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Capillary PO2 does not adequately reflect arterial PO2 in hypoxemic COPD patients

Authors Magnet FS, Majorski DS, Callegari J, Schwarz SB, Schmoor C, Windisch W, Storre JH

Received 1 May 2017

Accepted for publication 19 June 2017

Published 6 September 2017 Volume 2017:12 Pages 2647—2653


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 2

Editor who approved publication: Dr Richard Russell

Friederike Sophie Magnet,1 Daniel Sebastian Majorski,1 Jens Callegari,1 Sarah Bettina Schwarz,1 Claudia Schmoor,2 Wolfram Windisch,1 Jan Hendrik Storre3,4

1Department of Pneumology, Cologne Merheim Hospital, Kliniken der Stadt Köln gGmbH Witten/Herdecke University, Faculty of Health/School of Medicine, Cologne, Germany; 2Clinical Trials Unit, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany; 3Department of Intensive Care, Sleep Medicine and Mechanical Ventilation, Asklepios Fachkliniken Munich-Gauting, Gauting, Germany; 4Department of Pneumology, University Medical Hospital, Freiburg, Germany

Purpose: To compare arterial (PaO2) with capillary (PcO2) partial pressure of oxygen in hypoxemic COPD patients because capillary blood gas analysis (CBG) is increasingly being used as an alternative to arterial blood gas analysis (ABG) in a non-intensive care unit setting, although the agreement between PcO2 and PaO2 has not been evaluated in hypoxemic COPD patients.
Patients and methods: Bland–Altman comparison of PaO2 and PcO2 served as the primary outcome parameter if PcO2 values were ≤60 mmHg and the secondary outcome parameter if PcO2 values were ≤55 mmHg. Pain associated with the measurements was assessed using a 100-mm visual analog scale.
Results: One hundred and two PaO2/PcO2 measurement pairs were obtained. For PcO2 values ≤60 mmHg, the mean difference between PaO2 and PcO2 was 5.99±6.05 mmHg (limits of agreement: -5.88 to 17.85 mmHg). For PcO2 values ≤55 mmHg (n=73), the mean difference was 5.33±5.52 mmHg (limits of agreement: -5.48 to 16.15 mmHg). If PaO2 ≤55 (≤60) mmHg was set as the cut-off value, in 20.6% (30.4%) of all patients, long-term oxygen therapy have been unnecessarily prescribed if only PcO2 would have been assessed. ABG was rated as more painful compared with CBG.
Conclusions: PcO2 does not adequately reflect PaO2 in hypoxemic COPD patients, which can lead to a relevant number of unnecessary long-term oxygen therapy prescriptions.

Keywords: blood gas analysis, COPD, respiratory insufficiency, hypoxemia

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