OBJECTIVES: The level of pressure-support ventilation can affect mean airway pressure and potentially lung volume, but its increase is usually associated with a reduced respiratory rate, and the net effects on the gas exchange process and its components, including end-expiratory lung volume, have not been carefully studied. We measured pulmonary conductance for gas exchange based on lung diffusion for carbon monoxide in patients receiving pressure-support ventilation. DESIGN: Prospective, randomized, crossover study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Sixteen patients mechanically ventilated in pressure-support ventilation mode and free from chronic obstructive pulmonary disease. INTERVENTIONS: Two pressure-support ventilation levels (5 cm H2O difference) at the same level of positive end-expiratory pressure. MEASUREMENTS AND MAIN RESULTS: End-expiratory lung volume, lung diffusion for carbon monoxide, and SpO2/Fio2 were evaluated. Increasing pressure-support ventilation by 5 cm H2O significantly increased the mean tidal volume from 6.8 to 8.5 mL/kg of predicted body weight and decreased the mean respiratory rate by 6.6 breaths per minute. Although SpO2/Fio2 did not change significantly, there was a slight but significant decrease in lung diffusion for carbon monoxide (average decay rate of 4.5%) at high pressure-support ventilation. The pressure-support ventilation level did not significantly affect end-expiratory lung volume (1737±629 mL at 9.6±2.5 cm H2O pressure-support ventilation level vs. 1749±657 mL at 14.9±2.1 cm H2O pressure-support ventilation level). CONCLUSIONS: A 5-cm H2O increase in pressure-support ventilation neither affected end-expiratory lung volume nor increased the pulmonary volume participating in gas exchange. A target tidal volume closer to 6 mL/kg of predicted body weight than to 8 mL/kg during pressure-support ventilation was associated with better gas exchange.
|Titolo:||Effect of pressure support on end-expiratory lung volume and lung diffusion for carbon monoxide|
DI MARCO, FABIANO (Secondo)
|Parole Chiave:||humans ; aged ; pulmonary gas exchange ; prospective studies ; hospitals, university ; aged, 80 and over ; adult ; intensive care units ; cross-over studies ; carbon monoxide ; middle aged ; positive-pressure respiration ; lung volume measurements ; female ; male|
|Settore Scientifico Disciplinare:||Settore MED/10 - Malattie dell'Apparato Respiratorio|
|Data di pubblicazione:||ott-2011|
|Digital Object Identifier (DOI):||10.1097/CCM.0b013e3182227fce|
|Appare nelle tipologie:||01 - Articolo su periodico|