Evaluation of the add-on NOWAPI® medical device for remote monitoring of compliance to Continuous Positive Airway Pressure and treatment efficacy in obstructive sleep apnea

Abstract

Background: Optimizing the measurement of Continuous Positive Airway Pressure (CPAP) compliance and treatment efficacy is paramount for patients with obstructive sleep apnea syndrome (OSAS). Compliance knowledge is currently based on data coming from CPAP machines; however algorithms and measured parameters vary from one machine to another. This study was conducted to clinically evaluate a novel device, NOWAPI(®), designed to assess compliance remotely in conjunction with any CPAP machine. NOWAPI(®) was tested against polygraphy, the gold standard for the measurement of CPAP treatment duration and residual apnea-hypopnea index (AHI).

Methods: Single group assignment, open label, non-randomized. Sleep laboratory setting. 22 adult patients with OSAS treated by CPAP were included. Recordings were performed during one night while the patient was treated with his/her usual CPAP and interface. NOWAPI(®) data were collected electronically and compared to data acquisition and visual scoring using an EMBLETTA(®) GOLD polygraph. Statistics were only descriptive.

Results: Recordings were performed with six different CPAP machines and three different interfaces (full facemask, nasal pillow, nasal mask). The median [Q1; Q3] absolute difference in CPAP treatment duration between NOWAPI(®) and polygraphy was of 1.0 min [0.0; 12.0], corresponding to a relative difference of 0.21 % [0.0; 2.2] (Per Protocol data set, n = 20). NOWAPI(®) tended to underestimate residual AHI in a magnitude of two events per hour as compared to polygraphy. The device was well tolerated and the patient satisfaction was good.

Conclusions: This clinical study confirmed prior bench tests, showing that NOWAPI(®) estimate of CPAP treatment duration was clinically acceptable and in agreement with polygraphy. Although a limited number of OSAS patients treated by CPAP were included, relevant findings for the device improvement were identified. Trial Registration ClinicalTrials.gov identifier: NCT01441622. The study was funded by Air Liquide HealthCare.

Figures

Fig. 1

NOWAPI® stands on the patient circuit, at the output of the CPAP device. The diode indicator gives a traffic light feedback to the patient on the previous night CPAP treatment duration

Fig. 2

Schematic view of the NOWAPI®. DAand DB diameter upstream and at restriction site, respectively. Patm atmospheric pressure sensor, Pups pressure sensor upstream of the restriction, Pres pressure sensor at restriction site

Fig. 3

Comparison of overnight CPAP treatment duration (minutes)—Respiratory Polygraph vs NOWAPI® (PP data set, n = 20). Crosses represent the 16 patients with a perfect agreement in CPAP treatment duration measurement between NOWAPI® and polygraphy, all crosses being aligned on the 1:1 fit line. The circles represent the four outliers. Detailed NOWAPI® data files of patients #19 and 20 are presented in Fig. 4

Fig. 4

Example of NOWAPI® detailed data in two typical patients. The device measures two pressure signals (upstream restriction and at the site of restriction, pink and blue curves, left y-axis). Variations in the difference between two pressures (differential pressure, yellow curve, right y-axis) indicate a flow rate is detected. Panel a shows detailed data in patient #20, with variation in differential pressure indicating detection of a flow rate in the patient circuit, i.e. a CPAP treatment. Panel b shows detailed data in patient #19. The two pressure signals are always superimposed, there is no variation in differential pressure. This finding is compatible only with two situations, either no flow rate in the patient circuit, either reverse connection

Fig. 5

Differences between numbers of apneas and hypopnoeas (Panel a), apneas (Panel b) and hypopneas (Panel c) estimated by NOWAPI® and by respiratory polygraphy are presented for each of the common 15-min periods (n = 452) of the recording night. The x-axis plots the difference [NOWAPI® minus Respiratory Polygraph] and the y-axis the number of records. Panel d presents the Apnea-Hypopnea Index (events per hour) by patient for the overall recording night, estimated by NOWAPI® plotted against polygraphy with a 1:1 fit line. PP data set with detailed NOWAPI® data files indicating correct connection (n = 14)

Fig. 6

Patients’ opinion on NOWAPI® (n = 12). Results are mean ± SD. The self-administered satisfaction questionnaire included three questions on the general aspect of the device and two questions on the light indicator. Answers were given using a satisfaction scale (0, 20, 40, 60, 80, 100 %), 0 % being the poorest satisfaction and 100 % the maximum