THE RELATIONSHIP BETWEEN PHOSPHATE METABOLISM AND EXTERNAL RESPIRATION FUNCTION IN CHILDREN AND ADOLESCENTS WITH BRONCHIAL ASTHMA

Objective of the study: to study some indicators of renal function, phosphate homeostasis and their relationship with external respiration function parameters in children and adolescents with bronchial asthma (BA). Materials and methods of research: a pilot prospective non-randomized single-center comparative study of 31 children aged 12.0 [9.0; 14.0] years with atopic BA. All children underwent anthropometry, spirometry, blood biochemical parameters test and 24-hour urine collection. Results: glomerular filtration rate calculated by the classic Schwartz formula was below the median in 18 (58%) of 31 patients. Serum phosphate concentration was excessive (more than +1Z above the mean) in 71% (22/31) of patients. Positive relationships were found between the maximum expiratory flow rate at the 25% point of the flow–volume loop (MOC25), the average expiratory flow rate at the 25–75% portion of the flow–volume loop (COC25–75), and blood creatinine concentration (r=0.36, p=0.04 and r=0.34, p=0.05, respectively); a negative relationship between the ratio of forced expiratory volume in 1 s to forced vital capacity and urinary phosphate concentration (r=–0.38, p=0.03). A negative relationship was noted between MOC25, SOC25–75 and urinary phosphate concentration (r=–0.37, p=0.03 and r=–0.36, p=0.04, respectively) and phosphorus/creatinine ratio (r=–0.4, p=0.02 and r=–0.39, p=0.02, respectively). Age-dependent sex differences normalized phosphate excretion was positively correlated with MOC25 (r=0.36, p=0.04). Conclusion: we have found a negative relationship between the concentration of phosphates in urine and blood with indicators of bronchial patency, as well as a positive relationship between patency in the small bronchi and the concentration of blood creatinine. The development of phosphate metabolism disorders in patients with BA may be associated with prolonged spasm of bronchial smooth muscles with the development of hyperphosphatemia and compensatory hyperphosphaturia. Further study of glomerular and tubular function in children with BA is required for the purpose of early prevention of the development of chronic kidney disease in this cohort. © 2022, Pediatria Ltd. All rights reserved.