Teanau Roebuck

Increased long-term mortality in heart failure due to sleep apnoea is not yet proven

Previous small-scale studies of the effect of sleep-disordered breathing (SDB) on prognosis in congestive heart failure (CHF) are either lacking or conflicting. The aim of this study was to assess the impact of the presence and type of SDB on mortality in a patient group with severe CHF referred to a specialised heart failure centre. Out of 78 patients ((mean±sd) 53±9 yrs, left ventricular ejection fraction 19.9±7.2% and pulmonary capillary wedge pressure 16.5±8.3 mmHg) followed-up over a median period of 52 months, 29% had no apnoea (CHF‐N), 28% had obstructive sleep apnoea (CHF‐OSA) and 42% had central sleep apnoea (CHF‐CSA). At 52 months, their overall mortality was 40%, and combined mortality and transplantation was 72%. Mortality rates were similar between the three apnoea groups. Survivors had a similar prevalence of SDB (71%) as the nonsurvivors (70%). Although a significant increase in mortality was evident at 500 days in those patients with either CHF‐SDB or CHF‐CSA as compared with CHF‐N, this was not significant at final follow-up (52 months) using Kaplan Meier analysis. Multivariate analysis identified transplantation but not SDB type or severity as a significant predictor of survival. In conclusion, sleep-disordered breathing impacts upon early (500 day), but not long-term (52 month), mortality in a specialised heart failure centre.

Loop Gain As a Means to Predict a Positive Airway Pressure Suppression of Cheyne-Stokes Respiration in Patients with Heart Failure

RATIONALE Patients with heart failure (HF) and Cheyne-Stokes respiration or periodic breathing (PB) often demonstrate improved cardiac function when treatment with continuous positive airway pressure (CPAP) resolves PB. Unfortunately, CPAP is successful in only 50% of patients, and no known factor predicts responders to treatment. Because PB manifests from a hypersensitive ventilatory feedback loop (elevated loop gain [LG]), we hypothesized that PB persists on CPAP when LG far exceeds the critical threshold for stable ventilation (LG = 1). OBJECTIVES To derive, validate, and test the clinical utility of a mathematically precise method that quantifies LG from the cyclic pattern of PB, where LG = 2π/(2πDR - sin2πDR) and DR (i.e., duty ratio) = (ventilatory duration)/(cycle duration) of PB. METHODS After validation in a mathematical model of HF, we tested whether our estimate of LG changes with CPAP (n = 6) and inspired oxygen (n = 5) as predicted by theory in an animal model of PB. As a first test in patients with HF (n = 14), we examined whether LG predicts the first-night CPAP suppression of PB. MEASUREMENTS AND MAIN RESULTS In lambs, as predicted by theory, LG fell as lung volume increased with CPAP (slope = 0.9 ± 0.1; R(2) = 0.82; P < 0.001) and as inspired-arterial PO(2) difference declined (slope = 1.05 ± 0.12; R(2) = 0.75; P < 0.001). In patients with HF, LG was markedly greater in 8 CPAP nonresponders versus 6 responders (1.29 ± 0.04 versus 1.10 ± 0.01; P < 0.001); LG predicted CPAP suppression of PB in 13/14 patients. CONCLUSIONS Our novel LG estimate enables quantification of the severity of ventilatory instability underlying PB, making possible a priori selection of patients whose PB is immediately treatable with CPAP therapy.

Prevalence of depression in patients referred with snoring and obstructive sleep apnoea.

Depression and obstructive sleep apnoea are two common entities, with common symptoms that make identification of either condition difficult. Our aim was to examine, within a group of patients referred with snoring and obstructive sleep apnoea, (i) the prevalence of depression with the 14‐question Hospital Anxiety and Depression Scale (HADS), (ii) the correlation between the two lead depression symptoms from the Mini‐International Neuropsychiatric Interview (MINI) and HADS, and (iii) the relationship between depression symptoms with physiological markers of OSA.

Cardiac diastolic function and hypercapnic ventilatory responses in central sleep apnoea

Hyperventilation is the key factor contributing to the development of idiopathic nonhypercapnic central sleep apnoea (ICSA), where left ventricular systolic function is normal. ICSA is reported to occur in 20% of patients with left ventricular diastolic dysfunction, in whom elevated pulmonary vascular pressures and resultant increased pulmonary vagal afferent traffic may contribute to hyperventilation. The contribution of the two potential mechanisms responsible for the hyperventilation seen in the following ICSA was measured: 1) left ventricular diastolic dysfunction-induced pulmonary hypertension; and 2) increased peripheral and central hypercapnic ventilatory responses (HCVR). The pulmonary artery pressure, left ventricular diastolic function and chemosensitivity to hypercapnia were measured during wakefulness in 16 subjects with ICSA. All subjects had systolic pulmonary artery pressures <3.99 kPa (<30 mmHg) and only four had diastolic dysfunction. All subjects had elevated peripheral and central HCVR compared with historical normal control subjects. Diastolic dysfunction correlated with increasing age but not with HCVR or markers of central sleep apnoea severity. Idiopathic nonhypercapnic central sleep apnoea is likely to be dependent upon raised hypercapnic ventilatory responses, and not pulmonary hypertension due to left ventricular diastolic dysfunction.

Depression may reduce adherence during CPAP titration trial.

STUDY OBJECTIVES Depression is a risk factor for medication non-compliance. We aimed to identify if depression is associated with poorer adherence during home-based autotitrating continuous positive airway pressure (autoPAP) titration. DESIGN Mixed retrospective-observational study. SETTING Academic center. PARTICIPANTS Two-hundred forty continuous positive airway pressure-naïve obstructive sleep apnea (OSA) patients. MEASUREMENTS Patients underwent approximately 1 week of home-based autoPAP titration with adherence data downloaded from the device. Electronic hospital records were reviewed in a consecutive manner for inclusion. Three areas of potential predictors were examined: (i) demographics and clinical factors, (ii) disease severity, and (iii) device-related variables. Depression and anxiety were assessed using the Hospital Anxiety and Depression Scale (HADS). Scores on the subscales were categorized as normal or clinical diagnoses of depression (≥ 8) and anxiety (≥ 11). The primary outcome variable was the mean hours of autoPAP used per night. RESULTS Patients were diagnosed with OSA by either attended polysomnography (n = 73, AHI 25.5[15.1-41.5]) or unattended home oximetry (n = 167, ODI3 34.0[22.4-57.4]) and had home-based autoPAP titration over 6.2 ± 1.2 nights. Mean autoPAP use was 4.5 ± 2.4 hours per night. Multiple linear regression analysis revealed that depression and lower 95(th) percentile pressures significantly predicted lesser hours of autoPAP use (R(2) = 0.19, p < 0.001). Significantly milder OSA in those requiring lower pressures may have confounded the relationship between 95(th) percentile pressure and autoPAP use. CONCLUSION Depression was independently associated with poorer adherence during home-based autoPAP titration. Depression may be a potential target for clinicians and future research aimed at enhancing adherence to autoPAP therapy.

Comparison of supine-only and REM-only obstructive sleep apnoea

OBJECTIVES The effect of body position and sleep state on sleep apnoea have major clinical implications in the management of patients, yet are infrequently reported in the scientific literature. The aim of this study was to compare and contrast the prevalence and severity of supine-only and rapid eye movement (REM)-only obstructive sleep apnoea (OSA) in a population. METHODS Prospective cohort analysis of the influence of supine body position and REM sleep on the severity of apnoea in 100 consecutive patients with OSA (apnoea-hypopnoea index [AHI]>5) using attended polysomnography with continuous digital monitoring in an accredited sleep laboratory. Supine-only OSA was defined as a supine:non-supine AHI ratio of >2:1 and non-supine AHI <5 events/h. REM-only OSA was defined as an REM:non-REM ratio of >2:1 and non-REM AHI <5events/h. RESULTS Supine sleep time represented a greater proportion of total sleep time than REM sleep time (40% vs 13%). The prevalence of supine-only OSA was more than twofold greater than that of REM-only OSA (23% and 10%, respectively). The supine-only group had greater overall AHI (mean 12.6±6.1 vs 7.2±2.2 events/h; P<0.01) than the REM-only group. No significant differences in gender, age, or sleepiness were found between the two groups. CONCLUSIONS Supine-only OSA is more common and is associated with a greater AHI than REM-only OSA.

Control theory prediction of resolved Cheyne-Stokes respiration in heart failure.

Cheyne–Stokes respiration (CSR) foretells deleterious outcomes in patients with heart failure. Currently, the size of therapeutic intervention is not guided by the patients underlying pathophysiology. In theory, the intervention needed to resolve CSR, as a control system instability (loop gain >1), can be predicted knowing the baseline loop gain and how much it falls with therapy. In 12 patients with heart failure, we administered an inspiratory carbon dioxide fraction of 1–3% during CSR (n=95 interventions) as a means to reduce loop gain. We estimated the loop gain on therapy (LGtherapy), using the baseline loop gain (using hyperpnoea length/cycle length) and its expected reduction (18% per 1% inspired carbon dioxide), and tested the specific hypothesis that LGtherapy predicts CSR persistence (LGtherapy >1) versus resolution (LGtherapy <1). As predicted, when LGtherapy >1.0, CSR continued during therapy in 23 out of 25 (92%) trials. A borderline loop gain zone (0.8<LGtherapy<1) yielded an unpredictable outcome, while LGtherapy <0.8 consistently yielded CSR resolution (37 out of 37 trials). A threshold of LGtherapy=0.9 determined outcome in 76 out of 95 (80%) trials. We establish proof-of-concept that control theory provides predictive insight into CSR resolution in heart failure. Thus, we now have a means to calculate the size of interventions needed to ameliorate CSR on a patient-by-patient basis. Control theory predicts the magnitude of therapeutic intervention needed to resolve Cheyne-Stokes respiration http://ow.ly/Vpuj301PRUq

A consensus opinion amongst stakeholders as to benefits of obstructive sleep apnoea treatment for cardiovascular health: OSA treatment for cardiovascular health

Obstructive sleep apnoea (OSA) is a prevalent sleep disorder associated with increased cardiovascular morbidity and mortality. Whether treatment of OSA improves cardiovascular risk remains controversial. Our aim was to determine a consensus opinion of key sleep medicine stakeholder groups as to the cardiovascular benefits of treating moderate–severe OSA.