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This chapter de-mystifies respirometry equations, showing how they can be derived using a simple mental trick: concentrating the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases, are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.

This chapter describes the evolution of respirometry from Leonardo da Vinci's musings onwards. The works of Boyle, the brilliant and prophetic Mayow, and the well-intentioned but misguided Priestley are described. The bizarre dead-end theory of phlogiston and its apparent validity to the scientists of the day are explained in historical context. The breakthroughs of Lavoisier and Paulze, who realized the central role of oxygen and pioneered the quantitative measurement of metabolism, end the conventional historical part of the chapter, which concludes with a brief description of the deep history of the molecules most important to respirometry.

By using modern gas analyzers and variations of constant volume techniques described in Chapter 2, simple and high-throughput measurement of the metabolic rates of organisms ranging in size from bacteria to large insects and even small vertebrates are easily implemented. It is even possible to measure water loss rate and carbon dioxide production using only an oxygen analyzer. The techniques can be deployed in the field as well as the laboratory. Both manual and automated, computerized implementations of constant volume techniques are covered in full step-by-step detail, and appropriate analytical protocols for oxygen, carbon dioxide, or both oxygen and carbon dioxide analysis systems are also described in detail.

Measuring oxygen consumption rates in aquatic media is the only practical method for determining the metabolic rates of cell cultures and aquatic organisms. This chapter describes the two principal variations of aquatic respirometry — closed and open system (or flow-through) respirometry — together with procedures for calibrating aquatic respirometry systems, acquiring data from them, and analyzing the resulting data. The chapter also describes the operation of the widely used Clark dissolved oxygen electrode, the characteristics of common electrode membrane materials, and necessary routine maintenance. There is coverage of common problems, and trouble-shooting guides are included.

This chapter describes various techniques for measuring metabolic rates of unrestrained organisms in the field. These include stable isotope techniques, which allow the accurate measurement of the carbon dioxide production of wild animals, over an interval ranging from a few hours to a few days. The main disadvantage in the method is that the measurement is integrative and the organism must be captured on at least two occasions. Alternative techniques for real-time measurement of metabolic rates utilizing flow-through respirometry in wild, unrestrained animals are described, including representative case studies measuring hovering metabolism in wild hummingbirds, the foraging energetics of ants in the wild, and the energetics of nest building in wasps.

This chapter describes the basic theory behind the most widely used method for measuring metabolic rates: flow-through or open-system respirometry. The advantages and disadvantages of the technique are summarized, and the two major types of flow-through respirometry systems are described. Recommendations are given on choosing an appropriate flow rate to compromise between speed of response and signal amplitude; on using mathematical techniques for compensating for first-order wash-out kinetics and avoiding mixing errors; the essential differences between oxygen and carbon dioxide analysis; choosing a data acquisition system; generating and measuring flow rates; compensating for water vapor; important tools; and checklists for deciding on system configuration for a given investigation.

This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push-mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.

This chapter describes the setup, the plumbing, and the equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull-mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.

This chapter describes the theory and practical applications of coulometric respirometry. Coulometric respirometry is probably the most accurate method for measuring oxygen consumption rates. It is ideal for small animals and has the dual advantages of high sensitivity and the fact that the oxygen in the organism’s environment is not depleted, allowing measurements to continue for long periods in many cases. The technique works by maintaining a constant pressure in a sealed system by electrolytically producing oxygen at the same rate at which an enclosed organism consumes it.

The physics of pressure, flow and the gas laws have been discussed in Chapter 7 in relation to the behaviour of gas and vapour. This section will focus on the physical principles of the measurement of gas pressure, volume and flow. Unlike a liquid, a gas is compressible and the relationship between pressure, volume and flow depends on the resistance to gas flow (or impedance if there is a frequency dependence between pressure and flow in alternating flow, see Chapter 4 for the electrical analogy of this) in conduits (bronchi, anaesthetic tubing); it also depends on the compliance of structures being filled and emptied (alveoli, reservoir bags, tubing or bellows). Normal breathing occurs by muscular expansion of the thorax, thus lowering the intrathoracic pressure, allowing air or anaesthetic gas to flow towards the alveoli down a pressure gradient from atmospheric pressure. When positive pressure ventilation occurs, gas is ‘pushed’ under pressure into the alveoli. Depending on the exact relationship between the ventilator and the lungs, different relationships exist between airway pressure (rather than alveolar pressure, which cannot easily be measured) and gas flow and volume. Gas pressure measurement devices were traditionally in the form of an aneroid barometer, a hollow metal bellows calibrated for pressure and temperature, which contracts when the external pressure on it increases, and expands when it decreases. The movement is linked to a pointer and indicator dial. It is often more convenient to make the device in the shape of part of a circular section, but the principle is the same. This is what the Bourdon gauge, which commonly measures pressure in gas cylinders, looks like. The detection of movement of the diaphragm of an aneroid barometer can take several forms. The movement can either be linked via a direct mechanical linkage to a pointer, or diaphragm movement can be linked to a capacitative or inductive element in an electrical circuit, such as a Wheatstone bridge. Airway pressure during spontaneous breathing or artificial ventilation is low. The preferred units of measurement are cm H2O and the range of values is between −20 and +20 cmH2O. The aneroid barometer to measure this will therefore be of light construction, using thin copper for the bellows material.

This chapter describes various techniques for measuring metabolic rates of unrestrained organisms in the field. These include stable isotope techniques, which allow the accurate measurement of the carbon dioxide production of wild animals over an interval ranging from a few hours to several days. The main disadvantage of the method is that the measurement is integrative and the organism must be captured on at least two occasions. Alternative techniques for real-time measurement of metabolic rates utilizing flow-through respirometry in wild, unrestrained animals are described, including representative case studies measuring hovering metabolism in wild hummingbirds, the foraging energetics of ants in the wild, and the energetics of nest building in wasps.

This chapter describes the basic theory behind the most widely used method for measuring metabolic rates: flow-through or open-system respirometry. The advantages and disadvantages of the technique are summarized and the two major types of flow-through respirometry systems are described. Recommendations are given on choosing an appropriate flow rate to compromise between speed of response and signal amplitude; on the nature and importance of the cage time-constant; on using mathematical techniques for response correction by compensating for first-order wash-out kinetics and avoiding mixing errors; the essential differences between oxygen and carbon dioxide analysis; choosing a data acquisition system; generating and measuring flow rates; removing or mathematically compensating for water vapor; important tools; and checklists for deciding on system configuration for a given investigation.

This chapter describes the evolution of respirometry from Leonardo da Vinci’s musings onwards. The works of Boyle, the brilliant and prophetic Mayow, and the well-intentioned but misguided Priestley are described. The bizarre dead-end theory of phlogiston and its apparent validity to the scientists of the day are explained in historical context. The breakthroughs of Lavoisier and Paulze, who realized the central role of oxygen and pioneered the quantitative measurement of metabolism, end the conventional historical part of the chapter, which concludes with a brief description of the deep history of the molecules most important to respirometry.

By using modern gas analyzers and variations of constant volume techniques described in Chapter 2, simple and high-throughput measurement of the metabolic rates of organisms ranging in size from bacteria to large insects and even small vertebrates are easily implemented. It is also possible to measure water loss rate and carbon dioxide production using only an oxygen analyzer. These respirometry techniques can be deployed in the field as well as the laboratory. Both manual and automated, computerized implementations of constant volume techniques for metabolic rate measurement are covered in full step-by-step detail, and appropriate analytical protocols for oxygen, carbon dioxide, or both oxygen and carbon dioxide analysis systems are also described in detail.

Measuring oxygen consumption rates in aquatic media is the only practical method for determining the metabolic rates of cell cultures and aquatic organisms. This chapter describes the three principal variations of aquatic respirometry—closed and open system (or flow-through) respirometry, and headspace respirometry—together with procedures for calibrating aquatic respirometry systems, acquiring data from them, and analyzing the resulting data. Appendix 2 describes the operation of the widely used Clark dissolved oxygen electrode, the characteristics of common electrode membrane materials, and necessary routine maintenance. Common problems are discussed and trouble-shooting guides are included.

This chapter demystifies respirometry equations, showing how they can be derived using a simple mental trick: focusing the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.

This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.

This chapter describes the setup, plumbing, and equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.

This chapter describes two approaches to human metabolic measurement: room calorimetry and dilution mode mask (or hood, or canopy) respirometry. For room calorimetry, where the EE of a subject is typically monitored for 24 h, strategies for arranging air flow systems and the convective air movement required for effective time constant compensation are described, together with evaluation of push, pull, and push–pull flow and pressure regulation, with an emphasis on demystifying the technology. Methods for correcting the huge time constant of such rooms are described. For human metabolic measurement using a mask, hood, or canopy, common methodologies are summarized, and the advantages of dilution mode measurement over spirometry are discussed.