Abstract
Effective (non-shunted) pulmonary blood flow (QEPr) was measured using a modified rebreathing technique and compared to QEPi determined by thermodilution and blood gas analysis at varying PEEP in non-injured and oleic acid injured lungs.
Nine mongrel dogs (18-26 Kgs) were anesthetized, intubated with cuffed tubes, and instrumented with intravenous, systemic arterial, and pulmonary arterial catheters. Ventilation was volume controlled at 15 breaths/minute and tidal volume adjusted to maintain PaCO2 between 35-45 torr. Noninvasive measurements of QEPr were done before and after determination of QEPi. PEEP was varied by 5 cm H2O increments from 0 to 15 before lung injury and 0 to 20 after central venous administration of oleic acid (0.10-0.15 ml/kg).
QEPr highly correlated with QEPi as seen in the figure (r=.92, R2=.85, n=99, p < .0001) using Pearson's correlation. The noninvasive measurement of QEPr was accurate at varying cardiac outputs (CO, 0.8-6.3 L/min) and intrapulmonary shunt (Qs/Qt, 0.03-0.67). The measurement of QEPr at varying levels of PEEP (0-20 on H2O) and subsequent changes in Qs/Qt demonstrates that QEPr is the pulmonary blood flow that undergoes gas exchange such that QEPr = CO (1-Qs/Qt).
The study validates the noninvasive rebreathing technique as a reliable measurement of the effective pulmonary blood flow at varying CO and Qs/Qt in acute respiratory failure indicating clinical utility during PEEP therapy.
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Burch, K., Parker, D., Brudno, D. et al. THE NONINVASIVE MEASUREMENT OF EFFECTIVE PULMONARY BLOOD FLOW IN ACUTE LUNG INJURY. Pediatr Res 21 (Suppl 4), 198 (1987). https://doi.org/10.1203/00006450-198704010-00193
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DOI: https://doi.org/10.1203/00006450-198704010-00193