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Oxygen and anesthesia: what lung do we deliver to the post‐operative ward?
Author(s) -
HEDENSTIERNA G.
Publication year - 2012
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.2012.02689.x
Subject(s) - medicine , atelectasis , anesthesia , functional residual capacity , hypoxemia , oxygenation , continuous positive airway pressure , positive end expiratory pressure , airway , pulmonary compliance , lung , lung volumes , mechanical ventilation , obstructive sleep apnea
Anesthesia is safe in most patients. However, anesthetics reduce functional residual capacity ( FRC ) and promote airway closure. Oxygen is breathed during the induction of anesthesia, and increased concentration of oxygen ( O 2 ) is given during the surgery to reduce the risk of hypoxemia. However, oxygen is rapidly adsorbed behind closed airways, causing lung collapse (atelectasis) and shunt. Atelectasis may be a locus for infection and may cause pneumonia. Measures to prevent atelectasis and possibly reduce post‐operative pulmonary complications are based on moderate use of oxygen and preservation or restoration of FRC . Pre‐oxygenation with 100% O 2 causes atelectasis and should be followed by a recruitment maneuver (inflation to an airway pressure of 40 cm H 2 O for 10 s and to higher airway pressures in patients with reduced abdominal compliance (obese and patients with abdominal disorders). Pre‐oxygenation with 80% O 2 may be sufficient in most patients with no anticipated difficulty in managing the airway, but time to hypoxemia during apnea decreases from mean 7 to 5 min. An alternative, possibly challenging, procedure is induction of anesthesia with continuous positive airway pressure/positive end‐expiratory pressure to prevent fall in FRC enabling use of 100% O 2 . A continuous PEEP of 7–10 cm H 2 O may not necessarily improve oxygenation but should keep the lung open until the end of anesthesia. Inspired oxygen concentration of 30–40%, or even less, should suffice if the lung is kept open. The goal of the anesthetic regime should be to deliver a patient with no atelectasis to the post‐operative ward and to keep the lung open.