There have been approximately only 800 patients with diagnosis of SAS (sleep apnea syndrome) by polysomnography over recent several years in 25 institutions in Japan. This was obtained by the meeting for sleep disordered breathing found recently. In contrast, in North America some a hundred thausand patients with SAS are estimated, and about a half of them have got treatment for SAS with overt clinical symptoms annually. There is tremendous difference of the incidence between two areas, and this may attribute to relatively unawareness of SAS in our country. In this review, in addition to this syndrome's outline, we also describe the most important issues of SAS, among which are as follows.
First, SAS has been diagnosed by using Guilleminault's criteria more than a decade in almost all hospitals anywhere in the world. However, senile subjects tend to be overdiagnosed as having SAS, because apnea number per unit time steeply increases with age especially in case of patients, whose ages are more than 60 year-old. To avoid this, more appropriate criteria based on necessity of treatment should be established as soon as possible.
Secondly, recent papers have observed the similarity of the initializing mechanism between in OSA (obstructive sleep apnea) and CSA (central sleep apnea), both of which had considered as having distinct mechanisms to elicit each type of apnea. Despite this similarity in mechanism between OSA and CSA, we do not know why one patient proceed to OSA and another patient get CSA. Accordingly more detail mechanism should be elucidated intensively.
Thirdly, although numerous therapeutic approaches have been used for the treatment of SAS over a couple of decades, all approaches without tracheostomy and nasal CPAP could not have shown their satisfactory effects on SAS. For instance, effects of drugs which stimulate ventilation (e. g. progesterone derivatives, acetazolamide), have been found unsatisfactory on SAS. On the other hand, tracheostomy and nasal CPAP have been established as the best approach to treat them. And in these days, nasal CPAP has been thought as the best for SAS patients from cosmetic point of view and its relatively safety compared with tracheostomy. However, the long-term effect of nasal CPAP should be confirmed.
Finally, although a number of facts concerning about SAS have been elucidated in recent years, there are many things related to SAS still remain unknown. Therefore, as we have to evaluate SAS patients throughly and have to decide precisely whether patients should be treated or not, we hope this review can help you to recognize how serious the complication of SAS could be.

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For diagnosis of sleep apnea syndrome (SAS), there are three important steps wihch we have to consider. As the first step, we have to derive the following clinical symptoms from repeated questioning of patients and their families, for example, snoring, morning headache, daytime sleepiness, general fatigue, dyspnea, abnormal behavior during sleep or nocturnal enuresis, etc. Furthermore, we have to consider background diseases and complications. As the second step, it is necessary to take a screening test for patients, who are thought to have breathing disorders of sleep. We have developed a home sleep monitoring system which is very useful for a screening test. Home sleep monitor is consisted of two thermisters for mouth and nasal flow, a microphone for tracheal sound, three electrodes for electrocardiogram, amplifiers and microcomputer. The weight of this device is 280g. This device is equipped just before patient goes to bed, and brought back to hospital on the following day. Data such as trend display of apnea episodes, histogram of apnea episodes or trend display of heart rate are analyzed by a personal computer. As the third step, patient who is suspected of SAS by a screening test needs polysomnography to get correct diagnosis for SAS after admission to hospital. By polysomnography, we can obtain the informations of sleep stage, apnea type, degree of desaturation or hemodynamics during sleep.

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In recent years many attentions have been focused on the sleep apnea. We reported 5 cases of obstructive sleep apnea in children, 3 to 6 years of age. They were diagnosed by means of nocturnal polygraphic monitoring (polysomnograms). All cases revealed the partial airway obstruction due to enlarged tonsils and adenoids as a recognized clinical entity. Features of the sleep apnea syndrome were conspicuous snoring, and frequent apnea during sleep. Case No. 1 had cardiomegly in association with chronic nasopharyngeal obstruction. Tonsillectomy and adenoidectomy were performed in all children and the clinical improvement following adenotonsillectomy has been impressive.

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Acoustic reflection technique (AR) was applied to evaluate the pharyngeal space and its behavior responding to various stresses in obese patients and patients with obstructive sleep apnea (OSA). Pharyngeal space was narrower and its wall was more compliant in obese patients and patients with OSA than those of control patients. Whether the patient is obese or not, it is an important finding of AR that the pharyngeal wall of patients with OSA was more compliant than that without OSA. This fact was observed in the following conditions; natural breathing, pressure load in the upper airway during natural breathing, positional change of the body. AR is a non-invasive and useful tool to evaluate the role of pharyngeal space in sleep apnea.

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Recently, it was recognized that cardiac arrythmia or pulmonary hypertension (PH) was occurred during apnea in patients with sleep apnea syndrome (SAS), and those cardiopulmonary disorders might influence the prognosis of SAS. But the frequency and the mechanisms of PH have not been well known. Therefore, we carried out a polysomnographic sleep study, including continuous recordings of pulmonary artery pressure, systemic artery pressure and cardiac output in 11 patients with obstructive SAS.
Only 2 of 11 patients (19%) showed pulmonary hypertension during daytime (P_PA≥20Torr). Blood gas analysis of these patients showed hypoxemia and hypercapnemia: PaO₂ 48.1Torr, PaCO₂ 48.6Torr and PaO₂ 57.9Torr, PaCO₂ 50.9Torr, respectively. It was suggested that only the SAS patient with hypoxemia and hypercapnemia during wakefullness was a candidate for pulmonary hypertension during daytime. Precise analysis of hemodynamic recordings during apneic phase from a case of primary alveolar hypoventilation syndrome and a case of obstructive sleep apnea syndrome showed significant contribution of hypoxic pulmonary vasoconsriction to the development of severe pulmonary hypertension during apnea in these patients. And the effect of intrathoracic pressure oscillations with distinct intrathoracic suction during obstructive apnea on the pulmonary hemodynamic changes was discussed.

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Satisfactory results in the treatment of obstructive sleep apnea syndrome (OSAS) depend on precise diagnosis of the site and the severity of obstruction and application of the proper treatment. History-taking including sleep behavior, local and general physical examinations, X-ray examination, fluoroscopy, fiberscopy, polysomnography give us very useful informations for this decision. Among these, polysomnography is the most useful.
OSAS is treated conservatively or operatively as indicated case to case. Among the conservative treatments, body weight reduction with hypocaloric diet is essential in the obese. Nasal CPAP is widely used and known to be effective, however, its long-lasting use is problematic. Medications of antibiotics and antiallergica are useful for reduction of mucosal swelling caused by inflammatory and allergic reactions. Application of a dental prosthesis protruding the mandible is effective. Among the surgical treatments adenotonsillectomy is mainly performed on the infants and children with OSAS. If OSAS is created by intranasal pathologies, intranasal surgeries of various types are applied, when the causative region exists in the palato-pharynx, UPPP is very effective. Tracheostomy gives an instant relief on heavy obstructive dyspnea. If we encounter such heavily disturbed cases, we should not hesitate to do tracheostomy.

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Recent studies have shown that nasal CPAP is very effective in the treatment of patients with obstructive sleep apnea syndrome (OSA). In the present study, we examined the effects of short term nasal CPAP therapy in 10 cases of OSA patients. Nasal CPAP was used for 10 to 14 days and polysomnography was performed at two consecutive nights without nasal CPAP and at one night with nasal CPAP. Uchida-Kraepelin tests were performed before the initiation of nasal CPAP therapy and also 7 to 14 days after the nasal CPAP therapy. Apnea index reduced significantly in all cases from 49.0±20.3 episodes/hour without therapy to 3.1±3.3 with nasal CPAP (P<0.001). Nasal CPAP significantly reduced the frequency of obstructive and mixed apnea (P<0.01), but the frequency of central apnea did not change with nasal CPAP. During the nasal CPAP, mean nadir SaO₂ rose from 87.4±2.7% to 92.5±1.3% (P<0.001) and lowest SaO₂ rose from 74.0±5.5% to 91.8±2.5% (P<0.001). Uchida-Kraepelin test revealed significant increment of average marks after short term treatment of nasal CPAP (P<0.001). We conclude that nasal CPAP therapy during sleep is an effective and non invasive therapy for patients of OSA, and may lead to rapid recovery of mental function after short term treatment.

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Sleep respiratory disorder in children is frequently attributable to upper airway obstruction due to tonsillar hypertrophy. Children with sleep respiratory disorder sometimes have chest deformity such as funnel chest or pigeon chest, suggesting that upper airway obstruction can affect the respiratory system.
Using the measurement of the mesopharyngeal pressure while asleep, we recently studied the relationship between upper airway obstruction and chest deformity. In children with tonsillar hypertrophy, we examined the presence or absence of chest deformity and assessed the degree of upper airway obstruction based on the mesopharyngeal pressure. In 33 children in whom chest deformity was found, the shape of the thorax was observed for a long period after adenotonsillectomy.
The following results were obtained. (1) Most of the children with chest deformity had sleep respiratory disorders such as snoring, retracting respiration and sleep apnea. (2) The incidence of chest deformity was elevated as the mesopharyngeal pressure amplitude became higher. (3) In most cases, the chest deformity gradually improved within several years after adenotonsillectomy. (4) Upper airway obstruction due to tonsillar hypertrophy seemed to be one of the main causes for chest deformity.

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Generally, it has been recognized that the clinical time-course of thyroid malignancy is prolonged and its prognosis is better than that of malignancy of other organs. However, an extensive surgical treatment should be necessary in the case with thyroid cancer invading the adjacent organs, such as the larynx, trachea and esophagus. One hundred and forty-five cases with thyroid gland tumors including 95 benign and 50 malignant tumors had been surgically treated in the Department of Otolaryngology, Kitasato University Hospital during the last 16 years. Fifteen out of 145 cases (10.3%) showed the tumor invasion to the trachea, larynx, hypopharynx and/or esophagus. They were two males and 13 females, with age ranging from 28 to 83 years (the average age of 63).
Histopathological examination revealed papillary carcinoma in 9 cases, mixed papillary-follicular carcinoma in 3 cases and follicular carcinoma, anaplastic carcinoma and osteosarcoma in each one case. Their clinical features were discussed retrospectively. All cases were roentgenographically classified into three groups by the degree of tracheal distortion before surgery and the prognosis was precisely investigated in each group after surgery. From the present investigation, it is concluded that a correct estimation of the extent of the tumor invasion before surgery is the most important to get a good prognosis.

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Recently, the authors experienced a case of the tracheal stenosis probably caused by repeated digital pressure on the trachea.
A 52-year-old man was admitted to the Self Defense Force Kumamoto Hospital with complaint of dyspnea after common cold and cured by antibiotic therapy in 1972. Since then, he has gotten into a habit of pressuring the suprasternal region with the left thumb when expectorated. The patient has no respiratory symptoms for approximately 10 years until 1983, when he noticed again dyspnea and stridor, especially in heavy exercise. Fiberoptic bronchoscopy and computed tomography revealed a stenosis from the 1st to the 5th tracheal ring. No anti-cartilage antibody was found in the serum.
Stenotic lesions were resected partly through tracheofissure and a T-tube was placed into the revised tracheal lumen. Any inflammatory findings were not obtained histologically from the resected tracheal wall.
His present illness, past history, surgical findings and various examinations suggested that the tracheal stenosis was probably induced by a habit of repeatedly pressuring the suprasternal region with thumb when expectorated for a long time.

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