Submitted on February 8, 2008
Accepted on May 6, 2008
Assessing recruitment of lung diffusing capacity in exercising guinea pigs using a rebreathing technique
Cuneyt Yilmaz1, D. Merrill Dane1, and Connie C.W. Hsia2*
1 Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
2 Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
* To whom correspondence should be addressed. E-mail: connie.hsia{at}utsouthwestern.edu.
Non-invasive techniques for assessing cardiopulmonary function in small animals are limited. We previously developed a rebreathing technique for measuring lung volume, pulmonary blood flow, diffusing capacity for carbon monoxide (DLCO) and its components: membrane diffusing capacity (DMCO) and pulmonary capillary blood volume (Vc), and septal volume, in conscious non-sedated guinea pigs at rest. Now we have extended this technique to study guinea pigs during voluntary treadmill exercise using a sealed respiratory mask attached to a body vest and a test gas mixture containing 0.5% SF6 or Ne, 0.3% CO and 0.8% C2H2 in 40% or 98% O2. From rest to exercise, O2 uptake increased from 12.7 to 25.5 ml.[min.kg]-1 while pulmonary blood flow increased from 123 to 239 ml.kg-1. The measured DLCO, DMCO and Vc increased linearly with respect to pulmonary blood flow as expected from alveolar microvascular recruitment; body mass-specific relationships were consistent with that in healthy human subjects and dogs studied using a similar technique. Results show that a) cardiopulmonary interactions from rest to exercise can be measured non-invasively in guinea pigs, b) guinea pigs exhibit similar patterns of exercise response and alveolar microvascular recruitment as larger species, and c) the rebreathing technique is widely applicable to human (~70 kg), dog (20-30 kg) and guinea pig (1-1.5 kg). In theory, this technique can be extended to even smaller animals provided that species-specific technical hurdles can be overcome.
