Inspiratory flow effects on mechanically ventilated patients: lung volume, inhomogeneity, and arterial oxygenation

Abstract

Changes in the inspiratory flow rate of mechanically ventilated patients can affect arterial oxygenation. Although the mechanism producing this alteration is not certain, one possible mechanism is a change in ventilation inhomogeneity. This study was performed to determine if the inspiratory flow setting would affect ventilation inhomogeneity in patients who have minimal or no lung disease, but who require mechanical ventilation after cardiopulmonary bypass surgery. When inspiratory flows were doubled, PaO2 increased and FRC fell. However, no associated change in ventilation inhomogeneity was detected. It is concluded that inspiratory flow rate can affect arterial oxygenation of subjects without severe obstructive pulmonary disease through mechanisms other than altering ventilation inhomogeneity, such as changes in cardiac output or in distribution of perfusion.

PDPS: A pulmonary data processing system for assessment of gas exchange properties by multiple gas wash-out

“…The FRC at the end of the last expiration before wash-out starts can be calculated using the well-known mass-balance equation [19] stating that the partial volume in the lung occupied by the indicator gas before the wash-out, equals the sum of the partial volume of the .,Gas exchange ratio graphs (ratio of AFco 2/AFo2) of the same expirograms as in Fig. 2.…”