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Crit Care Med. 2013 Jun;41(6):1483-91. doi: 10.1097/CCM.0b013e31827caba0.

Estimation of patient's inspiratory effort from the electrical activity of the diaphragm.

Author information

1
Department of Experimental Medicine, University of Milan-Bicocca, Monza, Italy.

Abstract

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.

PMID:
23478659
DOI:
10.1097/CCM.0b013e31827caba0
[Indexed for MEDLINE]

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