Avaliação da força muscular inspiratória (PImáx) durante o desmame da ventilação mecânica em pacientes neurológicos internados na unidade de terapia intensiva

A ventilação mecânica, freqüentemente necessária em pacientes em estado crítico, pode ser associada à perda de força muscular respiratória por diversos mecanismos. Nosso objetivo foi avaliar a progressão da força da musculatura respiratória durante o processo de desmame, por mensuração seriada da PImáx até a independência completa da ventilação mecânica em pacientes neurológicos. A PImáx foi avaliada evolutivamente, uma vez ao dia, durante todo o período de desmame, com auxílio de manovacuômetro e válvula unidirecional. Foram incluídos no estudo 31 pacientes neurológicos (pós acidente vascular ou trauma crânio-encefálico) em desmame ventilatório e os valores obtidos foram comparados aos previstos, segundo Black e Hyatt. A média de PImáx inicial (primeiro dia do desmame) foi - 40,0±20,0 cmH2O (39% do previsto) (pMechanical ventilation, often needed in critically ill patients, may be associated to loss of respiratory muscular force due to several mechanisms. The objective was to assess the progression of respiratory muscular force during weaning from mechanical ventilation by using serial measurement of maximum inspiratory pressure until complete discontinuation in neurological patients. The PImax was progressively assessed by using manovacuometer and unidirectional valve once a day during the whole period of mechanical ventilation weaning. Thirty-one neurological patients (after stroke or craniocerebral trauma) undergoing weaning from mechanical ventilation were included for study, and the values obtained were compared to those established by Black and Hyatt. The initial mean PImax (first day of weaning) was - 40.0±20.0 cmH2O (39% of the expected value) (p < 0.05), reaching 50% at day 5 and 60% at day 10. It was observed an increase of 21% (p < 0.05) between the first and tenth days. On the 13th day, mechanical ventilation had been completely discontinued in all patients. Therefore a progressive evaluation of the inspiratory muscular force in patients undergoing prolonged mechanical ventilation shows that the complete discontinuation is possible in neurological patients with 72% of the established values