The correct measurement of oxygen saturation at high altitude

Initial Treatment of High-Altitude Pulmonary Edema: Comparison of Oxygen and Auto-PEEP

BACKGROUND

Improvement of oxygenation is the aim in the therapy of high-altitude pulmonary edema (HAPE). However, descent is often difficult and hyperbaric chambers, as well as bottled oxygen, are often not available. We compare Auto-PEEP (AP-Pat), a special kind of pursed lips breathing, against the application of bottled oxygen (O₂-Pat) in two patients suffering from HAPE.

METHODS

We compare the effect of these two different therapies on oxygen saturation measured by pulse oximetry (SpO₂) over time.

RESULT

In both patients SpO₂ increased significantly from 65-70% to 95%. Above 80% this increase was slower in AP-Pat compared with O₂-Pat. Therapy started immediately in AP-Pat but was delayed in O₂-Pat because of organizational and logistic reasons.

CONCLUSIONS

The well-established therapies of HAPE are always the option of choice, if available, and should be started as soon as possible. The advantage of Auto-PEEP is its all-time availability. It improves SpO₂ nearly as well as 3 L/min oxygen and furthermore has a positive effect on oxygenation lasting for approximately 120 min after stopping. Auto-PEEP treatment does not appear inferior to oxygen treatment, at least in this cross-case comparison. Its immediate application after diagnosis probably plays an important role here.

Effects of Acute Exposure and Acclimatization to High-Altitude on Oxygen Saturation and Related Cardiorespiratory Fitness in Health and Disease

Maximal values of aerobic power (VO₂max) and peripheral oxygen saturation (SpO₂max) decline in parallel with gain in altitude. Whereas this relationship has been well investigated when acutely exposed to high altitude, potential benefits of acclimatization on SpO₂ and related VO₂max in healthy and diseased individuals have been much less considered. Therefore, this narrative review was primarily aimed to identify relevant literature reporting altitude-dependent changes in determinants, in particular SpO₂, of VO₂max and effects of acclimatization in athletes, healthy non-athletes, and patients suffering from cardiovascular, respiratory and/or metabolic diseases. Moreover, focus was set on potential differences with regard to baseline exercise performance, age and sex. Main findings of this review emphasize the close association between individual SpO₂ and VO₂max, and demonstrate similar altitude effects (acute and during acclimatization) in healthy people and those suffering from cardiovascular and metabolic diseases. However, in patients with ventilatory constrains, i.e., chronic obstructive pulmonary disease, steep decline in SpO₂ and V̇O₂max and reduced potential to acclimatize stress the already low exercise performance. Finally, implications for prevention and therapy are briefly discussed.

Monitoring Acclimatization and Training Responses Over 17–21 Days at 1,800 m in Elite Cross-Country Skiers and Biathletes

Objective

To monitor the daily variations and time course of changes in selected variables during a 17–21-day altitude training camp at 1,800 m in a group of elite cross-country skiers (9 women, 12 men) and biathletes (7 women, 4 men).

Methods

Among other variables, resting peripheral oxygen saturation (SpO_2rest), resting heart rate (HR_rest) and urine specific gravity (USG) were monitored daily at altitude, while illness symptoms were monitored weekly. Before and after the camp, body composition (i.e., lean and fat mass) and body mass were assessed in all athletes, while roller-skiing speed at a blood lactate concentration of 4 mmol·L⁻¹ (Speed_@4mmol) was assessed in the biathletes only.

Results

Neither SpO_2rest, HR_rest nor USG changed systematically during the camp (p > 0.05), although some daily time points differed from day one for the latter two variables (p < 0.05). In addition, body composition and body mass were unchanged from before to after the camp (p > 0.05). Eleven out of 15 illness episodes were reported within 4 days of the outbound or homebound flight. The five biathletes who remained free of illness increased their Speed_@4mmol by ~ 4% from before to after the camp (p = 0.031).

Conclusions

The present results show that measures typically recommended to monitor acclimatization and responses to altitude in athletes (e.g., SpO_2rest and HR_rest) did not change systematically over time. Further research is needed to explore the utility of these and other measures in elite endurance athletes at altitudes typical of competition environments.

Skin Pigmentation Influence on Pulse Oximetry Accuracy: A Systematic Review and Bibliometric Analysis

Nowadays, pulse oximetry has become the standard in primary and intensive care units, especially as a triage tool during the current COVID-19 pandemic. Hence, a deeper understanding of the measurement errors that can affect precise readings is a key element in clinical decision-making. Several factors may influence the accuracy of pulse oximetry, such as skin color, body temperature, altitude, or patient movement. The skin pigmentation effect on pulse oximetry accuracy has long been studied reporting some contradictory conclusions. Recent studies have shown a positive bias in oxygen saturation measurements in patients with darkly pigmented skin, particularly under low saturation conditions. This review aims to study the literature that assesses the influence of skin pigmentation on the accuracy of these devices. We employed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to conduct a systematic review retrospectively since February 2022 using WOS, PubMed, and Scopus databases. We found 99 unique references, of which only 41 satisfied the established inclusion criteria. A bibliometric and scientometrics approach was performed to examine the outcomes of an exhaustive survey of the thematic content and trending topics.

Altitude and Quality of Life of Older People in Colombia: A Multilevel Study

Objective

To assess the association between municipality altitude and quality of life (QOL) of older people in Colombia.

Methods

Cross-sectional study with data from the Colombian Demographic and Health Survey Older Adult Questionnaire 2015 (N = 13,970). QOL was measured in six domains: physical health, psychological health, functional status, social relations, medical history and economic status. Regression analyses were carried out adjusting by individual and contextual level variables.

Results

Low altitude was associated with better QOL: physical health (OR = 1.92, 95%CI 1.47−2.52), psychological health (OR = 1.59, 95%CI 1.26−2.00), functional status (OR=1.80, 95%CI 1.45−2.23), social relations (OR = 2.16 95%CI 1.73−2.70), and medical history (OR = 1.57, 95%CI 1.37−1.81). Economic status was not associated with altitude.

Discussion

Living at high altitude was associated with lower QOL for Colombian older adults. This finding encourages further study of high altitude and health outcomes among older adults in Colombia and other countries with populations living at high altitudes.

The Use of Pulse Oximetry in the Assessment of Acclimatization to High Altitude

Background: Finger pulse oximeters are widely used to monitor physiological responses to high-altitude exposure, the progress of acclimatization, and/or the potential development of high-altitude related diseases. Although there is increasing evidence for its invaluable support at high altitude, some controversy remains, largely due to differences in individual preconditions, evaluation purposes, measurement methods, the use of different devices, and the lacking ability to interpret data correctly. Therefore, this review is aimed at providing information on the functioning of pulse oximeters, appropriate measurement methods and published time courses of pulse oximetry data (peripheral oxygen saturation, (SpO₂) and heart rate (HR), recorded at rest and submaximal exercise during exposure to various altitudes. Results: The presented findings from the literature review confirm rather large variations of pulse oximetry measures (SpO₂ and HR) during acute exposure and acclimatization to high altitude, related to the varying conditions between studies mentioned above. It turned out that particularly SpO₂ levels decrease with acute altitude/hypoxia exposure and partly recover during acclimatization, with an opposite trend of HR. Moreover, the development of acute mountain sickness (AMS) was consistently associated with lower SpO₂ values compared to individuals free from AMS. Conclusions: The use of finger pulse oximetry at high altitude is considered as a valuable tool in the evaluation of individual acclimatization to high altitude but also to monitor AMS progression and treatment efficacy.

Rapid ascents of Mt Everest: normobaric hypoxic preacclimatization

BACKGROUND

Acclimatization to high altitude is time consuming. An expedition to Mt Everest (8848 m) requires roughly 8 weeks. Therefore it seems very attractive to reach the summit within 3 weeks from home, which is currently promised by some expedition tour operators. These rapid ascent expeditions are based on two main components, normobaric hypoxic training (NHT) prior to the expedition and the use of high flow supplemental oxygen (HFSO2). We attempted to assess the relative importance of these two elements.

METHODS

We evaluated the effect of NHT on the basis of the available information of these rapid ascent expeditions and our experiences made during an expedition to Manaslu (8163 m) where we used NHT for preacclimatization. To evaluate the effect of an increased O2 flow rate we calculated its effect at various activity levels at altitudes of 8000 m and above.

RESULTS

So far rapid ascents to Mt Everest have been successful. The participants carried out 8 weeks of NHT, reaching sleeping altitudes = 7100 m and spent at least 300 h in NH. At rest a flow rate of 2 l O2/min is sufficient to keep the partial pressure of inspired oxygen (PIO2) close to 50 mm Hg even at the summit. For ativities of ~80% of the maximum rate of oxygen consumption (VO2max) at the summit 6 l O2/min are required to maintain a PIO2 above 50 mm Hg.

DISCUSSION

NHT for preacclimatization seems to be the decisive element of the offered rapid ascent expeditions. An increased O2 flow rate of 8 l/min is not mandatory for climbing Mt Everest.

CONCLUSIONS

Preacclimatization using normobaric hypoxica (NH) is far more important than the use of HFSO2. We think that NHT will be widely used in the future. The most effective regimen of preacclimatization in NH, the duration of each session and the optimal FIO2 are still unclear and require further study.

High Altitude and Its Effects on Oral Health: A Review of Literature

Health deterioration at high altitudes is related to many pathophysiological processes. The literature contains much evidence describing the multiple factors responsible for this deterioration, including hypoxia, decreased oxygen saturation, and decreased barometric pressure. An increase in the levels of oxidative stress at high altitudes can lead to many serious health events, although the human body may be able to adapt to such changes in the case of people who are accustomed to living at a high altitude. The pathophysiological processes at high altitudes also have adverse effects on oral tissue health. The aim of this review is to summarize the major published findings about oral health deterioration of living in and travelling to high-altitude areas.

Most studies have noted the adverse effects of prolonged exposure to hypoxia at high altitudes on oral tissues, including the salivary gland, periodontal tissue, gingival crevicular fluids, and jawbone. These changes include increases in the levels of inflammatory mediators and periodontal inflammation parameters. In addition, the incidence and severity of dental fluorosis is higher in residents of high-altitude areas. Abrupt changes in barometric pressure in people who travel to high altitudes may cause dental barotrauma and appear to increase sensitivity to pain (barodontalgia). In conclusion, it is important to consider that travelling to and living in high-altitude areas is a possible risk factor for multiple oral diseases.

Singing Improves Oxygen Saturation in Simulated High-Altitude Environment

At high altitude, low oxygen partial pressure predisposes human body to hypobaric hypoxia that may lead to high-altitude illness. Currently, singing had been used for rehabilitation of patients with lung diseases but its role in high-altitude low oxygen environment is still scarce. This study aims to examine the effect of singing in improving oxygen saturation at different levels of high altitudes in a hypobaric chamber. Eight healthy volunteers were assigned to three interventions at three simulated altitudes (sea level, 3000 m and 5000 m). The oxygen saturation (SpO₂) was measured via pulse oximetry under three conditions: no singing (NS), singing aloud (SA), and singing silently (SS). The "birthday song" was used as the standard song for 4 minutes. At sea level, mean NS SpO₂ was 97.75% ± 1.04%. With SS, the level increased to 98.25% ± 1.04%. Mean SA SpO₂ increased to 98.38% ± 0.92% (P < 0.05). At 3000 m, mean NS SpO₂ was 92.75% ± 3.73% and rose to 94.50% ± 2.51% and 94.63% ± 2.00% respectively with SA and SS (P < 0.05). At 5000 m, NS level of 79.88P ± 3.60% increased to 82.13 ± 5.87 and 82.88% ± 7.12% with SA and SS respectively (P < 0.05). The repeated measure ANOVA showed significant difference for altitude (P < 0.001) and intervention (P = 0.05). In conclusion, singing both either "aloud" or "silently" significantly increased the level of SpO₂ in simulated high altitude at 3000 m and above. The study suggests that singing as a potential intervention to improve oxygen saturation at high altitudes. Study with larger sample in hypobaric chamber as well as in real environment is recommended.

Positional Changes in Arterial Oxygen Saturation and End-Tidal Carbon Dioxide at High Altitude: Medex 2015

Background: Body position alters aspects of pulmonary function in health and disease. Although studies have assessed positional effects on the heart and lungs, little is known about positional changes in gas exchange parameters at high altitude. We hypothesized that following ascent, supine positioning would cause lower oxygen saturation than sitting, partially due to decreased ventilation and increased partial pressure of end-tidal carbon dioxide (Petco₂). Materials and Methods: Twenty-eight healthy subjects were studied at sea level and following gradual ascent to 5150 m. After 10 minutes of sitting rest, subjects were studied for 5 minutes each in the sitting, supine, and prone positions with the order randomly assigned. Pulse oximeter oxygen saturation (SpO₂), minute ventilation (V_E), end-tidal O₂ (Peto₂) and Petco₂, oxygen consumption, and CO₂ production were continuously measured. Alveolar ventilation (V_A) was calculated from the measured parameters. Results: At high altitude, V_E was not affected by body position (12.96 ± 3.09 and 11.54 ± 3.45 L/min in the sitting and supine positions, respectively, p = 0.255). Petco₂ increased from sitting to supine (22.8 ± 3.1 to 23.5 ± 3.3 mm Hg, p < 0.005), but V_E and Petco₂ were not different between the supine and prone positions. Calculated V_A was not significantly affected by body position at either sea level or high altitude. SpO₂ decreased from 81.3% ± 4.4% sitting to 78.8% ± 6.0% supine (p = 0.025), with a mean positional SpO₂ difference of 2.5% ± 4.9% (95% confidence interval 0.6%-4.4%). SpO₂ was not different between the supine and prone positions. Twenty-two of 28 subjects had lower SpO₂ supine compared with sitting. Conclusions: These results extend earlier low-altitude studies and demonstrate the importance of postural regulation in different environments. As 79% of subjects had lower SpO₂ while supine than sitting, control of body position is necessary for SpO₂ comparisons at altitude to be meaningful.