The effect of blood flow and diffusion impairment on pulmonary gas exchange: A computer model

✍ Scribed by Wesley M. Granger; David A. Miller; Ina C. Ehrhart; Wendell F. Hofman

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 564 KB
• Volume: 20
• Category: Article
• ISSN: 0010-4809
• DOI: 10.1016/0010-4809(87)90037-1

✦ Synopsis

An assumption of the classical three-compartment lung model is that the physiologic shunt fraction (Q/Q) remains constant with changes in cardiac output (Ql). As a result, when Qt decreases, both the arterial Oz tension (P,oJ and the mixed venous 02 tension (P,",) must also decrease. Yet observations in intact dogs with pulmonary edema and humans with the adult respiratory distress syndrome (ARDS) indicate that as Q, decreases, QslQt occasionally declmes while the P,oz increases. The present study was conducted to examine these discordant observations using a computer model of pulmonary gas exchange with a diffusion impairment. A computer model of gas exchange was developed to specifically analyze the . effect of changmg Qt upon PaOZ and Q,/Q in the presence of diffusion impairment. Using the classical three-compartment model of gas exchange, a diffusion impairment was inserted by a MIMIC subroutine. The results of this computer simulation indicated that in the presence of a diffusion impairment, lowering & caused P,oz to increase while Qs/Q, and P,ez decreased. These changes indicated that a diffusion impairment might account for the experimental observations of the effects of Q, on Paol in ARDS.