No abstract

Lung volumes, arterial blood gases, respiratory control system sensitivity, and oxygen cost of breathing were studied in obese but otherwise normal individuals and compared to similar studies in nonobese control subjects. Respiratory control system sensitivity as measured by the response to 5% carbon dioxide in air was normal in most obese subjects but reduced in certain obese individuals indistinguishable from the others on the basis of clinical evaluation or resting air studies. While breathing 5% carbon dioxide, the ventilation required to maintain any given alveolar carbon dioxide tension was directly dependent on weight. Oxygen cost of breathing in the ventilation range of 10–30 l/min. was elevated in 4 of 12 obese subjects, and in 6 of 9 obese subjects in the range of 20–40 l/min. There was no correlation between oxygen cost of breathing and respiratory control system sensitivity. Submitted on April 29, 1960

In 17 anesthetized dogs, 50–150 ml of isotonic saline or human amniotic fluid were instilled into a degassed lobe and after 2–6 hr of spontaneous or artificial ventilation, the lungs were excised. Static pressure-volume and extract surface tension values were then determined on a fluid- and a nonfluid-instilled lobe from each animal. When compared with nonfluid-instilled lobes the fluid-instilled lobes were found to have proportionately smaller volumes at maximum inflation ( P < .02) and during deflation ( P < .001) as well as regional areas with higher surface tension properties ( P < .001). It is proposed that the pressure-volume studies may furnish a useful means of assessing the anatomical extent of alterations in lung surface tension. There was a significant negative correlation between maximum inflation volumes and maximum surface tensions ( P < .001) as well as between the volumes during deflation and the minimum surface tensions ( P < .001). It is concluded that intra-alveolar fluid may inactivate or displace the surface-active material from the alveolar lining membrane. amniotic fluid; lung pressure-volume studies; lung surfactant Submitted on April 11, 1963