The Quarterly journal of medicine
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In 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. ⋯ 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.