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Biomedical subjects

J R Stradling

Publications and source records attributed to J R Stradling.

At least 55 records · Page 3Linked to original sources
PubMed1998

Value of beat-to-beat blood pressure changes, detected by pulse transit time, in the management of the obstructive sleep apnoea/hypopnoea syndrome.

Two important aspects of a respiratory sleep study are a measure of inspiratory effort and an estimate of the number of arousals. These can be derived from an indirect estimate of beat-to-beat blood pressure (BP), pulse transit time (PTT). This study investigated the reproducibility of inspiratory BP falls (reflecting inspiratory effort), and BP arousals derived from PTT, and the contribution they could make to the management of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS). Overnight PTT was recorded at home in 40 patients being investigated for OSAHS, and a second PTT recording was made in the sleep laboratory with full polysomnography. Patients were divided into three groups according to the severity of their sleep disorder, and a third PTT recording was made at home in 13 patients subsequently established on nasal continuous positive airway pressure (CPAP). The reproducibility between the home and laboratory studies was reasonable (r=0.87 for inspiratory BP falls, r=0.81 for BP arousals). Both derivatives showed a clear progression through the three patient groups, which returned to normal on treatment. The differences between the groups were significant (p<0.001 for inspiratory BP falls, p=0.0014 for BP arousals). Receiver operator characteristic curves, used to compare polysomnography variables and PTT variables, confirmed that the PTT variables were as good as apnoea-hypopnoea index (AHI), >4% arterial oxygen saturation dip rate and electroencephalography micro-arousals at dividing patients into two groups, either requiring nasal CPAP or not requiring CPAP. Pulse transit time can provide a noninvasive estimate of inspiratory effort and a measure of arousals that together document disease severity and response to treatment and may be useful in managing obstructive sleep apnoea/hypopnoea syndrome.

Adult↗
PubMed1997

What is an arousal and how should it be quantified?

Pathologically severe daytime sleepiness is one of the main symptoms seen in a respiratory sleep clinic and is due to repeated arousal from sleep. Which types of arousal are most important in causing this is uncertain and most studies have only found loose relationships between indices of arousal frequency and the severity of the ensuing daytime sleepiness. Recent attempts to improve these disappointing correlations have concentrated on detecting more minor arousal events through the use of novel EEG signal analysis techniques and non-EEG based signals such as blood pressure and heart rate. To date there are no good data sets which allow the relative merits of these various techniques to be compared and it is unclear whether these efforts to increase the sensitivity of arousal detection will lead to improvements in the clinical usefulness of sleep fragmentation scoring. Studies which relate both the traditional indices of sleep fragmentation and the newer methodologies to clinically relevant reference standards (such as measured excessive daytime sleepiness) are needed to clarify these issues.

Journal Article↗
PubMed1997

A behavioural test to assess daytime sleepiness in obstructive sleep apnoea.

Daytime sleepiness is an important symptom of obstructive sleep apnoea syndrome (OSAS). The standard tests for its objective quantification use EEG recordings, and are time consuming and expensive, which makes them difficult to use for large studies. This study assesses the ability of a simple test of sustained 'wakefulness' to discriminate the excessive somnolence of severe symptomatic obstructive sleep apnoea from normality, and compares its results to the traditional EEG based Maintenance of Wakefulness Test (MWT). Ten subjects (7M 3F) with severe sleep apnoea (> 4% SaO2 dip rate median 32.7 (90% central range 9.7-65.6)) and symptoms of daytime sleepiness, (Epworth Sleepiness Score (ESS)17(10-24)) and 10 normal subjects (4M 6F, ESS 3.5(1-8)) were studied. The MWT and the behavioural test (Oxford SLEep Resistance test - OSLER test) were performed on each subject in random order on 2 separate days. The protocol for both tests was the same with 4 X 40 min sleep resistance challenges throughout the day while sound isolated in a darkened room. During the OSLER test subjects were asked to press a switch in response to a light emitting diode (LED), which was lit for 1 s in every three. Both the switch and the light were connected to a computer that stored both the number of times the light was illuminated and whether a correct response was made. The OSLER test discriminated the normal subjects from the sleep apnoea group (mean sleep latency (min) normal group 39.8, OSA group 10.5) as well as the traditional MWT (normal group 38.1 OSA group 7.3) and was much simpler to administer. This test has the advantage that sleep onset is defined objectively and automatically as a failure to respond to the light, rather than from EEG interpretation, which is inevitable partly subjective. This technique may provide a simple and robust method of objectively quantifying daytime sleepiness for large studies.

Adult↗
PubMed1997

Automatic nasal continuous positive airway pressure titration in the laboratory: patient outcomes.

BACKGROUND: Manual titration of nasal continuous positive airway pressure (NCPAP) treatment for obstructive sleep apnoea (OSA) is time consuming and expensive. There are now "intelligent" NCPAP machines that try to find the ideal pressure for a patient by monitoring a combination of apnoeas, hypopnoeas, inspiratory flow limitation, and snoring. Although these machines usually find similar pressures to skilled technicians, it is not clear if their use in the sleep laboratory influences subsequent acceptance by patients. This study addresses this question. METHODS: One hundred and twenty two patients undergoing a trial of NCPAP were randomly allocated to either manual or automatic (Horizon, DeVilbiss) titration of pressure during their first night on NCPAP in a hospital sleep laboratory. The primary outcome (available on 112 patients) was the acceptance of NCPAP or otherwise six weeks following the initial titration night. Baseline indicators of severity were compared between the groups, as were the pressures selected and the subsequent improvement in the sleepiness of the patients. RESULTS: The initial severity of OSA was not significantly different in the two groups and the mean (SD) NCPAP pressures were similar (manual 8.7 (2.5) cm H2O, automatic 8.2 (2.1) cm H2O). The percentage of patients successfully established on CPAP at six weeks was 64% and 73% for the manual and automatic groups, respectively; 13% and 2%, respectively, in the manual and automatic groups had given up completely (p < 0.05), and there were about equal numbers (23% versus 25%) in the two groups who were still undecided. CONCLUSIONS: The substitution of automatic NCPAP titration for manual titration during the first night of NCPAP in patients with OSA does not reduce the number accepting the treatment at six weeks and may slightly improve it. This has important cost saving potential.

Humans↗
PubMed1996

Sleep disordered breathing: effects of adenotonsillectomy on behaviour and psychological functioning.

UNLABELLED: Children on the adenotonsillectomy waiting list aged 6 years or more were screened by questionnaire and overnight sleep monitoring to identify 12 with a moderate sleep and breathing disorder (SBD) group. They were matched by age and sex with 11 children who had a similar history of snoring and sleep disturbance but without an obvious sleep and breathing problem when monitored (snorer group) and also with a group of ten children most of whom were refered for an unrelated surgical procedure (control group). All children were studied before and 3-6 months after surgery. Pre-operatively the SBD and snorer groups both had significantly more restless sleep than the control group. The SBD group also had significantly more (> 4%) dips in oxygen saturation than the other two groups. After surgery there were no longer any significant differences between the three groups. After adenotonsillectomy the SBD group showed a significant reduction in aggression, inattention and hyperactivity on the parent Conners scale, and an improvement in vigilance on the Continuous Performance Test. The snorer group also improved showing less hyperactive behaviour than pre-operatively and better vigilance. The control groups's behaviour and performance did not change significantly. There were no significant changes in the performance of the Matching Familiar Figures Test in any of the groups. CONCLUSION: Relief of mild to moderate sleep and breathing disorders in children is associated with improved behaviour and functioning. We confirm previous work which suggests that the relation between sleep disordered breathing and daytime problems in children is a causal one.

Adenoidectomy↗
PubMed1996

Is it necessary to record sleep?

The severe limitations of conventional sleep staging during sleep apnea are now understood. Microarousals are likely to be the dominant cause of symptoms in sleep apnea, but it has been extremely difficult to quantify them in a way that will predict daytime sleepiness or poor vigilance any better than respiratory indices. It is clear that not all apneas are equal on sleep, differences in the degree of arousal required to end an apnea and open the pharynx may help to explain why some individuals with apnea-plus-hypopnea indices (AHIs) of 15 may be symptomless, whereas others are severely disabled. Use of newer techniques to measure arousals, both cortical and autonomic, may produce a better understanding of how to measure sleep.

Arousal↗
PubMed1996

Effect of short term graded withdrawal of nasal continuous positive airway pressure on systemic blood pressure in patients with obstructive sleep apnoea.

It is debated whether obstructive sleep apnoea (OSA) is a significant independent risk factor for sustained hypertension or cardiovascular morbidity and mortality. In an attempt to avoid the problem of confounding variables we have investigated whether withdrawing nasal continuous positive airway pressure (NCPAP) from patients with OSA for different proportions of the night leads to a subsequent rise in their morning blood pressures. Six patients with treated OSA had their NCPAP automatically varied between 3 cms H2O and a therapeutic pressure over 5 successive nights. The proportion of therapeutic NCPAP given was kept constant over the 5 nights and blood pressure measured the morning after the 5th night. Each patient had 5 different levels of sleep disruption, from no therapeutic NCPAP at all, through to 100% NCPAP. The nocturnal consequences of these different proportions of NCPAP were quantified both by oximetry and by a new EEG analysis that provides an objective estimate of the periodicity (fluctuations in the EEG depth) of the time course seen in patients with OSA. Increasing degrees of nocturnal hypoxic dipping and EEG periodicity were positively correlated with the subsequent morning systolic and diastolic blood pressures (p < 0.02). About 20% of the variance in systolic and diastolic blood pressure could be accounted for by the amount of either hypoxic dipping or EEG periodicity. The results of this study suggest that acute changes in awake blood pressure can be caused by sleep apnoea. It agrees with other data suggesting that OSA can have an independent influence on morning BP, but that this effect may have worn off by the afternoon and evening. Some of the discrepancies between the numerous studies in this area may be due to the timing of blood pressure measurements.

Aged↗
PubMed1996

New approaches to monitoring sleep-related breathing disorders.

Conventional approaches to the analysis of sleep and sleep apnea do not describe all of the critical events that result from upper airway narrowing during sleep. The hypersomnolence that drives treatment is mainly due to microarousals, but these are poorly documented with conventional epoch-based sleep staging. The counting of apneas and hypopneas also fails to document other equally important events, such as the arousals due to increased respiratory effort in response to partial upper airway narrowing that may not cause significant hypopnea, hypoxemia, or even snoring. Modifications of conventional polysomnography, such as microarousal detection and analysis of the ribcage/abdominal paradox, may be an improvement. However, no system has been shown to be better than any other at identifying the critical events that produce symptoms of sleep-related breathing disorders, and thus be likely to respond to effective treatment. The time is right to explore innovative ways to characterize sleep-related breathing disorders, such as those derived from the cardiovascular change related to upper airway obstruction and arousal, without the shackles of conventional polysomnography. New monitoring techniques need to identify patients with events that will respond to treatment, not mimic the flawed gold standard of polysomnography.

Arousal↗
PubMed1995

Use of the Epworth Sleepiness Scale to demonstrate response to treatment with nasal continuous positive airways pressure in patients with obstructive sleep apnoea.

The Epworth Sleepiness Scale (ESS) was used to measure the degree of daytime sleepiness in two groups of patients with obstructive sleep apnoea (OSA), before and after treatment with nasal continuous positive airways pressure (CPAP). One group (50 patients) were assessed after 2 months CPAP treatment after which the mean ESS fell from 16.4 [standard error of mean (SEM) 0.52] to 7.0 (SEM 0.56). A second group (25 patients) were assessed after 1 yr of treatment: a similar fall in mean ESS was seen from 15.2 (SEM 1.13) before treatment to 6.0 (SEM 0.72). These results imply that the ESS can be used clinically to demonstrate the response of daytime sleepiness in OSA to treatment with CPAP, and that the fall in ESS seen after 2 months is sustained after 1 yr of treatment. It is also possible that this approach could be used to monitor the progress of treatment with CPAP.

Female↗
PubMed1995

Short- and long-term outcomes of uvulopalatopharyngoplasty for snoring.

Uvulopalatopharyngoplasty is a well established and highly successful operation in the treatment of snoring. However, most published data are based on relatively short-term follow-up results. Anecdotal cases of late recurrence of snoring after an initially successful surgical result have been reported but few formal studies have been performed to determine the true magnitude of this problem. We compared the short-term and long-term results on our patients and found the late recurrence rate after a minimum follow-up period of 12 months (range: 12-84 months, mean 31.3 months) to be in the region of 13%. The risk of recurrence was directly related to the body mass index.

Adult↗
PubMed1995

Effects of short term high frequency negative pressure ventilation on gas exchange using the Hayek oscillator in normal subjects.

BACKGROUND: The Hayek oscillator is a negative pressure cuirass that can operate at a range of frequencies to provide ventilation, and is a technique which could potentially be used on a general ward. This study examined the effect of different frequencies and different ranges of inspiratory and expiratory pressures on gas exchange, respiratory rate, and blood pressure in normal subjects. METHODS: Eight normal subjects received five minute periods of ventilation using the Hayek oscillator at five different frequencies, and a combination of two spans of inspiratory and expiratory pressures and two mean chamber pressures. A "sham" or control period was also performed at each frequency. Measurements were made of changes in gas exchange, spontaneous respiratory rate, and blood pressure before and after ventilation. RESULTS: There was significant intersubject variation in all results, independent of their height and weight. "Sham" settings acted as true controls in terms of gas exchange, but produced a fall in respiratory rate at 30 oscillations/min. The lower oscillatory frequencies of 30 and 60 oscillations/min produced the greatest increase in oxygenation, decrease in end tidal carbon dioxide pressure, and decrease in spontaneous respiratory rate. These effects were most significant at higher spans of pressure and were different from "sham" settings. No adverse effects were observed on blood pressure. CONCLUSIONS: The Hayek oscillator can provide assisted ventilation for short periods in normal conscious subjects with no adverse side effects on blood pressure. Maximal changes in gas exchange and a significant reduction in the spontaneous respiratory rate are seen when a combination of lower frequencies (30 and 60 oscillations/min) and higher spans of pressure are used.

Adult↗
PubMed1995

Use of pulse transit time as a measure of inspiratory effort in patients with obstructive sleep apnoea.

Pulse transit time (PTT) is the time taken for the arterial pulse pressure wave to travel from the aortic valve to a peripheral site. For convenience, it is usually measured from the R wave on the electrocardiogram to the pulse wave arrival at the finger. Pulse transit time is inversely proportional to blood pressure, and the falls in blood pressure which occur with inspiration (pulsus paradoxus) correspond to rises (lengthening) in pulse transit time. In awake normal subjects, the size of these inspiratory rises in pulse transit time correlate well with the degree of inspiratory effort. The aim of this study was to investigate whether inspiratory rises in pulse transit time could provide a quantitative measure of inspiratory effort in patients with obstructive sleep apnoea. Eight patients with obstructive sleep apnoea, attending the laboratory for institution of nasal continuous positive airway pressure, took part in the study. Once asleep, airway pressure was varied between optimal treatment level and minimum pressure, to produce a range of inspiratory efforts whilst continuous recordings of oesophageal pressure and pulse transit time were made. There was an excellent correlation between the size of the swings in oesophageal pressure and the size of the swings in pulse transit time (mean r = 0.94). Pulse transit time may, therefore, provide a clinically useful noninvasive and quantitative measure of inspiratory effort in patients with sleep-related breathing disorders.

Adult↗
PubMed1995

Epidemiology of snoring and its consequences.

Much has been written about snoring and its affects on health, in particular its possible influence on cardiovascular disease. However, there are many assumptions made when linking the report of snoring to any consequences such as hypertension, heart disease or stroke. In particular it is not clear how snoring might influence the cardiovascular system, whether subjective reports of snoring are accurate, and snoring might only be acting as a marker for some common risk factor such as upper body obesity; a particular risk factor for cardiovascular disease, and through neck circumference, snoring. There is much better evidence that snoring is an important cause of sleepiness, even in the absence of conventional sleep apnoea.

Cardiovascular Diseases↗