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Changes in respiratory muscle strength and lung function are associated with increased mortality and morbidity in chronic kidney disease, especially in the dialysis population. However, respiratory system dysfunctions in this population have been underexplored. Therefore, the aim of this study is to assess diaphragmatic mobility and thickness and associate them with lung function and respiratory muscle strength in dialysis patients.
A prospective cross-sectional study to be conducted between March 2023 and March 2026, approved by the Ethics and Research Committee of Hospital de Clínicas de Porto Alegre (CAAE 29241320610015327).
Twenty-four patients were evaluated, with 66.7% being women, with a mean age of 52.7±14.77 years. The average duration of hemodialysis was 36.3±31.26 months. Regarding respiratory muscle strength, the mean Maximal Inspiratory Pressure was 70.66±28.55% of predicted, and the mean Maximal Expiratory Pressure was 82.88±31.19% of predicted. For lung function, the mean Forced Vital Capacity (FVC) was 75.93±16.69% of predicted, and the Forced Expiratory Volume in the first second (FEV1) was 70.94±18.09% of predicted. Regarding diaphragmatic mobility, the mean excursion of the right hemidiaphragm was 1.62±0.48cm at tidal volume and 4.22±1.40cm at vital capacity level. For the left hemidiaphragm, the mean excursion was 1.87±0.75cm at tidal volume and 3.80±1.37cm at vital capacity level. In the evaluation of right hemidiaphragm thickness, there was a mean of 0.46±0.17cm for inspiratory thickness and 0.37±0.15cm for expiratory thickness, corresponding to a mean thickening ratio of 1.28±0.13 and a mean thickness fraction of 28.90±13.71. For the left hemidiaphragm, there was a mean of 0.48±0.18cm for inspiratory thickness and 0.35±0.14cm for expiratory thickness, corresponding to a mean thickening ratio of 1.36±0.16 and a mean thickness fraction of 36.65±15.95. The mobility of the right hemidiaphragm at vital capacity level showed a moderate and positive correlation with FVC in liters (p=0.004; r=0.533), with FVC in % of predicted (p=0.038; r=0.401), and with FEV1 in % of predicted (p=0.017; r=0.457). As for the left hemidiaphragm, mobility at vital capacity level showed a weak and positive correlation with FVC in liters (p=0.041; r=0.397), and moderate and positive correlations with FVC in % of predicted (p=0.001; r=0.590) and FEV1 in % of predicted (p=0.033; r=0.411).
These preliminary data indicate a trend of respiratory muscle weakness, as well as alterations in lung function in the evaluated patients. Diaphragmatic mobility and thickness fraction show appropriate measurements, but the thickening ratio indicates a trend of bilateral muscle weakness, according to literature reference values. Thus, the presented data reinforce the need for evaluating diaphragmatic dysfunction in patients with chronic kidney disease undergoing hemodialysis.