Capillary PO(2) does not adequately reflect arterial PO(2) in hypoxemic COPD patients

PURPOSE: To compare arterial (P(a)O(2)) with capillary (P(c)O(2)) 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 P(c)O(2) and P(a)O(2) has not been evaluated in hypoxemic COPD patients. PATIENTS AND METHODS: Bland–Altman comparison of P(a)O(2) and P(c)O(2) served as the primary outcome parameter if P(c)O(2) values were ≤60 mmHg and the secondary outcome parameter if P(c)O(2) values were ≤55 mmHg. Pain associated with the measurements was assessed using a 100-mm visual analog scale. RESULTS: One hundred and two P(a)O(2)/P(c)O(2) measurement pairs were obtained. For P(c)O(2) values ≤60 mmHg, the mean difference between P(a)O(2) and P(c)O(2) was 5.99±6.05 mmHg (limits of agreement: −5.88 to 17.85 mmHg). For P(c)O(2) values ≤55 mmHg (n=73), the mean difference was 5.33±5.52 mmHg (limits of agreement: −5.48 to 16.15 mmHg). If P(a)O(2) ≤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 P(c)O(2) would have been assessed. ABG was rated as more painful compared with CBG. CONCLUSIONS: P(c)O(2) does not adequately reflect P(a)O(2) in hypoxemic COPD patients, which can lead to a relevant number of unnecessary long-term oxygen therapy prescriptions.