Correlates of dyspnea in late onset Pompe disease (LOPD) patients: a pilot study

<bold>Background:</bold> most LOPD patients complain of dyspnoea despite enzyme replacement therapy. Dyspnea may be due to reduction in lung volumes. However, recent studies have shown that dyspnoea in neuromuscular patients is related more to the mechanical properties of the respiratory system than to reduction in lung volumes (). The forced oscillometry technique (FOT) can provide information about the resistance and reactance of the respiratory system. Aims and research questions: to investigate the relationship between dyspnoea, lung volume and oscillometric measurements of the respiratory system in LOPD patients. <bold>Methods:</bold> Six patients were examined. Forced vital capacity, as % of predicted value, was measured in the upright (FVC% u) and supine positions (FVC% s), and the difference between FVC% u and FVC% s was calculated (postural drop). The low-frequency oscillometry indices z-score R5rs, R5−19, X5rs, the area of reactance (AX) and the resonance frequency (fres) were determined. The Multidimensional Dyspnoea Profile (MDP) was used to assess dyspnoea. It ranges from 0 to 10, with higher scores indicating greater severity. <bold>Results:</bold> Mean values were as follows: Age 53.1±14.9 yrs, FVC% u 61.0±23.2, FVC% s 49.2±18.1 and PD 30.7±9.1 Mean MDP was 6.2 ±6.0. MDP did not correlate with either FVC u or FVC s, PD However, it was correlated with Z-score X5rs (−0.94 p=0.004), R5-19, fres and AX (0.94 p=0.004). <bold>Conclusions:</bold> Reactance at 5 Hz (X5) provides information about the elastic and inertial properties of the lungs while R5-19 is thought to estimate ventilation heterogeneicity. Our results support a link between dyspnoea and thoracic elasticity in LOPD patient. Larger studies are needed to validate our results.