Effects of ventilatory pattern on experimental lung injury caused by high airway pressure.
OBJECTIVE
To determine the influence of clinician-adjustable ventilator settings on the development of ventilator-induced lung injury, as assessed by changes in gas exchange (Pao2), compliance, functional residual capacity, and wet weight to dry weight ratio.


METHODS
Randomized in vivo rabbit study.


METHODS
Hospital research laboratory.


METHODS
Forty-four anesthetized, mechanically ventilated adult rabbits.


METHODS
Ventilation for 2 hrs with pressure control ventilation at 45 cm H2O, Fio2 = 0.6, and randomization to one of five ventilatory strategies using combinations of positive end-expiratory pressure (3 or 12 cm H2O), inspiratory time (0.45, 1.0, or 2.0 secs), and frequency (9 or 23/min).


RESULTS
Among the ventilator strategies applied, PEEP at 12 cm H2O (elevated positive end-expiratory pressure) and inspiratory time at 0.45 secs (reduced inspiratory time) best preserved Pao2 (p <.003) and compliance (p <.035). During injury development, two consistent changes were observed: Tidal volume increased, and airway pressure waveform was transformed by extending the time to attain target pressure.


CONCLUSIONS
In this preclinical model, lung injury was attenuated by decreasing inspiratory time. As lung injury occurred, tidal volume increased and airway pressure waveform changed.
Simonson
Dana A
DA
Department of Pulmonary and Critical Care Medicine, Regions Hospital/HealthPartners and University of Minnesota Medical School, USA.
Adams
Alexander B
AB
Wright
Laurel A
LA
Dries
David J
DJ
Hotchkiss
John R
JR
Marini
John J
JJ
D000704:Analysis of Variance; D000818:Animals; D001469:Barotrauma / Q000209:etiology / Q000517:prevention & control*; D055370:Lung Injury; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods*; D011817:Rabbits; D011897:Random Allocation; D015656:Respiratory Mechanics