Monitoring of respiratory function before and after cardiopulmonary bypass using side-stream spirometry

Abstract

Pulmonary impairment is more frequent after cardiac surgery than after other major surgical procedures. The present study investigates whether, by using standard respiratory monitoring, i.e. side-stream spirometry and blood gas analysis, it is possible to detect changes in pulmonary function secondary to cardiopulmonary bypass. We investigated 18 patients undergoing elective coronary bypass surgery or aortic valve replacement. Cardiopulmonary bypass resulted in a nonsignificant increase in alveolar-arterial oxygen difference from 33.0 +/- 10.6 kPa to 36.1 +/- 12.5 kPa and arterial to end-tidal CO2 tension difference from 0.67 +/- 0.39 kPa to 0.79 +/- 0.54 kPa. Respiratory system resistance was unaltered. In contrast, dynamic compliance decreased significantly after cardiopulmonary bypass from 78.6 +/- 22.9 to 65.4 +/- 22.4 mL cmH2O-1 with open chest and from 61.0 +/- 10.2 to 51.1 +/- 17.2 mL cmH2O-1 with closed chest, compared with corresponding values before cardiopulmonary bypass. In conclusion, pulmonary gas exchange was not compromised after cardiopulmonary bypass, but a diminished respiratory compliance was a consistent finding, even in uncomplicated cardiac surgery using routine respiratory monitoring.

Respiratory mechanics with volume-controlled auto-flow ventilation mode in cardiac surgery*

“…Cardiac surgery could provoke pulmonary dysfunction as a result of sternotomy,[ 11 ] dissection of mammarian artery,[ 12 ] increase in extravascular lung volume, and leukocyte sequestration in alveolar microcirculation. [ 1 ] Additionally, CPB causes structural and functional damages in the pulmonary endothelium[ 13 ] and results in lung dysfunction. [ 14 ]…”

“…Consequently, these changes result in more oxygen consumption in cardiac patients. [ 1 15 ] Thus, prevention of these undesired changes in respiratory mechanics is aimed during the perioperative period. [ 1 5 8 16 ]…”

“…In most of the previous studies, respiratory mechanics were investigated during VC ventilation mode,[ 1 3 4 5 8 9 16 17 ] and different strategies have been designed for prevention of postoperative pulmonary dysfunction in cardiac patients. [ 3 8 9 16 18 ] A-Meguid et al .…”

“…Long-term general anesthesia, intrathoracic surgical manipulation, and cardiopulmonary bypass (CPB) may lead to significant changes in respiratory functions of patients during open heart surgery (OHS). [ 1 2 ] These changes are mainly related to respiratory mechanics,[ 3 4 5 ] lung volumes,[ 6 ] ventilation–perfusion ratio,[ 7 ] and gas exchange. [ 8 ]…”

“…Respiratory mechanics were investigated during surgeries of coronary artery bypass grafting (CABG) and aortic valve replacement in adult patients[ 1 3 8 ] and during congenital cardiac surgery in pediatric patients,[ 5 9 ] mainly using the volume-controlled (VC) ventilation mode. [ 1 3 4 8 ] However, data related to volume-controlled auto-flow (VCAF) ventilation mode were not investigated previously. This ventilation mode may have beneficial and/or protective effects on respiratory mechanics.…”