UBC-Nepal expedition: markedly lower cerebral blood flow in high-altitude Sherpa children compared with children residing at sea level

[Amplitude-integrated electroencephalography monitoring results of hospitalized neonates in plateau areas]

OBJECTIVES

To investigate the amplitude-integrated electroencephalography (aEEG) monitoring results of hospitalized neonates in plateau areas.

METHODS

A retrospective analysis was conducted on 5 945 neonates who were admitted to the Department of Neonatology, Kunming Children's Hospital, and received aEEG monitoring from January 2020 to December 2022. According to the aEEG monitoring results, they were divided into a normal aEEG group and an abnormal aEEG group. The incidence rate of aEEG abnormalities was analyzed in neonates with various systemic diseases, as well as the manifestations of aEEG abnormalities and the consistency between aEEG abnormalities and clinical abnormalities.

RESULTS

Among the 5 945 neonates, the aEEG abnormality rate was 19.28% (1 146/5 945), with an abnormality rate of 29.58% (906/3 063) in critically ill neonates and 8.33% (240/2 882) in non-critically ill neonates (P<0.05). The children with inherited metabolic diseases showed the highest aEEG abnormality rate of 60.77% (79/130), followed by those with central nervous system disorders [42.22% (76/180)] and preterm infants [35.53% (108/304)]. Compared with the normal aEEG group, the abnormal aEEG group had significantly lower age and gestational age, as well as a significantly lower birth weight of preterm infants (P<0.05). Among the 1 146 neonates with aEEG abnormalities, the main types of aEEG abnormalities were sleep cycle disorders in 597 neonates (52.09%), background activity abnormalities in 294 neonates (25.65%), and epileptiform activity in 255 neonates (22.25%), and there were 902 neonates (78.71%) with abnormal clinical manifestations. The sensitivity and specificity of aEEG monitoring for brain function abnormalities were 33.51% and 92.50%, respectively.

CONCLUSIONS

In plateau areas, there is a relatively high rate of aEEG abnormalities among hospitalized neonates, particularly in critically ill neonates and those with smaller gestational ages and younger ages, suggesting a high risk of brain injury. Therefore, routine aEEG monitoring for the hospitalized neonates can help with the early detection of brain function abnormalities, the decision-making in treatment, and the formulation of brain protection strategies.

To the extreme! How biological anthropology can inform exercise physiology in extreme environments

The fields of biological anthropology and exercise physiology are closely related and can provide mutually beneficial insights into human performance. These fields often use similar methods and are both interested in how humans function, perform, and respond in extreme environments. However, these two fields have different perspectives, ask different questions, and work within different theoretical frameworks and timescales. Biological anthropologists and exercise physiologists can greatly benefit from working together when examining human adaptation, acclimatization, and athletic performance in the extremes of heat, cold, and high-altitude. Here we review the adaptations and acclimatizations in these three different extreme environments. We then examine how this work has informed and built upon exercise physiology research on human performance. Finally, we present an agenda for moving forward, hopefully, with these two fields working more closely together to produce innovative research that improves our holistic understanding of human performance capacities informed by evolutionary theory, modern human acclimatization, and the desire to produce immediate and direct benefits.

Dynamic onset response of the internal carotid artery to hypercapnia is blunted in children compared with adults

Intracranial blood velocity reactivity to a steady‐state hypercapnic stimulus has been shown to be similar in children and adults, but the onset response to hypercapnia is slower in the child. Given the vasodilatory effect of hypercapnia on the cerebrovasculature, assessment of vessel diameter, and blood flow are vital to fully elucidate whether the temporal hypercapnic response differs in children versus adults. Assessment of internal carotid artery (ICA) vessel diameter (ICAd), blood velocity (ICAv), volumetric blood flow (Q_ICA), and shear rate (ICA_SR) in response to a 4 min hypercapnic challenge was completed in children (n = 14, 8 girls; 9.8 ± 0.7 years) and adults (n = 17, 7 females; 24.7 ± 1.8 years). The dynamic onset responses of partial pressure of end‐tidal CO₂ (P_ETCO₂), Q_ICA, ICAv, and ICA_SR to hypercapnia were modeled, and mean response time (MRT) was computed. Following 4 min of hypercapnia, ICA reactivity and ICAd were comparable between the groups. Despite a similar MRT in P_ETCO₂ in children and adults, children had slower Q_ICA (children 108 ± 60 s vs. adults 66 ± 37 s; p = 0.023), ICAv (children 120 ± 52 s vs. adults 52 ± 31 s; p = 0.001), and ICA_SR (children 90 ± 27 s vs. adults 47 ± 36 s; p = 0.001) MRTs compared with adults. This is the first study to show slower hypercapnic hyperemic kinetic responses of the ICA in children. The mechanisms determining these differences and the need to consider the duration of hypercapnic exposure when assessing CVR in children should be considered in future studies.

UBC-Nepal Expedition: Cerebrovascular Responses to Exercise in Sherpa Children Residing at High Altitude

Understanding the process of successful adaptation to high altitude provides valuable insight into the pathogenesis of conditions associated with impaired oxygen uptake and utilization. Prepubertal children residing at low altitude show a reduced cerebrovascular response to exercise in comparison to adults, and a transient uncoupling of cerebral blood flow to changes in the partial pressure of end-tidal CO₂ (P_ETCO₂); however, little is known about the cerebrovascular response to exercise in high-altitude native children. We sought to compare the cerebral hemodynamic response to acute exercise between prepubertal children residing at high and low altitude. Prepubertal children (n = 32; 17 female) of Sherpa descent (Sherpa children [SC]) at high altitude (3800 m, Nepal) and maturational-matched (n = 32; 20 female) children (lowland children [LLC]) residing at low altitude (342 m, Canada). Ventilation, peripheral oxygen saturation (S_pO₂), P_ETCO_2, and blood velocity in the middle and posterior cerebral arteries (MCA_v and PCA_v) were continuously measured during a graded cycling exercise test to exhaustion. At baseline (BL), P_ETCO₂ (-19 ± 4 mmHg, p < 0.001), S_pO₂ (-6.0% ± 2.1%, p < 0.001), MCA_v (-12% ± 5%, p = 0.02), and PCA_v (-12% ± 6%, p = 0.04) were lower in SC when compared with LLC. Despite this, the relative change in MCA_v and PCA_v during exercise was similar between the two groups (p = 0.99). Linear regression analysis demonstrated a positive relationship between changes in P_ETCO₂ with MCA_v in SC (R² = 0.13, p > 0.001), but not in LLC (R² = 0.03, p = 0.10). Our findings demonstrate a similar increase in intra-cranial perfusion during exercise in prepubertal SC, despite differential BL values and changes in P_ETCO₂ and S_pO₂.

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya

The University of British Columbia Nepal Expedition took place over several months in the fall of 2016 and was comprised of an international team of 37 researchers. This paper describes the objectives, study characteristics, organization and management of this expedition, and presents novel blood gas data during acclimatization in both lowlanders and Sherpa. An overview and framework for the forthcoming publications is provided. The expedition conducted 17 major studies with two principal goals—to identify physiological differences in: 1) acclimatization; and 2) responses to sustained high-altitude exposure between lowland natives and people of Tibetan descent. We performed observational cohort studies of human responses to progressive hypobaric hypoxia (during ascent), and to sustained exposure to 5050 m over 3 weeks comparing lowlander adults (n = 30) with Sherpa adults (n = 24). Sherpa were tested both with (n = 12) and without (n = 12) descent to Kathmandu. Data collected from lowlander children (n = 30) in Canada were compared with those collected from Sherpa children (n = 57; 3400–3900m). Studies were conducted in Canada (344m) and the following locations in Nepal: Kathmandu (1400m), Namche Bazaar (3440m), Kunde Hospital (3480m), Pheriche (4371m) and the Ev-K2-CNR Research Pyramid Laboratory (5050m). The core studies focused on the mechanisms of cerebral blood flow regulation, the role of iron in cardiopulmonary regulation, pulmonary pressures, intra-ocular pressures, cardiac function, neuromuscular fatigue and function, blood volume regulation, autonomic control, and micro and macro vascular function. A total of 335 study sessions were conducted over three weeks at 5050m. In addition to an overview of this expedition and arterial blood gas data from Sherpa, suggestions for scientists aiming to perform field-based altitude research are also presented. Together, these findings will contribute to our understanding of human acclimatization and adaptation to the stress of residence at high-altitude.