Pressure-controlled ventilation does not improve gas exchange in morbidly obese patients undergoing abdominal surgery.
BACKGROUND
Morbid obesity results in marked respiratory pathophysiologic changes that may lead to impaired intraoperative gas exchange. The decelerating inspiratory flow and constant inspiratory airway pressure resulting from pressure-controlled ventilation (PCV) may be more adapted to these changes and improve gas exchanges compared with volume-controlled ventilation (VCV).


METHODS
Forty morbidly obese patients scheduled for gastric bypass were included in this study. Total intravenous anesthesia was given using the target-controlled infusion technique. During the first intraoperative hour, VCV was used and the tidal volume was adjusted to keep end-tidal PCO(2) around 35 mmHg. After 1 h, patients were randomly allocated to 30-min VCV followed by 30-min PCV or the opposite sequence using a Siemens Servo 300. FiO(2) was 0.6. During PCV, airway pressure was adjusted to provide the same tidal volume as during VCV. Arterial blood was sampled for gas analysis every 15 min. Ventilatory parameters were also recorded.


RESULTS
Peak inspiratory airway pressures were significantly lower during PCV than during VCV (P < 0.0001). The other ventilatory parameters were similar during the two periods of ventilation. PaO(2) and PaCO(2) were not significantly different during PCV and VCV.


CONCLUSIONS
PCV does not improve gas exchange in morbidly obese patients undergoing gastric bypass compared to VCV.
Hans
Gregory A
GA
Department of Anesthesia and Intensive Care Medicine, CHU de Liège, University of Liège, Domaine du Sart Tilman, 4000, Liège, Belgium.
Prégaldien
Audrey A
AA
Kaba
Abdourahamane
A
Sottiaux
Thierry M
TM
DeRoover
Arnaud
A
Lamy
Maurice L
ML
Joris
Jean L
JL
D000005:Abdomen / Q000601:surgery; D000328:Adult; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000503:physiopathology / Q000601:surgery*; D001261:Pulmonary Atelectasis / Q000517:prevention & control; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012121:Respiration, Artificial / Q000379:methods*