Dynamic modeling of patient breathing effort in response to change in pressure support in mechanical ventilation

A patient-ventilator system is introduced where the input is pressure support level (PSV) from the ventilator and the output is the patient´s mechanical work of breathing per minute, or power of breathing (POB). With higher level of pressure support from the ventilator, less effort is needed by the patient to attain the needed the level of ventilation. However, due to several physiological control loops regulating the level of respiration, the dynamic response of the patient due to a change in PSV level can be very complicated. In this study, this dynamic behavior is characterized using a first order system. The dynamic model of the patient-ventilator system has been obtained numerically based on data collected from five patients receiving mechanical ventilation with different levels of pressure support. The results show a wide range of response times among the patients but very limited range in steady state behavior of the system, i.e. DC Gain.