Normal subjects have a larger diffusing capacity normalized per liter alveolar volume (DL/VA) in the supine than in the sitting position. Body position changes total lung diffusing capacity (DL), DL/VA, membrane conductance (Dm), and effective pulmonary capillary blood volume (Qc) as a function of alveolar volume (VA). These functions were studied in 37 healthy volunteers. DL/VA vs. VA yields a linear relationship in sitting as well as in supine position. Both have a negative slope but usually do not run parallel. In normal subjects up to 50 yr old DL/VA and DL increased significantly when subjects moved from a sitting to a supine posture at volumes between 50 and 100% of total lung capacity (TLC). In subjects greater than 50 yr old the responses of DL/VA and DL to change in body position were not significant at TLC. Functional residual capacity (FRC) decreases and DL/VA increases in all normal subjects when they change position from sitting to supine. When DL/VA increases more than predicted from the DL/VA vs. VA relationship in a sitting position, we may infer an increase in effective Qc in the supine position. In 56% of the volunteers, supine DL was smaller than sitting DL despite a higher DL/VA at FRC in the supine position because of the relatively larger decrease in FRC. When the positional response at TLC is studied, an estimation obtained accidentally at a volume lower than TLC may influence results. Above 80% of TLC, Dm decreased significantly from sitting to supine. Below this lung volume the decrease was not significant. The relationship between Qc and VA was best described by a second-order polynomial characterized by a maximum Qc at a VA greater than 60% of TLC. Qc was significantly higher in the supine position than in the sitting position, but the difference became smaller with increasing age. In observing the sitting and supine positions, we saw a decrease in maximum Qc normalized per square meter of body surface area with age.
The concentration of free epinephrine and norepinephrine in plasma and 24-hr urine samples, collected from members of the Dutch Monte Rosa expedition (July 1963) was investigated during 17 days at various altitudes up to 4,560 m. The results indicate that the levels of both plasma and urine catecholamines were elevated during the expedition, the plasma levels reaching a maximum towards the end of the 12 days sojourn at 4,560 m. In general there was a twofold increase in total catecholamine concentration in the samples collected at high altitude as compared to control values at sea level. This difference was due to a significant increase in the norepinephrine concentration; there was little change in epinephrine level. epinephrine and norepinephrine; sympathoadrenal activity Submitted on September 2, 1964
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.