Respirometri

Respirometry is a set of techniques used to quantify gas exchange by living organisms, typically measuring oxygen consumption and carbon dioxide production to infer metabolic rate. It can be applied at organismal, tissue, or cellular levels and is widely used in physiology, ecology, and environmental science.

Main approaches include open-flow (flow-through) respirometry, where a known flow of air passes through a chamber and gas concentrations are measured, and closed-circuit (closed) respirometry, in which the chamber is sealed and the changes in O2 and CO2 are tracked over time. There are also static or semi-closed methods and microrespirometry for single cells, small invertebrates, or tissues. Each method has specific advantages for sensitivity, control, and time resolution.

Common metrics are VO2 (volume of oxygen consumed) and VCO2 (volume of carbon dioxide produced), often reported as rates. The respiratory exchange ratio (RER) or respiratory quotient (RQ) is VCO2/VO2. In animals and humans, metabolic rate is described as basal, resting, or standard metabolic rate, and values are frequently normalized to body mass and, when appropriate, temperature.

Instrumentation typically includes chambers, O2 sensors (such as Clark electrodes or optical sensors), CO2 sensors (often infrared), and flow meters, with environmental controls for temperature and humidity. Calibration with known gas mixtures and empty-chamber tests are essential to accuracy, along with corrections for water vapor and ambient pressure.

Applications span physiology, animal ecology, plant respiration studies, and clinical/metabolic assessments, while limitations include stress effects on subjects, chamber artifacts, and the need for careful species-specific calibration and normalization.