Respiratory muscle dysfunction in schistosomal cor pulmonale: physiological histopathological and immunohistochemical studies

ABSTRACT

The study was conducted on 18 patients with schistosomal cor pulmonale with mean pulmonary artery pressure of 52.6 +/- 21.2 mm Hg, pulmonary vascular resistance of 8.1 +/- 4.7 unit and cardiac index of 3.03 +/- 0.37 L/min/m2. This work aimed to evaluate respiratory and diaphragmatic muscle strength and its impact on breathing pattern alteration. Histopathological and immunohistochemical studies were also performed on ten patients with evident reduced respiratory muscle strength to assess the structural changes and to identify the possible etiological mechanism for respiratory muscle dysfunction. Schistosomal cor pulmonale patients demonstrated reduction in respiratory muscle strength with mean values of 68.6 +/- 9.1% pred and 70.1 +/- 10.2% pred for maximal inspiratory and expiratory pressures respectively. On the other hand, transdiaphragmatic pressure during both normal and maximal effort showed mean values within the normal range [34.7 +/- 6.2 and 181.2 +/- 43.7cm H2O respectively]. Yet; diaphragmatic endurance index in the term of tension time index was found to be [0.09 +/- 0.05] reflecting reduction in diaphragmatic endurance. Breathing pattern demonstrated significant [P<0.01] increment in minute ventilation [VE 13.5 +/- 1.6 L/min] respiratory frequency [F 25.2 +/- 2.7] and mean inspiratory flow [V[t] /T[i]; 570.5 +/- 95.8]; whereas; inspiratory duty cycle was significantly [P<0.01] reduced [T[i]T[tot] 0.4 +/- 0.03] in comparison to control. PE[max] and PI[max] showed significant [P<0.05] negative correlation with V[T] /T[i] [r=-0.69,r =-0.88] and significant [P<0.05] positive correlation with T[i]T[tot] [r = 0.78 and r = 6.85] suggesting that respiratory muscle dysfunction does contribute to breathing pattern alterations. Histopathological study revealed myopathic changes in the form of increased variation in fiber diameter, degenerative changes with increased eosinophilic staining in 6 cases, fiber splitting and fragmentation in 7 cases and endomysial fatty changes in 5 patients Immunohistochemical study using anti-IgG and IgM antibodies revealed positive cytoplasmic staining for IgG in all cases and for IgM in 6 cases while none of the control showed positive stiaining. These previously unreported data document that patients with schistosomal cor pulmonale suffer from respiratory muscle affection at both physiological and histopathological levels. Immunohistochemical findings suggest immunopathogenetic mechanism for their deranged function. Greater attention should be paid for respiratory muscle while evaluating the respiratory functional state of patients with schistosomal cor pulmonale