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Biomedical subjects

J R Stradling

Publications and source records attributed to J R Stradling.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effect of measuring ambulatory blood pressure on sleep and on blood pressure during sleep.

OBJECTIVE: To assess whether recording of ambulatory blood pressure at night causes arousal from sleep and a change in the continuous blood pressure recorded simultaneously. DESIGN: Repeated measurement of blood pressure with two ambulatory blood pressure machines (Oxford Medical ABP and A&D TM2420) during continuous measurement of beat to beat blood pressure and continuous electroencephalography. SETTING: Sleep research laboratory. SUBJECTS: Six normal subjects. MAIN OUTCOME MEASURES: The duration of electroencephalographic arousal and the beat to beat changes in blood pressure produced by the measurement of ambulatory blood pressure; the size of any changes that this arousal and change in blood pressure produced in the blood pressure recorded by the ambulatory machine. RESULTS: Both ambulatory blood pressure machines caused arousal from sleep: the mean duration of arousal was 16 seconds (95% range 0-202) with the ABP and 8 seconds (0-73) with the TM2420. Both also caused a rise in beat to beat blood pressure. During non-rapid eye movement sleep, this rise led to the ABP machine overestimating the true systolic blood pressure during sleep by a mean of 10 (SD 14.8) mm Hg and the TM2420 by a mean of 6.3 (8.2) mm Hg. On average, diastolic pressure was not changed, but measurements in individual subjects changed by up to 23 mm Hg. These changes varied in size among subjects and stages of sleep and were seen after measurements that did not cause any electroencephalographic arousal. CONCLUSIONS: Ambulatory blood pressure machines cause appreciable arousal from sleep and therefore alter the blood pressure that they are trying to record. This effect should be taken into account when recordings of blood pressure at night are interpreted in clinical work and epidemiological research.

Adult↗
PubMed1994

Ambulatory blood pressure and left ventricular hypertrophy in subjects with untreated obstructive sleep apnoea and snoring, compared with matched control subjects, and their response to treatment.

1. Obstructive sleep apnoea and snoring are associated with daytime hypertension. It is uncertain whether this association is directly due to the disturbed sleeping respiration or the result of confounding variables, particularly obesity, smoking and alcohol intake. 2. Ambulatory blood pressure and echocardiographic left ventricular muscle mass were measured in 19 patients with obstructive sleep apnoea, 19 men who snore without apnoea and 38 control subjects matched for age, sex, body mass index, smoking and alcohol intake. Ambulatory blood pressure was also measured before and after treatment in 11 patients with obstructive sleep apnoea and their matched control subjects. 3. Compared with matched control subjects, untreated obstructive sleep apnoea and snoring were not associated with an increase in daytime blood pressure. A daytime elevation of either systolic or diastolic blood pressure of > 3.8 mmHg due to obstructive sleep apnoea or snoring was excluded with 95% confidence in each of the study groups. Daytime blood pressure was also unchanged when obstructive sleep apnoea was treated with nasal continuous positive airway pressure. Night-time blood pressure was not significantly different in the patients with obstructive sleep apnoea or the snorers when compared with their matched control subjects. However, a fall in night-time systolic blood pressure was seen in the patients with obstructive sleep apnoea after treatment [fall in systolic blood pressure -6.3 (SD 8.2) mmHg, P < 0.02]. 4. Left ventricular diameter, wall thickness and calculated mass were similar in each of the study groups and their matched control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure Determination↗
PubMed1994

Plasma insulin and lipid levels in untreated obstructive sleep apnoea and snoring; their comparison with matched controls and response to treatment.

Obstructive sleep apnoea (OSA), and snoring are associated with coronary heart disease. To assess whether OSA or snoring may contribute to this by raising fasting lipid or insulin levels, venous fasting total cholesterol, triglyceride, very-low-density lipoprotein, low-density lipoprotein, high-density lipoprotein, and insulin were measured in 15 untreated OSA patients and 18 snorers. Each of these subjects was individually matched to a control of the same sex, age +/- 10%, body index +/- 15%, smoking and drinking habits. This produced study groups which did not differ significantly by any of these criteria. Fasting venous blood samples were collected at 06.30 hours following polysomnography, and analysed blind of the subjects respiratory status. The OSA patients were then treated with nasal continuous positive airway pressure. In 10 of these subjects lipid and insulin levels were repeated after more than three months treatment. Lipid and insulin levels were also remeasured in the controls matched to these 10 subjects. The end points were compared with paired t-tests. There was no difference in any of the end points when the untreated OSA patients and the snorers were compared to their matched controls (P > 0.25 for all comparisons), and none of the indices changed when OSA was corrected with nasal continuous positive airway pressure (P > 0.25 for all comparisons). Patients with obstructive sleep apnoea or snoring do not have significant fasting hyperlipidaemia or hyperinsulinaemia when compared to carefully matched controls. These factors are therefore unlikely to be the cause of the excess cardiovascular mortality experienced by this patient group.

Journal Article↗
PubMed1994

Natural history of snoring and related behaviour problems between the ages of 4 and 7 years.

In 1989-90 a survey was carried out of the prevalence of snoring and related symptoms in 782 4 to 5 year old children. Two years later, in 1992, the same group of children was studied to gather information on the natural history of snoring and the related behaviour problems. A total of 507/782 (64.8%) completed questionnaires were received. Comparison of the responses with the 1989-90 survey showed that those who did not reply to the questionnaire were no different from the respondents in terms of the prevalence of snoring, daytime sleepiness, hyperactivity, and restless sleep. The overall prevalence of habitual snoring did not change between the two surveys (12.1% in 1989-90 v 11.4% in 1992), though more than half of the children who snored habitually in the original survey no longer did so. There was little change in the prevalence of hyperactivity (24.2% in 1989-90 v 20.7% in 1992) or restless sleep (both 39%) among the 507 who responded to the present survey. The prevalence of daytime sleepiness, however, did decrease substantially (20.7% in 1989-90 v 10.2% in 1992). There was moderate agreement between the individual questionnaire responses for the 1989-90 and 1992 surveys for snoring (weighted kappa 0.52), but poor agreement for the other symptoms (daytime sleepiness 0.37, hyperactivity 0.35, and restless sleep 0.38). Trend analysis showed that the increasing prevalence of sleepiness, hyperactivity, and restless sleep across the snoring categories was highly significant. Daytime sleepiness, hyperactivity, and restless sleep were all significantly more common in the habitual snorers than in those who never snored. Relative risks (95% confidence interval) were as follows: daytime sleepiness 6.13 (2.5 to 14.9), hyperactivity 2.78 (1.6 to 4.7), and restless sleep 2.3 (1.6 to 3.2). Though habitual snoring and the associated behaviour problems resolved spontaneously over two years in about half of the children with these symptoms, there is still the same overall percentage with these problems due to the emergence of new cases.

Child↗
PubMed1994

Non-invasive beat to beat arterial blood pressure during non-REM sleep in obstructive sleep apnoea and snoring.

BACKGROUND: Obstructive sleep apnoea, and possibly snoring, are associated with a poorly understood increase in cardiovascular mortality which may be explained by their effects on systemic blood pressure during sleep. This study compares changes in mean blood pressure during obstructive sleep apnoea and snoring without apnoeas with those in matched control subjects during non-REM sleep. METHODS: Eighteen men with obstructive sleep apnoea, 16 men who snored without apnoeas, and 34 control subjects matched for age, sex, obesity, smoking, and alcohol intake were studied. During polysomnography non-invasive mean blood pressure (Finapres) was recorded from each cardiac cycle during non-REM sleep and averaged over a 10 minute period. This was compared with the blood pressure during 10 minutes before sleep onset. The changes in the patients' sleeping blood pressure were compared with those in their individually matched control subjects. RESULTS: Compared with the control subjects the change in mean (SD) arterial blood pressure between being awake and asleep was higher during obstructive sleep apnoea (+6.5 (9) mm Hg v-2 (6.5), difference 8.5 (11)), and the rise from wakefulness to sleep in the obstructive sleep apnoea group was itself significant. The average mean arterial pressure was not raised in those who snored without apnoeas compared with either the control subjects or during wakefulness. CONCLUSIONS: Average mean arterial pressure is higher during obstructive sleep apnoea than it is during wakefulness, while normal subjects show a fall in blood pressure at sleep onset. This sleep related rise in blood pressure may contribute to the excess cardiovascular morbidity and mortality experienced by patients with this condition.

Blood Pressure↗
PubMed1993

Snoring, sleep disturbance, and behaviour in 4-5 year olds.

Parents of 996 children aged 4-5 years identified consecutively from the Oxford health visitor register were asked to complete a questionnaire about breathing disorders during sleep. A total of 782 (78.5%) was returned. Ninety five (12.1%) children were reported to snore on most nights. Habitual snoring was significantly associated with daytime sleepiness, restless sleep, and hyperactivity. The questionnaire responses were used to select two subgroups, one at high risk of a sleep and breathing disorder and a control group. These children (132 in total) were monitored at home with overnight video recording and oximetry, and had formal behavioural assessment using the Conners scale. Seven (7/66) children from the high risk group and none from the control group had obvious sleep disturbance consequent on snoring and upper airway obstruction. Thus our estimate of the prevalence of sleep and breathing disorders in this age group is 7/996 or 0.7%. The high risk group had significantly higher nocturnal movement, oxygen saturation dip rates, and overnight pulse rates than the controls. Maternal but not paternal smoking was associated with the high risk group. Parents and teachers thought those in the high risk group were more hyperactive and inattentive than the controls, but only their parents thought them more aggressive. Significant sleep and breathing disorders occur in about 0.7% of 4-5 year olds. Children whose parents report snoring and sleep disturbance have objective evidence of sleep disruption and show more behaviour problems than controls.

Child, Preschool↗
PubMed1993

Identification of sleep disruption and sleep disordered breathing from the systolic blood pressure profile.

BACKGROUND: Respiratory sleep studies are frequently performed to identify sleep disruption resulting from upper airway obstruction. Traditional polysomnographic studies may not detect brief recurrent sleep disruption and thus fail to recognise a significant problem when apnoea, hypopnoea, or arterial desaturation are not present. Arousal from sleep causes a transient blood pressure rise, and each inspiration causes a transient blood pressure fall. This study assesses whether these blood pressure changes are a useful indirect marker of disturbed sleep, obstructed sleep apnoea, and snoring related sleep disturbance. METHODS: Computer algorithms were developed to identify blood pressure falls caused by inspiration and rises related to arousal from 286 sleeping blood pressure samples of a consistent respiratory state drawn from 51 polysomnographic studies. From these samples, normal ranges for the number of arousal related systolic rises and the average size of the inspiratory falls were established. These were then applied prospectively to all night unedited blood pressure recordings from a further 20 subjects. RESULTS: The size of the inspiratory falls in blood pressure progressively increased from normal sleep, through snoring, to frank obstructive sleep apnoea. The 95th centile of normal was 12.5 mm Hg. The number of arousal related blood pressure rises also increased during obstructive sleep apnoea and periods of snoring with associated arousals, compared with normal undisturbed sleep, and all these periods of disturbed sleep included more than 30 such rises per hour. When these blood pressure features were examined in the 20 subjects studied prospectively, the six with a sleep related breathing disorder could all have been identified from their systolic blood pressure profile alone. CONCLUSIONS: The systolic blood pressure profile may be helpful in identifying patients with obstructive sleep apnoea, snoring with arousals, or other sleep disruption syndromes.

Adult↗
PubMed1993

Arterial blood pressure responses to graded transient arousal from sleep in normal humans.

During obstructive sleep apnea, transient arousal at the resumption of breathing is coincident with a substantial rise in blood pressure. To assess the hemodynamic effect of arousal alone, 149 transient stimuli were administered to five normal subjects. Two electroencephalograms (EEG), an electrooculogram, a submental electromyogram (EMG), and beat-to-beat blood pressure (Finapres, Ohmeda) were recorded in all subjects. Stimulus length was varied to produce a range of cortical EEG arousals that were graded as follows: 0, no increase in high-frequency EEG or EMG; 1, increased high-frequency EEG and/or EMG for < 10 s; 2, increased high-frequency EEG and/or EMG for > 10 s. Overall, compared with control values, average systolic pressure rose [nonrapid-eye-movement (NREM) sleep 10.0 +/- 7.69 (SD) mmHg; rapid-eye-movement (REM) sleep 6.0 +/- 6.73 mmHg] and average diastolic pressure rose (NREM sleep 6.1 +/- 4.43 mmHg; REM sleep 3.7 +/- 3.02 mmHg) over the 10 s following the stimulus (NREM sleep, P < 0.0001; REM sleep, P < 0.002). During NREM sleep, there was a trend toward larger blood pressure rises at larger grades of arousal (systolic: r = 0.22, 95% confidence interval 0.02-0.40; diastolic: r = 0.48, 95% confidence interval 0.31-0.62). The average blood pressure rise in response to the grade 2 arousals was approximately 75% of that during obstructive sleep apnea. Arousal stimuli that did not cause EEG arousal still produced a blood pressure rise (mean systolic rise 8.6 +/- 7.0 mmHg, P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Nasal continuous positive airway pressure in chronic heart failure with sleep-disordered breathing.

Nasal continuous positive airway pressure (NCPAP) has been reported to improve daytime symptoms in patients with sleep disordered breathing due to heart failure. To examine this in a controlled manner, eight men with stable chronic heart failure (mean left ventricular ejection fraction 18% and mean frusemide dose 160 mg) were entered into a controlled trial of domiciliary nocturnal NCPAP. At polysomnography (with sleep apnea quantified as the number of > 4% dips in arterial saturation per hour), seven had nocturnal Cheyne-Stokes respiration (SaO2 dip rate 3 to 27/hr), and one both central and obstructive apneas (SaO2 dip rate 8/hr). After 2 wk nocturnal domiciliary NCPAP at < 1.5 cm H2O (placebo) and 7.5 cm H2O (active) in random order, bicycle exercise tolerance and heart failure symptoms (modified Likert questionnaire) were assessed by an observer unaware of the patients' NCPAP status. Pulse oximetry (all subjects) and radionuclide estimated left ventricular ejection fraction (three subjects) were also measured at the end of each period. Two subjects withdrew from the study because of worsening heart failure during active NCPAP (7.5 cm H2O), and one of these subjects died. In the remaining six subjects exercise tolerance, symptom scores, and the severity of sleep apnea were similar on active NCPAP compared with placebo. When it was measured, resting left ventricular ejection fraction was lower on active therapy than on placebo. These data exclude a 25% improvement in exercise tolerance with 95% confidence and suggest that a study of 160 subjects would be needed to exclude a 10% change in symptom score.(ABSTRACT TRUNCATED AT 250 WORDS)

Cheyne-Stokes Respiration↗
PubMed1992

Prevalence of sleep apnoea in patients over 40 years of age with spinal cord lesions.

Twenty two patients over the age of 40 with stable spinal cord damage underwent overnight sleep studies to investigate the prevalence of sleep apnoea. Ten patients had some evidence of obstructive sleep apnoea (OSA). Hypoxic events were scored as number of dips of SaO2 more than 4% below the preceding 10 minute average (> 4% SaO2 dip rate). All the patients had more than five such dips per hour and six had clearly abnormal dip rates of more than 15 per hour. Two other patients had dip rates above 10 per hour without apnoeas but periods of central hypoventilation mainly during rapid eye movement (REM) sleep. OSA appears to be more common in older patients with spinal cord injury than in the general population. Possible relevant factors include patient selection, reduced ventilatory function secondary to spinal cord damage, sleep posture and medication.

Adult↗
PubMed1992

Neck circumference and other clinical features in the diagnosis of the obstructive sleep apnoea syndrome.

BACKGROUND: Neck circumference has been suggested to be more predictive of obstructive sleep apnoea than general obesity, but the statistical validity of this conclusion has been questioned. Combining neck circumference with other signs and symptoms may allow the clinical diagnosis or exclusion of sleep apnoea to be made with reasonable confidence. This study examines these issues. METHODS: One hundred and fifty patients referred to a sleep clinic for investigation of sleep related breathing disorders completed a questionnaire covering daytime sleepiness, snoring, driving, and nasal disease. Body mass index and neck circumference corrected for height were measured and obstructive sleep apnoea severity was quantified as number of dips in arterial oxygen saturation (SaO2) of more than 4% per hour of polysomnography. Multiple linear regression was used retrospectively to identify independent predictors of SaO2 dip rate, and the model derived was then prospectively tested in a further 85 subjects. RESULTS: The retrospective analysis showed that the question "Do you fall asleep during the day, particularly when not busy?" was the best questionnaire predictor of variance in the SaO2 dip rate (r2 = 0.13); no other question improved this correlation. This analysis also showed that neither body mass index nor any of the questionnaire variables improved the amount of variance explained by height corrected neck circumference alone (r2 = 0.35). A statistically similar prospective analysis confirmed this relationship (r2 = 0.38). CONCLUSIONS: Prospective study of these patients referred to a sleep clinic with symptoms suggesting sleep apnoea shows that neck circumference corrected for height is more useful as a predictor of obstructive sleep apnoea than general obesity. None of the questionnaire variables examined add to its predictive power, but alone it is inadequate to avoid the need for sleep studies to diagnose this disease.

Adult↗
PubMed1992

An artifact induced by negative pressure ventilation.

This report draws attention to an artifact that influences the qualitative information gained from respiratory inductance plethysmography during negative pressure ventilation with a cuirass. This artifact may prevent identification of upper airway obstruction, a manageable complication of this mode of ventilation.

Artifacts↗
PubMed1992

The acute effects of continuous positive airway pressure and oxygen administration on blood pressure during obstructive sleep apnea.

We have measured blood pressure continuously with a digital artery blood pressure monitor in eight patients with severe obstructive sleep apnea (OSA) during 30 min each of wakefulness, OSA, OSA with added oxygen to keep saturation above 96 percent at all times (OSA+O2), and nasal continuous positive airway pressure (CPAP) therapy. Mean blood pressures were not different between wakefulness, OSA, OSA+O2, and CPAP, although the variability in blood pressure was significantly greater during OSA and OSA+O2 than during wakefulness and CPAP. The addition of oxygen did not attenuate the variability in blood pressure. Using multiple linear regression modeling to further dissect out the principal variables determining the postapneic blood pressure rise, we found that only apnea length (r2 = 0.28, p less than 0.0001) and pulse rate changes (r2 = 0.15, p less than 0.0001) remained significantly related to SBPmax, while hypoxemia did not. We found the same trends in the other variables SBPten, DBPmax, and DBPten. Hypoxemia made a small contribution to the size of DBPmax, although this was small by comparison with apnea length. We conclude that CPAP treatment of OSA does not lower mean blood pressure acutely, although it significantly reduces the large oscillations in blood pressure seen in patients with untreated OSA. The rise in blood pressure following each apnea is not primarily due to arterial desaturation but is related to apnea length and may be caused by increased sympathetic activity secondary to arousal.

Blood Pressure↗
PubMed1991

Self reported snoring and daytime sleepiness in men aged 35-65 years.

BACKGROUND: It has been suggested that snoring alone, without conventional sleep apnoea or hypopnoea, may disrupt sleep and produce substantial daytime hypersomnolence. This study addresses this potential relationship. METHOD: Eight hundred and fifty men, aged 35-65 years, drawn from one general practice were visited at home and asked a range of questions potentially related to sleepiness, snoring, and sleep apnoea; these included inquiries about alcohol and cigarette consumption, nasal stuffiness, shift work, hypnotic or other drug use, and medical diagnoses. In addition, measurements of height, weight, and overnight arterial oxygen saturation were made. The relation between snoring and sleepiness, with allowance made for potentially confounding variables, including sleep apnoea, was assessed by multiple logistic regression. RESULTS: Positive answers to all questions about sleepiness were correlated significantly with self reported snoring. After potentially confounding variables and any sleep apnoea had been controlled for, positive answers to four questions about inappropriate drowsiness or sleepiness were independently related to snoring. For example, the odds ratio of admitting to "having almost had two or more car accidents while driving due to sleepiness" was 5.8 (95% confidence intervals: 2.7-12.5) in an "often" snorer. CONCLUSIONS: Although epidemiological associations such as this do not prove a causal relation, the study suggests that snoring (without classical sleep apnoea) may sometimes reduce sleep quality sufficiently to produce substantial daytime drowsiness.

Adult↗
PubMed1991

Predictors and prevalence of obstructive sleep apnoea and snoring in 1001 middle aged men.

One thousand and one men, aged 35-65 years, were identified from the age-sex register of one group general practice. Over four years 900 men were visited at home and asked questions about symptoms potentially related to sleep apnoea and snoring. Height, weight, neck circumference, resting arterial oxygen saturation (SaO2), and spirometric values were also determined. All night oximetry was then performed at home and the tracing analysed for the number of dips in SaO2 of more than 4%. Subjects with more than five dips of 4% SaO2 or more per hour were invited for sleep laboratory polysomnography. Seventeen per cent of the men admitted to snoring "often." Multiple linear regression techniques identified and ranked neck circumference (r2 = 7.2%), cigarette consumption (r2 = 3.4%), and nasal stuffiness (r2 = 2%) as the only significant independent predictors of snoring. Together these account for at least a sixfold variation in the likelihood of being an "often" snorer. Forty six subjects (5%) had greater than 4% SaO2 dip rates of over five an hour and 31 of these had full sleep studies. Three subjects had clinically obvious and severe symptomatic obstructive sleep apnoea, giving a prevalence of three per 1001 men (0.3%; 95% confidence interval 0.07-0.9%). Eighteen men had obstructive sleep apnoea only when supine and in 10 the cause of the SaO2 dipping on the original home tracing was not elucidated. The greater than 4% SaO2 dip rates correlated with the history of snoring. Multiple linear regression techniques identified and ranked neck circumference (r2 = 7.9%), alcohol consumption (r2 = 3.7%), age (r2 = 1%) and obesity (r2 = 1%) as the only significant independent predictors of the rate of overnight hypoxic dipping. This study shows that snoring in this randomly selected population correlates best with neck size, smoking, and nasal stuffiness. Obstructive sleep apnoea, defined by nocturnal hypoxaemia, correlates best with neck size and alcohol, and less so with age and general obesity.

Adult↗