Background Shortness of breath is a common and complex symptom in patients with advanced kidney failure treated with hemodialysis. It may result from excess fluid accumulation, cardiac dysfunction, or impaired lung performance. We studied the interactions between hydration status, pulmonary function, and muscle strength. Methods This cohort study included 29 patients on maintenance hemodialysis. Each participant underwent lung function testing, diffusing capacity for carbon monoxide measurement, handgrip strength assessment, body composition analysis by bioimpedance, echocardiography, and laboratory testing. All examinations were performed within 1 h before and after the same hemodialysis session. Results Hemodialysis significantly reduced total and extracellular body water and increased total lung capacity (5.11 ± 1.18 vs. 5.34 ± 1.27; p = 0.005), forced expiratory volume in 1 s (2.44 ± 0.88 vs. 2.54 ± 0.9 L; p = 0.022), and diffusing capacity for carbon monoxide 14.48 (4.35) vs. 15.73 (4.78) mL/min/mmHg; p = 0.0014. Muscle strength decreased slightly after hemodialysis (25,31 ± 12,82 vs. 23,79 ± 12,07 kg; p = 0,008), but this change was not correlated with the improvements in lung function. An improvement in gas transfer was associated with an increase in heart rate. Increased left ventricular filling pressure was linked to reduced pre-dialysis lung volume. Conclusions In our study, single hemodialysis session led to rapid improvements in lung volume and gas exchange, mainly due to reduced body fluid, as well as associated hemodynamic changes, rather than changes in muscle strength. Therefore, this study further underscores the need of a careful fluid management not only for maintaining respiratory performance but also overall wellbeing in patients on hemodialysis. Further studies with larger cohorts and long-term follow-up are needed to confirm these findings.
Salajová et al. (Thu,) studied this question.