Breathlessness in Patients with Chronic Airflow Limitation: Reducing Ventilatory Demand
Bronchodilator Therapy: As a first step, every effort should be made to reduce the resistive and elastic load on the inspiratory muscles by optimizing bronchodilation. In some instances, adjunct antiinflammatory medication may confer additional benefits. Relief of breathlessness can be achieved with various bronchodilators in the presence of only small improvements in FEVi, ie, <15 percent. In this setting, improvement may be more closely linked to reduced gas trapping with concomitant enhancement of inspiratory muscle function. In this regard, there is preliminary evidence that reduced exertional breathlessness following anticholinergic medication in CAL is a function of reduced lung hyperinflation and consequent reduction of motor output. Similarly, reduced breathlessness and improved exercise tolerance after oral theophyllines has been shown to be associated with reduction of thoracic gas volumes.
Inspiratory Muscle Training: Recently, considerable efforts have been expended toward improving the performance properties of the respiratory muscles in order to achieve relief of breathlessness by enhancing ventilatory capacity. Specific inspiratory muscle training (IMT) has been shown to increase the strength and endurance of inspiratory muscles and improve symptoms in individual patients with CAL with demonstrable muscle weakness. However, a recent meta-analysis of available controlled studies of IMT failed to show significant subjective or objective improvement in most patients. These negative resuits may be explained by the fact that, in CAL, respiratory muscles undergo adaptive structural and biochemical changes in response to intrinsic mechanical loading that results in relative preservation of muscle function, at least under resting conditions. buy antibiotics
Exercise Training: Manipulation of the components of the mass balance equation for ventilation, ie, VE=[0.86XVco2/PaC02ll-VD/VT] so as to reduce ventilatory demand for practical purposes is largely confined to reducing CO2 production (VCO2). Thus, exercise training at high intensities in motivated younger patients with moderate CAL has been shown to enhance aerobic capacity42 In these patients, post-training reductions in lactate levels and VCO2 resulted in reduced ventilation at a given external power output.
Category: Respiratory Symptoms
Tags: breathlessness, chronic airflow limitation, copd, dynamic compression, dynamic hyperinflation, exercise