Le alterazioni degli scambi gassosi polmonari nelle broncopneumopatie croniche ostruttive e loro modificazioni indotte dalla terapia

In order to assess the mechanisms of gas exchange disturbances(i.e. to what extent shunting and diffusion impairment contributeto hypoxemia) in chronic obstructive pulmonary disease (COPD)and respiratory failure, ventilation-perfusion relationshìps (V/Q)by the multiple inert gas elimination technique were obtained in 16patients with respiratory failure breakthrough. In 6 istances thestudy was repeated after long-term treatment with the aim to anaIyzeV/Q changes after therapy. Initially, patients showed severehypoxemia and hypercapnia and they presented signs of markedbronchoconstriction. A great dispersion of V and Q distributionwas present as indicated by the marked increase of the second momentof V and Q distributions. Interestingly, few patients presenteda unimodal distribution of both V and Q, whereas most pa-tients had bimodal distributions where the ventilation was distributedin a mode such that high V/Q areas were present between IOand lDOof V/Q ratio and biood fiow was displaced leftward or towardlower V/Q values. No correlations were found between Vand Q distribution and clinical types A or B of COPD. Significantrelationships were found between measured and calculated arterialP02 (r = 0.90, p < 0.001) and between measured P02 and thesum of the fractional perfusion to regions with V Q ratio less than0.1, suggesting that V/Q inequality and shunting, instead of the impairrnentof diffusion equilibration, can account for all the hypo-xemia. Finally, the reduced inhomogeneity of ventilation aftertreatment, expecially in the fraction located in high V Q regions ismostly related to some functional and reversible damages in