Impact of Hemodialysis on Dyspnea and Lung Function in End Stage Kidney Disease Patients

Background. Respiratory symptoms are usually underestimated in patients with chronic kidney disease undergoing maintenance hemodialysis. Therefore, we set out to investigate the prevalence of patients chronic dyspnea and the relationship of the symptom to lung function indices.Methods. Twenty-five clinically stable hemodialysis patients were included. The mMRC dyspnea scale was applied before and after hemodialysis. Spirometry, single breath nitrogen test, arterial blood gases, static maximum inspiratory (Pimax⁡) and expiratory (Pemax⁡) muscle pressures, and mouth occlusion pressure (P0.1) were also measured.Results. Despite normal spirometry, all patients (100%) reported mild to moderate degree of chronic dyspnea pre which was reduced after hemodialysis. The sole predictor of (Δ) mMRC was the (Δ)P0.1(r=0.71, P<0.001). ThePimax⁡was reduced before and correlated with the duration of hemodialysis (r=0.614, P<0.001), whilst after the session it was significantly increased (P<0.001). Finally (Δ) weight was correlated with the (Δ)Pimax⁡ %pred(r=0.533, P=0,006) and with the (Δ) CV(%pred)(r=0.65, P<0.001).Conclusion. We conclude that dyspnea is the major symptom among the CKD patients that improves after hemodialysis. The neuromechanical dissociation observed probably is one of the major pathophysiologic mechanisms of dyspnea.

Validity, prognostic value and optimal cutoff of respiratory muscle strength in patients with chronic heart failure changes with beta-blocker treatment

Background Training studies frequently use maximum inspiratory mouth occlusion pressure (PImax) as a therapeutic target and surrogate marker. For patients on β-blocker (BBL), prognostic data allowing this extrapolation do not exist. Furthermore, the effects of BBL, mainstay of modern chronic heart failure therapy, on respiratory muscle function remain controversial. Finally, no proper separate cutoff according to treatment exists. Design Prospective, observational inclusion of patients with stable systolic chronic heart failure and recording of 1 year and all-time mortality for endpoint analysis. Methods In 686 patients, 81% men, 494 patients on BBL, PImax was measured along with clinical evaluation. The median follow-up was 50 months (interquartile range: 26–75 months). Results Patients with or without BBL did not differ significantly for PImax, percentage of predicted PImax or other marker of disease severity. PImax was a significant (hazard ratio: 0.925; 95% confidence interval: 0.879–0.975; χ2: 8.62) marker of adverse outcome, independent of BBL-status or aetiology. Percentage of predicted PImax was not independent of PImax. The cutoff identified through receiver-operated characteristics for 1-year mortality was 4.14 kPa for patients on BBL and 7.29 kPa for patients not on BBL. When separated accordingly, 1-year mortality was 8.5 versus 21.4%, P = 0.02, for patients not on BBL and 4.3 versus 16.2%, P < 0.001, for patients on BBL. Conclusion This study fills the gap between trials targeting respiratory muscle on a functional basis and the resultant prognostic information with regard to BBL. BBL lowered the optimal PImax cutoff values for risk stratification without changing the measured values of PImax. This should be considered at inclusion and evaluation of trials and interpretation of exercise parameters.

Effect of inspiratory muscle strength training on inspiratory motor drive and RREP early peak components

This study investigated the effect of inspiratory muscle strength training (IMST) on inspiratory motor drive [mouth occlusion pressure at 0.1 s (P0.1)] and respiratory-related evoked potentials (RREP). It was hypothesized that, if IMST increased inspiratory muscle strength, inspiratory motor drive would decrease. If motor drive were related to the RREP, it was further hypothesized that an IMST-related decrease in drive would change RREP latency and/or amplitude. Twenty-three subjects received IMST at 75% of their maximal inspiratory pressure (Pi max) with the use of a pressure threshold valve. IMST consisted of four sets of six breaths daily for 4 wk. P0.1 and the RREP were recorded before and after IMST. Posttraining, Pi maxincreased significantly by 36.0 ± 2.7%. P0.1decreased significantly by 21.9 ± 5.2%. The increase in Pi max was significantly correlated to the decrease in P0.1. RREP peaks P1a, Nf, P1, and N1 were identified pre- and post-IMST, and there was no difference in either amplitude or latency for those peaks. These results demonstrate that high-intensity IMST significantly increased Pi max, decreased P0.1, but did not change the RREP.

Effect of expiratory resistive loading on the noninvasive tension-time index in COPD

Expiratory resistive loading (ERL) is used by chronic obstructive pulmonary disease (COPD) patients to improve respiratory function. We, therefore, used a noninvasive tension-time index of the inspiratory muscles (TTmus =P̄i/Pi max × Ti/Tt, where P̄i is mean inspiratory pressure estimated from the mouth occlusion pressure, Pi max is maximal inspiratory pressure, Ti is inspiratory time, and Tt is total respiratory cycle time) to better define the effect of ERL on COPD patients. To accomplish this, we measured airway pressures, mouth occlusion pressure, respiratory cycle flow rates, and functional residual capacity (FRC) in 14 COPD patients and 10 normal subjects with and without the application of ERL. TTmus was then calculated and found to drop in both COPD and normal subjects ( P < 0.05). The decline in TTmus in both groups resulted solely from a prolongation of expiratory time with ERL ( P < 0.001 for COPD, P < 0.05 for normal subjects). In contrast to the COPD patients, normal subjects had an elevation in P̄i and FRC, thus minimizing the decline in TTmus. In conclusion, ERL reduces the potential for inspiratory muscle fatigue in COPD by reducing Ti/Tt without affecting FRC andP̄i.