Model-based Identification of Work of Breathing in CPAP Ventilation of Adults

Abstract

The increasing burden of chronic respiratory disease to healthcare systems results in limited capacity to effectively treat patients. People with respiratory diseases, especially when exacerbated by muscular decruitment in sleep, are commonly prescribed a form of positive airway pressure (PAP) device to provide airway support. PAP is set to provide a clinically set PEEP (positive end expiratory pressure). The best method of setting PEEP, to maintain open airways without causing barotrauma, is still debated. Therefore, the efficacy of PAP is largely determined by clinical judgment at infrequent and expensive appointments with a respiratory specialist. Improving PEEP setting, requires improved understanding of, and ability to model, patient-specific pulmonary mechanics in relation to PAP. Investigation of subject work of breathing (WOB) contributions and their interaction with PAP has potential to inform control of PEEP to optimise the efficiency of patient effort. Imposed WOB increased with PEEP as the imposed resistance from CPAP circuitry increased. Subject lung elastance also increased with PEEP from a median of 4.98 to 8.31 cmH2O/L. Increases in imposed WOB and lung elastance account for the increase in subject muscular WOB (from 2.23, to 2.88, to 3.97 cmH2OL/L). Initial results from asthma subjects in the trial show a decrease in median subject WOB from ZEEP to 4cmH2O, which is not seen in non-asthmatics.