To the Editor:
Reports of silent hypoxia in patients with coronavirus disease 2019 (Covid-19) have raised the question of whether patients should use pulse oximeters at home to measure oxygen saturation rather than relying on subjective dyspnea as an indicator of clinical deterioration.1,2 Many Covid-19 remote-monitoring programs include home pulse oximetry,3,4 but the effectiveness of these programs remains unknown. We report the findings from a randomized trial that assessed a text message–based remote-monitoring program (COVID Watch) supplemented with monitoring of oxygen saturation by means of a home pulse oximeter (ClinicalTrials.gov number, NCT04581863).
As part of routine care in our six-hospital health system (which includes more than 500 outpatient practices), adults in our electronic health record with Covid-19 infection — as determined by their clinician or a confirmed positive test for Covid-19 — are enrolled in COVID Watch, a 2-week program involving twice-daily automated text messages inquiring about dyspnea and offering rapid callbacks from nurses when appropriate. This program has been associated with improved survival as compared with no remote monitoring.5
From November 29, 2020, to February 5, 2021, we randomly assigned in a 1:1 ratio patients who were enrolled in COVID Watch to participate in the standard monitoring program in addition to home pulse oximetry or the standard program alone. Patients in the pulse oximetry group were provided a pulse oximeter and were monitored for subjective symptoms or a low or declining oxygen saturation. Ethical considerations precluded assigning patients to no monitoring as a control. The prespecified primary outcome was the number of days the patient was alive and out of the hospital at 30 days, assessed in patients with test-confirmed Covid-19. Exploratory outcomes included patient-reported anxiety levels, use of health care services, and death at 30 days. Details regarding the patients and the trial methods are provided in the Supplementary Appendix, available with the full text of this letter at NEJM.org; the trial protocol is also available at NEJM.org.
A total of 1041 patients (606 of whom had test-confirmed Covid-19) were assigned to the standard program group, and 1056 patients (611 of whom had test-confirmed Covid-19) were assigned to the pulse oximetry group. Among patients in the pulse oximetry group, 77.7% submitted at least one pulse oximetry reading; these patients submitted a mean (±SD) of 9.8±8.5 readings, corresponding to a response rate of 69.4±32.8% to pulse oximetry check-ins.
Among patients with test-confirmed Covid-19, there was no significant between-group difference in the number of days they were alive and out of the hospital at 30 days (mean, 29.4 days in the pulse oximetry group and 29.5 days in the standard program group; P=0.58; difference, −0.1 days; 95% confidence interval [CI], −0.4 to 0.2) (Table 1). Prespecified subgroup analyses that were specifically powered to detect a difference in the number of days patients were alive and out of the hospital among Black patients as compared with non-Hispanic White patients showed no significant difference in this outcome. The mean number of telephone encounters within the health system (an exploratory outcome) was 3.3±4.2 in the pulse oximetry group and 2.4±3.3 in the standard program group (difference, 0.9; 95% CI, 0.4 to 1.3).
Among patients with Covid-19, the addition of home pulse oximetry to remote monitoring did not result in a greater number of days alive and out of the hospital than subjective assessments of dyspnea alone.
Kathleen C. Lee, M.D.
Anna U. Morgan, M.D., M.S.H.P.
Krisda H. Chaiyachati, M.D., M.P.H.
David A. Asch, M.D.
Ruiying A. Xiong, M.S.
David Do, M.D.
Austin S. Kilaru, M.D., M.S.H.P.
Doreen Lam, B.A.
Andrew Parambath, B.A.
Ari B. Friedman, M.D., Ph.D.
Zachary F. Meisel, M.D., M.S.H.P.
Christopher K. Snider, M.P.H.
Deena L. Chisholm, M.P.H.
Sheila Kelly, M.P.H.
Jessica E. Hemmons, M.S.
Dina Abdel-Rahman, B.S.
Jeffrey Ebert, Ph.D.
Medha Ghosh, M.P.H.
Julianne Reilly, B.S.
Christina J. O’Malley, M.H.A.
Lauren Hahn, M.B.A.
Nancy M. Mannion, D.N.P., R.N.
Ann M. Huffenberger, D.B.A., R.N.
Susan McGinley, C.R.N.P.
Mohan Balachandran, M.A., M.S.
Neda Khan, M.H.C.I.
Judy A. Shea, Ph.D.
Nandita Mitra, Ph.D.
M. Kit Delgado, M.D.
Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
Supported by grants from the
Disclosure forms provided by the authors are available with the full text of this letter at NEJM.org.
This letter was published on April 6, 2022, at NEJM.org.
Drs. Lee and Morgan contributed equally to this letter.
1. Tobin MJ, Laghi F, Jubran A. Why COVID-19 silent hypoxemia is baffling to physicians. Am J Respir Crit Care Med 2020;202:356–360.
2. Greenhalgh T, Knight M, Inda-Kim M, Fulop NJ, Leach J, Vindrola-Padros C. Remote management of covid-19 using home pulse oximetry and virtual ward support. BMJ 2021;372:n677–n677.
3. UK National Health Service. COVID Oximetry @home (https://www.england.nhs.uk/nhs-at-home/covid-oximetry-at-home/).
4. Huynh DN, Millan A, Quijada E, John D, Khan S, Funahashi T. Description and early results of the Kaiser Permanente Southern California COVID-19 Home Monitoring Program. Perm J 2021;25:1–7.
5. Delgado MK, Morgan AU, Asch DA, et al. Comparative effectiveness of an automated text messaging service for monitoring COVID-19 at home. Ann Intern Med 2022;175:179–190.
|Outcome||Standard Program+Pulse Oximetry
|Days alive and out of the hospital||29.4±2.8||29.5±2.3||−0.1 (−0.4 to 0.2)||0.58|
|Day of enrollment||2.8±1.3||2.9±1.3||−0.1 (−0.3 to 0.1)|
|Day 7||2.3±1.3||2.3±1.3||0.0 (−0.2 to 0.3)|
|Day 14||2.0±1.3||2.0±1.2||0.0 (−0.3 to 0.4)|
|Emergency department encounter — no. of patients (%)||57 (9.3)||68 (11.2)||−1.9 (−5.3 to 1.5)§|
|Within health system — no. of patients/total no. (%)||56/57 (98.2)||67/68 (98.5)||−0.3 (−23.9 to 23.3)§|
|Days from enrollment to encounter||9.2±6.9||8.8±7.3||0.4 (−2.1 to 3.0)|
|Lowest recorded systolic blood pressure — mm Hg¶||121.5±15.7||121.3±14.8||0.2 (−5.3 to 5.7)|
|Lowest recorded oxygen saturation — %¶||93.7±5.1||94.2±11.8||−0.5 (−3.7 to 2.7)|
|Supplemental oxygen provided — no. of patients/total no. (%)¶||14/56 (25.0)||11/67 (16.4)||8.6 (−6.6 to 23.8)§|
|Maximum temperature — °F¶||99.1±1.1||98.7±1.2||0.4 (−0.1 to 0.8)|
|Hospitalization — no. of patients/total no. (%)||43/611 (7.0)||41/606 (6.8)||0.2 (−2.6 to 3.2)§|
|Within health system||39/43 (90.7)||41/41 (100.0)||−9.3 (−39.9 to 21.3)§|
|Intubation and ventilator support provided¶||4/39 (10.3)||1/41 (2.4)||7.8 (−3.1 to 18.8)§|
|Death — no. (%)||5 (0.8)||3 (0.5)||0.3 (−0.7 to 1.5)§|
|Health-system encounter — no. per patient¶‖|
|Office visit||0.2±0.6||0.2±0.5||0.0 (−0.1 to 0.1)|
|Telemedicine||0.5±0.9||0.5±0.9||0.0 (−0.1 to 0.1)|
|Telephone||3.3±4.2||2.4±3.3||0.9 (0.4 to 1.3)|