Singh V, Chowdhary R, Chowdhary N
Department of Pulmonary Medicine, SMS Medical College, Jaipur-302 016, India.
J Assoc Physicians India. 2000 Mar;48(3):343-5.
Air flowing through a pipe exerts frictional stress on the walls of the pipe. Frictional stress of more than 40 N/m2 (velocity equivalent of air 113 m/s) is known to cause acute endothelial damage in blood vessels. The frictional stress in airways during coughing may be much greater, however, since the velocity of air may be as high as speed of sound in air. We suggest that high levels of frictional stress perpetuate airway inflammation in airways which are already inflamed and vulnerable to frictional stress-induced trauma in patients with asthma. Activities associated with rapid ventilation and higher frictional stress (e.g. exercise, hyperventilation, coughing, sneezing and laughing) cause asthma to worsen whilst activities that reduce frictional stress (Yoga 'Pranayama', breathing a helium-oxygen mixture and nasal continuous positive airway pressure) are beneficial. Therefore control of cough may have anti-inflammatory benefits in patients with asthma.
流经管道的空气会对管道壁施加摩擦应力。已知摩擦应力超过40 N/m²（相当于空气流速113 m/s）会导致血管内皮急性损伤。然而，咳嗽时气道内的摩擦应力可能会大得多，因为空气流速可能高达空气中的声速。我们认为，高水平的摩擦应力会使已经发炎且易受摩擦应力诱导创伤影响的哮喘患者气道炎症持续存在。与快速通气和较高摩擦应力相关的活动（如运动、过度通气、咳嗽、打喷嚏和大笑）会使哮喘恶化，而降低摩擦应力的活动（瑜伽“调息法”、呼吸氦氧混合气和经鼻持续气道正压通气）则有益。因此，控制咳嗽可能对哮喘患者具有抗炎作用。
