Domiciliary pulse-oximetry at exacerbation of chronic obstructive pulmonary disease: prospective pilot study

Abstract

Background: The ability to objectively differentiate exacerbations of chronic obstructive pulmonary disease (COPD) from day-to-day symptom variations would be an important development in clinical practice and research. We assessed the ability of domiciliary pulse oximetry to achieve this.

Methods: 40 patients with moderate-severe COPD collected daily data on changes in symptoms, heart-rate (HR), oxygen saturation (SpO2) and peak-expiratory flow (PEF) over a total of 2705 days. 31 patients had data suitable for baseline analysis, and 13 patients experienced an exacerbation. Data were expressed as multiples of the standard deviation (SD) observed from each patient when stable.

Results: In stable COPD, the SD for HR, SpO2 and PEF were approximately 5 min(-1), 1% and 10l min(-1). There were detectable changes in all three variables just prior to exacerbation onset, greatest 2-3 days following symptom onset. A composite Oximetry Score (mean magnitude of SpO2 fall and HR rise) distinguished exacerbation onset from symptom variation (area under receiver-operating characteristic curve, AUC = 0.832, 95%CI 0.735-0.929, p = 0.003). In the presence of symptoms, a change in Score of ≥1 (average of ≥1SD change in both HR and SpO2) was 71% sensitive and 74% specific for exacerbation onset.

Conclusion: We have defined normal variation of pulse oximetry variables in a small sample of patients with COPD. A composite HR and SpO2 score distinguished exacerbation onset from symptom variation, potentially facilitating prompt therapy and providing validation of such events in clinical trials.

Figure 1

Study Profile. Study profile summarising distribution of oximeters and data collection. No data were used in more than one analysis.

Figure 2

Time Course of Symptoms and Oximetry Variables at Exacerbation. Time course of symptom count, heart rate, oxygen saturation (SpO₂) and peak-expiratory flow (PEF) from seven days prior (-7) to exacerbation onset (day 0, vertical line) and seven days into exacerbation of COPD. Values of the physiological variables are the mean of 13 exacerbations in 13 patients, expressed as standard deviation multiples away from each patient's stable mean (see text for details). A 1SD change is an approximate alteration in heart rate of 5 min^-1, SpO₂ of 1% and PEF of 10l min^-1. Symptom count values are the mean from the 13 patients.

Figure 3

Time Course of Symptoms and Oximetry Variables At Exacerbation. Time course of heart rate, oxygen saturation (SpO₂) and peak-expiratory flow (PEF) from seven days prior (-7) to exacerbation onset (day 0, vertical line) and seven days into exacerbation of COPD. Data expressed as mean and 95%CI (in SD units) for each variable separately.

Figure 4

Time Course of Oximetry and Oximetry-PEF Scores At Exacerbation. Time course of Oximetry and Oximetry-PEF scores from seven days prior (-7) to exacerbation onset (day 0, vertical line) and seven days into exacerbation of COPD. Values are the mean score of 13 exacerbations in 13 patients (see text for details).

Figure 5

Time Course of Oximetry and Oximetry-PEF Scores At Exacerbation. Time course of Oximetry and Oximetry-PEF scores from seven days prior (-7) to exacerbation onset (day 0, vertical line) and seven days into exacerbation of COPD. Data represent the mean and 95%CI for each score separately.

Figure 6

ROC Curves. ROC curves for the ability of the individual components, and Oximetry and Oximetry-PEF scores to differentiate exacerbation onset from day-to-day symptom variation (symptom days) in COPD. The data are reported in Table 4.