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PubMed2005

Decreased brain activation during a working memory task at rested baseline is associated with vulnerability to sleep deprivation.

STUDY OBJECTIVE: To examine whether differences in patterns of brain activation under baseline conditions relate to the differences in sleep-deprivation vulnerability. DESIGN: Using blood oxygenation level dependent (BOLD) functional magnetic resonance imaging, we scanned 33 healthy young men while they performed the Sternberg working memory task following a normal night of sleep and again following 30 hours of sleep deprivation. From this initial group, based on their Sternberg working memory task performance, we found 10 subjects resilient to sleep deprivation (sleep deprivation-resilient group) and then selected 10 age- and education-matched subjects vulnerable to sleep deprivation (sleep deprivation-vulnerable group). SETTING: Inpatient General Clinical Research Center and outpatient functional magnetic resonance imaging center. PATIENTS OR PARTICIPANTS: Data from 10 young men (mean age 27.8 +/- 1.7 years) in the sleep deprivation-resilient group and 10 young men (mean age 28.2 +/- 1.9 years) in the sleep deprivation-vulnerable group were included in the final analyses. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: We compared functional magnetic resonance imaging BOLD signal at rested baseline and sleep deprivation states in the 2 groups. As hypothesized, following sleep deprivation, both groups showed significant decreases in global brain activation compared to their rested group baseline. At rested baseline and in the sleep-deprivation state, the sleep deprivation-resilient group had significantly more brain activation than did the sleep deprivation-vulnerable group. There were also differences in functional circuits within and between groups in response to sleep deprivation. CONCLUSIONS: These preliminary data suggest that patterns of brain activation during the Sternberg working memory task at the rested baseline and the sleep-deprivation state, differ across individuals as a function of their sleep-deprivation vulnerability.

Adolescent↗
PubMed2002

Assessment of transient left ventricular dilatation on rest and exercise on Tc-99m tetrofosmin myocardial SPECT.

In myocardial perfusion imaging, multiple-vessel involvement of coronary artery disease (CAD) sometimes makes diagnosis difficult. Transient left ventricular (LV) dilatation on Tl-201 myocardial SPECT is a useful finding that enables the clinician to identify patients with multiple-vessel disease. The aim of this study was to confirm the utility of measuring transient LV dilatation for the detection of multiple-vessel CAD in exercise Tc-99m tetrofosmin myocardial SPECT. The participants were 55 CAD patients and 20 controls who underwent Tc-99m tetrofosmin myocardial SPECT exercise and resting imaging. During exercise, 370 MBq (10 mCi) Tc-99m tetrofosmin was injected. Exercise images were obtained 30 minutes after injection. At 210 minutes after injection, 740 MBq (20 mCi) Tc-99m tetrofosmin was administered intravenously. The rest SPECT images were acquired 30 minutes later. Thirty-six radii at every 10 degrees were generated from the center of short-axis images. An area surrounded by 36 maximal points of the myocardial Tc-99m tetrofosmin counts on each radius was calculated for exercise and rest images. The area surrounded by the 36 maximal points in the same slice of the exercise and rest images was assigned the variables A (Ex) and A(R), respectively. The transient dilatation index (TDI) of the left ventricle was calculated using the formula mean A (Ex)/A(R) in the apical, middle, and basal myocardial short-axis images. In the controls, the TDI was 0.970 +/- 0.021. In patients with CAD, the TDIs of one-vessel disease, two-vessel disease, and three-vessel disease were 1.034 +/- 0.032, 1.093 +/- 0.046, and 1.131 +/- 0.076, respectively. The TDIs were significantly greater in patients who had more occluded coronary arteries (P < 0.01). If the mean + 2SD of the TDI (1.012) in controls were assumed to be the normal upper limit, the sensitivity, specificity, and accuracy of this method in detecting two-vessel or three-vessel disease would be 91.4%, 76.9%, and 84%, respectively. The TDI is a useful index for evaluating subendocardial ischemia non-invasively and detecting multiple-vessel disease clinically.

Coronary Angiography↗
PubMedDate not supplied

Measurement of aortic and pulmonary flow with MRI at rest and during physical exercise.

PURPOSE: Our aim was to assess the feasibility of measuring great vessel flow during submaximal exercise using MR flow mapping. METHOD: In 16 healthy volunteers, MR measurements of great vessel flow were obtained at rest and during two levels of submaximal physical exercise using an MR-compatible bicycle ergometer. RESULTS: Great vessel flow showed good correlation at rest and during exercise (r = 0.9, p < 0.0005). Significant increase in heart rate was observed during exercise. Aortic flow volume increased from 64 +/- 13 ml/beat at rest to 71 +/- 11 ml/beat at 50 W (p < 0.0005) to 79 +/- 13 ml/beat at 100 W (p < 0.0005). Pulmonary flow volume increased from 63 +/- 14 ml/beat at rest to 70 +/- 13 ml/beat at 50 W (p < 0.005) to 76 +/- 12 ml/beat at 100 W (p = NS). CONCLUSION: Quantification of great vessel flow can be performed safely in healthy volunteers using MR flow measurements during submaximal physical exercise. These measurements may be used to study hemodynamic abnormalities in patients with cardiac disease.

Adult↗
PubMed1983

Long-term effects on central haemodynamics and body fluid volumes of ketanserin in essential hypertension studies at rest and during dynamic exercise.

The long-term haemodynamic effects of ketanserin, a new serotonin-antagonist, was examined in 13 patients of both sexes (age range 24-62 years) with mild and moderate essential hypertension (EH). Cardiac output (CO) and intra-arterial blood pressure (BP) were measured at rest and during exercise before and after nine months of therapy. On ketanserin the mean casual BP was lowered by 15/21 mmHg to 152/91 mmHg and five of the 13 patients became 'normotensive' (BP less than 140/90 mmHg). The intra-arterial systolic pressure fell by 5-8% and the diastolic pressure by 5-11% from pretreatment levels at rest supine, sitting and during 50, 100 and 150 W exercise. The fall in BP was associated with a reduction in CO at rest while during exercise both a fall in CO and in total peripheral resistance contributed to the hypotensive effect. The fall in CO was due to a reduction in heart rate (average: -4 to 8 beats/min). The stroke volume remained unchanged in all settings and oxygen consumption was not affected by the drug. Body weight and body fluid volumes did not change significantly. Eight patients complained of drowsiness and lack of concentration. It is concluded that in mild and moderate EH ketanserin induces a moderate BP reduction associated with a fall in CO. There is no large vasodilating effect after long-term ketanserin treatment either at rest or during exercise. Ketanserin does not influence body fluid balance. The incidence of side-effects is high.

Adult↗
PubMed2001

In-vivo intracellular pH at rest and during exercise in patients with essential hypertension.

BACKGROUND: Several studies in isolated cells have reported that intracellular pH (pHi) in individuals with essential hypertension may be relatively alkaline compared to normotensive individuals. Such an abnormality of pHi in hypertension would be consistent with enhanced sodium-hydrogen exchanger activity and may provide potential mechanisms by which hypertension and its complications could develop. OBJECTIVES: To determine in-vivo intracellular pH of skeletal muscle at rest and during recovery from exercise-induced acidosis in hypertensive and normotensive subjects. METHODS: Using 31-phosphorus magnetic resonance spectroscopy, pHi of the dominant flexor digitorum superficialis was measured in 20 Caucasian subjects (14 male) with essential hypertension and 20 normotensive controls matched for gender, age, race and body mass index. Measurements were made at rest and during the exercise and recovery periods of a stepped incremental maximal exercise protocol. The rate of pHi recovery from exercise-induced acidosis was calculated by linear regression over the first 210 s of recovery from the pHi time plots of respective subjects. RESULTS: Mean resting pHi in the hypertensive (7.05 +/- 0.04) and normotensive groups (7.06 +/- 0.04) were not significantly different. There was a significant effect of gender on pHi: mean pHi was 7.07 +/- 0.03 in males and 7.02 +/- 0.03 in females, respectively (P < 0.0005). The mean intracellular pH achieved by exercise was 6.74 +/- 0.31 in hypertensive individuals and not significantly different in normotensive individuals (6.68 +/- 0.19; P = 0.4). The mean rate of pHi recovery in the hypertensives was 0.08 +/- 0.03 pH units/min and not significantly different in normotensives (0.08 +/- 0.02; P = 0.4). CONCLUSIONS: These results contrast with previously documented abnormalities in the control of pHi in hypertension and demonstrate the absence of major in-vivo disturbances of pHi in skeletal muscle, both at rest and during recovery from exercise-induced acidosis, in essential hypertension. Therefore, it is possible that previously documented abnormalities of pHi and activity of the exchanger may be either specific to cell type or not present under in-vivo conditions.

Exercise↗
PubMedDate not supplied

Effect of verapamil on left ventricular function at rest and during exercise in normal men.

Verapamil is a calcium channel blocking agent used primarily for treatment of arrhythmias and coronary artery disease. It may also depress myocardial contractility. The purpose of this study was to assess the effect of verapamil on left ventricular function. Twelve normal men, 22-29 years of age, were studied at rest and during exercise, with and without verapamil, using first-pass radionuclide angiocardiography. Verapamil was administered by continuous intravenous infusion to produce steady-state blood levels of 106-123 ng/ml. The heart rate, ejection fraction, stroke volume index, and end-diastolic volume index were measured with and without the drug. Verapamil increased the mean resting heart rate from 74 to 78 beats/min (p = 0.001), decreased the mean stroke volume index from 48 to 42 ml/m2 (p = 0.01), and decreased the mean end-diastolic volume index from 77 to 71 ml/m2 (p less than 0.05). No changes in cardiac index, ejection fraction, end-systolic volume index, or peak systolic pressure/end-systolic volume ratio were observed at rest. No differences occurred in exercise hemodynamics. Thus verapamil at therapeutic dose levels did not significantly depress contractility or have other clinically important hemodynamic effects at rest or during exercise in normal subjects.

Adult↗
PubMed1997

Intensive exercise training during bed rest attenuates deconditioning.

A 30-d 6 degrees head-down bed rest project was conducted to evaluate variable high-intensity, short-duration, isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent resistive isokinetic exercise (IKE) training regimens designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (adaptive) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Major findings are summarized in this paper. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volumes (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (f) attenuated the decrease in peak VO2 by 50%, (g) attenuated loss of red cell volume by 40% but had no effect on loss of plasma volume, (h) induced positive body water balance, (i) had no adverse effect on quality of sleep or concentration, and (j) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regimens and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

Adaptation, Physiological↗
PubMed2000

Resting heart rate definition and its effect on apparent levels of physical activity in young children.

PURPOSE: Heart rate monitoring is widely used to measure physical activity in children, but it may be dependent on the definition of resting heart rate used and the protocol used to measure or derive resting heart rate (RHR). The aim of this study was to determine the effect of RHR definition on activity levels assessed by PAHR-25 (% time at >25% of RHR), PAHR-50 (% time at >50% of RHR), and activity heart rate (AHR; mean HR minus RHR). METHODS: Minute-to-minute heart rates were measured over 3 d in 20 healthy preschool children aged 3-4 yr. Resting heart rate was measured for 5 min after a 10-min rest and was also derived from the following different but commonly used protocols: 1) mean of lowest heart rate plus all heart rates within three beats; 2) mean of lowest 5; 3) lowest 10; 4) lowest 50. This gave five different definitions of RHR. Differences in RHR and in the derived indices of activity among definitions were tested for agreement using a Bland-Altman analysis, and by rank order correlation. RESULTS: Differences in RHR among all definitions were statistically significant. These resulted in significant differences in apparent physical activity levels: PAHR-25 varied 10-50% depending on the protocol used to define RHR; PAHR-50 varied by 16-65% as a function of the protocol used to define RHR. However, the different definitions of RHR had no significant influence on physical activity level when children were rank ordered. CONCLUSION: Choice of method for defining RHR has a profound effect on the apparent level of activity of children. This does not alter the relative assessment of activity by rank order. A consensus definition of RHR is desirable if comparisons of activity levels between samples or populations are to be made and if the adequacy of physical activity levels is to be assessed using heart rate.

Body Height↗
PubMed2002

Aerobic training and cardiovascular responses at rest and during exercise in older men and women.

PURPOSE: The effects of an intense 8-wk aerobic training program on cardiovascular responses at rest and during exercise, including heart rate variability (HRV) as an expression of autonomic modulation, were evaluated in subjects over 70 yr (mean: 73.9 +/- 3.5 yr). METHODS: Before and after training in 7 men and 8 women: a) heart rate (HR), blood pressures (BPs), pulse pressure (PP), and oxygen uptake were measured at rest, during, and after exhausting incremental exercise; b) HRV power spectra were calculated at rest in supine and sitting, and during and after two submaximal constant loads (5 min). Power in low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, >0.15 Hz) bands were expressed as a percent of total power minus power < 0.04 Hz. RESULTS: After training: a) at rest HR and HRV parameters (in both body positions) were unchanged, whereas BPs decreased; b) peak cycle resistance and oxygen consumption increased by 25% and 18%, respectively, but no change in maximal HR and BPs were found; c) during submaximal loads HR was unchanged at the same metabolic demand, whereas SBP and DBP were lower than before at low loads whereas PP was unchanged. LF power decreased and HF increased at oxygen uptakes above about 0.7 L.min-1 similarly before and after training; and d) recovery of all parameters was similar to pretraining and complete after 10 min CONCLUSIONS: The increase in exercise capacity without changes in cardiovascular parameters suggests that 8 wk of aerobic training augmented peripheral gas exchange but not delivery to muscle. The lack of effect on HRV indicates that the improvements in aerobic power and cardiac autonomic modulation, at least in subjects over 70 yr, are dissociated. Moreover, the metabolic demand seems to be the main factor for the changes in HRV power spectra that occur during exercise.

Aged↗
PubMed1999

Management of incidental durotomy without mandatory bed rest. A retrospective review of 20 cases.

STUDY DESIGN: A retrospective review of 20 patients with incidental durotomy treated without mandatory bed rest. OBJECTIVES: To determine whether patients with incidental durotomy can be treated effectively without multiple days of bed rest. SUMMARY OF BACKGROUND DATA: Incidental durotomy can cause postural headaches, nausea, vomiting, dizziness, photophobia, tinnitus, and vertigo. These symptoms are believed to result from a decrease in cerebrospinal fluid pressure, leading to traction on the supporting structures of the brain. Traditional management includes bed rest for up to 7 days to eliminate traction and reduce hydrostatic pressure during the healing process. METHODS: Twenty incidental durotomies were repaired intraoperatively with dural stitches and fibrin glue. Patients were allowed to ambulate according to the natural course after surgery without mandatory bed rest. Symptoms were monitored closely for 1 week, and long-term follow-up assessments were obtained at a minimum of 10 months. RESULTS: Of the 20 patients in this study, 75% had no symptoms after repair of the incidental durotomy. Each of the dural tears was 1-3 mm in length. Two patients reported headache, two reported nausea, and one reported tinnitus; no patients experienced vomiting. One patient (5%) had stitch loosening requiring revision surgery. There were no additional serious complications. CONCLUSIONS: This study has shown that the majority of patients with incidental durotomy can be treated effectively with dural stitches and fibrin glue. Patients can be permitted to ambulate immediately after surgery but should be cautioned to lay flat if they develop symptoms. This will reduce the costs related to the hospital stay and missed work.

Adult↗
PubMed2006

Genetic influences on baroreflex sensitivity during rest and mental stress.

OBJECTIVE: Baroreflex sensitivity (BRS) is a predictor of cardiovascular mortality and an indicator of sympathetic and parasympathetic autonomic regulation. Although the BRS is influenced by genetic factors, the evidence is limited, and it is unknown whether contributions of genes and environment to individual variation in BRS differ during rest and mental stress conditions. DESIGN AND METHODS: In 250 female twins, electrocardiogram and continuous finger blood pressure (BP) were assessed during two rest and two mental stress conditions. BRS was calculated as the mean modulus between inter-beat-interval and systolic BP. Genetic model fitting was used to investigate the relative contribution of genetic and environmental influences to individual differences in the BRS measures. RESULTS: Familial resemblance for all conditions was found which was clearly mainly due to genetic contributions. A trend was found for higher genetic influences in the mental stress conditions (42 and 45%) compared to rest conditions (14 and 22%), and higher shared environmental effects in rest conditions (14 and 16%) compared to mental stress conditions (0.5 and 1%). Although their magnitude differed, the same genetic and shared environmental factors affected individual differences in BRS in all four conditions. CONCLUSION: Genetic influences explained up to 45% of the individual variation in BRS. This considerable proportion of genetic variance would make BRS an useful candidate trait for future association and linkage studies in the search for genes influencing autonomic regulation and cardiovascular disease risk.

Adolescent↗
PubMed2004

Myocardial stunning demonstrated with rest and post-stress measurements of left ventricular function using dual-isotope gated myocardial perfusion SPECT.

OBJECTIVES: We have evaluated left ventricular ejection fraction (LVEF) at rest (REF) and after stress (SEF) with dual-isotope gated myocardial perfusion SPECT (GMPS) with 201Tl injected at rest and 99mTc sestamibi (99mTc-MIBI) injected at peak stress, to assess the occurrence of post-stress stunning. METHODS: Two hundred and thirty-six consecutive patients had GMPS at rest and post-stress. The summed stress and rest scores and the summed difference score (SDS) were calculated using a 17-segment model analysis of GMPS. An SDS >3 indicated significant ischaemia. The REF and SEF were automatically generated and the DEF (SEF-REF) was calculated. RESULTS: Significant stress induced ischaemia was observed in 103 patients (44%). REF was 54.72%+/-15.75% and SEF was 55.69%+/-16.65% (P<0.0015). DEF was -2.25+/-5.36 and 3.42+/-5.25 in patients with and without ischaemia, respectively (P<0.001). Post-stress stunning (>5% decrease in LVEF) was present in 68 patients (29%) and in 58/103 (56%) patients with ischaemia, after treadmill exercise or dipyridamole infusion and was more common in patients with severe ischaemia. The single significant predictor of DEF in univariate analysis and of stunning using logistic binary regression was stress induced ischaemia (P<0.0001). CONCLUSION: LVEF increases post-stress in patients with no ischaemia and may decrease in 56% of patients with ischaemia, possibly due to stunning. The best predictor of post-stress stunning is stress induced ischaemia and its occurrence is related to the degree of ischaemia.

Adolescent↗
PubMed2006

Decreased regional homogeneity in schizophrenia: a resting state functional magnetic resonance imaging study.

We used a newly reported regional homogeneity approach to measure the temporal homogeneity of blood oxygen level-dependent signal for exploring the brain activity of schizophrenia in a resting state. The results showed decreased regional homogeneity in schizophrenia, which distributed over the bilateral frontal, temporal, occipital, cerebellar posterior, right parietal and left limbic lobes, similar to the findings reported in previous resting state functional studies. The brain regions that showed decreased regional homogeneity are believed to be involved in the psychopathology and pathophysiology of schizophrenia. Our results indicate that abnormal brain activity of schizophrenia may exist in a resting state and the regional homogeneity may be potentially helpful in understanding the resting state of schizophrenia.

Adult↗
PubMed2004

Efficacy of a gravity-independent resistance exercise device as a countermeasure to muscle atrophy during 29-day bed rest.

AIM: This study determined changes in knee extensor and plantar flexor muscle volume during 29 days of bed rest with or without resistance exercise using a gravity-independent flywheel ergometer. METHODS: Seventeen men (26-41 years) were subjected to 29 days of bed rest with (n = 8) or without (n = 9) resistance exercise; Supine Squat (SS) and Calf Press (CP) performed every third day. Quadriceps and triceps surae muscle volume was determined before and after bed rest and force and power were measured during training. Prior to these interventions, reproducibility of this device for training and testing was assessed in 23 subjects who performed bilateral maximal concentric, eccentric and isometric (MVC) knee extensions and plantar flexions over repeated sessions with simultaneous measurements of force, power and electromyographic (EMG) activity. RESULTS: Quadriceps and triceps surae muscle volume decreased (P < 0.05) 10 and 16%, respectively, after 29 days bed rest. Exercise maintained quadriceps volume and mitigated triceps surae atrophy. Thus, either muscle showed different response across subject groups (P < 0.05). Force and power output during training were either maintained (P > 0.05) or increased (P < 0.05). EMG amplitude in the training mode was similar (SS; P > 0.05) or greater (CP; P < 0.05) compared with that elicited during MVC. Peak force and power test-retest coefficient of variation (CV) ranged 5-6% and 7-8% for SS and CP, respectively. CONCLUSION: The present data suggest that this resistance exercise paradigm counteracts quadriceps and abates the more substantial triceps surae muscle atrophy in bedridden subjects, and therefore should be an important asset to space travellers.

Adult↗
PubMed2006

Resting and exercise energy use in Antarctica: effect of 50% restriction in temperate climate energy requirements.

OBJECTIVE: To determine the impact of energy restriction (ER) upon the previously reported increased resting and exercise-related oxygen utilization, reduced body temperature, increased serum TSH, and reduced serum free T3 concentrations found during Antarctic residence (AR). DESIGN: Prospective, intervention with both paired controls and a similar reference control group (RG). PATIENTS AND MEASUREMENTS: Seven subjects were assessed before and after a 50% ER period of 60 h. This ER was carried out within 30 days of arriving in Antarctica in October (OCT) and again after 10 months AR in August (AUG). During the periods of ER, mean energy consumption was 5662 +/- 1344 kJ/day in OCT and 5529 +/- 967 kJ/day in AUG. Resting metabolic rate (RMR), a calculated resting metabolic rate (RMR(reg)) using a submaximal work regression, serum TSH, FT3 and tympanic temperature (Tty) were measured. These values were compared with a similar RG of 12 subjects reported previously who were studied in California, USA before and then again during AR. RESULTS: Weight declined by 1.1 +/- 0.1 kg/day (OCT) and 0.92 +/- 0.2 kg/day (AUG) with ER, resulting in a reduction of body weight by 3.1 +/- 0.4% in OCT (P = 0.0001) and 2.5 +/- 0.4% in AUG (P = 0.0015) during AR. The RMR before ER did not change with AR and it was not significantly different from the RG studied in California. With ER the RMR tended to decline in both OCT (132 +/- 5 to 122 +/- 4 mlO2/min/m2) and AUG (134 +/- 5 to 126 +/- 5 mlO2/min/m2), but these were not significant. By contrast, RMR(reg) obtained before ER was increased with AR by 22.5 +/- 7.8% (P = 0.01) in OCT and by 28.1 +/- 7.0% (P = 0.0008) in AUG over the RG values obtained in California. RMR(reg) did not decrease with ER in either OCT or AUG. The total energy expenditure derived from these measures of weight loss suggests that 24-h energy requirements are 74.4%[95% confidence interval (CI) 2.6-146.3; P < 0.05] more than those expected in temperate climates. Tty declined by 0.6 +/- 0.2 degrees C (P < 0.01) with AR compared with the RG measured in California, but was not affected by either period of ER. ER had no effect on FT3 but tended to decrease serum TSH in AUG (P = 0.06). CONCLUSIONS: Exercise-related energy requirements are increased with AR. Moderate ER may reduce resting but not exercise-related energy expenditure and it is associated with a weight loss exceeding expectations for 50% restriction of temperate climate energy predictions.

Acclimatization↗
PubMed2005

Diurnal spectral EEG fluctuations in narcoleptic patients during rest and reaction time tasks.

Narcolepsy is associated with lowered vigilance. Diurnal variation in vigilance appears altered, but the exact nature of this change is unclear. It was hypothesized that the homeostatic sleep drive is increased in narcolepsy. Decreased levels of vigilance are reflected in low frequency band power in the electroencephalogram (EEG), so these frequencies were expected to be increased in the narcolepsy group. Furthermore, it was expected that low frequency power should increase over the day. Narcoleptic patients and healthy controls participated (36 participants in total); they were not allowed to take medication or naps on the experimental day. EEG was measured at 9:00, 11:00, 13:00, 15:00, and 17:00 hours, during rest and during reaction time tasks. In the narcolepsy group, alpha power was lower at rest at all times. Delta and theta power during rest and task performance increased steadily over the day in this group, from 11:00 hours onwards. Additionally, in the narcolepsy group beta1 and beta2 power during rest appeared increased at the end of the day. The effects in the lower frequency bands strongly suggest that vigilance is low at all times. The progressive increase in low frequency power indicates that the sleep drive is enhanced. It is not clear whether this pattern reflects an extreme state of low vigilance, or a pathological brain condition. The effects in the higher frequencies suggest that narcoleptic patients may make an effort to counteract their low vigilance level.

Adult↗
PubMed1997

Autonomic control of bronchial circulation in awake sheep during rest and behaviour.

1. We tested the hypothesis that the pattern and the intensity of autonomic mechanisms causing vasoconstriction in the resting bronchial circulation of awake dogs also exists in awake sheep. It was also postulated that sighing behaviour and the associated bronchovascular dilatation induced by non-adrenergic, non-cholinergic (NANC) mechanisms observed in the dog exist in sheep. 2. Bronchial arterial blood flow to lower airways of both lungs of awake sheep was measured continuously using pulsed Doppler flow probes mounted on the bronchial artery at prior thoracotomy. 3. Cumulative and factorial analysis of responses to randomized combinations of autonomic alpha 1-, alpha 2-, beta 1- and beta 2-adrenoceptors and cholinoceptor autonomic blockade suggests that resting vasoconstrictor activity is less in sheep than in dogs. At normal aortic pressure, the autonomic activity of these receptor groups in the sheep lowers bronchial blood flow and conductance by 30%, whereas in the awake dog, the corresponding autonomic effect is 50%. 4. Tonic autonomic control of bronchial conductance can be partitioned in sheep to show significant and separate alpha- and beta-adrenoceptor vasoconstrictor activity at a ratio of 1.8:1, an effect normally offset by a weaker vasodilator alpha-/beta-adrenoceptor interaction. In contrast to the situation in awake dogs, cholinoceptors do not play a role in awake sheep. 5. Nitric oxide (NO) synthase inhibition in sheep using NG-nitro-L-arginine following blockade of alpha- and beta-adrenoceptors and cholinoceptors causes hypertension, but minor changes, if any, in pulmonary pressures or heart rate. Bronchial flow and conductance, however, fall from a higher resting conductance by approximately 50%, suggesting that, normally, resting bronchial flow conductance is dominated by strong tonic NO vasodilator effects that interact with weaker tonic autonomic vasoconstrictor effects. 6. Superimposed (respiratory) behaviours of sighing, sneezing and coughing, which involve negative swings in intrathoracic pressure and the movement of inspired air, evoke large active bronchovascular dilator effects. These appear to be largely NANC in origin and appear to be dependent, in part, on mechanisms associated with NO release. It is postulated that the C-fibre axon reflex using substance P, calcitonin gene-related peptide and neurokinin A may be involved. Vocalization and eructation do not evoke bronchovascular effects.

Adrenergic alpha-Antagonists↗
PubMed1990

The effects of hospitalization for rest on fetal growth, neonatal morbidity and length of gestation in twin pregnancy.

OBJECTIVE: To test whether a policy of hospitalization for bed rest, from 28-30 weeks gestation until delivery, lengthens the duration of gestation, improves fetal growth and decreases neonatal morbidity in twin pregnancy. DESIGN: A randomized controlled trial. SETTING: Harare Maternity Hospital, Zimbabwe. SUBJECTS: 118 women with an uncomplicated twin pregnancy between 28 and 30 weeks gestation. INTERVENTION: Hospitalization for bed rest. Encouraged to rest in bed as much as possible, although voluntary ambulation was allowed. MAIN OUTCOME MEASURES: Gestational age at delivery and number of infants delivered preterm (less than 37 weeks); birthweight and number of small-for-gestational age (SGA) infants; neonatal morbidity was assessed by number of infants requiring admission to the neonatal unit and the length of stay. RESULTS: There was no effect on duration of gestation or the occurrence of preterm delivery. Mean birthweight was greater in the hospitalized group (t = -2.28, df 234, P = 0.02) and there were fewer SGA infants (OR 0.57, 95% CI 0.33-0.96). No differences were found in neonatal morbidity. CONCLUSIONS: Hospitalization for bed rest does not prolong pregnancy but can improve fetal growth, although this was not reflected in improved neonatal morbidity. Whether twin fetal growth can be enhanced similarly in other populations should be investigated.

Bed Rest↗