Pulmonary hypertension and cardiac function in chronic obstructive pulmonary disease

Significance of serum lncRNA XIST in chronic obstructive pulmonary disease and its progression to pulmonary heart disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) has become one of the major death-related causes. Chronic pulmonary heart disease (CPHD) is an adverse complication of COPD causing poor prognosis of patients. This study evaluated the role of lncRNA XIST in COPD and CPHD aiming to identify a potential biomarker for the screening and prediction of COPD.

METHODS

The study enrolled 127 COPD patients, including 73 patients occurred CPHD with 76 healthy individuals as the control group. The expression of XIST was evaluated by PCR and compared between COPD patients with different severity, grades, and complications. The diagnostic and prognostic values of XIST in COPD and CPHD were assessed by ROC and Kaplan-Meier analyses.

RESULTS

Significant upregulation of XIST was observed in the serum of COPD patients relative to healthy individuals, which distinguished COPD patients and showed a correlation with the respiratory and pulmonary function of COPD patients. COPD patients with acute exacerbations and CPHD showed a higher expression level. Increasing serum XIST discriminated COPD patients combined CPHD and positively correlated with right ventricular hypertrophy and pulmonary hypertension. Higher serum XIST levels could indicate the adverse 3-year prognosis of COPD patients, especially for COPD patients combined with CPHD.

CONCLUSION

Upregulated XIST served as a biomarker for screening COPD and predicting adverse prognosis of COPD and COPD patients with CPHD.

Severe pulmonary hypertension in histiocytosis X

Diminished exercise capacity in advanced pulmonary histiocytosis X does not appear to be related to ventilatory limitation but may be related to pulmonary vascular dysfunction. Pulmonary hemodynamics and respiratory function were studied in 21 consecutive patients with advanced pulmonary histiocytosis X, and compared with parameters of patients with other severe chronic lung diseases (29 patients with chronic obstructive pulmonary disease and 14 patients with idiopathic pulmonary fibrosis). All patients with pulmonary histiocytosis X displayed severe pulmonary hypertension: mean pulmonary arterial pressure, 59 +/- 4 mm Hg; cardiac index, 2.6 +/- 0.8 L/min/m(2); and total vascular pulmonary resistance, 25 +/- 3 IU/m(2) (p < 0.05, as compared with patients with other chronic lung diseases). Pa(O(2)) was similar in the three groups, whereas FEV(1) was lower in patients with other chronic lung diseases (p < 0.05). In contrast to other chronic lung diseases, the degree of pulmonary hypertension was not related to variables of pulmonary function in pulmonary histiocytosis X. Histopathology was available for 12 patients with pulmonary histiocytosis X and revealed proliferative vasculopathy involving muscular arteries and veins, with prominent venular involvement. Two consecutive lung samples (taken before and after the occurrence of pulmonary hypertension) were available for six patients with pulmonary histiocytosis X, and showed that pulmonary vasculopathy worsened, whereas parenchymal and bronchiolar lesions remained relatively unchanged. These results indicate that pulmonary hypertension in pulmonary histiocytosis X might be related to an intrinsic pulmonary vascular disease, in which the pulmonary circulation is involved independent of small airway and lung parenchyma injury.

Contractility of papillary muscle from rats exposed to 28 days of hypoxia, hypercapnia, and hypoxia with hypercapnia

The effects of chronic respiratory failure (hypoxia and hypercapnia) on the contractile properties of cardiac muscle are not established. A study was performed of the isometric contractile properties of isolated papillary muscle removed from rats exposed in a normobaric environmental chamber to 28 days of hypoxia (fractional inspired oxygen (FIO2) 10%, fractional inspired carbon dioxide (FICO2) less than 1%), hypercapnia (FIO2 21%, FICO2 5%), and hypoxia with hypercapnia (FIO2 10%, FICO2 5%). Rats exposed to both hypoxia and hypoxia with hypercapnia developed selective right ventricular hypertrophy. Exposure to hypercapnia alone did not alter right ventricular weight. No change in right ventricular papillary muscle contractility per unit muscle mass was observed as measured by maximum active tension, maximum rate of rise or fall of tension, or time to peak tension. Rat cardiac muscle adapts successfully to the altered acid-base environment and increased work load associated with prolonged exposure to hypoxia and mild hypercapnia.

Exercise performance in chronic obstructive pulmonary diseases

Patients with chronic obstructive pulmonary diseases demonstrate exercise limitation as a consequence of both an increased ventilatory requirement and a decreased ventilatory capacity. The increased ventilatory requirement arises from the elevated wasted ventilation fraction of each breath (VD/VT) and hypoxemia secondary to ventilation-perfusion mismatching, both of which stimulate minute ventilation of increase. The reduced ventilatory capacity is primarily the result of airflow obstruction, which causes an increased work of breathing. Respiratory muscle fatigue may also play a role in reducing ventilatory capacity. The differentiation of heart failure from chronic obstructive pulmonary diseases as a cause of dyspnea can be accomplished using a variety of noninvasive and invasive techniques during exercise, including measurements of minute ventilation, the expiratory airflow pattern, ventilatory reserve (VEmax/MVV), ventilatory efficiency (VD/VT), arterial blood gases, the anaerobic threshold, heart rate, cardiac output, pulmonary hemodynamics and ventricular ejection fraction. Exercise training of patients with chronic obstructive pulmonary diseases improves exercise intolerance but appears to have little effect on pulmonary function tests, arterial blood gases and pulmonary hemodynamics. Supplemental oxygen during exercise training may be a useful adjunct for improving exercise tolerance in patients with chronic obstructive pulmonary diseases.