hrvatski

Vd/Vt test u detekciji plućne disfunkcije u sepsi

Dyspnea and tachypnea are the leading sings of pulmonary dysfunction in sepsis. With regards to present knowledge of pathophysiology and pahtogenesis of the pulmonary dysfunction, the real reasons for this phenomena are still not resarched enough. It is our assumption that one of the underlying causes is in the increased ventilation of the physiological dead space due to the mismatch of the pulmonary ventilation and perfusion. In sepsis, equal to changes in systemic, there are changes in pulmonary circulation, often with pulmonary hypotension and decreased pulmonary vascular resistance. To investigate this we used a simple test to measure the ventilation of the dead space using Vd/Vt test. In 16 patients having conventional criteria for sepsis and tachypnea >20/min we measured dead space ventilation using Bohr&#8217; s Principe. The patients with chronic pulmonary disease (asthma, COPD) were not taken into consideration. According to Bohr the ratio of the dead space ventilation to tidal volume (Vt) is a measurable variable denoted as Vd/Vt=(PaCO2-PECO2)/PaCO2. Normal values are 0.2-0.4. To measure it we used a direct method with certain technical innovations. The subjects breathed through oronasal mask and one-way valve. Expired air was collected in a 5-litre balloon in order to provide adequate mixture of dead space and alveolar air. The concentration of CO2 on the end of the balloon was measured with RGM &#8220; Ohmeda&#8221; capnograph (infrared technique) together with minute ventilation. PaCO2 was measured simultaneously from arterial blood using conventional method. In all subjects increased (>0.4) Vd/Vt index was found, mean 0.51&#61617; 0.04. Minute ventilation was also increased, MV>8L. We compared this results with arterial O2 partial pressure and found high degree of negative linear correlation for Vd/Vt index and PaO2 (r=0.72, p<0.01). We believe that our results indicate that dyspnea and tachypnea in sepsis are mostly a result of the increased physiological dead space ventilation and that this test is useful for early detection and objectification of the pulmonary dysfunction in sepsis.

fiziološki mrtvi prostor; plućna disfunkcija; sepsa

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