evaluation the effect of airway filters on etco2 during inferior abdominal surgery in infants and changes of vital capacity and respiratory rate needs for preventing of increasing etco2

background: the aim of this study was to prevent of increasing end tidal co2(et co 2) with changing of vital capacity and respiratory rate, when using of birthing filter in infants. materials and method: in a randomized clinical trial study, ninety four infant' patients were studied in three groups . basic values, such as: peak inspiratory pressure, tidal volume, minute ventilation, respiratory rate and partial pressure of et(pet co 2 )level had been evaluated after intubation, 10 minute after intubation and 10 minutes after filter insertion .in first group patients only observed for changing in etco2 level. in the second and the third groups, respiratory rates and tidal volume had been increased retrospectively, until that et co 2 ? 35mmhg was received. we used anova, chi x2 and, descriptive test for data analysis. p<0.05 was considered significant. results: tidal volume 10 minutes after filter insertion was statistically higher in group 3 (145.0±26.3 ml) versus 129.3±38.9 ml in group1 and 118.7±20.8 ml in group 2 (p=0.02). also, respiratory rate at this time was statistically higher in group 2(25.82±0.43) versus group 1 and 3 (21.05±0.20 ml and 21.02±0.60 ml respectively) (p=0.001). minute volume and pet co 2 level were statistically significant between group1 and the other two groups after filter insertion (p=0.01 and p=0.001 respectively). conclusion: with changing the vital capacity and respiratory rate we can control pet co 2 level ? 35mmhg during using of birthing filters in infants.  we recommend this instrument during anesthesia of infants.