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Clinical significance of hilar thoracic index and width of right descending branch of pulmonary artery in chronic obstructive pulmonary disease.

BACKGROUND
Clinical recognition of pulmonary artery hypertension (PAH) is a major challenge in the management of COPD. Increased hilar-thoracic (HT) index and width of the descending branch of the right pulmonary artery (DRPA) measured on a plain PA chest radiograph have been shown to have a good correlation with pulmonary arterial pressures (PAP) measured by right-heart catheterization. Color Doppler echocardiography has evolved as a noninvasive method to estimate PAP. In the absence of information of the relationship between these radiological signs and PAP measured using this technique, we carried out the present study from an out patient unit of a tertiary care hospital.


METHODS
Spirometry, arterial blood gas analysis and color Doppler echocardiography to estimate systolic and mean PAP were carried out in fifty patients with COPD. HT index and width of the DRPA were measured on a plain PA chest radiograph.


RESULTS
The mean values and the proportions of patients with increased HT index (> 35%) and increased width of the DRPA (20 mm or more) increased with increasing severity of the disease. Both the indices had significant correlations with FEV1% predicted, arterial PO2, arterial PCO2 and the systolic pulmonary artery pressure, and, in the case of the HT index, also with the mean pulmonary arterial pressure. The two radiological indices were highly correlated with each other. Increased HT index and increased width of the DRPA had a 100% specificity and predictive value positive (PVP) in identifying patients with pulmonary hypertension. However, sensitivity and predictive value negative (PVN) were low.


CONCLUSION
It was concluded that the HT index and width of the DRPA are useful and clinically valid measurements in patients with COPD.