Periodic breathing during hypoxia altitude simulation test

A 79-year-old slender female patient presented at the pulmonary function laboratory to perform a hypoxia altitude simulation test (HAST). It was indicated on the basis of her intention to travel by plane and a diagnosis of idiopathic pulmonary fibrosis (IPF). She was a former smoker and had a history of arterial hypertension. Her only symptoms were mMRC grade 2 dyspnoea and cough. The test was performed at sea level through a tightly fitting facemask, attached to a pneumotachograph and a two-way non-rebreathing valve. Dead space of the circuit was 120 mL. Airflow, heart rate, inspired oxygen and carbon dioxide fraction were continuously recorded. Pulse oximetry (SpO2) was recorded trough a finger probe (Massimo Radical 7, California, USA). In the sitting position, the patient breathed ambient air (inspired oxygen percentage=21%) …