The relationship between acidosis and hypercapnia with Cor pulmonale in patients with chronic obstructive pulmonary disease

© 2017 The Authors; Tabriz University of Medical Sciences This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The relationship between acidosis and hypercapnia with Cor pulmonale in patients with chronic obstructive pulmonary disease

Citation: Hosseininia S, Aliasgharzadeh-Khiavi S, Zamani B, Habibzadeh A, Kheirjo S, Sadeghieh-Ahari S. The relationship between acidosis and hypercapnia with Cor pulmonale in patients with chronic obstructive pulmonary disease.J Anal Res Clin Med 2017; 5(4): 128-33.Doi: 10.15171/jarcm.2017.025 ][3][4] COPD is considered as one of the main causes of morbidity and mortality worldwide and is characterized by progressive airway obstruction leading to reduced lung function and breathlessness. 3,5Hypoxic pulmonary vasoconstriction, hypercapnia, respiratory acidosis and pulmonary vascular remodeling in COPD can cause an increase in right ventricular (RV) afterload, which in turn, results in RV failure leading to cor pulmonale. 6,7The severity of cor pulmonale in COPD patients is dependent to hypoxia, hypercapnia and airway obstruction as it has been reported a prevalence of 40% in patients with forced expiratory volume in the first second (FEV1) < 1 l and 70% in patients with FEV1 < 0.6 l.
With controlling and treatment of the causes and risk factors of cor pulmonale, it is possible to prevent the disease progress and reduce the morbidity and mortality rate. 8ue to presumed role of acidosis and hypercapnia for cor pulmonale in COPD patients, in this study we aimed to evaluate the correlation between acidosis and hypercapnia with corpulmonale in patients with COPD.
In this cross-sectional study, 100 patients with COPD exacerbation, global initiative for obstructive lung disease (GOLD) stage II-IV, FEV1 predicted < 60% and chronic hypoxia [partial pressure of oxygen (PaO2) < 60 mmHg)] admitted to Imam Khomeini Hospital, Ardabil, Iran, between February 2016 and February 2017 were included.Patients with previous or current pulmonary thromboemboli, obstructive sleep apnea, interstitial lung disease, left heart disease or left ventricular dysfunction due to ischemic heart disease, cardiomyopathies, congenital heart diseases, valvular heart disease, or other cardiovascular disease, malignancy, metabolic conditions, malnutrition, muscular disease, systemic inflammatory diseases, or renal failure, collagen vascular disease and idiopathic pulmonary hypertension were excluded.The study protocol was reviewed and approved by the Ethics Committee of Ardabil University of Medical Sciences.All patients were provided with written informed consent prior to enrolment.
Study protocol: Detailed clinical history and physical examination were obtained in each patient.Demographic, laboratory, electrocardiogram (ECG), chest X-ray findings were recorded.Atrial blood gas (ABG) was taken to evaluate the respiratory acidosis and hypercapnia.ABG was determined at patients' arrival to the emergency department with a FiO2 of 21%.All patients underwent echocardiography.The severity of COPD was staged according to the GOLD guidelines. 9The modified Medical Research Council (mMRC) 10 scale and the COPD Assessment Test (CAT) were also recorded.CAT is an eight-item questionnaire designed to quantify the impact of COPD symptoms on the health status of patients, with higher values indicative of worse health status. 11he patients were put into two subgroups, COPD with and without cor pulmonale.Cor pulmonale was diagnosed based on an established clinical history of cor pulmonale or the current clinical evidence, chest radiography, ECG, and echocardiography.Findings regarding RV hypertrophy or dilation and RV dysfunction in echocardiography were required for the enrollment.
All patients underwent spirometry and FEV1, forced vital capacity (FVC) and FEV1/FVC ratio were recorded.
A cardiovascular ultrasound system (Vivid E9, General Electric, Horten, Norway) was used to perform echocardiography, using M mode and two-dimensional ultrasonography.RV thickness and size, right ventricular hypertrophy (RVH), tricuspid regurgitation (TR) were recorded.Continuous wave Doppler was used to detect TR and calculate the systolic pulmonary artery pressure (sPAP).Pulmonary artery hypertension (PAH) was considered if sPAP value was above 30 mmHg and divided into mild (30-50 mmHg), moderate (50-70 mmHg) and severe (< 70 mmHg). 12ll data were analyzed using SPSS software (version 17, SPSS Inc., Chicago, IL, USA).Results are expressed as mean ± standard deviation (SD) or percentage.To compare the parameters, Student's independent t-test, analysis of variance (ANOVA) and chi-square or Fisher's exact tests were used to compare data between groups of patients.Pearson correlation was used to define possible correlations between echocardiographic and ABG and Pulmonary function test (PFT) findings, as well as between CAT and MMRC scores.P of less than 0.050 was considered statistically significant.
One-hundred patients including 56 men and 44 women with mean age of 66.53 ± 10.63 were studied.Mean duration of the disease was 12.50 ± 5.44 years.Comorbidities were diabetes mellitus (3 cases), hypertension (51 cases) and smoking (93 cases).Eighty-five patients had hypercapnia and 86 had respiratory acidosis.Cor pulmonale was present in 42 patients based on echocardiography findings.
Mean CAT score was 15.44 ± 10.84 and mean MMRC was 3.00 ± 0.81.According to GOLD criteria, 23 had stage II, 52 had stage III and 25 had stage IV.There was significantly positive correlation between CAT score and MMRC (r = 0.673, P < 0.001).Mean CAT score in GOLD stage II, III and IV were 7.26 ± 1.76, 13.59 ± 1.18 and 26.80 ± 7.69, respectively.With the increase in the GOLD stage, CAT score and health status were worsened (P < 0.001).
Demographic and clinical findings among COPD patients with and without cor pulmonale are shown in table 1.We found no significant difference among these variables between groups.Although cor pulmonale patients had higher CAT score and MMRC and more cases with a higher stage of GOLD, the difference was not significant.
Table 2 demonstrates PFT, ABG and echocardiography findings between COPD patients with and without cor pulmonale.Cor pulmonale patients had significantly lower FEV1, higher TR and pulmonary hypertension.
In our study, 100 patients with COPD including 56 men with mean age of 66.53 years were studied.We found cor pulmonale in 42 cases.In previous studies, COPD has been more prevalent in men, older age, lower socioeconomic state and smokers. 13In COPD patients, hypoxemia, hypercapnia, inflammation and vascular changes due to airway dilatation and changes in RV pressure lead to RV dysfunction and right heart failure. 14Cor pulmonale is the main cardiac side effect of COPD 15 and is considered as the main cause of mortality and morbidity in COPD. 16e observed cor pulmonale in 42.0% of COPD patients.Similarly, Gupta et al. 17 reported cor pulmonale in 41.2%.The prevalence was 48.1% in the study of Ju et al. 18 In our study, cor pulmonale patients were mostly men with longer duration of the disease and higher body mass index (BMI).Similarly, in the study of Ju et al, 18 patients with and without cor pulmonale had similar age and sex with higher prevalence in men, lower BMI and lower O2 saturation with no difference between groups.
Cor pulmonale patients in our study had lower FVC and FEV1/FVC, but there was the only significant difference between groups in the lower FEV1.ABG findings were not different between groups.There was no difference between hypercapnic and normocapnic COPD patients in the prevalence of COPD.Ju et al. 18 observed that cor pulmonale patients had lower FEV1 and FEV1/FVC.Unlike our findings, Yang et al. 19 observed that cor pulmonale was significantly higher in hypercapnic as compared to normocapnic patients.Verbitskii et al. 20 reported insignificant hypoxemia in cor pulmonale, which progressed with decompensation of chronic cor pulmonale.
In our study, cor pulmonale patients had significantly higher TR and pulmonary hypertension with a higher incidence of moderate and severe types.Likewise, Ju et al. 18 reported higher sPAP and RV thickness in cor pulmonale patients.Gupta et al. 17 observed that in corpulmonale patients, pulmonary hypertension prevalence is higher and with an increase in the severity of PHTN, the cases with cor pulmonale increases.
We also found significant negative correlations between FEV1/FVC with size and thickness of RV and positive correlation between RV size with PaCO2 and HCO3.We found a significantly positive correlation between CAT score and MMRC in COPD patients.We also observed that with an increase in the GOLD stage, CAT score and health status were worsened.

Table 1 .
Demographic and clinical findings between chronic obstructive pulmonary disease (COPD) patients with and without cor pulmonale

Table 2 .
Pulmonary function test (PFT), arterial blood gas (ABG) and echocardiographic findings between chronic obstructive pulmonary disease (COPD) patients with and without cor pulmonale