Evidence of sequential opening and closing of lung units during inflation-deflation of excised rat lungs.
Frazer-DG; Weber-KC; Franz-GN
Respir Physiol 1985 Sep; 61(3):277-288
The opening and closing of lung units during ventilation was assessed in excised lungs from male hooded-Long-Evans-rats in terms of alterations in the pressure ranges for opening and closing. Pressure volume curves were constructed for slow inflation from a transpulmonary pressure of 0 centimeters of water (cmH2O) to a maximum pressure of 30cmH2O (maximum volume), for inflation to half maximum volume in the presence of small oscillations, for inflation to maximum volume in the presence of small oscillations, and for inflation to maximum volume and deflation to -5cmH2O. The changes in the small pressure volume loops superimposed upon the larger pressure volume curve were studied by computing the respective perturbation and quasistatic compliances for any given point along the curve. Comparison of the perturbation and quasistatic compliances indicated a nonlinear process involving relatively large increases in the quasistatic compliance and small increases in the perturbation compliance. Deviation of the reinflation curve from the curve describing deflation to a minimum pressure of 3cmH2O increased as the minimum pressure decreased. The authors propose a model of lung hysteresis to account for the large difference between the perturbation and quasistatic compliances and the deviation observed in the deflation curve as airway pressure decreases.
NIOSH-Author; Lung-function; In-vitro-studies; Physiology; Air-pressure; Airway-resistance; Pulmonary-function; Laboratory-animals; Models;
Author Keywords: Lung hysteresis; Lung pressure-volume curves; Recruitment-derecruitment of lung units; Transpulmonary pressure