Elastic properties of pulmonary artery in chronic obstructive pulmonary disease

Materials and methods. Participants were 50 patients with COPD stages 1–3 without comorbidities (32 men and 18 women, average age was 49.8 ± 1.0 years). Control group included 30 healthy people (19 men and 11 women, aged 50.1 ± 1.2 years). PA elastic properties was researched by ultrasound method. Statistical analysis was performed by means of the Statistica® 6.0 for Windows (StatSoft Inc.) software using parametric and nonparametric methods.


Оригинальные исследования
Today chronic obstructive pulmonary disease (COPD) is one of the common diseases and observed in 9-10 % adult in many countries, including Ukraine [1].COPD characterized by progressive, complicated clinical course and is the fourth leading cause in mortality.The main pathogenic factors of adverse course in COPD are airflow limitation, and pulmonary vascular changes.Functional decline is often associated with vascular remodeling and reduction of the pulmonary vascular bed leading to pulmonary hypertension and pulmonary heart progression with heart failure [2,3].
In the last decade, the elastic properties of the pulmonary artery (PA) and their impact on the course of COPD attracted the attention of researchers.Obvious information about PA stiffness associated with the severity of COPD [4], obstructive respiratory disorders and pulmonary hypertension [5].It is proved, that the violation of elastic properties of PA adversely affects the structural and functional condition of pulmonary vessels and leads to right ventricular overload [6].Furthermore, Bhatt SP. et al. observed prognostic changes of PA pulsatility in COPD significantly associated with pulmonary hypertension and adversely clinical course [7].So, the study of PA elastic properties in COPD remains relevant for both scientific and practical medicine.

Aim of the study
To evaluate the elastic properties of the pulmonary artery and pathogenetic mechanisms of disorders in patients with COPD.
Data were analyzed using "Statistica" (v.6.0, StatSoft Inc, USA).Comparison of variables between groups was established using independent samples t-test or Mann-Whitney U test (for data with normal or abnormal distribution, respectively).Pearson correlation was used for variable pairs with linear distribution.Statistical significance among variables was considered a two-tailed p value of less than 0.05.

The results and discussion
Study data showed that PAP and PA elastic properties between subjects with COPD and control group were materially differing (Table 1).So, all PAP indexes were significantly higher in CORD (p < 0.05).Simultaneously, EM and IS-B were increased significantly to 65.7 ± 3.7 mm Hg and 2.91 ± 0.17 in group with COPD versus 31.6 ± 1.2 mm Hg and 2.05 ± 0.08 in control group, respectively (p < 0.05).Conversely, Puls, Comp and Dist were decreased significantly to 39.23 ± 1.6 %, 6.4 ± 0.4 mm 2 /mm Hg and 1.71 ± 0.10 %/mm Hg in CORD versus 51.4 ± 1.9 %, 11.1 ± 0.5 mm 2 /mm Hg and 3.30 ± 0.12 %/mm Hg in control group, respectively (p < 0.05).
Our received data coincide with previous studies [8] which had demonstrated that PA stiffness and distensibility were worsened in COPD patients and correlated with decreased functional capacity.It should be noted, that the most significant PA elastic properties changes we are observed in the later stages of COPD.In addition, the PA elastic properties were correlated well with the presence of pulmonary hypertension.Relationship between PA elastic properties and sPAP, pPAP suggests PA stiffness as a promising biomarker for early detection of pulmonary vascular disease, and, may be, to play a role in right ventricular failure in COPD.Similar relationships marked by Thenappan T. et al. [9] as early change in the disease process even when pulmonary artery pressure and pulmonary vascular resistance are normal.
Thus, present studies demonstrated violation of PA elastic properties in COPD with increased stiffness, thus reduce pulsatility, compliance and elasticity of vascular wall.Detected changes of PA elastic properties were associated with disease progression, airflow limitation and pulmonary hypertension, most significantly in COPD stage-3.More significant relationships between PA elastic properties violations and systolic, pulse pulmonary arterial pressure were founded.

Conclusion
1. Violation of pulmonary artery elastic properties in COPD characterized by increasing stiffness and thus reduce pulsatility, compliance and elasticity of vascular wall.
2. Changes of PA elastic properties in COPD is associated with disease progression, airflow limitation and pulmonary hypertension, most significantly in COPD stages-3.
3. Systolic and pulse pulmonary arterial pressure had most significant relationships with violations of PA elastic properties.Оригинальные исследования

Table 1 .
PAP and PA elastic properties in the examined groups (M ± m) *: likely differences between comparison group (p <0.05).

Table 2 .
PAP and PA elastic properties distributed by the severity of COPD

Table 3 .
Correlation between indexes of PA elastic properties, blood pressure and FEV 1 (Pearson r, P value) *: p < 0.05.