Volumetric capnography as a tool to detect early peripheric lung obstruction in cystic fibrosis patients [Capnografia volumétrica como meio de detectar obstrução pulmonar periférica precoce em pacientes com fibrose cística]

Objective: to compare spirometry and volumetric capnography (vcap) to determine if the capnographic values add more information about early lung disease in cystic fibrosis (cf) patients. methods: this was a cross-sectional study involving cf patients: group i (42 patients,6-12 years of age); and group ii (22 patients,13-20 years of age). the corresponding control groups were comprised of 30 and 50 healthy subjects,respectively. forced vital capacity (fvc),forced expiratory volume in one second (fev1),and the fev1/fvc ratio was determined by spirometry. using vcap,we measured peripheral oxygen saturation (spo2),respiratory rate (rr),inspiratory time (it),expiratory time (et),and the phase iii slope normalized by expiratory volume (phase iii slope/ve). results: in comparison with control groups,all cf patients presented higher phase iii slope/ve values (p < 0.001) independent of the pulmonary disease stage. the phase iii slope/ve was significantly higher in the 24 patients who presented normal spirometry results (p = 0.018). the group ii patients showed lower fvc,fev1,fev 1/fvc (p < 0.05),and also lower spo2 values (p < 0.001) when compared with group i patients. in comparison with control group ii,the group ii patients presented higher rr (p < 0.001),and lower it and et values (p < 0.001). conclusions: compared to the controls,all studied cf patients showed an increase in phase iii slope/ve values. vcap identified the heterogeneity of the ventilation distribution in the peripheral airways of cf patients who presented normal spirometry. copyright © 2012 by sociedade brasileira de pediatria.