The prevalence of restless legs syndrome across the full spectrum of kidney disease.

STUDY OBJECTIVES: Although restless legs syndrome (RLS) is common and well recognized as an important and potentially treatable cause of sleep disruption in end-stage renal disease (ESRD), few studies have evaluated the prevalence of RLS and its impact on sleep in the non-dialysis-dependent chronic kidney disease (CKD) population. The objectives of the study were to determine the prevalence of RLS across the full spectrum of kidney disease and to assess the impact of RLS on sleep quality and daytime function. METHODS: Five hundred patients were recruited from nephrology clinics and were stratified according to estimated glomerular filtration rate (EGFR): eGFR ≥ 60 mL/min/1.73m(2) (n = 127), CKD (eGFR < 60, not on dialysis, n = 242), and ESRD (on hemodialysis, n = 131). All subjects completed a sleep and medical history questionnaire, an RLS questionnaire, the Pittsburgh Sleep Quality Index (PSQI), and the Epworth Sleepiness Scale (ESS). RESULTS: The prevalence of RLS did not differ among the three groups (18.9% [eGFR ≥ 60], 26% (CKD), and 26% (ESRD) p = 0.27). However, many symptoms of sleep disruption were more common in patients with RLS, and RLS was independently correlated with the PSQI score both in the full cohort (OR = 2.63, CI = 1.60-4.00, p < 0.001) and the CKD group (OR = 2.39, CI = 1.20-4.79, p = 0.014). CONCLUSIONS: RLS is common in non-dialysis-dependent CKD patients and is an important source of sleep disruption.

Diagnostic value of screening instruments for identifying obstructive sleep apnea in kidney failure.

BACKGROUND: Patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have a high prevalence of obstructive sleep apnea (OSA) that can have significant clinical implications. An accurate clinical screening tool for OSA that identifies patients for further diagnostic testing would assist in the identification of this comorbidity. The Berlin Questionnaire (BQ), Adjusted Neck Circumference (ANC), and STOP-BANG questionnaire are 3 such instruments that have been validated in patients with normal kidney function. OBJECTIVE: The objective of this study was to determine the validity of these screening instruments in patients with CKD and ESRD, using overnight cardiopulmonary monitoring to diagnose OSA. METHODS: One hundred seventy-two patients were recruited from nephrology clinics and hemodialysis units (CKD: n = 109; ESRD: n = 63). All patients completed the BQ, ANC, STOP-BANG, and overnight cardiopulmonary monitoring to diagnose OSA (respiratory disturbance index [RDI] ≥ 15). Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for the BQ, ANC, and STOP-BANG. RESULTS: Obstructive sleep apnea was present in 41 CKD patients (38%) and 32 ESRD patients (51%). All screening instruments had satisfactory sensitivity (56% to 94%) but poor specificity (29% to 77%) and low accuracy (51% to 69%) in both CKD and ESRD patients with RDI ≥ 15. Using an RDI ≥ 30 yielded similar results. CONCLUSIONS: Current screening questionnaires do not accurately identify patients at high risk for OSA or rule out the presence of OSA in patients with CKD and ESRD. Consequently, objective monitoring during sleep is required to reliably identify sleep apnea in these patient populations.

Clinical presentation of obstructive sleep apnea in patients with chronic kidney disease.

BACKGROUND: Obstructive sleep apnea (OSA) is an important and common comorbidity in patients with chronic kidney disease (CKD). However, few studies have addressed how OSA presents in this patient population and whether it is clinically apparent. OBJECTIVE: The objectives of this study were to determine if the prevalence and severity of sleep related symptoms distinguished CKD patients with OSA from those without apnea, and whether the clinical presentation of OSA in CKD patients differed from the general OSA population. METHODS: One hundred nineteen patients were recruited from outpatient nephrology clinics. All patients completed a sleep history questionnaire, the Epworth Sleepiness Scale (daytime sleepiness, ESS > 10), the Pittsburgh Sleep Quality Index (poor sleep quality, PSQI > 5), and underwent overnight cardiopulmonary monitoring for determination of sleep apnea (respiratory disturbance index ≥ 15). CKD patients with OSA (n = 46) were compared to (1) CKD patients without OSA (n = 73) and (2) OSA patients without CKD (n = 230) who were referred to the sleep centre. RESULTS: The prevalence of OSA symptoms and PSQI scores did not differ between CKD patients with OSA and CKD patients without apnea. Although the prevalence of daytime sleepiness was higher in CKD patients with OSA compared to CKD patients without apnea (39% vs. 19%, p = 0.033), both daytime sleepiness and other symptoms of sleep apnea were considerably less frequent than in OSA patients without a history of kidney disease. CONCLUSIONS: The presence of OSA in patients with CKD is unlikely to be clinically apparent. Consequently, objective cardiopulmonary monitoring during sleep is required to reliably identify this comorbidity.

Declining kidney function increases the prevalence of sleep apnea and nocturnal hypoxia.

BACKGROUND: Sleep apnea is an important comorbidity in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Although the increased prevalence of sleep apnea in patients with ESRD is well established, few studies have investigated the prevalence of sleep apnea in patients with nondialysis-dependent kidney disease, and no single study, to our knowledge, has examined the full spectrum of kidney function. We sought to determine the prevalence of sleep apnea and associated nocturnal hypoxia in patients with CKD and ESRD. We hypothesized that the prevalence of sleep apnea would increase progressively as kidney function declines. METHODS: Two hundred fifty-four patients were recruited from outpatient nephrology clinics and hemodialysis units. All patients completed an overnight cardiopulmonary monitoring test to determine the prevalence of sleep apnea (respiratory disturbance index ≥ 15) and nocturnal hypoxia (oxygen saturation < 90% for ≥ 12% of monitoring). Patients were stratified into three groups based on estimated glomerular filtration rate (eGFR) as follows: eGFR ≥ 60 mL/min/1.73 m(2) (n = 55), CKD (eGFR < 60 mL/min/1.73 m(2) not on dialysis, n = 124), and ESRD (on hemodialysis, n = 75). RESULTS: The prevalence of sleep apnea increased as eGFR declined (eGFR ≥ 60 mL/min/1.73 m(2), 27%; CKD, 41%; ESRD, 57%; P = .002). The prevalence of nocturnal hypoxia was higher in patients with CKD and ESRD (eGFR ≥ 60 mL/min/1.73 m(2), 16%; CKD, 47%; ESRD, 48%; P < .001). CONCLUSIONS: Sleep apnea is common in patients with CKD and increases as kidney function declines. Almost 50% of patients with CKD and ESRD experience nocturnal hypoxia, which may contribute to loss of kidney function and increased cardiovascular risk.

Clinical presentation of obstructive sleep apnea in patients with end-stage renal disease.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is common in patients with end-stage renal disease (ESRD) and is largely underrecognized. Our objective was to determine whether the presentation of OSA in patients with ESRD differs from the stereotypical presentation in the general population (loud snoring, witnessed apnea, and daytime sleepiness in overweight, middle-aged men). METHODS: Seventy-six chronic dialysis patients with OSA were compared to 380 OSA patients with normal renal function who were matched for apnea severity (apnea-hypopnea index). All patients underwent overnight polysomnography and completed the Epworth Sleepiness Scale and a questionnaire to assess symptoms of OSA. RESULTS: Age and gender distribution were similar between groups, however, body mass index was lower in the ESRD group (28 +/- 5 vs. 33 +/- 14 kg/m2). Patients with ESRD were less likely to report snoring (80% vs. 98%), witnessed apnea during sleep (32% vs. 58%), unrefreshing sleep (55% vs. 73%), and morning headaches (15% vs. 27%). Overnight polysomnography revealed less intense snoring and more sleep disturbance in patients with ESRD. The prevalence and severity of self-reported daytime sleepiness was similar between groups. CONCLUSIONS: The presenting symptoms of patients with ESRD and documented OSA differed from a control group of OSA patients matched for AHI. This suggests that the presentation of ESRD patients with OSA may differ from the general population, and this should be appreciated to avoid underdiagnosis of this important comorbidity.

Decreased chemosensitivity and improvement of sleep apnea by nocturnal hemodialysis.

BACKGROUND: Sleep apnea occurs in up to 50% of patients with end-stage renal disease and is improved by nocturnal hemodialysis. We hypothesized that its pathogenesis is related to changes in chemoreflex responsiveness. METHODS: Twenty-four patients receiving conventional hemodialysis (4 h/day, 3 times/week) had overnight polysomnography and measurement of the ventilatory response to carbon dioxide during isoxic hypoxia and hyperoxia using a modified rebreathing technique. Measurements were repeated following conversion from conventional to nocturnal hemodialysis (8 h/night, 3-6 nights/week). Patients were divided into apneic and non-apneic groups based on apnea-hypopnea index > or =15/h at baseline (17 apneics and 7 non-apneics), and the apneic group was further divided into "responders" and "non-responders" based on a significant reduction in AHI at follow-up. RESULTS: Conversion from conventional to nocturnal hemodialysis was associated with a decrease in the ventilatory sensitivity to hypercapnia during hyperoxia in responders (3.2+/-1.0 vs. 2.3+/-1.3 L/min/mmHg) but not in non-responders (2.8+/-1.3 vs. 2.9+/-1.6 L/min/mmHg). The change in ventilatory sensitivity was correlated with the change in apnea-hypopnea index in all apneic patients (r=.528, p=0.029). CONCLUSIONS: Improvement of sleep apnea following conversion from conventional to nocturnal hemodialysis is associated with a decrease in chemoreflex responsiveness. This finding suggests that increased chemoreflex responsiveness contributes to the pathogenesis of sleep apnea in some patients with end-stage renal disease.

Improvement of periodic limb movements following kidney transplantation.

BACKGROUND/AIMS: Periodic limb movements are common in patients with end-stage renal disease. Kidney transplantation significantly improves renal function and may therefore reduce periodic limb movements. We evaluated the effect of kidney transplantation on periodic limb movements in a group of patients with end-stage renal disease. METHODS: Eighteen patients (aged 27-65) who were receiving dialysis and were candidates for living donor or deceased donor kidney transplantation (n = 12) or were predialysis with a suitable living donor arranged (n = 6) were recruited from the transplant clinic. Attended overnight polysomnography was performed before and after kidney transplantation. Patients were divided based on a periodic limb movement index >15 events/h during sleep. RESULTS: Kidney transplantation was associated with a significant reduction in periodic limb movement index in all patients (8 (0-110) events/h vs. 2 (0-80) events/h) and this reduction was greatest in 7 patients with a periodic limb movement index >15 events/h (40 (24-110) events/h to 14 (1-80) events/h, p < 0.005). CONCLUSION: Successful kidney transplantation improves periodic limb movements in patients with end-stage renal disease. This may improve sleep quality and sleep-related quality of life in kidney transplant recipients, which should have a beneficial impact on clinical outcomes.

Sleep monitoring in the intensive care unit: comparison of nurse assessment, actigraphy and polysomnography.

OBJECTIVE: Sleep loss and sleep disruption are common in critically ill patients and may adversely affect clinical outcomes. Although polysomnography remains the most accurate and reliable way to measure sleep, it is costly and impractical for regular use in the intensive care unit. This study evaluates the accuracy of two other methods currently used for measuring sleep, actigraphy (monitoring of gross motor activity) and behavioural assessment by the bedside nurse, by comparing them to overnight polysomnography in critically ill patients. DESIGN: Observational study with simultaneous polysomnography, actigraphy and behavioural assessment of sleep. SETTING: Medical-surgical intensive care unit. PATIENTS AND PARTICIPANTS: Twelve stable, critically ill, mechanically ventilated patients [68 (13) years, Glasgow coma scale 11 (0)]. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Sleep was severely disrupted, reflected by decreased total sleep time and sleep efficiency, high frequency of arousals and awakenings and abnormal sleep architecture. Actigraphy overestimated total sleep time and sleep efficiency. The overall agreement between actigraphy and polysomnography was <65%. Nurse assessment underestimated the number of awakenings from sleep. Estimated total sleep time, sleep efficiency and number of awakenings by nurse assessment did not correlate with polysomnographic findings. CONCLUSIONS: Actigraphy and behavioural assessment by the bedside nurse are inaccurate and unreliable methods to monitor sleep in critically ill patients.

Nocturnal haemodialysis increases pharyngeal size in patients with sleep apnoea and end-stage renal disease.

BACKGROUND: Sleep apnoea is common in patients with end-stage renal disease (ESRD) and is improved by nocturnal haemodialysis (NHD). Recent findings from our laboratory indicate the development of ESRD is associated with pharyngeal narrowing. We hypothesized that NHD increases pharyngeal cross-sectional area and that this is associated with an improvement in sleep apnoea. METHODS: Twenty-four patients (aged 32-68 years), receiving conventional haemodialysis (CHD) (4 h/day, 3 days/week), were recruited for overnight polysomnography and estimation of pharyngeal cross-sectional area at functional residual capacity (FRC) and residual volume (RV). Patients were divided into apnoeic and non-apnoeic groups based on an apnoea-hypopnoea index (AHI) > or = 15/h. Following conversion from CHD to NHD (8 h/night, 3-6 nights/week) all measurements were repeated and apnoeic patients were classified as 'responders' if AHI fell to < 15 events/h. RESULTS: Conversion from CHD to NHD was associated with an increase in pharyngeal cross-sectional area (FRC: 3.29 +/- 0.67 vs 3.39 +/- 0.75 cm(2); RV: 1.91 +/- 0.51 vs 2.13 +/- 0.48 cm(2), P < 0.05), which was not significantly different between groups. Sleep apnoea improved in three patients. CONCLUSIONS: Conversion from CHD to NHD is associated with an increase in pharyngeal cross-sectional area. This may play a role in some patients whose sleep apnoea improves on NHD.

Impact of kidney transplantation on sleep apnoea in patients with end-stage renal disease.

BACKGROUND: Sleep apnoea is common in patients with end-stage renal disease. Although individual case reports have described an improvement in sleep apnoea following kidney transplantation, there have been no longitudinal studies of a case series to determine what proportion of patients with sleep apnoea improve. METHODS: Dialysis-dependent patients awaiting kidney transplantation and pre-dialysis patients with an identified living donor kidney had overnight polysomnography, which was repeated several months after successful kidney transplantation. Patients were divided into apnoeic and non-apnoeic groups based on an apneoa-hypopnoea index (AHI) > 10/h during pre-transplant polysomnography and, following transplantation, apnoeic patients were further divided into responders and non-responders based on >50% reduction in AHI and/or AHI < 10/h. RESULTS: Eighteen patients (11 men, 7 women), aged 27-65, were studied. Pre-transplant sleep apnoea was present in 11 of 18 (61%) patients. Although transplantation was associated with a significant reduction in blood urea nitrogen and serum creatinine, there were no significant changes in AHI (pre vs post: 20.2 +/- 15.1 vs 23.5 +/- 21.3). Among the 11 apnoeic patients, only three met the criteria for a significant improvement ('responder'). There were no patient characteristics, sleep apnoea indices or renal function changes that distinguished responders from non-responders. CONCLUSIONS: Sleep apnoea improves in a minority of patients with end-stage renal disease following successful kidney transplantation. Specific determinants of improvement were not identified.

Comparison of the OxyMask and Venturi mask in the delivery of supplemental oxygen: pilot study in oxygen-dependent patients.

BACKGROUND: The OxyMask (Southmedic Inc, Canada) is a new face mask for oxygen delivery that uses a small 'diffuser' to concentrate and direct oxygen toward the mouth and nose. The authors hypothesized that this unique design would enable the OxyMask to deliver oxygen more efficiently than a Venturi mask (Hudson RCI, USA) in patients with chronic hypoxemia. METHODS: Oxygen-dependent patients with chronic, stable respiratory disease were recruited to compare the OxyMask and Venturi mask in a randomized, single-blind, cross-over design. Baseline blood oxygen saturation (SaO2) was established breathing room air, followed in a random order by supplemental oxygen through the OxyMask or Venturi mask. Oxygen delivery was titrated to maintain SaO2 4% to 5% and 8% to 9% above baseline for two separate 30 min periods of stable breathing. Oxygen flow rate, partial pressure of inspired and expired oxygen (PO2) and carbon dioxide (PCO2), minute ventilation, heart rate, nasal and oral breathing, SaO2 and transcutaneous PCO2 were collected continuously. The study was repeated following alterations to the OxyMask design, which improved clearance of carbon dioxide. RESULTS: Thirteen patients, aged 28 to 79 years, were studied initially using the original OxyMask. Oxygen flow rate was lower, inspired PO2 was higher and expired PO2 was lower while using the OxyMask. Minute ventilation and inspired and expired PCO2 were significantly higher while using the OxyMask, whereas transcutaneous PCO2, heart rate and the ratio of nasal to oral breathing did not change significantly throughout the study. Following modification of the OxyMask, 13 additional patients, aged 18 to 79 years, were studied using the same protocol. The modified OxyMask provided a higher inspired PO2 at a lower flow rate, without evidence of carbon dioxide retention. CONCLUSIONS: Oxygen is delivered safely and more efficiently by the OxyMask than by the Venturi mask in stable oxygen-dependent patients.