Dominique Choquet

Effects of obesity on breathing pattern, ventilatory neural drive and mechanics

The purpose of this study was to assess whether obesity induces changes in breathing pattern and ventilatory neural drive and mechanics. Measurements performed in 34 male obese subjects (BMI, 39+/-6 kg/m(2)) and 18 controls (BMI, 23+/-3 kg/m(2)) included anthropometric parameters, spirometry, breathing patterns, mouth occlusion pressure, maximal inspiratory pressure and work of breathing. The results show that spirometric flow (FEV(1)% pred, FVC% pred) and maximal inspiratory pressure (P(Imax)) were significantly lowers (p<0.001) in obese subjects compared to controls. The (fR/VT) ratio was higher in obese subjects than in controls (p<0.001). The increase in (fR/VT) was associated with an increase in the ratio of mean inspiratory pressure to maximal inspiratory pressure (P(I)/P(Imax)) and the duty cycle (T(I)/T(TOT)) (p<0.001). The energy cost of breathing (W(rest)/W(crit)), which reflects the oxygen consumed by the respiratory muscle was greater in obese subject than in controls (p<0.001) inducing an increase in the effective inspiratory impedance on the respiratory muscles. It is concluded that obese subjects show impairment in breathing pattern and respiratory mechanics as assessed by rapid shallow breathing leading to ventilatory failure.

Effects of interval training at the ventilatory threshold on clinical and cardiorespiratory responses in elderly humans

Abstract This study assessed clinical and cardiorespiratory responses after an interval training programme in sedentary elderly adults using the ventilatory threshold (Vth) as the index of exercise training intensity. A selection of 22 subjects were randomized into two groups: 11 subjects served as the training group (TG) and the others as controls (CG). Maximal exercise tests were performed on a treadmill before (T0), each month (T1, T2) and after the 3-month interval training programme period (T3). The TG subjects were individually trained at the heart rate corresponding to Vth measured at T0, T1 and T2 as the breakpoint in the oxygen uptake-carbon dioxide production relationship. Their training programme consisted of walking/jogging sessions on a running track twice a week. The sessions consisted of varying durations of exercise alternating with active recovery in such a way that the subjects slowly increased their total exercise time from an initial duration of 30 min to a final duration of 1 h. During training the heart rate was continuously monitored by a cardiofrequency meter. Compared with the daily activities of the controls, no training programme-related injuries were observed in TG. Moreover, programme adherence (73%) and attendance (97.3%) were high. The maximal oxygen uptake and Vth were increased in TG, by 20% (P<0.05) and 26% (P<0.01), respectively. Interval training at Vth also significantly increased maximal O2 pulse (P<0.05) and maximal ventilation (P<0.01). A significant decrease in submaximal ventilation (P<0.05) and heart rate (P<0.01) was also noted. These results would suggest that for untrained elderly adults, an interval training programme at the intensity of Vth may be well-tolerated clinically and may significantly improve both maximal aerobic power and submaximal exercise tolerance.

Cardiorespiratory fitness and functional capacity assessed by the 20-meter shuttle walking test in patients with coronary artery disease.

OBJECTIVE To validate the 20-meter shuttle walking test (20MST) in the assessment of maximal oxygen consumption (VO(2)max) and maximal speed in patients with coronary artery disease (CAD). DESIGN Single-sample validity study. SETTING Cardiac rehabilitation service in France. PARTICIPANTS Seventeen men with CAD. INTERVENTIONS Subjects underwent a symptom-limited treadmill test (SLTT) in a laboratory, with a speed starting at 2.5km/h and increasing by 0.5km/h every minute, and performed an adapted 20MST in a corridor, with a speed starting at 3km/h and increasing by 1km/h every minute until exhaustion. MAIN OUTCOME MEASURES VO(2) measured during the 20MST with the Cosmed K2 telemetric gas analyzer (K2 VO(2)), estimated VO(2) calculated by the Léger equation (Léger VO(2)) from the maximal speed obtained during the 20MST, and VO(2) measured during the SLTT (SLTT VO(2)). Maximal speeds attained on the treadmill and on the 20MST were also compared. RESULTS A significant (P<.0001) difference was observed between the Léger estimate of VO(2) and those of K2 VO(2) and SLTT VO(2) (mean +/- standard deviation, 12.28+/-5.90mL. min(-1).kg(-1) vs 23.04+/-7.17 and 22.56+/-6.29mL.min(-1).kg(-1)). No difference was found between the treadmill and the 20MST maximal speeds (6.73+/-0.91km/h, 6.78+/-1.23km/h, respectively). Measured with the Cosmed K2, a significant relationship existed between VO(2) and each speed level (r=.95, P<.0001; VO(2)=4.24x speed-7.37, standard estimation error=2.29mL.min(-1).kg(-1)). CONCLUSION Maximal VO(2) and maximal speed measured on the treadmill did not differ significantly from those obtained on the 20MST. The current 20MST equation (Léger equation) was not valid to estimate VO(2) in CAD patients. A modified prediction equation of VO(2) was given and would need a larger number of patients to be generalized.

Is there a beneficial effect difference between age, gender, and different cardiac pathology groups of exercise training at ventilatory threshold in cardiac patients?

BACKGROUND Research on cardiac rehabilitation has raised interesting methods and effects without however establishing the share of the profits according to age, sex and cardiac pathology. Yet today, this disease with various pathologies strikes people of all ages and both sexes, and the recommended rehabilitation exercise intensity is often the ventilatory threshold. The aim of this study was to compare benefits of a training program at ventilatory threshold according to age, gender and cardiac pathology. METHODS One hundred and eighty eight cardiac patients, of whom 62 had coronary artery bypass surgery, 22 artery angioplasty, 54 myocardial infarction and 50 valve replacements, aged 31-82 years, performed spirometric and cardiopulmonary exercise tests before and after a training program. This program consisted of exercise on a cycloergometer for three sessions of 45 min per week for eight weeks at heart rates attenuated at ventilatory threshold (V(Th)) obtained during a cardiopulmonary exercise test conducted before the training period. RESULTS Peak heart rate, peak aerobic power, and peak oxygen uptake determined at V(Th) increased during the training period in all groups of subjects. Men and adult groups had higher absolute values compared to women and elderly groups. No difference was observed in cardiac pathology groups. Similar improvements of aerobic capacities were observed in age, gender and cardiac pathology groups. CONCLUSIONS A training program conducted at personalised V(Th) significantly improves the aerobic physical capacities of all cardiac patients, and inducessimilar benefits whatever the age, gender or cardiac pathology.

Advanced Mechanical Ventilatory Constraints During Incremental Exercise in Class III Obese Male Subjects

BACKGROUND: We investigated the role of mechanical ventilatory constraints in obese class III subjects during incremental exercise. METHODS: We examined 14 control subjects (body mass index [BMI], 23.6 ± 3.2 kg/m2), 15 obese class II subjects (BMI, 37.2 ± 4.5 kg/m2), and 17 obese class III subjects (BMI, 53.4 ± 6.8 kg/m2). All subjects performed pulmonary function tests and maximal inspiratory pressure at rest, ventilatory parameters, flow-volume loops, and rated perceived exertion and breathlessness during exercise. RESULTS: All subjects had normal pulmonary function. Obesity resulted in increased minute ventilation for a given submaximal work rate, although minute ventilation during peak exercise was lowest in the obese class III subjects. End-expiratory lung volume was significantly lower in the obese subjects at rest and during exercise at the ventilatory threshold but not during peak exercise. During heavy-to-peak exercise, the obese subjects increased their end-expiratory lung volume, whereas the control group continued to decrease this parameter. Compared with controls, end-inspiratory lung volume was significantly lower in obese class II subjects and obese class III subjects at rest and at the ventilatory threshold but not during peak exercise. At maximal exercise, obese class III subjects had a greater end-inspiratory lung volume than obese class II subjects and controls. Obese class III subjects displayed a greater expiratory air flow limitation at rest, at the ventilatory threshold, and during peak exercise than both controls and obese class II subjects. CONCLUSIONS: Mechanical ventilatory constraints increase progressively with degrees of obesity, contributing to exercise limitation in obese subjects.

Inspiratory muscle performance in endurance-trained elderly males during incremental exercise.

The aim of this study was to compare the inspiratory muscle performance during an incremental exercise of twelve fit old endurance-trained athletes (OT) with that of fit young athletes (YT) and healthy age-matched controls (OC). The tension-time index (TT0.1) was determined according to the equation TT0.1=P0.1/PImax×ti/ttot, where P0.1 is the mouth occlusion pressure, PImax the maximal inspiratory pressure and ti/ttot the duty cycle. For a given VCO2, OT group displayed P0.1, P0.1/PImax ratio, TT0.1 and effective impedance of the respiratory muscle values which were lower than OC group and higher than YT group. At maximal exercise, P0.1/PImax ratio and TT0.1 was still lower in the OT group than OC group and higher than YT group. This study showed lower inspiratory muscle performance attested by a higher (TT0.1) during exercise in the OT group than YT group, but appeared to be less marked in elderly men having performed lifelong endurance training compared with sedentary elderly subjects.