title: Effects on lung function in patients undergoing coronary artery surgery on versus off cardiopulmonary bypass: a randomized trial.
abstract: BACKGROUND
  : Coronary revascularization is associated with respiratory dysfunction and poor gas exchange postoperatively. Cardiopulmonary bypass (CPB) has been implicated as a possible explanation for this phenomenon. This study investigated respiratory function in patients undergoing coronary artery bypass grafting (CABG) on-CPB versus off-CPB to determine whether the off-CPB condition results in improved postoperative pulmonary function.
  
  
  METHODS
  : Forty patients were randomized into 1 of 2 groups: CABG on-CPB (group A) or off-CPB (group B). Pulmonary function tests, including spirometry and diffusion studies, were performed preoperatively and on postoperative day 5. Arterial blood gases on 100% oxygen were taken preoperatively (TP1), 15 minutes after sternal closure (TP2), and 3 hours postoperatively (TP3).
  
  
  RESULTS
  : The arterial partial pressure of oxygen (PaO2) on FiO2 1.0 decreased from 59.5 ± 11.5 kPa and 55.7 ± 12.2 kPa at TP1 to 39.5 ± 16 kPa and 39.7 ± 13 kPa at TP2 in groups A and B, respectively (P < 0.001), with no significant difference between groups. At TP3, the PaO2 partially recovered toward preoperative levels (P > 0.05).Spirometry revealed a significant reduction in FEV1 and FVC on the fifth postoperative day (P < 0.001), with no significant difference between groups. The corrected transfer factor for carbon monoxide reduced significantly in group A from 7.9 ± 2.5 mmol·min · kPa preoperatively to 5.1 ± 1.6 mmol·min · kPa postoperatively (P < 0.05). This reduction was not seen in group B.
  
  
  CONCLUSIONS
  : Coronary artery surgery is associated with a marked reduction in lung function as measured by pulmonary function tests and PaO2. Diffusion studies revealed that on-CPB patients had significantly reduced diffusion capacities postoperatively compared with patients in the off-CPB group.
authors.affiliation: From the *Cardiothoracic Department and †Vascular Surgery Department, St. George's Hospital, London, UK.
authors.forename: Gunaratnam
authors.initials: G
authors.lastname: Niranjann
authors.forename: George
authors.initials: G
authors.lastname: Asimakopoulos
authors.forename: Brendan
authors.initials: B
authors.lastname: Madden
authors.forename: Gillian
authors.initials: G
authors.lastname: Cockerill
authors.forename: Matthew
authors.initials: M
authors.lastname: Thompson
authors.forename: Venkatachalam
authors.initials: V
authors.lastname: Chandrasekaran