Metabolic alkalosis in a patient with dyspnoea

A 56 year old woman with poorly controlled asthma was admitted to hospital with a suspected lower respiratory tract infection, having become increasingly anxious and short of breath over the past 24 hours. She had been unwell for the past week, and her general practitioner had started her on amoxicillin and oral steroids. She was a never smoker, had a history of ischaemic heart disease and atrial fibrillation, and had a high body mass index. This was not the first time she had been admitted to hospital with an exacerbation of her asthma, having been admitted several times previously. Her regular drugs included fluticasone, salbutamol, furosemide, omeprazole, simvastatin, and diltiazem.

On examination she had a normal temperature, a respiratory rate of 26 breaths/min, sparse crackles at her left lung base, together with widespread expiratory wheeze. The table⇓ details her initial arterial blood gases on air and other blood test results.