[Continuous prone position ventilation in patients with severe acute respiratory distress syndrome at high altitude]

To investigate the therapeutic effect of different prone position ventilation (PPV) on patients with severe acute respiratory distress syndrome (ARDS) at high altitude.

The severe ARDS patients who met the Berlin standard admitted to the department of intensive care unit (ICU) of Qinghai Provincial People's Hospital from January 2017 to January 2020 were enrolled. The patients with classic PPV treatment (i.e. alternate prone supine position, about 16 hours per day) were included in the discontinuous PPV group; the patients with modified PPV treatment (i.e. alternate left and right prone positions 20 degree angle-30 degree angle, every 4 hours and continuous treatment for 24 hours per day) were included in the continuous PPV group. The oxygenation index (PaO₂/FiO₂), mechanics of breathing, ventilator parameters before treatment and 72 hours after treatment, and mechanical ventilation time, the length of ICU stay, and related complications between the two groups were analyzed.

Eighteen cases were treated with continuous PPV and 20 cases were treated with discontinuous PPV. There were no significant differences in gender, age, acute physiology and chronic health evaluation II (APACHE II), PaO₂/FiO₂, lung compliance, driving pressure (ΔP) and positive end expiratory pressure (PEEP) before treatment between the two groups. Compared with before treatment, PaO₂/FiO₂ in discontinuous PPV group and continuous PPV group was increased significantly after 72-hour treatment [mmHg (1 mmHg = 0.133 kPa): 99.7±15.4 vs. 55.5±6.3, 121.8±25.3 vs. 55.1±7.1, both P < 0.05], lung compliance was improved significantly (mL/cmH₂O: 36.8±2.4 vs. 28.0±2.0, 43.4±6.7 vs. 27.7±2.1, both P < 0.05), and ΔP was decreased significantly [cmH₂O (1 cmH₂O = 0.098 kPa): 10.5 (10.0, 12.0) vs. 13.0 (12.3, 14.0), 10.0 (8.0, 12.0) vs. 13.0 (12.0, 14.0), both P < 0.05], PEEP was also decreased [cmH₂O: 12 (12, 14) vs. 14 (13, 14), 10 (8, 10) vs. 14 (12, 15), both P < 0.05], and the indexes in continuous PPV group were improved more significantly than those in discontinuous PPV group [PaO₂/FiO₂ (mmHg): 121.8±25.3 vs. 99.7±15.4, lung compliance (mL/cmH₂O): 43.4±6.7 vs. 36.8±2.4, ΔP (cmH₂O): 10.0 (8.0, 12.0) vs. 10.5 (10.0, 12.0), PEEP (cmH₂O): 10 (8, 10) vs. 12 (12, 14), all P < 0.05]. The duration of mechanical ventilation and the length of ICU stay in the continuous PPV group were significantly shorter than those in the intermittent PPV group [days: 6.0 (5.0, 7.3) vs. 8.0 (7.0, 9.0), 9.7±1.5 vs. 12.1±2.2, both P < 0.01]. During the PPV treatment, there were 3 cases of cheek skin damage and 2 cases of ear skin damage in the continuous PPV group, and 3 cases of facial skin damage in the intermittent PPV group. There was no significant difference in the incidence of complications between the two groups (χ² = 0.321, P = 0.571). All patients were repaired normally after PPV, without adverse consequences.

Continuous PPV is more effective than discontinuous PPV in the treatment of severe ARDS patients at high altitude, and the related complications are did not increased in prolonged time of PPV.