Effie Pereira

Comparing a combination of validated questionnaires and level III portable monitor with polysomnography to diagnose and exclude sleep apnea.

STUDY OBJECTIVES Questionnaires have been validated as screening tools in adult populations at risk for obstructive sleep apnea (OSA). Portable monitors (PM) have gained acceptance for confirmation of OSA in some patients with a high pretest probability of the disorder. We evaluated the combined diagnostic utility of 3 validated questionnaires and a Level III PM in the diagnosis and exclusion of OSA, as compared with in-laboratory polysomnography (PSG) derived apnea hypopnea index (AHI). METHODS Consecutive patients referred to the Sleep Disorders Clinic completed 3 testing components: (1) 3 questionnaires (Berlin, STOP-Bang, and Sleep Apnea Clinical Score [SACS]); (2) Level III at-home PM (MediByte) study; and (3) Level I in-laboratory PSG. The utility of individual questionnaires, the Level III device alone, and the combination of questionnaires and the Level III device were compared with the PSG. RESULTS One hundred twenty-eight patients participated in the study (84M, 44F), mean ± SD age 50 ± 12.3years, BMI 31 ± 6.6 kg/m(2). At a PSG threshold AHI = 10, the PM derived respiratory disturbance index (RDI) had a sensitivity and specificity of 79% and 86%, respectively. The sensitivity and specificity for the other screening tools were: Berlin 88%, 25%; STOP-Bang 90%, 25%; SACS 33%, 75%. The sensitivity and specificity at a PSG AHI = 15 were: PM 77%, 95%; Berlin 91%, 28%; STOP-Bang 93%, 28%; SACS 35%, 78%. CONCLUSIONS Questionnaires alone, possibly given a reliance on sleepiness as a symptom, cannot reliably rule out the presence of OSA. Objective physiological measurement is critical for the diagnosis and exclusion of OSA.

Validation of the MediByte ® type 3 portable monitor compared with polysomnography for screening of obstructive sleep apnea

BACKGROUND Portable monitors are increasingly being used as a diagnostic screening tool for obstructive sleep apnea (OSA), and in-laboratory validation of these devices with polysomnography (PSG) is required. OBJECTIVE To assess the reliability of the MediByte (Braebon Medical Corporation, Canada) type 3 screening device compared with overnight PSG. METHODS To cover a range of OSA severity, a consecutive series of patients wore the screening device while simultaneously undergoing PSG. Data acquired from the screener and PSG were blinded and scored separately. The number of apneas and hypopneas per hour were calculated using recording time (respiratory disturbance index [RDI]) for the MediByte device, and sleep time (apnea-hypopnea index [AHI]) for PSG. RESULTS Data from 73 patients with a mean age of 53 years and body mass index of 32.2 kg⁄m2 showed high measurement association between the RDI and AHI, with a Pearson correlation of 0.92, accounting for 85% of the variance. Based on Bland-Altman measurement agreement, the mean difference between the RDI and AHI (-5.9±11.2 events⁄h) indicated screener under-reporting. For an AHI of greater than 15 events⁄h, the sensitivity and specificity of the screener was 80% and 97%, respectively; for an AHI of greater than 30 events⁄h, the positive predictive value was 100%, while the negative predictive value was 88%. CONCLUSION The MediByte device accurately identified patients without OSA and had a high sensitivity for moderate-to-severe OSA.

CPAP reduces hypercoagulability, as assessed by thromboelastography, in severe obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is associated with increased cardiovascular morbidity and mortality and hypercoagulability may be an underlying factor. We tested the hypotheses that patients with severe OSA are hypercoagulable and that two weeks of continuous positive airway pressure (CPAP) treatment reduces this hypercoagulability. In a prospective crossover study, twelve patients were randomized to either CPAP or no-CPAP for two weeks, a one week washout period, and then the other testing period for two weeks. Thromboelastography was used to assess coagulability at the start and end of each period and the apnoea-hypopnea indices (AHI) were measured at the end of each period. At baseline, ten patients had, compared to reference values, shorter clotting times, six increased rate of clot formation, twelve increased clot strength, and ten increased clotting indices. CPAP significantly reduced AHI (p=0.0003), clot strength (p=0.019) and clotting index (p=0.014). Hypercoagulability in patients with OSA can be detected by thromboelastography, and is reduced by CPAP.

The effect of inhaled menthol on upper airway resistance in humans: A randomized controlled crossover study

BACKGROUND Menthol (l-menthol) is a naturally-occurring cold receptor agonist commonly used to provide symptomatic relief for upper airway congestion. Menthol can also reduce the sensation of dyspnea. It is unclear whether the physiological action of menthol in dyspnea reduction is through its cold receptor agonist effect or whether associated mechanical changes occur in the upper airway. OBJECTIVE To determine whether menthol inhalation alters upper airway resistance in humans. METHODS A randomized, sham-controlled, single-blinded crossover study of inhaled menthol on upper airway resistance during semirecumbent quiet breathing in healthy subjects was conducted. Ten healthy participants (eight female) with a mean (± SD) age of 21±1.6 years completed the study. RESULTS Nasal resistance before testing was similar on both occasions. No differences were found in respiratory frequency (mean ± SEM) (menthol 17.0±1.1 cmH2O⁄L⁄s; sham 16.9±0.9 cmH2O⁄L⁄s), minute ventilation (menthol 7.7±0.5 cmH2O⁄L⁄s; sham 7.9±0.5 cmH2O⁄L⁄s) or total inspiratory time⁄total breath time (menthol 0.4±0.1 cmH2O⁄L⁄s; sham 0.4±0.1 cmH2O⁄L⁄s). The upper airway resistance was similar during menthol (3.47±0.32 cmH2O⁄L⁄s) and sham (3.27±0.28 cmH2O⁄L⁄s) (P=0.33) inhalation. CONCLUSION Inhalation of menthol does not alter upper airway resistance in awake human subjects.