Biomedical subjects

R N Kingshott

Publications and source records attributed to R N Kingshott.

14 recordsLinked to original sources

PubMed2001

Association of airway obstruction, sleep, and phasic abdominal muscle activity after upper abdominal surgery.

We recorded nasal gas flow, sleep stage, and abdominal muscle EMG pattern in 11 patients throughout the night after abdominal surgery, to examine the association between phasic activity of the abdominal muscles, sleep stage, and flow disturbance. We used a miniaturized data logging system, and obtained satisfactory records in eight patients. The data were divided into 30-s epochs. Each epoch was classified as either awake or asleep. The epochs were also classified for the presence of phasic activity in the external oblique abdominal muscle, and for evidence of airway obstruction. Association between these features was tested by a quasi likelihood log linear model. Values given are median (quartiles) for the eight subjects. Sleep occurred for 62 (46-69)% of the study time. During sleep, inspiratory flow was normal for 69 (48-81)% of the time, whereas during wakefulness, the flow pattern was normal for 51 (28-77)% of the time. Phasic activity was present 16 (12-25)% of the time during sleep and 24 (19-37)% of the time during wakefulness (P<0.001). In the awake state, when breathing was normal, phasic activity was present 16 (11-30)% of the time. When breathing was obstructed, phasic activity was present 38 (25-44)% of the time (P<0.001). These surprising findings suggest that sleep may be seriously disturbed by airway obstruction, so that a stable sleep state is not reached. We could not confirm previous findings that disturbed breathing in post-operative patients only occurs during sleep.

Abdomen↗

PubMed2001

Randomized, double-blind, placebo-controlled crossover trial of modafinil in the treatment of residual excessive daytime sleepiness in the sleep apnea/hypopnea syndrome.

Some patients with the sleep apnea/hypopnea syndrome (SAHS) remain subjectively and objectively sleepy despite using effective continuous positive airway pressure (CPAP) therapy. The aim of this single center study was to determine the efficacy and safety of the novel wake-promoting medication modafinil in the treatment of CPAP-resistant daytime sleepiness. Thirty sleep apneics receiving effective CPAP therapy (objective use, 6.5 +/- 1.1 h/night) received daily single doses of 400 mg modafinil or placebo for 2 wk in a double-blind randomized crossover design. Outcome measures were assessed at baseline and at the end of both 2-wk treatment periods. Treatment periods were separated by a 1-wk washout. Modafinil had no effect on sleepiness as measured by the Epworth Sleepiness Scale or the Multiple Sleep Latency Test (p > 0.1); however, significant improvements in alertness were found with the Maintenance of Wakefulness Test (modafinil 18.3 +/- 3.9 min; placebo, 16.6 +/- 5.0 min; p < 0.02). No significant treatment-related improvements in cognitive performance or quality of life were found with modafinil (all p > 0.05). There was a significant reduction in CPAP use on modafinil compared to placebo (6.3 +/- 1 h/ night; 6.5 +/- 1, p = 0.03). This study suggests that modafinil may improve some aspects of alertness in patients with SAHS who remain sleepy during CPAP therapy, but further studies are required to assess the significance of the reduction in CPAP use.

Administration, Oral↗

PubMed2000

The effect of in-laboratory polysomnography on sleep and objective daytime sleepiness.

MSLT guidelines recommend performing MSLTs following polysomnography (PSG) to document the preceding night's sleep. We tested the hypothesis that patients are objectively sleepier after in-laboratory full diagnostic PSG than after a sleep recording at home. Sixteen patients with the sleep apnea/hypopnea syndrome (SAHS; AHI 35+/-SD 28 per hour slept) were recruited into a randomized crossover study. To monitor sleep with minimal disruption at home, only sleep was recorded on 2 consecutive nights, the first for acclimatization. The laboratory limb followed standard PSG. Both study nights were followed next day by MSLT and MWT. There were no differences in MSLT (12.0 SD 5.1 home, 11.6+/-4.7 min laboratory; p=0.7), MWT (32.7+/-8.7, 31.6+/-9.3 min; p=0.6) or total sleep time (362+/-53, 343+/-51 min; p=0.15) between home and laboratory limbs. However, on the home night, fewer microarousals (31+/-14, 54+/-25/hr slept; p<0.0001) and less % wake (15+/-10, 24+/-11; p=0.006) were found. On the home study night, patients had greater % REM sleep, slow-wave sleep and sleep efficiency (all p<0.009). This study does not support the hypothesis that patients are sleepier after laboratory PSG compared to home study night. However, the improved sleep at home raises the question whether laboratory-based polysomnography is always required prior to MSLT/MWT testing or whether less obtrusive monitoring of sleep duration at home would sometimes suffice.

Adult↗

PubMed2000

Cognitive function in the sleep apnea/hypopnea syndrome (SAHS).

The magnitude, determinants and reversibility of cognitive deficits associated with the sleep apnea/hypopnea syndrome (SAHS) are of clinical and research interest. A quantitative overview of impairment effect sizes (ESs) from case-control studies of cognitive performance in SAHS suggests that deficits broadly worsen with disease severity, with large average values for attentional (ES approximately 1.0 SD units) and executive (ES approximately 0.9 SD units) cognitive scores, and moderate values for memory-related (ES approximately 0.6 SD units) performance scores. A study of determinants of cognitive outcomes conducted in 150 patients with SAHS (AHI 5+ and > or =2 symptoms) showed significant but weak associations between a cognitive 'intellectual ability' component score (CS) and both AHI (r=-0.14) and minimum oxygen saturation (r = 0.15), linking increasing disease severity with poorer performance. A somewhat stronger correlation between a cognitive 'response slowing' CS and a 'wakefulness' CS was observed (r=-0.34). That sleepiness as well as hypoxemia might contribute to cognitive deficit has also been suggested by experimental sleep fragmentation in normals, producing small to moderate impairments (average ES approximately 0.3 SD units) in attention-biased scores. The reversibility of attentional cognitive deficits has been investigated through a meta-analysis of randomized placebo-controlled crossover studies of CPAP treatment, involving 98 SAHS patients (AHI 5+ and > or =2 symptoms). While cognitive outcomes showed at least trends towards better performance on CPAP than on placebo (p< or =0.1), the ESs of cognitive enhancements following CPAP were small (average ES approximately 0.2 SD units). This may be due either to the relatively mild study population, suboptimal CPAP use or to an irreversible component in cognitive impairment in SAHS.

Case-Control Studies↗

PubMed2000

The effect of sleep fragmentation on cognitive processing using computerized topographic brain mapping.

Topographic brain mapping of evoked potentials can be used to localize abnormalities of cortical function. We evaluated the effect of sleep fragmentation on brain function by measuring the visual P300 waveform using brain mapping. Eight normal subjects (Epworth Score +/- SD: 5 +/- 3) underwent tone-induced sleep fragmentation and undisturbed study nights in a randomized cross-over design. Study nights were followed by topographic brain mapping using a visual information processing test and concurrent event-related potentials. Experimental sleep fragmentation did not significantly increase objective daytime sleepiness or lower cognitive performance on a battery of cognitive function tests (all P > or = 0.1). There were no significant topographical delays in P300 latencies with sleep fragmentation (all P > 0.15). However, at sites Fz, F4, T3, C3, Cz and C4 the P300 amplitudes were reduced significantly after sleep fragmentation (all P < 0.05). A reduction in P300 amplitude has previously been interpreted as a decrease in attention. These reductions in P300 amplitudes with sleep fragmentation in frontal, central and temporal brain areas suggest that sleep fragmentation may cause a broad decrease in attention. Sleep fragmentation did not delay P300 latencies in any brain area, and so does not explain the delay in P300 latencies reported in sleep apnoeics.

Adult↗

PubMed2000

Predictors of improvements in daytime function outcomes with CPAP therapy.

Continuous positive airway pressure (CPAP) therapy improves daytime function in the sleep apnea/ hypopnea syndrome (SAHS) but it is unclear which patients benefit and what factors predict this improvement. To test the hypothesis that brief arousals from sleep predict improvements in daytime functioning with CPAP therapy, we prospectively studied 62 patients with polysomnography-defined SAHS. Each underwent daytime function assessments at baseline and after 6 mo of CPAP therapy to measure objective sleepiness, psychological well-being, quality of life, and cognitive performance. The microarousal frequency and AHI were poor predictors of improvements in daytime function with CPAP. Measures of hypoxemia predicted improvements in the mean sleep latency on the maintenance of wakefulness test, SAHS symptoms, quality of life, and reaction time, but such correlations were weak or moderate only explaining between 7% and 22% of variance. Significant relationships were found between CPAP use and improvements in self-ratings of daytime function. Results suggest that standard polysomnographic baseline variables are poor predictors of the response to CPAP therapy.

Adult↗

PubMed2000

Frequency and significance of increased upper airway resistance during sleep.

Previous studies have shown that episodes of inspiratory flow limitation can be clinically important. We have challenged the hypothesis that patients with the "upper airway resistance syndrome" have more episodes of inspiratory flow limitation, associated with greater swings in pleural pressure and more arousals from sleep than normal subjects. We thus studied eight symptomatic patients with UARS (ESS > 10, AHI < 15) and eight matched asymptomatic subjects. All had overnight polysomnography with recording of pleural pressure and airflow derived from nasal pressure. Events scored visually using nasal pressure were termed flow limitation events and those using both signals "resistive events." The patients with UARS had no more episodes of flow limitation or resistive events than the controls. However, pleural pressure swings at resistive event termination were significantly more negative in the patient group (-15 [IQR 9-19]; -11 [8-12] cm H(2)O; p = 0.02) and the number of cortical arousals associated with resistive events was higher in the patients (median, 10 [5-15]; 3 [1-9]/h slept; p = 0.02). This study confirms that patients with UARS have periods of increased upper airway resistance associated with significant sleep fragmentation. However, resistive events are also common in normal subjects, although these are associated with less negative pleural pressure swings and fewer arousals. Thus, the clinical significance of resistive events needs to be interpreted with caution.

Adult↗

PubMed1999

Randomized placebo-controlled crossover trial of continuous positive airway pressure for mild sleep Apnea/Hypopnea syndrome.

The minimal disease severity at which patients with the sleep apnea/hypopnea syndrome (SAHS) gain benefit from treatment is not well characterized, although a pilot study of continuous positive airway pressure (CPAP) therapy showed daytime improvements in patients with 5 to 15 apneas + hypopneas per hour slept (AHI). We have thus performed a second, larger, randomized, placebo- controlled study in a prospective series of 34 patients (13 female) with mild SAHS (AHI 5 to 15) and daytime sleepiness. Patients spent 4 wk on CPAP treatment and 4 wk on an oral placebo, with randomization of treatment order, and daytime assessments on the last day of each treatment. Effective CPAP use averaged 2.8 +/- 2.1 h (mean +/- SD) per night. Compared with placebo, CPAP improved symptom score (p < 0.01), subjective (Epworth; p < 0.01) but not objective (maintenance of wakefulness test; p > 0.2) sleepiness, performances on 2 of 7 cognitive tasks (p < 0.02), depression score (p < 0.01), and five subscales of the SF-36 health/functional status questionnaire (p </= 0.03). Fourteen of 34 patients preferred CPAP. In 14 patients with AHI in the range 5 to 10, symptoms, cognitive function, psychological well-being and quality of life were improved. These results confirm benefits for daytime function after CPAP treatment for mild SAHS, but highlight unacceptability of CPAP in many such patients.

Adult↗

PubMed1999

Can intensive support improve continuous positive airway pressure use in patients with the sleep apnea/hypopnea syndrome?

Continuous positive airway pressure (CPAP) therapy is widely prescribed for patients with the sleep apnea/hypopnea syndrome (SAHS), but the use of CPAP for such patients is disappointingly low. We postulated that providing intensive educational programs and nursing support to SAHS patients might improve CPAP use and outcomes. We also examined the hypothesis that CPAP use would be greater among patients who had initiated their own referral than among those asked to seek help by a partner. We randomized 80 consecutive, new patients with SAHS to receive either usual support or additional nursing input including CPAP education at home and involving their partners, a 3-night trial of CPAP in our institution's sleep center, and additional home visits once they had begun CPAP. The primary outcome variable was objective CPAP use; symptoms, mood, and cognitive function were also assessed after 6 mo. CPAP use over 6 mo was greater (p = 0.003) among patients receiving intensive than among those receiving standard support (5.4 +/- 0.3 versus 3.9 +/- 0. 4 h/night [mean +/- SEM]), with greater improvements (p < 0.05) in SAHS symptoms, mood, and reaction time in the intensively supported group. CPAP use was greater (p = 0.002) among patients who initiated their own referrals. CPAP use and outcomes of therapy can be improved by provision of a nurse-led intensive CPAP education and support program. CPAP use is lower among patients whose partners ask them to seek treatment.

Affect↗

PubMed1998

Randomised placebo controlled trial of daytime function after continuous positive airway pressure (CPAP) therapy for the sleep apnoea/hypopnoea syndrome.

BACKGROUND: Patients with the sleep apnoea/hypopnoea syndrome (SAHS) report improved sleepiness, cognitive function, and psychological well being after continuous positive airway pressure (CPAP) therapy, and it is for these daytime features that CPAP is usually given. However, few randomised or controlled studies exist on the effects of CPAP on daytime function. METHODS: A prospective, randomised, single blind, placebo controlled, crossover trial of daytime function after CPAP was conducted in 23 patients with SAHS, all with > or = 15 apnoeas + hypopnoeas/hour and > or = 2 symptoms of SAHS. All patients spent four weeks on CPAP therapy and four weeks on oral placebo treatment, following randomisation to treatment order. With ethics committee approval, patients were told the placebo tablet might improve upper airway function. Average effective CPAP use was monitored using hidden time clocks. Assessments of objective and subjective sleepiness, symptoms, cognitive performance, and psychological well being were performed on the last day of each treatment and compared. RESULTS: Objective sleepiness measured by sleep onset latency on the multiple sleep latency test improved with CPAP (mean difference from placebo +2.4 min, 95% CI 0.8 to 4.0; p < 0.001) as did subjective sleepiness on the Epworth scale (mean difference -6, 95% CI -3 to -9; p = 0.001). Symptom total score also fell with CPAP (mean difference -1.6, 95% CI -2.2 to -1.0; p < 0.001). No determinants of these changes with active treatment were identified, and no significant enhancements to cognitive function or psychosocial well being were found in this small sample. CONCLUSIONS: These findings provide further evidence for clinically significant benefits to daytime function from CPAP.

Adult↗

PubMed1998

Does arousal frequency predict daytime function?

Patients with the sleep apnoea/hypopnoea syndrome (SAHS) have impaired daytime function with demonstrable sleepiness and impaired cognition. The hypothesis that brief arousals from sleep cause these daytime impairments was tested. One hundred and fifty patients with sleep disordered breathing were studied prospectively, comparing overnight polysomnography with daytime measures of objective sleepiness, psychological well-being and cognitive performance. Significant, but weak (r2<0.1), relationships were seen between several nocturnal measures (apnoea/hypopnoea index, arousals and desaturation variables) and daytime measures of quality of life, well-being, subjective sleepiness, symptoms and cognitive performance. The only significant relationship between nocturnal variables and objective sleepiness was a very weak correlation (r2<0.05) between the lowest oxygen saturation and mean maintenance of wakefulness test (MWT) result. The MWT was better correlated with daytime function than the multiple sleep latency test. This study shows a lack of strong relationships between conventional nocturnal measures and daytime function in patients with sleep disordered breathing.

Adolescent↗

PubMed1997

Microarousals in patients with sleep apnoea/hypopnoea syndrome.

Upper airway obstructions during sleep cause recurrent brief awakenings or microarousals. Standard criteria exist for sleep and respiratory event scoring, however, there are different definitions currently used to score microarousals. We therefore compared three definitions of microarousal (ranging from 1.5-3 s in duration) and one of awakening (>15 s). We examined their occurrence at the termination of apnoeas and hypopnoeas and their correlation with daytime sleepiness in patients with sleep apnoea/hypopnoea syndrome (SAHS). Sixty-three patients (aged 49, SD 10) had overnight polysomnography, multiple sleep latency tests (MSLT) and Epworth Sleepiness Scales (ESS). There were significantly more microarousals by any definition than there were awakenings (P<0.001) and there were more 1.5 s than 3 s microarousals (P<0.001). Significantly more apnoeas and hypopnoeas were terminated by 1.5 s microarousals (83% and 81%) than by 3 s microarousals (75%) (all P<0.001). Apnoea/ hypopnoea index (AHI) correlated significantly with objective daytime sleepiness (rho=-0.30, P<0.01). There were weakly significant relationships between all three microarousal definitions (-0.24<rho<-0.22, 0.03<P<0.04) and objective daytime sleepiness. None of the arousal definitions correlated with Epworth Sleepiness Scales scores. These results suggest that although 1.5 s microarousals are found at the end of more respiratory events, relationships between 3 and 1.5 s definitions, and daytime sleepiness are similar. This indicates that any of the three microarousal definitions can be used for visual assessment of sleep fragmentation.

Arousal↗

PubMed1996

Ambulatory blood pressure on and off continuous positive airway pressure therapy for the sleep apnea/hypopnea syndrome: effects in "non-dippers".

Ambulatory blood pressure (BP) monitoring was performed in 13 patients with the sleep apnea/ hypopnea syndrome (SAHS) during a randomized, placebo controlled crossover trial of the effects of continuous positive airway pressure (CPAP) therapy. BP was monitored at half-hourly intervals for a 24-hour period both on CPAP and on an oral placebo, each given for a minimum of 3 weeks. Objective effective CPAP use averaged 4.3 hours per night. Weight and anti-hypertensive medications remained stable over the study period. Systolic, diastolic and mean arterial BP for 24-hour, daytime and nighttime periods were not significantly different on placebo compared to CPAP. Those patients with no significant overnight fall in BP on placebo ("non-dippers") showed a significant improvement in daytime mean arterial BP on CPAP (98 +/- 4 mm Hg) compared to placebo (102 +/- 4 mm Hg; p = 0.01). These findings, in a well-controlled trial, suggest that BP is not reduced by CPAP in a heterogeneous group of SAHS patients, but it may be selectively improved in those patients most at risk for cardiovascular morbidity and mortality.

Adult↗

PubMed1995

Self assessment of daytime sleepiness: patient versus partner.

BACKGROUND: Patients with the sleep apnoea/hypopnoea syndrome (SAHS) and their spouses often differ in their assessment of the patient's sleepiness. A study was therefore undertaken to investigate whether either the patient's or partner's rating on the Epworth sleepiness scale (ESS) was better related to illness severity. METHODS: Nocturnal variables (apnoeas+hypopnoeas/hour (AHI) and arousals/hour) and patient and partner ESS scores were compared in 103 new patients attending the sleep clinic. RESULTS: Mean patient and partner ESS scores were not different. In the whole population neither patient nor partner ESS variables correlated with AHI or arousal frequency. In the patients with SAHS (AHI > or = 15), partner ESS correlated weakly with AHI, but patient ESS did not. CONCLUSIONS: This study suggests that neither patient nor partner ESS ratings are strong predictors of SAHS severity.

Disorders of Excessive Somnolence↗