A novel device for measuring long-term oxygen therapy adherence: a preliminary validation.

INTRODUCTION Current methods for measuring patient adherence to long-term oxygen therapy fail to measure the actual amount of time the patient is inhaling oxygen and the pattern of oxygen use within the day. We have developed a novel oxygen-adherence monitor to address these limitations, and this report introduces the monitor and provides preliminary data validating its use. METHODS This battery-powered monitor attaches to the oxygen source and detects respiratory-related pressure fluctuations transmitted through the nasal cannula. The monitor takes a measurement over a 25-second period, at 4-min intervals. It detects and stores data on 4 different states that describe the patient's actual use of the oxygen source and nasal cannula: source-off/cannula-off, source-off/cannula-on, source-on/cannula-off, and source-on/cannula-on. We studied the monitor's performance with 10 patients with chronic obstructive pulmonary disease, during a directly-observed sequence of using and not using supplemental oxygen via nasal cannula, while sitting and walking. RESULTS The monitor correctly detected 122 out of 129 measurements among all participants, yielding a 95\% detection accuracy. CONCLUSION A monitor that objectively measures oxygen inhalation, rather than oxygen expenditure, may help improve the management of patients on long-term oxygen therapy.