Objective: Extraction and standardisation of pulse oximetry and supplemental oxygen data from electronic health records has the potential to improve risk-adjustment, quality assessment and prognostication. We develop an approach to standardisation and report on its use for benchmarking purposes.
Materials and methods: Using electronic health record data from the nationwide Veteran's Affairs healthcare system (2013-2017), we extracted, standardised and validated pulse oximetry and supplemental oxygen data for 2 765 446 hospitalisations in the Veteran's Affairs Patient Database (VAPD) cohort study. We assessed face, concurrent and predictive validities using the following approaches, respectively: (1) evaluating the stability of patients' pulse oximetry values during a 24-hour period, (2) testing for greater amounts of supplemental oxygen use in patients likely to need oxygen therapy and (3) examining the association between supplemental oxygen and subsequent mortality.
Results: We found that 2 700 922 (98%) hospitalisations had at least one pulse oximetry reading, and 864 605 (31%) hospitalisations received oxygen therapy. Patients monitored by pulse oximetry had a reading on average every 6 hours (median 4; IQR 3-7). Patients on supplemental oxygen were older, white and male compared with patients not receiving oxygen therapy (p<0.001) and were more likely to have diagnoses of heart failure and chronic pulmonary diseases (p<0.001). The amount of supplemental oxygen for patients with at least three consecutive values recorded during a 24-hour period fluctuated by median 2 L/min (IQR: 2-3), and 81% of such triplets showed the same level of oxygen receipt.
Conclusion: Our approach to standardising pulse oximetry and supplemental oxygen data shows face, concurrent and predictive validities as the following: supplemental oxygen clusters in the range consistent with hospital wall-dispensed oxygen supplies (face validity); there are greater amounts of supplemental oxygen for certain clinical conditions (concurrent validity) and there is an association of supplemental oxygen with in-hospital and postdischarge mortality (predictive validity).
Keywords: clinical physiology; epidemiology; health informatics; respiratory medicine (see thoracic medicine).
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