title: Changes in respiratory mechanics during cardiac surgery.
abstract: We investigated the role of cardiopulmonary bypass (CPB) in compromised lung function associated with cardiac surgery. Low-frequency respiratory impedance (Zrs) was measured in patients undergoing cardiac surgery with (n = 30; CPB group) or without (n = 29; off-pump coronary artery bypass [OPCAB] group) CPB. Another group of CPB patients received dopamine (DA) (n = 12; CPB-DA group). Extravascular lung water was determined in five CPB subjects. Zrs was measured before skin incision and after chest closure. Airway resistance and inertance and tissue damping and elastance were determined from Zrs data. Airway resistance increased in the CPB group (74.9% +/- 20.8%; P < 0.05), whereas it did not change in the OPCAB group (11.8% +/- 7.9%; not significant) and even decreased in the CPB-DA patients (-40.6% +/- 9.2%; P < 0.05). Tissue damping increased in the CPB and OPCAB groups, whereas it remained constant in the CPB-DA patients. Significant increases in elastance were observed in all groups. There was no difference in extravascular lung water before and after CPB, suggesting that edema did not develop. These results indicate a significant and heterogeneous airway narrowing during CPB, which was counteracted by the administration of DA. The mild deterioration in tissue mechanics, reflecting partial closure of the airways, may be a consequence of the anesthesia itself.
  
  
  CONCLUSIONS
  We observed that cardiopulmonary bypass deteriorates lung function by inducing a heterogeneous airway constriction, whereas no such effects were observed in patients undergoing cardiac surgery without bypass. The impairment in parenchymal mechanics, which was obtained in both groups, may result from peripheral airway closure and/or be a consequence of mediator release.
authors.affiliation: *Institute of Anesthesiology and Intensive Therapy, †Division of Cardiac Surgery, and ‡Department of Medical Informatics and Engineering, University of Szeged, Szeged, Hungary.
authors.forename: Barna
authors.initials: B
authors.lastname: Babik
authors.forename: Tibor
authors.initials: T
authors.lastname: Asztalos
authors.forename: Ferenc
authors.initials: F
authors.lastname: Peták
authors.forename: Zoltán I
authors.initials: ZI
authors.lastname: Deák
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Hantos
mesh_terms: D000328:Adult; D000368:Aged; D000403:Airway Resistance / Q000502:physiology; D000465:Algorithms; D000704:Analysis of Variance; D000758:Anesthesia; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D015331:Cohort Studies; D003250:Constriction; D015633:Extravascular Lung Water / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011229:Preanesthetic Medication; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D014132:Trachea / Q000502:physiology