Abstract
For the diagnosis of the upper airway obstruction, flow volume (FV) curve provides useful informations, since it shows a characteristic pattern. However, it may be difficult to identify the pattern when forceful expiration is not sufficiently performed or when the patient has a mild impairment of upper airway diseases. The purpose of the present paper was to study the utility of the He-O2 FV curve for the diagnosis of the upper and central airway obstruction and for the detection of the extent of obstruction. In this study, six healthy subjects and fourty nine patients with upper airway diseases (vocal cord polyp, vocal cord paralysis, cancer of ralynx), were examined. In order to simulate the upper airway obstruction, external resistance tubes with the inner diameters ranging from 4 to 15mm were inserted to the air passage. 1) Even when the external resistance increased, FVC did not change. 2) FEV1.0 showed no substantial change when the inner diameter was larger than 6mm, however it obviously decreased when the inner diameter was 5mm or less. 3) FEV1.0/PF ratio increased as the inner diameter decreased and the increase of this ratio became distinctive when the inner diameter was under 7mm reaching 10ml/l/min or more. 4) ΔPF increased as the inner diameter decreased, and the increment was significant when the inner diameter was less than 9mm. 5) Upper airway impairment of vocal cord polyp, vocal cord paralysis and cancer of larynx were detected by FEV1.0/PF and ΔPF of air FV curve and He-O2 FV curve. 6) The He-O2 FV curve was considered to be useful for the diagnosis of the upper airway obstruction.
