Impairment of renal reserve filtration capacity in stage II–III chronic obstructive pulmonary disease under conditions of syntropy with stage II essential hypertension

Abstract

The aim of the study: to examine the state of functional renal reserve in patients with stage II–III chronic obstructive pulmonary disease (COPD) and stage II essential hypertension (EH).

Materials and methods. 60 patients were examined and divided into 3 clinical groups: group 1 – 15 patients with stage II EH (mean age 52.87 ± 1.36 years; male / female ratio 73.33 % / 26.67 %); group 2 – 15 patients with stage III–III COPD (mean age 48.01 ± 2.75 years; male / female ratio 86.67 % / 13.33 %); group 3 – 30 patients with stage II–III COPD and comorbid stage II EH with arterial hypertension stage I–III (23 men and 7 women, mean age 57.49 ± 2.39 years), without evidence for another clinically significant concomitant pathology and who did not receive regular antihypertensive therapy. All the groups were comparable in sex distribution and demographic parameters. Data indicating the presence of clinically significant kidney disease in these individuals was not revealed by comprehensive clinical, laboratory and instrumental examination results.

Results. Functional renal reserve (FRR) in patients with COPD + EH was significantly lower by 3.79 times (p < 0.05) compared to that in otherwise healthy individuals, while the basal glomerular filtration rate (GFR) did not differ significantly between these groups. In EH monopathology, the FRR level was 2.11 times (p < 0.05) lower than that in the control group. In COPD comorbid with EH, almost 5/6 patients showed signs of renal dysfunction in the form of impaired renal reserve ability to proportionally increase GFR, indicating the progression of nephron hyperfiltration processes. According to the Pearson’s chi-squared test, adverse disorders of pulmonary respiratory function were significantly more common (decreased Tiffeneau index (χ² = 6.13, p = 0.013)) as well as cases of microalbuminuria combined with elevated renal interlobar artery resistance (RI ILRA >1.05 RU) (χ² = 13.64, p < 0.001) in COPD patients with EH in the lower quartile of the FRR index, indicating the possible parallelism in certain pathological processes and abnormal autoregulatory mechanisms of glomerular filtration in combination of COPD and EH.

Conclusions. In patients with comorbid stage II–III COPD and stage II EH, manifestations of intraglomerular hypertension and hyperfiltration progression are associated with more severe clinical symptoms and the degree of “pressure load” according to the results of 24-hour ambulatory blood pressure monitoring, as evidenced by the presence of statistically significant correlations between FRR values, on the one hand, and the COPD Assessment Test scores and daytime systolic blood pressure load index (r = +0.55 and -0.63, p < 0.05 for all cases), on the other, confirming important relationships between impaired intrarenal hemodynamic processes and some prognostic factors in COPD combined with EH.