Post-operative atelectasis - a randomised trial investigating a ventilatory strategy and low oxygen fraction during recovery.
BACKGROUND
Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy with a combination of 1) continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and 2) a reduced end-expiratory oxygen concentration during recovery would reduce post-operative atelectasis.


METHODS
Sixty patients were randomized into two groups. During anaesthesia induction, inspiratory oxygen fraction (FIO2) was 1.0, and depending on weight, CPAP 6, 7 or 8 cmH2O was applied in both groups via facemask. During maintenance of anaesthesia, a laryngeal mask airway (LMA) was used, and PEEP was 6-8 cmH2O in both groups. Before removal of the LMA, FIO2 was set to 0.3 in the intervention group and 1.0 in the control group. Atelectasis was studied by computed tomography (CT) approximately 14 min post-operatively.


RESULTS
In one patient in the group given an FIO2 of 0.3 before removal of the LMA a CT scan could not be performed so the patient was excluded. The area of atelectasis was 5.5, 0-16.9 cm(2) (median and range), and 6.8, 0-27.5 cm(2) in the groups given FIO2 0.3 or FIO2 1.0 before removal of the LMA, a difference that was not statistically significant (P = 0.48). Post-hoc analysis showed dependence of atelectasis on smoking (despite all were clinically lung healthy) and American Society of Anesthesiologists class (P = 0.038 and 0.015, respectively).


CONCLUSIONS
Inducing anaesthesia with CPAP/PEEP and FIO2 1.0 and deliberately reducing FIO2 during recovery before removal of the LMA did not reduce post-operative atelectasis compared with FIO2 1.0 before removal of the LMA.
Department of Anaesthesiology and Intensive Care, Västmanlands sjukhus Köping, Köping, Sweden; Department of Medical Sciences, Clinical Physiology, Uppsala University, Uppsala, Sweden.
L
L
Edmark
U
U
Auner
J
J
Lindbäck
M
M
Enlund
G
G
Hedenstierna
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000556:Ambulatory Surgical Procedures; D000762:Anesthesia Recovery Period; D000768:Anesthesia, General; D000772:Anesthesia, Local; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D000077324:Crystalloid Solutions; D005260:Female; D006801:Humans; D007552:Isotonic Solutions / Q000008:administration & dosage; D017214:Laryngeal Masks; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D019637:Orthopedic Procedures; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000517:prevention & control*; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging / Q000517:prevention & control*; D065589:Respiratory Tract Absorption; D014057:Tomography, X-Ray Computed
D000077324:Crystalloid Solutions; D007552:Isotonic Solutions; D010100:Oxygen