Exercise testing, limitation and training in patients with cystic fibrosis. A personalized approach

Abstract

Exercise testing and training are cornerstones in regular CF care. However, no consensus exists in literature about which exercise test protocol should be used for individual patients. Furthermore, divergence exists in insights about both the dominant exercise limiting mechanisms and the possibilities to aim and institute exercise training strategies, based on these individual limitations. Therefore, this thesis intends to expand current knowledge in [1] alternative exercise test procedures in CF; [2] exercise limiting mechanisms in CF; and [3] exercise training of the inspiratory and skeletal muscles. In the first part of this research report we describe two different methodologies of exercise testing that were developed in patients with CF and were analyzed for their usefulness. Chapter 2 described the verification of VO2peak obtained during traditional cardiopulmonary exercise testing (CPET) with a supramaximal exercise procedure. The development and the validity of an individualized exercise test protocol in children and adolescents with CF are described in Chapter 3. Subsequently, Chapter 4 presents an alternative method to estimate VO2peak developed and validated in adolescents with CF. The major findings of the first part of the thesis: · The VO2peak measured with traditional CPET seems to reflect the true VO2peak in adolescents with CF (Chapter 2), · W­peak can be reliably predicted with standard measured anthropometric variables (Chapter 3), · The predicted Wpeak can be reliably used as guideline to individualize workload increments during CPET (Chapter 3), · VO2peak can be reliably predicted from Wpeak obtained with a traditional CPET combined with gender in adolescents with CF without the necessity of direct gas analysis (Chapter 4). The second part of this thesis focuses on two previously described exercise limiting mechanisms in patients with CF. Chapter 5 presents a study of the possible role of static hyperinflation as an exercise limiting factor, while Chapter 6 describes a study of the possible role of a CF specific locomotor skeletal muscle dysfunction. The major findings of the second part of the thesis: •The presence of static hyperinflation alone does not strongly influence ventilatory limitations during (peak) exercise in adolescents with CF (Chapter 5), •The RV/TLC > 30% criterion for static hyperinflation is a slightly stronger predictor of Wpeak/kg and VO2peak/kg than the traditional FEV1%pred (Chapter 5), •Oxidative exercise metabolism and oxygenation kinetics in clinically stable adolescents with CF with mild lung function impairment and without systemic inflammation seem to be comparable to healthy controls (Chapter 6). The third part of this thesis (Chapter 7) presents a study of the effects of two different types of exercise interventions, i.e. short-term, home-based inspiratory muscle training (IMT) and short-term, home-based peripheral muscle training programin patients with CF and the possible preconditioning effect of inspiratory muscle training prior to general exercise training. The major findings of this part of the thesis: •A six-week, home-based, non-supervised IMT program does not significantly decrease work of breathing in patients with mild lung function impairment compared to control patients, •Six weeks, non-supervised, peripheral muscle training was insufficient effective to increase exercise capacity in mild-moderate patients with CF.