Flow-regulatory function of upper airway in health and disease: a unified pathogenetic view of sleep-disordered breathing

Although the Starling resistor behavior of the upper airway during sleep has been well established in health and disease, its physiological implications have not been fully appreciated. The purposes of the present communication are to reassess the current state of knowledge within the framework of the Starling resistor concept and to examine the implications of the concept on homeostatic feedback respiratory control and the pathogenesis of the sleep apnea syndrome. The main inferences drawn from the assessment include: (1) Owing to the Starling resistor properties of the upper airway and the well-organized neurochemical control mechanism, the upper airway performs important homeostatic flow regulatory function; it appropriately dampens the potentially unstable breathing during sleep and prevents the PaCO2 from falling below the apneic threshold; (2) Under certain conditions, the upper airway flow regulatory function fails to achieve appropriate dampening, leading to development of a variety of sleep-related breathing disorders that include underdamping due to overly sensitive central chemoresponsiveness and/or excessive lung to chemoreceptor transport lag--central sleep apnea; overdamping due to upper airway obstructive dysfunction--obstructive sleep apnea and/or hypopnea; and, finally, conditions with mixed features of central underdamping with coexisting collapsible upper airway; and (3) Successful treatment of these conditions requires restoration of appropriate damping. The overdamping imposed by the faulty upper airway is effectively reduced by surgical and medical approaches, and by application of nasal continuous positive airway pressure (CPAP). Reduction of PaCO2 by use of acetalzolamide and/or aminophylline reduces the plant gain, thus effectively offsetting the underdamping of central origin. Owing to the dual effect of nasal CPAP on the upper airway and respiratory pump, use of nasal CPAP can also effectively reduce the plant gain, accounting for the therapeutic effect of nasal CPAP on the central sleep apnea.     

Activity of phosphatidylinositol-specific phospholipase C from Bacillus cereus with thiophosphate analogs of dimyristoylphosphatidylinositol

We examined the effects of nasal continuous positive airway pressure (CPAP) on exercise performance in patients with obstructive sleep apnea (OSA). Six patients were treated with nasal CPAP on seven successive days and underwent overnight sleep studies and multiple sleep latency test (MSLT) at the beginning and after the last day of the treatment. The subjects also performed incremental exercise testing using a bicycle ergometer followed by 0-w, 25-w, 50-w,--(3 minutes each) until maximum level. Arterial oxygen pressure, arterial carbon dioxide pressure at rest while awake, apnea/ hypopnea index, longest apnea duration, the lowest percutaneous oxygen saturation measured by a pulse oximeter and the value of MSLT were significantly improved after nasal CPAP. Moreover, maximal oxygen consumption was significantly increased from 1841 ml/min +/- 350 to 2125 ml/min +/- 351 (p < 0.05); however, other cardiorespiratory parameters did not change significantly. The improvement of exercise performance by short-term nasal CPAP treatment in OSA patients may correlate with the improvement of sleepiness.     

The effect of nasal CPAP on nocturnal reflux in patients with aperistaltic esophagus

It has been shown that nasal continuous positive airway pressure (nasal CPAP) significantly reduces nocturnal reflux both in patients with sleep apnea and in patients without sleep apnea but consistent abnormal nocturnal reflux. The mechanism by which CPAP is thought to reduce reflux includes the elevation of the resting lower esophageal sphincter (LES) pressure. In this study, we tested the effect of nasal CPAP in two groups of patients with aperistaltic esophagus but with different resting LES pressure. Seven patients with scleroderma esophagus and six patients treated for achalasia were tested over a 48-h period. On the first night, the patients were untreated; on the second night, both groups received applied nasal CPAP at 8 cm H2O pressure. The percentage of time the pH < 4.0, the number of reflux events > 5 min, and the length of the longest reflux event were all significantly reduced in the patients with achalasia (p < 0.03), but not in the scleroderma group (p > 0.20). These results suggest that a residual resting LES pressure greater than that demonstrated by patients with scleroderma (> 10 mm Hg) may be necessary for nasal CPAP to affect nocturnal reflux.     

Unusual complication of nasal CPAP: subcutaneous emphysema following facial trauma

Subcutaneous emphysema is an unusual complication of nasal continuous positive airway pressure (CPAP). We report a case of a 58-year-old man who fell and sustained mild facial trauma to the left side of his head. After using CPAP the following night, he developed diffuse subcutaneous emphysema of his face and left neck. He discontinued CPAP, and his symptoms improved. The potential mechanisms of this patient's subcutaneous emphysema and the prior reports of this complication following facial trauma or dental procedure without use of CPAP are reviewed. Although there are case reports of bacterial meningitis and pneumocephalus following use of nasal CPAP, we are not aware of any prior reports of subcutaneous emphysema following use of CPAP. In light of our experience and the above related case reports, we would suggest nasal CPAP be withheld temporarily in the setting of acute facial trauma.     

Obstructive sleep apnea during pregnancy resulting in pulmonary hypertension

Obesity is known to increase maternal morbidity and mortality. We describe a case of obstructive sleep apnea due to obesity and discuss our treatment of the resulting pulmonary hypertension. A patient was transferred to our hospital at 29 weeks' gestation with severe anasarca and more than a 100-pound weight gain during pregnancy. Pulmonary hypertension due to obstructive sleep apnea was diagnosed. The patient was treated with nasal continuous positive airway pressure (CPAP) during sleep and remained in the hospital the remainder of her pregnancy. She had a massive spontaneous diuresis during her hospital stay and lost more than 100 pounds. She was delivered at term via cesarean section because of transverse lie. Preoperative hemodynamic monitoring confirmed the diagnosis of pulmonary hypertension. This represents the first case in the literature of obstructive sleep apnea leading to pulmonary hypertension in pregnancy. This patient responded well to nasal CPAP as evident by the massive diuresis and good maternal outcome.     

Early treatment with nasal continuous positive airway pressure and "minimal handling". Early and late prognosis in children with birth weight under 1,501 g

During 1988 and 1989 a regional cohort of 81 infants with birth weights of less than 1501 g were treated with oxygen (n = 11), early continuous positive airway pressure (CPAP) (n = 68) or mechanical ventilation from birth (n = 2). We used an easily applicable lightweight CPAP system with nasal prongs and a gas jet supplemented with ventilator treatment if necessary, but with conservative criteria for ventilator treatment with tolerance of high PCO2. A total of 65 infants (80%) survived to discharge, 61 of whom were supported solely with CPAP or oxygen. Nineteen infants (26%) developed periventricular-intraventricular haemorrhage, but only four survivors (6%) developed prognostically significant bleedings of grade 2-4. No survivors had bronchopulmonary dysplasia. Follow-up at 1.5-5 years of age revealed definite disabilities in seven (11%). The results suggest that treatment by early CPAP with nasal prongs with tolerance of high PCO2 may be effective and lenient in most infants of more than 25 weeks' gestation.     

Therapeutic leukapheresis in the patient with leukemia

OBJECTIVE: To predict and optimal level of continuous positive airway pressure (CPAP) in the menagement of obstructive sleep apnea syndrome (OSAS) by relating certain parameters of respiratory disturbance and sleep hypoxemia. METHODS: 18 patients with OSAS (all male, aged 48 +/- 11 yrs) were enrolled in the study. Their actual levels of CPAP (Pm) were determined by a RHK-5500 mode polysomnographic system plus BiPAP (ST/D) system. The actuual Pm was related to the respiratory disturbance index (RDI) or total time of SaO2 < or = 90% (T S90). The correlation regression equations were calculated. 6 patients with OSAS (Group A) were treated with the predicted nasal CPAP (predicted Pm) which was derived from the regression equation, 8-10 hours per night, for 5-7 nights. 13 patients (Group B) receiving nasal CPAP treatment using the actually measured Pm served as control. RESULTS: There was a close positive linear correlation between RDI or T S90 and actual Pm. Symptoms and polysomnographic parameters improved significantly after one course of CPAP treatment in Group A. The efficacy showed no signifcant different as compared with that in Group B. CONCLUSIONS: It was suggested that RDI or T S90 are of value and simple in predicting the pressuure level of CPAP in the management of OSAS with nasal CPAP.     

Surgical maxillofacial treatment of obstructive sleep apnea

Obstructive sleep apnea is the most common sleep-related breathing disorder, with a surprisingly high prevalence. The treatment of choice is nasal continuous positive airway pressure (CPAP) ventilation during sleep, which has to be applied throughout the patient's whole life. Because of various underlying pathomechanisms in patients with certain craniofacial disorders--narrow posterior airway space and maxillary-mandibular deficiency--surgical therapy by craniofacial osteotomies seems possible. A series of 38 consecutive patients were treated by 10-mm maxillomandibular advancement by retromolar sagittal split osteotomy and Le Fort I osteotomy, respectively. Obstructive sleep apnea syndrome was improved considerably in all patients; there was no significant difference compared to the results under nasal CPAP. In 37 of 38 patients, the postoperative apnea-hypopnea index was reduced clearly to under 10 per hour, oxygen saturation rose, and sleep quality improved. This was achieved by maxillomandibular advancement of 10 mm without secondary refinements in all but 2 patients. In one patient, the apnea-hypopnea index could only be reduced to 20 per hour, probably because of insufficient maxillary advancement. These results indicate that successful surgical treatment is possible in a high percentage of selected patients with certain craniofacial characteristics. In addition to cardiorespiratory polysomnography, there should be routine cephalometric evaluation of all patients. Maxillomandibular advancement should be offered as an alternative therapy to all patients with maxillary and/or mandibular deficiency or dolichofacial type in combination with narrow posterior airway space.     

The use of nasal CPAP in newborns with respiratory distress syndrome

The efficiency of applying continuous positive airway pressure (CPAP) by the nasal route was retrospectively nalyzed in 32 newborns with RDS (23 uncomplicated HMD with additional cardiac or pulmonary complications and 7 RDS of non-hyaline membrane etiology) who underwent nasal CPAP treatment at the Kinderspital Zurich from 1972--1974. 16 of the 23 infants with uncomplicated HMD were successfully treated with CPAP. They showed a significant rise in PaO2 as well as a significant drop in respiratory frequency during nasal CPAP application, the PaCO2 did not change significantly. The remaining 7 infants in this group (7/23) had to be intubated and mechanically ventilated owing to a persistent high FIO2 (4 infants), technical difficulties (1) or nasal hypersecretion (2). Two of these 23 infants died, one of meningitis, one of cerebral hemorrhage. The two infants with HMD and additional cardiac or pulmonary complications and 3 of 7 infants with RDS of non-hyaline membrane etiology had to be intubated and mechanically ventilated after failure of nasal CPAP. All 9 infants in these two groups survived. The nasal CPAP system as described is a simple, inexpensive and effective method of applying CPTPP in newborns with uncomplicated HMD, except radiological stage IV. In HMD with additional cardiac or pulmonary complications and in RDS of non-hyaline membrane etiology the results of nasal CPAP treatment were not convincing.     

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.     

Early evaluation of results from systemic thrombolysis in acute myocardial infarct: the value of troponin I

STUDY OBJECTIVES: This paper compares the performance of an experimental nasal positive airway pressure device that automatically adjusts the level of applied pressure (APAP) with the performance of a conventional continuous positive airway pressure (CPAP) in a sleep laboratory study. DESIGN: In a randomized sequence, conventional CPAP therapy was applied for 1 night (CPAP night) and APAP therapy the following night (APAP night). SETTING: The study was conducted in an accredited sleep disorders center. PATIENTS OR PARTICIPANTS: Twenty-six men and 5 women between the ages of 35 to 73 (51 +/- 9.6) years with body mass index 35.82 +/- 8.35 (kg/m2) who were diagnosed (using standard nocturnal polysomnography [NPSG] methods) as having OSA syndrome were studied. The subjects were treated with conventional CPAP for approximately 8 (7.79 +/- 3.16) weeks at home prior to their participation in this study. MEASUREMENTS AND RESULTS: All standard polysomnography data and nasal mask pressures were recorded using a computer-based data acquisition system. Sleep and respiratory data were scored by a registered polysomnographer. The mean apnea-hypopnea index (AHI) for subjects for the NPSG night was 55.2 +/- 33.7. It dropped to 4.2 +/- 3.8 for the CPAP night and to 5.4 +/- 5.4 for the APAP night. There was no significant (p = 0.05) difference between mean AHI indices, sleep stages, sleep stage shifts, and snore arousals for CPAP night and APAP night. However, all the measures showed significant (p = 0.05) improvement over NPSG night. The mean of APAP applied pressure (8.4 +/- 3.3 cm H2O) was significantly (p = 0.05) lower than the prescribed pressure (11.5 +/- 3.1 cm H2O), but there was no significant (p = 0.05) difference between the maximum APAP applied pressure (12.8 +/- 4.3 cm H2O) and the prescribed pressure (11.5 +/- 3.1 cm H2O). All mean comparison tests were carried out using two-tailed statistics. CONCLUSIONS: APAP appears to be as effective as CPAP in treating OSA patients. APAP delivers the same level of therapy as CPAP, but it reduces the average airway pressure while providing needed peak pressures.     

Long-term evolution of daytime somnolence in patients with sleep apnea/hypopnea syndrome treated by continuous positive airway pressure

We demonstrated in a previous study that excessive daytime sleepiness (EDS) in patients who have sleep apnea/hypopnea syndrome (SAHS) and are undergoing continuous positive airway pressure (CPAP) treatment improved differently in two groups of patients: in group I, multiple sleep latency tests (MSLT) were normalized after 50 days of treatment (individual value > 10 minutes), whereas they remained low (individual value < 10 minutes) in group II, with a significant difference between groups. To evaluate the long-term evolution of daytime somnolence under nasal CPAP treatment, five patients from group I and seven patients from group II underwent a new polysomnography and MSLT 4 years after the previous study. Clinical, polysomnographic and MSLT results obtained at baseline before treatment (T1), after the initial 50-day period of CPAP treatment (T2), and after 4 years (T3) were compared. The significant difference in mean MSLT value between the two groups previously observed at T1 and T2 disappeared at T3 (group I: 12.4+/-5.9 minutes; group II: 9.7+/-5.9 minutes). We found that this long-term improvement in excessive daytime somnolence was independent of the initial MSLT value, the severity of SAHS, and the initial MSLT changes under nasal CPAP. Long-term MSLT evolution was significantly correlated to CPAP compliance. These results demonstrate that even in the absence of a significant increase in MSLT at the beginning of CPAP treatment, further improvement is still possible several years later, which may encourage the regular, long-term use of nasal CPAP by patients.     

Does airway pressure release ventilation alter lung function after acute lung injury?

BACKGROUND: During airway pressure release ventilation (APRV), tidal ventilation occurs between the increased lung volume established by the application of continuous positive airway pressure (CPAP) and the relaxation volume of the respiratory system. Concern has been expressed that release of CPAP may cause unstable alveoli to collapse and not reinflate when airway pressure is restored. OBJECTIVE: To compare pulmonary mechanics and oxygenation in animals with acute lung injury during CPAP with and without APRV. DESIGN: Experimental, subject-controlled, randomized crossover investigation. SETTING: Anesthesiology research laboratory, University of South Florida College of Medicine Health Sciences Center. SUBJECTS: Ten pigs of either sex. INTERVENTIONS: Acute lung injury was induced with an intravenous infusion of oleic acid (72 micrograms/kg) followed by randomly alternated 60-min trials of CPAP with and without APRV. Continuous positive airway pressure was titrated to produce an arterial oxyhemoglobin saturation of at least 95% (FIO2 = 0.21). Airway pressure release ventilation was arbitrarily cycled to atmospheric pressure 10 times per minute with a release time titrated to coincide with attainment of respiratory system relaxation volume. MEASUREMENTS: Cardiac output, arterial and mixed venous pH, blood gas tensions, hemoglobin concentration and oxyhemoglobin saturation, central venous pressure, pulmonary and systemic artery pressures, pulmonary artery occlusion pressure, airway gas flow, airway pressure, and pleural pressure were measured. Tidal volume (VT), dynamic lung compliance, intrapulmonary venous admixture, pulmonary vascular resistance, systemic vascular resistance, oxygen delivery, oxygen consumption, and oxygen extraction ratio were calculated. MAIN RESULTS: Central venous infusion of oleic acid reduced PaO2 from 94 +/- 4 mm Hg to 52 +/- 9 mm Hg (mean +/- 1 SD) (p < 0.001) and dynamic lung compliance from 40 +/- 6 mL/cm H2O to 20 +/- 6 mL/cm H2O (p = 0.002) and increased venous admixture from 13 +/- 3% to 32 +/- 7% (p < 0.001) in ten swine weighing 33.3 +/- 4.1 kg while they were spontaneously breathing room air. After induction of lung injury, the swine received CPAP (14.7 +/- 3.3 cm H2O) with or without APRV at 10 breaths per minute with a release time of 1.1 +/- 0.2 s. Although mean transpulmonary pressure was significantly greater during CPAP (11.7 +/- 3.3 cm H2O) vs APRV (9.4 +/- 3.8 cm H2O) (p < 0.001), there were no differences in hemodynamic variables. PaCO2 was decreased and pHa was increased during APRV vs CPAP (p = 0.003 and p = 0.005). PaO2 declined from 83 +/- 4 mm Hg to 79 +/- 4 mm Hg (p = 0.004) during APRV, but arterial oxyhemoglobin saturation (96.6 +/- 1.4% vs 96.9 +/- 1.3%) did not. Intrapulmonary venous admixture (9 +/- 3% vs 11 +/- 5%) and oxygen delivery (469 +/- 67 mL/min vs 479 +/- 66 mL/min) were not altered. After treatment periods and removal of CPAP for 60 min, PaO2 and intrapulmonary venous admixture returned to baseline values. DISCUSSION: Intrapulmonary venous admixture, arterial oxyhemoglobin saturation, and oxygen delivery were maintained by APRV at levels induced by CPAP despite the presence of unstable alveoli. Decrease in PaO2 was caused by increase in pHa and decrease in PaCO2, not by deterioration of pulmonary function. We conclude that periodic decrease of airway pressure created by APRV does not cause significant deterioration in oxygenation or lung mechanics.     

Concomitant radiotherapy with mitomycin C and bleomycin compared with radiotherapy alone in inoperable head and neck cancer: final report

We evaluated the efficiency of two different treatment procedures with continuous positive airway pressure (CPAP) on sleep, nocturnal breathing characteristics and daytime vigilance in 18 newly diagnosed patients with untreated sleep apnoea/hypopnoea syndrome (SAHS) randomly allocated to two different groups. In group I, the positive pressure (PP) level was set to suppress flow limitation (PFL), while in group II the PP was set at a level that eliminated only apnoea/hypopnoea and snoring (PAHS). At the end of a 3 week period of home CPAP therapy, a follow-up sleep study, vigilance and cognitive tests were made. Overall, PFL was significantly higher than PAHS values (PFL: 10.42.6 cmH2O; PAHS: 8.9+/-2.6 cmH2O; p<0.01, mean+/-SD). We found no difference in sleep quality, nocturnal saturation and apnoea/hypopnoea index, or in daytime vigilance tests between the two groups at the end of the treatment period. However, there was a significantly greater scattering in the changes of sleep latency in group II than in group I. This was associated with a significant difference in the daily duration of nasal CPAP use between the two groups (group I: 7.29+/-0.95 h x day(-1); group II: 6.01+/-0.94 h x day(-1); p=0.01) and with a positive correlation between final maintenance of wakefulness test values and the duration of CPAP use (p<0.05; r=0.55). These results tend to show that correcting flow limitation is associated with a higher observance and a more important efficiency in normalizing daytime vigilance than with conventional nasal continuous positive airway pressure.     

Donor site morbidity following vascularized fibular grafting

Nasal continuous positive airway pressure (CPAP) therapy is usually effective in the treatment of obstructive sleep apnea (OSA), reversing the excessive daytime sleepiness associated with OSA. We investigated how polysomnography and maintenance of wakefulness test (MWT) predicted response to CPAP therapy in 10 patients with obstructive sleep apnea and 10 healthy controls. After a full polysomnography and MWT the patients were started on CPAP. MWT was repeated to quantify the treatment effect. Oxygen desaturation index and the percentage of slow wave sleep were the best predictors for baseline S1 latency in MWT. Baseline S1 latency in the MWT was the most important determinant of improvement in MWT S latency after CPAP, followed by the latency to 10 min of continuous nocturnal sleep, arousal index and CPAP use. We suggest that in mild sleep apnea, knowledge of sleep architecture is not necessary before deciding whether or not to initiate CPAP treatment.     

Venous leg ulcers. Part 1: Aetiology

Cardiogenic pulmonary edema is a frequent cause of reparatory failure. We investigated the effects of nasal continuous positive airway pressure (CPAP) in patients with severe pulmonary edema associated with acute myocardial infarction. Twenty-nine consecutive patients were divided into 3 groups: firstly, 7 intubated patients who received mechanical ventilation at study entry comprised the intubation group. The rest of the patients were randomly assigned to either of the following 2 groups: 11 patients who received oxygen plus CPAP delivered by a nasal mask (CPAP group), and 11 patients who received oxygen only via face mask (oxygen group). All patients in the intubation group had cardiogenic shock. Two patients (18%) in the CPAP group and 8 patients (73%) in the oxygen group required mechanical ventilation with endotracheal intubation (p=0.03). The hospital mortality rate in the CPAP group (9%) was significantly lower than the oxygen group (64%, p=0.02). The pulmonary artery wedge pressure and heart rate were significantly lower in the CPAP group than in the oxygen group 24 h after study entry (p<0.05 and p<0.01). The mean pulmonary artery pressure 48 h after study entry was 18+/-5 mmHg in the CPAP group and 25+/-8 mmHg in the oxygen group (p<0.05). The PaO2/FiO2 ratio increased in the intubation group (168+/-69 to 240+/-57, p<0.05) and the CPAP group (137+/-17 to 253+/-67, p<0.01) 24 h after study entry. Arterial plasma endothelin-1 concentrations decreased significantly earlier in the CPAP group than in the oxygen group (p<0.05). In patients without cardiogenic shock, nasal CPAP lead to an early improvement in oxygenation and hemodynamics, and decreased the mortality rate. Early and active respiratory management is recommended in patients with pulmonary edema associated with acute myocardial infarction.     

Sleep apnea and hypertension--what a mess!

It is unarguable that obstructive sleep apnea (OSA) causes pulsatile hypertension during sleep, but whether there is significant carryover of hypertension into waking hours is far from clear. It is perhaps more useful to consider whether OSA is related to the consequences of hypertension (e.g. stroke), since both nocturnal and daytime hypertension could be responsible for these. Furthermore, the effects of nasal continuous positive airway pressure (CPAP) on hypertension (or its consequences) must be assessed by randomized controlled studies, in exactly the same way as trials on hypotensive drugs would be carried out, before treatment is prescribed for OSA in the absence of any daytime symptoms.     

Secondary obstructive sleep apnea syndrome in a patient with tracheal stenosis and bilateral recurrent paresis. Successful treatment with nasal continuous positive airway pressure therapy

HISTORY AND ADMISSION FINDINGS: A 67-year-old woman complained of marked daytime sleepiness, as well as loud snoring and apnoeas during sleep. She was known to have had 3 thyroidectomies for goitre 41, 23 and 12 years ago, with known tracheal stenosis and recurrent nerve palsy for 11 years. Physical examination revealed marked stridor, hoarse voice and slightly enlarged and palpable recurrent right thyroid. INVESTIGATIONS: Polysomnography demonstrated a clearly elevated obstructive sleep apnoea activity (apnoea index: 34/h, apnoea-hypopnea index: 40/h, desaturation index: 31/h, minimal saturation: 63%). Selective tracheal imaging showed subglottic tracheal stenosis with an inspiratory luminal diameter of 4 mm and an expiratory luminal diameter of 8 mm. Lung function analysis revealed marked flattening of the flow-volume curve as sign of a functionally effective tracheal stenosis. These findings indicated a secondary obstructive sleep apnoea (OSA) due to tracheal stenosis and bilateral recurrent nerve palsy. The patient declined further studies, such as bronchoscopy. TREATMENT AND COURSE: As the patient did not want any surgical treatment, nasal continuous positive airway pressure therapy (CPAP) was instituted as a trial. No apnoea occurred at a pressure of 12 mm H2O and this was well tolerated. She has now continued CPAP at home for 12 months and her vigilance was markedly improved. CONCLUSIONS: Tracheal stenosis or recurrent nerve palsy is a rare cause of OSA which can be effectively treated by nasal CPAP.     

Obstructive sleep apnea and related disorders

OSAS, a common cause of disrupted sleep and EDS, result from repetitive closure of the upper airway during sleep. It probably represents the most severe syndrome related to obstruction of the upper airway; less severe forms include UARS, a syndrome characterized by the need for increased effort to breath but no prominent apneas or hypopneas, and primary snoring. Initial clues to the presence of OSAS and related disorders are derived from the history and include loud snoring, EDS or insomnia, and witnessed apneas. Some patients, especially women, may complain mostly of tiredness or fatigue, and children may present with behavioral abnormalities. Obesity, a large neck circumference, and a crowded oropharynx are common on physical examination. Nonobese patients, in particular, often have retrognathia, a high-arched narrow palate, macroglossia, enlarged tonsils, temporomandibular joint abnormalities, or chronic nasal obstruction. The clinical suspicion of obstructed nocturnal breathing is confirmed by overnight polysomnography, and an MSLT may be used to assess sleepiness. Esophageal manometry during polysomnography facilitates diagnosis of UARS. Treatment most commonly consists of nasal CPAP or BPAP, although problems with compliance make surgical treatment preferable in some cases. Although UPPP eliminates sleep apnea only in a minority of patients, combining UPPP with maxillofacial procedures appears to improve outcomes. Other treatments such as the use of dental appliances or medications, weight loss, and positional therapy may be useful as adjunctive therapy for moderate to severe OSAS or as primary treatments for UARS or mild OSAS.     

Oxidation in liposomes from egg phosphatidylcholine loaded with L-3,4-dihydroxyphenylalanine (DOPA) and dopamine: mutual effect of components

Effectiveness of continuous positive airway pressure (CPAP) as a treatment of obstructive sleep apnea can be limited by poor compliance, but little is known about how to improve compliance. We performed a randomized, controlled clinical trial among 33 subjects of two interventions to improve compliance. One group of subjects received weekly phone calls to uncover any problems and encourage use, another received written information about sleep apnea and the importance of regular CPAP use, and a third served as control subjects. We found that intervention improved CPAP compliance (p = 0.059) and that the effect was particularly strong when intervention occurred during the first month of CPAP treatment (p = 0.004). Although the sample size did not allow definitive investigation of other explanatory variables, subjects with lower levels of education or those with relatives who used CPAP may have benefited from intervention more than other subjects. We conclude that simple, inexpensive efforts to improve compliance with CPAP can be effective, especially when applied at the start of CPAP treatment, but optimal intervention may vary with certain patient characteristics.