A respirometer is a device used to measure the rate of

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

of a living organism by measuring its rate of exchange of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

and/or

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

. They allow investigation into how factors such as age, or chemicals affect the rate of respiration. Respirometers are designed to measure respiration either on the level of a whole animal or plant or on the cellular level. These fields are covered by whole animal and cellular (or mitochondrial) respirometry, respectively. A simple whole plant respirometer designed to measure oxygen uptake or CO₂ release consists of a sealed container with the living specimen together with a substance to absorb the carbon dioxide given off during respiration, such as

soda lime Soda lime is a mixture of NaOH and CaO chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent ...

pellets or

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...

wads soaked with

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

. The oxygen uptake is detected by manometry. Typically, a U-tube manometer is used, which directly shows the pressure difference between the container and the atmosphere. As an organism takes up O₂, it generates a proportionate quantity of CO₂ (see

respiratory quotient The respiratory quotient (RQ or respiratory coefficient) is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the b ...

), but all the CO₂ is absorbed by the soda lime. Therefore, all of the drop of pressure in the chamber can be attributed to the drop of O₂ partial pressure in the container. The rate of change gives a direct and reasonably accurate reading for the organism's rate of respiration. As changes in temperature or pressure can also affect the displacement of the manometric fluid, a second respirometer identical to the first except with a dead specimen (or something with the same mass as the specimen in place of the organism) is sometimes set up. Subtracting the displacement of the second respirometer from the first allows for control of these factors. The set up of modern respirometers is described in more detail under respirometry. A respirometer may also be called an oxygraph. Suppliers for whole animal respirometers are e.g. Sable Systems, Respirometer Systems and Applications, Qubit Systems, Eco-environment, Bio-technology, or Challenge Technology; for mitochondrial respirometers, Oroboros Instruments, Hansatech Instruments, or YSI.

References

{{Respiratory physiology Respiration Pulmonary function testing

See also

References