Assessment of the correlation between the severity of interstitial lung disease and clinical parameters by cardiopulmonary ultrasound performance

Abstract

Objective To evaluate the application value of cardiopulmonary ultrasound(CPUS) in patients with interstitial lung diseases(ILD). Methods Ninety patients with clinically diagnosed interstitial lung diseases and 30 healthy subjects were included in this study. The conventional echocardiographic parameters and right ventricular free wall longitudinal strain (RVLS_FW) were measured in all patients and healthy subjects. The degree of pulmonary fibrosis or the disease severity of each ILD patient was scored using a semi-quantitative scoring method. Patients′ pulmonary function parameters and clinical outcome score (GAP score) were recorded. Fourteen patients belong to other types of ILD and 19 patients with incomplete clinical data were unable to perform GAP scoring, finally 57 patients′ clinical and ultrasonographic parameters were measured. On the basis of the pulmonary arterial systolic pressure (PASP) obtained by Doppler echocardiography, 90 patients were divided into two groups: ILD patients with pulmonary hypertension(ILDPH, PASP ≥36 mmHg, 1 mmHg=0.133 kPa) and ILD patients without PH (ILDNPH, PASP<36 mmHg). Comparsion between ILDPH, ILDNPH and healthy subjects were then evaluated. According to the GAP score, all cases were divided into three groups: low risk, moderate risk and high risk. Statistical analysis was performed to examine the relationship between CPUS parameters and clinical parameters. Results ①Compared with ILDNPH patients, ILDPH patients had significantly lower right ventricular function, wider basal right ventricular diameter (RVD), proximal right ventricular outflow diameter (DRVOT1) and right pulmonary artery diameter (DRPA). Compared with healthy subjects, ILDNPH patients had mildly lower right ventricular function and wider left pulmonary artery diameter (DLPA ) and right ventricular outflow tract dimensions at the distal or pulmonic valve (DRVOT2). ②A good correlation was found between lung ultrasound (LUS) scores and pulmonary function parameters, especially diffusion capacity for carbon monoxide of the lung(DLco)(r=-0.68, P<0.001). ③With the increased risk of patients, the right ventricular function was gradually decreased, DRVOT2, DRPA, DLPA were gradually widened, and the lung ultrasound score was gradually increased. A weak correlation was found between GAP scores with RVLS_FW, LUS scores, DRPA(r=0.44, 0.34, 0.31, P<0.05). Conclusions CPUS parameters are useful in the assessment of interstitial lung disease and could reflect the prognosis of ILD patients to some extent. Therefore, on the basis of GAP scores, addition of RVLS_FW and LUS score will be more helpful to evaluate the prognosis of ILD patients. Key words: Cardiopulmonary ultrasound; Lung diseases, interstitial; GAP score; Pulmonary function test