Introduction Cognitive deficits in patients suffering from chronic obstructive pulmonary disease (COPD) have been described and hypoxaemia has been addressed as a possible cause. Cognitive functions in patients with interstitial lung disease (ILD) are not well studied. These patients are taking part in everyday traffic, but little is known regarding their driving performance. This study was conducted to determine the driving performance in patients with COPD and ILD, respectively compared to healthy controls using a driving simulator. Additionally, the effect of oxygen supply was addressed.

Methods 16 patients with COPD (8 receivers and 8 non-receivers of long-term oxygen therapy (LTOT)), 8 patients with ILD (consisting of idiopathic interstitial pneumonias) and 8 healthy controls were tested in a driving simulator. Each test lasted 45 min. In the oxygen intervention part of the study the patients were randomised to receive oxygen therapy in the first or second test and acted as their own controls.

Results Patients with COPD had significantly impaired driving performance when comparing SD from the centre of the road and number of off-road events to controls. Patients with COPD receiving LTOT performed significantly worse than those not receiving LTOT when comparing SD and worse than the patients with ILD when comparing SD and off-road events. Patients with ILD performed similarly to controls (SD: LTOT 2.39*; no LTOT 0.69*; ILD 0.37; controls 0.36; *p<0.05. Off-road: LTOT 226.67*; no LTOT 78.92*; ILD 40.00; controls 25.78; *p<0.05). Oxygen therapy had no effect on driving performance.

Conclusions Patients with ILD performed similarly to controls in the driving simulator, whereas patients with COPD showed decreased driving performance, especially those receiving LTOT. Doctors should be aware of this when renewing the driving license of patients with COPD. Oxygen therapy showed no effect on driving performance.

Trial registration number NCT02125916