Electrophysiological brainstem investigations in obstructive sleep apnoea syndrome

In children with steroid-resistant nephrotic syndrome (SRNS) hyperlipidaemia may in the long term be associated with progressive renal insufficiency and increased risk of coronary heart disease. We have assessed the efficacy and tolerability of diet prior to and in combination with a hydroxymethylglutaryl CoA reductase inhibitor, simvastatin, in seven children with SRNS with a mean age of 8 years (range 1.8-16.3 years). Dietary advice to maintain adequate energy and protein intakes with reduced saturated fat and cholesterol intake had little impact on lipid levels pre treatment (mean reduction in cholesterol 1 mmol/l, triglyceride 1.1 mmol/l) but was maintained throughout the study duration. The mean cholesterol and triglyceride concentrations pre treatment were 12.1 +/- 2 (SEM) mmol/l and 8 +/- 2.1 (SEM) mmol/l, respectively. On a median simvastatin dose of 10 mg/day (range 5-40 mg) there was a 41% reduction in cholesterol to 6.6 +/- 0.77 (SEM) mmol/l and a 44% reduction in triglyceride to 3.9 +/- 1.38 (SEM) mmol/l at 6 months which was sustained at 12 months in five patients. The drug was well tolerated with no clinical side effects being noted. Over 6 months the mean plasma albumin concentrations increased from 18.2 +/- 1.26 (SEM) g/l to 23 +/- 2.51 (SEM) g/l, accounted for by three patients (1 complete remission, 1 partial remission, 1 end-stage renal failure). Plasma creatinine concentrations remained stable in five patients with two having progressive chronic renal failure. Growth parameters for both weight and height were maintained. Simvastatin has a beneficial effect on abnormal lipid levels in SRNS but the effectiveness of long-term therapy needs to be evaluated.     

New frontiers in the management of obstructive sleep apnoea syndrome

BACKGROUND: To report the dynamic magnetic resonance (MR) imaging findings of hepatolithiasis. METHODS: Dynamic MR images (fast spoiled gradient echo sequence with intravenous injection of gadopentate dimeglumine) and computed tomography, cholangiography, or angiography of nine patients with hepatolithiasis are analyzed. RESULTS: All affected hepatic segments showed atrophic changes and contained dilated intrahepatic ducts. These segments showed either iso- or hypointensity on T1-weighted imaging and hyperintensity on T2-weighted imaging. Preferential enhancement was noted throughout all phases of the dynamic study and persisted to delayed T1-weighted imaging in seven patients. In the last two patients, severe atrophic changes made evaluating signal intensity differences and enhancement patterns difficult. CONCLUSION: In addition to intrahepatic stones and biliary dilatation, segmental atrophy, signal intensity differences, and preferential and persistent enhancement are important MR findings of hepatolithiasis.     

Microarousals in patients with sleep apnoea/hypopnoea syndrome

As medical schools begin to implement their new curricula under the guidance of Tomorrow's Doctors, the authors wish to raise some discussion on the form and content of the special study module (SSM) component. In order to do this they put forward in this paper proposals for an SSM in Medicine and Literature. This course has been designed jointly and will be run concurrently in three Scottish medical schools: Glasgow, Aberdeen and Dundee. Arguments for the course's acceptability to faculties of medicine and to students are discussed and its inclusion in the curriculum in terms of its educational impact, skills training, effect on personal development and broadening of the student's perspective are justified. The course structure, content and assessment procedures are described and a reading list proposed. The General Medical Council points out that SSMs should be seen as opportunities for innovation and this course demands a different educational approach from the standard objectives-led approach of most medical education. A process-led model is more appropriate as it stresses the way that students develop while taking the course rather than the end point reached at its finish.     

Chemical control of breathing in patients with obstructive sleep apnea

The authors have studied chemical control of breathing in 37 normocapnic patients with OSA. These patients had increased apnea-hypopnea index (AHI = 51 +/- 22), obesity (BMI = 32.4 +/- 5.6 kg/m2) and normal lung function tests. Control group consisted of 20 healthy subjects with normal weight (BMI = 23.1 +/- 2.4 kg/m2). Respiratory responses (ventilatory and P0.1) to hypercapnic and hypoxic stimulation during rebreathing tests were measured with computerized methods. The obtained results in OSA patients were compared with the data of the control group. The results exceeding mean values of the control group above 1.64 SD were recognized as hyperreactive responses. The majority e.g. 26 patients (OSA-N) had normal respiratory responses during hypercapnic stimulation. delta V/delta PCO2 = 16.8 +/- 4.5 L/min/kPa, P0.1/delta PCO2 = 3.5 +/- 2.4 cm H2O/kPa/. In remaining 11 patients (OSA-H) respiratory responses were significantly increased delta V/delta PCO2 = 39.1 +/- 18.8 L/min/kPa, P0.1/delta PCO2 = 8.6 +/- 3.9 cm H20/kPa). During isocapnic hypoxic stimulation majority e.g. 25 patients (OSA-H) had significantly increased respiratory responses delta V/delta SaO2 = 3.28 +/- 1.63 L/min/%, delta P0.1/delta SaO2 = 0.54 +/- 0.43 cm H2O/%/. In remaining 12 patients (OSA-N) respiratory responses were within normal limits delta V/SaO2 = 1.2 +/- 0.28 L/min/%, delta P0.1/ delta SaO2 = 0.21 +/- 0.07 cm H2O/%/. The above results indicated, that majority OSA patients (67.5%) had increased ventilatory and P0.1 responses to hypoxic stimulation. Among them also 11 patients had increased respiratory responses to hypercapnia. It seems, that increased respiratory responses to hypoxic stimulus in OSA patients are symptoms of protective reaction to hypoxaemia occurring during repetitive sleep apnoea and reveals increased neuro-muscular output.     

Screening obstructive sleep apnoea syndrome by home videotape recording in children

Overnight polysomnography (PSG) has been used to diagnose and assess the severity of obstructive sleep apnoea syndrome (OSAS) in children. The aim of this study was to determine whether home video-recording of children during sleep may be used for screening OSAS. In 58 children suspected of having OSAS, PSG results were compared with the corresponding analyses of 30 min video-recordings of each child sleeping at home. The video-recordings were evaluated by: 1) overall investigator's clinical judgement; and 2) a scoring system based on noisy breathing, movements, walking episodes, apnoea, chest retractions and mouth breathing. PSG results were highly correlated with the video test results, with agreement in 49 out of 58 (84%). In 36 of the 58 children, the PSG was abnormal compared with 41 out of 58 abnormal video tests. The sensitivity of the overall investigator judgement of video test was 94% (34 out of 36) and the specificity 68% (15 out of 22). Video scores > 10 were highly predictive of OSAS, whilst scores < 5 were associated with normality. Using a stepwise logistic regression analysis, each of the scoring variables was tested against the PSG results and an equation was formulated for predicting PSG by the video test. The equation predicted PSG results in 49 out of 58 (84%) cases. Thirty minutes of home video-recordings during sleep is a reliable screening method for obstructive sleep apnoea syndrome in children. This technique may, thus, improve patient selection for polysomnography.     

Impairment of muscle energy metabolism in patients with sleep apnoea syndrome

Impairment of muscle energy metabolism has been demonstrated in normal subjects with chronic hypoxaemia (altitude chronic respiratory failure). The purpose of this study was to verify the hypothesis that a comparable condition could develop in patients with sleep apnoea syndrome (SAS), considering that they are exposed to prolonged and repeated hypoxaemia periods. Muscle metabolism was assessed in 11 patients with SAS performing a maximal effort on cycloergometer. In comparison with normal subjects, SAS patients reached lower maximal loads [144 +/- 7 vs. 182 +/- 10 W (P < 0.005)] and lower peak oxygen uptakes [26.4 +/- 1.2 vs 33.2 +/- 1.4 ml kg-1 min-1 (P < 0.005)]. Abnormal metabolic features were found: maximal blood lactate concentration was significantly lower than in normal subjects [0.034 +/- 0.004 vs. 0.044 +/- 0.002 mmol l-1 W-1 (P < 0.05)]; and lactate elimination rate, calculated during a 30-min recovery period, was reduced [0.127 +/- 0.017 vs, 0.175 +/- 0.014 mmol l-1 min-1 (P < 0.025)]. The extent of these anomalies correlated with the severity of SAS. The patients also showed higher maximal diastolic blood pressures than normal subjects [104 +/- 5 vs. 92 +/- 4 mmHg (P < 0.05)]. These results can be interpreted as indications of an impairment of muscle energy metabolism in patients with SAS. Decrease in maximum blood lactate concentration suggests an impairment of glycolytic metabolism, while decrease in the rate of lactate elimination indicates a defect in oxidative metabolism. Since no respiratory pathology apart from SAS was found in this group of patients, it seems legitimate to link the genesis of these impairments to repeated bouts of nocturnal hypoxaemia.     

Acoustic analysis of snoring sound in patients with simple snoring and obstructive sleep apnoea

Snoring, a symptom which may indicate the presence of the obstructive sleep apnoea syndrome (OSA), is also common in the general population. Recent studies have suggested that the acoustic characteristics of snoring sound may differ between simple snorers and OSA patients. We have studied a small number of patients with simple snoring and OSA, analysing the acoustic characteristics of the snoring sound. Seventeen male patients, 10 with OSA (apnoea/hypopnoea index (AHI) 26.2 events x h(-1)) and seven simple snorers (AHI 3.8 events x h(-1)), were studied. Full night polysomnography was performed and the snoring sound power spectrum was analysed. Spectral analysis of snoring sound showed the existence of two different patterns. The first pattern was characterized by the presence of a fundamental frequency and several harmonics. The second pattern was characterized by a low frequency peak with the sound energy scattered on a narrower band of frequencies, but without clearly identified harmonics. The seven simple snorers and two of the 10 patients with OSA (AIH 13 and 14 events x h(-1), respectively) showed the first pattern. The rest of the OSA patients showed the second pattern. The peak frequency of snoring was significantly lower in OSA patients, with all but one OSA patient and only one simple snorer showing a peak frequency below 150 Hz. A significant negative correlation was found between AHI and peak and mean frequencies of the snoring power spectrum (p<0.0016 and p<0.0089, respectively). In conclusion, this study demonstrates significant differences in the sound power spectrum of snoring sound between subjects with simple snoring and obstructive sleep apnoea patients.     

Goitre: a cause of obstructive sleep apnoea in euthyroid patients

While hypothyroidism is considered to predispose to obstructive sleep apnoea (OSA), the presence of a goitre itself is not a recognized cause of OSA. We present the cases of two euthyroid patients with large goitres and clinical evidence of OSA, whose OSA symptoms significantly improved following partial thyroidectomy. This finding suggests that the goitre contributed to their symptoms.     

Resolution of obstructive sleep apnoea with growth in the Robin sequence

A 12 year old female with the Robin sequence presented with a one year history of snoring, witnessed apnoeas and daytime sleepiness. Surgery in early childhood had consisted of cleft palate repair, tonsillectomy and adenoidectomy and, later, revision palatoplasty. Overnight polysomnography (PSG) demonstrated severe obstructive sleep apnoea syndrome with an apnoea/hypopnoea index (AHI) of 49 events x h(-1), and repetitive oxygen desaturations below 50%. Nasal continuous positive airway pressure (nCPAP) effectively controlled her sleep abnormalities. After 3 yrs of nCPAP therapy, she requested discontinuation and was fully reassessed. PSG without nCPAP revealed an AHI <5 events x h(-1) with no desaturations below 90% and normal sleep quality. A repeat lateral cephalometrogram showed increased mandibular length and posterior airway space and reduced soft palate length. The patient remains asymptomatic 9 months following nCPAP discontinuation. This case indicates that nasal continuous positive airway pressure is an effective nonsurgical therapy in children with obstructive sleep apnoea syndrome and the Robin sequence. It is likely that mandibular growth, increase in mandibular length and enlargement of the posterior airway space was responsible for the resolution of obstructive sleep apnoea syndrome in this case.     

Pulmonary hypertension in patients with obstructive sleep apnea syndrome

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is associated with an increased cardiovascular morbidity, including pulmonary hypertension. Little is known about factors influencing the degree of pulmonary hypertension and left ventricular dysfunction in patients with OSAS, especially in the absence of concomitant lung disease. METHODS: Right heart catheterization, arterial blood gas analysis, and pulmonary function tests were performed in 92 consecutive patients (81 men and 11 women; mean +/- SD age, 53.1 +/- 11.0 years) with polysomnographically verified OSAS, in whom clinically significant lung disease was excluded. RESULTS: Eighteen patients (20%) had mild pulmonary hypertension; 8 (44%) of them also had increased pulmonary capillary wedge pressures (Ppew). Left ventricular dysfunction was associated with arterial hypertension. Only Ppcw (r = 0.51; P < .001) and the percentage of time during sleep spent with an oxygen saturation below 90% (as an indicator of the severity of OSAS) (r = 0.34; P = .003) were significantly and independently associated with pulmonary artery pressure. CONCLUSIONS: Obstructive sleep apnea syndrome can cause mild pulmonary hypertension, even in the absence of pulmonary disease. In these patients, pulmonary hypertension is of the postcapillary type, or-in patients with normal left ventricular function-strongly related to the severity of OSAS. Our findings indicate that OSAS may constitute an important, and independent, risk factor for pulmonary hypertension.     

Residual effect of nCPAP applied for part of the night in patients with obstructive sleep apnoea

The aim of the present study was to assess whether nasal continuous positive airway pressure (nCPAP) treatment, applied for only a few hours at the beginning of the night, has any residual effect on sleep and breathing during the ensuing hours of unassisted sleep in patients with obstructive sleep apnoea syndrome (OSAS). In 27 patients with newly-diagnosed OSAS, effective nCPAP was applied during the first part of the night and then withdrawn. Polysomnographic parameters after nCPAP withdrawal were compared with those of the corresponding part of the diagnostic polysomnography performed a few days or weeks before and with those of the first part of night on nCPAP. After 255+/-63 (mean+/-SD) min of sleep with normalization of sleep and breathing parameters under nCPAP, there was partial improvement of OSAS severity during the remaining 124+/-56 min of nocturnal sleep without treatment; mean oxygen saturation, desaturation index (equivalent to the apnoea/hypopnoea index) and movement arousal index all improved significantly with respect to the diagnostic night (p=0.001). This improvement was not accounted for by a change in sleep architecture. We conclude that there is an improvement in severity of obstructive sleep apnoea syndrome after only 4 h of nasal continuous positive airway pressure. This carryover effect could explain why a number of patients with obstructive sleep apnoea syndrome apply nasal continuous positive airway pressure for only part of the night or not every night.     

Craniofacial abnormalities in sleep apnoea syndrome

Each year, 15 transvestibular transseptal transsphenoidal hypophysectomies are performed in Lausanne. The aim of the study was to determine the complications rate of our procedure and their influence on the life quality of patients. Questionnaires were sent to 178 patients, operated between 1984 and 1995. 125 questionnaires were returned. Out of those, 73 patients accepted to undergo a control rhinoscopy. The most frequent complains were nasal obstruction and crusting (38% each), whistling while breathing through the nose (12%), and stuffiness of the upper lip or teeth (7%). Endoscopically, we detected an anterior septal perforation in 10 cases (13.7%), 8 (80%) of which were symptomatic and a posterior septal perforation in 6 cases, all of them being asymptomatic. Finally, 36% of the patients had no complains and 19% of them had an improvement of respiration after the operation. Of the whole series of 178 patients, only 5% had complications requiring an ENT follow-up for longer than 6 months after having been operated.     

Cor pulmonale due to obstructive sleep apnoea

A 47 year old man with a long history of chronic loud snoring and daytime sleepiness presented with hypercapnic respiratory failure and right ventricular failure. The diagnosis of obstructive sleep apnoea (OSA) leading to the 'obesity-hypoventilation syndrome', was supported by the findings of an overnight cardio-respiratory monitoring during sleep. His symptoms and arterial blood gases improved following treatment with nocturnal nasal continuous positive airway pressure (CPAP).     

Effects of nasal continuous positive airway pressure on breathing pattern and respiratory drive in patients with obstructive sleep apnea syndrome

To examine the influence of continuous positive airway pressure (CPAP) therapy on respiratory center drive in patients with obstructive sleep apnea syndrome (OSAS), 20 normocapnic OSAS patients (group 0) and 20 simple snoring patients were studied. In the first night, diagnostic polysomnography (PSG) was performed. Before and after PSG monitoring, mouth occlusion pressure (P0.1), tidal volume (VT), minute ventilation (VE), respiratory rate (RR), inspiratory time (Ti), expiratory time (Te), total cycle duration (Ttot), inspiratory duty cycle (Ti/Ttot), mean inspiratory flow (VT/Ti) and effective inspiratory impedance (P0.1/VT/Ti, Ieff) were measured while they were breathing room air. In the following night the OSAS patients were treated with nasal CPAP and PSG monitoring and the above mentioned measurements were repeated. The results showed that pre-PSG values of P0.1, RR and P0.1/VT/Ti in the OSAS patients were significantly higher than those in the snoring patients, while VT, Ti, Te and Ttot values were lower. In the first night, the post-PSG P0.1 value in the OSAS patients increased markedly as compared with the pre-PSG. After overnight nasal CPAP therapy, the respiratory disorder index in the OSAS patients decreased markedly, the nadir SaO2 increased markedly, but the post-PSG P0.1 value did not increase significantly. It is concluded that, before sleep, OSAS patients exhibit a higher respiratory drive and a shallow and frequent breathing pattern as compared with simple snoring patients. After nocturnal sleep, the respiratory drive of OSAS patients increases significantly, the breathing pattern becomes more shallow and frequent. Nasal CPAP may effectively relieve the sleep apnea and hypopnea as well as the resulting hypoxemia and therefore correct the changes in breathing pattern and respiratory drive through nocturnal sleep in patients with OSAS.     

Improvement of epileptic seizure control with treatment of obstructive sleep apnoea

Modified LDL, caused by many factors, is associated with increased atherogenisity. In many modified LDLs, it is recognized that LDL oxidation occurs in vivo, and oxidized LDL demonstrates enhanced cellular uptake by macrophage scavenger receptor, foam cell formation. In vitro, iron and zinc are necessary for oxidized LDL and lipid peroxisides, and considering these elements to participate in vivo, particularly hyperlipidemia. In fact, hyperlipidemia with high serum levels iron or zinc concentration is a risk factor of coronary heart disease. Further, the possibility of selenium insufficiency accelerated lipid peroxisides in vivo, because glutathione peroxidase (GSHPx), the antioxidant effect, includes selenium, and GSHPx hyperproduction are recognized in atherosclerotic lesion. It is known that oxidized LDL are more excessive in hyperlipidemia, so hyperlipidemia may suffer more from trace element status in vivo. Enzymes and hormones, influencing lipid metabolism, are necessary for many trace elements their activation. Trace elements may therefore, be important in several stage of lipid metabolism.