Effects of PEEP on Residual Vascularization in Oesophageal Substitution Gastroplasty by Surface Oximetry-Capnometry and Photoplethysmography

Abstract

Objective: To evaluate the effects of positive end-expiratory pressure (PEEP) on residual vascularization in gastric tubes for oesophageal replacement. Design: Experimental open study. Materials: Eleven mongrel dogs. Methods: Intestinal parietal blood flow was evaluated by photoplethysmography (PPG) and measurement of surface oxygen (PsO₂) and carbon dioxide (PsCO₂) tensions under basal conditions. After Akiyama’s tubular gastroplasty, three levels of PEEP were administered. At each level, fluids were infused to counter the drop in cardiac output. PPG, surface gas tensions, arterial pressure, cardiac output and arterial blood gas tensions were monitored. Control sections of the bowel were also monitored by PPG. Results: Cardiac output dropped for each level of PEEP and returned to basal levels on volume restabilization and on removal of PEEP. Central venous pressure and pulmonary arterial and capillary pressures increased for each level of PEEP and only returned to basal levels on removal of PEEP. PsO₂ values dropped for each level of PEEP and returned to basal levels on volume restabilization and on removal of PEEP. PsCO₂ levels rose, and PPG wave amplitude dropped, for each level of PEEP; these two variables only returned to basal levels on removal of PEEP. PPG values for the control sections reflected those of the anastomotic area. Conclusions: PEEP affects surface oxygen values at the level of the gastroplasty by means of its effect on cardiac output. PEEP also creates a venous return compromise and PPG wave amplitude and surface carbon dioxide values are related to this compromise. All three variables could be significant in anastomotic wound healing.