Original Contribution
Prevalence and predictors associated with severe pulmonary hypertension in COPD

https://doi.org/10.1016/j.ajem.2017.08.014Get rights and content

Abstract

Background

Pulmonary hypertension (PH) is one of the most common complications of COPD (chronic obstructive pulmonary disease), but its severe form is uncommon. Various factors play an important role in the occurrence and severity of pulmonary hypertension in patients.

Methods

This cross-sectional study was performed on patients with COPD referred to an emergency department over a one-year period. The tests—including complete blood count (CBC) and arterial blood gas (ABG), pulmonary functional test (PFT) and echocardiography—were performed for all patients to measure mPAP (mean pulmonary artery pressure), ejection fraction (EF) and body mass index (BMI). The prevalence of severe pulmonary hypertension and its associated factors were investigated in these patients.

Results

A total of 1078 patients was included in the study, of whom 628 (58.3%) were male and 450 (41.7%) were female. The mean age of the patients undergoing the study was 70.1 ± 12.2. A total of 136 (13.7%) of them had mPAP (mm Hg)  40 mm Hg as severe pulmonary hypertension. Following multivariable analysis by using the backward conditional method, it was shown that seven variables had a significant correlation with severe PH.

Conclusions

The results showed that there is an independent correlation between hypoxia, hypopnea and compensatory metabolic alkalosis, polycythemia, left ventricular dysfunction, emaciation, and cachectic with severe pulmonary hypertension. The prevalence of severe PH in these patients was 13.7%.

Introduction

Chronic obstructive pulmonary disease (COPD) is an irreversible bronchial inflammation that involves the lung airways and parenchyma and causes mucociliary dysfunction. Pulmonary hypertension (PH) is a common complication of COPD, which occurs in the wake of the development and exacerbation of the disease in the patients. PH is defined by a resting mean pulmonary arterial pressure > 25 mm Hg, which is measured via right heart catheterization [1], [2], [3], [4]. The prevalence of PH in these patients is different and depends on the severity of the disease, but is usually mild to moderate, and worsens by exercise, sleep and exacerbation of the disease. Approximately 5–10% of patients have “disproportionate” PH, which is the severe form of the disease. In these patients, resting PH is above 40 mm Hg. Such patients—because of the right ventricular failure—have worse prognosis compared with those who have mild to moderate pulmonary hypertension [4], [5], [6], [7].

A method of choice for the diagnosis of PH is right-heart catheterization, but because its nature is aggressive, Transthoracic Doppler Echocardiography can be used as a noninvasive method to screen these patients. In this method, mean pulmonary artery pressure (mPAP)  40 mm Hg is considered severe PH [3], [5]. The most important factors that can contribute to the occurrence or exacerbation of PH include forced expiratory volume 1 (FEV1), ejection fraction (EF), and body mass index (BMI).

BMI is a measure of body fat and weight. It is calculated by dividing a person's weight in kilograms by the square of their height in meters. A correlation has been established between a high BMI and the increased risk of cardiovascular complications. It has been observed that lower levels of BMI can increase the risk of COPD complications and is inversely related to the survival of these patients, such that a lower BMI increases the risk of mortality caused by COPD [8], [9].

Ejection fraction (EF) is used to assess left ventricular function and is calculated using the biplane Simpson's technique. An EF < 50% is considered left ventricular dysfunction. Patients with COPD are at risk for left ventricular dysfunction; however, the results regarding the association of LV dysfunction in COPD patients has been the subject of much controversy. Nevertheless, the risk of mortality increases in patients with left ventricular dysfunction [10], [11], [12]. It seems that this left ventricular dysfunction is caused by right ventricular heart failure [11].

Lung function in patients with COPD is measured by FEV1 using Spirometry, which enables the assessment of the degree and severity of airway obstruction. A lower value of FEV1 is correlated with a severity of obstruction. In addition, there is a direct correlation between FEV1 levels with the prognosis of these patients [13], [14].

The aim of this study was to assess the prevalence of severe PH in COPD patients referred to the emergency department of Afzalipour hospital and to monitor the relationship between PH with other variables.

Section snippets

Study design

This cross-sectional study was performed at the internal medicine referral center of Kerman Afzalipour Hospital, located in the southeast of Iran, on patients with exacerbated COPD referred to the emergency department from June 21, 2014 through June 21, 2015. In the primary stage of the study, before starting the treatment process, vital signs were measured and complete blood count (CBC) and arterial blood gas (ABG) tests were performed on all the patients. After the patients were stabilized,

Basic characteristics

Of a total of 1477 patients diagnosed with exacerbated COPD referring to the hospital within one year, 399 of them were excluded from the study and 1078 of them included in the study, in which 628 (58.3%) were male and 450 (41.7%) were female. The mean age of the patients undergoing the study was 70.1 ± 12.2. The youngest patient was 39 and the oldest was 93 years old. A total of 136 (13.7%) of them had mPAP (mm Hg)  40 mm Hg as severe pulmonary hypertension. Also, 129 (12.5%) of them had ejection

Discussion

In this study, the prevalence and predictors associated with severe PH in patients with COPD were examined. According to the results, the prevalence of severe PH in these patients by noninvasive echocardiographic evaluations was 13.7%. Moreover, there was an independent correlation between severe PH, with variables such as hypoxia, hypopnea and compensatory metabolic alkalosis, polycythemia, left ventricular dysfunction, emaciation, and cachectic as well.

The prevalence of severe PH in COPD

Conclusion

The prevalence of severe pulmonary hypertension in this study was reported in 13.7% of patients. The independent factors associated with PH include hypoxia, hypopnea and compensatory metabolic alkalosis, polycythemia, left ventricular dysfunction, emaciation and cachectic in patients.

Conflict of interest

The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

Acknowledgment

This study was supported by the Clinical Research Center of Afzalipour Hospital [grant number 94.427], Kerman University of Medical Science, Kerman, Iran.

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