Comparative study of recruitment maneuver guided by pressure-volume curve on respiratory physiology and lung morphology between acute respiratory distress syndrome of pulmonary and extrapulmonary origin in canine models

Abstract

To determine effects of recruitment maneuver (RM) guided by pressure-volume (P-V) curve on respiratory physiology and lung morphology in canine models of acute respiratory distress syndrome of pulmonary or extrapulmonary origin (ARDSp and ARDSexp). Twenty-four healthy dogs were randomly divided into two groups with 12 dogs each: ARDSexp and ARDSp. Each dog in ARDSexp group was injected with oleic acid 0.1 ml/kg through femoral vein, and each dog in ARDSp group received hydrochloric acid 2 ml/kg via trachea. Subsequently, dogs with both models were randomly subdivided into lung protective ventilation strategy (LPVS) group and LPVS+RM group, respectively. Dogs in LPVS group were given LPVS only without RM. RM guided by P-V curve was performed in LPVS+RM group followed by LPVS and pressure controlled ventilation (PCV) mode was selected. Phigh was set at upper inflection point (UIP) of the P-V curve, positive end-expiratory pressure (PEEP) was set at lower inflection point (LIP)+2 cm H(2)O (1 cm H(2)O=0.098 kPa), and the duration of RM was 60 seconds. The duration of mechanical ventilation (MV) in both subgroups was 4 hours. The oxygenation index (PaO(2)/FiO(2)), relative lung mechanical indexes were measured in two ARDS models before establishment of ARDS model, and before and after RM. The UIP and LIP were calculated with P-V curve. The percentage of different volume in ventilation of lung accounting for total lung volume was compared by CT scan. The PaO(2)/FiO(2), UIP and LIP did not showed significant differences among all groups before ARDS and before RM. PaO(2)/FiO(2) and respiratory system compliance (Crs) were significantly elevated in LPVS+RM group of both models 4 hours after RM compared with corresponding LPVS group [PaO(2)/FiO(2) (mm Hg, 1 mm Hg=0.133 kPa) of ARDSexp model: 263.9±69.2 vs. 182.8±42.8, Crs (ml/cm H(2)O) of ARDSexp model: 11.3±4.2 vs. 9.7±3.7; PaO(2)/FiO(2) (mm Hg) of ARDSp model: 193.4±33.5 vs. 176.4±40.2, Crs (ml/cm H(2)O) of ARDSp model: 10.1±3.9 vs. 9.0±3.9, P<0.05 or P<0.01], and the airway pressure was significantly declined compared with corresponding LPVS group [peak inspiratory pressure (PIP), cm H(2)O ] of ARDSexp model: 24.1±7.4 vs. 30.2±8.5, plateau pressure (Pplat, cm H(2)O) of ARDSexp model: 19.1±7.3 vs. 25.6±7.7; PIP (cm H(2)O) of ARDSp model: 26.6±8.4 vs. 29.6±10.3, Pplat (cm H(2)O) of ARDSp model: 21.9±7.3 vs. 25.1±8.4, P<0.05 or P<0.01]. Moreover, PaO(2)/FiO(2), Crs, PIP and Pplat were improved better in ARDSexp model than ARDSp model (P<0.05 orP<0.01). Compared with LPVS maneuver, RM plus LPVS maneuver could significantly decrease the proportion of closure and hypoventilation region, and increase the proportion of normal ventilation region in both models [closure region of ARDSexp model: (9.9±3.1)% vs. (16.3±5.2)%, hypoventilation region of ARDSexp model: (10.2±4.2)% vs. (23.4±6.7)%, normal ventilation region of ARDSexp model: (76.2±12.3)% vs. (57.5±10.1)%; closure region of ARDSp model: (14.3±4.8)% vs. (18.2±5.1)%, hypoventilation region of ARDSp model: (17.4±6.3)% vs. (24.1±5.9)%, normal ventilation region of ARDSp model: (63.2±10.7)% vs. (54.6±11.3)%, P<0.05 or P<0.01]. All of the ventilation regions were better improved with ARDSexp model than ARDSp model (all P<0.05). RM guided by P-V curve could help obtain better oxygenation, improve pulmonary compliance and lung ventilation in ARDSexp and ARDSp, and better treatment effects are seen in ARDSexp dogs than ARDSp dogs.