1995 OPEN FORUM Abstracts
ALTERING FLOW RATE DURING PRESSURE SUPPORT VENTILATION: EFFECTS ON WORK OF BREATHING AND RESPIRATORY DRIVE.
Massimo Croci MD, Paolo Pelosi MD, Davide Chiumello MD, Luciano Gattinoni MD Inst. of Anesthesia and Intensive Care, University of Milan, Ospedale Maggiore IRCCS, Milan, Italy.
Pressure support delivered by various mechanical ventilators is characterized by a non adjustable, rapide rise to a selected pressure. A new ventilator (Bear 1000) allows an adjustable pressurization rate (PR), resulting in a variable peak inspiratory flow (PIF) during pressure support ventilation (PSV). Aim of this study was to evaluate the usefulness of variable pressurization rate in reducing work of breathing and respiratory drive during PSV. METHODS We studied 7 stable patients, during weaning phase with PSV (PEEP 4.3±2 cm H_2O, PS 9±2 cm H_2O, F_IO_2 0.45±0.1). Measuring gas flow, airway and esophageal pressures we computed PIF, work of breathing per minute (WOB/min) and per liter of ventilation (WOB/1), and respiratory drive (P0.1). Measurements were obtained at PS of 5 and 15 cm H_2O with highest, lowest and optimal PR. Optimal PR was defined as that resulting in minimum WOB/min. RESULTS Data are expressed as mean ± S.D.
PS 5 cm H_2O Lowest Highest Optimal
PIF (1/s) 0.44±0.11 0.62±0.07 0.61±0.09 *$
WOB/1 (J/1)2±10.8±0.4 0.8±0.4 *
P0.1 (cm H_2O) 4±2.6 2.1±1.2 2.2±1.5 *
PS 15 cm H_2O
PIF (1/s) 0.46±0.09 1.09±0.10.79±0.17 *#
WOB/1 (J/1)1±0.6 0.4±0.1 0.1±0.1*#
P0.1 (cm H_2O)3.3±2.3 1.8±1.1 2.4±0.8*#
ANOVA: *p < 0.01 compared to Lowest PR, $p < 0.05 compared to highest PR, #p < 0.01 compared to highest PR. CONCLUSION We conclude that the possibility to adjust PR, and hence PIF, during PSV is an useful tool to improve patient-ventilator synchrony at different levels of pressure support.