Comparison of pressure and flow triggering systems during continuous positive airway pressure.
OBJECTIVE
Compare the inspiratory work of breathing (WOBI) during pressure triggering (PT), and flow triggering (FT) using two microprocessor ventilators.


METHODS
A randomized, crossover comparison of triggering strategies and ventilators used.


METHODS
Surgical intensive care unit.


METHODS
Ten patients recovering from acute respiratory failure (eight men, two women; mean age, 48 +/- 12 years) breathing on continuous positive airway pressure (CPAP) of 5 cm H2O were studied.


METHODS
Patients were randomly assigned to either receive 5 cm H2O CPAP via one of two units (Hamilton Veolar or Puritan Bennett 7200ae) using either PT or FT. Each patient had 30-min trials using the following: (1) Veolar FT; (2) Veolar PT; (3) 7200ae FT; and (4) 7200ae FT.


RESULTS
During each trial period, work of breathing (WOB) and pressure time product (PTP) were measured using a respiratory monitor (Bi-core CP-100). All patients were placed in semi-Fowler position and esophageal balloons were inserted and their position confirmed using the occlusion technique. Continuous measurements of peak negative pressure during inspiration, tidal volume (VT), minute ventilation (VE), respiratory frequency (f) were accomplished with a flow transducer at the proximal airway. FT with the 7200ae was superior to PT as measured by both the WOB (0.58 +/- 0.3 vs 0.84 +/- 0.2 J/L, p < 0.01) and PTP (148 +/- 50 vs 206 +/- 41 cm H2O/s/min, p, 0.05). FT with the Veolar was also superior to PT with respect to the WOB (0.53 +/- 0.2 vs 0.93 +/- 0.2 J/L, p < 0.01) and PTP (140 +/- 39 vs 229 +/- 46 cm H2O/s/min, p < 0.05).


CONCLUSIONS
FT reduces the WOB compared with PT, regardless of the ventilator used. The reduction in WOB during FT is related to improved responsiveness and changes in the posttrigger phase.
Branson
R D
RD
Department of Surgery, University of Cincinnati Medical Center, USA.
Campbell
R S
RS
Davis
K
K
Johnson
D J
DJ
D018592:Cross-Over Studies; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011312:Pressure; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy*; D014939:Work of Breathing