Reducing aerosol dispersion by high flow therapy in COVID-19: High resolution computational fluid dynamics simulations of particle behavior during high velocity nasal insufflation with a simple surgical mask.

Objective: All respiratory care represents some risk of becoming an aerosol-generating procedure (AGP) during COVID-19 patient management. Personal protective equipment (PPE) and environmental control/engineering is advised. High velocity nasal insufflation (HVNI) and high flow nasal cannula (HFNC) deliver high flow oxygen (HFO) therapy, established as a competent means of supporting oxygenation for acute respiratory distress patients, including that precipitated by COVID-19. Although unlikely to present a disproportionate particle dispersal risk, AGP from HFO continues to be a concern. Previously, we published a preliminary model. Here, we present a subsequent highresolution simulation (higher complexity/reliability) to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during HVNI, low-flow oxygen therapy (LFO2), and tidal breathing. Methods: This in silico modeling study of HVNI, LFO2, and tidal breathing presents ANSYS fluent computational fluid dynamics simulations that evaluate the effect of Type I surgical mask use over patient face on particle/droplet behavior. Results: This in silico modeling simulation study of HVNI (40 L min-1) with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in LFO2 (6 L min-1) capture, with particle distribution escaping to the room (> 1 m from face) lower for HVNI+Mask versus LFO2+Mask (8.23% vs 17.2%). The overwhelming proportion of particulate escape was associated with mask-fit designed model gaps. Particle dispersion was associated with lower velocity. Conclusions: These simulations suggest employing a surgical mask over the HVNI interface may be useful in reduction of particulate mass distribution associated with AGPs.

The ventilatory effect of high velocity nasal insufflation compared to non-invasive positive-pressure ventilation in the treatment of hypercapneic respiratory failure: A subgroup analysis.

PURPOSE: Oxygen delivery by high flow nasal cannula (HFNC) is effective in providing respiratory support. HFNC has utility in clearing the extra-thoracic dead space, making it potentially beneficial in the treatment of hypercapnic respiratory failure. This study compares high velocity nasal insufflation (HVNI), a form of HFNC, to non-invasive positive pressure ventilation (NIPPV) in their abilities to provide ventilatory support for patients with hypercapnic respiratory failure. METHODS: This is a pre-defined subgroup analysis from a larger randomized clinical trial of Emergency Department (ED) patients with respiratory failure requiring NIPPV support. Patients were randomized to HVNI or NIPPV. Subgroup selection was done for patients with discharge diagnoses of acute hypercapnic respiratory failure or acute exacerbation of chronic obstructive pulmonary disease. The primary outcomes were change in pCO2 and pH over time. Secondary outcomes were treatment failure and intubation rate. RESULTS: 65 patients with hypercapnic respiratory failure were compared. 34 were randomized to HVNI and 31 to NIPPV. The therapeutic impact on PCO2 and pH over time was similar in each group. The intubation rate was 5.9% in the HVNI group and 16.1% in the NIPPV group (p = 0.244). The rate of treatment failure was 23.5% in the HVNI group and 25.8% in the NIPPV group (p = 1.0). CONCLUSION: HVNI may provide ventilatory support similar to NIPPV in patients presenting with acute hypercapnic respiratory failure, but further study is needed to corroborate these findings.

HVNI vs NIPPV in the treatment of acute decompensated heart failure: Subgroup analysis of a multi-center trial in the ED.

BACKGROUND AND OBJECTIVE: Managing respiratory failure (RF) secondary to acute decompensated heart failure (ADHF) with non-invasive positive-pressure ventilation (NIPPV) has been shown to significantly improve morbidity and mortality in patients presenting to the emergency department (ED). This subgroup analysis compares high-velocity nasal insufflation (HVNI), a form of high-flow nasal cannula, with NIPPV in the treatment of RF secondary to ADHF with respect to therapy failure, as indicated by the requirement for intubation or all-cause arm failure including subjective crossover to the alternate therapy. METHODS: The subgroup analysis is from a larger randomized control trial of adults presenting to the ED with RF requiring NIPPV support. Patients were randomly selected to therapy, and subgroup selection was established a priori in the original study as a discharge diagnosis. The primary outcome was therapy failure at 72 h after enrolment. RESULTS: Subgroup analysis included a total of 22 HVNI and 20 NIPPV patients which fit discharge diagnosis ADHF. Baseline patient characteristics were not statistically significant. Primary outcomes were not statistically significant: intubation rate (p = 1.000), therapy success (p = 1.000). Repeated measures (vitals, dyspnea, blood gases) showed comparable differences over initial 4 h. Physicians scored HVNI superior on patient comfort/tolerance (p < 0.001), ease of use (p = 0.004), and monitoring (p = 0.036). Limitations were technical inability to blind the clinician team and lack of power of the subgroup analysis. CONCLUSION: In conclusion, this subgroup analysis suggests HVNI may be non-inferior to NIPPV in patients with respiratory failure secondary to ADHF that do not need emergent intubation.

Randomised cross-over study of automated oxygen control for preterm infants receiving nasal high flow.

OBJECTIVE: To evaluate a prototype automated controller (IntellO2) of the inspired fraction of oxygen (FiO2) in maintaining a target range of oxygen saturation (SpO2) in preterm babies receiving nasal high flow (HF) via the Vapotherm Precision Flow. DESIGN: Prospective two-centre order-randomised cross-over study. SETTING: Neonatal intensive care units. PATIENTS: Preterm infants receiving HF with FiO2 ≥25%. INTERVENTION: Automated versus manual control of FiO2 to maintain a target SpO2 range of 90%-95% (or 90%-100% if FiO2=21%). MAIN OUTCOME MEASURES: The primary outcome measure was per cent of time spent within target SpO2 range. Secondary outcomes included the overall proportion and durations of SpO2 within specified hyperoxic and hypoxic ranges and the number of in-range episodes per hour. RESULTS: Data were analysed from 30 preterm infants with median (IQR) gestation at birth of 26 (24-27) weeks, study age of 29 (18-53) days and study weight 1080 (959-1443) g. The target SpO2 range was achieved 80% of the time on automated (IntellO2) control (IQR 70%-87%) compared with 49% under manual control (IQR 40%-57%; p<0.0001). There were fewer episodes of SpO2 below 80% lasting at least 60 s under automated control (0 (IQR 0-1.25)) compared with manual control (5 (IQR 2.75-14)). There were no differences in the number of episodes per hour of SpO2 above 98% (4.5 (IQR 1.8-8.5) vs 5.5 (IQR 1.9-14); p=0.572) between the study arms. CONCLUSIONS: The IntellO2 automated oxygen controller maintained patients in the target SpO2 range significantly better than manual adjustments in preterm babies receiving HF. TRIAL REGISTRATION NUMBER: NCT02074774.

Impaired Neurobehavioural Performance in Untreated Obstructive Sleep Apnea Patients Using a Novel Standardised Test Battery.

OBJECTIVE/BACKGROUND: Although polysomnography (PSG) is the gold-standard measure for assessing disease severity in obstructive sleep apnea (OSA), it has limited value in identifying individuals experiencing significant neurobehavioural dysfunction. This study used a brief and novel computerised test battery to examine neurobehavioural function in adults with and without OSA. PATIENTS/METHODS: 204 patients with untreated OSA [age 49.3 (12.5) years; body mass index, [BMI] 33.6 (8.0) kg/m2; Epworth sleepiness scale 12 (4.9)/24; apnea hypopnea index 33.6 (25.8)/h] and 50 non-OSA participants [age 39.2 (14.0) years; BMI 25.8 (4.2) kg/m2, ESS 3.6 (2.3)/24]. All participants completed a computerised neurobehavioural battery during the daytime in the sleep clinic. The OSA group subsequently underwent an overnight PSG. The 30 min test battery assessed cognitive domains of visual spatial scanning and selective attention (Letter Cancellation Test), executive function (Stroop task) and working memory (2- and 3-Back tasks), and a validated sustained attention task (psychomotor vigilance task, PVT). Group differences in performance were compared. Associations between disease severity and performance were examined in the OSA group. RESULTS: After controlling for age, gender and education, OSA patients demonstrated impaired performance on the Stroop-Text, 2 and 3-Back tasks, and the PVT compared with the non-OSA group. OSA patients had worse performance on the LCT with fewer average hits albeit with better accuracy. Some OSA polysomnographic disease severity measures were weakly correlated with performance. CONCLUSIONS: This brief test battery may provide a sensitive, standardised method of assessing daytime dysfunction in OSA.

Metabolic and hormonal effects of 'catch-up' sleep in men with chronic, repetitive, lifestyle-driven sleep restriction.

OBJECTIVE: Acutely restricting sleep worsens insulin sensitivity in healthy individuals whose usual sleep is normal in duration and pattern. The effect of recovery or weekend 'catch-up' sleep on insulin sensitivity and metabolically active hormones in individuals with chronic sleep restriction who regularly 'catch-up' on sleep at weekends is as yet unstudied. DESIGN: 19 men (mean ± SEM age 28·6 ± 2·0 years, BMI 26·0 ± 0·8 kg/m(2) ) with at least 6 months' history (5·1 ± 0·9 years) of lifestyle-driven, restricted sleep during the working week (373 ± 6·6 min/night) with regular weekend 'catch-up' sleep (weekend sleep extension 37·4 ± 2·3%) completed an in-laboratory, randomized, crossover study comprising two of three conditions, stratified by age. Conditions were 3 weekend nights of 10 hours, 6 hours or 10 hours time-in-bed with slow wave sleep (SWS) suppression using targeted acoustic stimuli. MEASUREMENTS: Insulin sensitivity was measured in the morning following the 3rd intervention night by minimal modelling of 19 samples collected during a 2-h oral glucose tolerance test. Glucose, insulin, c-peptide, leptin, peptide YY (PYY), ghrelin, cortisol, testosterone and luteinizing hormone (LH) were measured from daily fasting blood samples; HOMA-IR, HOMA-ß and QUICKI were calculated. RESULTS: Insulin sensitivity was higher following three nights of sleep extension compared to sustained sleep restriction. Fasting insulin, c-peptide, HOMA-IR, HOMA-ß, leptin and PYY decreased with 'catch-up' sleep, QUICKI and testosterone increased, while morning cortisol and LH did not change. Targeted acoustic stimuli reduced SWS by 23%, but did not alter insulin sensitivity. CONCLUSIONS: Three nights of 'catch-up' sleep improved insulin sensitivity in men with chronic, repetitive sleep restriction. Methods to improve metabolic health by optimizing sleep are plausible.

An automated algorithm to identify and reject artefacts for quantitative EEG analysis during sleep in patients with sleep-disordered breathing.

PURPOSE: Large quantities of neurophysiological electroencephalogram (EEG) data are routinely collected in the sleep laboratory. These are underutilised due to the burden of managing artefact contamination. The aim of this study was to develop a new tool for automated artefact rejection that facilitates subsequent quantitative analysis of sleep EEG data collected during routine overnight polysomnography (PSG) in subjects with and without sleep-disordered breathing (SDB). METHODS: We evaluated the accuracy of an automated algorithm to detect sleep EEG artefacts against artefacts manually scored by three experienced technologists (reference standard) in 40 PSGs. Spectral power was computed using artefact-free EEG data derived from (1) the reference standard, (2) the algorithm and (3) raw EEG without any prior artefact rejection. RESULTS: The algorithm showed a high level of accuracy of 94.3, 94.7 and 95.8% for detecting artefacts during the entire PSG, NREM sleep and REM sleep, respectively. There was good to moderate sensitivity and excellent specificity of the algorithm detection capabilities during sleep. The EEG spectral power for the reference standard and algorithm was significantly lower than that of the raw, unprocessed EEG signal. CONCLUSIONS: These preliminary findings support an automated way to process EEG artefacts during sleep, providing the opportunity to investigate EEG-based markers of neurobehavioural impairment in sleep disorders in future studies.

Assessing sleep disturbance in low back pain: the validity of portable instruments.

Although portable instruments have been used in the assessment of sleep disturbance for patients with low back pain (LBP), the accuracy of the instruments in detecting sleep/wake episodes for this population is unknown. This study investigated the criterion validity of two portable instruments (Armband and Actiwatch) for assessing sleep disturbance in patients with LBP. 50 patients with LBP performed simultaneous overnight sleep recordings in a university sleep laboratory. All 50 participants were assessed by Polysomnography (PSG) and the Armband and a subgroup of 33 participants wore an Actiwatch. Criterion validity was determined by calculating epoch-by-epoch agreement, sensitivity, specificity and prevalence and bias- adjusted kappa (PABAK) for sleep versus wake between each instrument and PSG. The relationship between PSG and the two instruments was assessed using intraclass correlation coefficients (ICC 2, 1). The study participants showed symptoms of sub-threshold insomnia (mean ISI = 13.2, 95% CI = 6.36) and poor sleep quality (mean PSQI = 9.20, 95% CI = 4.27). Observed agreement with PSG was 85% and 88% for the Armband and Actiwatch. Sensitivity was 0.90 for both instruments and specificity was 0.54 and 0.67 and PABAK of 0.69 and 0.77 for the Armband and Actiwatch respectively. The ICC (95%CI) was 0.76 (0.61 to 0.86) and 0.80 (0.46 to 0.92) for total sleep time, 0.52 (0.29 to 0.70) and 0.55 (0.14 to 0.77) for sleep efficiency, 0.64 (0.45 to 0.78) and 0.52 (0.23 to 0.73) for wake after sleep onset and 0.13 (-0.15 to 0.39) and 0.33 (-0.05 to 0.63) for sleep onset latency, for the Armband and Actiwatch, respectively. The findings showed that both instruments have varied criterion validity across the sleep parameters from excellent validity for measures of total sleep time, good validity for measures of sleep efficiency and wake after onset to poor validity for sleep onset latency.

Safety and Long Term Outcomes with High Flow Nasal Cannula Therapy in Neonatology: A Large Retrospective Cohort Study.

OBJECTIVE: High flow nasal cannula therapy (HFT) has been shown to be similar to nasal continuous positive airway pressure (nCPAP) in neonates with respect to avoiding intubation. The objective of the current study is to determine if there are trends for adverse safety and long-term respiratory outcomes in very low birth weight infants (<1500 g) from centers using HFT as their primary mode of non-invasive respiratory support compared to data from the largest neonatal outcomes database (Vermont Oxford Network; VON). METHODS: A multicenter, retrospective analysis of pulmonary outcomes data was performed for the calendar years 2009, 2010 and 2011. Performance of five HFT centers was compared with population outcomes from the VON database. The five HFT centers routinely use flow rates between 4-8 L/min as described by the mechanistic literature. Weighted average percentages from the five HFT centers were calculated, along with the 95% confidence intervals (CI) to allow for comparison to the VON means. RESULTS: Patient characteristics between the HFT centers and the VON were not different in any meaningful way, despite the HFT having a greater percentage of smaller infants. The average VON center primarily used nCPAP (69% of all infants) whereas the HFT centers primarily used HFT (73%). A lesser percentage of VLBW infants in the HFT cohort experienced mortality and nosocomial infection. Compared to VON data, an appreciably lesser percent of the HFT cohort were receiving oxygen at 36 weeks and less went home on oxygen. CONCLUSIONS: Considering there was no trend for adverse events, and there was a trend for better outcomes pertaining to long-term oxygen use, these data support claims of safety for HFT as a routine respiratory management strategy in the NICU.

The effect of continuous positive airway pressure usage on sleepiness in obstructive sleep apnoea: real effects or expectation of benefit?

RATIONALE: Placebo responses are complex psychobiological phenomena and often involve patient expectation of benefit. With continuous positive airway pressure (CPAP) treatment of obstructive sleep apnoea, greater hours of CPAP use are associated with reduced sleepiness. However, these open-label studies have not controlled for patient expectation of benefit derived from their knowledge of hours of device use. OBJECTIVES: To investigate the relative effectiveness of the use of real or placebo CPAP on daytime sleepiness. METHODS: Patient-level meta-analysis combining data on sleepiness measured by the Epworth Sleepiness Scale from three randomised placebo-controlled crossover trials. Mixed model analysis of variance was used to quantify the effects of real versus placebo device treatment, usage, their interaction and regression to the mean. MEASUREMENTS AND MAIN RESULTS: Duration of real and placebo CPAP use was correlated within patients (r=0.53, p<0.001). High use of real CPAP reduced sleepiness more than high use of placebo (difference 3.0 points; 95% CI 1.7 to 4.3, p<0.001) and more than low use of real CPAP (difference 3.3; 95% CI 1.9 to 4.7, p<0.0001). High use of placebo was superior to low use of placebo (difference 1.5; 95% CI 0.1 to 2.8, p=0.03). Twenty-nine per cent of the effect of high usage of CPAP (4.2 points; 95% CI 3.3 to 5.1) was explained by the expectation of benefit effect associated with high use of placebo (1.2 points ; 95% CI 0.2 to 2.3). CONCLUSIONS: A clinically significant proportion of the effectiveness of high CPAP use in reducing sleepiness is probably caused by patient expectation of benefit.

Residual sleep-disordered breathing during autotitrating continuous positive airway pressure therapy.

Obstructive sleep apnoea (OSA) is often treated with autotitrating continuous positive airway pressure (autoCPAP) devices. Clinical and bench tests of these devices have suggested performance limitations. These studies do not indicate whether this is a failure to detect or a failure to respond to airway obstruction. In this randomised, crossover trial, 34 patients with moderate-to-severe OSA underwent polysomnography on two laboratory visits. The autoCPAP device was randomly set to a fixed subtherapeutic pressure (detection assessment) or autotitrating mode (response assessment). Airflow was measured both from the autoCPAP (autoCPAP flow) and directly from the nasal mask, and recorded on polysomnography. Apnoea/hypopnoea indices (AHIs) measured at the two sites and from the autoCPAP download report were compared. Regarding detection, the AHI measured from the nasal mask showed good agreement with the autoCPAP flow AHI, but agreement was lower with the autoCPAP report AHI. In autotitrating mode, there was significant misclassification of those with and without OSA (AHI ≥ 10 events · h(-1)) on the autoCPAP report. Regarding response, residual OSA (AHI ≥ 10 events · h(-1)) was still evident in 24% of patients during autotitration. In some patients, autoCPAP fails to detect and/or respond to sleep apnoea. Clinicians should consider limitations of each device and use caution when using autoCPAP report statistics to verify effective treatment.

Effect of weight loss on upper airway size and facial fat in men with obstructive sleep apnoea.

BACKGROUND: Obstructive sleep apnoea (OSA) is commonly associated with obesity and can be improved by weight loss. Changes in upper airway size related to regional fat loss may mediate the improvement in OSA. This study aimed to assess changes in upper airway size and regional facial and abdominal fat with weight loss and their association with OSA improvement. METHODS: Middle-aged obese men with moderate-to-severe OSA underwent a 24-week sibutramine-assisted weight loss trial. Polysomnography and CT of the head and neck were performed at baseline and 24 weeks. The upper airway lumen and facial and parapharyngeal fat were measured with image analysis software. RESULTS: Post-intervention there was a significant reduction in weight (-7.8±4.2 kg, p<0.001) and apnoea-hypopnoea index (AHI) (-15.9±20.5 events/h, p<0.001). Velopharyngeal airway volume significantly increased from baseline (5.3±0.4 to 6.3±0.3 cm(3), p<0.01) and facial and paraphayngeal fat volume significantly reduced. A reduction in upper airway length was associated with improvement in AHI (r=0.385, p=0.005). The variance in AHI improvement was best explained by changes in upper airway length and visceral abdominal fat (R(2)=0.31, p=0.004). CONCLUSIONS: Weight loss increases velopharyngeal airway volume, but changes in upper airway length appear to have a greater influence on the reduction in apnoea frequency. Inter-individual variability in the effects of weight loss on OSA severity cannot be explained in terms of changes in upper airway structure and local fat deposition alone.

A randomized crossover trial of the effect of a novel method of pressure control (SensAwake) in automatic continuous positive airway pressure therapy to treat sleep disordered breathing.

OBJECTIVES: To study the acute effect of the new SensAwake CPAP modality (reducing pressure on awakenings) on wake after sleep onset (WASO) and other polysomnographic measures in patients with obstructive sleep apnea (OSA). STUDY DESIGN: Randomized crossover trial comparing an automatic continuous positive airway pressure device (AutoCPAP) with and without SensAwake on sleep architecture. CPAP naive patients received each therapy for a single night in the laboratory with at least 1-week washout. Both patients' and technicians' subjective satisfaction was assessed. Pressure data measured and stored by the AutoCPAP device were also analyzed. RESULTS: OSA was controlled adequately by both modes (SensAwake ON apnea hypopnea index ± SD, AHI = 5.3 ± 5.6/h vs. SensAwake OFF = 5.4 ± 5.8, p = 0.9) in the 42 patients who completed the protocol. Mean and 90% pressures were significantly lower with SensAwake (mean ON = 6.9 ± 1.9 vs. OFF = 7.7 ± 2.5 cm H(2)O, p < 0.05; 90% pressure ON = 9.6 ± 2.7 vs. OFF = 10.6 ± 2.7 cm H(2)O, p < 0.02). SensAwake did not improve WASO (ON = 74 ± 54 min vs. OFF = 78 ± 51 min, p = 0.6). There were no differences in other sleep architecture measures or patient satisfaction between the 2 modalities. AutoCPAP-measured AHI closely approximated PSG-derived (ROC AUC = 0.81 [95% CI 0.71-0.92], p = 0.0001). CONCLUSIONS: SensAwake provides similar control of the AHI to the standard AutoCPAP mode but does so at lower mean and 90% pressures. However, no measure of sleep architecture was significantly improved by the SensAwake mode during this initial acute exposure. The internal AutoCPAP AHI detection and calculation was similar to PSG-derived AHI measures. Longer term studies are needed to evaluate any long-term influence of SensAwake on WASO.

Altered positional regulation of nasal patency in patients with obstructive sleep apnoea syndrome.

We assessed the regulation of nasal patency supine in subjects with obstructive sleep apnoea syndrome (OSAS) compared to healthy controls. Healthy subjects increase nasal obstruction when changing body position from sitting to supine, possibly due to increased hydrostatic pressure in the head supine. Limited data indicate that this response is altered in patients with OSAS, suggesting that supine nasal patency is actively regulated. This study examined the nasal response to recumbent body position using acoustic rhinometry in OSAS patients and healthy controls. Twenty subjects (16 men and 4 women, mean age 55 +/- 16 years), with diagnosed OSAS [mean apnoea hypopnoea index (AHI) 46 +/- 22 events/h] without nasal obstruction and continuous positive airway pressure (CPAP)-naive, underwent measurement of intra-nasal cross sectional area by acoustic rhinometry at sitting and after 5 min supine. Twenty healthy controls (13 men, 7 women, mean age 35 +/- 9 years) were also included in the study. In the patients with OSAS, the mean minimal cross sectional area (MCA, left + right nasal cavity) was unchanged between sitting (1.18 +/- 0.41 cm(2)) and supine (1.21 +/- 0.35 cm(2), P = 0.5). In the healthy controls, the mean MCA decreased from 1.06 +/- 0.18 to 0.94 +/- 0.21 cm(2) supine, P = 0.01. This study showed that the normal decrease in nasal patency following a change in body position from sitting to supine is absent in patients with OSAS. The results indicate that there is an active regulation of supine nasal patency.

The validity of wrist actimetry assessment of sleep with and without sleep apnea.

INTRODUCTION: It is unclear whether actimetry can be reliably used to measure sleep in severe obstructive sleep apnea (OSA) patients. We compared polysomnography (PSG) with actimetric assessment of sleep on an epoch-by-epoch basis in subjects with and without OSA. METHODS: 21 subjects were recorded with simultaneous overnight standard PSG and actimetry. RESULTS: 10 subjects with apnea-hypopnea index (AHI) <10 (6.5 +/- 2.8/h) were classified as non-OSA subjects and 11 subjects with AHI >10 (42.0 +/- 27.3/h) were classified as OSA subjects. Overall sensitivity and specificity for actimetry to identify sleep was 94.6% and 40.6%, respectively, with an overall mean sleep/wake simple agreement of 84.6% and kappa of 0.38. There was no difference in agreement between non-OSA and OSA subjects (simple agreement: 83% vs. 86%, p = 0.73; kappa: 0.35 vs. 0.40, p = 0.73). The kappa agreement did not correlate with PSG arousal index (r = -0.21, p = 0.36) but declined with reduced sleep efficiency (r = 0.66, p = 0.001). There was no systematic difference (all p > 0.40) between actimetry and PSG in sleep latency, total sleep time and sleep efficiency, although correlations between the measurements using the two techniques were generally poor. However, while actimetry systematically underestimated wake after sleep onset (WASO) (35.5 +/- 18.8 vs. 59.4 +/- 35.1, p = 0.009), fragmentation index measured by actimetry only underestimated arousal index measured by PSG in OSA patients (23.9 +/- 17.8 vs. 33.1 +/- 18.5, p = 0.04). CONCLUSIONS: Contrary to prior reports, epoch-by-epoch comparison of sleep/wake scoring showed similar fair agreement between actimetry and PSG in subjects with or without OSA. Fragmentation index by actimetry may underestimate arousals caused by respiratory events and offer misleading results in severe OSA patients.

Diagnostic test evaluation of a nasal flow monitor for obstructive sleep apnea detection in sleep apnea research.

In this diagnostic test evaluation of a nasal flow monitoring device for obstructive sleep apnea (OSA), 34 patients referred for polysomnography were studied at home for three consecutive nights with the monitor. The mean age of subjects (+/-SD) was 41.9+/-10.3 years, and their mean apnea-hypopnea index (AHI) was 31.5+/-27.2. The difference between the average AHI from three nights at home on the monitor and the polysomnogram (PSG) result was 1.8+/-17.1. The area under the receiver operating characteristic curve (AUC) for PSG AHI > or = 10 was .96. With a threshold AHI of 18 on the flow monitor, sensitivity was .92, specificity .86, positive predictive value .96, and negative predictive value .75. For detecting severe OSA (AHI > or = 30), the AUC was .85. With knowledge of appropriate thresholds and the pretest risk of OSA, the flow monitor can be used to detect or exclude OSA for sleep-related research, as well as to identify severe cases needing priority for further evaluation.

First experience of using new adaptive servo-ventilation device for Cheyne-Stokes respiration with central sleep apnea among Japanese patients with congestive heart failure: report of 4 clinical cases.

BACKGROUND: Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in congestive heart failure (CHF) is generally considered a poor prognostic indicator, but treatment of CSR-CSA using an adaptive servo-ventilation (ASV) device has been developed. This is the first evaluation of its use in the management of CSR-CSA in Japanese CHF patients. METHODS AND RESULTS: Four CHF patients with CSR-CSA that was unresponsive to conventional positive airway pressure (CPAP) underwent 3 nights of polysomnography: baseline, CPAP or bi-level PAP, and on the ASV. The apnea - hypopnea index (AHI) and central-AHI (CAHI) were markedly improved on ASV (AHI 62.7+/-10.1 to 5.9+/-2.2 /h, p=0.0006, CAHI 54.5+/-6.7 to 5.6+/-2.3 /h, p=0.007). In addition, the sleep quality improved significantly on ASV, including arousal index (62.0+/-10.5 to 18.7 +/-6.2 /h, p=0.012), percentage of slow-wave sleep (2.6+/-2.6 to 19.4+/-4.8 %, p=0.042). CONCLUSIONS: ASV markedly improved CSR-CSA in patients with CHF. It is a promising treatment for Japanese patients with CHF.