6MWT performance by means of Spiropalm in patients affected by fibrotic idiopathic interstitial pneumonias: Preliminary observations

Abstract

Despite there is no definitive reference to the role of the 6-minute walk test (6MWT), it is frequently used to assess overall cardiopulmonary fitness and predict outcome in patients with diffuse interstitial lung diseases. Aim of the present study was to assess 6MWT performance with the Spiropalm devise (that allows a combined evaluation of lung function parameters and pulse-oxymetry) in a group of patients affected by clinically stable idiopathic pulmonary fibrosis (n=15) and fibrotic non specific interstitial pneumonia (n=8). Overall, there were 17 males with a mean age±SD: 65±9yrs. Twelve were ex-smokers. Significant O₂ desaturation was detectable in all cases (p<0.0001) with a mean distance walked of 404 m (78% of predicted) accounting for a 6MW work of 30685 kg*m. Ventilation and tidal volume were significantly increased at the end of 6MWT (15.3 vs 45.6 L/min and 0.6 vs 1.1 L, respectively), while the respiratory reserve was decreased (77 vs 35 %, p<0.0001). The distance-saturation product (DSP), that is the product of distance walked and lowest O₂ saturation, was 322±110 m%, while the desaturation-distance ratio (DDR), that is the ratio between the desaturation area (difference between maximal SpO₂ and patient's SpO₂ every 2 seconds) and distance walked, was 8.5±5.5. DDR was inversely correlated with both FVC and DLCO (r=-0.5, p=0.04, and r=-0.66, p=0.004). A positive correlation was instead found with the composite physiologic index (r=0.66, p=0.006). Spiropalm may be successfully applied to ameliorate 6MWT performance in fibrotic idiopathic interstitial pneumonias. Performance upon incremental oxygen supplementation should be investigated.