The purposes of this investigation were to describe the changes in 1) dynamic compliance of the lungs, 2) airflow resistance, and 3) breathing pattern that occur during sleep in normal adult humans. Six subjects wore a tightly fitting face mask. Flow and volume were obtained from a pneumotachograph attached to the face mask. Transpulmonary pressure was calculated as the difference between esophageal pressure obtained with a balloon and mask pressure. At least 20 consecutive breaths were analyzed for dynamic compliance, airflow resistance, and breathing pattern during wakefulness, non-rapid-eye-movement stage 2 and rapid-eye-movement (REM) sleep. Dynamic compliance did not change significantly. Airflow resistance increased during sleep; resistance was 3.93 +/- 0.56 cmH2O X 1–1 X s during wakefulness, 7.96 +/- 0.95 in stage 2 sleep, and 8.66 +/- 1.43 in REM sleep (P less than 0.02). By placing a catheter in the retroepiglottic space and thus dividing the airway into upper and lower zones, we found the increase in resistance occurred almost entirely above the larynx. Decreases in tidal volume, minute ventilation, and mean inspiratory flow observed during sleep were not statistically significant.
Polynesian (Maori and Pacific Island) children account for approximately one quarter of the children in New Zealand, but good data for lung function in this group are not available. In this review, we report lung volume measurements in 571 healthy children 5 to 13 yr of age: 270 Polynesians (139 boys and 131 girls) and 301 Europeans (177 boys and 124 girls). All measurements were made in a body plethysmograph. Polynesian boys had significantly larger VC, FVC, FRC, TLC, and expiratory reserve volume than did Polynesian girls. Polynesian and European children generally showed different slope and intercept relationships for the prediction of lung volume from height. Racial differences are not adequately explained by differences in body proportions or social factors including parental smoking. Possible explanations include racial differences in lung growth and maturation.
1. Respiratory and circulatory functions of minimally clad human subjects were studied before and during acute exposure to ambient temperatures of 4.5-6.5 degrees C. 2. After 1 h of cold exposure, subjects showed increases of ventilation, O2 UPTAKE AND CARDIAC OUTPUT. Rectal temperatures fell. 3. During exercise in the cold conditions, oxygen uptake and cardiac output were greater than during the same exercise at normal temperature. 4. The increased cardiac output during cold exposure was achieved by an increase of stroke volume rather than heart rate; this finding is in contrast to changes during bicycle exercise and isometric exercise at normal ambient temperatures. 5. We conclude that the cardiorespiratory effects of cold exposure are not superseded by the response to moderate exercise. The difference between heart rate and stroke volume at increased levels of cardiac output during exercise at normal temperatures and during rest and exercise in cold conditions may be explained by changes of arterial baroreceptor input and of blood catecholamine levels.
We analyzed the accuracy of the inductance vest in measuring several ventilatory parameters in five patients with chronic obstructive pulmonary disease (COPD). We assessed tidal volume (VT) accuracy at different respiratory frequencies in different lying body positions with different thoracic and abdominal contributions to breathing and the accuracy over a 4-h time span. Mean percent error was calculated without regard to direction of error. The mean error of vest VT estimation was 7.6% for all body positions studied and 5.6% for right and left lateral positions combined. Vest VT accuracy was unchanged after 4 h and with changes in thoracic and abdominal contributions to VT. The mean errors for inspiratory and expiratory times were 3.3 and 2.0%, respectively. Volume was differentiated to flow. For respiratory rates ranging from 12 to 30 breaths/min, the mean error of the vest and our differentiation circuit in duplicating peak flows measured at the mouth was 3.5%. The ability of the vest to estimate changes in end-expiratory position or functional residual capacity was not as good as with VT; the mean error was 30.7%. For estimation of VT, ventilatory timing, and airflow in COPD patients, the inductance vest performs well. For measurement of changes in lung volume, improvements in vest design need to be made.
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