Sleep Research laboratory

Toronto, Canada

Sleep Research laboratory

Toronto, Canada
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Salloum A.,Sleep Research Laboratory | Rowley J.A.,Sleep Research Laboratory | Mateika J.H.,Sleep Research Laboratory | Mateika J.H.,Wayne State University | And 3 more authors.
American Journal of Respiratory and Critical Care Medicine | Year: 2010

Rationale: There is increasing evidence of increased ventilatory instability in patients with obstructive sleep apnea (OSA), but previous investigations have not studied whether the hypocapnic apneic threshold is altered in this group. Objectives: To compare the apneic threshold, CO 2 reserve, and controller gain between subjects with and without OSA matched for age, sex, and body mass index. Methods: Hypocapnia was induced via nasal mechanical ventilation for 3 minutes. Cessation of mechanical ventilation resulted in hypocapnic central hypopnea or apnea depending upon the magnitude of the hypocapnia. The apnea threshold (PETCO2-AT) was defined as the measured PETCO2 at which the apnea closest to the last hypopnea occurred. The CO2 reserve was defined as the change in PET CO2 between eupneic PETCO2 and PETCO2-AT. Controller gain was defined as the ratio of change in VE between control and hypopnea or apnea to the δPETCO2. Measurements and Main Results: Eleven pairs of subjects were studied. There was no difference in the PETCO2-AT between the two groups. However, the CO2 reservewassmaller in the subjects withOSA(2.2± 0.6 mm Hg) compared with the control subjects (4.5 ± 1.4 mm Hg; P < 0.001). The controller gain was increased in the subjects with OSA (3.7 ± 1.3 L/min/mm Hg) compared with the control subjects (1.6 ± 0.5 L/min/mm Hg; P < 0.001). Controller gain decreased and CO2 reserve increased in seven subjects restudied after using continuous positive airway pressure for 1 month. Conclusions: Ventilatory instability is increased in subjects with OSA and is reversible with the use of continuous positive airway pressure.


Alshaer H.,Sleep Research Laboratory | Alshaer H.,University of Toronto | Garcia M.,Ibero-American University of Mexico | Radfar M.H.,University of Toronto | And 3 more authors.
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2011

The similarities between unvoiced speech sounds and turbulent breath sounds were used to detect change in sound characteristics caused by narrowing of the upper airway (UA), similar to that occurring in obstructive sleep apnea (OSA). In 18 awake subjects, UA resistance (RAU), an index of UA narrowing, was measured simultaneously with breath sounds recording. Linear Prediction Coding was applied on turbulent inspiratory sounds drawn from low and high RAU conditions and K-means was used to cluster the resulting coefficients. The resulting 2 clusters were tested for agreement with the underlying RAU status. Distinct clusters were formed when R UA increased relatively high but not in cases with lower rise in RUA (P<0.01 for all indicators.) This is the first work to show the utility of LPC in breath sounds analysis confirmed by an objective indicator or UA narrowing. © 2011 IEEE.


Shahid A.,University of Toronto | Shen J.,University of Toronto | Shen J.,Sleep Research laboratory | Shapiro C.M.,University of Toronto | Shapiro C.M.,Sleep Research laboratory
Journal of Psychosomatic Research | Year: 2010

Sleepiness and fatigue are terms commonly used in clinical practice and research. At times sleepiness and fatigue are used interchangeably; however, each of them has distinct implications for diagnosis and treatment. The objective of this article is to review the psychometric properties of the measurements of sleepiness and fatigue. Although there are objective and subject measures to evaluate sleepiness, only rating scales are available to assess fatigue. Further research should be directed toward exploring the potential mechanisms underlying the measurements of sleepiness and fatigue. Establishing objective assessing instruments to evaluate fatigue and clarifying the relationship between objective and subjective assessments of sleepiness are crucially needed. © 2010 Elsevier Inc.


Hummel R.,Sleep Research Laboratory | Bradley T.D.,Sleep Research Laboratory | Fernie G.R.,Sleep Research Laboratory | Chang S.J.I.,University of Toronto | Alshaer H.,Sleep Research Laboratory
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2015

Polysomnography is a comprehensive modality for diagnosing sleep apnea (SA), but it is expensive and not widely available. Several technologies have been developed for portable diagnosis of SA in the home, most of which lack the ability to detect sleep status. Wrist actigraphy (accelerometry) has been adopted to cover this limitation. However, head actigraphy has not been systematically evaluated for this purpose. Therefore, the aim of this study was to evaluate the ability of head actigraphy to detect sleep/wake status. We obtained full overnight 3-axis head accelerometry data from 75 sleep apnea patient recordings. These were split into training and validation groups (2/1). Data were preprocessed and 5 features were extracted. Different feature combinations were fed into 3 different classifiers, namely support vector machine, logistic regression, and random forests, each of which was trained and validated on a different subgroup. The random forest algorithm yielded the highest performance, with an area under the receiver operating characteristic (ROC) curve of 0.81 for detection of sleep status. This shows that this technique has a very good performance in detecting sleep status in SA patients despite the specificities in this population, such as respiration related movements. © 2015 IEEE.

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