title: The effects of oxygen induced pulmonary vasoconstriction on bedside measurement of pulmonary gas exchange.
abstract: In patients with respiratory failure measurements of pulmonary gas exchange are of importance. The bedside automatic lung parameter estimator (ALPE) of pulmonary gas exchange is based on changes in inspired oxygen (FiO2) assuming that these changes do not affect pulmonary circulation. This assumption is investigated in this study. Forty-two out of 65 patients undergoing coronary artery bypass grafting (CABG) had measurements of mean pulmonary arterial pressure (MPAP), cardiac output and pulmonary capillary wedge pressure thus enabling the calculation of pulmonary vascular resistance (PVR) at each FiO2 level. The research version of ALPE was used and FiO2 was step-wise reduced a median of 0.20 and ultimately returned towards baseline values, allowing 6-8 min' steady state period at each of 4-6 levels before recording the oxygen saturation (SpO2). FiO2 reduction led to median decrease in SpO2 from 99 to 92 %, an increase in MPAP of 4 mmHg and an increase in PVR of 36 dyn s cm(-5). Changes were immediately reversed on returning FiO2 towards baseline. In this study changes in MPAP and PVR are small and immediately reversible consistent with small changes in pulmonary gas exchange. This indicates that mild deoxygenation induced pulmonary vasoconstriction does not have significant influences on the ALPE parameters in patients after CABG.
authors.affiliation: Department of Respiratory Diseases, Aalborg University Hospital, Mølleparkvej 4, 9000, Aalborg, Denmark. ulw@rn.dk.|Respiratory and Critical Care Group (RCARE), Centre for Model Based Medical Decision Support Systems, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark. ulw@rn.dk.|The Clinical Institute, Aalborg University Hospital, Aalborg, Denmark. ulw@rn.dk.
authors.forename: Ulla M
authors.identifier: http://orcid.org/0000-0003-1975-3654
authors.initials: UM
authors.lastname: Weinreich
authors.affiliation: Respiratory and Critical Care Group (RCARE), Centre for Model Based Medical Decision Support Systems, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Lars P
authors.initials: LP
authors.lastname: Thomsen
authors.affiliation: Respiratory and Critical Care Group (RCARE), Centre for Model Based Medical Decision Support Systems, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Rees
authors.affiliation: The Clinical Institute, Aalborg University Hospital, Aalborg, Denmark.|Department of Anaesthesia and Intensive Care Medicine, Aalborg University Hospital, Aalborg, Denmark.|Centre of Cardiovascular Research, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Bodil S
authors.initials: BS
authors.lastname: Rasmussen
mesh_terms: D000368:Aged; D001944:Breath Tests / Q000379:methods; D006801:Humans; D008875:Middle Aged; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D011651:Pulmonary Artery / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D011669:Pulmonary Wedge Pressure / Q000502:physiology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods; D012680:Sensitivity and Specificity; D014655:Vascular Resistance / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: FiO2; Hypoxia; Hypoxic pulmonary vasoconstriction; Mean pulmonary arterial pressure; Oxygen; Pulmonary vascular resistance