OBJECTIVES: To calculate an index (termed Pmusc/Eadi index) relating the pressure generated by the respiratory muscles (Pmusc) to the electrical activity of the diaphragm (Eadi), during assisted mechanical ventilation and to assess if the Pmusc/Eadi index is affected by the type and level of ventilator assistance. The Pmusc/Eadi index was also used to measure the patient's inspiratory effort from Eadi without esophageal pressure. DESIGN: Crossover study. SETTING: One general ICU. PATIENTS: Ten patients undergoing assisted ventilation. INTERVENTION: Pressure support and neurally adjusted ventilator assist delivered, each, at three levels of ventilatory assistance. MEASUREMENT AND MAIN RESULTS: Airways flow and pressure, esophageal pressure, and Eadi were continuously recorded. Sixty tidal volumes for each ventilator settings were analyzed off-line, at three time points during inspiration. For each time point, Pmusc/Eadi index was calculated. Pmusc/Eadi index was also calculated from airway pressure drop during end-expiratory occlusions. Pmusc/Eadi index was very variable among patients, but within one patient it was not affected by type and level of ventilator assistance. Pmusc/Eadi index decreased during the inspiration. Pmusc/Eadi index obtained during an occlusion from airway pressure swing was tightly correlated with that derived from esophageal pressure during tidal ventilation and allowed to estimate pressure time product. CONCLUSIONS: Pmusc is tightly related to Eadi, by a proportionality coefficient that we termed Pmusc/Eadi index, stable within each patient under different conditions of ventilator assistance. The derivation of the Pmusc/Eadi index from Eadi and airway pressure during an expiratory occlusion enables a continuous estimate of patient's inspiratory effort.
|Titolo:||Estimation of patient's inspiratory effort from the electrical activity of the diaphragm|
|Parole Chiave:||diaphragmatic electromyogram; mechanical ventilation; monitoring; neurally adjusted ventilatory assist; pressure support ventilation; work of breathing; adult; aged; aged, 80 and over; cross-over studies; diaphragm; electromyography; female; humans; inhalation; male; middle aged; respiration artificial|
|Settore Scientifico Disciplinare:||Settore MED/41 - Anestesiologia|
|Data di pubblicazione:||giu-2013|
|Digital Object Identifier (DOI):||10.1097/CCM.0b013e31827caba0|
|Appare nelle tipologie:||01 - Articolo su periodico|