PURPOSE: Obstructive sleep apnea (OSA) is common in patients with chronic obstructive pulmonary disease (COPD). The objective of this study was to develop a strategy to interpret nocturnal pulse oximetry tracings and assess its capacity for detection of OSA in COPD patients.
METHODS: A consecutive chart review was conducted (2006-2009). Based on nocturnal level 1 polysomnography, OSA was diagnosed if the apnea-hyponea index was ≥ 15/hour. A comprehensive set of criteria were developed for interpretation of pulse oximetry tracings through iterative validation and inter-scorer concordance of ≥ 80%. Criteria consisted of quantification of desaturation events (desaturation ≥ 4%, 1 hour time scale), saturation patterns (≥ 3 similar desaturation/saturation cycles, 15 min time scale) and mean saturation within each pattern. These findings were then prospectively compared to the polysomnography diagnosis in order to calculate the sensitivity, specificity, and likelihood ratios. Patients on long-term oxygen therapy (LTOT) were included.
RESULTS: Of 51 patients (23 males), 35 had OSA (69%). Mean FEV1 predicted (range) was 46% (16-75%) and 60% of patients were on LTOT (1-4 L). Among these 35 patients, 22 were identified as having OSA according to oximetry tracing criteria, sensitivity and specificity were 0.63 and 0.69, and positive likelihood ratio (95% confidence interval (CI)) was 2.01 (0.96-4.46). With desaturation events of ≥ 25/hour included in the oximetry interpretation criteria, the sensitivity (95%CI) was 0.28 (0.16 - 0.45) and specificity 1.00 (0.79 - 1.0). All patients with OSA were accurately identified. A sub-analysis of oximetry tracings performed on LTOT only, resulted in a sensitivity of 0.64 and specificity of 0.83, with a positive likelihood ratio (95%CI) of 3.82 (0.621 to 23.49). No important differences were assessed between the OSA and non-OSA groups with regards to pulse oximetry event count, pattern count, or mean saturation.
CONCLUSION: Pulse oximetry has diagnostic value to identify OSA in patients with moderate to severe COPD.
CLINICAL IMPLICATIONS: In patients with moderate to severe COPD, OSA can be identified with nocturnal oximetry even in the presence of LTOT.
DISCLOSURE: Marcel Baltzan, No Financial Disclosure Information; No Product/Research Disclosure Information