Limitations of exercise tolerance in patients with IPF

In patients with idiopatic pulmonary fibrosis (IPF), the exercise limitation has been associated with mechanical constrain of ventilation and oxygen desaturation during cardiopulmonary exercise test (CPET). Furthermore V/Q disbalance has been described in those with complicated pulmonary hypertension (PH). We tried 1) to investigate limits of exercise tolerance in 52 patients with IPF and 2) to detect PH and to test how supplemental oxygen can affect exercise tolerance in those with significant oxygen saturation (SpO2) drop during CPET. 52 patients (17 females) with diagnosed IPF according to ATS/ERS criteria (VC 69,2±16% pred., TLCO 49,2±14,0%pred.) underwent measuring of pulmonary function tests and breath-by-breath measurement of flow, volumes and O2 and CO2 concentration during standard CPET. Ten of them (3 females, VC 67,5±10,1% pred., TLCO 43,5±13,2%pred.) underwent repeated CPET with FIO2 of 0,35, and right heart catheterisation. PeakVO2 (%predicted) showed positive correlation to VT/VC ratio (p 25 mmHg. PH was associated with higher VE/VCO2 ratio ant lower KCO. Supplemental oxygen increased exercise tolerance, decreased physiological dead space (VE/VCO2 at AT, fig.2, p=0,0078), and ventilatory demand during CPET (peakVE, p=0,0078), mainly in those with complicating PH. Exercise tolerance in IPF seems to be limited mainly by mechanical constrain of ventilation and/or high dead space ventilation, while hypoxemia plays a minor role. The second limit can be decreased by supplemental oxygen.