Exercise testing

Exercise test in a woman who presented for evaluation of dyspnea on running and a dry cough of 18 months duration. She did not smoke or have a history of lung disease. The chest x-ray and lung function tests were normal. Her resting room air arterial blood gases (elevation 5000 feet) revealed PO2: 78; PCO2: 34; pH: 7.43; Sat: 94 percent; AaO2: 3.8. The patient performed an exercise test on a cycle ergometer. The work rate was increased 10 watts per minute to her symptom limited maximum. Blood was sampled every minute from an indwelling catheter. Her resting and exercise ECG was normal. The patient achieved 94 watts (65 percent of predicted workload). The PO2 decreased, AaO2 increased, and minute ventilation (Ve) increased systematically with increasing work rate (shown as the percent of predicted maximal VO2). The study was stopped because of mild shortness of breath and leg fatigue. Lung biopsy revealed UIP.