TY - JOUR T1 - Contribution of lung ventilation and perfusion distributions to the phase III slope of exhaled CO2 during acute bronchoconstriction studied by synchrotron imaging in rabbit JF - European Respiratory Journal JO - Eur Respir J VL - 42 IS - Suppl 57 SP - P3433 AU - Sam Bayat AU - Mathieu Guilbart AU - Liisa Porra AU - Loïc Dégrugilliers AU - Satu Strengell AU - Pekka Suortti AU - Anssi Sovijärvi Y1 - 2013/09/01 UR - http://erj.ersjournals.com/content/42/Suppl_57/P3433.abstract N2 - We studied the relation between the phase III slope of the volumetric capnogram (S3v) and the regional distributions of ventilation and blood volume (as a surrogate of perfusion) in 5 anesthetized and ventilated rabbits (Wt=2.9±0.1 kg). We used K-edge subtraction synchrotron imaging to quantify the regional distribution of ventilation (V’), blood volume (VB), the area of ventilated regions (VAA), at baseline, after inhaled methacholine (Mch, 125 mg/ml×1 min), and after salbutamol inhalation (2 mg/ml×5 min). Capnograms were recorded during tidal breathing. S3v was automatically computed and averaged using custom software. Respiratory mechanics were measured using multiple linear regression.The heterogeneity of V' increased more than that of VB after Mch (Figure). We found a significant relation between S3v and V’/VB (R=-0.65, p=0,0004), whereas the relation was weaker with VAA (R=-0.51, p=0.009) and V' (R=-0.49, p=0.014), and insignificant with VB (R=0.26, p=0.211).View this table:CONCLUSIONS: Direct measurements of regional lung V' and VB distributions during bronchoconstriction suggest that S3v is primarily determined by the V'/VB ratio. ER -