Model-Based Approaches for Breath-to-breath Estimation of Patient Effort during Mechanical Ventilation

Patient inspiratory effort during invasive mechanical ventilation is the voluntary breathing effort made by the patient while receiving partial assistance from a ventilator. Monitoring the effort is crucial to prevent lung and diaphragm injuries, optimize ventilation, and for weaning. Currently, invasive sensors are used to monitor the patient's effort or techniques that only give an intermittent estimate of the effort. Several noninvasive model-based techniques to estimate patient effort are available in the literature which could potentially give a breath-to-breath estimate of the effort without the use of invasive sensors. However, most techniques are not clinically validated and a systematic comparison of techniques is lacking. We tested and compared five different model-based estimation techniques for estimating patient effort noninvasively, including a new method that uses a more detailed model than is currently available in the literature. First, the techniques were tested on simulated data, after this, they were tested on clinical data recorded in the intensive care unit. The results indicated that least square fitting and fitting of an extended equation of motion performed well in both tests. However, techniques that estimated both the respiratory mechanics parameters and the patient's inspiratory effort on the same breath were not able to give reliable estimates. More research needs to be done to verify that the estimates correspond to the measurements of invasive sensors.