The comparison of nasal surgery and CPAP on daytime sleepiness in patients with OSAS

OBJECTIVE

Residual sleepiness after continuous positive airway pressure (CPAP) is a critical problem in some patients with obstructive sleep apnea syndrome (OSAS). However, nasal surgery is likely to reduce daytime sleepiness and feelings of unrefreshed sleep. The aim of this study is to clarify the effects of nasal surgery and CPAP on daytime sleepiness.

METHODOLOGY

This is a retrospective and matched-case control study. The participants were consecutive 40 patients with OSAS who underwent nasal surgery (Surgery group) and 40 matched patients who were treated with CPAP (CPAP group).

RESULTS

In the Surgery group, although the nasal surgery did not decrease either apnea or hypopnea, it improved oxygenation, the quality of sleep. In the CPAP Group, the CPAP treatment reduced apnea and hypopnea, and improved oxygenation, quality of sleep. The degree of relief from daytime sleepiness was different between the two groups. The improvement of Epworth Sleepiness Scale was more significant in the Surgery Group than those in the CPAP Group (Surgery from 11.0 to 5.1, CPAP from 10.0 to 6.2).

DISCUSSION

These findings suggest that the results of the nasal surgery is more satisfactory for some patients with OSAS than CPAP on daytime sleepiness.

Prediction of oral appliance treatment outcome in obstructive sleep apnoea syndrome: a preliminary study

OBJECTIVE

Predictors of treatment outcome of oral appliances (OAs) in patients with obstructive sleep apnoea syndrome (OSAS) are not known. There is a pressing need for simple, clinically useful tools to predict treatment outcome. This study aimed to identify predictors of successful OA therapy for OSAS, including evaluation of pharyngeal morphology, which can be measured during routine examination by an otorhinolaryngologist.

METHODOLOGY

This was a prospective study of 26 OSAS patients treated with OAs. A favourable outcome was obtained in 14 patients (responders) but not in 12 patients (nonresponders). The baseline patient characteristics and polysomnography and rhinopharyngeal findings were analysed.

RESULTS

Body mass index (BMI) was significantly lower in responders versus nonresponders (23.6 ± 2.8 vs. 27.9 ± 4.7 kg/m2; p < 0.05). Pharyngeal morphology, age, sex and nasal resistance did not differ between the groups. Multiple regression analysis showed that BMI was a significant predictor of improvement in the apnoea/hypopnoea index after OA treatment (p < 0.05).

CONCLUSION

Here we demonstrated that BMI is a favourable predictor of OA treatment outcome in OSAS patients. Among the OSAS patients, responders had wider retroglossal spaces than nonresponders.

Circadian rhythm of autonomic activity in patients with obstructive sleep apnea syndrome

BACKGROUND AND HYPOTHESIS

Although the immediate effects of sleep apnea on hemodynamics and the neurological system have been studied, little is known about the circadian rhythm of heart rate variability in patients with obstructive sleep apnea syndrome (OSAS). The purpose of the present study was to investigate the effects of sleep apnea on the autonomic activity during daytime, which may play some role in the pathogenesis of cardiovascular complications in OSAS.

METHODS

We studied 18 middle-aged male patients with OSAS and 10 age-matched control subjects. Patients with OSAS were classified according to the severity of OSAS: patients with an apnea index (AI) < 20 were considered to have mild OSAS (Group 1, n = 8) and patients with an AI > or = 20 were considered to have severe OSAS (Group 2, n = 10). Heart rate variability was calculated from the 24-h ambulatory electrocardiograms by the Fourier transformation. Power spectra were quantified at 0.04-0.15 Hz [low frequency power (LF)ln(ms2)] and 0.15-0.40 Hz [high frequency power (HF)ln(ms2)]. The HF component and the ratio of LF to HF were used as indices of the parasympathetic and sympathetic activity, respectively.

RESULTS

The circadian rhythms of the LF, HF, and LF/HF ratio differed significantly in Group 2 compared with Group 1 and control subjects (p < 0.05). Hypertension (> 160/95 mm Hg) was found in 7 (70.0%) of 10 patients in Group 2, and in 1 (12.5%) of 8 patients in Group 1. Echocardiographic evidence of left ventricular hypertrophy (LVH) (an interventricular septal thickness or a left ventricular posterior wall thickness > or = 12 mm) was found in 3 (30.0%) of 10 patients in Group 2, and in 1 (12.5%) of 8 patients in Group 1. The mean HF from 4 A.M. to 12 noon was significantly lower in Group 2 than in Group 1 and the control group, and it correlated significantly with the lowest nocturnal SaO2 (r = 0.58, p < 0.05). The mean LF/HF ratio during the same period was significantly higher in Group 2 than in Group 1 and the control group, and it correlated significantly with total time of the nocturnal oxygen saturation < 90% (r = 0.64, p < 0.005) and the lowest nocturnal SaO2 (r = 0.56, p < 0.05). Ventricular tachycardia was found in the early morning in one patient, ST-T depression in two patients, and sinus arrest in two patients in Group 2.

CONCLUSION

These findings suggest that sleep-disordered breathing associated with severe oxygen desaturation might influence heart rate variability not only during sleep but also during daytime. OSAS per se might contribute to altered circadian rhythm in autonomic activity leading to the development of cardiovascular diseases.

Twenty-four-hour ambulatory oxygen desaturation and electrocardiographic recording in obstructive sleep apnea syndrome

BACKGROUND

Although nocturnal pulseoximetry is routinely performed in obstructive sleep apnea syndrome (OSAS), pulseoximetry over a 24-h period has not been studied.

HYPOTHESIS

The purpose of the study was to determine whether simultaneous 24-h oxygen desaturation and electrocardiographic (ECG) recording might be used to screen for daytime sleep sequelae in patients with OSAS.

METHODS

Simultaneous recording of arterial oxygen saturation (SpO2) and ECG was conducted over a 24-h period in 18 male patients with OSAS (mean age 51.3 years) who were diagnosed by standard polysomnography (PSG), and in 15 age-matched healthy subjects (mean age 52.7 years) as controls to evaluate circadian variation of these parameters. The measures of heart rate variability (HRV) were calculated from 24-h ambulatory ECGs. Seventeen patients with OSAS showed excessive daytime sleepiness (EDS). We calculated the duration in which SpO2 decreased to < 90% (duration of SpO2 < 90%). The number of apnea/hypopneas per hour (AHI) during sleep was investigated with Apnomonitors (Chest MI, Co., Tokyo) on the same day as the SpO2 recordings.

RESULTS

Controls showed no episodes of oxygen desaturation. In patients with OSAS, driving (33.3% of patients with OSAS) was the most common activity in which SpO2 decreased to < 90%, followed by daytime napping (27.8%) and resting after meals (22.2%). The duration of SpO2 < 90% over a 24-h period correlated significantly with the duration levels recorded during sleep (r = 0.99, p < 0.05) and in the afternoon (r = 0.62, p < 0.05), and with the AHI (r = 0.55, p < 0.05), but not with the duration of SpO2 < 90% in the morning. The number of ventricular premature beats correlated significantly with the duration of SpO2 < 90% for a 24-h period, but not with measures of HRV. Ventricular tachycardia was found in two (11.1%) and ST-T depression in three patients (16.6%) with underlying cardiac diseases.

CONCLUSION

Our results suggest that daytime sleep attacks accompanied by oxygen desaturation in patients with moderate to severe OSAS may contribute to the occurrence of traffic or cardiovascular accidents. We conclude that 24-h ambulatory recordings of SpO2 and ECG are useful for screening for daytime sleep sequelae associated with the potential risk of this pathology in OSAS during social activities.

Long-term treatment of ischemic dilated cardiomyopathy with continuous positive airway pressure

An 81-year-old man with ischemic dilated cardiomyopathy complained of frequently awakening from sleep due to choking; subsequent polysomnography revealed Cheyne-Stokes respiration (CSR) with sleep apnea. With continuous positive airway pressure (CPAP) through a nasal mask, both the CSR and symptoms disappeared. After 6-12 months, chest X-ray and echocardiographic findings continued to improve without any change in pharmacological treatment. For three years, CPAP had been effective to eliminate CSR during sleep. Long-term CPAP treatment, which is rarely applied for congestive heart failure in Japan, is useful in alleviating the adverse effects of CSR and, thereby, maintaining a good quality of life in these patients.

Differential effects of hypoxia and hypercapnia on respiratory sinus arrhythmia in conscious dogs

To test the hypothesis that hypoxia and hypercapnia have different effects on the genesis of respiratory sinus arrhythmia (RSA), the magnitude of RSA to these stimuli was compared in 3 unanesthetized dogs. Respiration was continuously monitored through a permanent tracheostomy, and the electrocardiogram and blood pressure were also monitored. The magnitude of RSA was assessed as an instantaneous amplitude of the R-R interval oscillation in the high-frequency band of 0.15-0.80Hz by means of complex demodulation. In a total of 47 runs with hypoxia, heart rate, mean arterial pressure, respiratory rate and tidal volume increased, but RSA magnitude decreased even after adjusting for the effects of respiratory rate and tidal volume. In a total of 39 runs with hypercapnia, heart rate and mean arterial pressure did not change, despite the increased respiratory rate and tidal volume. In contrast to hypoxia, RSA magnitude increased even after adjusting for the effects of respiratory rate and tidal volume. The different effects of the two respiratory stimuli on RSA magnitude were noted at any level of ventilation and support the original hypothesis.

Row-a-boat phenomenon: respiratory compensation in advanced Duchenne muscular dystrophy

BACKGROUND

"Row-a-boat" phenomenon (RBP) is a spontaneous upper-body movement in patients with advanced Duchenne muscular dystrophy (DMD), when sitting upright supported by a belt around the body in a wheelchair. However, the role of RBP has not been clarified.

OBJECTIVES

To support the hypothesis that RBP is an abnormal pattern of respiration to compensate for the atrophied respiratory muscles in advanced DMD.

PATIENTS AND METHODS

Age, degree of ventilator dependency, and blood gas and spirometry values of 12 patients with spontaneous RBP were compared to those of 8 patients without RBP. All patients were men, and all exhibited a comparable level of motor function (unable to ambulate). Spirometry was undertaken with an ambulatory pneumotachograph in six patients with RBP in two conditions: sitting with RBP and sitting without RBP. In the latter condition, because a patient's shoulders, neck, and head were manually restricted, RBP was prevented.

RESULTS

We found that the patients with RBP were older (mean, 25.98 years vs 19.84 years), more dependent on mechanical ventilation (13.96 h/d vs 4.31 h/d), and had lower FVC and percentage of FVC (511.3 mL vs 762.5 mL and 13.37% vs 20.11%, respectively) than those without RBP. We also found that the frequency of RBP was identical with tidal breathing, and FVC was increased by 50.8% by simply allowing RBP.

CONCLUSION

We conclude that RBP is a respiratory movement to compensate for the atrophied respiratory muscles in advanced DMD.

Augmentation of respiratory sinus arrhythmia in response to progressive hypercapnia in conscious dogs

Respiratory sinus arrhythmia (RSA) may serve to enhance pulmonary gas exchange efficiency by matching pulmonary blood flow with lung volume within each respiratory cycle. We examined the hypothesis that RSA is augmented as an active physiological response to hypercapnia. We measured electrocardiograms and arterial blood pressure during progressive hypercapnia in conscious dogs that were prepared with a permanent tracheostomy and an implanted blood pressure telemetry unit. The intensity of RSA was assessed continuously as the amplitude of respiratory fluctuation of heart rate using complex demodulation. In a total of 39 runs of hypercapnia in 3 dogs, RSA increased by 38 and 43% of the control level when minute ventilation reached 10 and 15 l/min, respectively (P < 0.0001 for both), and heart rate and mean arterial pressure showed no significant change. The increases in RSA were significant even after adjustment for the effects of increased tidal volume, respiratory rate, and respiratory fluctuation of arterial blood pressure (P < 0.001). These observations indicate that increased RSA during hypercapnia is not the consequence of altered autonomic balance or respiratory patterns and support the hypothesis that RSA is augmented as an active physiological response to hypercapnia.

Impact of acute hypoxia on heart rate and blood pressure variability in conscious dogs

To examine whether the impacts of hypoxia on autonomic regulations involve the phasic modulations as well as tonic controls of cardiovascular variables, heart rate, blood pressure, and their variability during isocapnic progressive hypoxia were analyzed in trained conscious dogs prepared with a permanent tracheostomy and an implanted blood pressure telemetry unit. Data were obtained at baseline and when minute ventilation (VI) first reached 10 (VI10), 15 (VI15), and 20 (VI20) l/min during hypoxia. Time-dependent changes in the amplitudes of the high-frequency component of the R-R interval (RRIHF) and the low-frequency component of mean arterial pressure (MAPLF) were analyzed by complex demodulation. In a total of 47 progressive hypoxic runs in three dogs, RRIHF decreased at VI15 and VI20 and MAPLF increased at VI10 and VI15 but not at VI20, whereas heart rate and arterial pressure increased progressively with advancing hypoxia. We conclude that the autonomic responses to isocapnic progressive hypoxia involve tonic controls and phasic modulations of cardiovascular variables; the latter may be characterized by a progressive reduction in respiratory vagal modulation of heart rate and a transient augmentation in low-frequency sympathetic modulation of blood pressure.

Eight-year follow-up study of a patient with central alveolar hypoventilation treated with diaphragm pacing

We had treated a 17-year-old girl with central alveolar hypoventilation with diaphragm pacing at home for the past 8 years. Nocturnal diaphragm pacing with an open tracheostomy was effective in maintaining an adequate ventilation after 4 months of undergoing training of the diaphragm on the pacemaker implantation. However, the diaphragm pacemaker failed to maintain it mostly in the presence of respiratory tract infection, when she was treated with intermittent positive-pressure ventilation. Pulse oximetry was used at home for monitoring the adequacy of respiratory support. We conclude that the respiratory assistance by the diaphragm pacemaker or the use of a mechanical ventilator as a backup was highly useful for the home care of a patient with central alveolar hypoventilation.

Age related differences in electroencephalographic and cardiac arousal at the termination of sleep apnea/hypopnea

OBJECTIVE

The purpose of the present study was to determine whether electroencephalographic (EEG) and cardiac arousal, i.e. heart rate elevation at the termination of apnea/hypopnea are related to aging.

METHODS

The subjects were 13 middle-aged (40-60 years of age, 47.8+/-5.35 years) and 10 elderly (>60 years of age, 69.8+/-5.31 years) male patients with obstructive sleep apnea syndrome. We evaluated the number of apneas per an hour of sleep (apnea index: AI), the number of hypopneas per an hour of sleep (hypopnea index: HI), the summation of HI and AI (apnea/hypopnea index: AHI), sleep stage, the amount of time during which nocturnal oxygen saturation was decreased below 90% (oxygen desaturation time: ODT), and EEG and cardiac arousal at the termination of apnea/hypopnea using polysomnography with pulse oximetry.

RESULTS

There was no significant difference in AHI, duration of apnea/hypopnea, and sleep stage distribution between the two groups. However, the ratio of apnea/hypopnea with EEG and cardiac arousal was significantly higher in middle-aged than in elderly patients. The ratio of HI to AHI was significantly lower in middle-aged than in elderly patients. In middle-aged patients, EEG and cardiac arousal were significantly correlated with AI, AHI, and ODT, whereas, in elderly patients, these parameters were not similarly correlated.

CONCLUSION

Our findings suggest that the differences in EEG and cardiac arousal, and the pattern of sleep-disordered breathing (SDB) between middle-aged and elderly patients with SDB might be a physiological phenomenon of aging.

Influence of movement arousal on circadian rhythm of blood pressure in obstructive sleep apnea syndrome

OBJECTIVE

To investigate the hypothesis that repeated arousals at the termination of apnea/hypopnea in obstructive sleep apnea syndrome (OSAS) are related to abnormal circadian rhythm of blood pressure (BP).

DESIGN AND METHODS

We performed polysomnography (PSG) with pulse oximetry in 26 middle-aged patients with OSAS aged 42-58 years (mean age 51.8 years). The intensity of arousal on PSG was graded into two levels: grade 1 (EEG arousal, EA), an abrupt shift in EEG frequency, and grade 2 (movement arousal, MA), EEG arousal with an increase in electromyogram activity lasting at least 3 s. The number of apnea/hypopneas per hour (apnea/hypopnea index, AHI), and length of time during which nocturnal oxygen saturation decreased below 90% (oxygen desaturation time, ODT) were also evaluated. Percentage EA and %MA were assessed by the ratio of the number of apneas and hypopneas with EA or MA to the number of apneas and hypopneas in total. The 24 h systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured noninvasively. Multiple regression analysis was performed among AHI, ODT, %EA and %MA or among age, body mass index and %MA.

RESULTS

The %MA was the most significant factor contributing to the elevated 24 h SBP (r= 0.46, P< 0.05); oxygen desaturation (r= 0.44, P< 0.05) was the next most important contributing factor. The level and pattern of 24 h BP differed significantly between the patients with %MA 85% and %MA < 85% (mean 24 h SBP: 147 +/- 16.8 versus 125 +/- 19.6 mmHg, P< 0.01; mean 24 h DBP: 97.5 +/- 14.3 versus 85.6 +/- 14.6 mmHg, P< 0.01), and also differed between those with severe OSAS, i.e. ODT > or = 130 min, and mild to moderate OSAS, i.e. ODT < 130 min, (mean 24 h SBP: 149 +/- 15.8 versus 132 +/- 20.6 mmHg, P < 0.01; mean 24 h DBP: 100 +/- 14.1 versus 87.4 +/- 14.0 mmHg, P < 0.01).

CONCLUSION

Our findings suggest that MA and oxygen desaturation in OSAS make an important contribution to abnormal circadian rhythm of BP. We conclude that repeated end-apneic arousal and/or hypoxic asphyxia and the subsequent sleep fragmentation may contibute to nocturnal and diurnal elevation of BP.

[Evaluation of cranial CT findings of patients with muscular dystrophy: with a reference to cerebral vascular disease and cardiac complications]

We evaluated cranial CT findings of 160 patients with various type of progressive muscular dystrophy (PMD). Significant brain atrophy was observed in 21 out of 63 cases of Duchenne muscular dystrophy (DMD), 7 out of 15 Becker muscular dystrophy (BMD), no case of 2 female dystrophinopathy (F-dyst), 11 out of 21 limb-girdle muscular dystrophy (LG), all cases of 10 Fukuyama type congenital muscular dystrophy (FCMD), 2 out of 5 fascioscapulohumeral muscular dystrophy (FSH), and 32 out of 44 myotonic dystrophy (MyD). Genetical degenerative process and vascular insufficiency seemed to cause brain atrophy in these disease. The intracranial calcification was observed in one DMD, one LG and seven MyD. One LG patient showed focal atrophy in left temporal lobe, and one MyD demonstrated right temporal meningioma. The trace of cerebral vascular accident was disclosed in eleven patients with PMD (1 DMD, 2 BMD, 1 F-dyst, 2 LG, 5 MyD). In these cases, 2 patients had dilated cardiomyopathy, 6 patients with decreased left ventricular ejection fraction, 3 with atrial fibrillation, 1 with cardiac arrest followed by pacemaker instillation, 1 with Adam-Stokes attack, and 3 with 1 degree AV-block. Diffuse low density in the white matter was seen in a patient with F-dyst, a FCMD patient, and 8 MyD patients. Cardiac emobolism, severe arrythmia, cardiogenic shock and hemodynamic disorder were seemed to cause cerebral vascular disease in PMD.

[A patient of polymyositis with severe myocardial damage and conduction block]

A patient with polymyositis manifesting severe myocardial damage and conduction block is described. A 57-year-old man presented dysarthria, dysphagia, proximal-dominant muscle weakness and wasting of the extremities. Muscle biopsy revealed degeneration and regeneration of muscle fibers and infiltration of mononuclear cells. After admission, muscle weakness rapidly progressed and mechanical ventilation was needed for respiratory failure. Simultaneously, cardiac symptom developed and resulted in bradycardia and trifascicular conduction block, which required a pacemaker. Echocardiogram revealed diffuse hypokinesia, ventricular enlargement and thickened wall. Marked elevations of serum CK-MB, cardiac myosin light chain I and cardiac troponin T were observed. High dose administration of methylprednisolone resulted in improvement of muscular and cardiac symptoms, and prevented complete heart block. Immediate and high dose of steroid therapy was considered to be effective for severe myocarditis in polymyositis.

Prognosis of the middle-aged and aged patients with obstructive sleep apnea syndrome

The long-term natural course of obstructive sleep apnea syndrome (OSAS) is studied in order to determine whether severity of nocturnal oxygen desaturation associated with apnea/hypopnea, body mass index (BMI), and hypertension influence survival in young (<40 years), middle-aged (40-64 years), and aged (> or = 65 years) using a questionnaire survey. One hundred and forty-eight patients with OSAS aged 17-78 years (136 men, 12 women, mean 52.0+/-12.3 years), who were diagnosed by standard polysomnography (PSG) between 1983 and 1993, participated in the study. The survey revealed 15 deaths and 101 survivors; 32 subjects could not be located. The survival rate was 71.4% (95% confidence interval: 55.6-87.2%). The survival rate in patients with OSAS was significantly lower than that in the age and sex-adjusted control Japanese population (87.6%). In the young group, only one death (a 19-year-old woman) occurred unexpectedly during sleep. The patient showed an apnea/hypopnea index (AHI) of 33 per h and the length of time that the nocturnal oxygen saturation (SaO2) fell below 90% (time of SaO2 <90%) of 205 min. The survival rate in middle-aged patients with OSAS was significantly lower than that in the age and sex-adjusted control Japanese population (79.2 vs 91.0%), but this pattern was not seen among the aged. Time of SaO2 <90% was significantly longer in the middle-aged patients than in the aged patients, but AHI did not differ between the two groups. Moreover, it was significantly correlated with AHI in middle-aged patients, but not in the aged patients. The survival rate was significantly lower in patients with hypertension than in the patients without such complications in the middle-aged group (57.9 vs 90.4%). Cox proportional-hazard regression model including age, hypertension, BMI, AHI, lowest SaO2, and time of SaO2 <90% showed that hypertension was only significantly associated with lower survival rate in total group and middle-aged patients, but not in the young or aged patients. The prognosis in patients with OSAS may differ among the generations. The prognosis in the middle-aged population may depend on the role of OSAS on the complications of hypertension or severity of oxygen desaturation, but not on AHI only.

Recording of electroencephalograms and electrocardiograms during daytime sleep in trained canines: preparation of the sleeping dogs

Although respiration in trained canines is well investigated, the process of preparing dogs has not been described in any great detail. Moreover, their daytime patterns of sleep and wakefulness during 1 or 2 h of electroencephalogram (EEG) and electrocardiogram (ECG) recordings are not clear. Therefore, we describe the process of selecting and training dogs, in which we recorded EEG and ECG in the laboratory. First, 14 of 1242 dogs dealt with over a 1 year period were chosen. They were trained for 2 h to lie quietly and to sleep in the laboratory; this training procedure was repeated 152 times. Three dogs were then selected and a permanent tracheostomy was performed in one. Finally, EEG and ECG were recorded with the bipolar fine needle electrodes; respiration was recorded simultaneously through a tube inserted to a tracheostomy in one dog. Wakefulness, slow wave sleep (SWS) and rapid eye movement (REM) sleep (REMS) were identified according to the EEG pattern and on the basis of the behavioral criteria. Recordings were performed 12 or 13 times in each dog. Complete sleep cycles, including wakefulness, SWS and REMS in this sequence, were observed 3.9-4.1 times. The mean duration of SWS was 2.2-4.4 min and that of REMS was 3.5-4.6 min. The REMS latency was 33.9-41.8 min. Fluctuation of heart rate with respiration, termed respiratory sinus arrhythmia, was noted in the ECG. Heart beat increased with inspiration and decreased with expiration. The present study demonstrates how to select and train sleeping dogs and shows their undisturbed daytime sleep and wakefulness patterns.

Suppressed cardiac and electroencephalographic arousal on apnea/hypopnea termination in elderly patients with cerebral infarction

The goal of the present investigation is to show the clinical significance of arousal response at termination of apnea/hypopnea in patients with sleep apnea syndrome (SAS) after cerebral infarction. We polygraphically assessed "cardiac arousal," which is defined as an abrupt increase in heart rate at a termination of sleep apnea/hypopnea, and electroencephalographic (EEG) arousal. There were six elderly subjects, bedridden after cerebral infarction, with SAS aged 71-87 years (mean 72.3 years) and 11 age-matched patients with SAS aged 61-78 years (mean 62.3 years) as controls. The following sleep parameters were measured: number of apneas per hour (apnea index [AI]), number of hypopneas per hour (hypopnea index [HI]), summation of the two (apnea/hypopnea index [AHI]), and duration in which nocturnal oxygen saturation was decreased below 90% (duration of SaO2 < 90%). We calculated the ratio of apnea/hypopnea per hour with cardiac arousal to total apnea/hypopneas (XI) (% cardiac arousal [XI/AHI x 100]) and the ratio of that with EEG arousal (YI) (% EEG arousal [YI/AHI x 100]). Between the two groups, we found no significant difference in body mass index, the ratio of central apnea to total apnea/hypopnea, AHI, duration of apnea/hypopnea, lowest SaO2, and duration of SaO2 < 90%. Compared with controls, % cardiac and % EEG arousals were significantly lower in patients with cerebral infarction. In contrast, the ratio of HI to AHI was significantly higher in patients with cerebral infarction than in control subjects. Our findings indicate that cardiac and EEG arousals at termination of apnea/hypopnea are significantly suppressed in elderly patients with SAS after cerebral infarction, which may provide useful information on the pathophysiology of SAS in patients with cerebrovascular disease.

Ultra-low-field magnetic resonance imaging in upper airways obstruction in sleep apnea syndrome

The hypothesis that the sites of upper airways obstruction (UAO) are varied in a patient with obstructive sleep apnea syndrome (OSAS) among different sleep stages is studied. Four patients with OSAS underwent ultra-low-field magnetic resonance imaging (MRI) with a field strength of 0.064 Tesla provided real-time images and generated less noise and necessitated less strict magnetic isolation compared with conventional high-field MRI. After the fixed end-apneic sleep stage was determined, the polysomnogram was switched off and ultra-low-field MRI was commenced. The effects of continuous positive airway pressure (CPAP) on the upper airway patency in the deepest sleep stage obtained for each patient was assessed. Upper airway obstruction was found at the level of the palatopharynx (PP) at sleep onset extended to the glossopharynx (GP) during rapid eye movement (REM) sleep in two cases and during NREM sleep in one case. This combined PP and GP obstruction was observed from sleep onset and remained unchanged in one case. The patent upper airways were observed during treatment with CPAP during REM sleep in two patients and during stage two of NREM sleep in the other two patients. It can be concluded that the sites of UAO vary in a patient with OSAS in different sleep stages. The results also suggest the use of the ultra-low-field MRI in order to visualize the dynamic and real-time behaviors of the upper airways during sleep in patients with OSAS.

Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency

BACKGROUND

The primary mechanisms of respiratory sinus arrhythmia (RSA) are understood to be the modulation of cardiac vagal efferent activity by the central respiratory drive and the lung inflation reflex, and the degree of RSA increases with cardiac vagal activity. However, it is unclear whether RSA serves an active physiological role or merely reflects a passive cardiovascular response to respiratory input. We hypothesized that RSA benefits pulmonary gas exchange by matching perfusion to ventilation within each respiratory cycle.

METHODS AND RESULTS

In seven anesthetized dogs, a model stimulating RSA was made. After elimination of endogenous autonomic activities, respiration-linked heartbeat fluctuations were generated by electrical stimulation of the right cervical vagus during negative pressure ventilation produced by phrenic nerve stimulation (diaphragm pacing). The vagal stimulation was performed in three conditions; phasic stimulation during expiration (artificial RSA) and during inspiration (inverse RSA) and constant stimulation (control) causing the same number of heartbeats per minute as the phasic stimulations. Although tidal volume, cardiac output, and arterial blood pressure were unchanged, artificial RSA decreased the ratio of physiological dead space to tidal volume (VD/VT) and the fraction of intrapulmonary shunt (Qap/Qt) by 10% and 51%, respectively, and increased O2 consumption by 4% compared with control. Conversely, reverse RSA increased VD/VT and Qap/Qt by 14% and 64%, respectively, and decreased O2 consumption by 14%.

CONCLUSIONS

These results support our hypothesis that RSA benefits the pulmonary gas exchange and may improve the energy efficiency of pulmonary circulation by "saving heartbeats."

Cardiac hypertrophy in obstructive sleep apnea syndrome

Fifty-one middle-aged male patients with obstructive sleep apnea syndrome (OSAS) were evaluated using two-dimensional echocardiography, 24-h blood pressure measurements, polysomnography, and plasma norepinephrine (NE) measurements. Among these patients, left ventricular hypertrophy (LVH) (left ventricular posterior wall thickness [LVPWT] or interventricular septal thickness [IVST] > or = 12 mm) and right ventricular hypertrophy (RVH) (right ventricular wall thickness [RVT] > or = 5 mm) were present in 41.2% (21/51) and 11.8% (6/51). LVH was present in 50.0% of group 2 patients (apnea index > or = 20) and in 30.5% of group 1 patients (apnea index < 20). All patients with LVH had hypertension. RVH was present in 21.4% of group 2 patients and none of the group 1 patients. IVST, LVPWT, LV mass, LV mass/body surface area (BSA), and obesity index were significantly greater in group 2 than in group 1. Apnea index and the duration in which nocturnal oxygen saturation was decreased under 90% (duration of SaO2 < 90%), were significantly correlated with LV mass/BSA and 24-h mean blood pressure. Apnea index, number of apneas, duration of nocturnal oxygen saturation less than 90%, weight, and obesity index were significantly greater in patients with both LVH and RVH than in patients without LVH and RVH, or those with only LVH. Plasma NE after waking significantly increased compared with that before sleep (p < 0.05). The ratio of plasma NE levels after waking to those before sleep was significantly correlated with the duration of SaO2 < 90% (r = 0.83, p < 0.05), but not with apnea index. These results suggest that frequent episodes of oxygen desaturation and/or arousal responses caused by apnea may contribute to the complication of LVH and RVH in the long term, and apnea-induced cyclical increases in blood pressure and the resulting sustained elevation in blood pressure associated with the increase in afterload and sympathetic activity may play a role in the development of LVH.

A case of mitral regurgitation whose nocturnal periodic breathing was improved after mitral valve replacement

Nocturnal periodic breathing (PB) is often observed in patients with congestive heart failure (CHF). We investigated the sleep architecture polysomnographically in a 54-year-old man with CHF due to mitral regurgitation before and after surgical treatment. We found that the overnight frequency of central dominant sleep apnea decreased from 154 to 56, and the lowest nocturnal oxygen saturation increased from 66% to 85% postoperatively. These improvements in the manifestations of PB might be attributed to the improved hemodynamics after successful valve replacement.

24-hour ambulatory blood pressure variability in obstructive sleep apnea syndrome

The 24-h ambulatory blood pressure (24h-ABP) was examined in 21 men, aged 38 to 65 years (mean 50.6), with obstructive sleep apnea syndrome (OSAS) and in 123 normal male control subjects, aged 40 to 60 years (mean 48.1) who did not have OSAS, obesity, autonomic nervous system abnormality, cardiac disease, or respiratory disease (group C), to assess the role of apneas in the circadian variation of blood pressure (BP). The 24h-ABP patterns in OSAS patients were classified into three types as follow: normotensive OSAS patients with normal BP throughout the 24-h period with nocturnal BP fall (type 1); hypertensive OSAS patients with progressive BP elevation from onset of sleep to early morning (type 2); and hypertensive OSAS patients with elevated BP (systolic BP > or = 140 mm Hg or diastolic BP > or = 90 mm Hg) at any time during a 24-h period (type 3). It was concluded that the circadian BP variation in type 1 was almost identical to the level and pattern of group C; the circadian variations in types 2 and 3 were significantly different from that of group C; and the patients with types 2 and 3 BP patterns had more severe OSAS than type 1 patients. The severity of OSAS was an important factor in nocturnal elevation of BP, hence affecting the circadian variation of BP. Noninvasive 24h-ABP monitoring is a useful procedure for understanding the clinical features of OSAS patients with or without hypertension.

Effect of inspiratory muscle unloading on arousal responses to CO2 and hypoxia in sleeping dogs

Chemical respiratory stimuli can induce arousal from sleep, but the specific mechanisms involved have not been established. Therefore, we tested the hypothesis that mechanoreceptor stimuli arising in the ventilatory apparatus have a role in the arousal responses to progressive hypercapnia and hypoxia by comparing arousal responses during spontaneous ventilation with those obtained when the inspiratory muscles were unloaded by mechanical ventilatory assistance. Studies were performed in three trained dogs in which the adequacy of inspiratory muscle unloading was verified by diaphragmatic electromyographic (EMG) recordings. In rapid-eye-movement (REM) sleep the arousal threshold during progressive hypercapnia increased from 68.4 +/- 0.5 (SE) mmHg during spontaneous runs to 72.3 +/- 0.8 mmHg during mechanically assisted runs (P < 0.01). In contrast there were no changes in arousal responses to hypercapnia during non-REM (NREM) sleep or to hypoxia in either NREM or REM sleep. However, during the assisted hypoxic runs, EMG activity of the transversus abdominis muscle was increased compared with the unassisted runs; therefore, the effects on arousal threshold of unloading the inspiratory muscles may have been offset by increased loading of the expiratory muscles. The findings indicate that even in the absence of added mechanical loads, mechanoreceptor stimuli probably arising in the respiratory muscles contribute to the arousal response to hypercapnia during REM sleep.

Abdominal muscle activation by respiratory stimuli in conscious dogs

The responses of the diaphragm, external oblique, and transversus abdominis muscles to hyperoxic hypercapnia and isocapnic hypoxia were studied in four awake dogs to test the hypothesis that central and peripheral chemoreceptor inputs result in different patterns of respiratory muscle activation. The dogs were trained to lie quietly in place, and electromyographic (EMG) discharges of the diaphragm (EMGdi), external oblique (EMGeo), and transversus abdominis (EMGta) were recorded from chronically implanted electrodes. Both hypercapnia and hypoxia recruited EMGeo and EMGta activity, but at comparable levels of minute volume of ventilation the EMG activity of the abdominal muscles was greater during hypercapnia than during hypoxia. However the two chemical stimuli also resulted in different tidal volume (VT) and respiratory frequency responses at any given minute volume of ventilation. When EMG activity was reanalyzed as a function of VT, EMGeo and EMGta were the same for a given VT whether induced by hypercapnia or hypoxia, but EMGdi was consistently greater during hypoxia than during hypercapnia. When the vagus nerves were blocked by cooling exteriorized cervical vagal loops, all abdominal muscle EMG activity was abolished. The findings support the concept that stimulation of the central and peripheral chemoreceptors results in asymmetric activation of the inspiratory and expiratory respiratory muscles. The findings also indicate that afferent vagal stimuli play an important facilitatory role in activation of the abdominal expiratory muscles.

Interaction of chemical and mechanical respiratory stimuli in the arousal response to hypoxia in sleeping dogs

The role of respiratory mechanoreceptor stimuli in the arousal response to hypoxia was studied in three trained dogs. The dogs breathed through a cuffed endotracheal tube inserted through a chronic tracheostomy, and resistive loads of 8 to 49 cm H2O/L/s were added to the expiratory circuit. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and isocapnic progressive hypoxia was induced by a rebreathing technique. Arousal from sleep was determined by electroencephalographic and behavioral criteria. SaO2 at arousal from non-rapid eye movement (NREM) sleep increased progressively from 67.5 +/- 4.6% (mean +/- SEM), with no added resistance to 85.2 +/- 0.5% with the highest resistance (p less than 0.01), and from 60.6 +/- 0.6 to 81.6 +/- 0.4% during REM sleep (p less than 0.01). The added resistances also increased the steady-state (normoxic) level of alveolar PCO2 (PACO2). However, when PACO2 was increased to comparable levels by the addition of dead space rather than expiratory resistance to the breathing circuit, SaO2 at arousal from hypoxia was significantly lower than during expiratory resistive loading (p less than 0.05). We therefore conclude that mechanoreceptor stimuli arising from the ventilatory apparatus may contribute substantially to the arousal response to hypoxia.

Effects of vasodilators on venous tone in vivo in dogs

The authors investigated, in vivo, the effects of four vasodilators on venous tone in dogs. Baseline venous tone was determined from the pressure: diameter relationships in the inferior vena cava (VSIVC) and femoral vein (VSFV) as measured during several seconds of occlusion of the proximal inferior vena cava. All of the slopes were nearly linear. All vasodilators were administered in dosages sufficient to lower blood pressure by approximately 20%; these dosages also decreased systemic vascular resistance by 15% to 30%. Isosorbide dinitrate reduced VSIVC from 7.17 +/- 0.81 to 5.81 +/- 0.73 mmHg/mm and VSIVC from 59.4 +/- 13.5 to 37.2 +/- 6.6 mmHg/mm. Neither nifedipine nor nisoldipine altered VSIVC or VSFV. However, prazosin decreased VSIVC from 13.2 +/- 3.3 to 10.7 +/- 2.7 mmHg/mm and VSFV from 43.5 +/- 11.3 to 29.9 +/- 8.8 mmHg/mm. These results suggest that isosorbide dinitrate and prazosin decrease venous tone in vivo, whereas nifedipine and nisoldipine do not.

[Heart rate changes in sleep apnea syndrome]

Sleep apnea syndrome (SAS) is often associated with arrhythmias. The study was performed to clarify the characteristics and mechanisms of the heart rate (HR) changes during and after sleep induced apneas. Thirty-one patients with SAS without definitive heart disease, aged 17-78 years (mean 54.2 years), were examined by electroencephalograms, electrocardiograms, electrooculograms, nasal and oral breathing, thoracic and abdominal respiratory movements and arterial oxygen saturation (SaO2). [Results and Discussion] At the onset of sleep apnea, some showed progressive reductions in HR, followed by abrupt tachycardia on the resumption of breathing. Thirty-one patients with SAS were classified into three Groups (A, B, C). Group A demonstrated that HR changes occurred associated with apnea both in stage REM and in stage non-REM. Group B demonstrated that HR changes occurred associated with apnea only in stage REM. Group C demonstrated that HR changes did not occur associated with apnea. In Group A, apnea frequency and apnea index were higher than those of Group C. In Group A, the lowest SaO2 was lower than that of Group C, total time under 90% of arterial oxygen saturation (SaO2) was longer than that of Group C. There was a good negative correlation between oxygen saturation and HR changes. Further, HR changes were augmented by arousal response. This might be related to the arousal response as well as to the cardiostimulatory effects of hypoxia associated with increased ventilation. The arousability in response to apneas might be important in HR changes. In SAS, the degree of HR changes was related to apnea frequency, apnea index, apnea length and sleep stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Breathing abnormalities during sleep in patients with chronic heart failure

Polysomnography was carried out in 11 adult outpatients with stable chronic heart failure (CHF) due to valvular heart disease in order to investigate respiratory abnormalities during sleep. The subjects consisted of 6 males and 5 females and their ages ranged from 54 to 76 years. A coexisting central dominant sleep apnea syndrome (SAS) was found in 4 males, 3 of whom had evidence of nasal obstruction. A successful mitral valve replacement in one patient with central dominant SAS was associated with a reduction in the frequency of sleep apnea. The results suggest complications caused by respiratory abnormalities during sleep are common and should be considered in the management of patients with CHF.

[Hemodynamic study of negative pressure ventilation using diaphragm pacing]

A negative pressure ventilation (NPV) by unilateral or bilateral diaphragm pacing (DP) was prepared for canine experiments. A shift from positive pressure ventilation (PPV) to NPV resulted in elevation of mean aortic pressure, increase in stroke volume and depression of mean pulmonary arterial pressure. Examination of the interaction between respiratory cycle and cardiac function during PPV, disclosed a reduction of right ventricular stroke volume and elevation of mean aortic and right ventricular end-diastolic pressure at end inspiration, compared to those at end expiration. During NPV with DP, left ventricular stroke volume, heart rate and mean aortic pressure were increased immediately after DP (immediately after inspiration) compared to those at end expiration. The experimental model of DP, in which respiratory condition could be easily altered, was considered to be useful to evaluate the effect of NPV on cardiac function.

Retinal embolism from left atrial myxoma

Retinal artery embolism that had arisen as a complication of a left atrial myxoma was diagnosed in a young man who had suddenly developed a visual disorder in his left eye. A tumor in the left atrium was surgically excised. Pathologically, retinal embolism secondary to atrial myxoma is rare. To our knowledge, only 15 cases have been documented so far. The present case was only the second case of an isolated retinal embolism that had developed without systemic involvement, and the first case of retinal artery branch embolism that had resulted from a left atrial myxoma.

[Two cases of cardiac tamponade, complicated by malignant, effusive pericarditis and treated by creating a pericardial peritoneal window]

Reported are two cases of a cardiac tamponade complicated by a malignant, effusive pericarditis were treated by a pericardial, peritoneal window. In both cases, a reaccumulation of pericardial fluid was noticed, within a month after percutaneous, continuous pericardial drainage, and a tumor invasion was seen to the anterior mediastinum creating a pericardial, peritoneal window was considered useful for the treatment of the cardiac tamponade, secondary to the malignant, effusive pericarditis.

Congenital central alveolar hypoventilation (Ondine's curse): a case report and review of the literature

Congenital central alveolar hypoventilation (C-CAH), so called Ondine's curse, is known to be quite a rare neuropathology that has been reported in only 23 cases to date. C-CAH was diagnosed in a 2-year-5-month-old infant. In the treatment of C-CAH, we implanted a right unilateral diaphragm pacemaker in the infant and his respiratory status was remarkably improved after diaphragm pacing. Twenty-three reported cases of this disorder are reviewed in the literature.

The changes in regional myocardial surface area during coronary occlusion and reperfusion

For the analysis of regional myocardial function, the measurement of regional myocardial surface area (RMA) was performed on the epicardial surface of myocardial segment lengths in a direction parallel to the superficial myocardial fibers (SLa) and at right angles to the first (SLb). In eight anesthetized dogs with opened-chests, measurements were done during a 60 s left anterior descending coronary artery occlusion and reperfusion. In the ischemic region, coronary occlusion resulted in dyskinesis in RMA, and the reduction of it during the ejection phase (ERA) decreased significantly at 10 s (p less than 0.05) and thereafter (p less than 0.01). Regional myocardial work (EWA) from the pressure-area loops during the ejection phase also decreased significantly at 10 s (p less than 0.05) and thereafter (p less than 0.01). The end-diastolic RMA (EDRMA) increased significantly at 30 s (p less than 0.01) and thereafter (p less than 0.01). In the non-ischemic region, compensatory changes were shown, namely ERA, EWA and EDRMA, increased significantly during occlusion. After reperfusion, recovery to the control level was prompt, and only EDRMA remained the increased value after 30 s (p less than 0.01). Between SLa and SLb, characteristics differed from each other, which suggested that the directional differences of SLs should be considered when regional myocardial function is assessed from unidirectional SL. The changes in RMA reflect both changes of SLa and SLb during coronary occlusion and reperfusion, and were more marked than each SL. Thus, the usefulness of RMA to assess regional myocardial function was demonstrated during coronary occlusion and reperfusion.

[Central alveolar hypoventilation as a complication of massive intracerebellar hemorrhage: report of a case treated by diaphragm pacing]

The author reported a case of central alveolar hypoventilation (Ondine's curse) which was treated by diaphragm pacing. A 59-year-old man was admitted because of sudden deep coma and tetraparesis. Neurological examination on admission showed miotic pupils with absent light reaction, no oculocephalic reflex, no corneal reflex and tetraparesis. Glasgow scale was evaluated to be E-1 V-1, and M-3 with total of 5 points. Computed tomography confirmed a large hematoma in the cerebellum with ventricular rupture. Immediately, a suboccipital craniectomy was performed and the hematoma was evacuated. His neurological condition was improved gradually within a month after the operation. He responded to verbal orders and moved all his limbs against gravity. His respiration, however, was irregular with a pattern of so-called "cluster breathing" followed by prolonged apnea, that was more pronounced in night. He was suffered from hypoxic hypercapnea and recurrent pneumonia. Therefore, authors decided to employ diaphragm pacing for management of central alveolar hypoventilation. A diaphragm pacemaker (radiofrequency induction) was implanted. A cuff electrode was put around the right phrenic nerve in the right thorax, and the receiver installed subcutaneously in the right anterior chest. Postoperative respiratory study showed ventilation on pacing with satisfactory blood gas and he became able to move around using a wheel chair. In 1966 Glenn demonstrated a new technique to move the diaphragm paced by a receiver through the phrenic nerve, triggered by radio wave from external device.(ABSTRACT TRUNCATED AT 250 WORDS)

[Treatment of post-infarction ventricular septal perforation]

Recently clinical course of ventricular septal perforation following myocardial infarction is made clear. It is concluded that postinfarction ventricular septal perforation constitutes a surgical emergency. However, cardiac function of these patients are not fully evaluated, as full-cardiac catheterization including coronary angiography is hazardous. The timing of surgical intervention must be determined according to the non-invasive evaluation such as echocardiogram. In this report, we review our experience with postinfarction ventricular septal perforation and attempt to determine from this review the management of these patients. Our cases are classified into three categories. Group 1 showed cardiogenic shock state after onset of ventricular septal perforation. Group 2 had severe congestive heart failure and required inotropic support. Group 3 had moderate congestive heart failure. Group 1 need emergency operation. Group 2 need intraaortic balloon support and respiratory support after the onset. After then surgical intervention should be considered. Group 3 can be operated on more than 6 weeks after myocardial infarction on an elective basis.