As matter of fact, experimental evidence on the redistribution of ventilation away from the vascular occluded lung had been already obtained in the early 60s of the last century. Hence, it was inferred that this disorder was characterized, unlike parenchymal disease, by ventilation/perfusion mismatch in the affected lung zones and by an obvious increase of wasted ventilation, i.e., dead space. These findings show the potential for V(D)alv/V(T)alv to quantify the embolic burden of PE.The diagnostic strategy for pulmonary embolism, based on the mismatch of the ventilation/perfusion scan, was developed some 30 years ago on the following assumption: since the disorder involves the pulmonary vessels, it was surmised that in the embolized regions lung alveoli are unperfused or poorly perfused but well ventilated. The V(D)alv/V(T)alv correlates with the lung perfusion defect and the pulmonary artery pressures in subjects with PE. Regression of V(D)alv/V(T)alv vs pulmonary artery pressures yielded r2 = 0.59. Regression of V(D)alv/V(T)alv vs perfusion defect yielded r2 = 0.41. Regression analysis was performed to show correlation between V(D)alv/V(T)alv and defect on V/Q scan or systolic pulmonary arterial pressure (SPAP).įor subjects with PE, the mean perfusion defect on lung scan was 38 +/- 22% the mean V(D)alv = 208 +/- 115 mL, V(T)alv = 452 +/- 251 mL, and V(D)alv/V(T)alv = 43 +/- 18%. Percentage perfusion defect was determined from V/Q scans by a radiologist blinded to other data. Airway dead space (V(D)aw) was subtracted to yield the alveolar dead space the percentage of alveolar volume occupied by alveolar dead space per breath = V(D)alv/V(T)alv x 100%. The V(D)alv/V(T)alv was determined from volumetric capnography and arterial blood gas analysis, which permits measurement of the physiologic dead space, V(D)phys (mL) =. Pulmonary embolism was excluded by PAG in 20 subjects. Pulmonary embolism was diagnosed in 33 by high-probability ventilation/perfusion (V/Q) scan (n = 19) or by pulmonary arteriography (PAG, n = 14). To determine whether the alveolar dead space volume (V(D)alv), expressed as a percentage of the alveolar tidal volume (V(D)alv/V(T)alv), can predict the degree of vascular occlusion caused by pulmonary embolism (PE).įifty-three subjects with suspected PE were prospectively studied.
0 kommentar(er)
