Tracheal occlusion decreases airway resistance but not lung tissue mechanics in fetal rabbits with diaphragmatic hernia

MECHANICS IN FETAL RABBITS WITH DIAPHRAGMATIC HERNIA JACQUES JANI, ANDREAS FLEMMER, FLORIAN BERGMANN, XENIA ROUBLIOVA, DENIS GALLOT, OLIVER MUENSTERER, LISBETH VERCRUYSSE, KERSTIN HAJEK, HOLGER TILL, JAN DEPREST, Catholic University of Leuven, Center for Surgical Technologies, Leuven, Belgium, Ludwig-Maximilians-University, Department of Neonatology, Munich, Germany, Dr. von Hauner Children’s Hospital, University of Munich, Department of Pediatric Surgery, Munich, Germany, Catholic University of Leuven, Laboratory of Experimental Gynecology, Leuven, Belgium OBJECTIVE: To document the effect of tracheal occlusion (TO) on ventilatory parameters in a rabbit surgical model for diaphragmatic hernia (DH) using the forced oscillation technique. STUDY DESIGN: In New Zealand white rabbits fetuses of 23 d (term = 31d) underwent either surgical creation of DH (n = 18) or sham thoracotomy (Sham; n = 6). Half of DH-fetuses were randomly chosen to undergo TO @ 28d (DHCTO; n = 8). Non-operated littermates served as controls (n = 15). After term delivery, pups were intubated and connected to a Flexivent ventilator for 1 h. Outcome measures were body weight, lung weight, lungbody-weight ratio (LBWR), dynamic lung mechanics (Resistance; Rrs and Compliance; Crs) and lung impedance. Airway resistance (Raw), elastance (HL), tissue damping (GL) and hysteresivity (GL/HL) were calculated from impedance data. Sections of ventilated lungs were stained with Sirius-red to determine collagen content. Statistics were done using ANOVA. RESULTS: LBWR was larger in DHCTO than DH (p!0.01) and Sham (p!0.05) but not than controls. Crs and Rrs were no different in DHCTO than DH and Sham fetuses, but lower (Crs) resp. no different (Rrs) than in controls. Raw was decreased in DHCTO compared to DH but not to Sham and controls. DHCTO had no effect on lung tissue mechanic parameters HL, GL and hysteresivity; those fetuses also had morphologically a lower lung collagen content than DH. CONCLUSION: TO increases LBWR and improves mechanical lung properties in fetal rabbits with DH. TO has an effect on airway resistance but not on lung tissue mechanics.