title: Compressing the non-dependent lung during one-lung ventilation improves arterial oxygenation, but impairs systemic oxygen delivery by decreasing cardiac output.
abstract: OBJECTIVE
  We have previously found that compression of the non-dependent lung improves arterial oxygenation during one-lung ventilation (OLV) in patients undergoing esophagectomy. The purpose of this study was to investigate the effects of compression of the non-dependent lung on hemodynamic indices and oxygen delivery using a minimally invasive cardiac output (CO) monitor.
  
  
  METHODS
  Sixteen consecutive patients undergoing esophagectomy through a right thoracotomy were studied. Under general anesthesia, a left-sided double-lumen tube was placed for OLV, and the dependent lung was mechanically ventilated with a tidal volume of 8 ml kg(-1) body weight and a fraction of inspiratory oxygen of 0.8 during OLV. CO was monitored continuously using a FloTrac/Vigileo (Edwards Lifesciences) system. Surgeons compressed the non-dependent lung several times during surgery using a lung retractor to improve exposure of the surgical field. The oxygen delivery index was roughly estimated as the product of the cardiac index (CI) and arterial oxygen saturation as monitored by pulse oximetry (Spo2).
  
  
  RESULTS
  Just before non-dependent lung compression, mean (+/- SD) CI and Spo2 were 2.6 +/- 0.6 L min(-1) m(-2) and 95.0 +/- 3.9%, respectively. At 1 min after non-dependent lung compression, Spo2 increased significantly to 97.8 +/- 2.2% (P < 0.05), but CI decreased significantly to 2.0 +/- 0.4 L min(-1) m(-2) (P < 0.05). The product of CI and Spo2 at 1 min was significantly lower (192.7 +/- 37.3) than baseline levels (250.5 +/- 66.3, P < 0.05).
  
  
  CONCLUSIONS
  Although non-dependent lung compression may be a potentially effective measure to treat hypoxemia during OLV, it should be noted that CO and systemic oxygen delivery may be decreased by this maneuver.
authors.affiliation: Department of Anesthesiology, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. ishikawa.mane@tmd.ac.jp
authors.forename: Seiji
authors.initials: S
authors.lastname: Ishikawa
authors.forename: Madoka
authors.initials: M
authors.lastname: Shirasawa
authors.forename: Michiko
authors.initials: M
authors.lastname: Fujisawa
authors.forename: Tatsuyuki
authors.initials: T
authors.lastname: Kawano
authors.forename: Koshi
authors.initials: K
authors.lastname: Makita
mesh_terms: D000368:Aged; D002302:Cardiac Output / Q000502:physiology*; D016629:Esophagectomy; D005260:Female; D006439:Hemodynamics; D006801:Humans; D000860:Hypoxia / Q000517:prevention & control*; D007430:Intraoperative Care / Q000009:adverse effects / Q000379:methods; D008168:Lung / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D013908:Thoracotomy; D013997:Time Factors
chemical_list: D010100:Oxygen