Wheezing

Japanese: 喘鳴

Concept and mechanism: Wheezing is a continuous sound that occurs when the air passing through the narrowed airway forms turbulent flows and vibrates, or when the mucus causing the narrowing vibrates; it can be heard by the patient or by the examiner. It is different from continuous rales (wheezes or rhonchi) heard on auscultation. Patients often complain of "wheezing and whistling sounds and difficulty breathing." Wheezing that occurs in the larynx is called stridor, and is often distinguished from sounds that occur in the lower respiratory tract. Wheezing that occurs in the intrathoracic airways is easy to hear during the expiratory phase, when intrathoracic pressure rises and the narrowing of the airway intensifies, but as the narrowing becomes more severe, it can also be heard during the inspiratory phase. As the narrowing becomes more severe, the airflow passing through decreases, and wheezing becomes less audible.
Causes and clinical tests Causes of wheezing include spasm of bronchi and bronchioles, narrowing of the airway due to thickening and edema of the airway wall, accumulation of secretions, and narrowing of the airspace due to tumors or foreign bodies. Table 2-36-1 shows the diseases that cause each of these. As a method of differentiation, bronchi and bronchiolar spasm is proven by improvement with the use of bronchodilators. Diseases that increase lung compliance exhibit obstructive ventilation disorders, and low attenuation areas (LAA) and emphysematous cysts may be seen on CT scans. Thickening of the airway wall has recently become possible to evaluate with high-resolution CT. Airway narrowing due to tumors and narrowing of the airspace due to foreign bodies or sputum can be confirmed by CT or bronchoscopy. Fixed narrowing of the airway due to tumors or foreign bodies is present inside the thorax if the flow-volume curve flattens during expiration, and is present outside the thorax if the flow-volume curve flattens during inspiration. Vocal cord dysfunction, which must be differentiated from refractory asthma, can be evaluated not only by laryngoscope but also by measuring the vocal cord diameter during inspiration and expiration using multi-slice CT.
Treatment : For asthma airway constriction, inhaled steroids, β2 agonists, and xanthine preparations are used, while for chronic obstructive pulmonary disease, anticholinergic drugs are frequently used in addition to these. In severe cases of both diseases, corticosteroids are used systemically. Diuretics are necessary for pulmonary congestion caused by left heart failure. For tumors or foreign bodies in the airways, bronchoscopy or stent insertion may be necessary. [Yamaguchi Etsuro]
■References <br /> Kimura Hiroshi, Yamada Yoshihito: Wheezing. Learn Pathophysiology with Charts, 2nd Edition (Kawakami Yoshikazu, et al.), pp42-43, Chugai Igakusha, Tokyo, 2000.

Table 2-36-1
Mechanisms of wheezing and causative diseases and triggers

Table 2-36-1

Source : Internal Medicine, 10th Edition About Internal Medicine, 10th Edition Information

Japanese:

概念・機序
　喘鳴とは気道に狭窄があるためそこを通過する空気が乱流を形成して振動したり，狭窄を起こしている粘液などが振動して発生する連続性の音で，患者自身あるいは診察者が耳で聴取できるものを指す．聴診上の連続性ラ音（wheezesやrhonchi）とは異なる．患者は「ぜいぜい，ひゅーひゅーと音がして息が苦しい」と訴えることが多い．喉頭で発生する喘鳴はstridorとよび，下気道から発生する音と区別することが多い．胸郭内気道から発生する喘鳴は，胸腔内圧が上昇し気道の狭窄が増強する呼気相で聴取しやすいが，狭窄が強くなると吸気相でも聴取される．狭窄が強くなると通過する気流が低下するために，喘鳴は逆に聞かれなくなる．
原因・臨床検査
　喘鳴の原因として，気管支・細気管支の攣縮，気道壁の肥厚・浮腫による気道の狭窄，分泌物の貯留，腫瘍や異物による気腔の狭小化などがある．それぞれをきたす疾患を表2-36-1に示す．鑑別法として，気管支・細気管支攣縮は，気管支拡張薬の使用で改善することにより証明される．肺コンプライアンスの上昇をきたす疾患では閉塞性換気障害を呈し，CTにてＸ線の低吸収領域（low attenuation area：LAA）と気腫性囊胞が認められることがある．気道壁の肥厚は，近年高分解能CTにより評価可能となってきた．腫瘍による気道狭窄，異物や喀痰による気腔狭小化は，CTや気管支鏡により確認される．腫瘍や異物による気道の固定性狭窄病変は，フローボリューム曲線で呼気時に平坦化すると胸郭内に存在し，吸気時に平坦化すると胸郭外に存在する．難治性喘息と鑑別が必要な声帯機能異常症は，喉頭鏡のほかに多列CTによる吸呼気時の声帯径を測定することでも評価可能である．
治療
　治療は喘息の気道攣縮に対しては，吸入ステロイドやβ2刺激薬，キサンチン製剤を使用し，慢性閉塞性肺疾患ではそれらに加えて抗コリン薬が頻用される．重症例では両疾患とも全身的に副腎皮質ステロイド薬が使用される．左心不全による肺うっ血では，利尿薬が必要である．気道内の腫瘍や異物に対しては，気管支鏡による処置やステント挿入が必要となる場合がある．［山口悦郎］
■文献
木村　弘，山田嘉仁：喘鳴．チャートで学ぶ病態生理学，第2版（川上義和，他編），pp42-43，中外医学社，東京，2000．

表2-36-1
喘鳴の機序と原因疾患，誘因">

表2-36-1

出典　内科学第10版内科学第10版について　情報

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