Performance of peripheral arterial tonometry-based testing for the diagnosis of obstructive sleep apnea in a large sleep clinic cohort

STUDY OBJECTIVES

Peripheral arterial tonometry (PAT)-based technology represents a validated portable monitoring modality for the diagnosis of OSA. We assessed the diagnostic accuracy of PAT-based technology in a large point-of-care cohort of patients studied with concurrent polysomnography (PSG).

METHODS

During study enrollment, all participants suspected to have OSA and tested by in-laboratory PSG underwent concurrent PAT device recordings.

RESULTS

Five hundred concomitant PSG and WatchPat tests were analyzed. Median (interquartile range) PSG AHI was 18 (8-37) events/h and PAT AHI_3% was 25 (12-46) events/h. Average bias was + 4 events/h. Diagnostic concordance was found in 42%, 41%, and 83% of mild, moderate, and severe OSA, respectively (accuracy = 53%). Among patients with PAT diagnoses of moderate or severe OSA, 5% did not have OSA and 19% had mild OSA; in those with mild OSA, PSG showed moderate or severe disease in 20% and no OSA in 30% of patients (accuracy = 69%). On average, using a 3% desaturation threshold, WatchPat overestimated disease prevalence and severity (mean + 4 events/h) and the 4% threshold underestimated disease prevalence and severity by -6 events/h.

CONCLUSIONS

Although there was an overall tendency to overestimate the severity of OSA, a significant percentage of patients had clinically relevant misclassifications. As such, we recommend that patients without OSA or with mild disease assessed by PAT undergo repeat in-laboratory PSG. Optimized clinical pathways are urgently needed to minimize therapeutic decisions instituted in the presence of diagnostic uncertainty.

Improving the performance of peripheral arterial tonometry-based testing for the diagnosis of obstructive sleep apnea

Outside sleep laboratory settings, peripheral arterial tonometry (PAT, eg, WatchPat) represents a validated modality for diagnosing obstructive sleep apnea (OSA). We have shown before that the accuracy of home sleep apnea testing by WatchPat 200 devices in diagnosing OSA is suboptimal (50%-70%). In order to improve its diagnostic performance, we built several models that predict the main functional parameter of polysomnography (PSG), Apnea Hypopnea Index (AHI). Participants were recruited in our Sleep Center and underwent concurrent in-laboratory PSG and PAT recordings. Statistical models were then developed to predict AHI by using robust functional parameters from PAT-based testing, in concert with available demographic and anthropometric data, and their performance was confirmed in a random validation subgroup of the cohort. Five hundred synchronous PSG and WatchPat sets were analyzed. Mean diagnostic accuracy of PAT was improved to 67%, 81% and 85% in mild, moderate-severe or no OSA, respectively, by several models that included participants' age, gender, neck circumference, body mass index and the number of 4% desaturations/hour. WatchPat had an overall accuracy of 85.7% and a positive predictive value of 87.3% in diagnosing OSA (by predicted AHI above 5). In this large cohort of patients with high pretest probability of OSA, we built several models based on 4% oxygen desaturations, neck circumference, body mass index and several other variables. These simple models can be used at the point-of-care, in order to improve the diagnostic accuracy of the PAT-based testing, thus ameliorating the high rates of misclassification for OSA presence or disease severity.

Obstructive Lung Disease and Obstructive Sleep Apnea (OLDOSA) cohort study: 10-year assessment

STUDY OBJECTIVES

Asthma, chronic obstructive pulmonary disease (COPD), and obstructive sleep apnea (OSA) are very prevalent disorders. Their coexistence in the same individual has an unclear effect on natural history and long-term outcomes.

METHODS

The OLDOSA (Obstructive Lung Disease and Obstructive Sleep Apnea) cohort enrolled 4,980 veterans with an acute hospitalization and in whom asthma, COPD, OSA, overlapping conditions, or none of these disorders at baseline had been diagnosed. Pulmonary function, polysomnography, positive airway pressure (PAP) recommendations and adherence, and vital status were collected and analyzed. Various proportional hazards models were built for patients with OSA to test the effect of PAP therapy on survival.

RESULTS

Ten-year all-cause cumulative mortality rate was 52.8%; median time to death was 2.7 years. In nonoverlapping asthma, OSA and COPD, mortality rates were 54.2%, 60.4%, and 63.0%, respectively. The overlap syndromes had the following mortality: COPD-OSA 53.2%, asthma-COPD 62.1%, asthma-OSA 63.5%, and triple overlap asthma-COPD-OSA 67.8%. In patients with OSA not on PAP therapy, after adjustment for age, comorbidities, and lung function, risk of death was 1.34 (1.05-1.71) times higher than those undergoing treatment. Similarly, in patients with OSA nonadherent to PAP therapy the adjusted risk of death was 1.78 (1.13-2.82) times higher versus those using it at least 70% of nights and more than 4 hours nightly.

CONCLUSIONS

In this large longitudinal cohort of hospitalized veterans with high comorbid burden, asthma, COPD, OSA and their overlap syndromes had very high long-term mortality. In patients with OSA, PAP initiation and superior therapeutic adherence were associated with significantly better survival.

VAMONOS (Veterans Affairs' Metabolism, Obstructed and Non-Obstructed Sleep) Study: Effects of CPAP Therapy on Glucose Metabolism in Patients with Obstructive Sleep Apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) and type 2 diabetes mellitus (T2DM) are prevalent disorders that pose increased risk of cardiovascular disease and death. The objective of this study was to clarify if continuous positive airway pressure (CPAP) therapy for OSA affects T2DM control and emergence.

METHODS

Point-of-care, comparative effectiveness study; cross-sectional and longitudinal analyses.

RESULTS

Our cohort included 928 consecutive patients; 13% were women; 36% were Caucasians and 61% African-Americans. OSA was diagnosed in approximately 738 patients and CPAP was initiated in 718 patients; median duration of therapy was 5 mo (25% to 75% interquartile range [IQR] 3-14). Patients with OSA used CPAP therapy for a median duration of 4.8 h, 34.5% of the nights. Adherence to CPAP was prespecified as follows: good (≥ 70% nights and ≥ 4 h/night), excellent (≥ 80% nights and ≥ 6 h/night) or outstanding (≥ 90% of nights and 8 h/night). Based on objective data, good, excellent, and outstanding compliance were found in only 30%, 20%, and 6%, respectively. Three percent of subjects without CPAP follow-up and less than 4% of those nonadherent to CPAP therapy (based on the established criteria) developed incident T2DM. Incident T2DM developed in only 0.8% of those with good compliance and in none (0%) of those in the excellent and outstanding groups. During follow-up, median weight change was +0.3 kg (IQR -1.8 to 2.7).

CONCLUSIONS

We found that an outstanding compliance to CPAP reduced fasting blood glucose in patients with OSA. Longitudinally, higher levels of therapeutic adherence may affect the rate of incident impaired fasting glucose, prediabetes, and T2DM, despite the observed weight gains.

COMMENTARY

A commentary on this article appears in this issue on page 365.