[Effects of prone position ventilation combined with recruitment maneuver on oxygenation and shunt in canines with acute respiratory distress syndrome].

OBJECTIVE: To evaluate the effects of prone position ventilation (PPV) combined with recruitment maneuver (RM) on oxygenation and intrapulmonary shunting in oleic acid-induced acute respiratory distress syndrome (ARDS) in canines while ventilated with lung protective ventilation strategy.

METHODS: ARDS was induced by oleic acid in 24 dogs, and the animals were ventilated with volume controlled ventilation (VCV), 16 cm H2O (1 cm H2O = 0.098 kPa) of positive end-expiratory pressure (PEEP) and small tidal volumes (V(T) 10 ml/kg). All the dogs were randomly divided by random digit table into 4 groups (6 each), a control group (supine position, SP group), a prone position group (PP group), a supine position + RM group (SPRM group), and a prone position + RM group (PPRM group), and then were ventilated by VCV for 4 h. Arterial and mixed venous blood gas analyses were measured. Data were analyzed using the SPSS for windows (version 11.5). Results were expressed as x +/- s. Homogeneity of variance test was performed. The differences in means were calculated using one-way ANOVA. Post-hoc multiple comparisons of means were performed using Least Significant Difference. Nonparametric tests for several independent samples were performed to compare differences between the ranks in the groups studied. P value of < 0.05 was considered statistically significant.

RESULTS: (1) At 15 min, PaO2/FiO2 in the SPRM group, the PP group and the PPRM group [(368 +/- 45) mm Hg (1 mm Hg = 0.133 kPa), (349 +/- 80) mm Hg, ( 423 +/- 43) mm Hg, respectively] was significantly higher than that in the SP group [(269 +/- 72) mm Hg, q = 2.77, 2.23, 4.31, respectively, all P < 0.05]. At 2 h, PaO2/FiO2 in the PP group and the PPRM group [(401 +/- 82) mm Hg, (416 +/- 23) mm Hg, respectively] was significantly higher than that in the SP group [(232 +/- 40) mm Hg, q = 3.99, 4.35, respectively, all P < 0.05]. At 4 h, PaO2/FiO2 in the PPRM group [(384 +/- 68) mm Hg] was significantly higher than that in the SP group [(256 +/- 75) mm Hg], that in the SPRM group [(267 +/-92) mm Hg] and that in the PP group [(284 +/- 83) mm Hg, q = 2.75, 2.56, 2.17, respectively, all P < 0.05]. (2) Intrapulmonary shunt (Q(S)/Q(T)) in the PP group was significantly decreased compared with that in the SP group from 30 min to 2 h [30 min (9.9 +/- 4.4)% vs (15.0 +/- 1.6)%, 1 h (9.7 +/- 4.5)% vs (16.0 +/- 2.0)%, 2 h (8.3 +/- 4.6)% vs (16.2 +/- 1.8)%, q = 2.86, 3.00, 3.65, respectively, all P < 0.05]. The Q(S)/Q(T), in the PPRM group was significantly decreased compared with that in the SP group from 30 min to 4 h [30 min (10.0 +/- 1.0)% vs (15.0 +/- 1.6)%, 1 h (10.4 +/- 2.7)% vs (16.0 +/- 2.0)%, 2 h (10.2 +/- 0.7)% vs (16.2 +/- 1.8)%, 4 h (10.1 +/- 1.1)% vs (15.7 +/- 1.7)%, q = 2.80, 2.67, 2.75, 2.99, respectively, all P < 0.05].

CONCLUSIONS: On the basis of small tidal volume lung and PEEP protective ventilation strategy, combining prone position and recruitment maneuver was more effective and showed a synergistic effect on improving oxygenation and intrapulmonary shunt.