title: Breathing He-O2 shifts the lung pressure-volume curve of the dog.
abstract: To determine whether breathing a mixture of 80% He-20% O2 affects the lung pressure-volume (PV) curve, eight anesthetized paralyzed dogs were studied in a volume-displacement plethysmograph. Static PV curves on air were compared with PV curves obtained after equilibration with He-O2. The He-O2 PV curves were significantly shifted upward by an average of 5% total lung capacity. There was no change in compliance, indicating that the shift was due to lung expansion rather than a change in elasticity. Pretreatment of the dogs with cyclooxygenase inhibitors abolished the PV shift with He-O2. Four dogs had PV curves recorded on air and a mixture of O2, SF6, and Ne, a gas mixture with the same density as air but with 45% greater viscosity. The PV curve shift was even greater than observed with He-O2 and could again be virtually abolished with a cyclooxygenase inhibitor. These results suggest that breathing a high-viscosity gas mixture results in alveolar duct dilatation due to the release of a prostaglandin bronchodilator. This may need to be taken into account in the analysis of flow augmentation with He-O2.
mesh_terms: D000818:Animals; D004285:Dogs; D006371:Helium / Q000494:pharmacology*; D007213:Indomethacin / Q000494:pharmacology; D008469:Meclofenamic Acid / Q000494:pharmacology; D009356:Neon / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology*; D011312:Pressure; D012119:Respiration / Q000187:drug effects*; D012129:Respiratory Function Tests; D013459:Sulfur Hexafluoride / Q000494:pharmacology
chemical_list: D006371:Helium; D008469:Meclofenamic Acid; D009356:Neon; D010100:Oxygen; D013459:Sulfur Hexafluoride; D007213:Indomethacin