Cd Turnbull

Cardiovascular event rates in the MOSAIC trial: 2-year follow-up data

Abstract The Multicentre Obstructive Sleep Apnoea Intervention Cardiovascular (MOSAIC) trial investigated the effect of continuous positive airway pressure (CPAP) on both sleepiness and predicted cardiovascular risk over 6 months in minimally symptomatic patients with obstructive sleep apnoea. Although there was clear benefit in terms of Epworth Sleepiness Score, there was no improvement in blood pressure and predicted vascular risk score. In order to calculate the required size of future trials, with real vascular events as the endpoint, the rate of such events in this population is needed. 188 patients from the original trial were followed for 2 years. The overall number of new vascular events over the 2 years was 25, and all-cause mortality was 4. There was a weak statistically significant reduction in vascular events in the CPAP group (p=0.049). Large-scale randomised trials are needed to determine if CPAP causes a real reduction in vascular events in minimally symptomatic patients. Based on our figures, future trials of CPAP versus no treatment would need to randomise approximately 2540 patients to not miss a real reduction in vascular events and over 6000 for mortality.

P218 The effects of supplemental oxygen on blood pressure in obstructive sleep apnoea during cpap withdrawal

Introduction Intermittent hypoxia and/or intermittent arousals are thought to be the two key pathological mechanisms in the development of hypertension in obstructive sleep apnoea (OSA). We aimed to investigate the effect of abolishing the hypoxia on the rise in blood pressure (BP) that has been shown to follow continuous positive airway pressure (CPAP) withdrawal in patients with OSA. In addition, we explored the effect of supplemental oxygen on obstructive events during sleep. Methods Patients with OSA, established on CPAP≥1 year, and with ≥4 hours/ night usage, underwent a week of screening oximetry and were eligible if they had a nocturnal oxygen desaturation index ≥4% (ODI) of <10 on 3 nights on CPAP, and an ODI≥20 on at least 1 of 4 nights off CPAP. Patients then received overnight supplemental oxygen or air (via real or sham concentrators) at a flow rate of 5 l/min during 2 weeks off CPAP. After at least two weeks ‘washout’ back on CPAP, subjects crossed over. Treatment order was randomised. The primary outcome was early morning home BP which was recorded daily in triplicate, and averaged over the penultimate three mornings prior to each patient visit. Patients underwent overnight home respiratory sleep studies (including nasal airflow) on night 14 of each treatment arm. Differences between treatment arms were analysed using paired t-tests or Wilcoxon rank tests as appropriate. Results Twenty-five patients completed the study. Their mean ±standard deviation age was 63±7 years, mean BMI was 35.3±6.7 kg/m2, median (interquartile range) ODI at diagnosis was 48/hour (25, 68), and 21 (84%) were male. Table 1 shows the Results of the primary outcome and the overnight sleep studies. Abstract P218 Table 1 The results of early morning blood pressure and overnight sleep studies on supplemental oxygen and supplemental air. Paired t-tests were used for home early morning blood pressure and heart rate measurements. Wilcoxon rank tests were used for home respiratory sleep study derivatives which were not normally distributed Supplemental air Supplemental oxygen Home early morning blood pressure and heart rate measurements Baseline Follow-up Baseline Follow-up Mean difference in change in BP (95% confidence interval) p Mean systolic BP (mmHg) 129.2±14.1 136.1±14.9 129.6±15.1 129.8±13.6 −6.6 (-11.3 to −1.9) 0.008 Mean diastolic BP (mmHg) 78.3±7.8 85.3±9.6 79.3±8.0 81.6±8.0 −4.6 (-7.8 to −1.5) 0.006 Mean heart rate (bpm) 61.7±8.3 64.9±8.9 61.9±9.4 64.1±9.1 −1.0 (-3.9 to+1.9) 0.50 Home respiratory sleep study derivatives Supplemental air Supplemental oxygen Difference in medians p AHI (/hour) 34.4 (22.7–44.4) 30.4 (23.6–42.6) −3.6 0.98 ODI (/hour) 31.4 (21.0–49.2) 4.5 (1.1–19.0) −28.0 0.001 Mean oxygen saturations (%) 93.7 (92.1–95.2) 98.0 (96.6–98.6) +4.4 0.001 Sleep study length (mins) 392 (364–448) 394 (377–404) +4 0.80 Discussion Supplemental oxygen abolished the rise in early morning blood pressure during CPAP withdrawal when compared to supplemental air. As expected, supplemental oxygen substantially attenuated intermittent hypoxia and had only a small non-significant effect on the apnoea hypopnoea index. Thus intermittent hypoxia appears to be the dominant determinant of the rise in morning blood pressure seen in patients with OSA, rather than any other consequence of the obstructive events.

P71 Can postural OSA be identified from oximetry alone

Introduction Positional treatments have a long history of usage in obstructive sleep apnoea (OSA). Recent developments of more sophisticated therapies reported good response in patients with an AHI of <60 and predominately supine OSA (arbitrarily defined as total AHI: non-supine AHI ≥ 1.5).1,2 We hypothesised that patients with mild to moderate OSA usually have periods both with and without OSA, and that the OSA periods will be mainly due to supine OSA. Such patients might therefore be trialled on positional therapies without specific assessment of posture. Methods Patients included had OSA and underwent an in-hospital respiratory sleep study between May- July 2016. Sleep studies included video review for identification of supine sleep. The oxygen desaturation index >4% (ODI) was recorded in supine and non-supine positions. The ratio of the total to non-supine ODI was calculated. Results 40 patients’ sleep studies were suitable for analysis. 7 patients were excluded: 3 due to comorbidities (hypoventilation/CSA), 3 due to lack of supine sleep ( <30 minutes) and one due to having minimal OSA. Patients had a mean age of 53.8 years (SD 12.7) and mean BMI of 34.9 kg/m2 (SD 9.0). The median supine ODI was significantly higher than the median total ODI (supine ODI 54.3/h, IQR 47.9; total ODI 28.6/h, IQR 34.4; p < 0.001). There was a significant relationship between the ratio of total ODI to non-supine ODI versus the total ODI (Spearman’s rho = 0.37, p = 0.02; Figure 1). Discussion Our data suggests that patients with lower ODIs are more likely to have supine predominant OSA. At ODI values over 40 it is very unlikely that there is a posturally dependant component to a patient’s OSA. However, the reverse is not the case; although many patients with low ODIs do have a postural component, many do not. It is therefore necessary to objectively assess the degree of supine predominant OSA in future trials of positional therapies, but patients with ODIs over 40 could be excluded at the outset. Abstract P71 Figure 1 The relationship between the total ODI and the ration of total to non-supine ODI References Levendowski DJ, et al. Assessment of a neck-based treatment and monitoring device for positional obstructive sleep apnea. J Clin Sleep Med 2014;10(8):863–71. Levendowski DJ, et al. Capability of a neck worn device to measure sleep/wake, airway position, and differentiate benign snoring from obstructive sleep apnea. J Clin Monit Comput 2015;29:53–64.

S29 Predictors of continuous positive airways pressure usage at six months in minimally symptomatic patients. Further data from the MOSAIC trial

Introduction Severity of OSA and early patterns of CPAP usage have previously been shown to determine subsequent long term CPAP use in patients with symptomatic moderate-to-severe disease.1 We wished to see if different factors influenced compliance in minimally symptomatic patients. Methods Patients were randomised to 6-months of CPAP or standard care if they had an ODI of >7.5 h due to OSA on a baseline sleep study, but had insufficient daytime OSA symptoms to mandate CPAP.2 Baseline characteristics (Table 1), medical history, ESS, SAQLI and SF-36 were recorded. Repeat overnight pulse oximetry was performed after entry for uniformity of trial ODI across recruiting centres.Abstract S29 Table 1 Baseline characteristics from all 195 patients randomised to CPAP with 6 month follow-up data Variable Mean (SD), Median (IQR) or Number (%) 100% Range Age (mean; SD) 57.9 (7.2) 45–75 Gender (number male;%) 153 (78.5%) - Ethnicity (number white;%) 188 (96.4%) - BMI (mean kg/m2; SD) 32.2 (5.6) 21.6–51.6 Smoking status (number;%)  Current 17 (8.7%) -  Ex-smoker 102 (52.3%) -  Never smoker 76 (39%) - Reported snoring (number yes;%) 190 (97.4%) - Reported apnoeas (number yes;%) 142 (72.8%) - Reported choking (number yes;%) 66 (33.8%) - Reported nocturia (number yes;%) 114 (58.5%) - Oxygen desaturation index (ODI, median; IQR) 10.2 (4.7, 17.5) 0.5–58.0 Epworth Sleepiness Score (ESS, mean; SD) 7.9 (4.4) –18 Short sleep apnoea quality of life index (SAQLI, mean; SD) 4.9 (1.1) 2.3–6.9 SF-36 Physical Summary (mean; SD) 42.0 (12.3) 9.4–61.3 SF- 36 Mental Summary (mean; SD) 48.1 (10.3) 19.9–63.7 CPAP usage data were downloaded at the 2–4 week assessment, and at the 6 month assessment. Those who withdrew were assumed to have 0:00 h/n usage. Correlations were calculated between CPAP usage at the 6 month assessment and both the baseline characteristics and to the 2–4 week CPAP usage data. Results Median CPAP usage at 2–4 week follow-up was low at 2:49 h/n (n = 174, IQR 0:44, 5:13). Median usage at 6 month follow-up was 2:17 h/n (n = 195, IQR 0:08, 4:54). At 6 months males had significantly greater mean usage at 2:56 h/n compared to 1:47 h/n in females (95% confidence intervals of the difference, -1:49 to -0:09 h/n, p = 0.02). There were no other significant predictors of 6 month usage (age, BMI, ODI, ESS, sleep symptoms, smoking status, ethnicity, SAQLI, SF-36). Average usage of CPAP at 2–4 week assessment was moderately correlated with the average usage at the 6 month assessment (r = 0.76, p < 0.001). Conclusions Male gender predicted greater CPAP usage at 6 months, but no other baseline characteristics were predictive of CPAP usage in these minimally symptomatic patients with generally mild OSA. 2–4 week CPAP usage was predictive of 6 month usage, but by no means could all patients’ usage be predicted at such an early stage. Thus in clinical practice, trials of CPAP are necessary in patients with minimally symptomatic OSA but it may be necessary for patients to try CPAP for longer than one month to determine those benefitting from treatment in the long term. References 1 Thorax 2010;65:829–32 2 Thorax 2012;67:1090-66

P108 Quality of life, diet and exercise measurements in obese individuals with and without ventilatory failure

Introduction Obesity is associated with reduced quality of life (QOL), particularly physical health. In addition obesity has been linked to reduced exercise and high calorie diet. We aimed to describe these factors in obese individuals with and without ventilatory failure, and investigate the hypothesis that ventilatory failure would have a negative impact on QOL. Methods QOL, diet and exercise was assessed as part of an open cross-sectional study of ventilatory failure in obese subjects referred either for assessment of sleep disordered breathing or bariatric surgery. The SF-12 was completed; a validated questionnaire to assess QOL giving summary scores for physical health (PCS) and mental health (MCS), and compared to data from a large non-obese UK cohort.1 Participants underwent actigraphy (SenseWear BodyMedia) and from this the daily energy expenditure was estimated. A sedentary lifestyle was defined as <5000 steps/day. Participants completed a validated food frequency questionnaire, which calculates daily dietary calorie intake from patient reported three month food habits. This was compared to UK guideline recommended daily maximum intake. Arterial base excess was measured as a marker of ventilatory failure and the correlations between quality of life indices and arterial base excess were calculated. Results 72 individuals with a mean age of 52.0 years (SD 8.9) and median BMI of 46.7 kg/m2 (IQR 39.5, 52.6) participated in the study. Median duration of actigraphy was 23.2 days (IQR 21.2, 23.4). Arterial base excess was significantly but weakly correlated to MCS (r = 0.33, p = 0.01) but not to PCS (r = 0.05, p = 0.74).Abstract P108 Table 1 Results of SF-12, actigraphy, food frequency questionnaire and arterial blood gasses N Study mean or median SD or IQR 95% confidence interval of difference from comparison mean P value PCS 58 38.0 11.3 -16.4, -11.3 <0.0001 MCS 58 41.2 10.6 -10.2, -5.0 <0.0001 Energy expenditure (kCal) 58 2977 566 Daily steps 59 3169 2141, 5242 71.2% were ‘sedentary’ (<5000 steps/day) Dietary energy (kCal) Men 26 2434 1760, 3348 46.1% were above recommended daily allowance for men (>2500kCal/d) Dietary energy (kCal) Women 26 2812 2171, 3494 76.9% were above recommended daily allowance for women (>2000kCal/d) Arterial base excess (mmol/l) 72 2.08 2.41 48.6% had a raised arterial base excess (>2 mmol/l) Arterial PaCO2 (kPa) 72 5.57 0.80 22.2% had a raised PaCO2 (>6 kPa) Conclusions Obesity had a large negative impact on both physical and mental QOL not reproducibly reported elsewhere. Ventilatory failure was only a weak predictor of mental, but not physical QOL scores. The majority of participants were sedentary and dietary calorie intake was higher than the recommended daily allowance for most women and a significant number of men. Actigraphy energy expenditure estimates exceeded patient reported dietary intake, which is probably due to patient underreporting. This highlights the clinical importance of considering mental health, physical activity and diet together when obese individuals are seen in a tertiary centre. Reference 1 J Pub Health Med. 2001;23:187–94