Automated open flow respirometry in continuous and long-term measurements: design and principles.
Sustaining high-quality respirometry measurements on animals for estimating metabolic rate and fuel use is challenging. I present a general discussion and selected methods for automated measurements spanning over >4 mo with little need for adjustments or maintenance. 1) Lack of compensation for respiratory volume change may cause 6% error in the results on a fasting animal. The Haldane transformation provides the simplest calculation method for both O(2) and CO(2) measurements. 2) Use of Nafion tube dryers configured as countercurrent moisture exchangers provides maintenance-free drying of gases, with typical outlet dew points at -25 to -38°C and no CO(2) adsorption. The accuracy is improved by low dead space, making it feasible to pass gases though the same dryer. 3) A software algorithm employing a triple interpolation technique allows corrections for automated calibrations of O(2) and CO(2) with both zero-reference and span gas. 4) Burning known amounts of 100% ethanol provides total system verification of both O(2) consumption and respiratory quotient. A calculation method to supply instant CO(2) calibration gas from an alcohol burn is presented. 5) Automatic flow switching triggered by low/high O(2) thresholds improves accuracy of measurements and safety for the animals experiencing large ranges of O(2) consumption; this is a special requirement for recording metabolism in small hibernating mammals.
Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA. otoien@alaska.edu
Øivind
Ø
Tøien
D000388:Air; D000465:Algorithms; D000818:Animals; D057205:Automation, Laboratory; D002138:Calibration; D002153:Calorimetry, Indirect / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D004734:Energy Metabolism; D004867:Equipment Design; D006605:Hibernation; D006813:Humidity; D008954:Models, Biological; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012119:Respiration; D012984:Software; D013997:Time Factors