• B D Harrison.
• Q. J. Med. 1976 Oct 1; 45 (180): 625-45.

AbstractIn sixteen patients with upper airway obstruction, breathlessness was a symptom in all with maximum mid vital capacity flow rates in inspiration or expiration of 1-7 litres per second or less. With one exception, all these patients had stridor. The stridor was inspiratory in nine, expiratory in one and both inspiratory and expiratory in two. There was no diagnostic difficulty in the twelve patients with extrathoracic airway obstruction and in this group tests of inspiratory flow (forced inspired volume in one second, peak inspiratory flow or maximum mid inspiratory flow) were of most value in following the progression of the disease and the response to treatment. Flow volume loops were particularly useful where extrathoracic obstruction and diffuse intrapulmonary airway obstruction co-existed. The two patients with intrathoracic upper airway obstruction caused considerable difficulty with diagnosis and both were initially thought to have, and treated unsuccessfully for, asthma. In each patient flow volume loops showed a low flow expiratory plateau, diagnostic of severe intrathoracic airway obstruction but recorded in the absence of any clinical or radiographic features of emphysema. An obstructing lesion of the intrathoracic trachea was therefore suspected and this was confirmed by tracheal tomography. In one patient serial expiratory flow volume curves demonstrated the combination of intrathoracic upper and lower airway obstruction. Two patients had tracheal stenosis in the region of the suprasternal notch. Each showed a characteristic twin humped expiratory flow volume curve and in one patient the stenosis was demonstrated both physiologically and radiologically to move in and out of the thorax. The importance of a standard posture during serial measurements is emphasized. The ratio of forced expired volume in one second measured in millilitres, to the peak expiratory flow measured in litres per minute, was of limited value if differentiating upper from lower airway obstruction in these patients. It is concluded that upper airway obstruction is likely to become more common and that respiratory function tests, in particular the flow volume loop, play an essential part in the recognition and management of this problem.

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