Biphasic positive airway pressure spontaneous breathing attenuates lung injury in an animal model of severe acute respiratory distress syndrome

Abstract

Objective: To compare the effects of unassisted spontaneous breathing (SB) and complete muscle paralysis (PC) on early severe acute respiratory distress syndrome (ARDS) in an animal model, and to explore the possibility of biphasic positive airway pressure (BIPAP) as lung protective ventilation support for patients in the early stage of severe ARDS.

Methods: Twelve healthy beagle dogs between the ages of 10 and 15 months were randomly divided into two groups: the SB group (BIPAP_SB) and the PC group (BIPAP_PC). Arterial blood samples were drawn before modelling. Arterial blood gas analysis and mechanical tests were conducted. The animal model of severe ARDS was established using a deep intravenous injection of oleic acid, and BIPAP ventilation was performed for 8 hours. Lung tissue and blood were taken to detect lung function, inflammatory reactions and degree of pathological damage.

Results: At the beginning of the experiment, there was no significant difference in the arterial blood gas analysis between the two groups (p > 0.05). After successful modelling, the oxygenation index and the end-expiratory lung volume in the SB group were significantly higher than those in the PC group 8 hours after MV. Pathologically, the wet-dry ratio and pathological score of the PC group were higher than those of the SB group; the lung injury in the gravity-dependent area in the SB group was less than that in the PC group (p< 0.05).

Conclusions: In the early stage of severe ARDS induced by oleic acid, compared with PC, retention of the BIPAP mode of SB can reduce the risk of lung injury and improve respiratory function.

Keywords: Acute respiratory distress syndrome; Biphasic positive airway pressure; Inspiratory muscles; Neuromuscular blocker; Spontaneous breathing.

Fig. 1

Representative respiratory tracings of airway pressure (Paw), esophageal pressure (Pes), intragastric pressure (Pgas), transpumonary pressure (PL), Airflow, abdominal muscles surface electromyography (EMGab) and diaphragmatic esophageal surface electromyography (EMGdi) in BIPAP_SB, BIPAP_PC group in representative animals. BIPAP_SB = biphasic positive airway pressure with spontaneous breathing, SB efforts were regained; BIPAP_PC = biphasic positive airway pressure with muscles paralysis, Animals’ SB efforts were fully depressed. Therefore, BIPAP was equal to pressure-controlled ventilation

Fig. 2

Time course of the end expiratory lung volume (EELV) and VD/VT in experimental groups (n = 6 per group). N=Pre-modeled animal model; BIPAP_SB = biphasic positive airway pressure with spontaneous breathing; BIPAP_PC = biphasic positive airway pressure with muscles paralysis; *p< 0.05, vs. BIPAP_SB group

Fig. 3

The Levels of interleukin (IL)-6 and IL-8 in plasma after 8 h mechanical ventilation. BIPAP_SB = biphasic positive airway pressure with spontaneous breathing; BIPAP_PC = biphasic positive airway pressure with muscles paralysis

Fig. 4

The Levels of Wet to dry weight ratio (W/D) after 8 h mechanical ventilation. BIPAP_SB = biphasic positive airway pressure with spontaneous breathing; BIPAP_PC = biphasic positive airway pressure with muscles paralysis;*p< 0.05 vs. BIPAP_SB

Fig. 5

Representative appearances and photomicrographs of hematoxylineosin stained lung sections (magnification× 400) from in BIPAP_SB (A), BIPAP_PC group(B) in representative animals. BIPAP_SB = biphasic positive airway pressure with SB; BIPAP_PC = biphasic positive airway pressure with muscles paralysis