1. Obstructive sleep apnoea and its variants often provoke hundreds of short arousals that lead to the most important symptom, disabling hypersomnolence. The measurement of sleep in these conditions requires the documentation of these short arousals and this is conventionally done by manual inspection of the sleeping EEG, a laborious procedure. 2. Other markers of 'arousal', that are easier to measure and document, include several cardiovascular signals that change as part of the orienting reflex: pulse rate rise, blood pressure rise, skin vasoconstriction, for example. 3. Pulse transit time (measured as the interval from the ECG R-wave until the arrival of the pulse pressure wave at the periphery, about 250 ms) varies inversely with blood pressure and provides a beat-to-beat estimation of blood pressure changes. 4. In eight normal subjects we have assessed the relationship between transient EEG arousals of different length (provoked by external stimuli) and changes in both pulse transit time and heart rate. 5. Significant falls in pulse transit time occurred in response to external stimuli [15.1 (SEM 1.4) ms], indicating a rise in blood pressure, and were significant even when there was no discernible change in the EEG [9.9 (SEM 2.6) ms]. Significant changes in heart rate also occurred [10.3 (SEM 1.2) beats/min], but were slightly less sensitive than changes in pulse transit time. 6. Changes in pulse transit time (and to a lesser extent pulse rate) are sensitive markers of EEG arousal. As such they should be useful to include when monitoring sleep and its disorders, particularly since pulse transit time recorders can easily be made portable for home use.
Objective-To assess whether recording of ambulatory blood pressure
Nasal continuous positive airway pressure Background -Manual titration of nasal (NCPAP) is the most effective therapy for continuous positive airway pressure obstructive sleep apnoea (OSA). Patients are (NCPAP) treatment for obstructive sleep usually admitted to hospital overnight to start apnoea (OSA) is time consuming and treatment. During monitored sleep the lowest expensive. There are now "intelligent" pressure that is required to abolish the apnoeas NCPAP machines that try to find the ideal and arousals is established by manually inpressure for a patient by monitoring a creasing and lowering the airway pressure and combination of apnoeas, hypopnoeas, in-watching the effects on airflow, snoring, arterial spiratory flow limitation, and snoring. Al-oxygenation, and some measure of sleep though these machines usually find similar fragmentation such as movement or electropressures to skilled technicians, it is not encephalographic (EEG) disturbance. This is clear if their use in the sleep laboratory usually done over part or all of the night so influences subsequent acceptance by that periods requiring the highest pressures, patients. This study addresses this ques-such as the supine posture and rapid eye movetion. ment (REM) sleep, are included in the titration Methods -One hundred and twenty two period. However, it is labour intensive, time patients undergoing a trial of NCPAP were consuming, and expensive. When it was randomly allocated to either manual or thought that sleep monitoring with EEG was automatic (Horizon, DeVilbiss) titration necessary during NCPAP titration, a technician of pressure during their first night on was required to tend to the equipment anyway. NCPAP in a hospital sleep laboratory. However, in a study that assessed the adequacy The primary outcome (available on 112 of respiratory variables alone (airflow, chest patients) was the acceptance of NCPAP or wall movements, oximetry, and snoring) it was otherwise six weeks following the initial established that EEG monitoring during CPAP titration night. Baseline indicators of se-titration was not required, 1 so an automatic verity were compared between the groups, NCPAP machine capable of finding the optimal as were the pressures selected and the subpressure using feedback signals such as airflow sequent improvement in the sleepiness of and snoring could mean a substantial saving in the patients.technician time. Such a system might also track Results -The initial severity of OSA was the required pressure more assiduously than not significantly different in the two groups is usually possible manually, and hence the and the mean (SD) NCPAP pressures were pressure on which the patient is discharged similar (manual 8.7 (2.5) cm H 2 O, autohome might be more accurately prescribed. matic 8. (2.1) cm H O). The percentageSuch NCPAP machines are now available. of patients successfully established on They use a variety of signals to assess when to CPAP at six weeks was 64% and 73% for raise or lower their pressure, such as airflow or the manu...
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.
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