The utility of single-channel nasal airflow pressure transducer in the diagnosis of OSA at home.

RATIONALE: Given the high prevalence of obstructive sleep apnea (OSA) and the demand on polysomnography (PSG), there is a need for low cost accurate simple diagnostic modalities that can be easily deployed in primary care to improve access to diagnosis. STUDY OBJECTIVES: The aim was to examine the utility of single-channel nasal airflow monitoring using a pressure transducer at home in patients with suspected OSA. DESIGN: Cross-sectional study SETTING: Laboratory and home PARTICIPANTS: The study was conducted in two populations. Consecutive patients with suspected OSA were recruited from the sleep disorders clinic at a tertiary referral center and from 6 local metropolitan primary care centers. INTERVENTIONS: All patients answered questionnaires and had laboratory PSG. Nasal airflow was monitored for 3 consecutive nights at home in random order either before or after PSG. RESULTS: Atotal of 193 patients participated (105 sleep clinic patients and 88 from primary care). The mean bias PSG apnea hypopnea index (AHI) minus nasal flow respiratory disturbance index (NF RDI) was -4.9 events per hour with limits of agreement (2 SD) of 27.8. NF RDI monitored over 3 nights had high accuracy for diagnosing both severe OSA (defined as PSG AHI > 30 events per hour) with area under the receiver operating characteristic curve (AUC) 0.92 (95% confidence interval (CI) 0.88-0.96) and any OSA (PSG AHI > 5), AUC 0.87 (95% CI 0.80-0.94). CONCLUSIONS: Single-channel nasal airflow can be implemented as an accurate diagnostic tool for OSA at home in both primary care and sleep clinic populations.

Comparison between a single-channel nasal airflow device and oximetry for the diagnosis of obstructive sleep apnea.

RATIONALE: The most common single channel devices used for obstructive sleep apnea (OSA) screening are nasal airflow and oximetry. No studies have directly compared their role in diagnosing OSA at home. STUDY OBJECTIVES: To prospectively compare the diagnostic utility of home-based nasal airflow and oximetry to attended polysomnography (PSG) and to assess the diagnostic value of adding oximetry to nasal airflow for OSA. DESIGN: Cross-sectional study. SETTING: Laboratory and home. PARTICIPANTS: Sleep clinic patients with suspected OSA. INTERVENTIONS: All patients had laboratory PSG and 2 sets of 3 consecutive nights on each device; nasal airflow (Flow Wizard, DiagnoselT, Australia) and oximetry (Radical Set, Masimo, USA) at home in random order. RESULTS: Ninety-eight of the 105 patients enrolled completed home monitoring. The accuracy of nasal airflow respiratory disturbance index (NF RDI) was not different from oximetry (ODI 3%) for diagnosing OSA (area under the ROC curve (AUC) difference, 0.04; 95% CI of difference -0.05 to 0.12; P = 0.43) over 3 nights of at-home recording. The accuracy of NF RDI was higher after 3 nights compared to one night (AUC difference, 0.05; 95% CI of difference, 0.01 to 0.08; P = 0.04). Addition of oximetry to nasal airflow did not increase the accuracy for predicting OSA compared to nasal airflow alone (P > 0.1). CONCLUSIONS: Nasal flow and oximetry have equivalent accuracy for diagnosing OSA in the home setting. Choice of device for home screening of sleep apnea may depend on logistical and service delivery issues.

The role of single-channel nasal airflow pressure transducer in the diagnosis of OSA in the sleep laboratory.

RATIONALE: Obstructive sleep apnea (OSA) is a common but underdiagnosed disorder. There is a need for validated simpler modalities such as single-channel monitors to assist diagnosis of OSA. STUDY OBJECTIVES: To assess data sufficiency, agreement, and diagnostic accuracy of nasal airflow measured by a single-channel pressure transducer device (Flow Wizard, DiagnoseIT, Sydney, Australia) compared to attended full polysomnography (PSG) on the same night for OSA diagnosis. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Subjects with possible OSA referred to the sleep laboratory for PSG were eligible. METHODS: Nasal airflow was measured by a pressure transducer in the laboratory concurrently with PSG. RESULTS: Of 226 eligible subjects who consented, 221 (97.8%; 151 males, 70 females) completed the protocol. With nasal airflow measurement, 5.3% of subjects had insufficient data, compared with 2.2% on PSG. The mean difference between PSG AHI and NF RDI was -6.2 events/h with limits of agreement (+/- 2 standard deviation [SD]) of 17.0 events/hr. The accuracy of the Flow Wizard for diagnosing severe OSA (PSG AHI > 30) was very good (area under the ROC curve [AUC] 0.96; 95% confidence interval [CI] 0.92 to 0.99) and for diagnosing OSA (PSG AHI > 5) was good (AUC, 0.84; 95% CI, 0.77 to 0.90). There was no difference in the rate of data insufficiency and accuracy between males and females. CONCLUSION: Nasal flow measured by a nasal pressure transducer has a low rate of data insufficiency, good agreement, and high accuracy compared to PSG for diagnosing OSA in the monitored sleep laboratory setting.