Makara M, Dennler M, Schnyder M, et al.
In dogs, a mean broncho-arterial ratio of 1.45 +/- 0.21 has been previously defined as normal. These values were obtained in dogs under general inhalational anesthesia using a single breath-hold technique. The purpose of the study was to determine whether ventilation technique and bronchial diameter have an effect on broncho-arterial ratios. Four healthy Beagle dogs were scanned twice, each time with positive-pressure inspiration and end expiration. For each ventilation technique, broncho-arterial ratios were grouped into those obtained from small or large bronchi using the median diameter of the bronchi as the cutoff value. Mean broncho-arterial ratios obtained using positive-pressure inspiration (1.24 +/- 0.23) were statistically greater than those obtained at end expiration (1.11 +/- 0.20) P = 0.005. There was a strong positive correlation between bronchial diameter and broncho-arterial ratios for both ventilation techniques (positive-pressure inspiration rs = .786, P < 0.0005 and end expiration rs = .709, P < 0.0005). Mean broncho-arterial ratio for the large bronchi obtained applying positive-pressure inspiration was 1.39 cm +/- 0.20 and during end expiration was 1.22 cm +/- 0.20. Mean broncho-arterial ratio for the small bronchi obtained during positive-pressure inspiration was 1.08 cm +/- 0.13 and during end expiration was 1.01 cm +/- 0.13. There was a statistically significant difference between these groups (F = 248.60, P = 0.005). Findings indicated that reference values obtained using positive-pressure inspiration or from the larger bronchi may not be applicable to dogs scanned during end expiration or to the smaller bronchi.