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Saleem, Ferhan

University of British Columbia

Background: Interstitial lung disease (ILD) is a collection of diseases that cause fibrosis and/or inflammation of lung parenchyma, often resulting in the adverse consequence of hypoxemia that can be alleviated by domiciliary oxygen. Objectives: 1) Derive and validate a risk model to predict new-onset exertional and resting hypoxemia in patients with ILD. 2) Identify oxygen guidelines worldwide and compare these to national domiciliary oxygen criteria. 3) Compare costs of domiciliary oxygen for patients with ILD and chronic obstructive pulmonary disease (COPD). Methods: 1) A multivariable model that predicted new-onset exertional and resting hypoxemia was derived and validated in international cohorts using time-varying Cox regression, with the final model optimizing Harrell's C-index and goodness-of-fit (GoF). 2) Clinical practice guidelines for domiciliary oxygen were identified and compared to oxygen criteria and funding source used by the 193 member countries in the United Nations obtained from an Internet-based literature review. 3) A retrospective chart review determined monthly costs of oxygen in ILD and COPD within a large domiciliary oxygen program from 2010-2017. Results: 1) The best-performing prediction model for both exertional and resting hypoxemia included age, body mass index, idiopathic pulmonary fibrosis diagnosis, percent-predicted forced vital capacity, and diffusing capacity of carbon monoxide. Good performance was exhibited for prediction of exertional (C-index=0.70, GoF=0.85) and resting hypoxemia (C-index=0.77, GoF=0.27) in the derivation cohort, with performance replicated in the validation cohort except for calibration for prediction of resting hypoxemia (GoF=0.001). 2) Guidelines for continuous oxygen were obtained for 30 respiratory societies and criteria for 46 countries with public funding for oxygen. No public funding was available in 145 countries (5.9 billion people). 3) Cost of oxygen declined after month 1 (ILD: ($202.57 ± $88.88 in month 1 versus $142.21 ± $59.01 in month 2-24, P<0.001; COPD: $222.85 ± $102.52 versus $156.65 ± $60.50, P<0.001). Long-term cost of oxygen in COPD was more than in ILD (P=0.02). Conclusions: These studies will help patients prepare for oxygen initiation, identify variability in oxygen criteria worldwide and quantify the limited access in many countries, and provide funders with a better understanding of costs.

Text

2022-12-23

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83518

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/