Chest
Volume 116, Issue 2, August 1999, Pages 314-321
Journal home page for Chest

Clinical Investigations
COPD
Ambulatory Oximetry Monitoring in Patients With Severe COPD: A Preliminary Study

https://doi.org/10.1378/chest.116.2.314Get rights and content
Under a Creative Commons license
open archive

Background

The benefits of long-term oxygen supplementation in COPD patients with hypoxemia are well established. The standard approach to prescribing oxygen uses a static assessment of oxygen requirements in a hospital or clinic setting. The assumption behind this approach is that patients will maintain a“ therapeutic” hemoglobin oxygen saturation (Spo2) in the outpatient setting. We questioned the validity of this assumption, and hypothesized that many patients may demonstrate significant oxygen desaturation during normal activities of daily living.

Study design, methods, and measurements

We determined if oxygen supplementation maintained a therapeutic Spo2 level in patients with COPD (n = 27), using the technique of ambulatory oximetry monitoring (AOM). AOM consisted of using a portable oximeter to monitor Spo2, pulse rate, and patient activity while patients were engaged in normal activities of daily living over an extended time period (∼18 h). The portable oximeter collected and stored these data every 15 s over the monitored time period. Each AOM recording was manually scored for desaturation events and other key variables, including average Spo2 over the monitoring period, the average number of desaturation events per hour, and the percentage of monitored time deleted secondary to artifacts.

Setting

University-affiliated Veterans Affairs Medical Center.

Patients

All subjects were patients with stable COPD with no recent history of hospitalization or exacerbation of their lung disease.

Results

This cohort of patients demonstrated a surprising frequency of desaturation below the recommended target Spo2value (90%), which averaged approximately 25% of AOM recording time. There was wide variability among patients in the percentage of time Spo2 was below the target value (range, 3 to 67% of AOM recording time). Motion artifact on the AOM recordings was not a major problem; an average of 8% of the recording time was deleted secondary to artifacts in this patient cohort.

Conclusions

The results demonstrate that AOM is feasible and accurate with an acceptable level of motion artifact. These results also suggest that the standard approach for prescribing oxygen may lead to subtherapeutic Spo2 values in the outpatient setting. AOM holds promise as a tool to monitor the adequacy of oxygen prescriptions in the outpatient setting in patients with lung disease.

Key words

ambulatory oximetry monitoring
COPD
long-term oxygen therapy

Abbreviations

ABG
arterial blood gas
AOM
ambulatory oximetry monitoring
LTOT
long-term oxygentherapy
Sao2
arterial oxygen saturation
Spo2
hemoglobin oxygen saturation

Cited by (0)

The opinions expressed in this manuscript are solely those of theauthors. The portable oximetry equipment and accompanying software usedin this study were supplied by Respironics, Inc (Monroeville, PA). The authors have not received any direct remuneration from the manufacturer of the portable oximetry unit, other than using theportable oximeter.