Respiratory comfort and breathing pattern during volume proportional assist ventilation and pressure support ventilation: A study on volunteers with artificially reduced compliance

Objective: To assess respiratory comfort and associated breathing pattern d uring volume assist (VA) as a component of proportional assist ventilation and during pressure support ventilation (PSV). Design: Prospective, double-blind, interventional study. Setting: Laboratory. Subjects: A total of 15 healthy volunteers (11 females, 4 males) aged 21-31 yrs, Interventions: Decreased respiratory system compliance was simulated by ban ding of the thorax and abdomen. Volunteers breathed via a mouthpiece with V A and PSV each applied at two levels (VA, 8 cm H2O/L and 12 cm H2O/L; PSV, 10 cm H2O and 15 cm H2O) using a positive end-expiratory pressure of 5 cm H 2O throughout. The study was subdivided into two parts. In Part 1, voluntee rs breathed three times with each of the four settings for 2 mins in random order. In Part 2, the first breath effects of multiple, randomly applied m ode, and level shifts were studied. Measurements and Main Results: In Part 1, the volunteers were asked to esti mate respiratory comfort in comparison with normal breathing using a visual analog scale. In Part 2, they were asked to estimate the change of respira tory comfort as increased, decreased, or unchanged immediately after a mode shift, Concomitantly, the respiratory pattern (change) was characterized w ith continuously measured tidal volume, respiratory rate, pressure, and gas flow. Respiratory comfort during VA was higher than during PSV. The higher support level was less important during VA but had a major negative influe nce on comfort during PSV, Both modes differed with respect to the associat ed breathing pattern. Variability of breathing was higher during VA than du ring PSV (Part 1). Changes in respiratory variables were associated with ch anges in respiratory comfort (Part 2). Conclusions: For volunteers breathing with artificially reduced respiratory system compliance, respiratory comfort is higher with VA than with PSV, Th is is probably caused by a better adaptation of the ventilatory support to the volunteer's need with VA.