Methodological approaches to estimation of morning urge of arterial pressure in essential hypertensives

AIM: To estimate the time intervals of a morning arterial pressure urge (MAPU) and MAPU characteristics in patients with essential hypertension (EH). MATERIAL AND METHODS: The study enrolled 70 patients (50 male and 20 female) with EH of the first (n = 41) and second (n = 20) degrees aged 34-65 years (mean age 50.4 +/- 0.9 years). The control group consisted of 9 healthy men. Morning dynamics of arterial pressure (AP) and heart rate (HR) was studied basing on the data of 24-h AP monitoring (Spacelabs-90207, USA). RESULTS: Dynamics of AP from nocturnal to diurnal patterns in both hypertensive and normotensive subjects falls into 3 phases: a premorning urge (from 4-5 a.m. to waking up) with a characteristic slow rise in AP and HR; a morning urge (from waking up for 4-5 hours) with a characteristic forced AP and HR rise); a diurnal urge (from 11 a.m. to 13-14 p.m.) with characteristic slowing down of AP and HR rise. Patients with EH of the first and second degree vs normotensive subjects had unfavourable changes in morning dynamics of AP and HR: a significant progressive growth of maximal systolic and diastolic pressure proportional to mean circadian AP levels; a rise of morning hours index of AP which characterizes amplitude-speed features of AP and HR. CONCLUSION: To characterize MAPU most completely it is recommended to estimate the following parameters: wave index (to assess AP conversion from one level to another), mean rate of AP change per hour (to prevent influence of random factors on the rate of MAPU); relative maximal values of AP (to estimate maximal AP values in morning hours and nocturnal mean AP).     

Values of sleep/wake, activity/rest, circadian rhythms, and fatigue prior to adjuvant breast cancer chemotherapy

Fatigue is the most prevalent and distressing symptom experienced by patients receiving adjuvant chemotherapy for early stage breast cancer. Higher fatigue levels have been related to sleep maintenance problems and low daytime activity in patients who have received chemotherapy, but knowledge describing these relationships prior to chemotherapy is sparse. The Piper Integrated Fatigue Model guided this study, which describes sleep/wake, activity/rest, circadian rhythms, and fatigue and how they interrelate in women with Stage I, II, or IIIA breast cancer during the 48 hours prior to the first adjuvant chemotherapy treatment. The present report describes these variables in 130 females, mean age=51.4 years; the majority were married and employed. Subjective sleep was measured by the Pittsburgh Sleep Quality Index and fatigue was measured by the Piper Fatigue Scale. Wrist actigraphy was used to objectively measure sleep/wake, activity/rest, and circadian rhythms. Mean Pittsburgh Sleep Quality Index score was 6.73+/-3.4, indicating poor sleep. Objective sleep/wake results were within normal limits established for healthy individuals, except for the number and length of night awakenings. Objective activity/rest results were within normal limits except for low mean daytime activity. Circadian rhythm mesor was 132.3 (24.6) and amplitude was 97.2 (22.8). Mean Piper Fatigue Scale score was 2.56+/-2, with 72% reporting mild fatigue. There were significant relationships between subjective and objective sleep, but no consistent patterns. Higher total and subscale fatigue scores were correlated with most components of poorer subjective sleep quality (r=0.25-0.42, P< or =0.005).     

Sleep parameters in patients using pacemakers with sleep rate function on

INTRODUCTION: The cardiovascular system (CVS) is heavily influenced by the autonomic nervous system. Additionally, there is a functional alteration during the various stages of sleep. In nonrapid eye movement (NREM), a state of cardiovascular relaxation occurs during stages three and four. A large amount of rapid ocular movements is concentrated in rapid eye movement (REM) sleep. During this phase, fluctuations in arterial pressure (AP) and heart rate (HR) can be readily noted. Sleep disordered breathing (SDB) has been associated with cardiac rhythm disorders. Recently, cardiac rhythm disorder treatment with pacemaker (PM) highlighted a reduction in abnormal respiratory events during sleep. OBJECTIVE: Comparison of sleep parameters of patients using PM with a sleep rate (SR) algorithm based on its rate-modulated capability during physical activity (Integrity PM with SR function on and off). METHODS: Twenty-two patients (14 women, 8 men), implanted with an Integrity PM (St. Jude Medical Cardiac Rhythm Management Division, Sylmar, CA) with SR function for standard clinical indications, were evaluated utilizing a double-blind protocol. The indication for pacing included sinus node disease (SND), atrium ventricular blockage (AVB), and atrial fibrillation (AF). Following randomization, half of our patients had SR function switched to "on" mode while the other half were on "off" mode. During the first stage of the protocol, all patients underwent two consecutive nights of polysomnographic sleep recordings (PSG). During the first night patients slept in the sleep lab only for adaptation purpose. PSG full recording was carried out in the subsequent night. At a later stage, the programing of SR functions was shifted to "on" or "off" modes. One week later, a third assessment was undertaken. RESULTS: Twelve patients (54%) showed sleep efficiency improvement (total sleeping time/recording time) with PM SR on. This group had the least effective sleep efficiency with PM off, if compared with the others who highlighted no change in this sleep parameter (72 +/- 12 vs 81 +/- 7%, P = 0.01, respectively). This first group displayed a lower latency for REM sleep than the last one (89 +/- 55 vs 174 +/- 107 minutes, P = 0.01, respectively). In 11 (50%) patients, the number per sleep hour of microarousals was reduced when PM SR was switched on. When we compared such findings to the group whose parameters had not changed, we noted that the first set of patients were sleepier (ESE: 9 +/- 4 vs 5 +/- 5, P = 0.04, respectively), and showed more microarousals with PM SR off (20 +/- 14 vs 7 +/- 5 microarousal/hour, P = 0.007). CONCLUSION: In PM patients with sleep-related issues, the SR function activation improved sleep both from a qualitative and quantitative perspective.     

Circadian rhythms and sleep patterns in urban Greek couples

A convenience sample of 14 adults (seven couples) who intentionally nap regularly was recruited to describe circadian rhythms and sleep patterns in a culture in which afternoon naps are routine. Participants wore a wrist actigraph for 48 hr during May to obtain two peaks and troughs of activity data. Peak activity, estimated by cosinor analysis (acrophase), occurred at 1542 hours for men and at 1600 hours for women. Compared to their male partners, women had a later acrophase and a significantly stronger 24-hr rhythm, despite similar nap and nighttime sleep schedules. Men had more awakenings during the night and slightly shorter naps than did women. For the 24-hr period, men averaged 6.8 +/- 1.0 hr of sleep and women averaged 7.4 +/- 1.1 hr. Results indicate that Greek adults delay sleep onset at night and awaken early in the morning. Among this small group, naps are an accepted cultural behavior.     

Discrepancy between circadian rhythms of inulin and creatinine clearance.

To elucidate the disparity between circadian rhythmicity of inulin and creatinine clearance, we simultaneously measured inulin and creatinine clearances every 3 hours during 1 day in 14 normal subjects and in 8 patients with nephrotic syndrome. All patients and normal subjects had a circadian rhythm for inulin clearance with a maximum during daytime and a relative amplitude of 21% +/- 2%. For creatinine clearance a rhythm was either absent or reduced in relative amplitude (p less than 0.01). In all subjects the rate of tubular creatinine secretion was higher at minimum of inulin clearance (night) than at maximum (day). The fractional clearance (relative to inulin) of creatinine was also higher during the night: normal subjects, 1.28 +/- 0.02 versus 1.10 +/- 0.02; patients, 1.78 +/- 0.08 versus 1.45 +/- 0.05 (p less than 0.005). This demonstrates the inaccuracy of creatinine clearance as a measure of glomerular filtration rate (GFR). By subsequent blocking of the tubular secretion of creatinine with cimetidine in four normal subjects, creatinine clearance became similar to inulin clearance during day and night. This confirms that high tubular secretion of creatinine during the night counteracts the normal rhythmicity of glomerular filtration of creatinine. As a result, plasma creatinine concentration is nearly constant during a 24-hour period. In conclusion, tubular creatinine secretion has a circadian rhythm with a phase opposite to the rhythm of GFR, thus blunting or causing absence of a circadian rhythm for creatinine clearance.     

Fatigue, sleep, and circadian rhythms prior to chemotherapy for breast cancer

Goals Previous investigations have shown that women undergoing chemotherapy for breast cancer experience both disturbed sleep and fatigue. However, most of the previous research examined women either during or after chemotherapy. This study examined sleep, fatigue, and circadian rhythms in women with breast cancer before the start of chemotherapy.Patients and methods Eighty five women with Stages I–IIIA breast cancer who were scheduled to begin adjuvant or neoadjuvant anthracycline-based chemotherapy participated. Each had sleep/wake activity recorded with actigraphy for 72 consecutive hours and filled out questionnaires on sleep, fatigue, depression, and functional outcome.Main results On average, the women slept for about 6 h a night and napped for over an hour during the day. Sleep was reported to be disturbed and fatigue levels were high. Circadian rhythms were robust, but women who were more phase-delayed reported more daily dysfunction (p<0.01).Conclusions The data from the current study suggest that the women with breast cancer likely experience both disturbed sleep and fatigue before the beginning of chemotherapy. Although their circadian rhythms are robust, breast cancer patients with more delayed rhythms experience more daily dysfunction secondary to fatigue. These data suggest that strategies to improve disturbed sleep and to phase-advance circadian rhythms prior to initiation of chemotherapy may be beneficial in improving daily function in breast cancer patients.     

Diurnal variation of QT interval in patients with VVI pacemaker

In nine patients with chronically implanted ventricular pacemaker (VVI), diurnal variation of the QT interval was studied. The mean age of the patients was 74.2 years and underlying diseases were atrioventricular block (three patients), sick sinus syndrome (four patients) and chronic atrial fibrillation with bradycardia and heart failure (two patients). Eight of the nine patients showed longer QT intervals during sleep than during waking. Only one patient showed no change in QT interval during sleep and during wake time. The mean QT interval of the nine patients at each hour was slightly longer (9 msec) during sleep than that during each awake hour (p less than 0.001). The prolongation of QT interval during sleep may offer a possible mechanism of some nocturnal arrhythmias.     

Patient-ventilator interaction and sleep in mechanically ventilated patients: pressure support versus proportional assist ventilation

OBJECTIVES: To understand the role of patient-ventilator asynchrony in the etiology of sleep disruption and determine whether optimizing patient-ventilator interactions by using proportional assist ventilation improves sleep. DESIGN: Randomized crossover clinical trial. SETTING: A tertiary university medical-surgical intensive care unit. PATIENTS: Thirteen patients during weaning from mechanical ventilation. INTERVENTIONS: Patients were randomized to receive pressure support ventilation or proportional assist ventilation on the first night and then crossed over to the alternative mode for the second night. Polysomnography and measurement of light, noise, esophageal pressure, airway pressure, and flow were performed from 10 pm to 8 am. Ventilator settings (pressure level during pressure support ventilation and resistive and elastic proportionality factors during proportional assist ventilation) were set to obtain a 50% reduction of the inspiratory work (pressure time product per minute) performed during a spontaneous breathing trial. MEASUREMENTS AND MAIN RESULTS: Arousals per hour of sleep time during pressure support ventilation were 16 (range 2-74) and 9 (range 1-41) during proportional assist ventilation (p = .02). Overall sleep quality was significantly improved on proportional assist ventilation (p < .05) due to the combined effect of fewer arousals per hour, fewer awakenings per hour (3.5 [0-24] vs. 5.5 [1-24]), and greater rapid eye movement (9% [0-31] vs. 4% [0-23]), and slow wave (3% [0-16] vs. 1% [0-10]) sleep. Tidal volume and minute ventilation were lower on proportional assist ventilation, allowing for a greater increase in Paco2 during the night. Patient-ventilator asynchronies per hour were lower with proportional assist ventilation than with pressure support ventilation (24 +/- 15 vs. 53 +/- 59; p = .02) and correlated with the number of arousals per hour (R = .65, p = .0001). CONCLUSIONS: Patient ventilator discordance causes sleep disruption. Proportional assist ventilation seems more efficacious than pressure support ventilation in matching ventilatory requirements with ventilator assistance, therefore resulting in fewer patient-ventilator asynchronies and better quality of sleep.     

Circadian regulation of human sleep and age-related changes in its timing, consolidation and EEG characteristics.

The light-entrainable circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus regulates the timing and consolidation of sleep by generating a paradoxical rhythm of sleep propensity; the circadian drive for wakefulness peaks at the end of the day spent awake, ie close to the onset of melatonin secretion at 21.00-22.00 h and the circadian drive for sleep crests shortly before habitual waking-up time. With advancing age, ie after early adulthood, sleep consolidation declines, and time of awakening and the rhythms of body temperature, plasma melatonin and cortisol shift to an earlier clock hour. The variability of the phase relationship between the sleep-wake cycle and circadian rhythms increases, and in old age sleep is more susceptible to internal arousing stimuli associated with circadian misalignment. The propensity to awaken from sleep advances relative to the body temperature nadir in older people, a change that is opposite to the phase delay of awakening relative to internal circadian rhythms associated with morningness in young people. Age-related changes do not appear to be associated with a shortening of the circadian period or a reduction of the circadian drive for wake maintenance. These changes may be related to changes in the sleep process itself, such as reductions in slow-wave sleep and sleep spindles as well as a reduced strength of the circadian signal promoting sleep in the early morning hours. Putative mediators and modulators of circadian sleep regulation are discussed.     

Rotating Shiftwork Schedules: Can We Enhance Physician Adaptation to Night Shifts?

Objectives : To evaluate the effectiveness of a broad, literature-based night shiftwork intervention for enhancement of emergency physicians' (EPs') adaptation to night rotations. Methods : A prospective, double-blind, active placebo-controlled study was conducted on 6 attending physicians in a university hospital ED. Three data sets were collected under the following conditions: baseline, after active placebo intervention, and after experimental intervention. In each condition, data were collected when the physicians worked both night and day shifts. Measurements included ambulatory polysomnographic recordings of the main sleep periods, objective performance tests administered several times during the subjects' shifts, and daily subjective ratings of the subjects' sleep, moods, and intervention use. Results : The subjects slept an average of 5 hr 42 min across all conditions. After night shifts, the subjects slept significantly less than they did after day shifts (5 hr 13 min vs 6 hr 20 min; p < 0.05). The physicians' vigilance reaction times and times for intubation of a mannequin were significantly slower during night shifts than they were during day shifts (p = 0.007 and p < 0.04, respectively), but performances on ECG analysis did not significantly differ between night and day shifts. Mood ratings were significantly more negative during night shifts than they were during day shifts (more sluggish p < 0.04, less motivated p < 0.03, and less clear thinking p < 0.04). The strategies in the experimental intervention were used 85% of the time according to logbook entries. The experimental and active placebo interventions did not significantly improve the physician's performance, or mood on the night shift, although the subjects slept more after both interventions. Conclusions : Although the experimental intervention was successfully implemented, it failed to significantly improve attending physicians' sleep, performance, or mood on night shifts. A decrease in speed of intubation, vigilance reaction times, and subjective alertness was evident each time the physicians rotated through the night shift. These findings plus the limited sleep across all conditions and shifts suggest that circadian-mediated disruptions of waking neurobehavioral functions and sleep deprivation are problems in EPs.     

Differences between young and elderly subjects in seasonal and circadian variations of total plasma proteins and blood volume as reflected by hemoglobin, hematocrit, and erythrocyte counts

Circadian and seasonal rhythms in total plasma proteins were documented in healthy young men (around 24 years old), and in elderly subjects (both sexes), including senile-dementia patients in their eighties. The concentration of plasma proteins within a given group changed predictably (7-13%), depending on the hour of sampling and the season. Concentrations decreased noticeably around 04:00 h, then peaked around 08:00 h (shortly after waking). The 24-h mean concentrations of total plasma proteins were lower in the elderly groups than in the young men. But the seasonal variations of the 24-h mean values were strikingly larger in the elderly groups (7-8 g/L) than in the young men (2-5 g/L). Moreover, the circadian profiles of plasma proteins differed from the profiles of hematocrit, hemoglobin, and erythrocyte counts. Evidently, circadian variations of blood volume may not be the only element accounting for the variations of plasma protein concentrations. We suggest that the rhythms in plasma protein concentrations be taken into account when reference values are set. Circadian and seasonal variations in plasma proteins may also significantly affect the transport and binding of drugs, especially in the aged.     

Modafinil [2-[(diphenylmethyl)sulfinyl]acetamide] and circadian rhythms in syrian hamsters: assessment of the chronobiotic potential of a novel alerting compound

In Syrian hamsters, behavioral procedures for inducing arousal (e.g., running in a novel wheel or gentle handling) can shift circadian rhythms when applied during the usual sleep period ("subjective day") and can attenuate phase shifts to light during the active period ("subjective night"). This raises the possibility that drugs that affect behavioral state may have "chronobiotic" potential. We characterized the effects of modafinil (2-[(diphenylmethyl)sulfinyl]acetamide), an atypical alerting compound, on circadian rhythms in male Syrian hamsters. Electroencephalogram recordings and video observations confirmed that modafinil dose dependently increases wakefulness at the expense of slow-wave and paradoxical sleep with no increase in locomotor activity per unit of time awake. Despite inducing arousal, modafinil at these doses (150 or 300 mg/kg), administered in the subjective day or early or late in the subjective night, did not perturb circadian phase. Modafinil (300 mg/kg) also had no effect on phase shifts to light exposure either early or late in the night and did not alter the size of phase shifts induced by running in a novel wheel for 3 h during the mid-day. Modafinil (300 mg/kg) did, however, decrease by approximately 50% the amount of novel wheel-stimulated running, moving leftward the dose-response relation between wheel revolutions and shift magnitude. These results indicate that, in Syrian hamsters, modafinil alone has no significant chronobiotic efficacy. Nevertheless, this agent may increase the sensitivity of the circadian pacemaker to nonphotic stimuli and may thus have some potential as a tool for promoting clock resetting in combination with behavioral strategies.     

Circadian rhythm, shiftwork and you!

Chronobiological knowledge is increasing and the relationship between this knowledge and shiftwork is becoming clearer. This, in turn, is highlighting a need to facilitate a mix of permanent (day, evening and night) and rotational shift systems within individual wards or units. Is it perhaps time to allow greater flexibility in how individual nurses deal with the profession's need to care for patients throughout the 24 hour period? This review will focus on the 24 hour day-night or circadian rhythms and the consequences of the disruption of these rhythms as nurses undertake shiftwork and other activities which demand efficient functioning at times when an individual's circadian rhythms are expecting them to be at rest. As disruption of these rhythms is essentially unavoidable when 24 hour care is required, the choice becomes one of determining a preference for tolerable rhythm desynchrony and shorter more frequently occurring episodes of night work, or some degree of rhythm synchrony and adaptation during slightly longer but less frequent episodes of rhythm disruption.     

Acute sleep deprivation is associated with increased electrocardiographic P-wave dispersion in healthy young men and women

Background: Sleep deprivation (SD) is associated with worse cardiovascular outcome including mortality. Prolonged P-wave duration and P-wave dispersion (Pd) are known to represent inhomogeneous conduction of sinus impulses and are known to be electrophysiologic predictors of atrial fibrillation. Pd in normal subjects has been reported to be influenced by the autonomic tone. Because autonomic tone is affected by sleep and sleep duration, we evaluated the effect of acute SD on P-wave duration and Pd in healthy young adults and whether the effect was gender selective.
Methods : We obtained electrocardiograms of 37 healthy young volunteers (age: 28.45 ± 7.97; 11 women) after a night of regular sleep and repeated after a night with sleep debt. We measured minimum and maximum P-wave durations (Pmin, Pmax) and Pd in milliseconds.
Results : Average sleep time of the subjects were 7.7 ± 0.8 hours during regular sleep and 1.7 ± 1.6 hours during a night of sleep debt (P < 0.001). Subjects had significantly lower values of Pmin in milliseconds after a night of sleep debt when compared to regular sleep (65.13 ± 8.03 vs 74.86 ± 10.95; P < 0.001), whereas they had significantly higher values of Pmax and Pd (102.16 ± 9.46 vs 95.13 ± 11.21; P < 0.001 and 37.02 ± 8.11 vs 20.27 ± 11.42; P < 0.001, respectively). In Pearson's correlation analysis Pmin was positively and Pmax and Pd were negatively correlated with sleep time (P < 0.001, r = 0.465; P = 0.003, r =−0.336 and P < 0.001, r =–0.698 respectively). Effect of SD on P-wave duration and Pd was similar for both men and women.
Conclusions : In conclusion, prolongation of Pmax and Pd in acute SD suggests that acute SD might contribute to development and/or recurrence of atrial fibrillation.     

Circadian rhythm of leptin, orexin and ghrelin

Both metabolic syndrome and sleep disorder are major health problems. Leptin, orexin, ghrelin are implicated in regulation of energy homeostasis and sleep/wakefulness. The levels of these substances exhibit circadian fluctuations, and abnormalities in these rhythms were observed in those disorders. Serum leptin levels were increased during night. Cerebrospinal fluid orexin A levels were increased during active phase. Plasma ghrelin concentrations were increased before meals and during night. High concentrations of leptin during sleep might help keeping sleep by inhibition of feeding behavior and arousal through inhibition of neuropeptide Y and orexin neurons. On the contrary, high concentrations of ghrelin before meal might enhance wakefulness through activation of orexin neurons. These results suggest that the circadian rhythms of these substances are important for maintenance of normal energy homeostasis and sleep/wakefulness.     

Assessment of left atrial volumes in sinus rhythm and atrial fibrillation using the biplane area-length method and cardiovascular magnetic resonance imaging with TrueFISP.

OBJECTIVES: To determine whether the biplane area-length method can be used for the evaluation of left atrial volumes and ejection fraction with cardiovascular magnetic resonance imaging (CMR) by TrueFISP in normal subjects and patients with atrial fibrillation. BACKGROUND: Atrial fibrillation is the most common arrhythmia in elderly patients. Left atrial size and volumes play an important role in predicting short and long-term success after cardioversion. METHODS: Fifteen healthy subjects (mean age 65.6+/-6.4 years) and 18 patients (mean age 67.2+/-8.8 years) with atrial fibrillation were examined by CMR (Magnetom, Siemens, Erlangen, Germany). Images were acquired by TrueFISP using the horizontal and vertical long-axis plane to measure left atrial end-diastolic and end-systolic areas and longitudinal dimensions. Volumes were determined with commercially available software. Left atrial end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) were determined by the biplane area-length method and compared to findings obtained by the standard short-axis method. Images were acquired and analyzed a second time in the patients with atrial fibrillation. RESULTS: There was no difference in age between men and women (p=0.147) and healthy subjects and patients (p=0.128) included in the study. EDV and ESV were significantly higher and SV and EF significantly lower in patients with atrial fibrillation than in healthy subjects (p < or = 0.009), regardless of the method used. The values obtained for EDV and ESV by the biplane area-length method were significantly higher in both healthy subjects (p<0.001) and patients with atrial fibrillation (p<0.001) than those obtained by the standard short-axis approach, whereas SV (p> or = 0.057) and EF (p> or = 0.118) did not differ significantly. In the second investigation in patients with atrial fibrillation, ESV, SV, and EF did not differ significantly between the two methods (p> or =0.481). Assessment of interobserver variability revealed good agreement in the findings of the two observers, both in normal sinus rhythm and atrial fibrillation (overall variability 0.8+/-6.5%). CONCLUSIONS: The biplane area-length method can be used in CMR images obtained by TrueFISP to assess left atrial volumes and ejection fraction in normal subjects and patients with varying cardiac cycle length, as in atrial fibrillation.     

Circadian rhythms of body temperature and activation and the well-being of older women

The circadian parameters of body temperature and activation were studied in relationship to the well-being of 18 healthy women, aged 65-80 years. The women took oral temperature readings with an IVAC 2000 electronic thermometer and completed 1 of 12 alternate forms of the Activation-Deactivation Adjective Check List every 2 hours during waking hours for 7 consecutive days (2 subjects followed this procedure for 3 midweek days in 2 consecutive weeks). Approximately 2 hours before going to bed, all subjects completed the General Well-Being Questionnaire that was modified for this study to measure daily fluctuations in well-being. Hypotheses were examined using cosinor analysis and Pearson correlations. Temperature and activation were demonstrated to manifest circadian periodicities. There were no correlations between the parameters of these rhythms and the well-being of the subjects.     

Effect of nCPAP therapy on heart rate in patients with obstructive sleep apnoea-hypopnoea

BACKGROUND: Elevated heart rate (HR) is a risk factor for cardiovascular disease. The effects of obstructive sleep apnoea-hypopnoea syndrome (OSAHS) on HR are controversial. AIM: To investigate the effect of nasal continuous positive airway pressure (nCPAP) therapy on HR in OSAHS patients. METHODS: Sixty-two OSAHS patients underwent 24-h electrocardiographic recording, both before and 3 or 4 days after instigation of nCPAP. RESULTS: After nCPAP was started, HR significantly decreased (mean +/- SD 71.8 +/- 10.6 vs. 67.5 +/- 9.4 bpm, p < 0.0001), both in the daytime (0600-2200 h, 76.3 +/- 12.2 vs. 72.2 +/- 10.2 bpm, p < 0.0001) and at night-time (2200-0600 h, 64.5 +/- 9.1 vs. 60.0 +/- 8.9 bpm, p < 0.0001). HR was significantly reduced in both periods in the 44 patients with hypertension and/or diabetes mellitus, but only during the night-time in the 18 with neither condition. Before nCPAP treatment, HR was positively correlated with percentage time of arterial O2 saturation <90% during sleep (p = 0.008) and with the apnoea-hypopnoea index during sleep (p = 0.003). In 15 patients undergoing HR for 2 days before starting nCPAP, the mean HRs for the two periods were similar (p = 0.95). DISCUSSION: nCPAP therapy appears to decrease HR in OSAHS patients, and may thereby reduce their risk of cardiovascular disease.     

Circadian index as indicator of stable organization of heart circadian rhythm

The author proposes to use circadian index (CI) as a method of evaluation of major structure of the circadian heart rhythm profile in Holter monitoring. CI is calculated as a ratio of awaking (7 a.m. to 22 p.m.) mean heart rate to sleep (23 p.m. to 6 a.m.) mean heart rate. CI was estimated by the literature data on 7648 healthy subjects and patients aged 2 to 79 years. In healthy subjects CI was stable irrespective of the sex and age. Normal CI makes up 1.33 +/- 0.05. All the cardiovascular patients exhibited increasing rigidity of the rhythm with the disease progression and deterioration of the prognosis. In patients with diabetes mellitus with vegetopathy rigidity of the circadian rhythm grows with aggravation of vegetopathy. In neurological patients free of vegetopathy CI was normal. Intensification of the heart rhythm profile was seen in patients with high sensitivity to catecholamines.     

Diurnal variation of plasma atrial natriuretic peptide in normals and patients with enuresis nocturna.

The circadian variation of plasma atrial natriuretic peptide (ANP) in relation to urinary excretion of sodium (UNa) and potassium (UK) as well as clearance of creatinine (Ccrea) was assessed in 15 juvenile patients with enuresis nocturna and compared with 11 age-, sex-, and weight-matched normal subjects. Normal juveniles showed a highly significant diurnal variation (p less than 0.001) of plasma ANP with diurnal peak levels at midnight (0000 hours) and minimum levels at 0400 hours. Enuretic patients showed a similar diurnal rhythmicity with normal levels during day and night. In normals both UNa and UK showed significant diurnal rhythmicity with a marked reduction from daytime to night-time. Although the total diurnal excretions of UNa and UK were similar to normals, patients with enuresis showed abnormal diurnal variation in both UNa (p less than 0.05) and UK (p less than 0.01). The abnormal circadian rhythm of UNa and UK in enuretics seemed to be caused by abnormal tubular handling as similar abnormalities were found in the fractional excretions and as the circadian variation of Ccrea was normal. Especially during the first hours of sleep (2200 hours to 0000 hours), the patients showed polyuria (230 +/- 138 ml vs 116 +/- 58 ml, p less than 0.01), natriuresis (20.9 +/- 16.3 mmol l-1 vs 10.7 +/- 6.8 mmol l-1, p less than 0.01), and kaliuresis (7.3 +/- 6.3 mmol l-1 vs 3.7 +/- 2.3 mmol l-1, p less than 0.05), despite normal levels of plasma ANP. In conclusion, the study describes the diurnal variation of plasma ANP in relation to urinary excretion of sodium and potassium in a juvenile normal population. Patients with nocturnal enuresis show abnormal diurnal rhythmicity in the urinary excretion of sodium and potassium that is not correlated to the plasma levels of ANP.