JMIR Publications

ABSTRACT

Background:

Chronic obstructive pulmonary disease (COPD) is a major global health problem. The World Health Organisation estimated the global prevalence in 2016 to be 251 million cases and COPD is ranked as the fifth leading cause of death. COPD is predicted to become the third commonest cause of death by 2030. Individuals with COPD experience acute deteriorations in respiratory health called ‘exacerbations’ which profoundly affect quality of life and can lead to hospital admission. Prevention and mitigation of exacerbations is a key goal in managing COPD. One method that might improve COPD outcomes is early identification of exacerbations. Prompt access to therapy at exacerbation onset is associated with faster symptom recovery. Delay in accessing care may be due to the difficulty in differentiating day-to-day symptom variation from exacerbations. There has therefore been interest in the utility of monitoring physiological variables to support the earlier detection of exacerbations. Early, objective identification of exacerbations would also be of value in research.

Objective:

The goal of this research is to study the possibility of predicting a COPD exacerbation by monitoring the patient’s physiological parameters overnight, thus removing non-COPD related effects of, for example, anxiety and exercise on the physiological signal.

Methods:

Participants and recruitment Participants were approached from COPD clinics and pulmonary rehabilitation (PR) classes between September 2016 and January 2018, at three different sites in London, UK. Ethical approvals were obtained from the local committee at the Royal Free Hospital, and the UK Health Research Authority (16/LO/1120). The study was registered at ClinicalTrials.gov (NCT03003702). All participants provided written informed consent. Inclusion criteria were a confirmed diagnosis of COPD (smoking history ≥10 pack years and post-bronchodilator FEV1/FVC < 0.7), one or more self-reported moderate or severe COPD exacerbations in the previous 12 months, and ability to use study equipment and attend appointments. Exclusion criteria were an existing diagnosis of obstructive sleep apnoea (either via self-report or results of STOP-Bang or Epworth questionnaires (10, 11)), and/or significant co-morbidity preventing participation. Study procedures At recruitment, we collected demographic and clinical data and performed post-bronchodilator spirometry (FEV1, and FVC). Subjects were randomised using sealed envelopes; each envelope contained a card indicating once-daily or overnight measurement. The researcher instructed the participant how to use the pulse oximetry equipment based on their allocation (wristband pulse oximeter (Nonin 3150) for overnight monitoring, or finger pulse oximeter (Nonin G92) for once-daily (morning) monitoring), peak expiratory flow (PEF) meter, and the COPD Assessment Test (CAT) questionnaire, and how to record the results on a diary card. Subjects were monitored for six months, or until they completed recovery from a first exacerbation (whichever was sooner). Data recorded in the first week were not included in the analysis. During the subsequent two weeks (the ‘stable state’), participants were closely monitored to ensure they were using the equipment properly and reporting data accurately. Participants were instructed to call the researcher if they developed an exacerbation, or if they developed any medical problem resulting in hospitalisation. Monitoring was continued through the exacerbation until clinical recovery at which point the equipment was returned and participation was complete. Equipment was removed and the study was completed for any participant that did not develop an exacerbation within six months. In the absence of an exacerbation, in-person visits were scheduled at two weeks, three months, and six months. An exacerbation was defined as the need for oral corticosteroids and/or antibiotics, as judged by the patient’s clinician or self-management plan. At the end of the study, a ten-question acceptability survey was administered to participants allocated to the overnight monitoring group to evaluate their acceptance of continuous overnight pulse-oximetry monitoring. The questionnaire covered willingness to use the monitoring equipment, effect on sleep quality, and convenience of the device. The highest possible score was 90 (the higher the score, the greater the acceptance).

Results:

The time to treatment initiation from changes in symptoms versus changes in pulse oximetry first becoming abnormal were not statistically significant. However, patients waited an average of five days before treatment and therefore objectively monitoring symptoms or use of overnight oximetry may prompt patients to seek attention. Second, overnight measurement of heart rate may permit earlier detection of exacerbations compared to once-daily measurement, because the standard deviation of the stable state mean is smaller, permitting detection of smaller changes (increased signal-to-noise ratio). Third, changes in heart rate were more useful than changes in oxygen saturation or PEF. Finally, a combined oximetry score calculated by subtracting the Z score of change in oxygen saturation from the Z score of change in heart rate had a positive predictive value over 90% for the detection of exacerbation. The findings of this pilot study support our hypothesis that nocturnal pulse oximetry could facilitate earlier, objective detection of COPD exacerbations.

Conclusions:

In conclusion, we have demonstrated that overnight pulse oximetry could facilitate earlier, objective detection of COPD exacerbations. Overnight pulse oximetry allowed earlier detection compared to once-daily monitoring. Heart rate was superior to oxygen saturation and PEF, and combining heart rate and oxygen saturation data provided the best performance. Clinical Trial: Ethical approvals were obtained from the local committee at the Royal Free Hospital, and the UK Health Research Authority (16/LO/1120). The study was registered at ClinicalTrials.gov (NCT03003702).