The problems of functional diagnosis and ergospirometry in patients with COPD

Abstract

Available now methods allowing to determine functional diagnosis of CO PD do not take into consideration such important factors as patient’s physical work capacity and metabolic response to it. However, these factors may help to assess functional status of patients with more accurasy and to reveal subtle mechanisms of limited physical work capacity. The impairments in all components of respiratory function (bronchial conductance, lung diffusing capacity, respiratory muscle function et al.) may not be evident during rest because of ventilatory reserves available to meet the physiologic demands of exercise.

The possibility of distinguishing different mechanisms of limited physical work capacity was demonstrated in our study included 186 patients with COPD. In spite of dependence of maximal exercise capacity on expiratory airway resistance it was shown that limited physical work capacity can not be explained only by the presense of bronchial obstruction, because mechanism of exercise limitation includes not only reduction of maximal ventilator capacity at increasing in airway resistance, but also an increasing in ventilation level nessesary for determined level of oxygen uptake because of fall in gas exchange efficacy. Diffusing mechanism of limited physical work capacity in patients with COPD during exercise was displayed by fall in arterial oxygen saturation. In patients with respiratory muscle fatigue the most specific features illustrated the peculiarity of ventilatory response to physical load were dinamic changes in respiratory pattern characterized by increase in respiratory rate, fall in tidal volume, flight level of dead space ventilation and slow recowering of respiratory stereotype.

The obtained findings have showed that assessment of methabolic response to physical load and evaluation of mechanisms of exercise limitation may be valuable components of functional diagnosis.