Fabrícia C Hoff1, Mauro R Tucci2, Marcelo B P Amato2, Laura J Santos3, Josué A Victorino4. 1. Intensive Care Unit, Hospital Mãe de Deus, Porto Alegre, Brazil; Graduate Program in Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. 2. Pulmonary Division, Heart Institute (INCOR), Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil. 3. Graduate Program in Cardiology and Cardiovascular Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Physiotherapy Division, Universidade Luterana do Brasil, Torres, Brazil. 4. Intensive Care Unit, Hospital Mãe de Deus, Porto Alegre, Brazil; Graduate Program in Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil; Intensive Care Unit, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil. Electronic address: josuev@terra.com.br.
Abstract
PURPOSE:Expiratory asynchrony during pressure support ventilation (PSV) has been recognized as a cause of patient discomfort, increased workload, and impaired weaning process. We evaluated breathing pattern, patient comfort, and patient effort during PSV comparing 2 flow termination criteria: fixed at 5% of peak inspiratory flow vs automatic, real-time, breath-by-breath adjustment within the range of 5% to 55%. MATERIALS AND METHODS: Randomized crossover clinical trial. Sixteen awake patients, in the process of weaning, under PSV for more than 24 hours were subjected to 3 phases of PSV, each lasting 1 hour and using 1 of the 2 aforementioned termination criteria. RESULTS: Effective pressure support during automatic adjustment (AA) was 12.5±3.2 cm H2O vs 12.5±3.9 cm H2O (P=.9) with the fixed termination criterion, and external positive end-expiratory pressure was 6.2±1.8 vs 6.8±2 (P<.05). The effective termination criterion was higher during AA (31% [23-39] vs 12% [6-23]; P<.01), but without producing premature breath terminations. Pressure overshoots and alternative cycling-off were also decreased. Throughout the AA period, we observed a higher respiratory rate (24±8 breaths/min vs 19±6 breaths/min; P<.001), lower tidal volume (484 ± 88 mL vs 518±102 mL; P<.001), and shorter inspiratory times (1.0±0.3 seconds vs 1.3±0.3 seconds; P<.001). Automatic adjustment was associated with lower airway occlusion pressure after 0.1 second (P0.1) (1.8±0.9 cm H2O vs 2.4±1 cm H2O; P<.01), lower pressure-time product to trigger the ventilator, and lower subjective discomfort (visual analog scale, 3.7±1.3 vs 4.5±1.2; P<.001). CONCLUSIONS: When compared with a fixed termination criterion, the use of a variable, real-time-adjusted termination criterion improved some indices of patient-ventilator synchrony, producing better breathing pattern, less discomfort, and slightly lower patient effort during PSV.
RCT Entities:
PURPOSE: Expiratory asynchrony during pressure support ventilation (PSV) has been recognized as a cause of patient discomfort, increased workload, and impaired weaning process. We evaluated breathing pattern, patient comfort, and patient effort during PSV comparing 2 flow termination criteria: fixed at 5% of peak inspiratory flow vs automatic, real-time, breath-by-breath adjustment within the range of 5% to 55%. MATERIALS AND METHODS: Randomized crossover clinical trial. Sixteen awake patients, in the process of weaning, under PSV for more than 24 hours were subjected to 3 phases of PSV, each lasting 1 hour and using 1 of the 2 aforementioned termination criteria. RESULTS: Effective pressure support during automatic adjustment (AA) was 12.5±3.2 cm H2O vs 12.5±3.9 cm H2O (P=.9) with the fixed termination criterion, and external positive end-expiratory pressure was 6.2±1.8 vs 6.8±2 (P<.05). The effective termination criterion was higher during AA (31% [23-39] vs 12% [6-23]; P<.01), but without producing premature breath terminations. Pressure overshoots and alternative cycling-off were also decreased. Throughout the AA period, we observed a higher respiratory rate (24±8 breaths/min vs 19±6 breaths/min; P<.001), lower tidal volume (484 ± 88 mL vs 518±102 mL; P<.001), and shorter inspiratory times (1.0±0.3 seconds vs 1.3±0.3 seconds; P<.001). Automatic adjustment was associated with lower airway occlusion pressure after 0.1 second (P0.1) (1.8±0.9 cm H2O vs 2.4±1 cm H2O; P<.01), lower pressure-time product to trigger the ventilator, and lower subjective discomfort (visual analog scale, 3.7±1.3 vs 4.5±1.2; P<.001). CONCLUSIONS: When compared with a fixed termination criterion, the use of a variable, real-time-adjusted termination criterion improved some indices of patient-ventilator synchrony, producing better breathing pattern, less discomfort, and slightly lower patient effort during PSV.