Using a wrist-worn device based on peripheral arterial tonometry to diagnose obstructive sleep apnea: in-laboratory and ambulatory validation

Abstract

Study objectives: To assess the accuracy of a wrist-worn device (Watch_PAT 100) to diagnose obstructive sleep apnea in the home.

Design: Participants completed 2 overnight diagnostic studies with the test device: 1 night in the laboratory with concurrent polysomnography and 1 night in the home with only the Watch_PAT. The order of the laboratory and home study nights was random. The frequency of respiratory events on the PSG was quantified using indexes based on 2 definitions of hypopnea: the respiratory disturbance index (RDI) using American Academy of Sleep Medicine Task Force criteria for clinical research, also referred to as the Chicago criteria (RDI.C), and the Medicare guidelines (RDI.M). The Watch_PAT RDI (PAT RDI) and oxygen desaturation index (PAT ODI) were then evaluated against the polysomnography RDI.C and RDI.M, respectively, for both Watch_PAT diagnostic nights, yielding IN-LAB and HOME-LAB comparisons.

Setting: Sleep laboratory affiliated with a tertiary-care academic medical center.

Patients: 30 patients referred with suspected OSA.

Interventions: N/A.

Measurements and results: The polysomnography and PAT measures were compared using the mean [2 SD] of the differences and the intra-class correlation coefficient (ICC). The receiver-operator characteristic curve was used to assess optimum sensitivity and specificity and calculate likelihood ratios. For the IN-LAB comparison, there was high concordance between RDI.C and PAT RDI (ICC = 0.88, mean difference 2.5 [18.9] events per hour); RDI.M and PAT ODI (ICC = 0.95, mean difference 1.4 [12.9] events per hour; and sleep time (ICC = 0.70, mean difference 7.0 [93.1] minutes) between the test device and PSG. For the HOME-LAB comparison, there was good concordance between RDI.C and PAT RDI (ICC = 0.72, mean difference 1.4 [30.1] events per hour) and RDI.M and PAT ODI (ICC = 0.80, mean difference 1.6 [26.4] events per hour) for the test device and PSG. Home studies were performed with no technical failures.

Conclusions: In a population of patients suspected of having obstructive sleep apnea, the Watch_PAT can quantify an ODI that compares very well with Medicare criteria for defining respiratory events and an RDI that compares favorably with Chicago criteria for defining respiratory events. The device can be used with a low failure rate for single use in the lab and home for self-administered testing.

Figure 1

In-laboratory (Watch_PAT data collected concurrently with polysomnography data) comparisons are shown. (A) Scatter plot of PSG RDI.C vs LAB-PAT RDI with a best-fit line of Y = −0.97 + 0.95X. (B) Bland-Altman plot of PSG RDI.C vs LAB-PAT RDI. Agreement was good except for 1 case, subject #9. (C) Scatter plot of PSG RDI.M vs LAB-PAT ODI with a best-fit line of Y = 0.10 + 1.1X. (D) Bland-Altman plot of PSG RDI.M vs LAB-PAT ODI. Agreement was good except for one case, subject #3. PAT refers to peripheral arterial tonometer; PSG, polysomnography; RDI, respiratory disturbance index; RDI.C, RDI based on American Academy of Sleep Medicine criteria (also known as the Chicago criteria); RDI.M, RDI based on Medicare criteria; ODI, oxygen desaturation index; ICC, intraclass correlation coefficient.

Figure 2

This represents a 3-minute sample from a polysomnogram (subject #9: mild sleep apnea by Chicago criteria). One hypopnea is shown (event indicated by the word Hypopnea in the box). Five respiratory events detected by the Watch_PAT software and included in the peripheral arterial tonometer (PAT) respiratory disturbance index (RDI) are indicated on the electroencephalogram (EEG) channel with the text Resp Event Arousal. No oxyhemoglobin desaturations of 4% were present during this segment of the study. This illustrates a period with 20% agreement when comparing the Watch_PAT RDI to the Chicago criteria for scoring respiratory events, yet there was 100% agreement when comparing the Watch_PAT oxygen desaturation index (ODI) to the Medicare criteria for scoring respiratory events. Thus, due to the sensitivity of the Watch_PAT algorithm to detect sympathetic activation for scoring respiratory events included in the PAT RDI and the absence of an airflow signal to increase specificity, 4 respiratory events were detected by the Watch_PAT device that did not meet Chicago criteria by polysomnography in this individual. However, careful examination of the raw data does indicate sustained periods of snoring and flow limitation on the nasal pressure channel. EMG_AT refers to anterior tibialis electromyography; NP, nasal pressure (surrogate for airflow); Abd, abdominal movement; HR, heart rate; SaO₂, arterial oxyhemoglobin saturation.

Figure 3

This represents a 2-minute sample from a polysomnogram (subject #3: severe sleep apnea). Four obstructive apneas are shown (events indicated by the words Apnea Obstructive in the boxes). Respiratory events detected by the Watch_PAT software and included in the peripheral arterial tonometer (PAT) respiratory disturbance index (RDI) are indicated on the electroencephalogram (EEG) channel with the text Resp Event Arousal. An oxyhemoglobin desaturation of 4% detected by the Watch_PAT software and included in the PAT oxygen desaturation index (ODI) is indicated on the arterial oxyhemoglobin saturation (SaO₂) channel with the word Desaturation. This illustrates a period with 100% agreement when comparing the Watch_PAT RDI to the Chicago criteria for scoring respiratory events but only 25% agreement when comparing the Watch_PAT ODI to the Medicare criteria for scoring respiratory events. Thus, due to the lack of Watch_PAT airflow measurement, 3 obstructive events without adequate oxyhemoglobin desaturation were missed based on these less-inclusive criteria. NP prefers to nasal pressure (surrogate for airflow); Abd, abdominal movement; HR, heart rate.

Figure 4

Home-Laboratory (Watch_PAT and polysomnography [PSG] data collected on different nights) comparisons are shown. (A) Scatter plot of PSG RDI.C vs HOME-PAT RDI with a best-fit line of Y = 8.6 + 0.76X. (B) Bland-Altman plot of PSG RDI.C vs HOME-PAT RDI. (C) Scatter plot of PSG RDI.M vs HOME-PAT ODI with a best-fit line of Y = 2.8 + 0.93X. (D) Bland-Altman plot of PSG RDI.M vs HOME-PAT ODI. PAT refers to peripheral arterial tonometer; PSG, polysomnography; RDI, respiratory disturbance index; RDI.C, RDI based on American Academy of Sleep Medicine criteria (also known as the Chicago criteria); RDI.M, RDI based on Medicare criteria; ODI, oxygen desaturation index.

Figure 5

Home-Laboratory (Watch_PAT data collected on different nights) comparisons are shown. (A) Bland-Altman plot of HOME-PAT RDI vs LAB-PAT RDI. (B) Bland-Altman plot of HOME-PAT ODI vs LAB-PAT ODI. PAT refers to peripheral arterial tonometer; PSG, polysomnography; RDI, respiratory disturbance index; RDI.C, RDI based on American Academy of Sleep Medicine criteria (also known as the Chicago criteria); ODI, oxygen desaturation index.