Difference Between Direct Calorimetry and Indirect Calorimetry

While direct calorimetry is achieved through direct measurement of total body heat produced, such as via a thermally sealed chamber, indirect calorimetry measures respiratory gases, i.e. oxygen (O₂) and carbon dioxide (CO₂) that are influenced by metabolism to meet energy requirements (Figure 1).

1. What is direct calorimetry?
2. What does the indirect calorimeter measure?
3. How accurate is indirect calorimetry?
4. How do you calculate indirect calorimetry?
5. What does calorimetry measure?
6. What is calorimetry method?
7. Is indirect calorimetry expensive?
8. What are examples of methods used in indirect calorimetry?
9. What is the purpose of indirect calorimetry quizlet?
10. What factors affect indirect calorimetry?
11. What describes a disadvantage of using indirect calorimetry?
12. Why is indirect calorimetry the gold standard?

What is direct calorimetry?

Direct calorimetry obtains a direct measurement of the amount of heat generated by the body within a structure large enough to permit moderate amounts of activity. ... Direct calorimetry provides a measure of energy expended in the form of heat. The technique of direct calorimetry has several disadvantages.

What does the indirect calorimeter measure?

Indirect calorimetry (IC), which measures oxygen consumption and carbon dioxide production, provides an assessment of energy expenditure.

How accurate is indirect calorimetry?

Accuracy of the instrument was based on ≤1.5% percent relative error from theoretical values, i.e. Respiratory Exchange Ratio (RER) = 0.667, and % Gas recovery = 100%.

How do you calculate indirect calorimetry?

Weir equation used to calculate energy expenditure: Energy expenditure = (3.9VO2 – 1.1VCO2) – 2.17 (urinary nitrogen) Abbreviated Weir Equation = used to calculate REE: REE = (3.94 x VO2) + (1.1 x VCO2)

What does calorimetry measure?

Calorimetry is used to measure the amount of thermal energy transferred in a chemical or physical process. This requires careful measurement of the temperature change that occurs during the process and the masses of the system and surroundings.

What is calorimetry method?

Calorimetry deals with the measurement of heats or heat flow rates. ... The principles generally used in calorimetry are either compensation of the thermal effect by suitable phase transitions or electric means or measurement of temperature differences. These temperature differences can be a function of time or position.

Is indirect calorimetry expensive?

Currently, the most accurate clinical tool used to measure REE is indirect calorimetry, which is expensive, requires trained personnel, and has significant error at higher inspired oxygen concentrations.

What are examples of methods used in indirect calorimetry?

Indirect calorimetry systems estimate respiratory gas exchange as a surrogate for substrates consumed and produced during metabolism. This is done by one of 4 methods: confinement, closed-circuit, total collection, and open-circuit approaches.

What is the purpose of indirect calorimetry quizlet?

Indirect calorimetry: one way to measure energy expenditure by measuring the respiratory exchange of O2 and CO2. This is called "indirect" calorimetry because heat production is more measured directly.

What factors affect indirect calorimetry?

Factors affecting REE include:

age • gender • body weight • body composition • weight loss • medications • exercise fever • disease • infection.

What describes a disadvantage of using indirect calorimetry?

Indirect calorimetry. Disadvantage of indirect calorimetry are: it cannot measure energy production by anaerobic processes, which can contribute a lot at higher exercise intensities. This means that measurement of energy expenditure by indirect calorimetry is much more accurate at low and constant work rates.

Why is indirect calorimetry the gold standard?

In order to prevent under- and over-feeding and their related complications, it is important to accurately assess REE in individual patients and to ensure adapted nutrition support. IC is considered as the gold standard to this purpose and ideally any patients in whom energy needs are uncertain should be measured.