A brief airway occlusion is sufficient to measure the patient’s inspiratory effort/electrical activity of the diaphragm index (PEI)

Abstract

Pressure generated by patient's inspiratory muscles (Pmus) during assisted mechanical ventilation is of significant relevance. However, Pmus is not commonly measured since an esophageal balloon catheter is required. We have previously shown that Pmus can be estimated by measuring the electrical activity of the diaphragm (EAdi) through the Pmus/EAdi index (PEI). We investigated whether PEI could be reliably measured by a brief end-expiratory occlusion maneuver to propose an automated PEI measurement performed by the ventilator. Pmus, EAdi, airway pressure (Paw), and flow waveforms of 12 critically ill patients undergoing assisted mechanical ventilation were recorded. Repeated end-expiratory occlusion maneuvers were performed. PEI was measured at 100 ms (PEI 0.1) and 200 ms (PEI 0.2) from the start of the occlusion and compared to the PEI measured at the maximum Paw deflection (PEI occl , reference). PEI 0.1 and PEI 0.2 tightly correlated with PEI occl , (p < 0.001, R 2 = 0.843 and 0.847). At a patient-level analysis, the highest percentage error was-64% and 50% for PEI 0.1 and PEI 0.2 , respectively, suggesting that PEI 0.2 might be a more reliable measurement. After correcting the error bias, the PEI 0.2 percentage error was lower than ± 30% in all but one subjects (range − 39 to + 29%). It is possible to calculate PEI over a brief airway occlusion of 200 ms at inspiratory onset without the need for a full patient's inspiratory effort. Automated and repeated brief airway occlusions performed by the ventilator can provide a real time measurement of PEI; combining the automatically measured PEI with the EAdi trace could be used to continuously display the Pmus waveform at the bedside without the need of an esophageal balloon catheter.

Patient Self-Inflicted Lung Injury—A Narrative Review of Pathophysiology, Early Recognition, and Management Options

“…Electrical activity of the diaphragm (EAdi) provides important information about the crural diaphragm. The P mus /EAdi (PEI) index characterizes the pressure generated by the respiratory muscles in relation to the electrical activity of the diaphragm, which facilitates the discrimination between the respiratory drive (electrical activity) and the respiratory effort (generated pressure) [50,51]. The limitation of EAdi measurement lies in its invasiveness, but small-sample clinical studies confirmed a significant correlation between EAdi and the diaphragmatic electrical activity measured by surface electromyography [52,53].…”

Diaphragm function in acute respiratory failure and the potential role of phrenic nerve stimulation

“…Thus, there is a paucity of evidence to define reference values for weakness or for optimal diaphragm activity during mechanical ventilation using EA di . Normalizing EAdi based on airway occlusion pressure offers a promising approach [35].…”

Proportional modes of ventilation: technology to assist physiology

“…The correction factor (/1.5) is required, because in the presence of an occlusion, the diaphragm generates more pressure for the same EAdi than with an open airway [26]. NME calculations over a brief airway occlusion of 200 ms at inspiratory onset tightly reflect NME occl [78], and estimate inspiratory effort. A change in NME could also indicate recruitment of accessory respiratory muscles, since EAdi is insensitive to recruitment of accessory muscles.…”