Clinical Study

Validated Clinical Study using The Remmers Sleep Recorder

The Remmers Sleep Recorder was clinically validated at the Foothills Sleep Centre, Calgary, AB. A clinical trial of 241 randomly selected patients demonstrated a correlation between the Respiratory Disturbance Index (RDI) measured using the Remmers Sleep Recorder compared with the Apnea-Hyponea Index (AHI) measured with a full polysomnogram (PSG). A correlation of 0.97 was observed. This study utilized SagaTech's RDI algorithm which automatically analyzes the data, thereby eliminating the need for manual scoring. This study is the largest such validation of a sleep monitor to date. It demonstrates technical proficiency which exceeds that provided by other monitors and is acceptable for clinical purposes. A report summarizing the findings of the study, which has been published in a leading peer-reviewed journal(1) (Thorax 2000; 55; 302-307).

Study Objectives

To evaluate the diagnostic accuracy of the Remmers Sleep Recorder in adults suspected of having sleep apnea by comparison to the gold-standard polysomnogram (PSG).

The Remmers Sleep Recorder Description

The Remmers Sleep Recorder is an ambulatory sleep recorder designed for unattended sleep studies in the home environment. Remmers Sleep Recorder measures up to 10 diagnostic indicators of sleep apnea. They include oxygen saturation, airflow, heart rate, respiratory effort, snoring, body position, leg EMGs, mask pressure and airflow on continuous positive airway pressure (CPAP).

Study Design

Patients were recruited at random the Alberta Lung Association Sleep Center, the major sleep referral center for southern Alberta. All patients were over the age of 18. A randomly selected population underwent in-laboratory PSG and Remmers Sleep Recorder testing simultaneously (n=241).

PSG data were recorded by a computerized polysomnographic system (Alice 3, Respironics Inc.), which included a standardized montage of channels that recorded EEG, EOG, EMG and ECG. A thermistor (Respironics Inc.) was used to measure airflow. Respiratory effort and oxygen saturation were assessed using inductance plethysmography (Respitrace, Ambulatory Monitoring, Ardsley, New York) and the 953 Finger Flex Sensor (Respironics Inc.), respectively.

The PSG records were reviewed by a single trained observer, blinded to the results of the Remmers Sleep Recorder test, according to standardized criteria. Hypopnea, a transient reduction in breathing, was defined according to two criteria. The first criterion was characterized by a 50% decrease in flow, followed by desaturation. The second criterion was determined as a 50% mechanical event followed by a desaturation or an arousal.

The Remmers Sleep Recorder collected nocturnal oxygen saturation data sampling at 1 Hz. The stored data was subsequently downloaded into a personal computer for interpretation by an automated off-line analysis algorithm. Based on this data, the Remmers Sleep Recorder software assigned an event marker to readings showing a drop in the sampled oxygen saturation value. A respiratory disturbance (RD) was designated when at least three consecutive falls in recorded oxygen saturation readings (event markers) occurred prior to a rise in this signal. Respiratory Disturbance Index (RDI) was calculated as a ratio of total number of RD to total monitor probe-on time.

Results

• Modified Bland-Altman plots revealed very small bias and rather constant variability.
• A strong correlation (97%) was observed between monitor RDI and PSG AHI, using either of the hypopnea criterion.
• Based on a clinical cut-off of RDI 15, the values for sensitivity and specificity are:
  - Sensitivity(2): 98%
  - Specificity(3): 88%
• Failure rate of 2%

Remmers Sleep Recorder
Results equivalent to PSG

Summary

This peer-reviewed study demonstrates that the Remmers Sleep Recorder can be used in the diagnosis of uncomplicated sleep apnea. This convenient, inexpensive and easy-to-use system provides a definitive evaluation in the home of respiratory status during sleep. The Remmers Sleep Recorder provides data that is equivalent to polysomnograph results but is more convenient, more relevant and less expensive. We believe that these developments will reduce waiting time and costs associated with the methods currently employed in diagnosis of sleep apnea.

Conducted in accordance with the University of Calgary's Conjoint Medical Research ethics committee.

Notes:

(1)Juan-Carlos Vázquez, Willis H Tsai, W Ward Flemons, Akira Masuda, Rollin Brant, Eric Hajduk, William A Whitelaw, John E Remmers., Automated analysis of digital oximetry in the diagnosis of obstructive sleep apnoea. Thorax 2000; 55; 302-307

(2) Sensitivity = True positive / (True positive + False negative)

(3) Specificity = True negative / (True negative + False positive)