Breathing Events Research Articles

MATPLM1, A MATLAB script for scoring of periodic limb movements: preliminary validation with visual scoring

Background and PurposeA Matrix Laboratory (MATLAB) script (MATPLM1) was developed to rigorously apply World Associations of Sleep Medicine (WASM) scoring criteria for periodic limb movements in sleep (PLMS) from bilateral electromyographic (EMG) leg recordings. This study compares MATPLM1 with both standard technician and expert detailed visual PLMS scoring. Methods and SubjectsValidation was based on a ‘macro’ level by agreement for PLMS/h during a night recording and on a ‘micro’ level by agreement for the detection of each PLMS from a stratified random sample for each subject. Data available for these analyses were from 15 restless leg syndrome (RLS) (age: 61.5 ± 8.5, 60% female) and nine control subjects (age: 61.4 ± 7.1, 67% female) participating in another study. ResultsIn the ‘micro’ analysis, MATPLM1 and the visual detection of PLMS events agreed 87.7% for technician scoring and 94.4% for expert scoring. The technician and MATPLM1 scoring disagreements were checked for 36 randomly selected events, 97% involved clear technician-scoring error. In the ‘macro’ analysis, MATPLM1 rates of PMLS/h correlated highly with visual scoring by the technician (r2 = 0.97) and the expert scorer (r2 = 0.99), but the technician scoring was consistently less than MATPLM1: median (quartiles) difference: 10 (5, 23). There was little disagreement with expert scorer [median (quartile) difference: −0.3 (−2.4, 0.3)]. ConclusionsThe MATPLM1 produces reliable scoring of PLMS that matches expert scoring. The standard visual scoring without careful measuring of events tends to significantly underscore PLMS. These preliminary results support the use of MATPLM1 as a preferred method of scoring PLMS for EMG recordings that are of a good quality and without significant sleep-disordered breathing events.

Misclassification of OSA Severity With Automated Scoring of Home Sleep Recordings

The advent of home sleep testing has allowed for the development of an ambulatory care model for OSA that most health-care providers can easily deploy. Although automated algorithms that accompany home sleep monitors can identify and classify disordered breathing events, it is unclear whether manual scoring followed by expert review of home sleep recordings is of any value. Thus, this study examined the agreement between automated and manual scoring of home sleep recordings. Two type 3 monitors (ApneaLink Plus [ResMed] and Embletta [Embla Systems]) were examined in distinct study samples. Data from manual and automated scoring were available for 200 subjects. Two thresholds for oxygen desaturation (≥ 3% and ≥ 4%) were used to define disordered breathing events. Agreement between manual and automated scoring was examined using Pearson correlation coefficients and Bland-Altman analyses. Automated scoring consistently underscored disordered breathing events compared with manual scoring for both sleep monitors irrespective of whether a ≥ 3% or ≥ 4% oxygen desaturation threshold was used to define the apnea-hypopnea index (AHI). For the ApneaLink Plus monitor, Bland-Altman analyses revealed an average AHI difference between manual and automated scoring of 6.1 (95% CI, 4.9-7.3) and 4.6 (95% CI, 3.5-5.6) events/h for the ≥ 3% and ≥ 4% oxygen desaturation thresholds, respectively. Similarly for the Embletta monitor, the average difference between manual and automated scoring was 5.3 (95% CI, 3.2-7.3) and 8.4 (95% CI, 7.2-9.6) events/h, respectively. Although agreement between automated and manual scoring of home sleep recordings varies based on the device used, modest agreement was observed between the two approaches. However, manual review of home sleep test recordings can decrease the misclassification of OSA severity, particularly for those with mild disease. ClinicalTrials.gov; No.: NCT01503164; www.clinicaltrials.gov.

Sleep breathing disorders and cognitive function in the elderly: an 8-year follow-up study. the proof-synapse cohort.

Sleep breathing disorder (SBD) may be an important factor in age-related cognitive decline. In a cohort of healthy elderly subjects, we performed an 8-y longitudinal study to assess whether changes in cognitive function occur in untreated elderly patients with SBD and without dementia and the factors implicated in these changes. A population-based longitudinal study. Clinical research settings. A total of 559 participants of the PROOF study aged 67 y at the study entry and free from neurological disorders were examined. N/A. Abnormal breathing events were defined by an apnea-hypopnea index (AHI) > 15. The raw cognitive data and averaged Z-scores for the attentional, executive, and memory functions were collected at the baseline and follow-up. At baseline, AHI > 15 was found in 54% of subjects with 18% having an AHI > 30. At follow-up, the presence of abnormal breathing events was associated with a slight but significant decline in the attentional domain (P = 0.01), which was more evident in the subjects with an AHI > 30 (P = 0.004). No significant changes over time were observed in the executive and memory functions. Several indices of chronic hypoxemia, defined either as a cumulative peripheral oxygen saturation (SpO2) < 90% or a minimal SpO2, accounted for portions of the variance in the decline in attention. All observed effects were small, accounting for 4-7% of variance in multivariate models. In healthy elderly subjects, various components of sleep breathing disorder at baseline were associated with small changes in selected cognitive functions specific to the attention domain after controlling for multiple comorbidities, such as sleepiness, hypertension, diabetes, anxiety, and depression. ClinicalTrials.gov identifiers NCT 00759304 and NCT 00766584.

An anatomically based analysis of objectively measured pediatric snoring: a pilot study.

To assess pediatric habitual snoring (PS) using home sleep test (HST) technology and attempt to correlate the objective components of PS to specific upper airway anatomy. In addition, the effects of adenotonsillectomy (±turbinoplasty) on objective measures of PS were evaluated. Prospective cohort study. Tertiary medical center. Pediatric patients with a chief complaint of snoring and probable obstructive sleep apnea underwent an HST (SNAP Diagnostics, Wheeling, Illinois) with a detailed acoustical snoring analysis prior to adenotonsillectomy (±turbinoplasty). During surgery, detailed anatomical measurements were performed and correlated to snoring analysis results. After surgery, patients were offered another HST with snoring analysis. Data analysis was performed using descriptive statistics and statistical correlation with attention to the multiple-comparisons paradox. Twenty-two patients (45% male; mean age, 5.4 years [range, 2.4-8.4 years]) completed the preoperative HST and operative measurements. Unlike typical adult snoring, only a minority of PS was from palatal flutter (mean palatal component, 24%; median, 10%). The resistance occurrence percentage (ROP, percentage of breathing events with snoring noise) was associated with body mass index (BMI; Spearman ρ=0.55; P=.017), subjective turbinate size (0.54; P=.032), palatal obstruction (0.63; P=.008), and mean oxygen saturation (-0.729; P=.0003) but not adenotonsillar hypertrophy. Twelve patients (54%) completed a postoperative HST. The ROP was significantly reduced (median, 20.5% vs 6.5%; P=.006, sign rank test) postoperatively. The magnitude of the ROP reduction was proportional to the volume of the removed tonsils (0.74; P=.022). Pediatric snoring has different acoustical characteristics than adult snoring. Objective PS is associated with BMI, turbinate size, and palatal obstruction. Adenotonsillectomy (±turbinoplasty) may significantly reduce objective PS.

Pseudoaneurysm of the mitral–aortic intervalvular fibrosa

Pseudoaneurysm of the mitral-aortic intervalvular fibrosa (P-MAIVF) is an infrequent but potentially life-threatening condition. Both transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) can detect P-MAIVF with sensitivity rates of 43 and 90 %, respectively. The typical finding of echocardiography is a pulsatile echo-free sac that expands in systole and collapses in diastole. Our review comprises 166 patients with P-MAIVF, including eight cases in our hospital and 158 cases from the literature. P-MAIVF is often associated with infection or surgical trauma. While it is likely to maintain an asymptomatic course, symptoms of shortness of breath, heart failure, valvular disease, chest pain, endocarditis, and cerebrovascular events are common clinical presentations. The recommended treatment is surgery. However, conservative therapy is an alternative approach for high-risk patients or when surgical treatment is refused. With the increasing incidence of cardiac surgery and infective endocarditis, a likely increment in the new diagnosis of pseudoaneurysm is expected.

Surfacers change their dive tactics depending on the aim of the dive: evidence from simultaneous measurements of breaths and energy expenditure.

Air-breathing divers are assumed to have evolved to apportion their time between surface and underwater periods to maximize the benefit gained from diving activities. However, whether they change their time allocation depending on the aim of the dive is still unknown. This may be particularly crucial for 'surfacers' because they dive for various purposes in addition to foraging. In this study, we counted breath events at the surface and estimated oxygen consumption during resting, foraging and other dives in 11 green turtles (Chelonia mydas) in the wild. Breath events were counted by a head-mounted acceleration logger or direct observation based on an animal-borne video logger, and oxygen consumption was estimated by measuring overall dynamic body acceleration. Our results indicate that green turtles maximized their submerged time, following this with five to seven breaths to replenish oxygen for resting dives. However, they changed their dive tactic during foraging and other dives; they surfaced without depleting their estimated stores of oxygen, followed by only a few breaths for effective foraging and locomotion. These dichotomous surfacing tactics would be the result of behavioural modifications by turtles depending on the aim of each dive.

An Objective, Anatomically Based Analysis of Pediatric Snoring

Objectives: The implications and anatomical basis of pediatric snoring (PS) remain largely unknown. The objectives of this study are to: (1) Objectively assess PS using home sleep test (HST) technology. (2) Attempt to correlate the objective components of PS to upper airway anatomy. (3) Objectively measure the effects of adenotonsillectomy (±turbinoplasty) on PS. Methods: Pediatric patients with a chief complaint of snoring and probable obstructive sleep apnea underwent a HST (SNAP Diagnostics, USA) with a detailed acoustical analysis of snoring prior to adenotonsillectomy (±turbinoplasty). During surgery, detailed anatomical measurements were performed and correlated with snoring analysis results. After surgery, patients were offered another HST with snoring analysis. Data analysis was performed using descriptive statistics and statistical correlation with attention to the multiple comparisons paradox. Results: Twenty-two patients (45% male; mean age, 5.4 years; range, 2.4-8.4 years) completed the preoperative HST and intra-operative measurements. Unlike typical adult snoring, only the minority of PS was from palatal flutter (mean palatal component = 24%, median = 10%). The resistance occurrence percentage (ROP, % of breathing events with snoring noise) was associated with body mass index (BMI; Spearmans Rho = 0.55, P = .017), subjective turbinate size (0.54, P = .032), lowest oxygen saturation (–0.46, P = .043), and palatal obstruction (0.62, P = .008) but not adenotonsillar hypertrophy. Ten patients (45%) completed a postoperative HST. The ROP was significantly reduced (median 20.5% vs 6.5%, P = .006 Sign rank test) postoperatively. The magnitude of the ROP reduction was directly proportional to the measured volume of the removed tonsils (0.74, P = .022). Conclusions: Pediatric snoring has different acoustical characteristics than adult snoring. Objective PS is associated with BMI, turbinate size, and palatal position/obstruction. Adenotonsillectomy (±turbinoplasty) significantly reduces objective PS.

Chemoreflexes, sleep apnea, and sympathetic dysregulation.

Obstructive sleep apnea (OSA) and hypertension are closely linked conditions. Disordered breathing events in OSA are characterized by increasing efforts against an occluded airway while asleep, resulting in a marked sympathetic response. This is predominantly due to hypoxemia activating the chemoreflexes, resulting in reflex increases in sympathetic neural outflow. In addition, apnea - and the consequent lack of inhibition of the sympathetic system that occurs with lung inflation during normal breathing - potentiates central sympathetic outflow. Sympathetic activation persists into the daytime, and is thought to contribute to hypertension and other adverse cardiovascular outcomes. This review discusses chemoreflex physiology and sympathetic modulation during normal sleep, as well as the sympathetic dysregulation seen in OSA, its extension into wakefulness, and changes after treatment. Evidence supporting the role of the peripheral chemoreflex in the sympathetic dysregulation seen in OSA, including in the context of comorbid obesity, metabolic syndrome, and systemic hypertension, is reviewed. Finally, alterations in cardiovascular variability and other potential mechanisms that may play a role in the autonomic imbalance in OSA are also discussed.

Sleep monitoring using body sounds and motion tracking.

This paper presents a system for sleep monitoring that can continuously analyze snoring, breathing, sleep phases and the activity of the patient during the night and the beginning of the day. Early results show that the system can be used to detect the occurrence of obstructive sleep apnea syndrome (OSAS). OSAS is traditionally diagnosed using polysomnography, which requires a whole night stay at the sleep laboratory of a hospital, where the patient is attached to multiple electrodes and sensors. Our system detects heartbeats, breathing, snoring, sleeping positions and movements using a special electret microphone and an inertial measurement unit (IMU). The system first analyses the sleep using the acoustic information provided by the electret microphone. From the acoustic information breathing events and heartbeats are identified. The system also analyses the patient's activity and positions from data delivered by the IMU. The information from both sensors is fused to detect sleep events. First experiments show that the system is capable of detecting and interpreting relevant data to improve sleep monitoring.

Design, development and experimental validation of a non-invasive device for recording respiratory events during bottle feeding.

In newborns, a poor coordination between sucking, swallowing and breathing may undermine the effectiveness of oral feeding and signal immaturity of Central Nervous System. The aim of this work is to develop and validate a non-invasive device for recording respiratory events of newborns during bottle feeding. The proposed device working principle is based on the convective heat exchanged between two hot bodies and the infants' breathing. The sensing elements are inserted into a duct and the gas exchanged by infants is conveyed into this duct thanks to an ad hoc designed system to be mounted on a commercial feeding bottle. Two sets of experiments have been carried out in order to investigate the discrimination threshold of the device and characterize the sensor response at oscillating flows. The effect of distance and tilt between nostrils and device, and the breathing frequency, have been investigated simulating nostrils and neonatal respiratory pattern. The device has a discrimination threshold lower than 0.5 L/min at both 10° and 20° of tilt. Distance for these two settings does not affect the threshold in the investigated range (10-20 mm). Moreover, the device is able to detect breathing events, and to discriminate the onset of expiratory phase, during a neonatal respiratory task delivered by a lung simulator. The results foster the successful application of this device to the assessment of the temporal breathing pattern of newborns during bottle feeding with a non-invasive approach.

Complementary methods to estimate population size of Antillean Manatees (Sirenia: Trichechidae) at Ciénaga de Paredes, Santander, Colombia

Information on manatee population size in Colombia is limited. This study was aimed at determining manatee population size in the Cienaga de Paredes (Colombia) by three different methods: boat-based surveys, side-scan Sonar (SSS) surveys and local interviews. Manatees were counted during breathing events by direct observation during the dry season, with the number of sightings per hour (NSH) and maximum number of simultaneous sightings (MNSS) used as occurrence indices. In 2002, we obtained an average NSH of 27.62 (SD=12.34) and the MNSS was 18; in 2010 the values were 55.71 (SD=29.79) and four respectively. Using linear-transect SSS data we estimated a population size of 12 individuals (%CV=27.3). The local community claimed that no hunting or entanglements had taken place in the area for over 20 years. These methods have pros and cons in terms of investment, effort, efficiency and community involvement, and their efficiency may vary in different seasons. Applying them in a complementary way and at greater spatial and temporal scales could enhance the accuracy of results.

Prevalence of bruxism in children with episodic migraine--a case-control study with polysomnography.

BackgroundParents of children with migraine have described a higher prevalence of sleep bruxism and other sleep disturbances in their children. The objective of this study was to use polysomnography to investigate the prevalence of bruxism during sleep in children with episodic migraine relative to controls.FindingsControls and patients were matched by sex, age, years of formal education, presence of snoring, arousals per hour, and respiratory events per hour.A total of 20 controls, between 6 and 12 years old, with no history of headache, recruited from public schools in Sao Paulo between 2009 and 2012, and 20 patients with episodic migraine recruited from the Headache Clinic at the Federal University of Sao Paulo between 2009 and 2012 underwent polysomnography.No intervention was performed before sleep studies.Among migraine patients, 27.5% experienced aura prior to migraine onset. The sleep efficiency, sleep latency, REM sleep latency, arousals per hour, percentage of sleep stages, and breathing events per hour were similar between groups. Five children (25%) with episodic migraine exhibited bruxism during the sleep study while this finding was not observed in any control (p = 0.045).ConclusionsOur data demonstrate that bruxism during sleep is more prevalent in children with episodic migraine. Further prospective studies will help elucidate the underlying shared pathogenesis between bruxism and episodic migraine in children.

Real-time prediction of disordered breathing events in people with obstructive sleep apnea.

Conventional therapies for obstructive sleep apnea (OSA) are effective but suffer from poor patient adherence and may not fully alleviate major OSA-associated cardiovascular risk factors or improve certain aspects of quality of life. Predicting the onset of disordered breathing events in OSA patients may lead to improved strategies for treating OSA and inform our understanding of underlying disease mechanisms. In this work, we describe a deployable system capable of performing real-time predictions of sleep disordered breathing events in patients diagnosed with OSA, providing a novel approach for gaining insight into OSA pathophysiology, discovering population subgroups, and improving therapies. LArge Memory STorage and Retrieval artificial neural networks with 864 different configurations were applied to polysomnogram records from 64 patients. Wavelet transforms, measures of entropy, and other statistics were applied to six physiological signals to provide network inputs. Approximate statistical tests were used to determine the best performing network for each patient. The most important predictors of disordered breathing events in OSA patients were determined by analyzing internal network parameters. The average optimized individual prediction sensitivity and specificity were 0.81 and 0.77, respectively. Predictions were better than random guessing for all OSA patients. Analysis of internal network parameters revealed a high degree of heterogeneity among disordered breathing event predictors and may reveal patient subgroups. We report the first practical system to predict individual disordered breathing events in a heterogeneous group of patients diagnosed with OSA. The pattern of disordered breathing predictors suggests variable underlying pathophysiological mechanisms and highlights the need for an individualized approach to OSA diagnosis, therapy, and management.

Hypopnea: ‘rule of thumb’ or ruler and plumb?

Hypopnea: ‘rule of thumb’ or ruler and plumb?

Does Positive Airway Pressure Therapy Result in Improved Sleep Quality?

Introduction:Positive airway pressure (PAP) therapy is the gold-standard for obstructive sleep apnea (OSA) management. While it is known that PAP is efficacious for controlling breathing events during sleep when it is worn at the right pressure for the amount of time prescribed, there is less clear data on how well it improves sleep quality. There are few studies that have examined the effectiveness of PAP therapy on sleep quality.Methods:OSA participants (n = 241) from a larger trial examining a PAP adherence were included. Participants were provided with PAP instruction and followed at 2 months and 4 months. PAP adherence was measured as the number of hours per night at prescribed pressure, an objective measure of treatment adherence. The Pittsburgh Sleep Quality Index (PSQI) was used as the primary measure of sleep quality.Results:The PSQI was significantly correlated with PAP adherence at both the 2-month and 4-month time points, such that lower sleep quality was associated with lower PAP use. This finding held for the sleep disturbance subscale of the PSQI. Over 55% of those using PAP therapy at the 4-month time point continued to report significantly disturbed sleep.Discussion:This study shows that PAP therapy does not appear to improve sleep quality to a degree that would be expected. Over half of those patients using PAP therapy still experienced disturbed sleep. Whether the disturbed sleep is directly attributable to the PAP device itself or to disturbed sleep secondary to uncontrolled OSA when PAP is not worn is worthy of further investigation.

Procedural sedation with dexmedetomidine during ablation of atrial fibrillation: a randomized controlled trial

Procedural sedation by non-anaesthesiologists with GABAergic anaesthetics has the potential risk of fatal respiratory depression. Dexmedetomidine works its sedative action via α2-adrenergic receptors, and is less associated with respiratory depression. We tested the usability of dexmedetomidine as a procedural sedative during ablation of atrial fibrillation (AF). Consecutive patients were randomized to be treated with dexmedetomidine (n = 43) or thiamylal (n = 44) as sedatives during AF ablation. Apnoeic and body movement events were monitored using a novel portable respiratory monitor, the SD-101, during the procedure. Although the majority of the patients receiving dexmedetomidine required rescue sedations with thiamylal, the respiratory disturbance index (RDI) defined as the total number of sleep-disordered breathing events divided by the recording time (10.4 ± 5.1 vs. 18.2 ± 8.1 events/h; P < 0.0001) and movement index defined as the number of body movement events per hour (7.6 ± 6.1 vs. 11.0 ± 5.5 events/h; P = 0.0098) were both significantly lower in the dexmedetomidine arm than in the thiamylal arm. A multivariate linear regression analysis including potential factors revealed that dexmedetomidine vs. thiamylal was solely and independently associated with the RDI (β = -0.62; P = 0.0031). The occurrence of hypotension [9 (21%) vs. 4 (9%); P = 0.14] and bradycardia [4 (9%) vs. 4 (9%); P = 1.0] were similar in the patients with dexmedetomidine and thiamylal. Procedural sedation with dexmedetomidine may assure safety and patient immobility during AF ablation, and therefore may be a potential alternative for that with GABAergic anaesthetics.

Impact of respiratory events associated with autonomic arousals using type 1 sleep laboratory and type 3 ambulatory recordings

Introduction The aim was to compare standard apnea-hypopnea indices (AHI) and respiratory disturbance indices with RERA (RDI) to indices including breathing events with autonomic arousals (AA) recorded in suspected sleep-disordered breathing populations using AASM type 1 and 3 recordings. Materials and methods Type 1: 73 subjects underwent overnight in-laboratory polysomnography. The following respiratory outcomes were scored: 4% oxygen desaturation index (ODI), apnea-hypopnea index (AHI), respiratory disturbance index with EEG arousals (RDIe), and RDI with AA (RDIa). Type 3: 89 subjects underwent home recordings for one night with ambulatory monitoring. As above, ODI, AHI, and RDIa were scored (not RDIe). Patients were classified into severity categories as no (0) to mild (1), moderate (2), and severe (3). Analyses performed were: (1) frequency of migration from lower to higher category; (2) Bland–Altman (B-A) to assess agreement between AHI, RDIe, and RDIa (type 1 monitoring), and AHI and RDIa (type 3 monitoring) (limits of agreement defined as the interval of the mean difference ±1.96 ×SD). Results Type 1: A linear severity trend was observed for all mean values of ODI, AHI, RDIe, and RDIa. 29% (21/73) of subjects migrated using RDIe vs. RDIa: 14% from 0 to 1, 11% 1 to 2, and 4% 2 to 3. B-A plots show a 6.63 mean difference (interval [–1.39; 14.66]) for RDIa vs. AHI, and 3.95 difference for RDIa vs. RDIe with interval [–2.83; 10.73]. Type 3: No linear trend was observed for ODI, AHI, and RDIa. 57% (45/79) of subjects migrated using AHI vs. RDIa: 33% from 0 to 1, 14% 1 to 2, 4% 2 to 3, and 4% 0 to 2. B-A plots show a 6.91 mean difference between RDIa and AHI (RDIa-AHI) with limits of agreement [–2.90; 16.73]. Conclusion Autonomic arousal events produce a similar increase in indices over AHI in type 1 and type 3 recordings, with a smaller difference compared to RDIe for type 1. Presumably, AA events captured most of the EEG arousal events not counted in type 3 studies. Unsurprisingly, the impact on AHI severity change was greater in the type 3 study (no EEG). The significance of events with AA remains unclear: their identification in type 3 studies may lead to better concordance with type 1 studies and improved disease definition. Acknowledgements Supported by Canada Res Chair and CHUM.

An animal model of obstructive sleep apnea in rabbit

An animal model of obstructive sleep apnea (OSA) may help to investigate the pathophysiology of this disorder and develop appropriate treatments. We investigated the feasibility of a rabbit model of OSA. Animal study. Twelve New Zealand white rabbits were injected at the base of their tongues under endoscopic guidance with liquid silicone (experimental group, n = 6) or normal saline (control group, n = 6). Polysomnography was performed before and after injection. The development of OSA and changes in sleep parameters were compared between the two groups. Before injection, all rabbits showed normal breathing during sleep without hypopnea. In the silicone group, the rabbits had a mean of 29.9 ± 6.9 hypopneas/hour and a mean of 10.4 ± 3.1 apneas/hour 1 month after silicone injection and 28.4 ± 6.9 hypopneas/hour and 10.0 ± 3.3 apneas/hour 3 months after silicone injection (P < 0.05). Mean total sleep time decreased from 260.3 ± 70.2 minutes at baseline to 152.5 ± 38.8 minutes 1 month and 206.8 ± 60.3 minutes 3 months after injection, with a decrease in stage II sleep. In the saline group, however, there were no breathing events during sleep. These results show that silicone injections into the tongue base of rabbits can result in OSA.

Bench test evaluation of adaptive servoventilation devices for sleep apnea treatment.

Adaptive servoventilation devices are marketed to overcome sleep disordered breathing with apneas and hypopneas of both central and obstructive mechanisms often experienced by patients with chronic heart failure. The clinical efficacy of these devices is still questioned. This study challenged the detection and treatment capabilities of the three commercially available adaptive servoventilation devices in response to sleep disordered breathing events reproduced on an innovative bench test. The bench test consisted of a computer-controlled piston and a Starling resistor. The three devices were subjected to a flow sequence composed of central and obstructive apneas and hypopneas including Cheyne-Stokes respiration derived from a patient. The responses of the devices were separately evaluated with the maximum and the clinical settings (titrated expiratory positive airway pressure), and the detected events were compared to the bench-scored values. The three devices responded similarly to central events, by increasing pressure support to raise airflow. All central apneas were eliminated, whereas hypopneas remained. The three devices responded differently to the obstructive events with the maximum settings. These obstructive events could be normalized with clinical settings. The residual events of all the devices were scored lower than bench test values with the maximum settings, but were in agreement with the clinical settings. However, their mechanisms were misclassified. The tested devices reacted as expected to the disordered breathing events, but not sufficiently to normalize the breathing flow. The device-scored results should be used with caution to judge efficacy, as their validity depends upon the initial settings.

Arousal from sleep: implications for obstructive sleep apnea pathogenesis and treatment

Historically, brief awakenings from sleep (cortical arousals) have been assumed to be vitally important in restoring airflow and blood-gas disturbances at the end of obstructive sleep apnea (OSA) breathing events. Indeed, in patients with blunted chemical drive (e.g., obesity hypoventilation syndrome) and in instances when other defensive mechanisms fail, cortical arousal likely serves an important protective role. However, recent insight into the pathogenesis of OSA indicates that a substantial proportion of respiratory events do not terminate with a cortical arousal from sleep. In many cases, cortical arousals may actually perpetuate blood-gas disturbances, breathing instability, and subsequent upper airway closure during sleep. This brief review summarizes the current understanding of the mechanisms mediating respiratory-induced cortical arousal, the physiological factors that influence the propensity for cortical arousal, and the potential dual roles that cortical arousal may play in OSA pathogenesis. Finally, the extent to which existing sedative agents decrease the propensity for cortical arousal and their potential to be therapeutically beneficial for certain OSA patients are highlighted.