Biomedical subjects

T V Coy

Publications and source records attributed to T V Coy.

6 recordsLinked to original sources

PubMed1996

Sleep apnoea and sympathetic nervous system activity: a review.

A review was made of the literature relating sleep apnoea to sympathetic nervous system (SNS) activity, as inferred from catecholamine levels or muscle sympathetic nerve activity (MSNA). Twenty-four studies were located. Most studies reported an elevation of norepinephrine and MSNA, both during sleep and wakefulness among individuals with sleep apnoea. However, studies rarely controlled for known confounders of sympathetic activity, making the validity of the findings questionable.

Arousal↗

PubMed1996

The role of sleep-disordered breathing in essential hypertension.

In recent years there have been numerous reports addressing the relationship between sleep-disordered breathing (SDB) and hypertension (HTN). This study investigated the relationship between SDB and BP after controlling for age, gross obesity, and notably, antihypertensive medications. Sixty-seven men and women between 30 and 60 years of age and between 0.90 to 1.5 times ideal body weight were studied. SDB was assessed over two nights of polysomnographic monitoring, and BP was measured over repeated visits to the hospital. The results indicate that respiratory disturbance index (RDI) independently predicts diastolic BP (DBP), accounting for 15% of the variance in DBP (p=0.02). In subjects with severe levels of SDB (RDI >30), RDI uniquely accounted for 36% of the variance in DBP (p=0.003). Interestingly, SDB was not independently related to systolic BP. The physiologic mechanisms responsible for these findings are currently being explored.

Adult↗

PubMed1995

Beta 2-adrenergic receptor characteristics in sleep apnea patients.

This study examined the relationship between sleep apnea and beta 2-adrenergic receptor characteristics. Using standard polysomnography, individuals were classified as either apneic (n = 15) or mild to nonapneic (n = 15) according to their respiratory disturbance index (RDI). Subjects were similar in terms of sodium excretion and blood pressure. Apneic subjects showed a decrease in beta 2-adrenergic receptor sensitivity (p = 0.01) [as determined by isoproterenol-stimulated cyclic adenosine 5'-monophosphate (AMP) production in lymphocytes] and an increased binding affinity to the beta receptor antagonist [125I]iodopindolol (p < 0.001). beta receptor density was also diminished in apneics, but not significantly (p = 0.08). Forskolin-stimulated cyclic AMP was not significantly different between the groups, indicating a similarity in postreceptor Gs-adenylate cyclase activation. Across all subjects, RDI was negatively correlated with beta receptor sensitivity (r = -0.35, p = 0.05) and Kd (r = -0.54, p < 0.01) and positively correlated with systolic blood pressure (r = 0.37, p < 0.05). The findings indicate that sleep apnea is associated with a diminished beta 2-adrenergic receptor function but no change in postreceptor components and suggest a mechanism for the high comorbidity between sleep apnea and hypertension.

Adenosine Monophosphate↗

PubMed1994

A technique for improved blood sampling during sleep studies.

Research protocols often require that blood samples be drawn during sleep. This study compares the efficacy of obtaining nocturnal blood samples using a standard heparinized intravenous setup versus the same intravenous setup used in conjunction with a small chemical heating pad. The chemical heating pad significantly improved the number of blood samples obtained and the maintenance of intravenous patency. The use of a chemical heating pad is an economical way to resolve the frustration of lost blood samples while maintaining a reasonable environment to monitor sleep.

Adult↗

PubMed1993

The effect of blood pressure cuff inflation on sleep. A polysomnographic examination.

Ambulatory blood pressure monitors are being used increasingly to define blood pressure in contexts other than the doctor's office. With increasing interest in both effects of treatment on quality of life and chronobiology of hemodynamic regulation, such monitors have also been used to define blood pressure during sleep. Unfortunately, few investigators have scrutinized the effect of such recordings on sleep, as defined precisely with polysomnography. We studied a diverse group of 12 unmedicated individuals, measuring BP by cuff inflation every 60 min. The polysomnogram was then analyzed for periods of wakefulness and arousals from sleep. Cuff inflation was associated with increased arousals (P < .0001) and wakefulness (P < .0001). In addition, subjects recalled 58% of the cuff inflations. Effects of cuff inflation on a second night of recording indicated some habituation. Nocturnal BPs measured by such techniques are still valuable, but one must have some reservations that these measures accurately reflect BP during sleep.

Blood Pressure Monitors↗

PubMedDate not supplied

Evaluation of sleep disordered breathing with unattended recording: the Nightwatch System.

There is a need for studies to determine how new ambulatory systems compare to traditional polysomnography (PSG). Thirty-four subjects were recorded with the Nightwatch (NW) System (Heathdyne Inc.) at home and then recorded with PSG in the laboratory. NW records were scored automatically using the NW algorithm with manual editing. There were no significant differences in mean RDI, AI, number of apneas or hypopneas or oximetry varibles between the systems. Correlations of RDI on the Nightwatch system and laboratory nights were significant (r = 0.63). Every case of RDI > or = 10 on the PSG was also identified by Nightwatch. Specificity was lower on Nightwatch (66%); however, all three cases of false positives could be explained physiologically, i.e. by body position. Overall the NW system correlated well with traditional PSG for respiratory disturbance.

Algorithms↗