Martina Mason

Usefulness of the STOP-Bang Questionnaire in a Cardiac Surgical Population

OBJECTIVE The aim of this study was to assess the predictive accuracy of the STOP-Bang questionnaire in relation to obstructive sleep apnea (OSA) detected by nocturnal oximetry, as well as postoperative outcomes, in a population undergoing cardiac surgery. DESIGN A prospective observational cohort study. SETTING The specialist cardiothoracic center at the Royal Papworth Hospital, Cambridge University Health Partners, United Kingdom. PARTICIPANTS All adult patients, undergoing elective coronary artery bypass grafting with or without cardiac valve surgery between March 2013 and July 2014 were included. The authors excluded patients participating in other interventional studies, those who had a tracheostomy before surgery, and those who required emergency surgery or were due to be admitted on the day of surgery. INTERVENTIONS None. MEASUREMENTS AND RESULTS Cardiac surgical patients were screened for the risk of OSA with the use of STOP-Bang questionnaire. The presence of OSA prior to surgery was assessed with overnight oximetry. The predictive performance of the STOP-Bang questionnaire was assessed by calculating sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve (AUC)-receiver operating characteristic curve (ROC). Multiple-logistic regression models were used to assess for associations between the STOP-Bang scores and postoperative outcomes. The STOP-Bang questionnaire discriminated poorly between mild OSA (AUC-ROC 0.57 [95% confidence interval (CI) 0.47-0.67]) and moderate/severe OSA (AUC-ROC 0.82 (95% CI 0.69-0.95)]. Accuracy was increased by modifying the cut-off value to 6 or greater, with sensitivity and specificity of 75% and 77%, respectively. A STOP-Bang score indicating the possibility of OSA was not significantly associated with prolonged intensive care unit lengths of stay (hazard ratio [HR] 1.1; 95% CI 0.99-1.19; p = 0.08) or postoperative complications (odds ratio [OR] 1.0; 95% CI 0.59-1.72; p = 0.98). CONCLUSIONS In the study population, a STOP-Bang questionnaire score of 3 or greater had limited predictive value for identifying cardiac surgical patients at high risk of OSA. STOP-Bang scores were not significantly associated with worse postoperative outcomes. A STOP-Bang score of 6 or greater could help identify patients in need of a sleep study to confirm the presence of OSA as such patients may be at increased risk of postoperative complications.

P215 Continuous positive airway pressure (cpap) versus auto-cpap (apap) for the initial treatment of obstructive sleep apnoea syndrome: clinical efficacy and cost

Introduction and Objectives APAP has been shown to be an effective way of titrating CPAP levels. Systematic reviews have shown similar treatment effects for APAP and CPAP. APAP devices are increasingly used for outpatient initiation of CPAP and subsequent long term use. In this service evaluation we assessed the clinical effectiveness and cost implications of APAP pressure titration followed by switching to long term CPAP. Methods We collected data on 93, newly diagnosed patients with OSAS, starting on PAP, at baseline and at a 3 months follow-up visit. Patients initiated on APAP in an outpatient setting were asked to return in 2 weeks’ time to swap APAP for CPAP, set at average pressure estimated by APAP. The compliance, Epworth Sleepiness Scale (ESS) score and physiological indices; mean nocturnal SpO2, 4% oxygen desaturation index (ODI), from nocturnal oximetry were collected at 3 months. Cost of device CPAP vs. long term APAP were compared. We also compared outcomes between patients with mild and moderate/severe OSA (ODI≥15). Results Following 3 months of treatment patients had clinically and statistically significant improvements in measured parameters aside from change in weight (Table 1). There was no significant difference in CPAP compliance between patients with mild and moderate/severe OSA, 5.6 (3.2–6.9) vs. 5.3 (3.7–7.0) hours/night respectively, p=0.9. We found 74% of patients with mild OSA and 75% of patients with moderate/severe OSA used CPAP for ≥4 hours. Patients with mild OSA were sleepy with median ESS 12 (10–15) and treatment with CPAP led to significant reduction to ESS 8 (4–11), at 3 months. No patients asked to be transferred back to APAP. Transferring patients to CPAP, after initial APAP pressure titration, led to a calculated cost saving of £1 98 144 p/a, estimating that 1536 new patients initiate CPAP each year. Conclusions - Auto CPAP titration pathway is effective in terms of the outcomes measured. - Good compliance with significant reduction in ESS has been shown in patients with mild OSA, confirming that appropriately selected mild OSA patients can benefit from CPAP. - Transferring patients from APAP to long term CPAP can lead to significant cost reduction. Abstract P215 Table 1 Data are presented as median and interquartile range (IQR). A p value of <0.05 was deemed statiscally significant.

S27 Predictive performance of STOPBANG questionnaire for diagnosis of sleep apnoea in a cardiac surgical cohort

Introduction and objectives Questionnaires to assess the risk of obstructive sleep apnoea (OSA) prior to surgery could reduce the need for screening sleep studies. STOPBANG questionnaire is user friendly and was previously validated in a general surgical population. A high risk of OSA has been defined as a score of ≥3 and low risk as a score 0–2. We aimed to validate the STOPBANG against nocturnal oximetry in a population undergoing major cardiac surgery and assessed its prognostic value for postoperative outcomes. Methods Patients were screened for high risk of OSA with the STOPBANG questionnaire. The presence of sleep apnoea (SA), prior to surgery, was assessed with overnight oximetry. SA was defined as mild with a 4% oxygen desaturation index (ODI) of 5–14/hr, moderate with ODI of 15–29/hr and severe ODI ≥30/hr. Predictive performance of STOPBANG against nocturnal oximetry was assessed for diagnosis of mild and moderate SA by assessing the area under curve receiver operating characteristic (AUC-ROC) and sensitivity and specificity were calculated. A multiple-logistic regression model was used to assess association of STOPBANG and post-operative outcomes. Results The AUC-ROC for mild SA was low 0.57 (95% CI = 0.47–0.67). Good performance was observed for moderate SA with AUC-ROC 0.82 (95% CI = 0.69–0.95) (Figure 1) but specificity of STOPBANG at the conventional cut of value of ≥3 for moderate SA was very low at 5% whilst sensitivity was 100%. The best predictive STOPBANG cut-off value for moderate SA was ≥6 with sensitivity and specificity of 75% and 77% respectively. Assessing predictive value for severe SA was not possible due to the lack of severe SA cases in our cohort. STOPBANG was not found to be an independent predictor of worse post-operative outcomes.Abstract S27 Figure 1 ROC curves for STOPBANG to predict ODI ≥5 and ODI ≥15 Conclusion Predictive performance of STOPBANG in our patient cohort at the conventional cut off value was poor. The probable explanation is that the cardiac surgical population is preselected as male, older and most suffer with hypertension. Thus the majority will score as high risk for OSA. STOPBANG had no prognostic value on worse postoperative outcomes in our study, which again contrasts with the findings in general surgical cohorts.

S28 Effect of sleep apnoea on post-operative outcomes in cardiac surgery

Introduction and objectives Obstructive sleep apnoea (OSA) is common and can be associated with adverse health outcomes. There are conflicting data for the impact of undiagnosed OSA on the outcome of surgical procedures but at least some results suggest an association with worse outcomes. EuroSCORE risk model was developed to calculate the risk of mortality after cardiac surgery. We evaluated the prevalence and impact of undiagnosed sleep apnoea (SA) on postoperative outcomes in cardiac surgery. Methods Patients undergoing coronary artery bypass grafting with or without cardiac valve surgery were screened for the presence of SA, prior to surgery, with the STOPBANG questionnaire and overnight oximetry. SA was defined as a 4% oxygen desaturation index (ODI) of ≥5/hr. A Weibull model was used to analyse lengths of stay (LoS) in intensive care unit (ICU). Complications in ICU were dichotomised and analysed with binary logistic regressions. Parsimonious models were obtained using a combination of step-wise regression and manually removing predictors that did not reach the 5% significance level. Results 122 subjects were included in final analysis of which 57 (47%) had a new diagnosis of SA. Of those, 45 (79%) had mild SA and 12 (21%) had moderate/severe SA. There was no simple relationship between OSA as measured by ODI and LoS in ICU. The most significant predictor for ICU LoS was developing complications at ICU (p < 0.001). The independent predictors associated with increasing likelihood of developing major organ complications following cardiac surgery were EuroSCORE, ODI and intravenous opioid analgesia (IOA). When patients with mild and moderate SA received IOA, predicted probability of complications rose 2.4 and 1.4 times respectively (Figure 1).Abstract S28 Figure 1 Predicted probabilities and 95% CI of suffering a complication at ICU as ODI increases for individuals with average EuroSCORE (5) and with or without IOA Conclusion We found a high prevalence of undiagnosed sleep apnoea in our cohort. EuroSCORE, SA and the administration of intravenous morphine were found to be independent risk factors for developing post-operative complications. This risk has increased when patients with SA received intravenous morphine.