Assessment of respiratory drive and muscle function in the pediatric intensive care unit and prediction of extubation failure

BACKGROUND: Extubation failure can result from poor respiratory drive, impaired respiratory muscle function, or excessive inspiratory load. Measurement of airway pressure changes either during tidal breathing or after end-expiratory occlusion allows assessment of respiratory drive and muscle function. OBJECTIVE: To determine whether the results of airway pressure measurements characterized children who subsequently failed extubation and identify which test's results had the highest predictive performance. DESIGN: A prospective study. SETTING: Pediatric intensive care unit. PATIENTS: A sample of 42 stable intubated pediatric patients who were judged clinically ready for extubation. METHODS: A pneumotachograph was placed between the endotracheal tube and ventilator circuit. Airway pressure was measured from the pneumotachograph. The flow and pressure signals were amplified and displayed in real time on a laptop computer. During a temporary disconnection from the ventilator, the airway was occluded at end-expiration and the occlusion maintained for at least five breaths. From the first inspiratory effort during the occlusion, the pressure generated after 0.1 sec of occlusion (P0.1) and the largest negative pressure (PI) were calculated. From the series of breaths during the occlusion, the maximum P0.1 (P0.1 max) and maximum PI (PI max) were determined and P0.1/P0.1 max, PI/PI max and P0.1/PI max calculated. From spontaneous, tidal breaths during ventilatory support the pressure time product was calculated. RESULTS: Thirty-six (84%) of the children were successfully extubated. The children who failed extubation were characterized by a lower median P0.1 (p <.06), P0.1/P0.1 max, p <.05 and P0.1/PI max (p <.02). P0.1 and P0.1/P0.1 max and performed best in predicting extubation failure (areas under the receiver operator characteristic curves, 0.76 and 0.77 respectively). CONCLUSION: Assessment of P0.1 was the most useful airway pressure measurement in predicting extubation failure. Assessment of P0.1 may help to characterize children likely to fail extubation.