title: Ventilation with increased apparatus dead space vs positive end-expiratory pressure: effects on gas exchange and circulation during anesthesia in a randomized clinical study.
abstract: Atelectasis formation can be reduced by positive end-expiratory pressure (PEEP), but resulting increases in intrathoracic pressure could affect circulation. We have earlier demonstrated that increased tidal volumes with larger apparatus dead space improves oxygenation and sevoflurane uptake. In the present study, we hypothesize that isocapnic ventilation with increased tidal volumes increases oxygen and sevoflurane uptake similar to ventilation with PEEP, but with less impact on cardiac output. Thirty patients, with ASA physical status 1 or 2, scheduled for elective open colon surgery were randomly assigned to be ventilated with either PEEP at 10 cm H20 (PEEP, 15 patients) or increased tidal volumes achieved with larger apparatus dead space but with zero end-expiratory pressure (DS group, 15 patients). Oxygen tension and arterial sevoflurane concentration were significantly higher in the DS group (P < .05). Cardiac output decreased significantly less in the DS group compared with the PEEP group (5% and 33%, respectively; P < .05). Consequently, isocapnic ventilation with increased tidal volumes using apparatus dead space increased oxygen and sevoflurane tensions in arterial blood and preserved cardiac output better than did PEEP.
authors.forename: Bruno
authors.initials: B
authors.lastname: Enekvist
authors.forename: Mikael
authors.initials: M
authors.lastname: Bodelsson
authors.forename: Michelle
authors.initials: M
authors.lastname: Chew
authors.forename: Anders
authors.initials: A
authors.lastname: Johansson
mesh_terms: D000368:Aged; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics; D002302:Cardiac Output; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000493:pharmacokinetics*; D008875:Middle Aged; D009719:Nurse Anesthetists; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012126:Respiratory Dead Space; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane