Positive end-expiratory pressure: Implications for tidal volume changes in anesthesia machine ventilation

Abstract

In clinical practice, the addition of positive end-expiratory pressure (PEEP) into a standard anesthesia circle circuit decreases the delivered tidal volume (DTV) to a patient. We studied the magnitude of the delta DTV/delta PEEP relationship in two commonly used anesthesia systems. In addition, the magnitude of the delta DTV/delta PEEP relationship varies with both pulmonary compliance and volume of gas contained in the patient's breathing system between the ventilator and PEEP valve site, and this was also evaluated. Routine monitoring of expired tidal volume should be used whenever PEEP is added to an anesthesia circuit.

Positive end-expiratory pressure and lung compliance: effect on delivered tidal volume

“…The VT~ l can be derived from the following equation. 1,5,6 VTdel : VTset "~-fresh gas flow rate. inspiratory time --VTPEEPIos s --VT(C+CL)Ios s where VT(CL+C)1oss is the loss due solely to CL and corn- pression of circuit and gas.…”