DISCUSSION
There are 3 new findings in this study. First, health care practitioners at JBVAMC did not document the presence of NCD during sleep in patients with hypoxemic CRF due to COPD and receiving LTOT. Second, one-third of these patients reported frequent NCD during sleep when interviewed. Third, the nocturnal events were associated with a higher hospitalization rate for physician-diagnosed COPD exacerbation and higher overall hospital costs. These findings are unlikely to be explained by differences in COPD severity and/or known triggers that lead to COPD exacerbation and require hospitalization because baseline physiologic and LTOT parameters were similar in both groups. Conceivably, patients with untreated OSA could be restless while asleep, leading to NCD. However, this explanation seems unlikely because the frequency of OSA was similar in both groups.
Nocturnal arterial oxygen desaturation in patients with COPD without evidence of OSA may contribute to the frequency of exacerbations.16 Although the mechanism(s) underlying this phenomenon is uncertain, we posit that prolonged nocturnal airway wall hypoxia could amplify underlying chronic inflammation through local generation of reactive oxygen species, thereby predisposing patients to exacerbations. Frequent COPD exacerbations promote disease progression and health status decline and are associated with increased mortality.11,13 Moreover, hospitalization of patients with COPD is the largest contributor to the annual direct cost of COPD per patient.10,12 The higher hospitalization rate observed in the NCD group in our study suggests that interruption of supplemental oxygen delivery while asleep may be a risk factor for COPD exacerbation. Alternatively, an independent factor or factors may have contributed to both NCD during sleep and COPD exacerbation in these patients or an impending exacerbation resulted in sleep disturbances that led to NCD. Additional research is warranted on veterans with hypoxemic CRF from COPD who are receiving LTOT and report frequent NCD during sleep that may support or refute these hypotheses.
To the best of our knowledge, NCD during sleep has not been previously reported in patients with hypoxemic CRF due to COPD who are receiving LTOT at home or in an acute care setting.17-20 Several layperson proposals to secure nasal cannulas to the face while sleeping are posted online. These include wearing a commercially available headband with 2 Velcro loops that fix the cannula tube, using fabric medical tape on both cheeks, and wearing a sleep mask. Conceivably, the efficacy and safety of these inexpensive interventions to mitigate NCD during sleep in patients receiving LTOT with hypoxemic CRF from COPD could be tested in clinical trials.
Limitations
This was a small, single-site study, comprised entirely of male patients who are predominantly Black veterans. The telephone interviews with veterans self-reporting NCD during their sleep are prone to recall bias. In addition, the validity and reproducibility of NCD during sleep were not addressed in this study. Missing data from 9 nonresponders may have introduced a nonresponse bias in data analysis and interpretation. The overall hospital cost for a COPD exacerbation at JBVAMC was derived from VA data; US Centers for Medicare & Medicaid Services or commercial carrier data may be different.15,21 Lastly, access to LTOT for veterans with hypoxemic CRF from COPD is regulated and supervised at VA medical facilities.14 This process may be different for patients outside the VA. Taken together, it is difficult to generalize our initial observations to non-VA patients with hypoxemic CRF from COPD who are receiving LTOT. We suggest a large, prospective study of veterans be conducted to determine the prevalence of NCD during sleep and its relationship with COPD exacerbations in veterans receiving LTOT with hypoxemic CRF due to COPD.
CONCLUSIONS
Clinicians at the JBVAMC did not document the presence of NCD during sleep in patients with hypoxemic CRF from COPD who received LTOT. However, self-reported, weekly nocturnal NCD episodes were associated with a higher hospitalization rate for COPD exacerbation and higher hospital costs. Accordingly, user-friendly devices to mitigate NCD during sleep should be developed.
Acknowledgments
We thank Yolanda Davis, RRT, and George Adam for their assistance with this project.