title: Effect on lung volumes of oxygen concentration when breathing is restricted.
abstract: We have examined the effect of the fractional concentration of nitrogen (FIN2) on the decrease in lung volumes which occurs during restricted breathing with oxygen-nitrogen mixtures. Conscious human subjects breathed one of five gas mixtures of oxygen and nitrogen for 15 min on each of five occasions. For the final 5 min of each 15-min period, functional residual capacity (FRC) was reduced by one tidal volume, by external pressurization. After return to normal breathing, the subjects showed a statistically significant decrease in FRC and residual volume (RV), which became larger as FIO2 increased from 30% to 100%. This reduction in lung volumes was resistant to early reexpansion. The maximum decrease in both FRC and RV was found with 100% oxygen, and was 10% of the control lung volumes. The use of a mixture of 75% nitrogen and 25% oxygen prevented this decrease in lung volumes. Nitrogen 50% reduced the decrease in FRC, but did not affect the decrease in RV. The difference in effect on lung volumes between FIO2 25% and 30% was statistically significant, indicating a watershed area for FIN2 between 70% and 75%.
authors: Department of Anasthesia and Intensive Care, Otago University, Dunedin, New Zealand.
authors: A B
authors: AB
authors: Baker
authors: A
authors: A
authors: McGinn
authors: C
authors: C
authors: Joyce
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000008:administration & dosage*; D010100:Oxygen / Q000008:administration & dosage*; D012115:Residual Volume / Q000502:physiology
chemical_list: D009584:Nitrogen; D010100:Oxygen