Respirometer

A respirometer is a device used to measure the rate of respiration of a living organism by measuring its rate of exchange of oxygen and/or carbon dioxide. They allow investigation into how factors such as age, chemicals or the effect of light affect the rate of respiration. Respirometers are designed to measure respiration either on the level of a whole animal (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 pellets or cotton wads soaked with potassium hydroxide. 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), 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, Qubit Systems, or Challenge Technology; for mitochondrial respirometers Oroboros Instruments, Hansatech Instruments, or YSI.

Respiratory physiology

Respiration	breath inhalation exhalation respiratory rate respirometer pulmonary surfactant compliance elastic recoil hysteresivity airway resistance bronchial hyperresponsiveness constriction dilatation mechanical ventilation

Control	pons pneumotaxic center apneustic center medulla dorsal respiratory group ventral respiratory group chemoreceptors central peripheral pulmonary stretch receptors Hering–Breuer reflex

Lung volumes	VC FRC Vt dead space CC PEF calculations respiratory minute volume FEV1/FVC ratio Lung function tests spirometry body plethysmography peak flow meter nitrogen washout

Circulation	pulmonary circulation hypoxic pulmonary vasoconstriction pulmonary shunt

Interactions	Perfusion (V) ventilation (Q) ventilation/perfusion scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–haemoglobin dissociation curve (Oxygen saturation 2,3-BPG Bohr effect Haldane effect) carbonic anhydrase (chloride shift) oxyhemoglobin respiratory quotient arterial blood gas diffusion capacity (DLCO)

Insufficiency	high altitude oxygen toxicity hypoxia

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Respirometer

See also