An occult cause of dyspnoea

Discussion

A 69 year old man presented to the emergency department with severe dyspnoea. His medical history included adult onset asthma. Arterial blood gas analysis showed acidosis (pH 7.10), acute type 1 respiratory failure, and a lactate of 5.1 mmol/L. He was treated for an exacerbation of asthma. On the fifth day, his symptoms had not improved, stridor was audible, and he had a respiratory arrest. Computed tomography of the neck was performed (fig 2⇓). A large compressive multinodular thyroid gland was resected. After he recovered from surgery his presenting symptoms resolved.

Fig 2 Computed tomogram of the neck showing a large compressive multinodular goitre (A)

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Upper airway compromise can be demonstrated by peak expiratory flow and the ratio of the peak expiratory flow to the forced expiratory volume in one second when more than 50% of the tracheal area is involved. However, symptoms usually present only when more than 75% of the trachea is occluded.1 2 Thyroid goitre has been reported to be the cause of clinically detectable upper airway obstruction in 33% of these patients.3 Peak expiratory flow will increase after treatment with a bronchodilator in patients without an airway obstructing goitre, so the response to such treatment can differentiate between those with and without a goitre. The possibility of concomitant upper airway compromise on background chronic airflow limitation should be taken into account in the investigation of patients presenting with unremitting dyspnoea.4