Long-term use of occlusal appliance has impact on sleep structure.

Acrylic occlusal appliances (OAs) have been used for temporomandibular disorders and sleep bruxism, but the effects of the treatment are still insufficiently evaluated. Two all-night polysomnographic recordings were made in a sleep laboratory on 14 bruxists (9 females and 5 males with mean age of 27·5 years). The measurement included basic polysomnography with additional masseter muscle electromyogram and movement recording (static charge-sensitive bed method) using randomisation. The base night recording was followed by the second study night after 8 weeks regular use of OA. The OA was made on the occlusal surface of the teeth of the upper jaw, and it was used at night time during the study period. With the OA, rapid eye movement sleep changed from 23·3% to 19·6% (P = 0·078), and slow wave sleep increased significantly from 10·2% to 14·7% (P = 0·039). Masseter contraction (MC) episodes occurred with similar frequency (9·7 vs. 10·5 episodes per hour, P = 0·272). The intensity of the rhythmic MC bursts within an episode decreased from 5·5 to 4·4 (P = 0·027). The groups were post hoc divided into responders and non-responders using a 20% change in MC episode per hour as a cut-off point. The results indicated that 43% of bruxists increased activity (negative responders), while 36% decreased (positive responders), and in 21%, there was no change in the level. It is concluded that OA does not have significant feedback inhibition on masseter muscle motor activity during sleep. However, OA may increase slow wave sleep.

Tracheal sound parameters of respiratory cycle phases show differences between flow-limited and normal breathing during sleep.

The objective of the present work was to develop new computational parameters to examine the characteristics of respiratory cycle phases from the tracheal breathing sound signal during sleep. Tracheal sound data from 14 patients (10 males and 4 females) were examined. From each patient, a 10 min long section of normal and a 10 min section of flow-limited breathing during sleep were analysed. The computationally determined proportional durations of the respiratory phases were first investigated. Moreover, the phase durations and breathing sound amplitude levels were used to calculate the area under the breathing sound envelope signal during inspiration and expiration phases. An inspiratory sound index was then developed to provide the percentage of this type of area during the inspiratory phase with respect to the combined area of inspiratory and expiratory phases. The proportional duration of the inspiratory phase showed statistically significantly higher values during flow-limited breathing than during normal breathing and inspiratory pause displayed an opposite difference. The inspiratory sound index showed statistically significantly higher values during flow-limited breathing than during normal breathing. The presented novel computational parameters could contribute to the examination of sleep-disordered breathing or as a screening tool.

Intelligent methods for identifying respiratory cycle phases from tracheal sound signal during sleep.

We present two methods for identifying respiratory cycle phases from tracheal sound signal during sleep. The methods utilize the Hilbert transform in envelope extraction. They determine automatically a patient-specific amplitude threshold to be used in the detection. The core of one method is designed to be amplitude-independent whereas the other method uses solely the amplitude information. The methods provided average sensitivities of 98% and 99%, respectively, and positive prediction values of 100% on the total of 1434 respiratory cycles analysed from six different patients. The developed methods seem promising as such or as tools for analysing sleep disordered breathing.

High frequency components of tracheal sound are emphasized during prolonged flow limitation.

A nasal pressure transducer, which is used to study nocturnal airflow, also provides information about the inspiratory flow waveform. A round flow shape is presented during normal breathing. A flattened, non-round shape is found during hypopneas and it can also appear in prolonged episodes. The significance of this prolonged flow limitation is still not established. A tracheal sound spectrum has been analyzed further in order to achieve additional information about breathing during sleep. Increased sound frequencies over 500 Hz have been connected to obstruction of the upper airway. The aim of the present study was to examine the tracheal sound signal content of prolonged flow limitation and to find out whether prolonged flow limitation would consist of abundant high frequency activity. Sleep recordings of 36 consecutive patients were examined. The tracheal sound spectral analysis was performed on 10 min episodes of prolonged flow limitation, normal breathing and periodic apnea-hypopnea breathing. The highest total spectral amplitude, implicating loudest sounds, occurred during flow-limited breathing which also presented loudest sounds in all frequency bands above 100 Hz. In addition, the tracheal sound signal during flow-limited breathing constituted proportionally more high frequency activities compared to normal breathing and even periodic apnea-hypopnea breathing.

New tracheal sound feature for apnoea analysis.

Sleep apnoea syndrome is common in the general population and is currently underdiagnosed. The aim of the present work was to develop a new tracheal sound feature for separation of apnoea events from non-apnoea time. Ten overnight recordings from apnoea patients containing 1,107 visually scored apnoea events totalling 7 h in duration and 72 h of non-apnoea time were included in the study. The feature was designed to describe the local spectral content of the sound signal. The median, maximum and mean smoothing of different time scales were compared in the feature extraction. The feature was designed to range from 0 to 1 irrespective of tracheal sound amplitudes. This constant range could offer application of the feature without patient-specific adjustments. The overall separation of feature values during apnoea events from non-apnoea time across all patients was good, reaching 80.8%. Due to the individual differences in tracheal sound signal amplitudes, developing amplitude-independent means for screening apnoea events is beneficial.

Detection of compressed tracheal sound patterns with large amplitude variation during sleep.

The objective of the present work was to develop automated methods for the compressed tracheal breathing sound analysis. Overnight tracheal breathing sound was recorded from ten apnoea patients. From each patient, three different types of tracheal sound deflection pattern, each of 10 min duration, were visually scored, viewing the compressed tracheal sound curve. Among them, high deflection patterns are of special interest due to the possible correlation with apnoea-hypopnoea sequences. Three methods were developed to detect patterns with high deflection, utilizing nonlinear filtering in local characterization of tracheal sounds. Method one comprises of local signal maximum, the second method of its local range, and the third of its relative range. The three methods provided 80% sensitivity with 57, 91 and 93% specificity, respectively. Method three provided an amplitude-independent approach. The nonlinear filtering based methods developed here offer effective means for analysing tracheal sounds of sleep-disordered breathing.

Prolonged spiking in the Emfit sensor in patients with sleep-disordered breathing is characterized by increase in transcutaneous carbon dioxide.

A phenomenon of prolonged spiking in movement sensors, such as static-charge-sensitive bed or Emfit (electromechanical film) sensors, has been connected to an increase in carbon dioxide tension in wakefulness. Spiking is also a common finding in sleep studies. This made us hypothesize that carbon dioxide changes might also happen in sleep during prolonged spiking episodes in Emfit sheet. We examined four different kinds of breathing pattern episodes: normal breathing, episodes of repetitive apnea, episodes of repetitive hypopnea and episodes with prolonged spiking lasting at least 3 min. One hundred and fifteen episodes from 19 polysomnograms were finally admitted to the study according to the protocol. The changes in the transcutaneous carbon dioxide tension (TcCO(2)) were defined for different breathing patterns. During prolonged spiking episodes the TcCO(2) increased significantly and differed statistically from the TcCO(2) changes of normal breathing and periodic breathing patterns (episodes of apnea and hypopnea). The rise in TcCO(2) during prolonged spiking episodes might suggest that prolonged spiking is representing another type of breathing disturbance during sleep differing from periodic breathing patterns. The Emfit sensor as a small, flexible and non-invasive sensor might provide useful additional information about breathing during sleep.

Climacteric vasomotor symptoms do not predict nocturnal breathing abnormalities in postmenopausal women.

OBJECTIVE: To study the association of climacteric vasomotor symptoms and nocturnal breathing abnormalities in a sample of healthy postmenopausal women. METHODS: Out of 71 postmenopausal women who took part in a large sleep study, 65 women were included into the present study. Sleep was monitored with polysomnography and nocturnal breathing with a static-charge sensitive bed and a pulse oximeter. Climacteric vasomotor symptoms were scored daily for 14 days and levels of oestradiol and FSH were measured in the serum. RESULTS: Altogether 21 (32.3%) women had some degree of breathing abnormalities during the study night. The occurrence of clinically significant sleep apnoea was low (1.5%) and of moderate type (OP-2). In contrast, increased respiratory resistance pattern, typical for partial upper airway obstruction, was frequent (16.9%). Seventy-eight per cent of the women had arterial oxyhaemoglobin desaturation events, but only in 4.6% of the women these events occurred more than 5 times/h of time in bed. Older women had more simple periodic breathing (P-1) and lower mean arterial oxyhaemoglobin saturation (SaO(2)). Body mass index (BMI) correlated with the apnoea frequency (OP-2) and inversely with the mean SaO(2). The severity of climacteric vasomotor symptoms or serum oestradiol concentration did not correlate with nocturnal breathing abnormalities. CONCLUSIONS: Nocturnal breathing abnormalities, especially partial upper airway obstruction, are common in postmenopausal women, but climacteric vasomotor symptoms do not predict their occurrence or severity. Increasing age and high BMI are important determinants of nocturnal breathing abnormalities.

Estrogen replacement therapy and nocturnal periodic limb movements: a randomized controlled trial.

OBJECTIVE: To evaluate the effect of estrogen replacement therapy on nocturnal periodic limb movements in a randomized, double-masked, placebo-controlled, crossover trial. METHODS: Seventy-one healthy postmenopausal women volunteered in answer to a newspaper announcement; 62 women completed the follow-up. Frequency of nocturnal body movements was measured with the static-charge-sensitive bed and all-night polysomnographic recordings. Serum estradiol (E2) and FSH concentrations were also measured at baseline and after each treatment period. The power of the study setup was 94%. RESULTS: Nearly half the women presented with episodes of periodic limb movements (30 of 62 women, or 48%, during placebo and 27, or 44%, during estrogen therapy). In 17 (27%) during placebo and 19 (31%) during estrogen therapy, frequency of periodic limb movements exceeded index level 5 per hour while subjects were in bed. Incidence or intensity of movements, movement durations, and movement intervals did not change with estrogen therapy. The arousal index was similar during the two treatments (medians = 1.7 for placebo and 1.3 for estrogen, P =.758). Variations in serum E2 concentration, age, and body mass index did not explain variations in movement activity. CONCLUSION: Estrogen replacement therapy in doses used to control climacteric symptoms does not alter the incidence or intensity of nocturnal periodic limb movements.

Medroxyprogesterone in postmenopausal females with partial upper airway obstruction during sleep.

The aim of the present study was to evaluate the degree and duration of respiratory stimulation caused by medroxyprogesterone acetate (MPA), and compare the effect of MPA to that of nasal continuous positive airway pressure (nCPAP) in sleep-disordered breathing. Ten postmenopausal females with predominantly partial upper airway obstruction during sleep had an overnight sleep study at baseline, on the fourteenth day of treatment with MPA and after a 3-week washout period. Six subjects on nCPAP were also studied 3 months later. At baseline, the overnight mean+/-SD end-tidal pressure of carbon dioxide (Pet,CO2) was 5.5+/-0.4 kPa the arterial oxygen saturation (Sa,O2) 93.0+/-1.2%, Sa,O2 nadir 80.0+/-6.7%, and frequency of oxygen desaturation > or = 4% (ODI4) per hour 2.2+/-1.3. MPA decreased Pet,CO2 by 0.8 kPa (14.5%, p<0.001). After washout, the mean Pet,CO2 remained at 0.5 kPa (9.1%, p<0.001) lower than at baseline. Sa,O2 did not change. Pet,CO2 was lower on MPA than on nCPAP (4.7+/-0.2 kPa versus 5.0+/-0.3 kPa; p=0.037) but Sa,O2 was similar. Apnoea/hypopnoea index tended to be lower on CPAP than on MPA. Medroxyprogesterone acetate at a daily dose of 60 mg improves ventilation in postmenopausal females with partial upper airway obstruction during sleep without compromising sleep. The ventilatory improvement is sustained for at least 3 weeks posttreatment. Medroxyprogesterone acetate was more efficient in decreasing the partial pressure of carbon dioxide but continuous positive airway pressure was superior in decreasing respiratory efforts.

Comparison of autonomic withdrawal in men with obstructive sleep apnea syndrome, systemic hypertension, and neither condition.

Obstructive sleep apnea syndrome is characterized by obesity, nocturnal breathing abnormalities, arterial hypertension, and an increased number of cardiovascular events. Sympathetic activity is increased during nocturnal apneic episodes, which may mediate the cardiovascular complications of sleep apnea. We studied 15 male subjects with obstructive sleep apnea syndrome and associated hypertension, 54 subjects with mild to moderate essential hypertension, and 25 healthy normotensive men. Cardiovascular autonomic control was assessed using frequency domain measures of heart rate variability (HRV) during a controlled breathing test and during orthostatic maneuver. Compared with normotensive and hypertensive groups, total power and low- and high-frequency components of HRV during controlled breathing were significantly (analysis of variance, p<0.0001) lower in the obstructive sleep apnea syndrome. During the orthostatic maneuver, the change in total power of HRV was different between the 3 groups (analysis of variance, p = 0.004). The total power of HRV tended to increase in the normotensive (4.11+/-12.29 ms2) and in hypertensive (2.31+/-12.65 ms2) groups, but decreased (1.13+/-1.23 ms2) in the hypertensive group with obstructive sleep apnea syndrome. According to multivariate regression analysis, age and sleep apnea were the major independent determinants of HRV. This study found that an abnormal response to autonomic nervous tests characterizes hypertension in overweight subjects with obstructive sleep apnea syndrome. This could be due to autonomic withdrawal or supersaturation of the end-organ receptors by excessive and prolonged sympathetic stimulation. Our results also show the reduced response of orthostatic maneuver and controlled breathing in the hypertensive group compared with the normotensive group.

Distributed clinical neurophysiology.

We have developed a consultation forum for clinical neurophysiology in Finland. The system connects local digital electroencephalography (EEG) recording and analysing networks using a high-speed asynchronous transfer mode (ATM) network. Clinicians can obtain a second opinion using interactive data and video consultations or using data-only consultations. In addition, the system can be used for off-line review of pre-recorded data. During a one-month evaluation, 66 EEG recordings were made altogether in Satakunta Central Hospital and consultations were required on 12 occasions. Nine of them were data-only consultations and three were data and video consultations. A data consultation lasted 15-20 min and a data and video consultation 35-45 min. Clinically, there were numerous benefits for the hospitals. The system established a link to a centre of excellence for second opinions or continuing education. It also helped with on-duty arrangements and enabled the construction of national data banks.

Detection of periodic leg movements with a static-charge-sensitive bed.

We evaluated the performance of the static-charge-sensitive bed (SCSB), a non-invasive movement sensor, in detecting nocturnal periodic movement activity using simultaneous bilateral anterior tibialis electromyography (EMGat) as a reference. Two different study setups were used, one with 500 random record extracts, another with 10 continuous recordings. The inter-rater reliability between two independent scorers was 0.92 in scoring EMGat and 0.91 in scoring SCSB. In an epoch based analysis, depending on the study setup and scorer, the sensitivity of the SCSB to detect periodic leg movements was 0.81-0.94 whereas the specificity was 0.84-0.89. In a movement-by-movement analysis, despite incomplete concordance between the two methods the total number of movements per hour were comparable. Our findings support the use of the SCSB as a non-invasive alternative to anterior tibialis EMG recordings to reveal the presence of nocturnal periodic movement activity and estimate its frequency.

Sleep-related disorders in carpal tunnel syndrome.

INTRODUCTION: Patients with carpal tunnel syndrome (CTS) often wake up at night due to pain and numbness of affected fingers and hand. We studied the sleep disorder caused by CTS. SUBJECTS AND METHODS: 34 consecutive patients referred for operative treatment of CTS answered to a sleep questionnaire and the results were compared to a stratified random sample of 1600 Finns aged 36-50 year, whose response rate to the mailed questionnaires was 75.2% (n = 1186). Six CTS patients underwent a polygraphic sleep study before and after operative treatment of CTS. RESULTS: CTS patients reported suffering from poor sleep quality, fragmentary sleep and daytime sleepiness more often than controls. Before operative treatment of CTS there were more nocturnal body movements (p < 0.01) and awakenings lasted longer (p < 0.05) than after operation. During preoperative sleep studies no drop in median nerve conduction was detected during awakenings. CONCLUSIONS: Patients with CTS suffer from fragmentary sleep. Although patients reported waking up for the pain or numbness of hands no impairment in median and ulnar nerve conduction could be observed during these awakenings. Operative treatment of hand entrapment significantly reduced the number of nocturnal movements.

Automatic SCSB analysis of motor and autonomic nervous functions compared with sleep stages.

All-night recordings of respiration, ballistocardiogram, and body movements were obtained using the static charge-sensitive bed (SCSB) and automatically analysed data were compared with sleep stages. The mean sum of eight SCSB variability parameters was lowest in slow wave sleep (SWS), higher during stage 2 (S2), and highest in REM sleep. The sum scores of the parameters with the highest correlations with the EEG data were classified into quiet (QS), intermediate (IS) and active (AS) states. SCSB signals during wakefulness, stage 1 and REM sleep were mostly scored as AS, whereas in S2 and especially in SWS they were scored as QS or IS. The SCSB is an easy and inexpensive tool for conducting follow-up studies on sleep quality in natural environments.

Nocturnal breathing abnormalities in acromegaly after adenomectomy.

OBJECTIVE: The incidence of sleep apnoea is increased in acromegaly. The aim of the study was to determine the occurrence of nocturnal breathing abnormalities and upper airway morphology in acromegalic patients some years after adenomectomy. DESIGN: A case-control study. PATIENTS: Eleven patients with treated acromegaly and two control groups: (1) sleep studies: 197 subjects randomly selected from the population, (2) cephalometry: 27 healthy subjects and 17 patients with obstructive sleep apnoea. MEASUREMENTS: Nocturnal breathing was monitored with a static charge-sensitive bed. The upper airway soft tissues and bone morphology were assessed by cephalometric X-ray photography. The upper airway collapsibility was investigated with dynamic nasopharyngoscopy. Endocrinological investigations were also performed. RESULTS: Nocturnal breathing abnormalities were present in all but one acromegalic patient (91%), which was far more frequent than in the general population (29.4%, P < 0.0001). Treated acromegaly was the most powerful predictor of breathing abnormalities, independent of the other significant predictors, age and body mass index. The predominant breathing abnormality was periodic breathing with symmetrically waxing and waning respiratory effort without a major body movement component. Episodes of complete obstruction with repetitive arousals were rare. Except for the longer soft palate, the cephalometric findings were similar to normal. In comparison to obstructive sleep apnoea, the treated acromegalic patients had rather prognathic than retrognathic mandibles. Fibreoptic endoscopy in the acromegalic patients revealed collapsible upper airways at the level of the soft palate, whereas at the base of the tongue little, if any, dynamic narrowing was observed. CONCLUSION: Our study confirms that nocturnal breathing abnormalities are common in treated acromegaly, and may persist years after the removal of the GH secreting tumour. The breathing abnormalities and the upper airway morphology in acromegalic patients after adenomectomy are different from those observed in primary obstructive sleep apnoea, suggesting a different pathophysiology of the airway obstruction.

Mandibular advancement with dental appliances in obstructive sleep apnoea.

The purpose of this study was to compare the effects of a modified Herbst appliance (mHA) and a muscle relaxation appliance (MR) on nocturnal breathing and body movement activity in patients with obstructive sleep apnoea syndrome (OSAS). To increase the airway space posterior to the tongue base without severely affecting the craniomandibular joint, the mHA was adjusted to anchor the mandible at 50% of maximum protrusion. MR producing an occlusal coverage but no protrusion served as a control appliance. All-night static charge-sensitive bed (SCSB) and finger oximeter recordings were done to six male patients in three conditions: first without dental device and then with mHA and with MR, in a random order, after a 2 month period of habituation. The oxyhaemoglobin desaturation events were 44.7 h-1 of recording observed during the control night, 29.6 h-1 with mHA (P = 0.087). The frequency of body movements decreased from 34.9 to 20.4 h-1 (P = 0.0079), respectively. MR had no significant effects either on the frequency of the desaturation events or the frequency of body movements, but the increased respiratory resistance breathing, indicating presence of partial upper airway obstruction, was reduced from 14.3 to 6.9% of the time in bed (P = 0.022). We conclude that 50% protrusion chosen for these experiments, produced with a mHA, brought about some alleviation of upper airway obstruction in our preselected patients, but did not lead to sufficient control of apnoea. The reduction of partial upper airway obstruction induced with a MR warrants further studies in a larger patient population.

Upper airway obstruction in hypothyroidism.

OBJECTIVES: To determine the occurrence and frequency of nocturnal upper airway obstruction in hypothyroidism. DESIGN: A case-control study of patients with newly diagnosed hypothyreosis and euthyroid subjects who had been selected from the population register. The subjects underwent sleep recordings with a static-charge-sensitive bed (SCSB). SETTING: Turku University Hospital and Research and Development Unit, Social Insurance Institution, Turku, Finland. SUBJECTS: Twenty six consecutive patients underwent sleep recordings with SCSB and a pulse oximeter. One hundred and eighty-eight euthyroid subjects who were previously studied with the SCSB were used as controls. MAIN OUTCOME MEASURES: In a multivariate analysis, hypothyroidism, gender, age, and body mass index (BMI) were considered as predictors for the occurrence of nocturnal breathing abnormalities. RESULTS: Nocturnal breathing abnormalities were frequent in both groups. Fifty per cent of the hypothyroid patients and 29.3% of the control subjects had at least some episodes of partial or complete upper airway obstruction (P = 0.04). Severe obstruction with episodes of repetitive apnoea was present in 7.7% of the patients and in 1.5% of the controls. The multivariate analysis revealed that the presence of hypothyroidism did not significantly (P = 0.06), and independently of age, BMI or gender, predict nocturnal breathing abnormalities, whereas obesity (P < 0.0001) and male gender (P = 0.0001) were independent and significant predictors. CONCLUSIONS: The incidence of nocturnal upper airway obstruction is increased in hypothyroidism, but is related to obesity and male gender rather than to hypothyroidism per se.