Morphological Assessment of the Safety of Alveolar Opening

Abstract

Objective: The safety of an alveolar mobilization technique was morphologically evaluated. Materials and methods. Experiments were made on 46 non-inbred albino male rats weighing 280—320 g. Thiopental sodium (15—20 mg/kg animal weight) was intraperitoneally injected for anesthesia. A TSE Animal Respirator was employed for 30—180 minutes. In the first experimental animal group, the ventilation parameters were as follows: air flow 0.4—0.5 l/min; respiration rate 60 per min; tidal volume 1—5 ml; PEEP (during alveolar opening) 40 cm H2O (40 seconds); PEEP (after recruitment) 10 cm H2O (20 minutes). Recruitment was carried out at 20-minute intervals for 1—3 hours. Experimental Group 2 animals underwent artificial ventilation (AV) with the following ventilation parameters: air flow 0.4—0.5 l/min; respiration rate 60 per min; tidal volume 1—5 ml; PEEP (during alveolar opening) 20 cm H2O (20 seconds); PEEP (after recruitment) 10 cm H2O (20 minutes). The control animals had AV with the ventilation parameters: air flow 0.4—0.5 l/min; respiration rate 60 per min; tidal volume 1—5 ml; PEEP 0 cm H2O. Lung pieces were fixed in 10% neutral formalin solution and embedded in paraffin. The histological specimens were stained with hematoxylin and eosin; the Schick test was carried out. Results. Histological study of the lung from the experimental group animals has shown dilated alveoli and bronchioli. The increased alveolar volume at a high air flow and PEEP leads to air-blood barrier damage, alveolar septal infiltration with leukocytes, neutrophils, and macrophages, and to the development of interstitial and alveolar edema. Lung morphological changes were less pronounced in the animals from the second experimental group. Conclusion. The alveolar opening technique improves gas exchange parameters, as evidenced by oxygen utilization. The high PEEP values are attended by more significant lung morphological changes. Key words: alveolar recruitment, open lungs, PEEP.