Hypoxic Test Research Articles

Can resting lung function predict the response of a person living with motor neuron disease to a hypoxic challenge test?

People living with MND (PlwMND) are at risk of altitude-related hypoxia during flight. The Hypoxic Challenge Test (HCT) determines whether in-flight oxygen is required but can be expensive and inaccessible. To assist with travel recommendations, we investigated the relationship between altitude simulation-induced hypoxemia and baseline lung function. Retrospective audit of clinical database of PlwMND who had HCT and lung function. Pearson's correlation assessed relationships between oxygen saturation at altitude (AltSpO2) and lung function. Univariate logistic regression analysis and receiver operator characteristic (ROC) curves determined associations between lung function and HCT pass or fail. Between 2004-2023, 50 PlwMND were identified (median (IQR) diagnosis to HCT = 11.6 (16.9) months, mean ± SD forced vital capacity (FVC) = 2.4 ± 0.9 liters). Ten patients dropped below 85% SpO2 during testing (HCT fail). Baseline SpO2 was associated with AltSpO2 (r = 0.64) and predicted HCT pass or fail (OR 2.0 [95% CI 1.2-3.4], area under ROC curve (AUC) =0.8 [0.6-1.0]), as did FVC (AUC = 0.8 [0.6-0.9]). PlwMND with a FVC > 2.7L or a resting SpO2 > 97% are likely to pass HCT, whereas all those with FVC < 1L and SpO2 < 92% failed. PlwMND with FVC >2.7L or SpO2 >97% are unlikely to require oxygen or ventilatory supports for airline travel. A FVC below 2.7L will require a HCT to confidently determine HCT outcome, with testing still required for FVC <1L or baseline SpO2 <92%, to provide evidence to the airlines for in-flight respiratory support.

Effects of Taurine and Vitamin C on the Improvement of Antioxidant Capacity, Immunity and Hypoxia Tolerance in Gibel Carp (Carrassius auratus gibeilo).

To investigate the effects of taurine and vitamin C on gibel carp (Carrassius auratus gibeilo), fish (41.85 ± 0.03 g) were fed three diets with 0% taurine + 0% vitamin C (D0), 0.1% taurine + 0% vitamin C (D1), and 0.1% taurine + 0.1% vitamin C (D2) for 8 weeks. Then 12-hour hypoxic stress test was conducted. The results showed that weight gain rate (WGR), specific growth rate (SGR), and sustained swimming time (SST) were significantly increased in the D2. CAT, SOD, T-AOC, and GSH were increased. GSH-Px and il-6 were decreased in D1 and D2. In hypoxia, CAT and T-AOC were decreased, while GSH, sod, and nrf2 were the highest in D1. Compared to normoxia, GSH-Px was increased, while SOD and MDA were decreased. Il-10 and nf-κb were increased. Vegf, epo, and ho-1 were increased and they all were higher than that in normoxia. The number of gill cell mitochondria and survival rate (SR) of gibel carp had an increasing trend but no significant difference among groups. In conclusion, taurine with vitamin C improved the growth and SST of gibel carp, and taurine and taurine with vitamin C improved antioxidant capacity, immunity, and hypoxia tolerance.

Changes in hypoxic and hypercapnic ventilatory responses at high altitude measured using rebreathing methods.

Ventilatory responses to hypoxia and hypercapnia play a vital role in maintaining gas exchange homeostasis and in adaptation to high-altitude environments. This study investigates the mechanisms underlying sensitization of hypoxic and hypercapnic ventilatory response (HVR and HCVR, respectively) in individuals acclimatized to moderate high altitude (3,800 m). Thirty-one participants underwent chemoreflex testing using the Duffin-modified rebreathing technique. Measures were taken at sea level and after 2 days of acclimatization to high altitude. Ventilatory recruitment threshold (VRT), HCVR-Hyperoxia, HCVR-Hypoxia, and HVR were quantified. Acclimatization to high altitude resulted in increased HVR (P < 0.001) and HCVR-Hyperoxia (P < 0.001), as expected. We also observed that the decrease in VRT under hypoxic test conditions significantly contributed to the elevated HVR at high altitude since the change in VRT across hyperoxic and hypoxic test conditions was greater at high altitudes compared to baseline sea-level tests (P = 0.043). Pre-VRT, or basal, ventilation also increased at high altitudes (P < 0.001), but the change did not differ between oxygen conditions. Taken together, these data suggest that the increase in HVR at high altitude is at least partially driven by a larger decrease in the VRT in hypoxia versus hyperoxia at high altitude compared to sea level. This study highlights the intricacies of respiratory adaptations during acclimatization to moderate high altitude, shedding light on the roles of the VRT, baseline respiratory drive, and two-slope HCVR in this process. These findings contribute to our understanding of how human respiratory control responds to hypoxic and hypercapnic challenges at high altitude.NEW & NOTEWORTHY We report the first measurements of the hypoxic ventilatory response (HVR) after 2 days at high altitude using a CO2 rebreathing technique. We evaluated mechanisms by which the HVR becomes elevated with acclimatization (increased hypercapnic ventilatory response sensitivity in hypoxia, increased baseline respiratory drive in hypoxia, or lower ventilatory recruitment thresholds in hypoxia). For the first time, we report that decreases in the ventilatory recruitment threshold in hypoxia contribute to elevated HVR at high altitude.

The Analysis of The Functional Status of Female Soldiers In The Conditions of The Legal Regime of The Martial State

This article presents the results of a study on the cardiorespiratory system of 30 female soldiers during a period of legal regime of martial state. It is important to note that all investigated cardiovascular parameters, determined by median, were within age norms. Our findings from hypoxic tests demonstrated that the functional capacity of the respiratory system of female military personnel was within age norms as well. The results also confirm that this category has the ability to effectively operate in hypoxic conditions, which is a crucial aspect for professional performance. Analysis of orthostatic test results indicates a significant variability in the body’s reactions to body position changes, with a median value of 5.0 bpm, a minimum of 0.0 bpm, and a maximum of 56.0 bpm. This means that female soldiers have different levels of adaptation. However, it is worth noting the stability of the cardiovascular system’s response to orthostatic stress, with minimal changes in systolic and diastolic blood pressure at 5 mmHg, indicating cardiovascular stability during orthostatic activity. In the vast majority of female military personnel (60.0%), hemodynamic reactions to changes in body position indicate a high level of adaptive capacity of the cardiovascular system. The results of the study of the functional state of the cardiovascular and respiratory systems in female military personnel indicate compliance with the majority of physiological norms; however, isolated cases are observed where the detected values may indicate certain abnormalities, particularly arterial hypertension. The results of respiratory tests indicate a normal response of the female military personnel's bodies to hypoxia conditions, which is important for fulfilling their service duties.

A Step Test to Evaluate the Susceptibility to Severe High-Altitude Illness in Field Conditions.

Hermand, Eric, Léo Lesaint, Laura Denis, Jean-Paul Richalet, and François J. Lhuissier. A step test to evaluate the susceptibility to severe high-altitude illness in field conditions. High Alt Med Biol. 25:158-163, 2024.-A laboratory-based hypoxic exercise test, performed on a cycle ergometer, can be used to predict susceptibility to severe high-altitude illness (SHAI) through the calculation of a clinicophysiological SHAI score. Our objective was to design a field-condition test and compare its derived SHAI score and various physiological parameters, such as peripheral oxygen saturation (SpO2), and cardiac and ventilatory responses to hypoxia during exercise (HCRe and HVRe, respectively), to the laboratory test. A group of 43 healthy subjects (15 females and 28 males), with no prior experience at high altitude, performed a hypoxic cycle ergometer test (simulated altitude of 4,800 m) and step tests (20 cm high step) at 3,000, 4,000, and 4,800 m simulated altitudes. According to tested altitudes, differences were observed in O2 desaturation, heart rate, and minute ventilation (p < 0.001), whereas the computed HCRe and HVRe were not different (p = 0.075 and p = 0.203, respectively). From the linear relationships between the step test and SHAI scores, we defined a risk zone, allowing us to evaluate the risk of developing SHAI and take adequate preventive measures in field conditions, from the calculated step test score for the given altitude. The predictive value of this new field test remains to be validated in real high-altitude conditions.

Fitness Level- and Sex-Related Differences in Pulmonary Limitations to Maximal Exercise in Normoxia and Hypoxia.

Both maximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach its maximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations during maximal-intensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia. Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit. EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different ( P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio ( P = 0.029), higher ventilation (V̇ E ) ( P < 0.001), larger ΔVO 2max ( P = 0.019), and lower hypoxia-related V̇ E increase ( P < 0.001). Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions.

Right ventricular performance during acute hypoxic exercise.

Acute hypoxia increases pulmonary arterial (PA) pressures, though its effect on right ventricular (RV) function is controversial. The objective of this study was to characterize exertional RV performance during acute hypoxia. Ten healthy participants (34±10 years, 7males) completed three visits: visits 1 and 2 included non-invasive normoxic (fraction of inspired oxygen ( )=0.21) and isobaric hypoxic ( =0.12) cardiopulmonary exercise testing (CPET) to determine normoxic/hypoxic maximal oxygen uptake ( ). Visit 3 involved invasive haemodynamic assessments where participants were randomized 1:1 to either Swan-Ganz or conductance catheterization to quantify RV performance via pressure-volume analysis. Arterial oxygen saturation was determined by blood gas analysis from radial arterial catheterization. During visit 3, participants completed invasive submaximal CPET testing at 50% normoxic and again at 50% hypoxic ( =0.12). Median (interquartile range) values for non-invasive values during normoxic and hypoxic testing were 2.98 (2.43, 3.66) l/min and 1.84 (1.62, 2.25) l/min, respectively (P<0.0001). Mean PA pressure increased significantly when transitioning from rest to submaximal exercise during normoxic and hypoxic conditions (P=0.0014). Metrics of RV contractility including preload recruitable stroke work, dP/dtmax , and end-systolic pressure increased significantly during the transition from rest to exercise under normoxic and hypoxic conditions. Ventricular-arterial coupling was maintained during normoxic exercise at 50% . During submaximal exercise at 50% of hypoxic , ventricular-arterial coupling declined but remained within normal limits. In conclusion, resting and exertional RV functions are preserved in response to acute exposure to hypoxia at an =0.12 and the associated increase in PA pressures. KEY POINTS: The healthy right ventricle augments contractility, lusitropy and energetics during periods of increased metabolic demand (e.g. exercise) in acute hypoxic conditions. During submaximal exercise, ventricular-arterial coupling decreases but remains within normal limits, ensuring that cardiac output and systemic perfusion are maintained. These data describe right ventricular physiological responses during submaximal exercise under conditions of acute hypoxia, such as occurs during exposure to high altitude and/or acute hypoxic respiratory failure.

Psychological typification and reaction of the cardiovascular system of endurance athletes to multisensory interference. Part 2: the relationship between the psychological characteristics of a successful athlete and the response of heart rate to stressors

The search for methods of profiling and selecting athletes in order to preserve health and improve performance is one of the most important tasks of scientific and methodological support for sports training. The purpose of the study is to assess the possibility of determining the psychophysiological types of athletes when testing for resistance to multisensory interference. These data can later be used in combined psychophysiological methods of sports selection. The aim of the study is to find out whether certain psychological types of athletes may have characteristic physiological features of reactions to hypoxia, as well as to assess the applicability of the methods used. 28 cyclical sports athletes — male skiers and swimmers from 13 to 26 years old (Q1 (25 %) 18,2; median (50 %) 19,0; Q3 (75 %) 20,7) of various levels of athletic qualification were examined. A test was performed with normobaric 10 % hypoxia with an analysis of heart rate variability (HRV). Revealed: 1. differences in HRV profiles at rest and at the beginning of the hypoxic test in athletes of different sports qualifications, 2. certain combinations of personality traits of masters of cyclic sports correspond to characteristic HRV profiles. This study shows that the skill level of an athlete is reflected in the response to multisensory interference and the chosen research methods are adequate for the set goals. The limitations of this pilot study include the sample size, as well as the fact that only males participated in it. In the future, the authors plan to increase the sample depending on the size of the effect (at least 125 volunteers) to obtain more reliable data and qualitative conclusions.

Identifying the Causes of Unexplained Dyspnea at High Altitude Using Normobaric Hypoxia with Echocardiography.

Exposure to high altitude results in hypobaric hypoxia, leading to physiological changes in the cardiovascular system that may result in limiting symptoms, including dyspnea, fatigue, and exercise intolerance. However, it is still unclear why some patients are more susceptible to high-altitude symptoms than others. Hypoxic simulation testing (HST) simulates changes in physiology that occur at a specific altitude by asking the patients to breathe a mixture of gases with decreased oxygen content. This study aimed to determine whether the use of transthoracic echocardiography (TTE) during HST can detect the rise in right-sided pressures and the impact of hypoxia on right ventricle (RV) hemodynamics and right to left shunts, thus revealing the underlying causes of high-altitude signs and symptoms. A retrospective study was performed including consecutive patients with unexplained dyspnea at high altitude. HSTs were performed by administrating reduced FiO2 to simulate altitude levels specific to patients' history. Echocardiography images were obtained at baseline and during hypoxia. The study included 27 patients, with a mean age of 65 years, 14 patients (51.9%) were female. RV systolic pressure increased at peak hypoxia, while RV systolic function declined as shown by a significant decrease in the tricuspid annular plane systolic excursion (TAPSE), the maximum velocity achieved by the lateral tricuspid annulus during systole (S' wave), and the RV free wall longitudinal strain. Additionally, right-to-left shunt was present in 19 (70.4%) patients as identified by bubble contrast injections. Among these, the severity of the shunt increased at peak hypoxia in eight cases (42.1%), and the shunt was only evident during hypoxia in seven patients (36.8%). In conclusion, the use of TTE during HST provides valuable information by revealing the presence of symptomatic, sustained shunts and confirming the decline in RV hemodynamics, thus potentially explaining dyspnea at high altitude. Further studies are needed to establish the optimal clinical role of this physiologic method.

Retrospective analysis of referrals for hypoxic challenge testing in children born preterm

IntroductionChildren with a history of bronchopulmonary dysplasia (BPD) may be at risk of hypoxaemia at altitude, such as during air travel. We have performed preflight hypoxic challenge testing (HCT) since...

Реакція на дозовану гіпоксію у жінок, що перебували у стані хронічного стресу, зумовленого війною

Military stress has a traumatic effect on mental and physical health, and disrupts the adaptive capabilities of the body, in particular, its ability to adequately respond to hypoxia. However, the specifics of the reaction of the cardiorespiratory system to dosed hypoxia in individuals who experiencing warrelated chronic stress (WRCS) have not yet been elucidated. The peculiarities of the reaction of the cardiorespiratory system to dosed hypoxia in women experiencing WRCS were clarified. It was shown that during breathing of atmospheric air, the blood saturation level, lung ventilation indicators, and hemodynamics did not differ significantly between women exposed to WRCS and those not exposed to it. However, during a controlled hypoxic test (breathing a gas mixture with 12% oxygen for 20 min), women experiencing WRCS experienced a more significant decrease in blood saturation, indicating a lower tolerance to hypoxia. This is also evidenced by a reduced lung ventilation response to controlled hypoxia in the WRCS group, where the increase in ventilation primarily occurred due to an elevation in breathing rate rather than tidal volume. At the same time, the hemodynamic response to hypoxia in women with WRCS was characterized by a more substantial increase in heart rate and systolic arterial pressure. Thus, it was established that in women who were in the state of HCV, the body’s resistance to the effects of hypoxia decreases. At the same time, in conditions of hypoxia, the nature of their breathing changes, and the compensatory growth of pulmonary ventilation decreases, but the growth of hemodynamic indicators increases.

Abstract 12116: Identifying the Underlying Causes of Unexplained Dyspnea at High Altitude Using Normobaric Hypoxia With Transthoracic Echocardiography

Introduction: Exposure to high altitude results in hypobaric hypoxia, leading to physiological changes in the cardiovascular system that may result in dyspnea. Hypoxic simulation testing (HSTs) simulates changes in physiology that occur at a specific altitude. Hypothesis: The use of transthoracic echocardiography (TTE) during HST can detect the raise in right-sided pressures revealing underlying causes of high-altitude dyspnea. Methods: We performed a prospective observational study of consecutive patients with unexplained dyspnea at high altitude who were referred to an aerospace medicine program at a single institution between August 2021 and March 2023. Reduced FiO 2 was administered for 20 minutes to simulate altitude levels specific to patients’ history. TTE images were obtained at baseline and during peak hypoxia to evaluate right ventricular (RV) function, RV systolic pressure, and any possible shunts. Result: The study included 27 patients, with a mean age of 64.7 ±14.4 years and 14 (51.9%) females. No significant abnormalities were seen on baseline TTE and no significant differences in blood pressure and heart rate between baseline and hypoxia simulation were detected. Notably, RV systolic pressure increased at peak hypoxia, while RV systolic function declined as shown by a decrease in S’ wave and TAPSE ( Figure 1 ). Additionally, right to left shunts were present in 19 (70.4%) patients. Of these, four patients (21.1%) had shunts present at baseline with no changes at peak hypoxia, while the severity of shunts increased at peak hypoxia in eight cases (42.1%) and the shunts were only evident during hypoxia in seven patients (36.8%). Conclusion: TTE during HST provides valuable information by revealing the presence of symptomatic, sustained shunts and confirming the decline in RV hemodynamics explaining dyspnea at altitude. Further studies are necessary to establish the optimal clinical role of this physiologic method.

'It gives me more freedom': Family perspectives on travelling with children on nocturnal ventilation.

Children with neuromuscular weakness or central hypoventilation often require nocturnal ventilation. Children with these conditions are living longer and the numbers of children affected are increasing. The challenges associated with managing ventilation at home have been documented; however, there has been limited investigation into accessing wider experiences such as travel. Air travel, in particular, may be considered challenging for children with these conditions because oxygen levels are lower in airplane cabins than at sea levels. We sought to understand experiences of and attitudes towards travel amongst families of children using nocturnal ventilation for neuromuscular weakness or central hypoventilation. Two semi-structured interviews were conducted amongst participants enrolled in a trial of a new pre-flight assessment of their tolerance of reduced oxygen levels during flight (known as a hypoxic challenge test). Children participating in the trial were aged 19 months to 18 years. Parents were interviewed and provided proxy views for younger children, and older children were encouraged to present their own views during these interviews. One interview was conducted immediately after the assessment, and a second 3 months later. Data were analysed utilising the framework approach to thematic analysis. Seventeen families participated in the first interview with 14 of these families completing the follow-up interview. Three further families participated in the follow-up interview only. Here, we report three themes relating to participant experience of travel and how this is impacted by their condition. The three themes and their sub-themes were (1) insight into children's lives: hospital attendances, gaining knowledge and confidence, and child as a person; (2) travelling with your child: planes, trains and automobiles, rules of air travel, and uncertainty; and (3) the meaning of travel: normalisation, connection to extended family, expanded experiences, and freedom and equality. This population of children and their families aspire to travel but face challenges from clinical and social barriers. It is essential that we further our understanding of the physiological, social and cultural aspects of their experience to facilitate their access to broadened life experiences.

On the Relationship of Natural and Modified Radioresistance with Mast Cell Reactivity

This study was caused by accumulation of the data concerning: 1) relationship between the general reactivity of the body and radioresistance; 2) essential role of mast cells in the formation of radiobiological effects; 3) significant individual features of body radioresistance. Purpose of the study was to identify the relationship of radioresistance indicators with the state of body reactivity, manifested by constitutionally determined features of connective tissue mast cells. Natural radioresistance and modifying effect of hypoxia, hyperoxia and indralin radioprotector were considered. The study was performed on 369 white male rats weighing 215–240 g. To determine the individual characteristics of radioresistance, total and cranio-caudal irradiation of animals was performed. As a hypoxic test, hypoxic gas mixture with 8% oxygen content was used. The criteria of radioresistance were 5- and 30-day survival, weight loss, early transient disability. Index of reactivity of skin mast cells was considered as the diagnostic sign. Relationship features between the level of mast cell reactivity and radioresistance indicators were revealed. It has been shown that the minimum level of natural radioresistance is typical for animals with a high index of mast cell response to hypoxia. The modifying effect of hypoxia during irradiation was manifested in all animals. Also, the highest level of modified radioresistance was observed in rats with average values of the mast cell reactivity index. At the same time, When indralin was used, its radioprotective effect was most pronounced in the group of animals with the maximum reaction of mast cells. The radiomodifying effect of oxygen is mostly expressed in rats with the maximum values of the mast cell reactivity index and is characterized by a decrease in 5-day survival and average life expectancy. The relationship between the characteristics of mast cells and radioresistance can serve as a basis for the development of methods for predicting individual natural and modified radioresistance.

Relationships between neuro-endocrine, electrocardiogram, and gastric mucosal damage parameters in naїve and stressed rats

Introduction The first scientific publication on general adaption syndrome, or as we know today biologic stress has been published in Nature in 1936 by the 29-year old Hans Selye.1 Szabo et al2 in the anniversary review "Stress" is 80 Years Old” conclude that despite the extensive and multidisciplinary research on stress during the last 80 years, a lot of basic and clinical research is needed to better understand the manifestations, central and peripheral molecular regulators of stress response, especially the modes of prevention/management of distress or its transformation into eustress and the treatment of stress-related diseases. In the vast majority of publications on stress, the HPA-, HPG- and autonomous systems are the objects of research, while the place in the general adaptation syndrome of such important hormones as calcitonin and PTH has been studied only in a few publications. Another methodological shortcoming of most studies is that the subjects of analysis are limited to a single neuro-endocrine system. Therefore, we set ourselves the goal: to analyze relationships between some adaptation hormones, HRV, calcitonin, and PTH as well as electrocardiogram and gastric mucosal damage in naїve and post stressed rats. Material and methods Ethics approval All animals were kept in room having temperature 22±2ºC, and relative humidity of 44-55% under 12/12 hours light and dark cycle with standard laboratory diet and water given ad libitum. Studies have been conducted in accordance with the rules and requirements of the “General Principles for the Work on Animals” approved by the I National Congress on Bioethics (Kyїv, Ukraine, 2001) and agreed with the provisions of the “European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes” (Council of Europe No 123, Strasbourg 1985), and the Law of Ukraine “On the Protection of Animals from Cruelty” of 26.02.2006. The removal of animals from the experiment was carried out under light inhalation (ether) anesthesia by decapitation. Participants The experiment is at 38 rats Wistar line: 18 males (Weight Mean=227 g; SD=25 g) and 20 females (Mean=214 g; SD=27 g). Study design and procedure Due to the purposeful formation of groups, the potential predictors of post-stress reactions of the neuro-endocrine-immune complex and the metabolome3,4,5 were almost identical both in mean values and, to a lesser extent, in variance (SD). In particular, the hypoxic test (sec) was: 136±59 and 133±81; swimming test (min): 19±11 and 19±17; HRV Stress index4 (units) as (AMo/2*Mo*MxDMn)1/3: 0,14±0,08 and 0,14±0,05 in intact animals and those exposed to acute stress. Results and discussion Adhering to the algorithm of the Truskavetsian Scientific School of Balneology, we recalculated the current values of the parameters in Z-scores. This approach makes it possible to adequately compare deviations from the norm of parameters expressed in different units and with different variability.10,11,12 This is all the more important in view of sexual dimorphism in endocrine parameters. In addition to drastically higher levels of testosterone (41.8±1.7 vs 3.53±0.24 nM/L), males have higher levels of calcitonin (36±6 vs 21±4 ng/L), but lower levels of parathyroid hormone (154±12 vs 185±3 ng/L), adrenals mass (44±5 vs 65±5 mg), corticosterone (340±45 vs 466±57 nM/L), and aldosterone (587±8 vs 639±24 pM/L). Conclusion The condition of the gastric mucosa and myocardium as essential targets of stressors is determined by the damaging and protective effects of adaptive hormones and the autonomic nervous system.

Fitness to fly for children and adolescents after Fontan palliation.

At cruising altitude, the cabin pressure of passenger aircraft needs to be adjusted and, therefore, the oxygen content is equivalent to ambient air at 2,500 masl, causing mild desaturation and a rising pulmonary vascular resistance (PVR) in healthy subjects. For Fontan patients with passive pulmonary perfusion, a rising PVR can cause serious medical problems. The purpose of this fitness to fly investigation (FTF) is to assess the risk of air travel for children and adolescents after Fontan palliation. We investigated 21 Fontan patients [3-14y] in a normobaric hypoxic chamber at a simulated altitude of 2,500 m for 3 h. Oxygen saturation, heart rate, and regional tissue saturation in the forehead (NIRS) were measured continuously. Before entering the chamber, after 90 and 180 min in the hypoxic environment, blood gas analysis and echocardiography were performed. Heart rate and blood pressure did not show significant intraindividual changes. Capillary oxygen saturation (SaO2) decreased significantly after 90 min by a mean of 5.6 ± 2.87% without further decline. Lactate, pH, base excess, and tissue saturation in the frontal brain did not reach any critical values. In the case of open fenestration between the tunnel and the atrium delta, P did not increase, indicating stable pulmonary artery pressure. All 21 children finished the investigation successfully without any adverse events, so flying short distance seems to be safe for most Fontan patients with good current health status. As the baseline oxygen saturation does not allow prediction of the maximum extent of desaturation and adaption to a hypoxic environment takes up to 180 min, the so-called hypoxic challenge test is not sufficient for these patients. Performing an FTF examination over a period of 180 min allows for risk assessment and provides safety to the patients and their families, as well as the airline companies.

The features of reactions to acute stress of neuro-endocrine-immune complex, metabolome, ECG and gastric mucosa in rats with various state of innate muscular endurance and resistance to hypoxia

Background. It is known about wide variety of individual reactions to stress explained by genetics factors. On the other hand, it is also known about aerobic fitness variability between individuals. From the above it follows the hypothesis that inter-individual differences in normal conditions determine the characteristics of the body's response to acute stress. The purpose of this study is to test the hypothesis. Material and methods. The experiment is at 58 rats (28 males) Wistar line. Animals were tested for resistance to hypoxic hypoxia and aerobic muscular performance by swimming test. On the basis of the received data two qualitatively equivalent groups in a ratio 10/48 were formed. After a week of recovery over the next 10 days, one animal remained intact and 5 other rats were exposed to water-immersion and restraint stress. The next day after stress, the ECG recorded and some endocrine, metabolic and immune parameters determined as well as erosive-ulcerative lesions of the gastric mucosa evaluated. Results. Four clusters by hypoxic and swimming tests were created retrospectively: normal resistance to hypoxia and muscular endurance (n=11); moderately reduced resistance to hypoxia and normal swimming test (n=25); drastic increased swimming test and normal hypoxic test (n=3); significantly increased resistance to hypoxia and normal swimming test (n=9). Each cluster is characterized by specific (correctness of classification 100%) post-stress changes in 6 neuro-endocrine, 12 immune, 10 metabolic and 2 ECGs parameters, as well as the index of damage to the gastric mucosa. The swimming test determines the post-stress state of the registered parameters by 63,8%, the hypoxic test - by 57,5%, and taken together - by 79,1%. Conclusion. The post-stress neuro-endocrine, immune and metabolic parameters as well as injuries of myocardium and gastric mucosa in rats are determined significantly by innate muscular endurance and resistance to hypoxia.

Clinical features and health-threatening conditions of the trek to Capanna Margherita.

Since trips to high altitude have become popular, reports on clinical and environmental characteristics during expeditions to popular destinations are needed. A group of 15 healthy adults was monitored during a trek to Capanna Margherita (4556 m). A hypoxic stress test was applied before the expedition started. Environmental characteristics were acquired with a portable device. Vital signs were compared at low and high altitude, and altitude sickness was diagnosed by the Lake Louise scoring system. Ocular symptoms and intraocular pressure were recorded. Temperature ranged from -3.5 to 31.3 °C and relative humidity from 36 to 95% during the trek. Acute mountain sickness was diagnosed in 40% of participants, more frequently in women, and slightly associated with a greater drop in SpO<inf>2</inf>. Heart rate and blood pressure increased, while peripheral saturation and intraocular pressure decreased, in response to altitude hypoxia. Rapid ascents, as in the most common expedition plans, should be carefully supervised because of the common occurrence of AMS, especially in women. Among organ districts, the eye should deserve more attention in high-altitude medicine. Analyses of environmental conditions, together with predictive methods and early identification of health-threatening conditions, are of great value in supporting further recreational, professional and scientific expeditions to the most intriguing altitude sites.

Resistance to the action of flight work factors of vietnamese pilots operating russian aviation equipment

This study analyzed the tolerability of factors of flight work by Vietnamese pilots. The effects of aerobatic overloads (statoergometry), hypoxia (hypoxic test), and statokinetic loads (Otolith reaction-10 test) were simulated. To assess the functional state, computer stabilography and psychophysiological techniques were used to determine the reaction of choice and the critical frequency of light flashes. Height, bodyweight, blood pressure, heart rate, and blood oxygen saturation were recorded. In this study, 17 Vietnamese (group 1) and 24 Russian (group 2) pilots aged 1922 years were examined. Significant differences in height and bodyweight were found between the groups, which affected the tolerance of static muscle loads. Only 12% of the Vietnamese pilots completed the statoergometric test, and only one of the Russian ones did not reach the fifth stage. The conducted tests did not significantly affect the psychophysiological indicators, although they had multidirectional changes. Thus, when performing a normobaric hypoxic test, the blood pressure, heart rate, and blood oxygen saturation at the 5th minute of the recovery period returned to their original values. A slight increase in the pulse rate did not reach statistical significance. In general, the tolerance for normobaric hypoxia in both groups was good. However, a significantly smaller area of displacement of the pressure center of the statokinesiogram indicated a greater strain of adaptation mechanisms in group 1 than in group 2. The reaction to the statokinetic effect also indicated a satisfactory tolerance of the vestibular test Otolith reaction-10. Moreover, the tension of adaptive mechanisms in group 1, in contrast to group 2, was more pronounced. In addition, changes in the indicators of computer stabilography suggest a greater strain of adaptive mechanisms in Vietnamese pilots than in Russian pilots. The results indicate the need to develop methods of preparation for flights with aerobatic overloads and a system of psychophysiological training of pilots of the Socialist Republic of Vietnam to increase resistance to the influence of professional factors of flight work and the successful operation of Russian aviation equipment.

The role of modern and promising methods of diagnostics of functional ventilation disorders in pulmonological patients

The current problems of the application of existing and promising methods for assessing respiratory function in a modern pulmonological hospital are considered. Determining the degree of respiratory disorders is key both in the period of exacerbation of chronic bronchopulmonary diseases and intercommunal and/or rehabilitation period and identifies the tactics and scope of therapeutic measures. There is a wide variety of hardware methods for assessing respiratory function: body plethysmography, volumetric capnography, computer pulse oximetry monitoring, ergospirometry, impulse oscillometry, etc. Most of them are non-invasive, for some standardized stress tests with physical, drug, and other load options. Each of the methods for assessing ventilation disorders has its advantages and disadvantages; therefore, it is common to search for new or refine existing approaches in assessing respiratory function. The entire arsenal of functional tests should be considered in the form of an integrated approach in examining patients, based on the clinical situation, with the choice of optimal, most informative methods. A novel and promising method is stress hypoxic testing based on the principle of feedback, which allows the assessment of the reaction of the body of a pulmonological patient to hypoxic stress to avoid the risks of emergency conditions without loss of informative results. The prospect of further growth in the information content and quality of the obtained data of functional respiratory tests is the introduction into research on the principles of biofeedback and automated evaluation of the data provided to the researcher and the attending physician.