title: Re-expansion of atelectasis during general anaesthesia: a computed tomography study.
abstract: Formation of atelectasis is one mechanism of impaired gas exchange during general anaesthesia. We have studied manoeuvres to re-expand such atelectasis in 16 consecutive, anaesthetized adults with healthy lungs. In group 1 (10 patients), the lungs were inflated stepwise to an airway pressure (Paw) of 10, 20, 30 and 40 cm H2O. In group 2 (six patients), three repeated inflations up to Paw = 30 cm H2O were followed by one inflation to 40 cm H2O. Atelectasis was assessed by analysis of computed x-ray tomography (CT). In group 1 the mean area of atelectasis in the CT scan at the level of the right diaphragm was 6.4 cm2 at Paw = 0 cm H2O, 5.9 cm2 at 20 cm H2O, 3.5 cm2 at 30 cm H2O and 0.8 cm2 at 40 cm H2O. A Paw of 20 cm H2O corresponds approximately to inflation with twice the tidal volume. In group 2 the mean area of atelectasis was 9.0 cm2 at Paw = 0 cm H2O and 4.2 cm2 after the first inflation to 30 cm H2O. Repeated inflations did not add to re-expansion of atelectasis. The final inflation (Paw = 40 cm H2O) virtually eliminated the atelectasis. We conclude that, after induction of anaesthesia, the amount of atelectasis was not reduced by inflation of the lungs with a conventional tidal volume or with a double tidal volume ("sigg"). An inflation to vital capacity (Paw = 40 cm H2O), however, re-expanded virtually all atelectatic lung tissue.
authors.affiliation: Department of Anaesthesiology and Intensive Care, University Hospital, Uppsala, Sweden.
authors.forename: H U
authors.initials: HU
authors.lastname: Rothen
authors.forename: B
authors.initials: B
authors.lastname: Sporre
authors.forename: G
authors.initials: G
authors.lastname: Engberg
authors.forename: G
authors.initials: G
authors.lastname: Wegenius
authors.forename: G
authors.initials: G
authors.lastname: Hedenstierna
mesh_terms: D000328:Adult; D000768:Anesthesia, General / Q000009:adverse effects*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging / Q000209:etiology / Q000628:therapy*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012121:Respiration, Artificial; D014057:Tomography, X-Ray Computed