Analysis of respiratory mechanics by impulse oscillometry in non-sedated and diazepam-sedated swine

Analysis of respiratory mechanics using impulse oscillometry is applicable to sedated, or non-sedated (trained) pigs when they are fixed in a sling. I n this study, the influence of the following sources of variability on meas urement results was examined: (i) sedation with diazepam; (ii) body weight of animals (ranging in age: 40 to 102 days); and (iii) time of the measurem ent (circadian influences). The following parameters were examined: respira tory rate (RR), tidal volume (v(t)), spectral resistance, reactance and t), and proximal coherence, each at 5, 10, 15 and 20 Hz (R5,...R-20, X-5,...X- 20, Co-5...Co-20, respectively), distal respiratory resistance (R-dist), an d proximal airway resistance (R-prox). After sedation (using 1.5 mg diazepa m per kg body weight), RR and v(t) decreased significantly. There was a sig nificant improvement of co(5), co(10) and co(15). Increase in body weight w as strongly correlated to v(t), furthermore to spectral resistance paramete rs. Impulse oscillometry system (IOS) parameters showed only slight non-sig nificant alterations in dependency on the time of day. In consequence, diff erent sources of variability must be taken into account when performing IOS measurements in swine. (C) 2001 Harcourt Publishers Ltd.