Is there a competition for oxygen availability between respiratory and limb muscles?

If a competition between the oxygen demands of limb and respiratory muscles happens, hypoxia may favor redistribution of blood flow from peripheral to respiratory muscles during heavy exercise. This hypothesis was tested in eighteen lowlanders and 27 highlanders at 4350m altitude. During an incremental exercise, the regional tissue oxygen saturation (rSO2) and tissue hemoglobin concentration ([Hbt]) of the intercostal muscles and vastus medialis were monitored simultaneously by NIRS. The intercostal and vastus medialis rSO2 values were lower at altitude than at sea level (-10%, p<0.001) and decreased similarly during incremental exercise (p<0.001) while [Hbt] values increased. At maximal exercise, the intercostal rSO2 was lower than the vastus medialis rSO2 in lowlanders (-7%, p<0.001). In highlanders the time patterns were similar but intercostal rSO2 was less decreased at exercise (p<0.05). Maximal exercise performed in hypoxia did not alter the kinetics of rSO2 and [Hbt] in peripheral muscles. These findings do not favor the hypothesis of blood flow redistribution.

Expiratory flow limitation and obstruction in the elderly.

Elderly people commonly suffer from dyspnoea, which may stem from expiratory flow limitation (EFL). The relationship between EFL, as assessed by the negative expiratory pressure method and spirometric indices, was investigated in an elderly French population. Subjects, aged 66-88 yrs, filled in socio-demographic and standardised questionnaires, which dealt with: medical history, smoking status and respiratory symptoms. EFL measurements and forced expiratory manoeuvres were performed. Validated measurements were obtained in 750 out of 1,318 subjects: 47% were EFL+ (EFL >0), with a higher prevalence in females than in males. EFL and forced expiratory volume in one second (FEV1) were correlated with age. A total of 116, from the 750 subjects, with no medical history and no symptoms, served as a healthy group. The prevalence of EFL+ subjects increased with the grade of dyspnoea and was highest in respiratory and cardiac patients when compared with the healthy subjects. EFL did not correlate with FEV1/forced vital capacity (FVC), the usual index of obstruction. Some elderly subjects (15%) with dyspnoea but with no medical history, mainly females with small FVC and normal FEV1/FVC, had a greater EFL than the healthy subjects. In elderly people, expiratory flow limitation measurements, along with the usual forced expiratory volume in one second/ forced vital capacity ratio, may be of value for the interpretation of dyspnoea.

Airway tone during exercise in healthy subjects: effects of salbutamol and ipratropium bromide.

In healthy subjects changes in airway calibre during exercise are conflicting and smaller than in asthmatics. Methodological differences could explain the discrepancies between the results obtained in healthy subjects. Therefore, our aim was to assess during exercise the changes in airway diameter and the effects of 200 microg salbutamol (SAL) or 40 microg ipratropium bromide (IPR) inhalations versus placebo (PLA), using spirometry and respiratory resistance (Rrs). Eight non-asthmatic subjects exercised 9 min at 70 % of their maximal aerobic power after inhalation of 200 microg SAL, 40 microg IPR, or PLA. Maximal flow-volume curves were obtained before and after inhalations, at 3 (E3) and 6 (E6) minutes of exercise, and during recovery. Rrs were measured by impulse oscillometry before and after inhalation, and immediately at the end of exercise. At rest, FEV (1) increased significantly after inhalation of SAL and IPR. Rrs decreased only after SAL. During exercise FEV (1) increased significantly from rest with SAL and IPR while forced mid expiratory flow (FEF (25 - 75)) increased significantly for all conditions. At E6 the rise of FEV (1) and FEF (25 - 75) were greater with SAL compared to PLA and IPR. In all conditions Rrs increased significantly immediately at the end of exercise as compared to rest but less than during flow-matched hyperpnea. It is concluded that a similar bronchodilation was observed during exercise with and without anticholinergic drug which suggests a withdrawal of parasympathetic control of airways during exercise in healthy subjects. Nevertheless, the bronchodilation observed during exercise is not maximal since it can be reinforced by beta (2)-mimetic drug.

Reduction of exercise-induced asthma in children by short, repeated warm ups.

AIM: To study the effect of a warm up schedule on exercise-induced asthma in asthmatic children to enable them to engage in asthmogenic activities. METHOD: In the first study, peak flows during and after three short, repeated warm up schedules (SRWU 1, 2, and 3), identical in form but differing in intensity, were compared in 16 asthmatic children. In the second study the efficiency of the best of these SRWU schedules was tested on 30 young asthmatic children. Children performed on different days a 7 minute run alone (EX1) or the same run after an SRWU (EX2). RESULTS: The second study showed that for most children (24/30) the fall in peak flow after EX2 was less than that after EX1. The percentage fall in peak flow after EX2 was significantly correlated with the percentage change in peak flow induced by SRWU2 (r = 0.68). The children were divided into three subgroups according to the change in peak flow after SRWU2: (G1: increase in peak flow; G2: < 15% fall in peak flow; G3: > 15% fall in peak flow). Only the children in the G3 subgroup did not show any gain in peak flow after EX2 compared with EX1. CONCLUSION: The alteration in peak flow at the end of the SRWU period was a good predictor of the occurrence of bronchoconstriction after EX2. An SRWU reduced the decrease in peak flow for most of the children (24/30) in this series, thus reducing subsequent post-exercise deep bronchoconstriction.