Effect of sustained inflation with different degrees of negative pressure for sputum aspiration in patients with acute respiratory distress syndrome on lung recruitment

Abstract

To investigate the effect of different degrees of pressure of sustained inflation (SI) in patients with acute respiratory distress syndrome (ARDS) after lung recruitment as the result of different negative pressure for sputum aspiration. A prospective single-blind randomized controlled trial was conducted. The factorial analysis of variance was adopted. 150 patients with ARDS admitted to the emergency intensive care unit (ICU) of Chongqing Three Gorges Central Hospital from January 2012 to December 2014 were enrolled, and they were randomly divided into S1, S2, S3 group, with 50 patients in each group, suction pressure varying from 150, 175, to 200 mmHg (1 mmHg=0.133 kPa) was respectively used in each group. Then the patients of each group were randomly subdivided into five subgroups of P0, P1, P2, P3, P4, with 10 patients in each group, and 0, 30, 35, 40, and 45 cmH2O (1 cmH2O=0.098 kPa) were used for control pulmonary inflation pressure, respectively. The respiratory mechanics and the hemodynamic parameters were recorded, and they were compared before and after the sputum aspiration as well as lung recruitment with sustained inflation. The lung recruitment volume (mL: 87.56±28.47 vs. 109.38±34.63, t=3.573, P=0.001) and lung static compliance [Cst (mL/cmH2O): 27.69±13.25 vs. 35.87±17.47, t=2.814, P=0.004] after sputum aspiration in the 150 patients were significantly lower than those before the sputum aspiration, and peak airway pressure [PIP (cmH2O): 24.16±8.28 vs. 18.63±6.67, t=2.957, P=0.005], airway plateau pressure [Pplat (cmH2O): 21.28±9.14 vs. 17.47±7.26, t=2.089, P=0.032], and mean airway pressure [Pm (cmH2O): 13.26±4.65 vs. 10.41±3.54, t=3.271, P=0.001] were significantly higher than those before the treatment. There were no significant differences in the lung recruitment volume, Cst, PIP, Pplat and Pm between groups with different negative pressure for sputum aspiration (F value was 0.809, 0.986, 1.121, 0.910, 1.043, and P value was 0.452, 0.381, 0.335, 0.410, 0.361), but statistical significance was found among different groups of different lung recruitment pressures (F value was 3.581, 5.028, 3.064, 3.036, 4.050, and P value was 0.013, 0.002, 0.026, 0.027, 0.007). There was no interaction between the two factors. After pairwise comparison, under the same negative pressure for sputum aspiration, lung recruitment volume and Cst in different lung recruitment pressures subgroups (P1, P2, P3, P4) were significantly higher than those of P0 subgroup, and PIP, Pplat, and Pm were significantly lower than those of P0 subgroup. There was no significant difference among P1, P2, P3 and P4 groups. There were no significant differences in mean arterial pressure (MAP) and pulmonary arterial pressure (PAP) among different groups with negative pressures for sputum aspiration and different lung recruitment pressures (negative pressure for sputum aspiration: F=0.586, P=0.561, F=1.373, P=0.264; lung recruitment pressure: F=1.313, P=0.280, F=1.621, P=0.186), there was no interaction between the two factors (F=0.936, P=0.497, F=1.391, P=0.227). The difference of heart rate (HR) in different negative pressure for sputum aspiration groups was not significant (F=1.144, P=0.328), and there were significant differences in different lung recruitment pressure groups (F=3.297, P=0.019), there was no interaction between the two factors (F=1.277, P=0.280). After pairwise comparison, under the same negative pressure for sputum aspiration, HR in P3 and P4 subgroups was significantly higher than that in P0, P1, and P2 subgroups (all P<0.05). 30 cmH2O and 35 cmH2O were the suitable pressure for SI in ARDS patients, and they were not affected by different negative pressure for sputum aspiration.