Jean Paul Richalet

Swimmers can train in hypoxia at sea level through voluntary hypoventilation.

This study used an innovative technique of pulse oximetry to investigate whether swimmers can train under hypoxic conditions through voluntary hypoventilation (VH). Ten trained subjects performed a front crawl swimming series with normal breathing (NB), VH at high (VHhigh) and low pulmonary volume (VHlow). Arterial oxygen saturation was continuously measured via pulse oximetry (SpO2) with a waterproofed forehead sensor. Gas exchanges were recorded continuously and lactate concentration ([La]) was assessed at the end of each test. In VHlow, SpO2 fell down to 87% at the end of the series whereas it remained above 94% in VHhigh during most part of the series. Ventilation, oxygen uptake and end-tidal O2 pressure were lower in both VHhigh and VHlow than in NB. Compared to NB, [La] significantly increased in VHlow and decreased in VHhigh. This study demonstrated that swimmers can train under hypoxic conditions at sea level and can accentuate the glycolytic stimulus of their training if they perform VH at low but not high pulmonary volume.

Factors affecting the development of lung function in Tunisian children.

We undertook to evaluate the impacts of morphology at birth, physical activity, anthropometric, socioeconomic and environmental factors on lung function in healthy Tunisian children. Pulmonary function parameters were measured with a Minato portable spirometer in a randomized population of 756 healthy children (388 males and 368 females) aged between 6 and 16. The morphology at birth, the gestational age, the physical activity, the socioeconomic status, the type of habitation, and the environmental factors were all assessed by a standard questionnaire. Using univariate analysis, we found that: (1) morphometric parameters (height, weight, maximal inspiratory, and expiratory perimeter), as well as sex were highly associated with pulmonary function parameters; (2) Height at birth showed strong significant relations with FVC, FEV1, and FEV1/FVC; (3) lung function parameters were influenced by physical training of our children, socioeconomic status, indoor pollution, and passive smoking; and (4) we did not observe any association between the gestational age and the weight at their birth and lung function parameters. Using a general linear model analysis, morphometric parameters, age, sex, type of heating, and maximal inspiratory and expiratory perimeters had significant relation with respiratory parameters. In our population of healthy Tunisian children, the main predictive factors of the pulmonary development were the morphological factors such as height, weight, maximal inspiratory, and expiratory thoracic perimeter, sex and age, and the environmental conditions such as type of heating but not morphology at birth, physical activity, or socioeconomic status. Am. J.Hum. Biol., 2008.

Doppler study of middle cerebral artery blood flow velocity and cerebral autoregulation during a simulated ascent of Mount Everest

OBJECTIVEnTo explore cerebral hemodynamics in 8 healthy volunteers in a hypobaric chamber up to the altitude of Mount Everest after a progressive stepwise decompression to 8,848 m.nnnMETHODSnPhysiological, clinical, and transcranial Doppler data were collected after at least 3 days at 5,000, 6,000, and 7,000 m and within 4 hours of reaching 8,000 m and returning to sea level.nnnRESULTSnThree subjects were excluded at 8,000 and 8,848 m because of acute neurological deficits. Heart rate increased; mean arterial pressure remained stable; PaO2 and PaCO2 decreased with altitude; hemoglobin (Hb) and hematocrit (Ht) increased; arterial O2 content decreased over 6,000 m; middle cerebral artery blood flow velocity (MCAv) increased only during acute exposure to 8,000 m; and the corresponding pulsatility (PI) and resistivity indices (RI) decreased over 5,000 m. PI and RI correlated with heart rate. The transient hyperemic response (THR) of MCAv to common carotid compression was depressed at 8,000 m.nnnCONCLUSIONSnAt 8,000 m, the increase in MCAv seemed to reflect the normal hemodynamic response to acute hypoxia. The decrease of THR at this altitude could be an indication of impaired cerebral autoregulation. The role of impaired cerebral autoregulation in the genesis of acute neurologic deficits, observed at 8,000 m and above in 3 subjects, remains speculative.

Effect of acetazolamide on ventilatory response in subjects with chronic mountain sickness

Although the effects of acetazolamide (ACZ) on ventilation during acute mountain sickness are well known, there are no studies assessing its effect on ventilatory response in chronic hypoxia. We studied this effect in patients with chronic mountain sickness (CMS). Subjects with CMS, living permanently at 4300 m, were assigned in a randomized, double-blind study to 250 mg/day (n=9) or to 500 mg/day (n=9) of ACZ. Resting end-tidal PET(O2) and end-tidal PET(CO2) were measured before and after 3 weeks of acetazolamide. Ventilatory responses were evaluated by the determination of sensitivity to hypoxia and to CO2. After treatment ventilatory response to hypoxia increased, resting PET(CO2) decreased, and ACZ caused a leftward shift in the position, but not a change in the slope of the ventilation (VE) versus PET(CO2) relationship. There were no differences between the two doses used. ACZ administration provides a beneficial effect on respiratory function of high altitude natives with CMS and thus it can be an effective therapy for the disease.

Spirometric values in Tunisian children: relationship with pubertal status.

Background: Little is known about the effect of pubertal stages on lung function parameters in Tunisian children. Aim: The purpose of this study is to determine the relationship between lung function and pubertal stage in Tunisian children using anthropometric parameters. Subjects and methods: Pulmonary function parameters were measured with a Minato portable spirometer in 684 healthy Tunisian children (351 males and 333 females) aged between 8 and 16. The pubertal status was assessed for males and females according to the Tanner Method. Results: A large variation was observed in the distribution of childrens age and height by pubertal stages in both sexes. Height increased with age and pubertal stage in both males and females. The results also showed a significant increase in parameters of lung function (FVC, FEV1, PEF, MEF50 and MMEF25–75) with pubertal stage in Tunisian children. The analysis of covariance adjusting for anthropometric parameters showed that pubertal status had a significant independent effect on some pulmonary function parameters in both sexes. Conclusion: The results indicated that the parameters of pulmonary function for healthy Tunisian school children increased with age, height and pubertal stage. The present study has indicated that the use of only one morphological parameter such as height is not sufficient, but the pubertal status could be taken into account to standardize the lung function.

The relative contributions of anthropometric variables to vertical jumping ability and leg power in Tunisian children.

Aouichaoui, C, Trabelsi, Y, Bouhlel, E, Tabka, Z, Dogui, M, Richalet, JP, and Bouchez Buvry, A. The relative contributions of anthropometric variables to vertical jumping ability and leg power in Tunisian children. J Strength Cond Res 26(3): 777–788, 2012—The purpose of this study was to examine the relative contributions of anthropometric variables to vertical jumping ability and leg power and to establish reference values of vertical jumping parameters in athletic Tunisian children aged 7–13 years in both sexes. Three hundred and ninety-one athletic Tunisian children (208 boys and 183 girls) aged 7–13 years were randomly selected to participate in our study. They were asked to perform squat jumps and countermovement jumps. Jump heights and leg power were simultaneously provided by the optojump device. Full and stepwise regression models were calculated to identify which anthropometric parameters significantly contributed to performance variables. The multiple regressions showed that age, weight, standing height and fat-free mass were the predictors of jumping performance. The results may help in verifying the effectiveness of a specific training program and detecting highly talented athletes.

Oxygen modulates the glutathione peroxidase activity during the L6 myoblast early differentiation process.

Aim: This work aims to study the regulation of the glutathione peroxidase and catalase activities in myoblasts from the L6 line exposed to 21%, 5% and 1% O2 during the cell differentiation. Material and Methods: Rat L6 myoblasts were grown in 1%, 5% or 21% O2 in the presence or absence of N-acetyl cysteine. The cell proliferation was evaluated by determining the doubling time and kinetics of cultures by counting cells. The cell differentiation was analyzed by determining the myogenic fusion index using antibodies against the myosin heavy chain. The glutathione peroxidase and catalase activities were assayed. The p110-PI3K/Thr308-Akt pathway was studied using western blotting. The oxidative status of the cells was carried out by determining TBARS. Results: 5% O2 improves the glutathione peroxidase activity, p110-PI3K/Thr308-Akt pathway and differentiation while 1% O2 alters all these parameters compared to 21% O2. NAC (0.5 mM) can prevent the deleterious effects of hypoxia (1% O2) on the L6 myoblast proliferation and enhances the myoblast differentiation when exposed to 21% O2. TBARS are reduced in 5% O2 compared to both 21% and 1% O2. Conclusion: The glutathione peroxidase activity and p110-PI3K/Thr308-Akt are both modulated in the same way by oxygen.

'Oxygen uptake efficiency slope' in trained and untrained subjects exposed to hypoxia

We assessed the ability of the oxygen uptake efficiency slope, whether calculated on 100 and 80% of maximal exercise test duration (OUES(100) and OUES(80)), to identify the change in cardiorespiratory capacities in response to hypoxia in subjects with a broad range of V(O2 peak). Four maximal exercise tests were performed in trained (T) and untrained subjects (UT) in normoxia and at 1000, 2500 and 4500 m. The mean reductions in maximal exercise capacities at 4500 m were the same in T subjects for V(O2 peak) (-30%), OUES(80) (-26%) and OUES(100) (-26%) whereas in UT subjects only OUES(100) (-14%), but not OUES(80) (-20%), was lower compared with V(O2 peak) (-21%, p<0.05). OUES(100) and OUES(80) were correlated with V(O2 peak) and the ventilatory anaerobic threshold in both groups. Multiple regression analyses showed that V(O2 peak), OUES(100) and OUES(80) were significantly linked to O(2) arterial-venous difference. The OUES(80) could be considered as an interesting sub-maximal index of cardiorespiratory fitness in normal or hypoxemic subjects unable to reach V(O2 peak).

Periodic breathing and oxygen supplementation in Chilean miners at high altitude (4200m).

Our objective was to determine the nocturnal ventilatory pattern and characterize the effect of oxygen enrichment on nocturnal ventilatory pattern and sleep quality in miners exposed to intermittent hypobaric hypoxia at 4200m. A total of 16 acclimatized miners were studied. Nocturnal ventilatory pattern (plethysmographic inductance), arterial oxygen saturation and heart rate (pulse oximetry) were performed in 9/16 subjects. Sleep quality at high altitude was assessed by self-questionnaires in 16/16 subjects. All measurements were performed during at least 7h of sleep. Subjects were studied while sleeping at high altitude without (control, C) and with oxygen supplementation (FiO2=0.25, treated, T). Periodic breathing (%) C: 25±18 vs T: 6.6±5.6 (p<0.05), apneas index (no./h) C: 34.9±24.1 vs T: 8.5±6.8 (p<0.05); and sleep quality C: 17.8±3.4 vs T: 12.1±2.2 (p<0.0001) were evaluated. In conclusion, periodic breathing with apneas was present in miners exposed to high altitude for 1 to 4 years and was reduced by treatment with supplementary oxygen.

Effect of inositol hexaphosphate–loaded red blood cells (RBCs) on the rheology of sickle RBCs

BACKGROUND: The recent in vitro demonstration that inositol hexaphosphate–loaded red blood cells (IHP‐RBCs) may reduce the risks of sickling of sickle RBCs (SS RBCs) exposed to hypoxia make these modified RBCs potentially useful in transfused sickle cell anemia (SCA) patients.