P-V characteristics in heart-pulsation affected and non-affected lung units: a model

Elastic recoil pressure, pleural pressure and pressure pulsation of the heart (PHRT) control the expired flow from a small lung unit. Variability in each trait may affect the expirate. The same (SDPV) or different (DDPV) regional distribution of P-V characteristics, regional effects of PHRT-affected (O) and non-affected units (N) and regional differences in pleural pressure, were incorporated into a computer model. Output acceptability was judged by the alveolar slope of the N2 washout, cardiogenic oscillations (CO) and the phase shift between PHRT and CO. Can SDPV be in both O and N units? What causes CO and phase shift? With SDPV in O and N units, CO were negligibly small. The incorporation of the pleural pressure difference did not fulfill the three criteria, which were met when there was DDPV in the N and O units. We conclude that the distribution of P-V characteristics changes with the distance from a pulsating artery, and only DDPV, and not different time constants or pleural pressure difference, can explain CO.