Clinical significance of pulse rate rise during sleep as a screening marker for the assessment of sleep fragmentation in sleep-disordered breathing

Nocturnal Pulse Event Frequency Is Reduced in Multiple System Atrophy

Risk of sudden death in multiple system atrophy (MSA) is greatest during sleep with unknown mechanisms. We compared nocturnal pulse event frequency in 46 MSA patients and age-/sex-matched controls undergoing overnight pulse oximetry. Nocturnal oxyhemoglobin desaturation indices and pulse event indices (PEIs) were recorded, and relationships between pulse oximetry variables and survival were analyzed. MSA patients had lower PEI (3.1 ± 5.3 vs. 12.8 ± 10.8, p < 0.001) despite greater hypoxic burden and similar frequency of respiratory events. Nocturnal pulse events were not associated with severity of daytime autonomic failure. Two MSA patients had suspected sudden death, both with severely reduced PEI. MSA patients have fewer nocturnal pulse events compared with controls, despite similar respiratory event frequency, suggesting abnormal cardiac responses to sleep-disordered breathing. Whether this contributes to sudden death in MSA requires further study. ANN NEUROL 2023;93:205-212.

A differential of the left eye and right eye neurological pupil index is associated with discharge modified Rankin scores in neurologically injured patients

Background

Automated infrared pupillometry (AIP) and the Neurological Pupil index (NPi) provide an objective means of assessing and trending the pupillary light reflex (PLR) across a broad spectrum of neurological diseases. NPi quantifies the PLR and ranges from 0 to 5; in healthy individuals, the NPi of both eyes is expected to be ≥ 3.0 and symmetric. AIP values demonstrate emerging value as a prognostic tool with predictive properties that could allow practitioners to anticipate neurological deterioration and recovery. The presence of an NPi differential (a difference ≥ 0.7 between the left and right eye) is a potential sign of neurological abnormality.

Methods

We explored NPi differential by considering the modified Rankin Score at discharge (DC mRS) among patients admitted to neuroscience intensive care units (NSICU) of 4 U.S. and 1 Japanese hospitals and for two cohorts of brain injuries: stroke (including subarachnoid hemorrhage, intracerebral hemorrhage, acute ischemic stroke, and aneurysm, 1,200 total patients) and 185 traumatic brain injury (TBI) patients for a total of more than 54,000 pupillary measurements.

Results

Stroke patients with at least 1 occurrence of an NPi differential during their NSICU stay have higher DC mRS scores (3.9) compared to those without an NPi differential (2.7; P < .001). Patients with TBI and at least 1 occurrence of an NPi differential during their NSICU stay have higher discharge modified Rankin Scale scores (4.1) compared to those without an NPi differential (2.9; P < .001). When patients experience both abnormalities, abnormal (NPi < 3.0) and an NPi differential, the latter has an anticipatory relationship with respect to the former (P < .001 for z-score skewness analysis). Finally, our analysis confirmed ≥ 0.7 as the optimal cutoff value for the NPi differential (AUC = 0.71, P < .001).

Conclusion

The NPi differential is an important factor that clinicians should consider when managing critically ill neurological injured patients admitted to the neurocritical care units.

Trial registration

NCT02804438, Date of Registration: June 17, 2016.

Scoring heart rate increases as a surrogate arousal marker on portable monitor studies for obstructive sleep apnea: Impact on diagnostic accuracy and clinical decision-making

Cortical arousal-related hypopneas are not scored on type 3 home devices, which therefore limits their diagnostic accuracy for obstructive sleep apnea. The objective of this study was to evaluate whether scoring heart rate accelerations as surrogate markers of arousal improves type 3 portable monitor diagnostic agreement compared with polysomnography and improves therapeutic decision-making. We prospectively recruited patients evaluated for obstructive sleep apnea to undergo in-laboratory simultaneous full polysomnography + type 3 portable monitoring. Hypopnea events were scored on portable monitor studies with and without autonomic scoring, which was defined as an associated increase in pulse oximetry-derived heart rate ≥6 beats per min (autonomic hypopnea). Portable monitor diagnostic agreement compared with polysomnography with and without autonomic hypopnea scoring was assessed. We also evaluated whether reporting autonomic hypopnea scoring improves portable monitor clinical treatment decision agreement after four physicians reviewed clinical data and sleep study results (polysomnography, portable monitor with autonomic hypopnea, portable monitor without autonomic hypopnea). Eighty-two participants completed simultaneous polysomnography and in-laboratory portable monitor studies. Scoring autonomic hypopnea resulted in a decreased mean difference between in-laboratory portable monitor respiratory event index and polysomnography apnea-hypopnea index in Bland-Altman analysis (mean difference 14.6 per hr without versus 6.1 per hr with autonomic hypopnea scoring [p ˂ 0.01]), and increased intraclass correlation from 0.769 to 0.844. Inclusion of autonomic hypopnea scoring resulted in better accuracy between portable monitor and polysomnography expert's treatment decisions, and ultimately resulted in 24% fewer additional polysomnographies requested. The addition of pulse oximetry heart rate increases for autonomic hypopnea scoring during portable monitor resulted in better diagnostic agreement, improved clinical decision-making and reduced additional polysomnography testing.

Accuracy of portable devices in sleep apnea using oximetry-derived heart rate increases as a surrogate arousal marker

PURPOSE

Type 3 home study (HS) monitors do not detect cortical arousal-related hypopneas and may therefore underestimate the polysomnography (PSG)-based apnea-hypopnea index (AHI). Our aim was to test the hypothesis that scoring hypopneas using heart rate accelerations as a surrogate marker for cortical arousal (autonomic hypopnea; AnH) improves the accuracy of HS for OSA diagnosis, using PSG AHI as the diagnostic gold standard.

METHODS

We retrospectively identified patients referred for OSA who underwent complete PSG following an initial inconclusive HS. Respiratory events were scored using AASM research (Chicago) criteria with additional HS scoring for AnH, defined as hypopneas based on flow criteria associated with an increase in pulse oximetry-derived heart rate ≥ 6 beats/min.

RESULTS

A total of 178 patients met inclusion criteria, with mean (±SD) HS AHI = 4.4 ± 4.2/h, which increased to 8.5 ± 5.3/h with AnH scoring. The hypopnea arousal index on subsequent PSG was 7.6 ± 7.7/h, with total AHI 15.6 ± 11.9/h. Bland-Altman analysis showed improved agreement between HS and PSG AHI (mean difference 11.2/h (95%CI 33.6, - 11.1) without vs. 7.2/h (95%CI 29.6, - 15.4) with AnH scoring). Overall diagnostic accuracy was improved with AnH scoring as reflected by an increased area under the receiver-operating characteristic curve for AHI thresholds of 10 and 15 events/h.

CONCLUSIONS

In this retrospective analysis, the diagnostic accuracy of type 3 HS was improved by the inclusion of hypopnea-associated heart rate increases as a surrogate marker of arousal. Prospective studies are warranted to evaluate the impact of AnH scoring on clinical decision-making and patient outcomes.

Reliability of autonomic activations as surrogates of cortical arousals in ventilated patients affected by amyotrophic lateral sclerosis

PURPOSE

The study aims to evaluate the performance of autonomic activations as a tool to assess sleep fragmentation and to recognize hypopneas in patients with amyotrophic lateral sclerosis (ALS) under non-invasive mechanical ventilation and secondarily, to evaluate, in patients with the same disease, the relationship between disruption of autonomic nervous system (ANS) activity and the usefulness of the autonomic activations as surrogates of cortical arousals.

METHODS

Sixteen ALS patients underwent simultaneous polysomnography and portable cardiorespiratory monitoring (PM). On the polysomnography, standard rules were used for scoring arousals and respiratory events. On the PM, autonomic arousals were scored as ≥ 15% heart rate (HR) increase with a ≥ 35% pulse wave amplitude (PWA) reduction, HR increase ≥ 20%, or PWA decrease ≥ 40%. Nocturnal HR variability was analyzed in the ALS patients and in 11 control subjects as an index of ANS activity.

RESULTS

Synchronized epoch by epoch analysis of the polysomnography and PM recordings showed that only 31.0 (22.5-58.7)% cortical and 36.1 (20.5-47.2)% autonomic arousals were associated with one another. Among hypopneas scored at polysomnography, 71.7% were associated with a cortical arousal but not with a desaturation. On average, HR variability in ALS showed signs of depressed ANS activity that was particularly evident in the patients where the cortical arousals exceeded the autonomic ones.

CONCLUSIONS

In ventilated ALS patients, autonomic activations may hardly have a role as surrogates of cortical arousals for assessment of sleep fragmentation and for respiratory scoring. Depression of ANS activity may be related to their poor performance.

Improving detection of obstructive sleep apnoea by overnight oximetry in children using pulse rate parameters

PURPOSE

Overnight oximetry is a simple tool for investigation of obstructive sleep apnoea (OSA) in children, but only severe cases will be detected, and children with obstructive events resulting in arousal, but not desaturation, will have a normal (inconclusive) result. We hypothesised that pulse rate rises using pulse rate indices per hour (PRI) and pulse rate standard deviation (PR-SD) automatically calculated from commercially available software would improve oximetry as a diagnostic tool.

METHODS

Children having home overnight oximetry for suspected OSA were identified over 12 months, and those with a normal result who went on to have polysomnography (PSG) were included. Oximetry, including PR-SD and PRI (rises of 8, 10 and 15 beats/min per hour), was analyzed using commercially available software. PR parameters were compared between those with OSA (obstructive apnoea-hypopnoea index (OAHI) >1 event/h) and those without OSA.

RESULTS

One hundred sixteen children had normal oximetry, of whom 93 (median age 4.5 years; 55 % M) had PSG. Fifty-seven of 93 (61 %) children had OSA (median OAHI 4.5 events/h, range 1.1-24). PR-SD was not different between the OSA and non-OSA groups (p = 0.87). PRI tended to be higher in those with OSA, but there was considerable overlap between the groups: PRI-8 (mean ± SD 58.5 ± 29.0/h in OSA group vs 48.6 ± 20.2/h in non-OSA group, p = 0.07), PRI-10 (45.1 ± 25.0 vs 36.2 ± 16.7, p = 0.06) and PRI-15 (24.4 ± 14.5 vs 18.9 ± 9.0, p = 0.04). A PRI-15 threshold of >35/h had specificity of 97 % for OSA.

CONCLUSION

The PRI-15 shows promise as an indicator of OSA in children with normal oximetry.

Use of a level 3 portable monitor for the diagnosis and management of sleep disordered breathing in an inpatient tertiary care setting

BACKGROUND

Sleep-disordered breathing (SDB) may impact the course of medical illness among hospitalized patients. Access to testing during hospitalization to assess this may be limited by wait times for laboratory polysomnography. Level 3 portable monitoring (PM) may provide an alternative.

OBJECTIVE

To assess the rate of technically adequate studies, diagnostic information obtained and impact on patient management of inpatient PM studies performed for SDB.

METHODS

A retrospective review of 114 PM (Embletta, Natus Inc, Canada) records from the past two years was performed. Studies were ordered by pulmonologists, initiated by respiratory therapists and performed unattended on inpatient units. Admitting diagnoses, indication for sleep study, diagnostic information obtained from recordings and change in clinical management subsequent to PM were determined from medical charts.

RESULTS

Of 114 studies reviewed, 99 (87%) met predetermined criteria for adequate signal quality and duration. Five studies could not be interpreted due to inadequate data, yielding an overall success rate of 83% (94 of 114). Of 86 studies performed for diagnosis, clinical and PM data supported a new diagnosis of SDB in 55 patients, of which 23 (42%) were started on positive pressure therapy. Thirteen PM studies were performed during SDB treatment. All were technically adequate and six of 13 demonstrated new or persistent SDB. Results from PM testing informed clinical management during hospitalization in 70 (61%) cases.

CONCLUSION

Unattended level 3 PM studies are technically feasible in hospitalized patients and may provide information that influences clinical management.

Screening for obstructive sleep apnoea in obesity and diabetes--potential for future approaches

BACKGROUND

It is recognised that sleep-disordered breathing (SDB), in particular, obstructive sleep apnoea (OSA) is associated with obesity and diabetes. The complications of OSA include dysregulation of metabolic and cardiovascular homeostasis. With the growing population of diabetes and obesity globally, it is becoming apparent that identifying and screening patients who are at risk is becoming increasingly crucial. Many patients may remain unaware of the potential diagnosis and continue to be undiagnosed. The high prevalence of OSA poses a demanding challenge to healthcare providers in order to provide sufficient resources and facilities for patient diagnosis and treatment.

DESIGN

In this article, we review the evidence in favour of screening populations deemed to be at increased risk of OSA, with particular reference to patients with obesity and diabetes. We consider the recent advances in potential screening methods that may allow new prognostic and predictive tools to be developed. A detailed search of Medline and Web of Science electronic databases for relevant articles in English was performed.

RESULTS

Apart from the use of screening tools such as questionnaires and clinical decision models, there is increasing evidence to suggest that there are differences in biological parameters in patients with OSA. Although further studies are required, there may be potential for such biomarkers to contribute to and augment the screening process. However, the significance of such biological tools remains to be elucidated.

CONCLUSIONS

A fundamental role for improved screening in patients with conditions such as obesity and diabetes can enable early interventions that may improve health outcomes relating to the adverse consequences of OSA. The future will see further research being carried out in the development of potential screening methods with emphasis on the selection of patients at risk of sleep disorders, thereby allowing more detailed physiological studies to be carried out where needed.

Effect of continuous positive airway pressure on proteinuria in obstructive sleep apnea

Obstructive sleep apnea (OSA) is common in patients with renal disease, and an association between OSA and proteinuria has been proposed. However, the effect on proteinuria of OSA treatment with continuous positive airway pressure (CPAP) is unknown. We experienced a case of severe OSA, where proteinuria was clearly improved after CPAP initiation without any changes of medication or body weight. The remarkable reduction of repetitive apnea and hypopnea by CPAP might ameliorate proteinuria by lessening renal hypoxia and sympathetic nerve activation. This case suggests that CPAP is a promising option for OSA with proteinuria.

Pulse transit time in screening sleep disordered breathing in an elderly population: the PROOF-SYNAPSE study

STUDY OBJECTIVES

Pulse transit time (PPT) has been introduced as a useful screening tool to diagnose sleep disordered breathing (SDB). Since the prevalence of SDB increases with age, the question is whether PTT could be used to diagnose SDB in the elderly. We assess the effectiveness of PTT for SDB screening in a large healthy elderly population.

SETTING

Community-based sample in home and research clinical settings.

INTERVENTION

N/A.

PARTICIPANTS

Seven hundred eighty volunteers, free of cardiac and neurologic disease, aged 68.6 ± 1.0 years, underwent ambulatory polygraphy to measure the apnea-hypopnea index (AHI). The presence of SDB was defined as an AHI of 15 or greater. The PTT was continuously monitored during the nocturnal study, and the overall autonomic arousal index (AAI) was calculated.

RESULTS

SDB was diagnosed in 447 (57.3%) subjects. In these subjects, the Bland-Altman plot for AAI revealed an underestimation with a bias of -8.04 ± 16.55 events per hour (mean ± 95% confidence interval). Receiver operating characteristic curves constructed for an AHI of 15 or greater defined an area under the curve of 0.67 and a cutoff point to AAI 32.3 events per hour, giving a sensitivity of 70.5% and a specificity of 54.7%. For prediction of an AHI of at least 30, the area under the curve was equal to 0.74 for a cutoff point of 56.3 events per hour, giving a better specificity (94.7%) but a lower sensitivity (32.2%).

CONCLUSIONS

In a healthy older population, the AAI showed moderate sensitivity for predicting SDB. This data does not allow us to use PTT as a screening tool for the diagnosis of SDB in the elderly.

CLINICAL TRIAL REGISTRATION

NCT 00759304 and NCT 00766584.

The Epworth Sleepiness Scale: self-administration versus administration by the physician, and validation of a French version

BACKGROUND/OBJECTIVES

The Epworth Sleepiness Scale (ESS) measures sleepiness and is used for, among others, patients with obstructive sleep apnea (OSA). The questionnaire is usually self-administered, but may be physician administered. The aim was to compare the two methods of administration and to validate a French version.

METHODS

Consecutive patients presenting to the sleep clinic at a tertiary care centre completed a self-administered questionnaire containing the ESS. During the medical interview the same day, one of three pulmonologists who specialized in sleep medicine administered the ESS. Correlations with the apnea-hypopnea index and mean sleep latencies were used to assess construct validity, while results of previous self-administered ESS questionnnaires in untreated and recently treated OSA patients were used to test reproducibility and longitudinal construct validity, respectively.

RESULTS

In OSA patients, the ESS weakly correlated with the apnea-hypopnea index (r=0.224; P=0.05; n=120) and negatively with mean sleep latency. For untreated patients (test-retest), the mean (+/- SD) average score was unchanged (10.3+/-6.0 to 10.8+/-6.5; P=0.35; n=56) after a median of seven months. With continuous positive airway pressure use, the mean score decreased from 12.4+/-6.8 to 7.6+/-5.0 after 40.2 months (P<0.0001; n=68). For all subjects, the ESS score obtained by the physician was less than that of the self-administered result (9.4+/-5.9 versus 8.5+/-5.8; P<0.0001 [paired t test]; n=188).

CONCLUSIONS

In a sleep clinic population, the French version of the ESS performed similarly to the English version. However, the systematic underscoring during physician administration may be important to consider in the research setting if questionnaire administration methods are not consistent.

Pulse wave amplitude drops during sleep are reliable surrogate markers of changes in cortical activity

BACKGROUND

During sleep, sudden drops in pulse wave amplitude (PWA) measured by pulse oximetry are commonly associated with simultaneous arousals and are thought to result from autonomic vasoconstriction. In the present study, we determine whether PWA drops were associated with changes in cortical activity as determined by EEG spectral analysis.

METHODS

A 20% decrease in PWA was chosen as a minimum for a drop. A total of 1085 PWA drops from 10 consecutive sleep recordings were analyzed. EEG spectral analysis was performed over 5 consecutive epochs of 5 seconds: 2 before, 1 during, and 2 after the PWA drop. EEG spectral analysis was performed over delta, theta, alpha, sigma, and beta frequency bands. Within each frequency band, power density was compared across the five 5-sec epochs. Presence or absence of visually scored EEG arousals were adjudicated by an investigator blinded to the PWA signal and considered associated with PWA drop if concomitant.

RESULTS

A significant increase in EEG power density in all EEG frequency bands was found during PWA drops (P<0.001) compared to before and after drop. Even in the absence of visually scored arousals, PWA drops were associated with a significant increase in EEG power density (P<0.001) in most frequency bands.

CONCLUSIONS

Drops in PWA are associated with a significant increase in EEG power density, suggesting that these events can be used as a surrogate for changes in cortical activity during sleep. This approach may prove of value in scoring respiratory events on limited-channel (type III) portable monitors.

Detection of respiratory events using pulse rate in children with and without obstructive sleep apnea

Oximetry is a simple but insensitive diagnostic test modality for obstructive sleep apnea (OSA) in children. Sensitivity for OSA may be enhanced if pulse rate is analyzed in conjunction with oxygen saturation. We analyzed 25 ambulatory polysomnographic recordings obtained from children with (n = 5) and without (n = 20) OSA. To assess sensitivity and specificity, pulse rate increases were determined during respiratory (i.e., apneas and hypopneas; n = 965) and non-respiratory sleep events (i.e., body movements; n = 1,197), and contrasted to baseline fluctuations (n = 209). The absolute pulse rate increase (APRI) was the parameter that differentiated best between baseline fluctuations and sleep events (area under the receiver operating characteristic curve [AUC]: 0.88). At a cutoff value of 12 beats per minute, APRI showed a sensitivity and specificity for detecting sleep events of 0.81 each. However, AUC was lower for the differentiation between respiratory and non-respiratory sleep events (0.77) and between central and obstructive respiratory events (0.68). In OSA cases, influencing factors for APRI following respiratory events were age, occurrence of a body movement, and severity of concomitant oxygen desaturation. We conclude that pulse rate analysis may be used to detect respiratory events in oximetry recordings in children.

Pulse rate and pulse rate variability decrease after adenotonsillectomy for obstructive sleep apnea

BACKGROUND

Data suggest that obstructive sleep apnea syndrome (OSA) results in sympathetic stimulation, brady/tachycardia and cardiac stress. Heart rate variability, but not baseline heart rate, is known to be elevated in pediatric OSA. Our patients with moderate to severe OSA (McGill Oximetry Scores of 3 or 4) have been re-evaluated with pulse oximetry after adenotonsillectomy (T&A). We hypothesized that pulse rate (PR) and pulse rate variability (PRV) would decrease after treatment of OSA with T&A.

METHODS

This retrospective before-after study comprised pre- and post-operative oximetries and parental questionnaires of children 1-18 years old with moderate to severe OSA from September 2004 to August 2005, inclusive. We excluded patients with significant comorbidities.

RESULTS

In 25 subjects, age at surgery was 4.3 +/- 3.6 years (mean +/- SD). OSA symptoms decreased or resolved, saturation metrics improved, and parental concern about breathing during sleep decreased following T&A. PR decreased in 21 of 25 patients after T&A (mean PR from 99.7 +/- 11.2 to 90.1 +/- 10.7 bpm, P < 0.001; maximum PR from 150.6 +/- 14.5 to 137.4 +/- 15.6 bpm, P < 0.001). PRV, as measured by the standard deviation of the PR, decreased in 23 of 25 patients after T&A (from 10.3 +/- 2.1 to 8.2 +/- 1.6 bpm, [P < 0.001]). Pulse accelerations greater than 6, 7, 8 bpm also decreased post-operatively.

CONCLUSIONS

Nocturnal pulse oximetry complements clinical history to document improvement and/or resolution of moderate to severe OSA in children. Resolution of tachycardia and diminished PRV after T&A illustrate the stress that recurrent airway obstruction during sleep places on the cardiovascular system. Further work will be required to determine if PR and PRV as measured by pulse oximetry would be useful in the diagnosis and follow-up of OSA in children.

An ECG-based algorithm for the automatic identification of autonomic activations associated with cortical arousal

OBJECTIVES

EEG arousals are associated with autonomic activations. Visual EEG arousal scoring is time consuming and suffers from low interobserver agreement. We hypothesized that information on changes in heart rate alone suffice to predict the occurrence of cortical arousal.

METHODS

Two visual AASM EEG arousal scorings of 56 healthy subject nights (mean age 37.0 +/- 12.8 years, 26 male) were obtained. For each of 5 heartbeats following the onset of 3581 consensus EEG arousals and of an equal number of control conditions, differences to a moving median were calculated and used to estimate likelihood ratios (LRs) for 10 categories of heartbeat differences. Comparable to 5 consecutive diagnostic tests, these LRs were used to calculate the probability of heart rate responses being associated with cortical arousals.

RESULTS

EEG and ECG arousal indexes agreed well across a wide range of decision thresholds, resulting in a receiver operating characteristic (ROC) with an area under the curve of 0.91. For the decision threshold chosen for the final analyses, a sensitivity of 68.1% and a specificity of 95.2% were obtained. ECG and EEG arousal indexes were poorly correlated (r = 0.19, P <0.001, ICC = 0.186), which could in part be attributed to 3 outliers. The Bland-Altman plot showed an unbiased estimation of EEG arousal indexes by ECG arousal indexes with a standard deviation of +/- 7.9 arousals per hour sleep. In about two-thirds of all cases, ECG arousal scoring was matched by at least one (22.2%) or by both (42.5%) of the visual scorings. Sensitivity of the algorithm increased with increasing duration of EEG arousals. The ECG algorithm was also successfully validated with 30 different nights of 10 subjects (mean age 35.3 [ 13.6 years, 5 male).

CONCLUSIONS

In its current version, the ECG algorithm cannot replace visual EEG arousal scoring. Sensitivity for detecting <10-s EEG arousals needs to be improved. However, in a nonclinical population, it may be valuable to supplement visual EEG arousal scoring by this automatic, objective, reproducible, cheap, and time-saving method.

Electroencephalogram characteristics of autonomic arousals during sleep in healthy men

OBJECTIVE

Many sleep disorders involve frequent, brief arousals, not appreciated during conventional sleep stage scoring due to lack of electroencephalogram (EEG) desynchronization. We evaluated the temporal relation between heart rate (HR) changes, an index of autonomic activation, and EEG in seven healthy subjects during sleep.

METHODS

We identified bouts of tachycardia-bradycardia and performed spectral analysis of EEG during these. We also identified cortical arousals by the appearance of EEG alpha activity. This allowed us to dichotomize bouts of tachycardia-bradycardia by presence or absence of cortical arousal.

RESULTS

During non-rapid eye movement (REM) sleep, bouts with or without cortical arousal occurred with approximately equal frequency. Those with cortical arousals usually preceded onset of EEG changes. Those without cortical arousals were followed by increases in delta but not alpha power. EEG did not change during bouts in REM sleep.

CONCLUSIONS

Capturing bouts of tachycardia-bradycardia is relatively easy via computerized algorithm. Bouts occur with cortical arousal or with slow wave synchronization suggestive of subcortical arousal. Thus, changes in HR may be useful index of arousal.

SIGNIFICANCE

These brief bursts of tachycardia-bradycardia are consistent with autonomic arousal. Such a measure may be among the first in a continuum of arousal ending with frank awakening.

The pulse transit time arousal index in obstructive sleep apnea before and after CPAP

BACKGROUND AND PURPOSE

Pulse transit time (PTT) is a non-invasive index which reflects changes in peripheral vascular resistance and intrathoracic pressure. PTT arousal index (PTT Ar/I) is defined as the frequency (number/hour) of a defined decrease in PTT which may serve as a marker for respiratory events, and associated arousals which occur in patients with obstructive sleep apnea (OSA). This study was designed to evaluate the PTT Ar/I before and after patients with OSA were treated with continuous positive airway pressure (CPAP).

PATIENTS AND METHODS

Individuals referred for evaluation of possible OSA underwent split-night polysomnography (PSG). The findings from 144 consecutive patients with a respiratory disturbance index (RDI)>/=20, who demonstrated at least a 50% drop in RDI with CPAP, provide the basis for this analysis. The PTT Ar/I measured before and after CPAP were compared to other measures of severity for OSA, including RDI and arousal index.

RESULTS

The PTT Ar/I correlates with the RDI (r=0.43, P</=0.0001) and with the arousal index (r=0.43, P<0.0001). Moreover, the decrease in RDI and arousal index that occurs with CPAP treatment correlates with a similar decrease in the PTT Ar/I (r=0.54, P<0.0001).

CONCLUSIONS

The PTT Ar/I correlates well with other standard measures of severity in patients with OSA and is potentially a non-invasive marker with which to measure the frequency of disruptive events that occur during sleep.

Pulse transit time improves detection of sleep respiratory events and microarousals in children

OBJECTIVES

To evaluate the additional information provided by pulse transit time (PTT), a noninvasive tool, when using during polysomnography for the diagnosis of sleep breathing disorders in a pediatric population.

MAIN FINDINGS

Respiratory and microarousals events were scored twice. The first scoring was performed using nasal pressure, thermistors, thoracic and abdominal movements, and oxygen saturation. The second scoring, blinded to the first scoring, was performed using PTT in combination with all the other signals. Microarousals were scored once visually on the EEG trace (cortical arousals [CAs]) and once using the PTT signal (autonomic arousals [AAs]) blinded to EEG. For the whole group of 16 children studied (mean age, 9.5 years), there was no significant difference between the respiratory disturbance index (RDI) with or without PTT analysis (22.4 +/- 13.5/h vs 20.4 +/- 14.3/h; not significant [mean +/- SD]). Among the children exhibiting a "without PTT" RDI < 30/h, 5 of 12 children (41.66%) showed a clinically significant >/= 5/h increase in RDI when using PTT. AAs detected by PTT were significantly more frequent than CAs during rapid eye movement (REM) sleep (7.4 +/- 3.9/h vs 3.2 +/- 2.3/h; p < 0.001) and slow wave sleep (SWS) [6.0 +/- 4.3/h vs 0.6 +/- 0.5/h; p < 0.0001].

CONCLUSIONS

The quantification of respiratory effort using PTT improves the detection of respiratory events in children. The detection of microarousals is improved particularly in REM and SWS.

Heart rate increment: an electrocardiological approach for the early detection of obstructive sleep apnoea/hypopnoea syndrome

The prevalence of OSAHS (obstructive sleep apnoea/hypopnoea syndrome) is high in developed countries and it is estimated that the vast majority of patients remain undiagnosed. On the basis of physiological evidence, we evaluated the frequency component of HRI (heart rate increment) as a simple and inexpensive screening tool for OSAHS detection in a first group of patients (group 1) and validated their discriminant capacity in a second group (group 2). The predictive accuracy of hourly %VLFI (frequency-domain HRI variable obtained from nocturnal ECG Holter monitoring) was analysed by comparison with an hour-by-hour respiratory disturbances index assessed by complete polysomnography in 28 consecutive clinically suspected OSAHS patients for group 1 and in 35 patients for group 2. OSAHS was present in 20 patients according to a mean hourly apnoea plus hypopnoea index >10 in group 1, and prevalence reached 77.1% in group 2. Sensitivity, specificity and positive and negative predictive accuracy were calculated and an ROC (receiver operating characteristic) curve was constructed for several polysomnographic threshold values. In group 1, hourly %VLFI appeared as an evident predictor of the apnoea/hypopnoea index (W=0.848, P<0.0001; where W is the area under the curve obtained using ROC curve analysis). Using an appropriate threshold (value ≥3.2%), %VLFI demonstrated a sensitivity of 78.1% and a specificity of 70.4%. These thresholds applied to group 2 yielded a sensitivity of 73.9% and a specificity of 76.6%. Frequency-domain analysis of the HRI appears to be a powerful tool for OSAHS prediction. The simplicity of its analysis and use makes of it a particularly well-suited variable for routine mass screening in high-risk populations undergoing ECG Holter monitoring.