A GENERAL 2-COMPARTMENT MODEL FOR MECHANICAL VENTILATION

A general mathematical model for the dynamic behavior of the two-compa rtment respiratory system in response to an arbitrary applied inspirat ory pressure is investigated. The model is used to compute explicit ex pressions for ventilation and pressure variables of clinical interest, for clinician-selected and impedance-determined inputs. The outcome v ariables include tidal volume, end-expiratory pressure, minute ventila tion, mean alveolar pressure for each compartment, given resistive par ameters and compliances of the system. The calculation of these outcom e variables assume that the patient is ventilated under passive condit ions. Limiting values of the outcome variables as the frequency of the breathing cycle increases are also computed for three basic types of ventilation: constant, linear, and sinusoidal pressure waveforms. Expl icit expressions for the limiting values of certain ratios of the key outcome variables (tidal volume,end-expiratory pressure, and mean alve olar pressure) are computed and are shown to be independent of the app lied airway pressure.