Hypercapnia during maximal exercise in patients with chronic airflow obstruction.

The pattern of breathing during maximal oxygen uptake (Vo2max) was studied in 26 patients with chronic airflow obstruction (CAO), in whom the vital capacity (VC), forced expiratory volume in 1 s (FEV1) and residual volume (RV) were measured. The patients performed, on a cycle ergometer, in a sitting position, a submaximal (A) and a maximal (B) exercise in a single session during which three arterial blood samples (pH, PaCO2, PaO2, lactate) were taken: the first at rest, the second at the 10th min of steady-state 40 W exercise, and the third at maximal VO2. VE, VCO2, VO2, respiratory rate (RR) and VT were measured with an open circuit. Physiological dead space (VD) and alveolar to arterial O2 pressure differences (A-aPO2) were computed. According to the measured value of PaCO2 at maximal exercise, the patients were divided in non-hypercapnic (NH; PaCO2 less than 44 mmHg; n = 17) and hypercapnic (H; PaCO2 greater than 44 mmHg; n = 9) groups, and were compared with a group of normal subjects (N; n = 11). At rest, VC, FEV1, FEV1/VC ratio, TLC and PaO2 were more decreased in H than in NH patients. However, RV, VE, RR and VT did not differ between H and NH patients. PaCO2 at rest was comparable in N and H subjects but was significantly lower in NH patients. During B exercise, VE, VO2 and PaO2 were lower in H patients. With both A and B exercises, the H patients showed a lower VT and VT/VC ratio with a higher VD/VT ratio, while A-aPO2 were the same in NH and H patients.(ABSTRACT TRUNCATED AT 250 WORDS)

[The place of the chest radiograph in estimating total lung capacity (author's transl)]. / Place de la radiographie thoracique dans l'estimation de la capacité pulmonaire totale.

The determination of total lung capacity (TLC) by either the plethysmographic (pleth) or closed-circuit foreign gas (dil) method requires expensive and sophisticated equipment. Since hospitals usually have the facilities to perform chest roentgenograms, we wanted to ascertain if the radiologic method (rad) of BARNHARD et al. [1] could be used in lieu of the more sophisticated methods. Sixty-two men ranging from 21 to 67 years had TLC determined by the plethysmographic method, the closed-circuit foreign gas method in which rebreathing was continued until helium was uniformly distributed throughout the lungs, and the radiologic method. There were 21 normal men, 30 with a clinical diagnosis of chronic bronchitis and 11 with a radiologic diagnosis of emphysema plus chronic bronchitis. The mean value of TLC in the normal men showed no significant differences between the three methods and an excellent correlation between the pleth-rad and dil-rad. In the men with chronic bronchitis, there were no significant differences between the mean TLC of rad (7.166 +/- 1.217 1) and dil (6.704 +/- 1.067 1) of rad and pleth (7.545 +/- 1.165 1). The correlations (p < 0.001) were: dil-rad (r = 0.78) and pleth-rad (r = 0.77). In the men with emphysema, there were also no significant differences between the mean TLC of rad (7.166 +/- 1.217 1) and dil (6.704 +/- 1.067 1) or rad and pleth (7.545 +/- 1.165 1). The correlations (p < 0.001) were: dil-rad (r = 0.78) and pleth-rad (r = 0.77). In the men with emphysema, there were also no significant differences between the mean TLC of rad (8.789 +/- 1.207 1) and dil (7.831 +/- 1.041 1) or rad and pleth (9.403 +/- 1.735 1). The correlations were: dil-rad (r = 0.81, p < 0.01) and pleth-rad (r = 0.91, p < 0.001). This study suggests that in normal individuals and patients with chronic bronchitis or emphysema the radiographic method is a useful and reliable technique for determining TLC when elaborate equipment for measuring lung volumes is not available.