Pulmonary NO and C18O2 uptake during pressure-induced lung expansion in rabbits.
In artificially ventilated animals we investigated the dependence of the pulmonary diffusing capacities of nitric oxide (NO) and doubly 18O-labeled carbon dioxide (DLNO, DLC18O2) on lung expansion with respect to ventilator-driven increases in intrapulmonary pressure. For this purpose we applied computerized single-breath experiments to 11 anesthetized paralyzed rabbits (weight 2.8-3.8 kg) at various alveolar volumes (45-72 ml) by studying the almost entire inspiratory limb of the respective pressure/volume curves (intrapulmonary pressure: 6-27 cmH2O). The animals were ventilated with room air, employing a computerized ventilatory servo-system that we designed to maintain mechanical ventilation and to execute the particular lung function tests automatically. Each single-breath maneuver was started from residual volume (13.5+/-2 ml, mean+/-SD) by inflating the rabbit lungs with 35-55 ml indicator gas mixture containing 0.05% NO in N2 or 0.9% C18O2 in N2. Alveolar partial pressures of NO and C18O2 were measured by respiratory mass spectrometry. Values of DLNO and DLC18O2 ranged between 1.55 and 2.49 ml/(mmHg min) and 11.7 and 16.6 ml/(mmHg min), respectively. Linear regression analyses yielded a significant increase in DLNO with simultaneous increase in alveolar volume (P<0.005) and intrapulmonary pressure (P<0.023) whereas DLC18O2 was not improved. Our results suggest that the ventilator-driven lung expansion impaired the C18O2 blood uptake conductance, finally compensating for the beneficial effect of the increase in alveolar volume on DLC18O2 values.
Heller
Hartmut
H
Department of Physiology, University of Bonn, Argelanderstr. 2a, 53115 Bonn, Germany. h.heller@uni-bonn.de
Schuster
Klaus-Dieter
KD
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D002682:Chinchilla; D005260:Female; D006824:Hybridization, Genetic; D008168:Lung / Q000502:physiology; D008176:Lung Volume Measurements; D008297:Male; D013058:Mass Spectrometry; D009569:Nitric Oxide / Q000378:metabolism*; D011312:Pressure; D011653:Pulmonary Diffusing Capacity / Q000502:physiology*; D011817:Rabbits; D012121:Respiration, Artificial; D014797:Vital Capacity / Q000502:physiology
D002245:Carbon Dioxide; D009569:Nitric Oxide