Work-Exacerbated Asthma

Work exacerbated asthma is pre-existing or coincident asthma that is worsened by workplace conditions, without new sensitisation to a workplace agent. It differs from occupational asthma, which is caused by work.

Epidemiology. Roughly 15 to 25% of working adults with asthma report work related worsening. It is more frequent than occupational asthma caused by work.

Triggers. Irritant gases and fumes, dust, cold or dry air, physical exertion, strong odours, cleaning products, tobacco smoke and workplace stress.

Risk groups. Cleaners, healthcare staff, construction workers, workers in dusty or cold environments, and those with poorly controlled asthma.

Importance. It causes lost work, reduced productivity and exacerbations. Exposure removal is not always needed and many workers can stay in post with controlled conditions.

Pathophysiology.

Airway hyperresponsiveness and chronic inflammation lower the threshold for irritant and non-specific triggers. Exposure produces bronchoconstriction and increased mucus.

Cold air and exertion act through airway cooling and drying and mediator release. No specific immunological sensitisation to a work agent is involved.

• Existing asthma with increased cough, wheeze or dyspnoea at work or after work, and recovery on holiday.
• Symptoms often occur after particular tasks or products.
• Examination may be normal between attacks.

Red flags.

• Frequent severe attacks, hospital attendance or oral corticosteroid use.
• Persistent symptoms despite good adherence.

• Confirm asthma by spirometry with reversibility of 12% and 200 mL, peak flow variability, FeNO or methacholine challenge.
• Work history with tasks, products, ventilation and co-worker symptoms.
• Serial peak flow at least 4 times daily over at least 2 weeks at work and 2 weeks away. A work related pattern with pre-existing asthma and no new sensitiser supports work exacerbated asthma.
• Specific inhalation challenge in a specialist centre when it is unclear whether a work agent has caused asthma.

Differential diagnosis. Occupational asthma caused by sensitisation, irritant induced asthma, vocal cord dysfunction, chronic obstructive pulmonary disease, rhinitis, gastro oesophageal reflux, cardiac disease.

• Optimise control and inhaler technique; identify and reduce triggers; engineering controls, ventilation and task changes; respirator as an adjunct.
• Budesonide with formoterol 200/6 micrograms inhaled, 1 inhalation twice daily as maintenance plus 1 inhalation as needed (adults and adolescents 12 and over). Usual maximum 8 inhalations in 24 hours, up to 12 for a short period. Monitor symptoms, spirometry, exacerbations and oral candidiasis; rinse mouth after use. No renal adjustment; step up or down by control.
• Exacerbation: salbutamol 100 microgram metered dose through a spacer, 4 to 10 puffs, repeated every 20 minutes for the first hour, then every 4 hours as needed. Maximum 10 puffs each dose. Monitor heart rate, potassium and oxygen saturation. Caution in arrhythmia and hyperthyroidism.
• Exacerbation: prednisolone 40 to 50 mg orally once daily for 5 days, with no taper. Maximum 50 mg daily. Monitor glucose and blood pressure. Caution in diabetes and peptic ulcer; acceptable in pregnancy when needed; no renal adjustment.
• Change of duty or workplace when symptoms persist despite good control and exposure reduction.

Monitoring. Review every 3 months until stable, then yearly; peak flow review if symptoms recur.

Referral and escalation. Occupational physician for workplace adjustment; respiratory physician for poor control or diagnostic doubt; notification where a work cause is established.

Special groups. Pregnancy: continue inhaled corticosteroid and avoid triggers.