Neuroventilatory efficiency and extubation readiness in critically ill patients

• Published in: Critical care (London, England) Vol. 16; no. 4; p. R143
• Main Authors: Liu, Ling, Liu, Huogen, Yang, Yi, Huang, Yingzi, Liu, Songqiao, Beck, Jennifer, Slutsky, Arthur S, Sinderby, Christer, Qiu, Haibo
• Format: Journal Article
• Language: English
• Published: London BioMed Central 31.07.2012; BioMed Central Ltd
• Subjects: Airway Extubation; Artificial respiration; Blood Gas Analysis; Continuous positive airway pressure; Critical Care Medicine; Critical Illness; Critically ill; Diaphragm - innervation; Emergency Medicine; Female; Health aspects; Humans; Intensive; Male; Medical research; Medicine; Medicine & Public Health; Medicine, Experimental; Respiration, Artificial; Respiratory Function Tests; Respiratory Mechanics - physiology; Treatment Failure; Ventilator Weaning; Continuous Positive Airway Pressure; Inspiratory Muscle; Respiratory Drive; Chronic Obstructive Pulmonary Disease Patient; Spontaneous Breathing Trial
• ISSN: 1364-8535; 1466-609X; 1364-8535; 1466-609X
• DOI: 10.1186/cc11451

Introduction Based on the hypothesis that failure of weaning from mechanical ventilation is caused by respiratory demand exceeding the capacity of the respiratory muscles, we evaluated whether extubation failure could be characterized by increased respiratory drive and impaired efficiency to generate inspiratory pressure and ventilation. Methods Airway pressure, flow, volume, breathing frequency, and diaphragm electrical activity were measured in a heterogeneous group of patients deemed ready for a spontaneous breathing trial. Efficiency to convert neuromuscular activity into inspiratory pressure was calculated as the ratio of negative airway pressure and diaphragm electrical activity during an inspiratory occlusion. Efficiency to convert neuromuscular activity into volume was calculated as the ratio of the tidal volume to diaphragm electrical activity. All variables were obtained during a 30-minute spontaneous breathing trial on continuous positive airway pressure (CPAP) of 5 cm H 2 O and compared between patients for whom extubation succeeded with those for whom either the spontaneous breathing trial failed or for those who passed, but then the extubation failed. Results Of 52 patients enrolled in the study, 35 (67.3%) were successfully extubated, and 17 (32.7%) were not. Patients for whom it failed had higher diaphragm electrical activity (48%; P < 0.001) and a lower efficiency to convert neuromuscular activity into inspiratory pressure and tidal volume (40% ( P < 0.001) and 53% ( P < 0.001)), respectively. Neuroventilatory efficiency demonstrated the greatest predictability for weaning success. Conclusions This study shows that a mixed group of critically ill patients for whom weaning fails have increased neural respiratory drive and impaired ability to convert neuromuscular activity into tidal ventilation, in part because of diaphragm weakness. Trial Registration Clinicaltrials.gov identifier NCT01065428 . ©2012 Liu et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0 ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.