睡眠醫學二十八之阻塞性睡眠窒息症的顯型

我年青的時候很喜歡到書局打書釘，今天突然心血來潮要再扮” 偽”文青。想不到在書局的大眾心理學角落竟然遇到振華，他洋洋得意捧著一本關於「九型人格」的書。他興奮地分享從這本書學會將下屬分成九種類別，從而亦學會如何駕馭不同型格的下屬。但振華忽然問我能否同樣將阻塞性睡眠窒息症(OSA)分門別類，如此一來，醫治睡眠窒息症不就簡單直接得多了嗎?

雖然近年醫學界對OSA的認識增添了不少，但卻沒有制定什麼普世認同的分類。有個別學者把阻塞性睡眠窒息症分成多種顯型 (phenotypes is defined as an observable expression of an individual’s characteristics that result from the interaction between the individual’s genes (genotype)and the environment, without any implication of a mechanism) 。一如其名，顯型是指病人所顯露出來的表徵，而表徵是由遺傳因子和環境因素交錯而成的。

顯型的種類

年齡層

隨著病人年齡的增長，阻塞性睡眠窒息症愈見普遍，高峰期見於65歲，此後發病率大致平穩。病理是多樣化的(Reduced airway caliber due to preferential deposition of fat around the pharynx makes the aging population anatomically susceptible to OSA (1) Overnight rostral shift of fluids to the neck(2) higher surface tension of the upper airway(3) and decreases in lung volume tethering effect(4) also predispose the elderly population to OSA)。而老齡的OSA病人有別於年青的OSA病人(5):日間嗜睡較輕微；細的肺容量引起圈養後果(tethering contributes to airway collapsibility)；夜間咀唇液體移位(overnight rostral shift of fluid) 較普遍。

更年期

更年期後的婦女患上睡眠窒息症的機會大增(6)，有別於年青婦女患者，她們在Non Rapid Eye Movement [NREM] Sleep 時病情特別嚴重(7)，賀爾蒙補允藥有助減少更年期後的婦女患上OSA的機會(8) 。

種族

亞洲OSA患者較多有顱面骨架異常(Craniofacial skeletal restriction)，而美國非洲裔(African Americans)患者則多因肥胖引起發病，另外(Caucasians) 高加索人種患者同時因顱面骨架異常及肥胖引起發病(9)。所以有不少亞洲OSA患者並不如外國患者般肥胖(10,11) 。

睡眠階段

有個別患者的睡眠窒息主要(predominant)或單單(isolated)發生在Rapid Eye Movement , REM Sleep，約10至36% OSA病人屬這類別(12)。患者多為年長婦女而且她們的病情亦較嚴重(13,14)，這類的睡眠窒息症(REM-related OSA) 特別與高血壓有關(15)。

睡姿

與平臥有關(supine position -related) 的OSA 是相當常見的，其流行率(prevalence) 為20至60%(16)。病理主因乃上呼吸道結構及功能異常( It may be attributable to unfavorable upper airway anatomy, reduced lung volume, and inability of airway dilator muscles to compensate for the airway collapse in the supine position.)。患者多為年青男士，亦非肥胖，可是他們卻出現較嚴重的日間嗜睡(7)。治理這類型病人可考慮側睡(17)、鈄睡(18)。如果這屬病人不想使用連CONTINUOUS POSITIVE AIRWAY PRESSURE THERAPY[CPAP]/持續正壓呼吸機，亦可試用 Mandibular Advancement Devices (MAD)下頜前移矯治器。

上呼吸道狹窄症候群 (Upper Airway Resistance Syndrome)

病人由於上呼吸道狹窄，因而在睡眠中呼吸遇到阻力，最終引致睡夢中覺醒(Respiratory Effort Related Arousal) (19)，但病變機理又未符合睡眠窒息(Apnoea)或低通氣(Hypopnea) 的定義。典型患者是非肥胖年青人士，及有多種顱面骨架異常(Craniofacial abnormalities include low soft palate, long uvula, increased overbites, and a high and narrow hard palate)。

我輕輕拍了振華的膊頭，其實任何疾病的病人都不可能用幾種顯型就可慨括的! 唯一較實際的分類: 老闆(振華)及打工仔(小弟)。

參考文獻:

1.  Aging influences on pharyngeal anatomy and physiology: the predisposition to pharyngeal collapse. Am J Med. 2006;119:72.e9–e14.

2.  Relationship between overnight rostral fluid shift and obstructive sleep apnea in nonobese men. Am J Respir Crit Care Med. 2009;179:241–246.

3.  Relationship between surface tension of upper airway lining liquid and upper airway collapsibility during sleep inobstructive sleep apnea hypopnea syndrome. J Appl Physiol (1985). 2003;95:1761–1766

4.  Effect of increased lung volume on sleep disordered breathing in patients with sleep apnoea. Thorax. 2006;61:435–439.

5.  Obstructive sleep apnea in older adults is a distinctly different physiological phenotype. Sleep. 2014;37:1227–1236

6.  Menopausal status and sleep-disordered breathing in the Wisconsin Sleep Cohort Study. Am J Respir Crit Care Med. 2003;167:1181–1185.

7.  Phenotypes of patients with mild to moderate obstructive sleep apnoea as confirmed by cluster analysis. Respirology 2012;17:99–107.

8.  Prevalence of sleepdisordered breathing in women: effects of gender. Am J Respir Crit Care Med. 2001;163:608–613.

9.  Obesity and craniofacial structure as risk factors for obstructive sleep apnoea: impact of ethnicity. Respirology 2012;17:213–222.

10.A community study of sleep-disordered breathing in middle-aged Chinese women in Hong Kong: prevalence and gender differences. Chest. 2004;125:127–134.

11.Excess weight and sleep-disordered breathing. J Appl Physiol (1985). 2005;99:1592–1599

12.Prevalence, clinical features, and CPAP adherence in REM-related sleep-disordered breathing: a cross-sectional analysis of a large clinical population. Sleep Breath. 2012;16:519–526.

13.Gender differences in the polysomnographic features of obstructive sleep apnea. Am J Respir Crit Care Med. 2000;161:1465–1472

14.Gender differences in obstructive sleep apnea and treatment implications. Sleep Med Rev. 2008;12:481–496.

15.Obstructive sleep apnea during REM sleep and hypertension results of the Wisconsin Sleep Cohort. Am J Respir Crit Care Med. 2014;190:1158–67

16.Prevalence and clinical significance of supine-dependent obstructive sleep apnea in patients using oral appliance therapy. J Clin Sleep Med. 2014;10:959–964.

17.Positional treatment vs continuous positive airway pressure in patients with positional obstructive sleep apnea syndrome. Chest. 1999;115:771–781.

18.Effects of sleep posture on upper airway stability in patients with obstructive sleep apnea. Am J Respir Crit Care Med. 1997;155:199–204.

19.The upper airway resistance syndrome. Chest. 1999;115:1127–1139.

師公葉準師傅大壽2018