Investigation Of Obstructive Sleep Apnoea Research Articles

O028 Combination Pharmacological Therapy Targeting Multiple Mechanisms of Sleep Apnea

Abstract Introduction Currently two leading experimental pharmacological interventions are under investigation for obstructive sleep apnea (OSA). Acetazolamide, which acts to stabilise ventilatory control, lowers the apnea-hypopnea index (AHI) by ∼38%. More recently, atomoxetine-plus-oxybutynin (“AtoOxy”), acting via improvements to dilator muscle responsiveness and baseline tone, was found to lower AHI by >50%. Given that each potential therapy targets a different pathophysiology, we tested whether combined AtoOxy-plus-acetazolamide would be more efficacious than AtoOxy alone. Methods In a multicenter randomised crossover trial, 19 patients with moderate-to-severe OSA received AtoOxy (80/5mg respectively), acetazolamide (500mg), AtoOxy-plus-acetazolamide, or placebo at bedtime for 3 nights (half-dose on first night); outcomes were assessed at baseline and night 3 of each treatment period. Primary outcome: mixed model analysis compared the reduction in AHI(3% desaturation or arousal criterion) from baseline between AtoOxy-plus-acetazolamide and AtoOxy. Secondary outcomes included hypoxic burden, arousal index, and visual analog scale for sleep quality. Results Compared with placebo, AHI was lowered with AtoOxy by +49 [33, 62] %baseline (estimate [95%CI]), AtoOxy-plus-acetazolamide by +47 [31, 61]%baseline, and acetazolamide by +34 [14, 50]%baseline. However, there was no effect of AtoOxy-plus-acetazolamide vs. AtoOxy alone (−3 [−33, 20]%baseline, P=0.8). Secondary outcomes: AtoOxy, acetazolamide and combined AtoOxy-plus-acetazolamide each lowered hypoxic burden and arousal index, but no differential effect of combination therapy was observed. There was no impact on the visual analog scale for sleep quality. Conclusions While AtoOxy halved AHI, and acetazolamide lowered AHI by a third, the combination of these leading experimental interventions provided no greater efficacy than AtoOxy alone.

Circulating C-reactive protein levels in patients with suspected obstructive sleep apnea.

To assess determinants of C-reactive protein (CRP) in a cohort of patients referred for investigation of obstructive sleep apnea (OSA) and to determine whether the overlap of OSA and chronic obstructive pulmonary disease (overlap syndrome) is associated with higher levels of CRP. This was a cross-sectional study that included 2,352 patients seen at the West Australian Sleep Disorders Research Institute between 2006 and 2010. All patients had circulating CRP levels measured and spirometry performed. OSA was defined as an apnea-hypopnea index ≥ 5 events/h, and chronic obstructive pulmonary disease was defined as a forced expiratory volume in 1 second/forced vital capacity ratio < 0.70 and age > 40 years. Univariate and multivariate regression analysis were used to identify CRP determinants. The mean age was 51 years (60% male), the median apnea-hypopnea index was 27 events/h, the median 3% oxygen desaturation index was 24 events/h, the mean forced expiratory volume in 1 second was 88% predicted, and the median CRP was 3.0 mg/L. In multivariate analyses, age, body mass index, female sex, neck circumference, apnea-hypopnea index, and desaturation markers (nadir and mean oxygen saturation) were independently associated with higher CRP. Spirometric variables were not predictors. There was no significant difference in CRP among patients with OSA with or without coexisting chronic obstructive pulmonary disease. Markers of OSA severity (apnea-hypopnea index and oxygenation), age, body mass index, neck circumference, and female sex were independent predictors of circulating CRP levels. OSA overlapping with chronic obstructive pulmonary disease was not associated with increased CRP compared to either condition alone, suggesting other mechanisms for the increased cardiovascular disease risk in overlap syndrome. Recognizing factors that predict CRP will help identify patients at higher risk of cardiovascular disease and aid risk stratification. Shah A, Mukherjee S, McArdle N, Singh B, Ayas N. Circulating C-reactive protein levels in patients with suspected obstructive sleep apnea. J Clin Sleep Med. 2022;18(4):993-1001.

Impact of upper airway configuration on CPAP titration assessed by CT during Müller's maneuver in OSA patients

PurposeContinuous positive airway pressure (CPAP) is the current gold-standard treatment for moderate to severe obstructive sleep apnea (OSA), and upper airway anatomy plays an increasingly important role in evaluating the efficacy of CPAP therapy. The aim of this observational study was to investigate the influence of upper airway anatomy on CPAP titration in OSA patients assessed by computed tomography (CT) during Müller's maneuver. MethodsConsecutive patients under investigation for OSA by undergoing polysomnography and CT scan of the upper airway while awake were enrolled. Successful full-night manual titration was performed to determine the optimal CPAP pressure level for OSA patients in supine position using a nasal mask. ResultsA total of 157 subjects (134 males and 23 females) were included. Both apnea–hypopnea index (AHI) and LaSO2 significantly correlated with CPAP titration level, upper airway length (UAL), distance from mandibular plane to hyoid bone (MPH), and neck circumference (all p < 0.05). There were significant positive correlations between CPAP titration level and UAL (r = 0.348, p = 0.000) and MPH (r = 0.313, p = 0.002). Stepwise multiple linear regression analyses were performed to evaluate the independent predictors of AHI, LaSO2, and CPAP titration level. CPAP titration level was identified as an independent explanatory variable for AHI and LaSO2 after adjustment for confounders. Multiple linear regression analyses also indicated that body mass index (BMI) and UAL were independently associated with CPAP titration level (all p < 0.05). ConclusionsUpper airway abnormalities combined with anthropometric parameters play important roles in CPAP titration for OSA patients, providing additional insight into the factors influencing OSA treatment strategies. UAL and BMI should be taken into consideration when choosing CPAP titration level to improve CPAP compliance.

Diagnosis of Sleep-Disordered Breathing in the Home Environment.

Polysomnography, a gold standard for the diagnosis of sleep-disordered breathing, is a complex investigation requiring access to the sleep laboratory. Thus, sleep-disordered breathing could be underdiagnosed. The aim of this paper was to investigate the feasibility and effectiveness of self-performed investigation of obstructive sleep apnea (OSA) in the home setting, using a portable device, and to assess the comfort and simplicity of the procedure from the patient's perspective. The study included 68 middle-aged patients (21 women and 47 men), who were examined at home with the ApneaLink Air device in search for the underlying reason of reported nighttime snoring and occasionally disordered breathing pattern. The apnea-hypopnea index was quantified and matched with body mass index (BMI), age, and other characteristics. OSA was diagnosed in 37 patients (27 men and 10 women): 22 had mild, 4 had moderate, and 11 patients had severe OSA. All cases of severe OSA were present in men. Patients with severe OSA had significantly higher BMI than those from the other groups. All of the patients pointed to the comfort and ease of the diagnostic device. We conclude that home diagnosis of OSA is a relatively easy and cost-effective way to substitute for the hospital-linked polysomnography, particularly in severely ill patients who have a movement difficulty. A wider implementation of home-based diagnosis of OSA may substantially increase the number of patients investigated in a short time span, also leading to the plausibly upward correction of the disease prevalence.

The McGill score as a screening test for obstructive sleep disordered breathing in children with co-morbidities

BackgroundThe McGill score is used to stratify severity of oximetry in children referred for investigation of obstructive sleep apnoea (OSA) to identify those with more severe disease and prioritize treatment. We hypothesized that its positive predictive value (PPV) and negative predictive value (NPV) in detecting OSA differs significantly between children with medical conditions and otherwise healthy children. MethodsWe performed a two-year retrospective analysis of children referred for investigation of OSA who underwent a cardiorespiratory (CR) polygraphy study. McGill score was calculated from the oximetry trace blinded to polygraphy results. We looked at two definitions of OSA: Obstructive Apnoea Hypopnoea Index (oAHI) ≥1 and ≥ 5. McGill sensitivity, specificity, PPV and NPV were calculated. McGill score = 1 was considered normal or inconclusive, >1 abnormal. ResultsWe studied 312 children, 190 males (61%), median age 4.5 (2.4–7.9) years. 129 were otherwise healthy and 183 had associated medical conditions. The PPV of the McGill score was significantly lower in children with medical conditions than otherwise healthy children. The NPV was similar in both groups of children. ConclusionsThe higher number of false positives in children with medical conditions may be due to non-obstructive causes such as central apnoeas. Children with underlying lung disease are also more likely to desaturate following a brief apnoea or hypopnoea. Children with co-morbidities who have an abnormal McGill score should not be assumed to have OSA and need more detailed sleep studies to determine the reason for the oxygen desaturations.

Floppy eyelid syndrome: ocular and systemic associations.

To summarize the ocular and systemic associations of floppy eyelid syndrome (FES) as well as provide an up-to-date review on the pathogenesis and treatment strategies. Virtually all patients with FES have obstructive sleep apnea (OSA). However, a significantly lower proportion of patients with OSA have FES. Although some studies demonstrate no association between OSA and FES, almost all show at least an association with increased eyelid laxity, which may be a less severe form of FES. FES has also been associated with keratoconus (KCN) and glaucoma. Decreased corneal hysteresis has been found in FES, KCN, glaucoma, and OSA and may be related to matrix metalloproteinase (MMP) upregulation. Hypoxia-reperfusion injury, leptin resistance, and mechanical forces all may lead to increased MMP activity, contributing to elastin breakdown in the tarsus and other tissues throughout the body. Management of FES begins with investigation for OSA. Treating OSA with continuous positive airway pressure (CPAP) or surgical uvulopalatoplasty may improve FES. Surgical treatments for FES should reduce horizontal eyelid laxity while maximizing the stability of the tarsus. Collagen crosslinking may prove a helpful modality for stabilizing the tarsus in the future. FES is associated with OSA, glaucoma, and KCN. MMP upregulation and lower corneal hysteresis have been found in these conditions, pointing toward a potential common pathogenesis.

Investigation of Obstructive Sleep Apnea in Adult Non-Cyctic Fibrosis Bronchiectasis Patients

Investigation of Obstructive Sleep Apnea in Adult Non-Cyctic Fibrosis Bronchiectasis Patients

A review of approaches for analysing obstructive sleep apnoea-related patterns in pulse oximetry data.

Overnight pulse oximetry allows the relatively non-invasive estimation of peripheral blood haemoglobin oxygen saturations (SpO2 ), and forms part of the typical polysomnogram (PSG) for investigation of obstructive sleep apnoea (OSA). While the raw SpO2 signal can provide detailed information about OSA-related pathophysiology, this information is typically summarized with simple statistics such as the oxygen desaturation index (ODI, number of desaturations per hour). As such, this study reviews the technical methods for quantifying OSA-related patterns in oximetry data. The technical methods described in literature can be broadly grouped into four categories: (i) Describing the detailed characteristics of desaturations events; (ii) Time series statistics; (iii) Analysis of power spectral distribution (i.e. frequency domain analysis); and (d) Non-linear analysis. These are described and illustrated with examples of oximetry traces. The utilization of these techniques is then described in two applications. First, the application of detailed oximetry analysis allows the accurate automated classification of PSG-defined OSA. Second, quantifications which better characterize the severity of desaturation events are better predictors of OSA-related epidemiological outcomes than standard clinical metrics. Finally, methodological considerations and further applications and opportunities are considered.

Investigation of Obstructive Sleep Apnea Using Portable Monitors and Health Check Data in Japanese Drivers.

Aims: The identification and appropriate management of commercial motor vehicle (CMV) drivers with unrecognized obstructive sleep apnea (OSA) is a major public health concern and priority; OSA among drivers has not been fully investigated in Japan, and a better understanding of this undiagnosed disease is warranted. Therefore, we evaluated the prevalence of OSA and the factors related to apnea–hypopnea index (AHI) in Japanese CMV drivers.Methods: This retrospective study included 1309 Japanese CMV drivers aged 40–69 years. All the subjects received type IV portable sleep monitors (PMs) with Epworth Sleepiness Scale (ESS) and a periodic health check including anthropometrical and laboratory measurements, and a questionnaire of medical history, smoking status, and life style, following which variables related to AHI were analyzed.Results: Of all the subjects, 23.9% had moderate to severe OSA (AHI ≥ 15). Age, body mass index (BMI), LogeHbA1c and diastolic blood pressure (DBP) showed significance with AHI in 1309 subjects. The following factors were found to have significant odds ratio (OR) for AHI of ≥ 15 in 1309 subjects: age, ESS, DBP, and LogeHbA1c.Conclusion: Notably, drivers with undiagnosed OSA exist. In these subjects, AHI was related to obesity, hypertension, and diabetes. For the early diagnosis and intervention of OSA, BMI, blood pressure, and HbA1c measurements may be helpful, particularly for drivers. Furthermore, when performing an objective assessment of the suspected OSA, evaluating these parameters during routine medical check-ups may be useful and feasible in the detection of drivers with latent OSA.

Influence of interface and position on upper airway collapsibility assessed by negative expiratory pressure.

Negative expiratory pressure (NEP) is a simple technique for the evaluation of upper airway collapsibility in patients with obstructive sleep apnea (OSA). Most studies evaluated NEP using a mouthpiece that may exclude the cephalic portion of the upper airway. We hypothesize that NEP determination is influenced by interface and position. We evaluated patients with suspected OSA using polysomnography, NEP (-5cmH2O in sitting and supine position with mouthpiece and nasal mask). A subgroup also underwent computed tomography (CT) of the upper airway. We studied a total of 86 subjects (72 male, age 46±12yrs, body mass index 30.0±4.4kg/m2, neck circumference 40.0±3.5cm, AHI 32.9±26.4, range 0.5 to 122.5events/hour). NEP was influenced by interface and position (p=0.007), and upper airway was more collapsible with mouthpiece than with nasal mask in sitting position (p=0.001). Position influenced NEP and was worse in supine only when evaluated by nasal mask. Expiratory resistance (R 0.2) at 0.2s during NEP was significantly higher and independent of position with mouthpiece than with nasal mask (20.7 versus 8.6cmH2O/Ls-1, respectively, p=0.018). NEP evaluated with nasal mask in supine position and with mouthpiece in sitting position, but not when evaluated with mouthpiece in supine position, were correlated with upper airway anatomical measurements including tongue dimensions and pharyngeal length. Interface and position influence NEP. NEP evaluated with nasal mask in supine position may convey more relevant information for patients under investigation for OSA than when evaluated with mouthpiece.

Erratum to: Toward numerical simulations of fluid–structure interactions for investigation of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a medical condition characterized by repetitive partial or complete occlusion of the airway during sleep. The soft tissues in the airway of OSA patients are prone to collapse under the low-pressure loads incurred during breathing. This paper describes efforts toward the development of a numerical tool for simulation of air–tissue interactions in the upper airway of patients with sleep apnea. A procedure by which patient-specific airway geometries are segmented and processed from dental cone-beam CT scans into signed distance fields is presented. A sharp-interface embedded boundary method based on the signed distance field is used on Cartesian grids for resolving the airflow in the airway geometries. For simulation of structure mechanics with large expected displacements, a cut-cell finite element method with nonlinear Green strains is used. The fluid and structure solvers are strongly coupled with a partitioned iterative algorithm. Preliminary results are shown for flow simulation inside the three-dimensional rigid upper airway of patients with obstructive sleep apnea. Two validation cases for the fluid–structure coupling problem are also presented.

当科における小児睡眠時無呼吸症についての検討

当科における小児睡眠時無呼吸症についての検討

Toward numerical simulations of fluid–structure interactions for investigation of obstructive sleep apnea

Toward numerical simulations of fluid–structure interactions for investigation of obstructive sleep apnea

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

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. Children having home overnight oximetry for suspected OSA were identified over 12months, 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. One hundred sixteen children had normal oximetry, of whom 93 (median age 4.5years; 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. The PRI-15 shows promise as an indicator of OSA in children with normal oximetry.

P260 Haematological characteristics of patients referred for investigation of Obstructive Sleep Apnoea

IntroductionObstructive Sleep Apnoea (OSA) is a condition with increasing prevalence. Individuals with severe OSA have significant intermittent nocturnal hypoxia. Erythropoiesis is stimulated through the renal secretion of erythropoietin in response...

Investigation of Obstructive Sleep Apnea Using Nonlinear Mode Interactions in Nonstationary Snore Signals

Acoustic studies on snoring sounds have recently drawn attention as a potential alternative to polysomnography in the diagnosis of obstructive sleep apnea (OSA). This paper investigates the feasibility of using nonlinear coupling between frequency modes in snore signals via wavelet bicoherence (WBC) analysis for screening of OSA. Two novel markers (PF1 and PSF), which are frequency modes with high nonlinear coupling strength in their respective WBC spectrum, are proposed to differentiate between apneic and benign snores in same- or both-gender snorers. Snoring sounds were recorded from 40 subjects (30 apneic and 10 benign) by a hanging microphone, and subsequently preprocessed within a wavelet transform domain. Forty inspiratory snores (30 as training and 10 as test data) from each subject were examined. Results demonstrate that nonlinear mode interactions in apneic snores are less self-coupled and usually occupy higher and wider frequency ranges than that of benign snores. PF1 and PSF are indicative of apneic and benign snores (p < 0.0001), with optimal thresholds of PF1 = 285 Hz and PSF = 492 Hz (for both genders combined), as well as sensitivity and specificity values between 85.0 and 90.7%, respectively, outperforming the conventional diagnostic indicator (spectral peak frequency, PF = 243-275 Hz, sensitivity = 77.7-79.7%, specificity = 72.0-78.0%, p < 0.0001). Relationships between apnea-hypopnea index and the proposed markers could likely take the functional form of exponential or power. Perspectives on nonlinear dynamics analysis of snore signals are promising for further research and development of a reliable and inexpensive diagnostic tool for OSA.

Large Eddy Simulation and Reynolds-Averaged Navier–Stokes modeling of flow in a realistic pharyngeal airway model: An investigation of obstructive sleep apnea

Computational fluid dynamics techniques employing primarily steady Reynolds-Averaged Navier–Stokes (RANS) methodology have been recently used to characterize the transitional/turbulent flow field in human airways. The use of RANS implies that flow phenomena are averaged over time, the flow dynamics not being captured. Further, RANS uses two-equation turbulence models that are not adequate for predicting anisotropic flows, flows with high streamline curvature, or flows where separation occurs. A more accurate approach for such flow situations that occur in the human airway is Large Eddy Simulation (LES). The paper considers flow modeling in a pharyngeal airway model reconstructed from cross-sectional magnetic resonance scans of a patient with obstructive sleep apnea. The airway model is characterized by a maximum narrowing at the site of retropalatal pharynx. Two flow-modeling strategies are employed: steady RANS and the LES approach. In the RANS modeling framework both k–ε and k–ω turbulence models are used. The paper discusses the differences between the airflow characteristics obtained from the RANS and LES calculations. The largest discrepancies were found in the axial velocity distributions downstream of the minimum cross-sectional area. This region is characterized by flow separation and large radial velocity gradients across the developed shear layers. The largest difference in static pressure distributions on the airway walls was found between the LES and the k–ε data at the site of maximum narrowing in the retropalatal pharynx.

Functional central nervous system imaging in the investigation of obstructive sleep apnea

This review summarizes recent neuroimaging research into cerebral alterations observed in obstructive sleep apnea. Studies applying neuroimaging techniques over the past 10 years have made important contributions to our understanding of the neurocognitive changes associated with this disorder. Converging experiments using different methods (transcranial Doppler, event-related potentials, magnetic resonance spectroscopy, and structural and functional magnetic resonance imaging) demonstrated changes in cerebral blood flow, metabolism, morphology, and brain activation in response to cognitive challenges in patients with obstructive sleep apnea. Obstructive sleep apnea is associated with unique cerebral alterations that may explain the changes in behavior and cognition observed. Their high temporal and spatial resolution mean that functional magnetic resonance imaging techniques may provide important information regarding the cerebral changes associated with cognitive performance in obstructive sleep apnea. Studies should control for obstructive sleep apnea-associated changes in basal cerebral blood flow, however. In addition, further research using standardized morphologic techniques is needed to better localize and characterize the pattern of neuronal loss in obstructive sleep apnea. Likewise, techniques to examine cerebral white matter integrity will be important in fully elucidating the impact of obstructive sleep apnea on the brain, as well as any recovery in brain function and cognitive performance following treatment.

Is heart rate variability the simple solution to diagnose sleep apnoea?

Early in the investigation of obstructive sleep apnoea it was recognised that the events of apnoea and hypopnoea are accompanied by concomitant cyclic variations in heart rate 1. The pattern of brady/tachycardia is closely linked to the time course of apnoeic events. As a consequence, this pattern had been used successfully to detect sleep apnoea in patients with clinical symptoms for sleep apnoea. Dedicated devices were developed over the past 15 yrs to detect sleep apnoea at an early stage of the disease using recordings of heart rate, snoring, oxygen saturation and body position 2. These devices were used successfully to stratify the individual risk of patients suffering from sleep-disordered breathing before they were referred to cardiorespiratory polysomnography. Sleep laboratories have limited capacity for cardiorespiratory polysomnography and are expensive in terms of personal costs due to continuous attendance during the night. The sensitivity and specifity of these simplified four channel-based recording systems had been evaluated in many studies giving results for specific systems. A recent systematic review compiled the results of these studies in a comparative overview 3. The review revealed the value and the limitations of systems with respect to the accepted criteria for the diagnosis of sleep apnoea 4. In conclusion, a satisfactory standardisation of terms and of diagnostic criteria regarding the portable diagnosis of sleep apnoea could not be achieved. In parallel with efforts to define evidence-based criteria for the simplified diagnosis of …

Which derivative from overnight oximetry best predicts symptomatic response to nasal continuous positive airway pressure in patients with obstructive sleep apnoea?

The cost and inconvenience of polysomnography for the investigation of obstructive sleep apnoea (OSA) has led to the search for simpler and cheaper alternatives. These are usually compared to an apnoea/hypopnoea index (AHI) derived from oro-nasal airflow and ribcage/abdominal effort sensors. However, AHI is not a proven gold standard for the identification of clinically important OSA. Recent work has shown that correctly analysed oximetry indices not only mimic AHI with considerable accuracy, but also predict the symptomatic response to nasal continuous positive airway pressure (nCPAP) at least as well as conventional polysomnographic indices. This current study looks at 10 different derivatives of all-night oximeter tracings in 81 patients with OSA, and compares their ability to predict the improvement in subjective sleepiness after 6 months of nCPAP therapy.Sleep apnoea in this study was defined as a >4% Sa O2dip rate of >10 h−1, and an Epworth sleepiness score (ESS) of >10 on presentation. Subjects took part in a placebo-controlled trial of nCPAP for 1 month and thereafter were all supplied with nCPAP set at an effective pressure. All night SaO2 was sampled every 2 sec and later analysed for mean, median, mean nadir of Sa O2dip, time below 90%, 2 and 12 sec delta index (an average measure of Sa O2change across these two time periods), rapid resaturation index (rises in Sa O2>3% within 10 sec per hour), and >4, >3, and >2% dips per hour. These indices were then correlated with the change in ESS seen after 6 months on nCPAPMedian compliance for the group was 5·8 (5/95% range, 1·5–8·0) h night−1. The two best correlates of improvement in ESS were the >4% Sa O2dips h−1(Spearman'sr =−0·33 P=0·002) and the delta 12 sec index (r=−0·33, P=0·003). Cumulative time below 90% SaO2 was almost as good (r=−0·29, P=0·009). The worst correlate was the >2% Sa O2dips h−1(r=0·01, not significant).This study has identified which of several analyses of overnight oximeter recordings best identify nCPAP responsive OSA. Both >4% Sa O2dips and 12 sec delta index are equally predictive and presumably the most appropriate derivatives to calculate from overnight records of Sa O2.