以血氧飽和度預測是否發生AMS
Pulse oximetry for the prediction of acute mountain sickness: A systematic review
(這段是我寫的)以前查詢血氧濃度與AMS相關性. 印象中罹患AMS和沒有生病的兩組. 血氧濃度交叉涵蓋的範圍不小. 有些血氧接近正常人平均值的也可能發生AMS. 有些低於正常人平均值的沒有發生AMS. 我的想法. 這些研究都是在特定條件下得出的結論. 結果可能受到很多因素影響, 例如基因差異. 當時高海拔地區的天氣. 路線難度及消耗體能的差異. 不同研究使用的儀器是否標準化(能直接將數據做比較). 還有很多其他可能會影響結果的因素. 得到的都只是特定條件下的研究結果. 未必能適用於所有地方.
Pulse oximetry for the prediction of acute mountain sickness: A systematic review
(這段是我寫的)以前查詢血氧濃度與AMS相關性. 印象中罹患AMS和沒有生病的兩組. 血氧濃度交叉涵蓋的範圍不小. 有些血氧接近正常人平均值的也可能發生AMS. 有些低於正常人平均值的沒有發生AMS. 我的想法. 這些研究都是在特定條件下得出的結論. 結果可能受到很多因素影響, 例如基因差異. 當時高海拔地區的天氣. 路線難度及消耗體能的差異. 不同研究使用的儀器是否標準化(能直接將數據做比較). 還有很多其他可能會影響結果的因素. 得到的都只是特定條件下的研究結果. 未必能適用於所有地方.
在醫院實際使用夾手指的血氧機測定血氧飽和度時, 數值有時候會變動. 病患手指血流灌注是否正常. 夾的位置都會影響數據. 下面很多研究的血氧飽和度差異. 發生 AMS 與健康個體差異僅有
名詞翻譯
丹木斯=乙醯唑胺 acetazolamide
普拿疼=乙醯氨基酚(普拿疼是台灣比較為民眾熟知的止痛退燒商品)
重點整理
1. 海拔2400公尺至5300公尺處，進行中等強度日常運動（50公尺步行，目標心率150次/分）後的靜止血氧飽和度（R-SpO₂）和運動血氧飽和度（Ex-SpO₂）。可預測在海拔4300-5300公尺是否會發生AMS
2. 服用丹木斯可預防AMS，且可改善 SpO2(但並非 SpO2 低就需要吃丹木斯)
本系統性回顧旨在評估高海拔地區脈搏血氧飽和度作為AMS易感性和嚴重程度預測指標的相關文獻，以便及早識別易患AMS的個體，對其進行更恰當的管理，並減輕疾病對個人、團隊和當地資源的負擔
The purpose of this systematic review is to evaluate the literature related to the use of pulse oximetry at high altitude as a predictive factor for AMS susceptibility and severity, so that individuals likely to develop the condition can be identified early, managed more appropriately, and disease burden on individuals, teams and local resources reduced.
2.2納入標準
本研究納入了以下人體研究：在健康低地居民攀登至陸地高海拔地區期間，透過脈搏血氧飽和度儀採集週邊血氧飽和度SpO2數據，並評估週邊血氧飽和度與急性高山病（AMS）嚴重程度之間的關係。排除以下研究：（1）研究對象包括動物、不健康的人類（例如，已知存在心臟/代謝/呼吸系統疾病、吸煙者）或僅包括高海拔居民（居住在海拔 2000 米以上）； (2) 使用模擬海拔（例如，在環境艙中進行常壓/低壓低氧）；(3) 未報告急性反應 (AMS) 評估方法 (AMS)；僅透過動脈血液樣本測量血氧飽和度；(5) 僅評估慢性高山病；(6) 僅在單一海拔或最高海拔 ≤2100 公尺處進行測量；或 (7) 未評估、分析或報告 AMS 嚴重程度或發生率與任何預測關係的結果。完整的納入與排除標準列於附錄A。涉及藥物/順勢療法介入的研究也被考慮，但僅當對照組/安慰劑組的數據能夠與治療組的數據區分開來，且在分析 AMS 的任何關係/差異時仍然相關時才予以納入。
儘管存在這些差異，大多數研究都採取了一些措施來保證測量品質。除了允許生理穩定外，許多研究還概述了緩解策略，包括：讓參與者避風、戴手套並對結果不知情（Oliver 等，2012）；戴上連指手套（Karinen 等，2012）；在測量前數月內未前往海拔高於 2500 公尺的地區（即未適應高海拔）之前進行測量；測量在加熱帳篷內進行（Modesti 等，2011）。
3.2.6 SpO2 and relationship with/prediction of AMS
其中兩項研究觀察到，在高海拔地區發生急性高山病AMS的個體，其在低海拔地區血氧飽和度SpO2 低於後來保持健康的個體（Cobb et al., 2021 ; Karinen et al., 2010）。
在海拔4300公尺及海拔4300-5300公尺出現高海拔疾病的個體. 海拔3500公尺靜止及運動SpO2低於健康組
4300公尺發生AMS. 海拔3500公尺靜止SpO2 88% VS 92%, 運動 SpO2 80% vs 85%
4300-5300公尺, 海拔3500公尺靜止SpO2 82% VS 86%, 運動 SpO2 76% vs 79%
Cobb and colleagues made similar observations, with individuals who became sick at any point having lower resting and post-exercise SpO2 at 3500 m (88.5% vs. 89.6%, P = 0.02 and 82.2% vs. 83.8%, P = 0.027) 
Mandolesi and colleagues derived a cutoff for of 84% at 3647 m for predicting later development of severe AMS (defined by LLS of >5), which demonstrated 86.67% sensitivity, 82.25% specificity, with area under the receiver operating characteristic curve (AUROC) = 0.87, P < 0.0001.
3.2.7 其他與AMS預測相關的變數一些納入的研究揭示了其他生理參數與AMS後續發展之間的預測關係。例如，Karinen 及其同事（ 2012）的研究表明，心率變異性(heart rate variability)與AMS具有預測關係。
與其他研究相比，各項研究中對生理狀態的控制較為一致。
Control for physiological state was carried out with greater consistency across studies than SpO2 measurement techniques themselves. Authors often outlined procedures to ensure physiological stabilisation prior to resting measurements (e.g., 15 min of seated rest). However, there were inconsistencies in physiological state (rested vs. during exercise) and the duration of time spent at altitude prior to SpO2 measurements (arrival vs. morning after). These variables require adequate control to draw truly robust conclusions such as whether one was more informative than the other regarding prediction of AMS.
儘管研究結果積極，但其效用仍需進一步研究。SpO2單獨使用時，其預測能力被認為有限（Chen et al., 2012）。這很可能是由於存在大量重疊。SpO2常在組間（AMS組和非AMS組）觀察到。使用多元分析方法建立預測模型似乎增強了預測能力。SpO2（Cobb 等人，2021；Oliver等人，2012）。然而，遺憾的是，多元模型通常包含一些晦澀難懂且難以重複的變量，例如血細胞比容（Modesti等人，2011），這使得這些模型的外部驗證尤為困難。儘管如此，多元模型仍然有助於識別其他對急性高山症（AMS）具有預測價值的變量，特別是靜止心率和心率變異性。值得注意的是，並非所有與AMS相關的變數都能單獨預測AMS。這就引出了一個問題：這些生理參數是否可以與其他因素結合？SpO2旨在改進預測模型並創建臨床工具，以識別有急性高山症風險的登山者和健行者，或早期識別急性高山症。
Despite positive findings, the utility of SpO2 as a standalone predictor was described as limited (Chen et al., 2012). This is most likely due to the substantial overlap in SpO2 often observed between groups (AMS and non-AMS). The use of multivariate analysis methods for prediction models appeared to strengthen the predictive power of SpO2 (Cobb et al., 2021; Oliver et al., 2012). Unfortunately, however, multivariate models often included esoteric and difficult to replicate variables such as haematocrit (Modesti et al., 2011), which makes external validation of these models particularly challenging. Nevertheless, multivariate models helped identify other variables that had predictive utility for AMS, particularly that of resting heart rate and heart rate variability, although it is worth noting that not all of the variables identified as having relationships with AMS were found to be individual predictors of AMS. It raises the question as to whether such physiological parameters could be used in combination with SpO2 to improve predictive modelling and create clinical tools to identify climbers and trekkers at risk of developing AMS or early identification of AMS
最後，必須指出的是，評估AMS的方法各異（例如，LLS評分的臨界值不同，以及是否結合臨床因素）也會影響預測分析。本篇回顧納入的研究均在現行指引發布前開展，而現行指引並未包含LLS的睡眠成分（Roach等人，2018）。
Finally, it must be noted that the variable methods for assessing AMS (i.e., different LLS score cut-off, and used with and without clinical components) can also impact predictive analysis. Studies included in this review were conducted prior to publication of current guidelines, which omits the sleep component of the LLS (Roach et al., 2018).
4.1 未來方向
未來該領域的研究必須著重關注資料的品質和數量，理想情況下，應採用易於進行外部驗證和再驗證的變量，這是建模的核心原則。創建精確的機器學習工具是一個很有前景的選擇；然而，此類方法需要高品質且規模龐大的資料集，這在山區環境中可能很難取得。為了應對這些挑戰，未來的研究應致力於在多個野外研究中，使用高保真設備（例如，智慧型手機穿戴裝置）收集多種生理參數的數據，並保持符合現有建議的上升速度。同樣，未來的研究人員必須考慮多年來發表的不同LLS評分標準，並在進行任何跨研究的事後分析時將其納入考慮。將臨床評分添加到LLS總分中可能有助於提高預測準確性，並降低LLS的整體主觀性。
4.1 Future directions
Future research efforts in this area must focus on the quality and quantity of collected data, ideally with variables that enable easy external validation and re-validation, a core principle of modelling. The creation of accurate machine learning tools presents a promising option; however, such methods require high-quality datasets of substantial size, which can be challenging to obtain in the mountain environment. To combat these challenges, future studies should aim to collect data for multiple physiological parameters using high-fidelity devices (e.g., smartphone-enabled wearables) across multiple field studies with rates of ascent in line with existing recommendations. Similarly, future researchers must consider the different criteria for LLS published over the years, and must factor this in when conducting any post-hoc analyses across studies. The addition of the clinical score to the total sum LLS may improve predictions and limit the overall subjectivity of LLS.
4.2結論
總之，這項系統性回顧證實，兩者之間很可能存在預測關係。
鑑於脈搏血氧儀的普及程度，無論我們今天對AMS的立場如何，登山者仍會繼續使用它來預測AMS。因此，進行更多關於此主題的研究（包括特定脈搏血氧儀的準確性及其誤差範圍、統一的測量方法以及避免數據誤讀）以「完善」這門科學至關重要。
Pulse oximeters are easy to use, noninvasive tools for the assessment of individuals at high altitude. These instruments provide an estimate in percentage of arterial hemoglobin oxygen saturation, which is a function of arterial partial pressure of oxygen. The percentage denotes the hemoglobin binding sites that are occupied at any one time by oxygen. At sea level, healthy individuals will be on the flat portion of the oxyhemoglobin dissociation curve, but at high altitude as the partial pressure of oxygen decreases with ascent, individuals will be at the steep portion of the curve (a slippery slope by comparison) where saturation changes significantly with respect to small changes in the partial pressure.
Most trekking and expedition groups use pulse oximeters as a novelty item, and many groups carry an inexpensive, pocket pulse oximeter (some as little as US $30) to periodically check the oxygen saturation (Spo2) as they as ascend up the trail. Based on medical literature, the pulse oximetery, though not 100% accurate, is useful in predicting acute mountain sickness (AMS).
Many studies have attempted to see if there is a link between hypoxemia and the likelihood of developing AMS. Some of these studies have used a prospective design to determine if decreased oxygen saturation earlier in the trip have increased the likelihood of suffering from AMS (Roach et al., 1998; Tannheimer et al., 2002; Karinen et al., 2010; Chen et al., 2012; Wagner et al., 2012; Faulhaber et al., 2014). Except for two studies above (Chen et al. and Wagner et al.), all the other studies in these prospective observations found a link. For example, Karinen et al. (2010) studied 83 ascents during eight expeditions. They measured both resting Spo2 (R-Spo2) and exercise Spo2 (Ex-Spo2) after moderate daily exercise [50 m walking, target heart rate 150 bpm] at altitudes of 2400 to 5300 m during ascent. The Lake Louise Score (Roach, 1993) was used in the diagnosis of AMS. Ex-Spo2 was lower at all altitudes among those climbers suffering from AMS during the expeditions than among those climbers who did not get AMS at any altitude during the expeditions. Reduced R-Spo2 and Ex-Spo2 measured at altitudes of 3500 and 4300 m seem to predict impending AMS at altitudes of 4300 m and 5300 m.
Why were the studies by Chen et al. (2012) and Wagner et al. (2012) different from the rest? One explanation may lie in the methodology of these studies. Error ranges in various pulse oximeters may be different. Large error ranges may not be good enough when small differences are being looked for. Other reasons for the differing results may be test performance methods, and possibly differences in assessment of clinical significance.
There are no randomized controlled trials (RCTs) of hypoxemic individuals to determine if starting them on AMS prophylaxis after they are identified as having a low Spo2 prevents AMS later in the trip. But RCTs using acetazolamide vs. other drugs or placebo in the prevention of AMS in the Everest region have consistently shown that those participants on acetazolamide were not only significantly more protected from AMS, but also had significant increased changes in their Spo2 compared to the drug or placebo group from the baseline, even though the actual changes were small (Basnyat et al., 2003; Gertsch et al., 2004; Basnyat et al., 2011). This is not to advocate using pulse oximetry to determine who should take acetazolamide.
An important review (Burtscher et al., 2008) of exposure to simulated hypoxia with measurement of arterial oxygen saturation to determine AMS susceptibility has also been carried out. Sixteen studies were reviewed where Sao2 was measured 20 to 30 min after exposure to simulated hypoxia equivalent to 2300 to 4200 m. The saturation values correctly predicted AMS susceptibility >80% of cases. Recently another study (Faulhaber et al., 2014) revealed that the additional determination of breathing frequency to oxygen saturation reading after 30 min exposure to simulated hypoxia can improve success in AMS prediction. Yet another interesting study (Tannheimer et al., 2009) revealed that the time necessary to complete a running task at high altitude on Mont Blanc (4808 m) and the lowest oxygen saturation while performing this task was predictive of an individual's risk of developing altitude sickness with further ascent. Hence other easily measurable parameters (such as respiratory rate, exercise time) in addition to measurement of Spo2 at high altitude may help improve the accuracy of the Spo2 readings vis a vis prediction of AMS. A fascinating, comprehensive recent study (Richalet et al., 2012) of 1326 subjects revealed that oxygen desaturation equal to or greater than 22% at exercise in hypoxia before a sojourn to >4000 m was an independent risk factor for predisposing a person to severe altitude sickness. The study did not address predisposition to the more benign form of the disease (i.e., AMS) and the study also had a methodological flaw in that more than two-thirds of the subjects did not complete the study.
Indeed, there is no dearth of medical literature supporting the use of pulse oximetry to predict AMS at a higher altitude from a baseline reading. At least one possible pathophysiological rationale for the link between AMS and decreased Spo2 may be adequate ventilation. If hyperventilation is the cornerstone of acclimatization, AMS patients may have hypoventilation with resultant decreased Spo2 (Basnyat and Murdoch, 2003). Another pathophysiological mechanism may be subclinical pulmonary edema as shown by Ge and colleagues (1997) who measured pulmonary diffusion capacity for carbon monoxide (DLCO) in a group of 32 subjects at 2260 m and following ascent to 4700 m. In subjects without AMS, the DLCO increased at higher altitude while in AMS patients the DLCO did not increase significantly. However when Dehnert et al. (2010) tried to reproduce this finding in individuals sojourning up to 4559 m, they were unable to replicate these results.
Pulse oximeters are even being used to predict summit success(Tannheimer et al., 2002). But clearly there are potential pitfalls of pulse oximeter readings; for example, individual variations, cut- offs for altitudes, and large standard deviations of the Spo2 need to be taken into account (Luks and Swenson, 2011; Windsor, 2012; Zafren, 2012).
Given the popularity of pulse oximeters, mountain sojourners will continue to use them to try to predict AMS, regardless of where we stand on this issue today. It is therefore very important to do further studies on this topic (including accuracy of particular pulse oximeters and their error ranges, uniform measurement methods, and avoiding misinterpretation of data) to “refine” this science.
研究納入和排除條件. 研究方法, 統計分析方式這些請到原文裡面查詢. 這裡僅截錄部分內容. 另外. 複製張貼原文的時候. SpO2 是特殊符號無法直接拷貝貼上. 內容很多地方少了SpO2 這個字. 翻譯起來會很怪. 若覺得翻譯怪的地方. 請回原文尋找答案
這篇研究報告的附錄有整理出所收納的七篇研究的主要結果. Main outcomes from included studies. 可以直接看原文
名詞翻譯
丹木斯=乙醯唑胺 acetazolamide
普拿疼=乙醯氨基酚(普拿疼是台灣比較為民眾熟知的止痛退燒商品)
重點整理
1. 海拔2400公尺至5300公尺處，進行中等強度日常運動（50公尺步行，目標心率150次/分）後的靜止血氧飽和度（R-SpO₂）和運動血氧飽和度（Ex-SpO₂）。可預測在海拔4300-5300公尺是否會發生AMS
2. 服用丹木斯可預防AMS，且可改善 SpO2(但並非 SpO2 低就需要吃丹木斯)
3. 在高海拔發生AMS的個體. 在較低海拔(2610-3402-3500-3647)的SpO低於健康組 (研究中所謂高低是比較出來的. 例如 3500 相較於 4300 是較低海拔. 但兩處都已經是高海拔地區)
4. 海拔3647公尺測得 SpO2 < 84% 有可能會發生AMS (86.67% sensitivity, 82.25% specificity)
INTRODUCTION 這段不翻譯請看原文
Acute mountain sickness (AMS) is one of three major high-altitude (HA, >2500 m) illnesses (including HA cerebral and pulmonary oedema; HACE and HAPE) (Imray et al., 2011) and can afflict as many as 75% of people who ascend to HA (Croughs et al., 2014; Karinen et al., 2008). AMS has a much higher incidence and occurs at much lower altitudes than the more severe syndromes of HACE and HAPE. HA illnesses are caused by exposure to the reduced atmospheric pressure and reduced partial pressure of oxygen relative to sea level, which ultimately creates a hypoxic state in exposed individuals.
急性高山病AMS與高海拔腦水腫都是因腦水腫引起. 腦水腫是因為血腦障壁BBB的通透性上升造成. 其機轉目前並不明確, 但推測是多種原因引起(有人推測各種原因,但也僅是推測). 缺氧,二氧化碳過高,血管壓力上升,發炎反應都與血管反應相關, 細胞毒性反應也有關聯, 無論如何, 腦水腫導致典型症狀出現，頭痛，噁心想吐，頭暈，疲憊倦怠，在極高海拔這些水腫反應可能嚴重到引起中樞神經異常，即是高海拔腦水腫HACE
AMS and HACE are caused by cerebral oedema due to increased fluid permeability of the blood–brain barrier. The mechanism for how this occurs is unclear but is thought to be multifactorial. Hypoxia, hypercapnia, increased vascular pressures and inflammatory processes have all been linked as vasogenic causes, with other cytotoxic causes also identified (Lafuente et al., 2016). Nevertheless, the cerebral oedema results in the classical collection of symptoms including HA headache, nausea/vomiting, dizziness and fatigue (Luks et al., 2017), and at extreme altitudes these oedematous changes can become profound enough to cause acute central neurological deficits. This is considered the threshold for the diagnosis of HACE.
預防AMS和HACE最好的方法是足夠的高海拔生理適應, 藉由休息間隔, 放慢爬升速率, 減少每天爬升海拔(在海拔超過3000公尺,每天上升不要超過500公尺)使身體能完成高度適應. 但要達到足夠的高度適應非常耗時間. 很難做到上述建議, 因此藥物預防被廣泛的使用,
Acute mountain sickness (AMS) is one of three major high-altitude (HA, >2500 m) illnesses (including HA cerebral and pulmonary oedema; HACE and HAPE) (Imray et al., 2011) and can afflict as many as 75% of people who ascend to HA (Croughs et al., 2014; Karinen et al., 2008). AMS has a much higher incidence and occurs at much lower altitudes than the more severe syndromes of HACE and HAPE. HA illnesses are caused by exposure to the reduced atmospheric pressure and reduced partial pressure of oxygen relative to sea level, which ultimately creates a hypoxic state in exposed individuals.
急性高山病AMS與高海拔腦水腫都是因腦水腫引起. 腦水腫是因為血腦障壁BBB的通透性上升造成. 其機轉目前並不明確, 但推測是多種原因引起(有人推測各種原因,但也僅是推測). 缺氧,二氧化碳過高,血管壓力上升,發炎反應都與血管反應相關, 細胞毒性反應也有關聯, 無論如何, 腦水腫導致典型症狀出現，頭痛，噁心想吐，頭暈，疲憊倦怠，在極高海拔這些水腫反應可能嚴重到引起中樞神經異常，即是高海拔腦水腫HACE
AMS and HACE are caused by cerebral oedema due to increased fluid permeability of the blood–brain barrier. The mechanism for how this occurs is unclear but is thought to be multifactorial. Hypoxia, hypercapnia, increased vascular pressures and inflammatory processes have all been linked as vasogenic causes, with other cytotoxic causes also identified (Lafuente et al., 2016). Nevertheless, the cerebral oedema results in the classical collection of symptoms including HA headache, nausea/vomiting, dizziness and fatigue (Luks et al., 2017), and at extreme altitudes these oedematous changes can become profound enough to cause acute central neurological deficits. This is considered the threshold for the diagnosis of HACE.
預防AMS和HACE最好的方法是足夠的高海拔生理適應, 藉由休息間隔, 放慢爬升速率, 減少每天爬升海拔(在海拔超過3000公尺,每天上升不要超過500公尺)使身體能完成高度適應. 但要達到足夠的高度適應非常耗時間. 很難做到上述建議, 因此藥物預防被廣泛的使用,
這篇研究提到了參考oxford-handbook-of-expedition-and-wilderness-medicine 建議的上升速率. 這本書免費的PDF檔案可在網路搜尋到(第三版2023-08-24)
The gold standard for both AMS and HACE prophylaxis is adequate physiological acclimatisation to HA, which can be achieved through rest periods, and slow and partial ascents (<500 m gain in sleeping altitude per day above 3000 m) (Imray et al., 2015). However, adequate acclimatisation is time consuming, prompting poor adherence and the widespread use of pharmaceuticals to aid the process.
丹木斯是最常使用的藥物, 丹木斯是碳酸酐酶抑制劑, 會引起酸血症. 酸血症會刺激呼吸中樞,增加呼吸驅動力,可提高氧氣輸送, 可加速高度適應, 因此，乙醯唑胺也可用於治療，儘管急性高山病（AMS）和高海拔腦水腫（HACE）在嚴重情況下均可透過吸氧和立即下降進行治療。 AMS 也可使用對普拿疼和充足的口服補液進行治療，而 HACE 則需要使用強效皮質類固醇（如地塞米松）治療以減輕腦水腫，這凸顯了預防和密切監測的重要性（Joyce 等，2018 年）。
Most noteworthy of these prophylactic aids is acetazolamide, a carbonic anhydrase inhibitor that induces mild acidaemia, which stimulates increased respiratory drive, and thereby increases oxygen delivery, thus accelerating acclimatisation (Leaf & Goldfarb, 2007). As such, acetazolamide can also be used for treatment, notwithstanding that both AMS and HACE can be treated with oxygen and immediate descent in severe cases. AMS can also be treated with paracetamol and adequate oral hydration, whereas HACE requires treatment with potent corticosteroids such as dexamethasone to reduce cerebral oedema, thus emphasising the importance of prevention and close monitoring (Joyce et al., 2018).
目前，AMS 的診斷仍以臨床表現為主(不需抽血或以其他儀器檢測)，當症狀嚴重時，診斷較為明確。儘管如此，在早期階段，AMS 可能難以界定，沒有明顯的跡像或症狀。自我報告的路易斯湖評分（LLS）標準也可用於評估 AMS，該標準涉及對頭痛、胃腸道不適、疲勞和頭暈/眩暈等症狀進行主觀排序（Roach 等，2018 年）。儘管LLS能夠追蹤疾病症狀的發展進程，並可作為輔助診斷手段，但目前它並不具備預測價值（Moore等人，2020）。 LLS的主觀性和可靠性爭議凸顯了採用更客觀、理想情況下更具前瞻性的方法來提高急性高山病（AMS）診斷準確性的必要性，這將使臨床醫生能夠及時識別高危險群並進行預防性干預。
Currently, diagnosis of AMS remains clinical, and when symptoms are severe, the condition makes diagnosis obvious. Despite this, in its earlier stages AMS can be ill-defined without distinctive signs or symptoms. The self-report Lake Louise Score (LLS) criteria can also be used to evaluate AMS, and involves subjectively ranking symptoms, such as headache, gastrointestinal distress, fatigue and dizziness/light-headedness (Roach et al., 2018). While the LLS is able to track progression of the illness as symptoms develop, and can be used as a diagnostic aid, it currently offers no predictive value (Moore et al., 2020). The subjectivity and disputed reliability of the LLS have emphasised the need for assessing AMS with improved diagnostic accuracy utilising more objective and ideally prospective methodology, which would allow clinicians to identify individuals who are at risk in time for preventative intervention.
研究人員已對生理參數進行了研究，以確定它們是否能夠作為更客觀的AMS預測手段，並評估其嚴重程度和易感性。鑑於AMS是長期暴露於低壓低氧環境的結果，動脈血氧飽和度一直是與AMS一同研究的常用生理參數。雖然直接測量動脈血氧飽和度SaO2（AOO）需要專門的設備和技術，這在研究環境之外幾乎不可能實現，但透過脈搏血氧儀測量週邊血氧飽和度（PBOS）則更為便捷，也更適合在高海拔地區進行實地應用。然而，關於脈搏血氧飽和度SpO2在評估急性高山病（AMS）嚴重程度的應用，現有文獻尚無定論（Major et al., 2012 ; O'Connor et al., 2004），而其在AMS預測的應用研究則較為匱乏。
The gold standard for both AMS and HACE prophylaxis is adequate physiological acclimatisation to HA, which can be achieved through rest periods, and slow and partial ascents (<500 m gain in sleeping altitude per day above 3000 m) (Imray et al., 2015). However, adequate acclimatisation is time consuming, prompting poor adherence and the widespread use of pharmaceuticals to aid the process.
丹木斯是最常使用的藥物, 丹木斯是碳酸酐酶抑制劑, 會引起酸血症. 酸血症會刺激呼吸中樞,增加呼吸驅動力,可提高氧氣輸送, 可加速高度適應, 因此，乙醯唑胺也可用於治療，儘管急性高山病（AMS）和高海拔腦水腫（HACE）在嚴重情況下均可透過吸氧和立即下降進行治療。 AMS 也可使用對普拿疼和充足的口服補液進行治療，而 HACE 則需要使用強效皮質類固醇（如地塞米松）治療以減輕腦水腫，這凸顯了預防和密切監測的重要性（Joyce 等，2018 年）。
Most noteworthy of these prophylactic aids is acetazolamide, a carbonic anhydrase inhibitor that induces mild acidaemia, which stimulates increased respiratory drive, and thereby increases oxygen delivery, thus accelerating acclimatisation (Leaf & Goldfarb, 2007). As such, acetazolamide can also be used for treatment, notwithstanding that both AMS and HACE can be treated with oxygen and immediate descent in severe cases. AMS can also be treated with paracetamol and adequate oral hydration, whereas HACE requires treatment with potent corticosteroids such as dexamethasone to reduce cerebral oedema, thus emphasising the importance of prevention and close monitoring (Joyce et al., 2018).
目前，AMS 的診斷仍以臨床表現為主(不需抽血或以其他儀器檢測)，當症狀嚴重時，診斷較為明確。儘管如此，在早期階段，AMS 可能難以界定，沒有明顯的跡像或症狀。自我報告的路易斯湖評分（LLS）標準也可用於評估 AMS，該標準涉及對頭痛、胃腸道不適、疲勞和頭暈/眩暈等症狀進行主觀排序（Roach 等，2018 年）。儘管LLS能夠追蹤疾病症狀的發展進程，並可作為輔助診斷手段，但目前它並不具備預測價值（Moore等人，2020）。 LLS的主觀性和可靠性爭議凸顯了採用更客觀、理想情況下更具前瞻性的方法來提高急性高山病（AMS）診斷準確性的必要性，這將使臨床醫生能夠及時識別高危險群並進行預防性干預。
Currently, diagnosis of AMS remains clinical, and when symptoms are severe, the condition makes diagnosis obvious. Despite this, in its earlier stages AMS can be ill-defined without distinctive signs or symptoms. The self-report Lake Louise Score (LLS) criteria can also be used to evaluate AMS, and involves subjectively ranking symptoms, such as headache, gastrointestinal distress, fatigue and dizziness/light-headedness (Roach et al., 2018). While the LLS is able to track progression of the illness as symptoms develop, and can be used as a diagnostic aid, it currently offers no predictive value (Moore et al., 2020). The subjectivity and disputed reliability of the LLS have emphasised the need for assessing AMS with improved diagnostic accuracy utilising more objective and ideally prospective methodology, which would allow clinicians to identify individuals who are at risk in time for preventative intervention.
研究人員已對生理參數進行了研究，以確定它們是否能夠作為更客觀的AMS預測手段，並評估其嚴重程度和易感性。鑑於AMS是長期暴露於低壓低氧環境的結果，動脈血氧飽和度一直是與AMS一同研究的常用生理參數。雖然直接測量動脈血氧飽和度SaO2（AOO）需要專門的設備和技術，這在研究環境之外幾乎不可能實現，但透過脈搏血氧儀測量週邊血氧飽和度（PBOS）則更為便捷，也更適合在高海拔地區進行實地應用。然而，關於脈搏血氧飽和度SpO2在評估急性高山病（AMS）嚴重程度的應用，現有文獻尚無定論（Major et al., 2012 ; O'Connor et al., 2004），而其在AMS預測的應用研究則較為匱乏。
Physiological parameters have been investigated to ascertain whether they can be used to form a more objective means of predicting AMS in individuals, as well as assessing severity and susceptibility. Given that AMS is the product of exposure to prolonged hypobaric hypoxia, arterial oxygenation has been the reflexive physiological parameter to investigate alongside AMS. Whilst direct measurement of arterial oxygenation () requires specialised equipment and techniques that are prohibitively impractical outside of research settings, measurement of peripheral blood oxygen saturation () via pulse oximetry is more convenient, and more practical for use in the field at altitude. Nevertheless, the literature surrounding the utility of in evaluating AMS severity appears inconclusive (Major et al., 2012; O'Connor et al., 2004), and the utility of in AMS prediction even less thoroughly researched.
本系統性回顧旨在評估高海拔地區脈搏血氧飽和度作為AMS易感性和嚴重程度預測指標的相關文獻，以便及早識別易患AMS的個體，對其進行更恰當的管理，並減輕疾病對個人、團隊和當地資源的負擔
The purpose of this systematic review is to evaluate the literature related to the use of pulse oximetry at high altitude as a predictive factor for AMS susceptibility and severity, so that individuals likely to develop the condition can be identified early, managed more appropriately, and disease burden on individuals, teams and local resources reduced.
2.2納入標準
本研究納入了以下人體研究：在健康低地居民攀登至陸地高海拔地區期間，透過脈搏血氧飽和度儀採集週邊血氧飽和度SpO2數據，並評估週邊血氧飽和度與急性高山病（AMS）嚴重程度之間的關係。排除以下研究：（1）研究對象包括動物、不健康的人類（例如，已知存在心臟/代謝/呼吸系統疾病、吸煙者）或僅包括高海拔居民（居住在海拔 2000 米以上）； (2) 使用模擬海拔（例如，在環境艙中進行常壓/低壓低氧）；(3) 未報告急性反應 (AMS) 評估方法 (AMS)；僅透過動脈血液樣本測量血氧飽和度；(5) 僅評估慢性高山病；(6) 僅在單一海拔或最高海拔 ≤2100 公尺處進行測量；或 (7) 未評估、分析或報告 AMS 嚴重程度或發生率與任何預測關係的結果。完整的納入與排除標準列於附錄A。涉及藥物/順勢療法介入的研究也被考慮，但僅當對照組/安慰劑組的數據能夠與治療組的數據區分開來，且在分析 AMS 的任何關係/差異時仍然相關時才予以納入。
2.2 Eligibility criteria
Human studies involving the collection of peripheral blood oxygen saturation (, via pulse oximetry) from healthy lowlanders during ascent to terrestrial high altitude that evaluated the relationship between and AMS severity were considered for eligibility. Studies were excluded that: (1) included animals, unhealthy humans (e.g., known pre-existing cardiac/metabolic/respiratory condition(s), smokers), or only highlanders (living above 2000 m); (2) utilised simulated altitude (e.g., normobaric/hypobaric hypoxia in an environmental chamber); (3) failed to report the AMS assessment method (e.g., LLS or Environmental Screening Questionnaire, ESQ); (4) measured blood oxygen saturation only by arterial samples; (5) assessed only chronic mountain sickness; (6) measured only at a single altitude or a maximum altitude ≤2100 m, or (7) failed to evaluate, analyse or report results for any predictive relationship between AMS severity or occurrence and . Full inclusion and exclusion criteria are listed in Appendix A. Studies involving pharmacological/homeopathic intervention(s) were considered, albeit only included if control/placebo group data could be isolated from those of the treated group(s) and were still relevant in the context of any relationship/difference in AMS.
2.6資料項
所需資料項包括：樣本量；使用的血氧飽和度監測設備；測量海拔/位置、解剖部位（例如，手指、耳垂）、頻率/間隔（例如，每秒一次；每5分鐘一次）和持續時間（例如，90秒）、時間（即，前瞻性測量、到達高原期測量、AMS發作時測量）、一天中的時間（例如，夜間、早晨或運動後測量）、環境溫度、人體狀態（即，清醒或睡眠狀態）和身體姿勢（例如，仰臥、坐姿、站立）。其他需要收集資料的變數包括：參與者特徵（例如，男性/女性、年齡）、上升速度（是否符合現有指南）、主要交通方式（例如，飛機、健行或汽車）、使用的急性高山病評估方法（例如，LLS、ESQ 或 AMS-C）、急性高山病的盛行率或發病率、應用於原始血氧飽和度資料的任何處理技術以及統計分析程序。
Human studies involving the collection of peripheral blood oxygen saturation (, via pulse oximetry) from healthy lowlanders during ascent to terrestrial high altitude that evaluated the relationship between and AMS severity were considered for eligibility. Studies were excluded that: (1) included animals, unhealthy humans (e.g., known pre-existing cardiac/metabolic/respiratory condition(s), smokers), or only highlanders (living above 2000 m); (2) utilised simulated altitude (e.g., normobaric/hypobaric hypoxia in an environmental chamber); (3) failed to report the AMS assessment method (e.g., LLS or Environmental Screening Questionnaire, ESQ); (4) measured blood oxygen saturation only by arterial samples; (5) assessed only chronic mountain sickness; (6) measured only at a single altitude or a maximum altitude ≤2100 m, or (7) failed to evaluate, analyse or report results for any predictive relationship between AMS severity or occurrence and . Full inclusion and exclusion criteria are listed in Appendix A. Studies involving pharmacological/homeopathic intervention(s) were considered, albeit only included if control/placebo group data could be isolated from those of the treated group(s) and were still relevant in the context of any relationship/difference in AMS.
2.6資料項
所需資料項包括：樣本量；使用的血氧飽和度監測設備；測量海拔/位置、解剖部位（例如，手指、耳垂）、頻率/間隔（例如，每秒一次；每5分鐘一次）和持續時間（例如，90秒）、時間（即，前瞻性測量、到達高原期測量、AMS發作時測量）、一天中的時間（例如，夜間、早晨或運動後測量）、環境溫度、人體狀態（即，清醒或睡眠狀態）和身體姿勢（例如，仰臥、坐姿、站立）。其他需要收集資料的變數包括：參與者特徵（例如，男性/女性、年齡）、上升速度（是否符合現有指南）、主要交通方式（例如，飛機、健行或汽車）、使用的急性高山病評估方法（例如，LLS、ESQ 或 AMS-C）、急性高山病的盛行率或發病率、應用於原始血氧飽和度資料的任何處理技術以及統計分析程序。
上升速度的評估依據《牛津探險與野外醫學手冊》中的上升指南，該指南規定，海拔3000米以上時，每日上升高度不應超過500米，且每3-4天休息一天。牛津探險與野外醫學手冊2023年第三版可在網路找到PDF檔案
2.6 Data items
Data items sought included: sample size; oximetry device used; measurement altitude/location, anatomical site (e.g., finger, earlobe), frequency/interval (e.g., every second; every 5 min) and duration (e.g., 90 s), timing (i.e., prospective, on arrival to altitude, at onset of sickness), time of day (e.g., overnight, morning, or post-exercise), ambient temperature, human state (i.e., awake or asleep), and body position (e.g., supine, seated, standing). Additional variables for which data were sought included: participant characteristics (e.g., male/female, age), rate of ascent (in line with existing guidelines, yes/no), predominant mode of transport (e.g., flight, trekking, or by car), AMS assessment method used (e.g., LLS or ESQ or AMS-C), prevalence or incidence of AMS, any processing techniques applied to raw oximetry data, and statistical analysis procedures. (Rate of ascent was assessed using the ascent guideline from the Oxford Handbook of Expedition and Wilderness Medicine, which stipulates that above 3000 m, ascent should be no more than 500 m per day with a rest day every 3–4 days.)
3 RESULTS結果
Data items sought included: sample size; oximetry device used; measurement altitude/location, anatomical site (e.g., finger, earlobe), frequency/interval (e.g., every second; every 5 min) and duration (e.g., 90 s), timing (i.e., prospective, on arrival to altitude, at onset of sickness), time of day (e.g., overnight, morning, or post-exercise), ambient temperature, human state (i.e., awake or asleep), and body position (e.g., supine, seated, standing). Additional variables for which data were sought included: participant characteristics (e.g., male/female, age), rate of ascent (in line with existing guidelines, yes/no), predominant mode of transport (e.g., flight, trekking, or by car), AMS assessment method used (e.g., LLS or ESQ or AMS-C), prevalence or incidence of AMS, any processing techniques applied to raw oximetry data, and statistical analysis procedures. (Rate of ascent was assessed using the ascent guideline from the Oxford Handbook of Expedition and Wilderness Medicine, which stipulates that above 3000 m, ascent should be no more than 500 m per day with a rest day every 3–4 days.)
3 RESULTS結果
3.2.5 測量SpO2
大多數研究使用Nonin血氧儀在早晨進行指尖血氧飽和度測量（參見表2）。在納入的七項研究中，有五項研究在受試者靜坐休息時採集血氧飽和度數據，測量前受試者有最多15分鐘的休息時間以使生理狀態穩定（表3）。除了靜止狀態下的測量外，一些研究還考察了運動後（或運動過程中）的測量（Karinen 等，2010；Mandolesi 等，2014）。各研究的測量持續時間不一致，從連續測量到 1-2 分鐘不等（參見表2中的「測量持續時間」 ），而關於研究如何確定後續分析所用數值的細節則更加不一致，且往往不明確（參見表2中的「處理」 ）。
3.2.5 SpO2 measurements
大多數研究使用Nonin血氧儀在早晨進行指尖血氧飽和度測量（參見表2）。在納入的七項研究中，有五項研究在受試者靜坐休息時採集血氧飽和度數據，測量前受試者有最多15分鐘的休息時間以使生理狀態穩定（表3）。除了靜止狀態下的測量外，一些研究還考察了運動後（或運動過程中）的測量（Karinen 等，2010；Mandolesi 等，2014）。各研究的測量持續時間不一致，從連續測量到 1-2 分鐘不等（參見表2中的「測量持續時間」 ），而關於研究如何確定後續分析所用數值的細節則更加不一致，且往往不明確（參見表2中的「處理」 ）。
3.2.5 SpO2 measurements
Most studies measured SpO2 from the finger in the morning using Nonin oximeters (refer to Table 2). Five of the seven included studies collected oximetry measurements while participants were seated at rest, which was preceded by a period of rest (up to 15 min) to allow for physiological stabilisation (Table 3). In addition to resting SpO2 measurements, some studies also looked at post-exercise (or exercise)SpO2 (Karinen et al., 2010; Mandolesi et al., 2014). Measurement duration was inconsistent between studies, ranging from continuous to 1–2 min (refer to ‘Measurement duration’ in Table 2), with details surrounding how studies determined values to then be used in subsequent analysis being even less consistent, and often unclear (refer to ‘Processing’ in Table 2).
儘管存在這些差異，大多數研究都採取了一些措施來保證測量品質。除了允許生理穩定外，許多研究還概述了緩解策略，包括：讓參與者避風、戴手套並對結果不知情（Oliver 等，2012）；戴上連指手套（Karinen 等，2012）；在測量前數月內未前往海拔高於 2500 公尺的地區（即未適應高海拔）之前進行測量；測量在加熱帳篷內進行（Modesti 等，2011）。
Despite observed differences, most studies took some action(s) to protect the quality of the measurements. In addition to allowing for physiological stabilisation, many studies outlined mitigation strategies, which included: participants being sheltered from the wind, wearing gloves and blinded to their results (Oliver et al., 2012); hands covered with mittens (Karinen et al., 2012); no travel to altitudes >2500 m in months prior (i.e., unacclimatised) (Karinen et al., 2010); measurements performed prior to any caffeine consumption (Cobb et al., 2021); and measurements performed in a heated tent (Modesti et al., 2011).
3.2.6 SpO2 and relationship with/prediction of AMS
不同研究之間. 預測AMS的方法各有差異. 因此得到不同結果.
(... 以下這段省略中文翻譯)
3.2.6 SpO2 and relationship with/prediction of AMS
Methods used to evaluate the prediction of AMS by SpO2 varied substantially between studies (as outlined in Table 4), producing multiform results (Appendix D), and thus precluding the possibility of carrying out traditional quantitative meta-analysis. As a result, qualitative meta-analysis was carried out. Some studies evaluated SpO2 as a standalone factor by means of correlation analysis, receiver operator characteristic and logistic regression (Mandolesi et al., 2014; Modesti et al., 2011), while other studies included SpO2 as part of multivariate prediction models (refer to Table 4). Studies often included multiple analyses.
3.2.6 SpO2 and relationship with/prediction of AMS
Methods used to evaluate the prediction of AMS by SpO2 varied substantially between studies (as outlined in Table 4), producing multiform results (Appendix D), and thus precluding the possibility of carrying out traditional quantitative meta-analysis. As a result, qualitative meta-analysis was carried out. Some studies evaluated SpO2 as a standalone factor by means of correlation analysis, receiver operator characteristic and logistic regression (Mandolesi et al., 2014; Modesti et al., 2011), while other studies included SpO2 as part of multivariate prediction models (refer to Table 4). Studies often included multiple analyses.
其中兩項研究觀察到，在高海拔地區發生急性高山病AMS的個體，其在低海拔地區血氧飽和度SpO2 低於後來保持健康的個體（Cobb et al., 2021 ; Karinen et al., 2010）。
Two of the included studies observed that individuals who subsequently developed AMS at higher altitudes had a lower SpO2 at lower altitudes than their counterparts who later remained healthy (Cobb et al., 2021; Karinen et al., 2010).
在海拔4300公尺及海拔4300-5300公尺出現高海拔疾病的個體. 海拔3500公尺靜止及運動SpO2低於健康組
4300公尺發生AMS. 海拔3500公尺靜止SpO2 88% VS 92%, 運動 SpO2 80% vs 85%
4300-5300公尺, 海拔3500公尺靜止SpO2 82% VS 86%, 運動 SpO2 76% vs 79%
Specifically, Karinen et al. (2010) observed this in both resting and exercise SpO2 in individuals at 3500 m who later became sick at 4300 m (88 ± 2% vs. 91 ± 3% , P < 0.05 and 80 ± 2% vs. 85 ± 4%, P < 0.01, respectively), and between 4300 m and 5300 m (82 ± 4% vs. 86 ± 5%, P < 0.01, 76 ± 4% vs. 79 ± 5%, P < 0.01).
Similarly, Mandolesi and colleagues observed that individuals who become sick with either mild or moderate-to-severe AMS were always more hypoxaemic at rest at altitudes as low as 3275 m (87.7 ± 3.5% vs. 86 ± 4.1% vs. 85.4% ± 4, P = 0.037, P = 0.030).
不同海拔休息時的血氧濃度(2610公尺.3402公尺)與發生AMS相關
Further, Chen and colleagues observed the same relationship in resting SpO2 at every observation point in their study, even at 2610 m (93.1 ± 2.1% vs. 93.5 ± 2.3%; P = 0.023), and at 3402 m before and after summiting at 3952 m (86.2 ± 4.7% vs. 87.6 ± 4.3%; P < 0.001 and 85.5 ± 3.5% vs. 89.6 ± 3.2%; P < 0.001)
海拔2400公尺的血氧飽和度與AMS沒有顯著關聯. 但海拔3000-4300公尺運動後血氧飽和度較低的個體在海拔5000公尺以上出現症狀.
Notably, Karinen and colleagues (2012) did not observe a significant relationship between resting SpO2 at 2400 m, but found exercise SpO2 to be lower at between 3000 and 4300 m in individuals who became sick above 5000 m (P < 0.05). (Specific data not provided by authors.)
Mandolesi及其同事推導出了一個臨界值
Mandolesi and colleagues derived a cutoff for of 84% at 3647 m for predicting later development of severe AMS (defined by LLS of >5), which demonstrated 86.67% sensitivity, 82.25% specificity, with area under the receiver operating characteristic curve (AUROC) = 0.87, P < 0.0001.
當分析範圍限制在LLS評分≥6的嚴重AMS時，他們觀察到敏感性提高至90%，AUROC為0.91（P< 0.0001）。這個數值(84%)明顯低於Modesti及其同事得出的4200公尺SpO2臨界值91.5% (僅繪製了靈敏度和特異性曲線，未提供具體數值）。
When restricting analyses to severe AMS defined by LLS ≥ 6, they observed that the sensitivity improved to 90% and the AUROC was 0.91 (P < 0.0001).
These cutoffs were noticeably lower than the 91.5% cutoff derived by Modesti and colleagues at 4200 m (sensitivity and specificity only plotted, no values provided).
相較之下，Cobb及其同事並未發現靜止狀態下的
By contrast, Cobb and colleagues did not identify resting measured at 3500 m to be a standalone predictor (by univariate regression) of severe AMS (LLS ≥ 5) during the trek; however, it was included in the subsequent multivariate regression model based on its significance (i.e., variables with P < 0.15 considered for inclusion in the multiple logistic regression model; odds ratio (OR) = 0.963 (95% CI: 0.880–1.055)). Nevertheless, Cobb and colleagues did show post-exercise to be a significant standalone predictor of severe AMS (OR = 0.870 (95% CI: 0.803–0.943)); however, the AUROC for individual variables was not evaluated.
3.2.7 其他與AMS預測相關的變數一些納入的研究揭示了其他生理參數與AMS後續發展之間的預測關係。例如，Karinen 及其同事（ 2012）的研究表明，心率變異性(heart rate variability)與AMS具有預測關係。
3.2.7 Other variables linked to AMS prediction
Some included studies revealed predictive relationships between other physiological parameters and subsequent development of AMS. For example, heart rate variability was shown to have a predictive relationship with AMS by Karinen and colleagues (2012).
Some included studies revealed predictive relationships between other physiological parameters and subsequent development of AMS. For example, heart rate variability was shown to have a predictive relationship with AMS by Karinen and colleagues (2012).
Mandolesi及其同事發現，靜止心率和在海拔3647公尺處過夜的心率與AMS之間有顯著相關性。同樣，Oliver及其同事也發現心率與AMS症狀評分呈正相關。相較之下，Karinen及其同事（2010）並未觀察到海拔3500公尺和4300公尺處的靜止心率與分別在海拔4300公尺和5300公尺處即將發生的AMS之間存在任何相關性。
(海拔3500-4300公尺測得的心跳與之後在4300-5300公尺是否發生AMS無關)
Mandolesi and colleagues noted a significant relationship between heart rate (at rest and overnight at 3647 m) and AMS. Similarly, Oliver and colleagues showed a positive correlation between heart rate and AMS symptom score. By contrast, Karinen and colleagues (2010) did not observe any relationship between resting heart rate at 3500 m and 4300 m and impending AMS at 4300 and 5300 m, respectively.
Modesti及其同事也發現，年齡、性別、體重指數、血壓和呼吸頻率等其他因素與AMS（根據LLS定義）獨立相關。同樣，Modesti及其同事也發現，探險日期和氣壓等環境因素，以及凝血動力學、血球比容、肺動脈壓和兒茶酚胺血漿濃度等更複雜的因素，也是LLS在多變量模型中的獨立預測因子。
Modesti and colleagues identified several other factors such as age, sex, body mass index, blood pressure and respiratory rate that were independently associated with AMS (as defined by LLS). Similarly, Modesti and colleagues identified environmental factors including day of expedition and barometric pressure, as well as more complex factors such as coagulation dynamics, haematocrit, pulmonary artery pressure and catecholamine plasma concentration, which were also independent predictors of LLS within multivariate models.
Modesti及其同事也發現，年齡、性別、體重指數、血壓和呼吸頻率等其他因素與AMS（根據LLS定義）獨立相關。同樣，Modesti及其同事也發現，探險日期和氣壓等環境因素，以及凝血動力學、血球比容、肺動脈壓和兒茶酚胺血漿濃度等更複雜的因素，也是LLS在多變量模型中的獨立預測因子。
Modesti and colleagues identified several other factors such as age, sex, body mass index, blood pressure and respiratory rate that were independently associated with AMS (as defined by LLS). Similarly, Modesti and colleagues identified environmental factors including day of expedition and barometric pressure, as well as more complex factors such as coagulation dynamics, haematocrit, pulmonary artery pressure and catecholamine plasma concentration, which were also independent predictors of LLS within multivariate models.
3.2.8 高原藥物(預防性服用藥物的群體不納入統計)
本研究排除了納入服用增強高原適應藥物的受試者的研究。雖然可能存在部分受試者未申報服用乙醯唑胺等高原藥物，或服用處方藥導致數據出現反向混淆的情況，但考慮到納入研究的受試者總數，預計此類零星用藥的頻率不會對整體研究結果造成混淆。
3.2.8 Altitude drugs
Studies that included participants taking medications that enhance acclimatisation were excluded from this study. While it is possible some individuals did not declare use of altitude drugs such as acetazolamide, or were taking prescription medication that invertedly confounded the data, it is not anticipated that any such sporadic drug use occurred at a frequency that would confound the overall study findings, given the total number of individuals included.
4 討論
我們的系統性回顧表明，多項研究已證實靜止狀態降低與預測風險之間存在正面關係。
4 DISCUSSION
Our systematic review demonstrates that multiple studies have positively identified a predictive relationship between decreased resting SpO2 measured around 3500 to 4000 m and the risk of developing AMS at higher camps. A similar trend between exercising SpO2 measurements and AMS was also described by authors of several included studies (Cobb et al., 2021; Karinen et al., 2010, 2012; Mandolesi et al., 2014). There is, however, considerable nuance in the literature surrounding altitude profiles, methodologies, cohorts and measurement techniques, which limited our ability to draw definitive conclusions, as discussed below. This also prevented traditional meta-analytical techniques being carried out, and required a qualitative review of the evidence. Whilst this may have introduced an element of bias, findings consistent under the scrutiny of different methodological strategies adds an element of robustness to the findings.
未能證明
Ascents that failed to demonstrate SpO2 to be a significant predictive factor for AMS exhibited rates of ascent outside existing recommendations (refer to Figure 2c) (Modesti et al., 2011). This suggests that the predictive relationship may be dependent on rate of ascent. Similarly, the predictive relationship between SpO2 and AMS observed in this review (up to 6300 m) may only be relevant up to a threshold point, due to extreme altitude (>5500 m) ascent profiles necessitating extended acclimatisation and partial ascents over extended periods. Unfortunately, none of the predictive models examined in this review adequately addressed ascent profile, which is widely regarded as being one of the most significant risk factors for developing AMS. Thus, caution must be exercised when extrapolating the present findings to such extreme altitudes, or for ascents that go against current recommendations.
存在大量不一致之處SpO2
There were substantial inconsistencies in SpO2 measurement protocols, which posed an important limiting factor. Measurements are susceptible to many confounding factors at altitude including increased UV index and brightness, ambient temperature, and peripheral vasoconstriction due to cold (Luks & Swenson, 2011). Methods for optimising the measurement ofSpO2 at high altitude do exist (Tannheimer & Lechner, 2019), but these recommendations were not available at the time of publication for six out of the seven included studies. Nevertheless, authors regularly cited strategies used to protect measurement reliability (e.g., sheltering participants from wind and light or having participants wear gloves to warm their fingers) suggesting that authors were aware of the variety of factors that have the potential to influence SpO2 readings. Together, this strengthened the findings related to the predictive relationship between SpO2 and AMS.
本研究排除了納入服用增強高原適應藥物的受試者的研究。雖然可能存在部分受試者未申報服用乙醯唑胺等高原藥物，或服用處方藥導致數據出現反向混淆的情況，但考慮到納入研究的受試者總數，預計此類零星用藥的頻率不會對整體研究結果造成混淆。
3.2.8 Altitude drugs
Studies that included participants taking medications that enhance acclimatisation were excluded from this study. While it is possible some individuals did not declare use of altitude drugs such as acetazolamide, or were taking prescription medication that invertedly confounded the data, it is not anticipated that any such sporadic drug use occurred at a frequency that would confound the overall study findings, given the total number of individuals included.
4 討論
我們的系統性回顧表明，多項研究已證實靜止狀態降低與預測風險之間存在正面關係。
4 DISCUSSION
Our systematic review demonstrates that multiple studies have positively identified a predictive relationship between decreased resting SpO2 measured around 3500 to 4000 m and the risk of developing AMS at higher camps. A similar trend between exercising SpO2 measurements and AMS was also described by authors of several included studies (Cobb et al., 2021; Karinen et al., 2010, 2012; Mandolesi et al., 2014). There is, however, considerable nuance in the literature surrounding altitude profiles, methodologies, cohorts and measurement techniques, which limited our ability to draw definitive conclusions, as discussed below. This also prevented traditional meta-analytical techniques being carried out, and required a qualitative review of the evidence. Whilst this may have introduced an element of bias, findings consistent under the scrutiny of different methodological strategies adds an element of robustness to the findings.
未能證明
Ascents that failed to demonstrate SpO2 to be a significant predictive factor for AMS exhibited rates of ascent outside existing recommendations (refer to Figure 2c) (Modesti et al., 2011). This suggests that the predictive relationship may be dependent on rate of ascent. Similarly, the predictive relationship between SpO2 and AMS observed in this review (up to 6300 m) may only be relevant up to a threshold point, due to extreme altitude (>5500 m) ascent profiles necessitating extended acclimatisation and partial ascents over extended periods. Unfortunately, none of the predictive models examined in this review adequately addressed ascent profile, which is widely regarded as being one of the most significant risk factors for developing AMS. Thus, caution must be exercised when extrapolating the present findings to such extreme altitudes, or for ascents that go against current recommendations.
存在大量不一致之處SpO2
There were substantial inconsistencies in SpO2 measurement protocols, which posed an important limiting factor. Measurements are susceptible to many confounding factors at altitude including increased UV index and brightness, ambient temperature, and peripheral vasoconstriction due to cold (Luks & Swenson, 2011). Methods for optimising the measurement ofSpO2 at high altitude do exist (Tannheimer & Lechner, 2019), but these recommendations were not available at the time of publication for six out of the seven included studies. Nevertheless, authors regularly cited strategies used to protect measurement reliability (e.g., sheltering participants from wind and light or having participants wear gloves to warm their fingers) suggesting that authors were aware of the variety of factors that have the potential to influence SpO2 readings. Together, this strengthened the findings related to the predictive relationship between SpO2 and AMS.
與其他研究相比，各項研究中對生理狀態的控制較為一致。
Control for physiological state was carried out with greater consistency across studies than SpO2 measurement techniques themselves. Authors often outlined procedures to ensure physiological stabilisation prior to resting measurements (e.g., 15 min of seated rest). However, there were inconsistencies in physiological state (rested vs. during exercise) and the duration of time spent at altitude prior to SpO2 measurements (arrival vs. morning after). These variables require adequate control to draw truly robust conclusions such as whether one was more informative than the other regarding prediction of AMS.
儘管研究結果積極，但其效用仍需進一步研究。SpO2單獨使用時，其預測能力被認為有限（Chen et al., 2012）。這很可能是由於存在大量重疊。SpO2常在組間（AMS組和非AMS組）觀察到。使用多元分析方法建立預測模型似乎增強了預測能力。SpO2（Cobb 等人，2021；Oliver等人，2012）。然而，遺憾的是，多元模型通常包含一些晦澀難懂且難以重複的變量，例如血細胞比容（Modesti等人，2011），這使得這些模型的外部驗證尤為困難。儘管如此，多元模型仍然有助於識別其他對急性高山症（AMS）具有預測價值的變量，特別是靜止心率和心率變異性。值得注意的是，並非所有與AMS相關的變數都能單獨預測AMS。這就引出了一個問題：這些生理參數是否可以與其他因素結合？SpO2旨在改進預測模型並創建臨床工具，以識別有急性高山症風險的登山者和健行者，或早期識別急性高山症。
Despite positive findings, the utility of SpO2 as a standalone predictor was described as limited (Chen et al., 2012). This is most likely due to the substantial overlap in SpO2 often observed between groups (AMS and non-AMS). The use of multivariate analysis methods for prediction models appeared to strengthen the predictive power of SpO2 (Cobb et al., 2021; Oliver et al., 2012). Unfortunately, however, multivariate models often included esoteric and difficult to replicate variables such as haematocrit (Modesti et al., 2011), which makes external validation of these models particularly challenging. Nevertheless, multivariate models helped identify other variables that had predictive utility for AMS, particularly that of resting heart rate and heart rate variability, although it is worth noting that not all of the variables identified as having relationships with AMS were found to be individual predictors of AMS. It raises the question as to whether such physiological parameters could be used in combination with SpO2 to improve predictive modelling and create clinical tools to identify climbers and trekkers at risk of developing AMS or early identification of AMS
最後，必須指出的是，評估AMS的方法各異（例如，LLS評分的臨界值不同，以及是否結合臨床因素）也會影響預測分析。本篇回顧納入的研究均在現行指引發布前開展，而現行指引並未包含LLS的睡眠成分（Roach等人，2018）。
Finally, it must be noted that the variable methods for assessing AMS (i.e., different LLS score cut-off, and used with and without clinical components) can also impact predictive analysis. Studies included in this review were conducted prior to publication of current guidelines, which omits the sleep component of the LLS (Roach et al., 2018).
4.1 未來方向
未來該領域的研究必須著重關注資料的品質和數量，理想情況下，應採用易於進行外部驗證和再驗證的變量，這是建模的核心原則。創建精確的機器學習工具是一個很有前景的選擇；然而，此類方法需要高品質且規模龐大的資料集，這在山區環境中可能很難取得。為了應對這些挑戰，未來的研究應致力於在多個野外研究中，使用高保真設備（例如，智慧型手機穿戴裝置）收集多種生理參數的數據，並保持符合現有建議的上升速度。同樣，未來的研究人員必須考慮多年來發表的不同LLS評分標準，並在進行任何跨研究的事後分析時將其納入考慮。將臨床評分添加到LLS總分中可能有助於提高預測準確性，並降低LLS的整體主觀性。
4.1 Future directions
Future research efforts in this area must focus on the quality and quantity of collected data, ideally with variables that enable easy external validation and re-validation, a core principle of modelling. The creation of accurate machine learning tools presents a promising option; however, such methods require high-quality datasets of substantial size, which can be challenging to obtain in the mountain environment. To combat these challenges, future studies should aim to collect data for multiple physiological parameters using high-fidelity devices (e.g., smartphone-enabled wearables) across multiple field studies with rates of ascent in line with existing recommendations. Similarly, future researchers must consider the different criteria for LLS published over the years, and must factor this in when conducting any post-hoc analyses across studies. The addition of the clinical score to the total sum LLS may improve predictions and limit the overall subjectivity of LLS.
4.2結論
總之，這項系統性回顧證實，兩者之間很可能存在預測關係。
4.2 Conclusions
In conclusion, this systematic review establishes that there is most likely a predictive relationship between and AMS. It also highlights that this effect is not profound enough to be of clinical use in isolation. Reviews of existing research, post-hoc analysis of existing data sets, or the collection of new data could be used to identify other physiological parameters that also share a predictive relationship with AMS.
Pro: Pulse Oximetry Is Useful in Predicting Acute Mountain Sickness
(下面中文使用google翻譯)
脈搏血氧儀是一種易於使用、非侵入性的工具，可用於評估高海拔地區人口的健康狀況。這些儀器提供動脈血氧飽和度的百分比估計值，這是動脈血氧分壓的函數。此百分比表示在任何時刻被氧氣佔據的血紅蛋白結合位點。在海平面，健康個體處於氧合血紅蛋白解離曲線的平坦部分；但在高海拔地區，隨著海拔升高，氧分壓降低，個體則處於曲線的陡峭部分（相比之下，這是一個「滑坡」），此時氧飽和度會隨著氧分壓的微小變化而發生顯著變化。
大多數健行和探險隊將脈搏血氧儀視為一種新奇物品，許多隊伍會攜帶價格低廉的袖珍脈搏血氧儀（有些僅售30美元），以便在登山過程中定期檢查血氧飽和度（SpO₂ ）。根據醫學文獻，脈搏血氧儀雖然並非百分之百準確，但對於預測AMS仍然很有用。
許多研究試圖探討低氧血症與AMS發生風險之間是否存在關聯。其中一些研究採用前瞻性設計，旨在確定行程早期氧飽和度下降是否會增加患有AMS的風險（Roach et al., 1998 ; Tannheimer et al., 2002 ; Karinen et al., 2010 ; Chen et al., 2012 ; Wagner et al., 2012 ; Chen et al., 2012 ; Wagner et al., 2012 ; Chen et al., 2012 ; Wagner et al., 2012 ;除上述兩項研究（Chen et al.和Wagner et al.）外，其他所有前瞻性觀察研究均發現二者有關聯。例如，Karinen et al.（2010）研究了八次探險中的83次攀登。在登山過程中，研究人員測量了海拔2400公尺至5300公尺處，受試者在進行中等強度日常運動（50公尺步行，目標心率150次/分）後的靜止血氧飽和度（R-SpO₂）和運動血氧飽和度（Ex-SpO₂）。他們採用路易斯湖評分（Roach ，1993 ）診斷AMS）。在探險過程中，所有海拔高度下，發生AMS的登山者的Ex-SpO₂均低於未 發生AMS的登山者。在海拔3500公尺和4300公尺處測得的R-SpO₂和Ex-SpO₂降低似乎 可以預測 在海拔4300公尺和5300公尺處即將發生AMS。
Chen等人（ 2012）和Wagner等人（2012 ）的研究為何與其他研究有所不同？一種解釋可能在於這些研究的方法。不同脈搏血氧儀的誤差範圍可能有差異。當需要檢測微小差異時，較大的誤差範圍可能不夠理想。其他導致結果差異的原因可能包括測試方法不同，以及對臨床意義的評估標準不同。
目前尚無針對低氧血症患者的隨機對照試驗（RCT）來確定，在發現患者血氧飽和度（SpO2）較低後立即給予AMS預防藥物，是否能預防 後續行程中的AMS。但先前在珠穆朗瑪峰地區進行的RCT，以乙醯唑胺與其他藥物或安慰劑相比，在預防AMS方面取得了顯著療效。這些研究一致表明，服用乙醯唑胺的受試者不僅能更有效地預防AMS，而且與藥物組或安慰劑組相比，其SpO2較基線水平也有顯著改善，儘管 實際改善幅度較小（Basnyat et al., 2003 ; Gertsch et al., 2004 ; Basnyat et al., 2011）。但這並不意味著建議使用脈搏血氧飽和度來決定哪些人應該服用乙醯唑胺。
一項重要的綜述（Burtscher等人， 2008）探討了透過測量動脈血氧飽和度來評估模擬低氧暴露對AMS易感性的影響。該綜述回顧了16項研究，這些研究在受試者 暴露於相當於海拔2300至4200米的模擬低氧環境20至30分鐘後測量了動脈血氧飽和度（SaO₂ ） 。結果顯示，這些飽和度值能夠正確預測超過80%的AMS易感性病例。近期另一項研究（Faulhaber等人， 2014 年）表明，在模擬低氧暴露30分鐘後，除了測量血氧飽和度外，額外測定呼吸頻率可以提高AMS預測的準確性。此外，還有一項有趣的研究（Tannheimer等人， 2009 年）發現，在白朗峰（海拔4808公尺）完成跑步任務所需的時間以及完成該任務時的最低血氧飽和度可以預測個體在進一步攀登過程中發生AMS的風險。因此，除了在高海拔地區測量血氧飽和度（ SpO2 ）外，其他易於測量的參數（例如呼吸頻率、運動時間）可能有助於提高SpO2 讀數在預測AMS方面的準確性。一項近期開展的、引人入勝且全面的研究（Richalet等人， 2012）納入了1326名受試者，結果表明，在前往海拔4000米以上地區之前，低氧環境下運動時氧飽和度下降22%或以上是導致嚴重高原反應的獨立危險因素。該研究並未探討對較輕微的AMS的易感性，且該研究存在方法學缺陷，即超過三分之二的受試者未能完成研究。
事實上，有大量醫學文獻支持使用脈搏血氧飽和度監測儀，根據基線讀數預測AMS。 AMS與SpO₂降低之間聯繫的至少一個可能的病理生理學解釋是通氣不足。如果過度通氣是適應高原環境的基石，那麼AMS患者可能出現通氣不足，從而導致SpO₂降低（ Basnyat和Murdoch， 2003）。另一個病理生理機制可能是亞臨床肺水腫(很輕微尚未出現症狀的肺水腫)，正如Ge及其同事（1997）所展示的那樣，他們測量了32名受試者在海拔2260米處以及上升至4700米後的肺一氧化碳彌散量（DLCO）。在非AMS受試者中，DLCO隨海拔升高而增加，而在AMS患者中，DLCO並未顯著增加。然而，當Dehnert等人… （2010 年）試圖在海拔高達 4559 公尺的個體中重現這一發現，但他們未能重現這些結果。
脈搏血氧儀甚至被用於預測登頂成功率（Tannheimer等人， 2002）。但顯然，脈搏血氧儀讀數存在潛在的缺陷；例如，需要考慮個體差異、海拔高度的閾值以及SpO2的較大標準偏差（ Luks和Swenson， 2011 ； Windsor， 2012；Zafren， 2012）。
In conclusion, this systematic review establishes that there is most likely a predictive relationship between and AMS. It also highlights that this effect is not profound enough to be of clinical use in isolation. Reviews of existing research, post-hoc analysis of existing data sets, or the collection of new data could be used to identify other physiological parameters that also share a predictive relationship with AMS.
Pro: Pulse Oximetry Is Useful in Predicting Acute Mountain Sickness
(下面中文使用google翻譯)
脈搏血氧儀是一種易於使用、非侵入性的工具，可用於評估高海拔地區人口的健康狀況。這些儀器提供動脈血氧飽和度的百分比估計值，這是動脈血氧分壓的函數。此百分比表示在任何時刻被氧氣佔據的血紅蛋白結合位點。在海平面，健康個體處於氧合血紅蛋白解離曲線的平坦部分；但在高海拔地區，隨著海拔升高，氧分壓降低，個體則處於曲線的陡峭部分（相比之下，這是一個「滑坡」），此時氧飽和度會隨著氧分壓的微小變化而發生顯著變化。
大多數健行和探險隊將脈搏血氧儀視為一種新奇物品，許多隊伍會攜帶價格低廉的袖珍脈搏血氧儀（有些僅售30美元），以便在登山過程中定期檢查血氧飽和度（SpO₂ ）。根據醫學文獻，脈搏血氧儀雖然並非百分之百準確，但對於預測AMS仍然很有用。
許多研究試圖探討低氧血症與AMS發生風險之間是否存在關聯。其中一些研究採用前瞻性設計，旨在確定行程早期氧飽和度下降是否會增加患有AMS的風險（Roach et al., 1998 ; Tannheimer et al., 2002 ; Karinen et al., 2010 ; Chen et al., 2012 ; Wagner et al., 2012 ; Chen et al., 2012 ; Wagner et al., 2012 ; Chen et al., 2012 ; Wagner et al., 2012 ;除上述兩項研究（Chen et al.和Wagner et al.）外，其他所有前瞻性觀察研究均發現二者有關聯。例如，Karinen et al.（2010）研究了八次探險中的83次攀登。在登山過程中，研究人員測量了海拔2400公尺至5300公尺處，受試者在進行中等強度日常運動（50公尺步行，目標心率150次/分）後的靜止血氧飽和度（R-SpO₂）和運動血氧飽和度（Ex-SpO₂）。他們採用路易斯湖評分（Roach ，1993 ）診斷AMS）。在探險過程中，所有海拔高度下，發生AMS的登山者的Ex-SpO₂均低於未 發生AMS的登山者。在海拔3500公尺和4300公尺處測得的R-SpO₂和Ex-SpO₂降低似乎 可以預測 在海拔4300公尺和5300公尺處即將發生AMS。
Chen等人（ 2012）和Wagner等人（2012 ）的研究為何與其他研究有所不同？一種解釋可能在於這些研究的方法。不同脈搏血氧儀的誤差範圍可能有差異。當需要檢測微小差異時，較大的誤差範圍可能不夠理想。其他導致結果差異的原因可能包括測試方法不同，以及對臨床意義的評估標準不同。
目前尚無針對低氧血症患者的隨機對照試驗（RCT）來確定，在發現患者血氧飽和度（SpO2）較低後立即給予AMS預防藥物，是否能預防 後續行程中的AMS。但先前在珠穆朗瑪峰地區進行的RCT，以乙醯唑胺與其他藥物或安慰劑相比，在預防AMS方面取得了顯著療效。這些研究一致表明，服用乙醯唑胺的受試者不僅能更有效地預防AMS，而且與藥物組或安慰劑組相比，其SpO2較基線水平也有顯著改善，儘管 實際改善幅度較小（Basnyat et al., 2003 ; Gertsch et al., 2004 ; Basnyat et al., 2011）。但這並不意味著建議使用脈搏血氧飽和度來決定哪些人應該服用乙醯唑胺。
一項重要的綜述（Burtscher等人， 2008）探討了透過測量動脈血氧飽和度來評估模擬低氧暴露對AMS易感性的影響。該綜述回顧了16項研究，這些研究在受試者 暴露於相當於海拔2300至4200米的模擬低氧環境20至30分鐘後測量了動脈血氧飽和度（SaO₂ ） 。結果顯示，這些飽和度值能夠正確預測超過80%的AMS易感性病例。近期另一項研究（Faulhaber等人， 2014 年）表明，在模擬低氧暴露30分鐘後，除了測量血氧飽和度外，額外測定呼吸頻率可以提高AMS預測的準確性。此外，還有一項有趣的研究（Tannheimer等人， 2009 年）發現，在白朗峰（海拔4808公尺）完成跑步任務所需的時間以及完成該任務時的最低血氧飽和度可以預測個體在進一步攀登過程中發生AMS的風險。因此，除了在高海拔地區測量血氧飽和度（ SpO2 ）外，其他易於測量的參數（例如呼吸頻率、運動時間）可能有助於提高SpO2 讀數在預測AMS方面的準確性。一項近期開展的、引人入勝且全面的研究（Richalet等人， 2012）納入了1326名受試者，結果表明，在前往海拔4000米以上地區之前，低氧環境下運動時氧飽和度下降22%或以上是導致嚴重高原反應的獨立危險因素。該研究並未探討對較輕微的AMS的易感性，且該研究存在方法學缺陷，即超過三分之二的受試者未能完成研究。
事實上，有大量醫學文獻支持使用脈搏血氧飽和度監測儀，根據基線讀數預測AMS。 AMS與SpO₂降低之間聯繫的至少一個可能的病理生理學解釋是通氣不足。如果過度通氣是適應高原環境的基石，那麼AMS患者可能出現通氣不足，從而導致SpO₂降低（ Basnyat和Murdoch， 2003）。另一個病理生理機制可能是亞臨床肺水腫(很輕微尚未出現症狀的肺水腫)，正如Ge及其同事（1997）所展示的那樣，他們測量了32名受試者在海拔2260米處以及上升至4700米後的肺一氧化碳彌散量（DLCO）。在非AMS受試者中，DLCO隨海拔升高而增加，而在AMS患者中，DLCO並未顯著增加。然而，當Dehnert等人… （2010 年）試圖在海拔高達 4559 公尺的個體中重現這一發現，但他們未能重現這些結果。
脈搏血氧儀甚至被用於預測登頂成功率（Tannheimer等人， 2002）。但顯然，脈搏血氧儀讀數存在潛在的缺陷；例如，需要考慮個體差異、海拔高度的閾值以及SpO2的較大標準偏差（ Luks和Swenson， 2011 ； Windsor， 2012；Zafren， 2012）。
鑑於脈搏血氧儀的普及程度，無論我們今天對AMS的立場如何，登山者仍會繼續使用它來預測AMS。因此，進行更多關於此主題的研究（包括特定脈搏血氧儀的準確性及其誤差範圍、統一的測量方法以及避免數據誤讀）以「完善」這門科學至關重要。
Pulse oximeters are easy to use, noninvasive tools for the assessment of individuals at high altitude. These instruments provide an estimate in percentage of arterial hemoglobin oxygen saturation, which is a function of arterial partial pressure of oxygen. The percentage denotes the hemoglobin binding sites that are occupied at any one time by oxygen. At sea level, healthy individuals will be on the flat portion of the oxyhemoglobin dissociation curve, but at high altitude as the partial pressure of oxygen decreases with ascent, individuals will be at the steep portion of the curve (a slippery slope by comparison) where saturation changes significantly with respect to small changes in the partial pressure.
Most trekking and expedition groups use pulse oximeters as a novelty item, and many groups carry an inexpensive, pocket pulse oximeter (some as little as US $30) to periodically check the oxygen saturation (Spo2) as they as ascend up the trail. Based on medical literature, the pulse oximetery, though not 100% accurate, is useful in predicting acute mountain sickness (AMS).
Many studies have attempted to see if there is a link between hypoxemia and the likelihood of developing AMS. Some of these studies have used a prospective design to determine if decreased oxygen saturation earlier in the trip have increased the likelihood of suffering from AMS (Roach et al., 1998; Tannheimer et al., 2002; Karinen et al., 2010; Chen et al., 2012; Wagner et al., 2012; Faulhaber et al., 2014). Except for two studies above (Chen et al. and Wagner et al.), all the other studies in these prospective observations found a link. For example, Karinen et al. (2010) studied 83 ascents during eight expeditions. They measured both resting Spo2 (R-Spo2) and exercise Spo2 (Ex-Spo2) after moderate daily exercise [50 m walking, target heart rate 150 bpm] at altitudes of 2400 to 5300 m during ascent. The Lake Louise Score (Roach, 1993) was used in the diagnosis of AMS. Ex-Spo2 was lower at all altitudes among those climbers suffering from AMS during the expeditions than among those climbers who did not get AMS at any altitude during the expeditions. Reduced R-Spo2 and Ex-Spo2 measured at altitudes of 3500 and 4300 m seem to predict impending AMS at altitudes of 4300 m and 5300 m.
Why were the studies by Chen et al. (2012) and Wagner et al. (2012) different from the rest? One explanation may lie in the methodology of these studies. Error ranges in various pulse oximeters may be different. Large error ranges may not be good enough when small differences are being looked for. Other reasons for the differing results may be test performance methods, and possibly differences in assessment of clinical significance.
There are no randomized controlled trials (RCTs) of hypoxemic individuals to determine if starting them on AMS prophylaxis after they are identified as having a low Spo2 prevents AMS later in the trip. But RCTs using acetazolamide vs. other drugs or placebo in the prevention of AMS in the Everest region have consistently shown that those participants on acetazolamide were not only significantly more protected from AMS, but also had significant increased changes in their Spo2 compared to the drug or placebo group from the baseline, even though the actual changes were small (Basnyat et al., 2003; Gertsch et al., 2004; Basnyat et al., 2011). This is not to advocate using pulse oximetry to determine who should take acetazolamide.
An important review (Burtscher et al., 2008) of exposure to simulated hypoxia with measurement of arterial oxygen saturation to determine AMS susceptibility has also been carried out. Sixteen studies were reviewed where Sao2 was measured 20 to 30 min after exposure to simulated hypoxia equivalent to 2300 to 4200 m. The saturation values correctly predicted AMS susceptibility >80% of cases. Recently another study (Faulhaber et al., 2014) revealed that the additional determination of breathing frequency to oxygen saturation reading after 30 min exposure to simulated hypoxia can improve success in AMS prediction. Yet another interesting study (Tannheimer et al., 2009) revealed that the time necessary to complete a running task at high altitude on Mont Blanc (4808 m) and the lowest oxygen saturation while performing this task was predictive of an individual's risk of developing altitude sickness with further ascent. Hence other easily measurable parameters (such as respiratory rate, exercise time) in addition to measurement of Spo2 at high altitude may help improve the accuracy of the Spo2 readings vis a vis prediction of AMS. A fascinating, comprehensive recent study (Richalet et al., 2012) of 1326 subjects revealed that oxygen desaturation equal to or greater than 22% at exercise in hypoxia before a sojourn to >4000 m was an independent risk factor for predisposing a person to severe altitude sickness. The study did not address predisposition to the more benign form of the disease (i.e., AMS) and the study also had a methodological flaw in that more than two-thirds of the subjects did not complete the study.
Indeed, there is no dearth of medical literature supporting the use of pulse oximetry to predict AMS at a higher altitude from a baseline reading. At least one possible pathophysiological rationale for the link between AMS and decreased Spo2 may be adequate ventilation. If hyperventilation is the cornerstone of acclimatization, AMS patients may have hypoventilation with resultant decreased Spo2 (Basnyat and Murdoch, 2003). Another pathophysiological mechanism may be subclinical pulmonary edema as shown by Ge and colleagues (1997) who measured pulmonary diffusion capacity for carbon monoxide (DLCO) in a group of 32 subjects at 2260 m and following ascent to 4700 m. In subjects without AMS, the DLCO increased at higher altitude while in AMS patients the DLCO did not increase significantly. However when Dehnert et al. (2010) tried to reproduce this finding in individuals sojourning up to 4559 m, they were unable to replicate these results.
Pulse oximeters are even being used to predict summit success(Tannheimer et al., 2002). But clearly there are potential pitfalls of pulse oximeter readings; for example, individual variations, cut- offs for altitudes, and large standard deviations of the Spo2 need to be taken into account (Luks and Swenson, 2011; Windsor, 2012; Zafren, 2012).
Given the popularity of pulse oximeters, mountain sojourners will continue to use them to try to predict AMS, regardless of where we stand on this issue today. It is therefore very important to do further studies on this topic (including accuracy of particular pulse oximeters and their error ranges, uniform measurement methods, and avoiding misinterpretation of data) to “refine” this science.
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