Direct and indirect calorimetry

The quantity of heat produced when a given portion of pure air is altered by the respiration of an animal is nearly equal to that which is produced when the same quantity of air is altered by the combustion of wax or charcoal. (Crawford, 1778) [2], These early words of Crawford together with Laplace s indirect observation of respiration rates of guinea-pigs in his ice calorimeter established the fundaments for the great success of indirect calorimetry. 

Indirect calorimetry was originally bound to the manometric or voluminetric determination of the respiratory metabolism of an animal, i.e. its oxygen consumption and carbon dioxide production rate. Nowadays, it includes a manifold of different metabolic approaches, as briefly mentioned in the Introduction. 

Battley [39] presented a critical survey about advantages and drawbacks of direct and indirect techniques for different types of calorimetry. Kleiber [33] stated that Indirect calorimetry measures the heat production of an animal direct calorimetry measures the heat loss. Heat gain and heat loss are equal only when heat capacity and body temperature remain constant. One may define indirect calorimetry as the determination of heat production rates by means of some methods other than direct calorimetry. But one has to bear in mind that with the exception of the determination of heat production by ergometry, all indirect methods of calorimetry depend ultimately on previously made direct calorimetric measurements of one kind or another that are used in the calculation of the heat produced. [39] 

If one has the choice to make direct or indirect calorimetric determinations one has to consider their strong and weak points. For analytical calorimetry, i.e. the proof if some process is proceeding and how fast, the direct approach is preferable, e.g. for temporal structures or periodicities in animal activity or for special developmental transitions like pupation and moulting of insects (section 5.3.). Although calorimeters are more expensive than most indirect techniques they are also advantageous for quantitative analysis of heat loss provided that the necessary corrections can be performed for the true heat dissipation. If one wants to know the reason(s) for an observed heat loss, indirect calorimetry may be the approach of choice. But in any case when both methods are at hand, it will be best to determine the possible heat loss in an indirect way and confirm it later with the direct one [39]. 

However, there are often situations in the life of animals (e g. strong locomotor activities, decrease of oxygen concentration in their environment) that force them to switch over partly (perhaps also temporarily) or completely to anaerobic metabolism without oxygen consumption. Under such conditions direct calorimetry -which monitores all enthalpy changes in the animal and not only the aerobic ones 

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Waversveld, J., Addink, A.D.F. and van den Thillart, G. (1989). The anaerobic energy metabolism of goldfish determined by simultaneous direct and indirect calorimetry during anoxia and hypoxia. Journal of Comparative Physiology 159B, 263-268. 

Coward, W. A., Prentice, A. M., Murgatroyd, P. R., Davies, H. L., Cole, T. J., Sawyer, M., Goldberg, G. R., Halliday, D., and Macnamara, J. P. (1984). Measurement of COj and water production rates in man using H, -labelled H2O comparison between calorimeter and isotope values. In Human Energy Metabolism Physical Activity and Energy Expenditure Measurements in Epidemiological Researdi Based Upon Direct and Indirect Calorimetry (A. J. H. van Es, ed.), pp. 126-128. EURO-NUT, The Netherlands. 

Lamprecht, I.H.D. (1985) Direct and indirect calorimetry of medium sized animals. Thermochim. Acta, 94,113—122. 

Early calorimetric investigations were performed on pupae of the wax moth Galleria mellonella by means of a differential adiabatic setup [92]. Galleria represents an important pest for weak honeybee colonies where it feeds on wax, honey, pollen and other organic material. Individual pupae were kept in small Dewar flasks of 5 cm for measurements of 10 to 60 min, which were repeated in regular intervals through the whole pupal metamorphosis of about 7 days. The calorimetric experiments alternated with manometry (indirect calorimetry) to evaluate the RQ and to find hints about the type of metabolism. Heat dissipation was monitored by electrical heating of the reference flask to keep the temperature difference between both Dewars close to zero. In this way composite curves for male and female moths and both direct and indirect calorimetry were established. 

The aquatic oligochaete Lumbriculus variegatus is known to survive long periods of anoxia so that it represents a suited object for various calorimetric investigations. Groups of 10 individuals of this species with 1 to 2 mg dry weight were placed in a perfusion chamber of a flow calorimeter connected to a twin-flow respirometer (section 3.3.1.) for simultaneous direct and indirect calorimetry [170]. They were exposed to normoxic and anoxic conditions and showed a drastic reduction of heat dissipation under anoxia down to 15 % of the aerobic rates. Switching back to aerobic conditions, heat dissipation increased immediately. 

Simultaneous direct and indirect calorimetry was applied to monitor decreased oxygen concentrations in combination with hydrogen sulphide contaminations of freshwater on two annelides, Limnodrilus hoffineisteri and Tubifex tubifex [175,176], Such combined adverse conditions are typical for polluted lakes and rivers with high organic load. Complete anoxia reduced the normoxic heat production rates (0.83 and 0.56 mW/g for L hoffineisteri and T. tubifex, resp.) to less than one fourth. Presence of 100 pmol/l H2S depressed the heat dissipation in L hoffineisteri at each oxygen level, mainly due to the strict inhibition of aerobic respiration. In contrast, heat dissipation increased in T. tubifex (up to 170 %) because of its detoxification system which protects respiration. 

M. Harak. Heat production and respiration during the normal and defective metamorphosis of holometabolous insects by direct and indirect calorimetry, PhD Thesis, Tartu, 1997. 

J. van Waversveld. The energy metabolism of goldfish at different oxygen levels determined by simultaneous direct and indirect calorimetry. PhD-Thesis, University of Leiden, 1988. 

Table 2 Advantages, disadvantages and common features of direct and indirect calorimetry...

Whole body calorimetry is an important tool for physicians, physiologists and nutritionists. The application of calorimetry started about 200 years ago. Its theoretical base was established in the last 100 years. The technique of calorimeters and calorimetric methods have been largely improved until nowadays. Modern whole body calorimeters are very accurate and fast responding instruments. They reach recovery rates of about 100 3 % and a delay of measurement of as short as 3 min. Two calorimetric techniques are established, direct and indirect calorimetry. The former is the measurement of the heat loss of a subject the latter determines the heat production by metabolic processes. This gives a deeper insight into the metabolic status of the subjects. So indirect calorimetry is nowadays more frequently used than direct one. 

BMR is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (expressed in kcal/day). BMR decreases with age and with the loss of lean body mass. Increasing muscle mass increases BMR. Illness, previously consumed food and beverages, environmental temperature and stress levels can affect overall energy expenditure as well as the BMR. BMR is accurately determined by gas analysis (direct or indirect calorimetry) an estimation can be found using the equation ... 

In comparison to males BMR is generally lower in females and higher in children. BMR is measured 12—14 hours after a meal, by direct or indirect calorimetry. Feeding increases BMR because of the necessary energy expenditure that occurs during the assimilation of nutrients into the body (also known as specific dynamic action). BMR is also very closely related to body surface area, since this is where the majority of heat exchange takes place. 

However, bomb calorimetry is more simple and direct. It might be expected that the simpler method would be theoretically the more accurate. Practically, the direct and indirect methods of calorimetry appear to be similar in this respect if appropriate data for the latter are available." [146]... 

Direct calorimetry of fish is scarce, and indirect calorimetry started even later. Davies [144] determined heat production rates for goldfish. Smith and coworkers [145] investigated those of 4 salmonids at different temperatures. Group effects (see section 5.1.1. and 5.4.2.) could also be observed. Van Waversfeld and colleagues presented an approximate rate of 700 J/h/mw (0.20 W/mw) for fish at 20 °C where mw indicates the metabolic weight, i.e. the body mass m in kg to a broken power of 0.85 (mw = [146]. 

Calorimetry is still in use today, but the emphasis in biological and medical research went from direct to indirect calorimetry in the last decades. This was mainly caused by two reasons. The first one is a huge improvement in gas analysis instrumentation compared with that of the instrumentation of direct calorimetry. The second reason is, that indirect calorimetry provides not only with measures of energy expenditure, but the substrate oxidation rates too. This is in biology related fields probably of at least the same significance than energy expenditure alone. 

It is possible, of course, to use direct calorimetry, often in combination with the indirect approach (OUR) to investigate the properties of muscle under different physiological conditions and in the diseased state. Chinet s group [70] found that the slow- and fast-twitch skeletal muscle fibres from the murine model of Duchenne muscular dystrophy had a reduced sarcoplasmic energy metabolism as measured by the combined direct and indirect calorimeter [69]. The possibility that this could be due to diminished glucose availability was then examined [71] but was dismissed in favour of decreased oxidative utilisation of glucose and free fatty acids, conceivably due to defective mitochondria. 

This temperature rise can be detected directly (laser calorimetry and optical calorimetry), or indirectly by measuring the change in either the refractive index (thermal lensing, beam deflection or refraction and thermal grating) or the volume (photo- or optoacoustic methods). This review will focus primarily on photoacoustic methods because they have been the most widely used to obtain thermodynamic and kinetic information about reactive intermediates. Other calorimetric methods are discussed in more detail in a recent review.7... 

The methods of indirect and direct calorimetry may not always result in the same values for energy expenditure. Indirect calorimetry is a measure of the heat produced by oxidative processes. Direct calorimetry measures the rate of dissipation of heat from the body. An increase in the rate of heat production, as with exercise, may not always result in an immediate, measurable increase in heat released by the body (from the skin). Instead, the increase in heat production may result in a rise in body temperature. That part of the energy requirement used to raise... 

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