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EFFECTS OF DIFFERENT LEVELS OF PRESSURE SUPPORT ON INTRA-INDIVIDUAL BREATH-TO-BREATH VARIABILITY
Pressure support ventilation
Breath-to-breath variability
Patient-ventilator interaction
Coefficient of variation
Author
Affilliation
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil.
Federal University of Minas Gerais. Department of Electronics. Belo Horizonte, MG, Brazil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil / D’Or Institute for Research and Education. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil.
Federal University of Minas Gerais. Department of Electronics. Belo Horizonte, MG, Brazil.
Universidade Federal do Rio de Janeiro. Carlos Chagas Filho Institute of Biophysics. Laboratory of Respiration Physiology. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil / D’Or Institute for Research and Education. Rio de Janeiro, RJ, Brazil.
Fundação Oswaldo Cruz. Instituto Nacional de Infectologia Evandro Chagas. Laboratório de Pesquisa Clínica em Medicina Intensiva. Rio de Janeiro, RJ, Brasil.
Abstract
BACKGROUND: Evidence exists that during pressure support ventilation (PSV), the addition of an extrinsic (ie, ventilator-generated) breath-to-breath variability (BBV) of breathing pattern improves respiratory function. If BBV is beneficial per se, choosing the PS level that maximizes it could be considered a valid strategy for conventional PSV. In this study, we evaluated the effect of different PS levels on intrinsic BBV in acutely ill, mechanically ventilated subjects to determine whether a significant relationship exists between PS level and BBV magnitude. METHODS: Fourteen invasively mechanically ventilated subjects were prospectively studied. PS was adjusted at 20 cm H2O and sequentially reduced to 15, 10, and 5 cm H2O. Arterial blood gas analysis and pressure at 0.1 s after the onset of inspiration (P0.1) were measured at each PS level. Airway and
esophageal pressure and air flow were continuously recorded. Peak inspiratory flow, tidal volume (VT), breathing frequency, and pressure-time product (PTP) were calculated on a breath-by-breath basis. The breathing pattern variability was assessed by the coefficient of variation of the time series of VT, peak inspiratory flow, and breathing frequency from 60 consecutive breath cycles at each PS level. A general linear model for repeated measures was applied, with PS as an independent factor. A significance level of .05 was considered. RESULTS: Despite a large inter-individual difference in all measured variables (P < .001), the coefficient of variation was as low as 30%, and no significant differences in the coefficient of variation of peak inspiratory flow, breathing frequency, and VT between PS levels were observed (P > .15). Additionally, a significant increase in P0.1, PTP, and breathing frequency (P < .01) and a reduction in VT (P < .001) were observed with PS reduction. CONCLUSIONS: Despite a significant increase in spontaneous activity with PS reduction, BBV was not influenced by the PS level and was as low as 30% for all evaluated parameters.
Keywords
Key wordsPressure support ventilation
Breath-to-breath variability
Patient-ventilator interaction
Coefficient of variation
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