Pressure‐diameter behavior of airways measured from tantalum bronchograms in isolated mouse lungs

In a previous study, conscious mice in response to methacholine aerosol reached a limit in airway constriction that occurred near zero airway elastic recoil, based on an analysis using elastic and active properties of large dog airways (J. Appl. Physiol. 105: 933‐941, 2008). We wondered whether mice have airway elastic properties similar to dogs. Balb/c mice (n = 5, 23‐27 g) were anesthetized and tantalum dust (5 micron) was insufflated via a 22‐G catheter into the lungs using a 0.2 ml air injection to produce a well‐defined bronchogram. Postmortem, the chest was opened and the lungs were inflated to 25 cmH 2 O transpulmonary pressure (Ptp) then deflated in steps to 10, 5, 0, ‐5 and ‐10 cmH 2 O. Tantalum bronchograms were taken at each Ptp. Airway diameters (8‐10) located between 1 and 8 airway generations were measured from the bronchograms of each mouse. Airway diameter decreased from a maximum (Dmax) at 25 cmH 2 O Ptp to 87, 79, 60, 50 and 47 %Dmax at 10, 5, 0, ‐5 and ‐10 cmH 2 O Ptp, respectively. The pressure‐diameter (PD) behavior was similar for both large (Dmax of 0.75 ± 0.11 (SD) mm) and small (Dmax of 0.32 ± 0.026 mm) airways. The measured PD behavior of mice was similar to that reported for dog airways (J. Appl. Physiol. 44: 859‐868, 1978). Supported by NIH grant HL 36597.