Flow volume loops: postural significance.

ABSTRACT

Upper airway obstruction is an important but often unrecognised cause of dyspnoea and ventilatory failure. Flow volume loop remains the most sensitive method to detect upper airway obstruction. We report a patient with Hashimoto's thyroiditis who showed evidence of upper airway obstruction on the flow volume loop only in the supine position. It is important to recognise as it may be missed during the conventional method of performing a pulmonary function test in sitting posture and also because surgical intervention should be considered in patients with tracheoesophageal compression due to a thyroid swelling.