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Biomedical subjects

J R Stradling

Publications and source records attributed to J R Stradling.

At least 19 recordsLinked to original sources
PubMed2006

Prevalence of obstructive sleep apnoea in men with type 2 diabetes.

BACKGROUND: A study was undertaken to establish the prevalence of obstructive sleep apnoea (OSA) in men with type 2 diabetes. METHODS: Men with type 2 diabetes from local hospital and selected primary care practitioner databases received questionnaires about snoring, apnoeas, and daytime sleepiness based on the Berlin questionnaire. Selected respondents had overnight oximetry to establish whether they had OSA. Comparisons of oximetry were made with those from a previous general population study. HbA1c results were collected. RESULTS: 1682 men were sent questionnaires, 56% of whom replied. 57% scored as "high" and 39% as "low" risk for OSA; 4% were already known to have OSA. Oximetry was performed in 240 respondents from both risk groups: 31% of the "high" and 13% of the "low" risk group had significant OSA (more than 10 >4% Sao(2) dips/hour or Sao(2) tracing consistent with OSA). These results were verified by detailed sleep studies. Extrapolation of the oximetry data to the questionnaire respondent population suggests that 23% had OSA. Comparison of the oximetry results with men from a previous general population study (using only more than 10 >4% Sao(2) dips/hour to define OSA) showed the prevalence of OSA is significantly higher in this diabetes population (17% v 6%, p<0.001). Multiple linear regression revealed BMI and diabetes as significant independent predictors of OSA. Following correction for BMI (which explained 13% of the variance in OSA), diabetes explained a further 8% of the variance (p<0.001). There was a low correlation between OSA severity and HbA1c in the subgroup recruited from the hospital database (r = 0.2, p = 0.006) which remained significant after allowing for obesity (p = 0.03). CONCLUSIONS: OSA is highly prevalent in men with type 2 diabetes; most are undiagnosed. Diabetes itself may be a significant independent contributor to the risk of OSA.

Adolescent↗
PubMed2006

Continuous positive airway pressure does not reduce blood pressure in nonsleepy hypertensive OSA patients.

Obstructive sleep apnoea (OSA) is associated with high cardiovascular morbidity and mortality. Several randomised controlled trials have shown that continuous positive airway pressure (CPAP) treatment of OSA reduces blood pressure (BP). This randomised, sham-placebo controlled crossover trial assesses whether CPAP produces a similar clinically significant fall in BP in hypertensive OSA patients, but without hypersomnolence. Thirty-five, nonsleepy, hypertensive patients with OSA were treated with CPAP for 1 month, randomised first to either therapeutic or sham-placebo (subtherapeutic CPAP, about 1 cmH(2)O pressure). The second months' alternative treatment followed a 2-week washout period. BP was measured over 24 h, before and at the end of the two treatment periods: mean 24-h BP was the primary outcome variable. There was no overall significant difference in mean 24-h BP: the change in mean 24-h BP on therapeutic CPAP was -2.1 mmHg (sd 8.1), and -1.1 mmHg (sd 8.1) on subtherapeutic CPAP, with a difference of 0.7 mmHg (95% confidence interval (CI) +2.9- -4.4). There was a small significant fall in Epworth Sleepiness Score, therapeutic (-1.4) versus sham (-0.3), and difference -1.2 (95% CI -2.0- -0.4), but no change in objective sleepiness. In nonhypersomnolent hypertensive patients with obstructive sleep apnoea, there is no significant fall in mean 24-h blood pressure with continuous positive airway pressure, in contrast to the fall seen in hypersomnolent patients with obstructive sleep apnoea.

Adult↗
PubMed2005

Comparison of three ways to determine and deliver pressure during nasal CPAP therapy for obstructive sleep apnoea.

BACKGROUND: The simplest method of initiating and maintaining therapeutic continuous positive airways pressure (CPAP) therapy for obstructive sleep apnoea (OSA) has not been established. METHODS: Ninety eight subjects with OSA requiring CPAP treatment (more than 10 dips in oxygen desaturation of >4% per hour of sleep study and Epworth Sleepiness Score (ESS) >9) were randomised prospectively to three different methods of CPAP delivery for 6 months: (1) autotitration pressure throughout; (2) autotitration pressure for 1 week followed by fixed pressure (95th centile) thereafter; and (3) fixed pressure determined by algorithm (based on neck size and dip rate). Patients and investigators were blind to group allocation. One week after initiation the patients were routinely reviewed by sleep nurses. Study assessments took place before starting CPAP treatment and 1 and 6 months after to assess ESS, maintenance of wakefulness test, 24 hour blood pressure, general health (SF-36), and sleep apnoea related quality of life. CPAP internal monitoring data were also collected. RESULTS: There were no significant differences in any of the outcome measures or CPAP monitoring data between the three groups. The 95th centile CPAP pressures delivered in the 6 month and 1 week autotitration groups were higher than in the algorithm group, but the median pressures were lowest in the 6 month autotitration group. CONCLUSIONS: The method of determining CPAP pressure for treatment of moderate to severe OSA makes no significant difference to clinical outcome measures. The autotitration CPAP machine used has no advantage in this setting over simpler methods of pressure determination.

Adolescent↗
PubMed2004

Relative accuracy of algorithm-based prescription of nasal CPAP in OSA.

BACKGROUND: Patients with OSA on nasal continuous positive airway pressure (CPAP) have considerable night-to-night variation in their pressure requirements, suggesting that a one-night titration might not be very precise. This study investigates the likely error incurred using a one-night titration, and explores whether an algorithm-based approach to determine the pressure is as accurate. METHODS: Thirty patients with OSA used an autotitrating CPAP device for 28 nights and the average was regarded as the 'reference' pressure for that patient. Using estimates of precision and bias, this 'reference' pressure was compared with (1) an algorithm-derived pressure (based on neck circumference and OSA severity), (2) a one-night titration (using four alternative nights), and (3) a fixed pressure of 10 cmH2O. RESULTS: The mean 'reference' pressure for the group was 9.83 (SD 2.12) cmH2O. There was little bias from any of the alternatives. However, the precision varied between 1.65 and 2.45 cmH2O for the four one-night titrations, was 2.00 for the algorithm, and was 2.12 using a fixed pressure of 10 cmH2O. CONCLUSIONS: Considerable night-to-night variation means that a one-night titration is not very precise and is subject to random variation. A one-night titration has a similar inaccuracy to that resulting from using an algorithm, based on OSA severity and neck circumference. Setting all patients with OSA at 10 cmH2O is little worse.

Algorithms↗
PubMed2004

A novel, simplified approach to starting nasal CPAP therapy in OSA.

BACKGROUND: Due to ever increasing referral rates, we have had to move the nasal CPAP induction program for patients with obstructive sleep apnoea (OSA) out of the sleep laboratories and into an outpatient setting. We report the effects this has had on patient outcomes. METHODS: The last 75 patients with OSA who had an overnight CPAP titration in the sleep laboratory (group 1) were compared with the first 75 coming to an afternoon clinic and set up on CPAP in groups, and who had their CPAP pressure determined from an algorithm (group 2). They were assessed at 1 and 11 months using the Epworth Sleepiness Score, compliance with CPAP (h/night), whether still using CPAP, and the number of clinic appointments required in the first 11 months. RESULTS: The two groups were similar at baseline. There were no differences in any of the outcome measures. ESS values fell from 14.6 to 5.0 and from 14.0 to 5.1 at 11 months in groups 1 and 2, respectively: compliance, 5.2 versus 5.1 h/night; clinic appointments, 1.75 versus 1.96; discontinuation rates at 1 month, 8% and 7%, and at 11 months, 25% and 21%. CONCLUSIONS: Using these simple outcome measures, we have shown that using an outpatient-based approach, and CPAP pressure based on an algorithm, have not reduced the efficacy of our CPAP induction program for patients with OSA.

Algorithms↗
PubMed2004

Sleep. 1: Obstructive sleep apnoea/hypopnoea syndrome: definitions, epidemiology, and natural history.

Arguments over the definition of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) have still not been satisfactorily resolved. As a result, robust estimates of the prevalence of OSAHS are not possible. New approaches are needed to identify those who have "CPAP responsive" disease, enabling more accurate estimates to be made of the prevalence of the sleep apnoea syndrome in the community.

Age Factors↗
PubMed2004

Circulating cardiovascular risk factors in obstructive sleep apnoea: data from randomised controlled trials.

BACKGROUND: Obstructive sleep apnoea (OSA) is associated with high cardiovascular morbidity and mortality and is an independent risk factor for hypertension. Novel circulating cardiovascular risk markers enabling a more accurate prediction of cardiovascular risk have been identified. Examination of these markers may clarify the increased risk in OSA and contribute to an analysis of the benefits of treatment. METHODS: Plasma levels of total cholesterol and triglyceride and activated coagulation factors XIIa and VIIa, factors VII, VIII, XII, fibrinogen, thrombin-antithrombin (TAT), von Willebrand factor antigen (vWFAg), soluble P-selectin (sP-sel), and homocysteine were measured before and after treatment for 1 month with therapeutic or subtherapeutic (control) continuous positive airways pressure (CPAP) in 220 patients with OSA. RESULTS: Levels of activated coagulation factors XIIa, VIIa, TAT and sP-sel were higher in OSA patients at baseline than in unmatched controls, but did not fall with 1 month of therapeutic CPAP treatment. The raised sP-sel levels correlated only with body mass index (p = 0.002). There was a trend towards a significant fall in total cholesterol with therapeutic CPAP (p = 0.06) compared with the control group. In the therapeutic group there was a clinically significant mean fall in total cholesterol of 0.28 mmol/l (95% confidence interval 0.11 to 0.45, p = 0.001) which may reduce cardiovascular risk by about 15%. CONCLUSION: A number of activated coagulation factors are increased in untreated OSA patients, potentially contributing to vascular risk, but they do not fall with 1 month of CPAP treatment. Nasal CPAP may produce a clinically relevant fall in total cholesterol level, potentially reducing cardiovascular risk, but this needs to be verified in a larger prospective study.

Adult↗
PubMed2003

Endocrine effects of nasal continuous positive airway pressure in male patients with obstructive sleep apnoea.

OBJECTIVE: Obstructive sleep apnoea (OSA) is a relatively common condition producing disabling somnolence and profound physiological responses to hypoxaemic episodes during sleep, including significant oscillations in blood pressure. This study aimed to provide controlled data on the interaction between OSA and endocrine axes to establish whether overrepresentation of pathology such as hypertension and hypogonadism in OSA subjects might have an endocrine basis. DESIGN, SETTING AND SUBJECTS: Parallel randomized sham placebo controlled 1-month trial of nasal continuous positive airway pressure (nCPAP) in 101 male subjects with OSA presenting to a respiratory sleep clinic. METHODS: Analysis of gonadotrophins, testosterone, sex hormone binding protein (SHBG), prolactin, cortisol, thyroid stimulating hormone (TSH), free thyroxine (free T4), insulin-like growth factor-1 (IGF-1), renin and aldosterone were performed at baseline and after 1 month's active or placebo nCPAP intervention. Quality of life questionnaire scoring was also recorded over the same time period. RESULTS: Testosterone and SHBG showed significant negative correlations with baseline OSA severity. Active treatment of OSA produced SHBG elevation and TSH reduction (P< or =0.03). Both groups showed an increase in aldosterone (P<0.001) and IGF-1 (P< or =0.03), associated with a large improvement in subjective quality of life scoring. CONCLUSIONS: These findings demonstrate significant changes in endocrine axes not previously reported in a placebo-controlled trial. OSA is a recognized reversible cause of testosterone reduction; SHBG suppression correlating to baseline OSA severity supports a diagnosis of secondary hypogonadism. Significant rises in aldosterone and IGF-1 on treatment coincide with increased physical activity and an improved quality of life score.

Aldosterone↗
PubMed2003

Caffeine levels following treatment of obstructive sleep apnoea.

BACKGROUND: Randomised trials show that treatment of obstructive sleep apnoea (OSA) with nasal continuous positive airway pressure (CPAP) greatly improves sleepiness and also lowers diurnal systemic blood pressures (BP). Such patients consume more coffee than controls (presumably to combat their sleepiness) and might reduce their consumption following effective treatment, thus lowering BP by this mechanism rather than via a direct effect of alleviating OSA. METHODS: Plasma caffeine levels before and after treatment with either therapeutic (n=52) or subtherapeutic (control, n=49) CPAP were measured in stored blood samples from a previous randomised controlled trial of CPAP for 4 weeks in patients with OSA. RESULTS: There was a small significant rise in caffeine levels when the two groups were analysed as a whole (p=0.02), but not individually. Despite the fall in sleepiness measured objectively in the therapeutic CPAP group, there was no difference in absolute (or change in) caffeine levels between the two groups (mean (SE) micro mol/l; therapeutic CPAP 9.2 (1.2), 10.2 (1.0), subtherapeutic 6.7 (0.9), 8.6 (0.9) before and after treatment, respectively). CONCLUSION: Reduced coffee consumption is unlikely to be the explanation for the falls in BP following treatment of OSA.

Blood Pressure↗
PubMed2002

Sleep studies for sleep apnoea.

Sleep studies have grown to encompass a broad range of technologies employed to study and diagnose a variety of sleep disorders. From their inception in neurophysiology laboratories interested in investigating primary disorders of sleep architecture from psychiatric illness, their remit has widened such that their most common role is currently to diagnose secondary sleep disruption from respiratory, cardiovascular or other systemic causes. This review outlines the pathophysiology of obstructive sleep apnoea in particular and how sleep studies have improved our understanding of the complex dynamic changes in blood gas tensions, cardiovascular control and cerebral arousal that occur with these repetitive events. We review the historical development of standard laboratory-based sleep studies and discuss their limitations in staging sleep, reflecting the episodes of increased upper airway resistance that underlie these disorders and their ability to predict individuals' symptoms or response to medical or surgical therapies. We then describe some alternative signals that have been employed to monitor the physiological changes in upper airway resistance and arousal with a discussion of some of the evidence that these 'limited' studies may provide diagnostic information that can guide clinical decision making and may predict the outcome without the need, in some cases, for more complex and costly laboratory-based studies.

Humans↗
PubMed2002

Evidence for persistence of upper airway narrowing during sleep, 12 years after adenotonsillectomy.

AIMS: To establish whether subjects with previous evidence of sleep apnoea prior to adenotonsillectomy continue to have evidence of narrower upper airways during sleep, 12 years later. METHODS: Twenty subjects (median age 16 years) underwent repeat sleep studies at home, 12 years after such studies had shown significant sleep apnoea in many of them prior to an adenotonsillectomy. Twenty control subjects, also studied 12 years ago, underwent repeat home sleep studies as well. The sleep studies provided information on snoring, hypoxia, and inspiratory effort (from measures of pulse transit time). A questionnaire was also administered, the subjects were weighed, and their heights measured. RESULTS: There was more reported snoring in the previous adenotonsillectomy group (50% versus 20%) and also during the sleep study (80 versus 31 snores per hour). The measure of inspiratory effort overnight was higher in the previous adenotonsillectomy group (15.6 versus 12.3 ms). Allowance for potentially confounding variables (obesity and nasal congestion) partially reduced the statistical significance of the difference in snoring, but not that of the measure of inspiratory effort. CONCLUSION: Results suggest that a narrower upper airway during sleep, to the point of snoring, persists 12 years after adenotonsillectomy, and may partly account for the occurrence earlier of preoperative sleep apnoea while adenotonsillar hypertrophy was present. It is not known if this narrowing is one of the risk factors for later development of adult sleep apnoea.

Adenoidectomy↗
PubMed2002

Can mandibular advancement devices be a satisfactory substitute for short term use in patients on nasal continuous positive airway pressure?

BACKGROUND: Mandibular advancement devices (MADs) can successfully control both snoring and obstructive sleep apnoea (OSA). Many patients on nasal continuous positive airway pressure (NCPAP) for OSA would like a more portable alternative, even if only temporarily. This study assesses what proportion of patients with OSA already on NCPAP can successfully use a MAD for short periods (up to 1 month) as a temporary alternative to NCPAP. METHODS: Fifty patients with OSA, already on NCPAP for at least 3 months, were recruited by invitation. They were provided with a simple fixed MAD estimated to provide 75% of maximum mandibular protrusion. Sleep studies using a portable home recorder were performed on and after three nights without NCPAP to provide control data. Following acclimatisation to the MAD, sleep studies were also planned after 3, 7, and 28 days while using the MAD. If their overnight >4% SaO(2) dips per hour deteriorated to >20 or the Epworth sleepiness score (ESS) rose to >9 (or increased by >4 over baseline) on nights 3 or 7, they were then deemed to have failed the trial and were withdrawn. RESULTS: Of the 50 patients entered, one had inadequate teeth for a MAD and 31 gave up trying to use the device during the acclimatisation period because of side effects. Of the 18 prepared to use the device, two patients failed at night 3, five at night 7, and two at night 28. Thus, nine patients remained controlled by our criteria at night 28. On average, sleep study indices while using the MAD were poor compared with the night on NCPAP. CONCLUSIONS: Simple MADs are poorly tolerated by patients with OSA already on NCPAP. OSA was adequately controlled by our criteria in 32% of those recruited for the equivalent of a weekend, in 22% for 1 week, and in 18% for up to 1 month. Better tolerated devices would be likely to improve on these figures.

Heart Rate↗
PubMed2001

Case control study of cerebrovascular damage defined by magnetic resonance imaging in patients with OSA and normal matched control subjects.

STUDY OBJECTIVES: To assess whether MRI detectable evidence of silent cerebrovascular disease is more prevalent in patients with obstructive sleep apnea (OSA) when compared to carefully matched control subjects. DESIGN AND SETTING: Case-control study of patients with OSA attending a specialist sleep clinic and matched control subjects drawn from the normal community. PARTICIPANTS: Forty-five sleep clinic patients with moderate to severe OSA and excessive daytime sleepiness, matched to 45 control subjects without excessive sleepiness or evidence of OSA on a sleep study. Matched variables included age, body mass index (BMI), alcohol and cigarette consumption, treated hypertension, and ischaemic heart disease. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: All subjects underwent 24-hour ambulatory blood pressure recordings (before treatment in OSA patients) and sagittal T1, axial T2, and coronal dual echo cerebral MRI imaging to detect clinically silent abnormalities related to hypertensive cerebrovascular disease; areas of high signal foci in deep white matter (DWM), lacunae, and periventricular hyperintensity. Lacunae/high signal foci in DWM and/or periventricular hyperintensity were present in 15 (33%) OSA subjects and 16 (35%) controls, despite significant increases in mean daytime diastolic blood pressure (4.6mmHg, p<0.05), and both nighttime diastolic (7.2mmHg, p<0.001) and systolic blood pressures (9.2mmHg, p<0.05) in OSA subjects. These data exclude more than a 17% excess prevalence of MRI detected minor cerebrovascular disease in the OSA patients, with 95% confidence. CONCLUSIONS: Sub-clinical cerebrovascular disease is prevalent in both clinic patients with OSA and their matched control subjects. Despite the increased arterial blood pressures, there is, however, no apparent excess of MRI-evident subclinical cerebrovascular disease in patients with OSA compared to appropriately matched control subjects.

Adult↗
PubMed2001

Is (re)titration of nasal continuous positive airway pressure for obstructive sleep apnoea necessary?

OBJECTIVE: To assess changes in nasal continuous positive airway pressure (nCPAP) pressure requirements across time in obstructive sleep apnoea (OSA), and whether routine retitrations are indicated. BACKGROUND: Most sleep laboratories perform one nCPAP titration, although some authors have found changes in pressures with time. A cohort of patients with OSA in a randomised controlled trial of nCPAP provided us with data on changes in titration pressures with time. METHODS: One hundred and one patients with symptomatic OSA (Epworth Sleepiness Scale > or =10, and >10 episodes/h of >4% dips in SaO(2) overnight) were recruited to a 1 month trial comparing real (autotitrated) and placebo nCPAP. At 1 month all patients were titrated and received real nCPAP thereafter. Eighty five were retitrated at about 6 months. RESULTS: Average pressures did not change between the initial value and 1 month (95th centile, 8.47 (SD 3.00), 8.94 (2.85) cm H(2)O), although there were large individual changes (mean difference, +0.47, SD 2.30, range -5 to +6 cm H(2)O). There was a small fall at 6 months (mean difference -0.68, SD 2.60, range -6 to +6 cm H(2)O, P<0.03) with no suggestion that the changes from 1-6 months were clinically important. CONCLUSIONS: This study suggests that routine nCPAP retitrations are not necessary. In conjunction with other published data, the night to night variation we found implies that a nCPAP calibration using an algorithm (based on obesity and OSA severity) might be as clinically successful as conventional one night titrations. However, further studies will be needed to specifically confirm this hypothesis.

Clinical Trial↗
PubMed2001

Comparison of the effects of sleep deprivation, alcohol and obstructive sleep apnoea (OSA) on simulated steering performance.

Patients with obstructive sleep apnoea (OSA) are reported to have an increased risk of road traffic accidents. This study examines the nature of the impairment during simulated steering in patients with OSA, compared to normal subjects following either sleep deprivation or alcohol ingestion. Twenty-six patients with OSA and 12 normal subjects, either deprived of one night's sleep or following alcohol ingestion [mean (SD) alcohol blood level 71.6 mg dl(-1) (19.6)], performed a simulated steering task for a total of 90 min. Performance was measured using the tendency to wander (SD), deterioration across the task, number of 'off-road' events and the reaction time to peripheral events. Control data for OSA, sleep deprivation and alcohol were obtained following treatment with nasal continuous positive airway pressure (nCPAP), after a normal night of sleep, and following no alcohol, respectively. Patients with untreated OSA, and sleep-deprived or alcohol-intoxicated normal subjects performed significantly less well, compared to their respective controls (P<0.01 for all tests), with untreated OSA lying between that of alcohol intoxication and sleep deprivation. Alcohol impaired steering error equally throughout the whole drive, whilst sleep deprivation caused progressive deterioration through the drive, but not initially. Untreated OSA was more like sleep deprivation than alcohol, although there was a wide spread of data. This suggests that the driving impairment in patients with OSA is more compatible with sleep deprivation or fragmentation as the cause, rather than abnormal cognitive or motor skills.

Adult↗
PubMed2001

Long-term benefits in self-reported health status of nasal continuous positive airway pressure therapy for obstructive sleep apnoea.

Doubt has been expressed about the efficacy of nasal continuous positive airways pressure (NCPAP) therapy for sleep apnoea. Recent evidence from a randomized controlled trial of 1 month duration, suggested that NCPAP therapy can have a substantial impact on subjective and clinical outcomes in the short term, but data was not available to determine whether these effects were sustained over the long term. This study, an extension of the original trial, examined whether the beneficial impacts of NCPAP continued over the longer term. Patients were followed-up 1 month after being placed on active or sub-therapeutic NCPAP. They completed health status measures and a clinical test of sleepiness. After this period, all patients were placed on NCPAP and followed up 5 months later. The beneficial impact of NCPAP on sleep apnoea was sustained on all measures at follow-up. Furthermore, those who had initially been in the sub-therapeutic arm gained scores after 5 months of NCPAP similar to those of the active group. The impact of NCPAP appears sustained in the longer term. Subjective health status instruments have been advocated as important outcome points in randomized trials. This study would support such a use, and shows the important role of patient report in the evaluation of health care.

Follow-Up Studies↗