ECSS Paris 2023: CP-PN10
INTRODUCTION: Patent foramen ovale (PFO) is an opening between the right and left atria of the heart, present in ~25-40% of the population [1,2]. As blood passes through the lungs, it acts as a “radiator” to help dissipate heat from the body and aid in cooling. In individuals with a PFO (PFO+), blood bypasses the respiratory “radiator” and does not get cooled through the pulmonary circulation. In support of this theory, previous work has found that PFO+ individuals have elevated core body temperature by ~0.4 degrees Celsius (DegC) at rest, which persists during cycling exercise at sea-level [3,4]; however, this has not been tested at high-altitude, which alters resting alveolar ventilation and thermoregulation. We hypothesized that at sea-level and high-altitude: 1) rectal core temperature (TREC) at rest, and during cycling exercise, would remain elevated in PFO+ compared to PFO-, 2) the partial pressure of arterial oxygen (PaO2) and oxygen saturation (SaO2) would be reduced, but the partial pressure of arterial carbon dioxide (PaCO2) would be elevated, in PFO+ compared to PFO-. METHODS: PFO screening was completed via agitated saline contrast echocardiography in 25 individuals (n=6 PFO+, n=19 PFO-). The presence of a PFO was determined if bubbles appeared in the left atria ≤3 cardiac cycles [5]. Participants performed a five-kilometer cycling time-trial at sea-level (334m) and after 4-8 days at high-altitude (~3,800m). We recorded TREC and collected arterial blood samples at rest, and at each kilometer of cycling exercise. RESULTS: At rest, PFO+ participants had an elevated sea-level TREC compared to PFO- individuals (0.47+0.36 DegC], p=0.02), but this difference became non-significant after acclimatizing to high-altitude (0.35+0.35DegC, p=0.09). The TREC response to cycling exercise was not different between PFO+ and PFO- at both sea-level and high-altitude (both p≥0.66). Additionally, at rest SaO2 was difference between PFO+ verses PFO-, but no interaction effect (p=0.016). In contrast, during exercise there was no SaO2 difference between groups at sea-level (p=0.21), but there was a trend toward reduction in PFO+ at high-altitude (p=0.052). With regards to arterial blood gases, there was no difference at rest or exercise between groups at sea-level or high-altitude in PaO2 and PaCO2 (both p>0.74). CONCLUSION: We found that the resting TREC difference between PFO+ and PFO- individuals observed at sea-level may be attenuated at high-altitude, with no group differences in the TREC response to exercise. Additionally, there were no differences in arterial blood data between groups. These data indicate that presence of PFO has minimal response to core temp and arterial blood gases during exercise at sea-level and high-altitude. [1] Lechat 1988/ [2] Hagen 1984/ [3] Lovering 2011/ [4] Davis 2015/ [5] Silvestry 2015
Read CV Samantha TsiorosECSS Paris 2023: CP-PN10
INTRODUCTION: Acid-base regulation plays a central role in exercise physiology, inducing changes in ventilation, buffering capacity, and the development of fatigue during endurance and high-intensity exercise. Hypobaric hypoxia (i.e. high altitude) elicits a hypoxic ventilatory response, the magnitude of which may be sex dependent (1). The hypoxic ventilatory response attenuates the decline of arterial oxygen (PaO2), but also reduces the partial pressure of arterial carbon dioxide (PaCO2), resulting in respiratory-induced alkalosis. Eventually, the alkalosis is corrected by renal bicarbonate (HCO3-) excretion to return pH near low-altitude values. Therefore, the purpose of this study was to characterize differences in acid-base balance between males and females at sea-level and during high altitude acclimatization. It was hypothesized that both males and females would demonstrate respiratory alkalosis at high altitude, with males exhibiting a larger reduction in PaCO2 and greater increase in pH, consistent with a stronger hypoxic ventilatory response. METHODS: Eighteen healthy lowlanders (9 male, 9 female), all living below 500 m were studied at sea level (Guelph, ON, Canada; 340 m) and again between days 3-7 at high-altitude (Barcroft Research Station; 3,800 m). Arterial (brachial) blood samples were taken at rest and analyzed immediately for blood gases and pH (Radiometer ABL90 Flex) Two-way repeated measures ANOVAs were used to assess condition and sex effects. RESULTS: At high-altitude, pH was elevated in both males and females compared to sea-level (7.42±0.01 to 7.47±0.01 and 7.42±0.02 to 7.45±0.01, respectively; p<0.01); however, this response was augmented in males (p=0.04). PaCO₂ decreased with high-altitude exposure in males and females (38.9±2.1 to 29.1±3.0 and 35.7±1.7 to 29.3±1.3 respectively; p<0.01), due to an increase in alveolar ventilation at high-altitude this response was exacerbated in males compared to females (p<0.01 and p=0.02, respectively). Similarly, PaO₂ was reduced at high-altitude in both males and females (91.8±6.8 to 55.9±6.1 and 101.0±4.3 to 53.7±4.0 respectively; p<0.01), and this reduction was more pronounced in females compared to males (p<0.01). There was a metabolic compensation via increased [HCO₃⁻] excretion at high-altitude in response to the respiratory alkalosis (p<0.01). The magnitude of [HCO₃⁻] excretion in response to high-altitude was similar between males and females (p=0.52). However, [HCO₃⁻] was elevated in males at both sea-level and high-altitude compared to females (25.1±0.9 to 23.2±1.2 and 23.9±1.0 to 22.3±0.6, respectively; p=0.01). CONCLUSION: These findings demonstrate that there are sex differences in acid-base regulation in response to 4-8 days of high-altitude acclimatization. Males exhibited a greater alkalosis and larger reductions in PaCO2, consistent with an augmented ventilatory response, whereas females experienced a greater decline in PaO2. 1 Raberin, A., Burtscher, J., Citherlet, T. Sports Med 2024 54:271–287
Read CV Ty MacdonaldECSS Paris 2023: CP-PN10
INTRODUCTION: Sleep and oxygen availability are fundamental for maintaining metabolic homeostasis and central nervous system integrity. High-altitude expeditions frequently involve a dangerous combination of systemic hypoxia and severe sleep restriction (SR). While isolated effects are well-documented, integrative research—particularly protocols reflecting the long-duration physical effort and cumulative fatigue occurring during mountain expeditions—is significantly lacking. This review synthesizes current evidence to identify cognitive risks and gaps in expedition safety. METHODS: Reporting followed PRISMA guidelines to ensure methodological transparency and rigor. Studies were identified through PubMed, SPORTDiscus, and Web of Science. Scientific databases were queried using specific search keys: “sleep” OR “sleep deprivation” OR “sleep restriction” AND “mountain” OR “hypoxia” OR “altitude” OR “physical performance” “cognitive performance”. Included were peer-reviewed English articles analyzing sleep manipulation in mountain or hypoxic environments on cognitive or physical performance. Methodological quality was appraised using the Mixed Methods Appraisal Tool (MMAT). Evidence was qualitatively synthesized from five sources, comprising four randomized crossover experimental trials and one large-scale descriptive field study. RESULTS: The available literature indicates that while moderate hypoxia alone has limited cognitive effects, its combination with SR significantly degrades performance. Sleep loss—from partial to total deprivation—reduces executive function throughput across domains such as inhibition and working memory. When hypoxia and SR co-occur, individuals report peak levels of subjective mental workload and exhibit increased error rates in complex tracking tasks. Neurophysiologically, SR is the primary driver of diminished attentional capacity and disrupted neural synchronization, with moderate hypoxia exacerbating these existing deficits. The visual attentional system demonstrates higher sensitivity and delayed latencies compared to the auditory system under dual stress. Field data from 1,154 mountain reveals that 80% experience symptoms such as hallucinations (34%) and falls (15%). Crucially, "banking sleep" and 20-minute bouts of moderate exercise can reduce these cognitive decrements CONCLUSION: Hypoxia and sleep loss synergistically compromise the prefrontal cortex, the primary region associated with executive functions. While respiratory and ocular parameters provide robust non-invasive monitoring for mental overload, laboratory models currently fail to simulate the cumulative physical fatigue of actual mountain travel. Practically, "sleep banking" reduces fall risks, while prioritizing auditory over visual alerts ensures safety information is processed more effectively under combined stress. Future research must prioritize protocols reflecting the prolonged physical effort occurring during mountain expeditions to accurately model and mitigate expedition risks.
Read CV Mateusz ŚwiątekECSS Paris 2023: CP-PN10