Specific features of pulmonary mechanics and gas exchange in patients with histiocytosis X (HX)

Aim: To assess the changes of pulmonary mechanics and gas exchange parameters, which are typical for histiocytosis X. Materials and methods: 67 patients with HX have been examined, including 48 men (mean age 29.1 ±1.4 yrs) and 19 women (mean age 27.1±2.6 yrs). Spirometry, bodyplethysmography, compliance measurement, diffusion capacity (DLCO) and blood gases were carried out for all patients. Results: For either men or women the mean values of the lung mechanics parameters didn9t overstep the bounds of normal value, except for DLCO. Excluding 39 patients with normal value of indices, two groups of patients were identified. The first group of 20 patients shown signs of airflow limitation: decrease of the forced exhalation FEV1 (59.7±5.5 %Pred), MEF25-75 (39.7±8.9 %Pred) and reorganization normal TLC (98.8±4.5 %Pred) by obstructive type (RV/TLC – 168.0±11.2 %Pred). The second group contained 8 patients with restrictive respiratory pattern: reduction of TLC (70.4 ±2.5 %Pred) and VC (71.9±4.0 %Pred) without airflow limitation. Increase of pulmonary tissue retraction index (0.62±0.10 and 0.92±0.10 kPa/l) in both groups was an interesting find. DLCO has reduced in both groups (51.4±4.2 and 56.8±6.2 %Pred), but the DLCO/VA (61.0±8.2 and 70.7±5.0 %Pred) has been reduced in a greater degree in patients of the first group. Conclusions: DLCO decrease is characteristic for HX patients. Changes of lung mechanics parameters are observed much rarer. When it is the case, the obstructive pattern dominates restrictive one. In contrast to COPD, the obstructive pattern in HX is combined with increase of pulmonary tissue elasticity.