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The device is intended for use in clinical and research applications to measure oxygen uptake.

The REEVUE is an indirect calorimeter. The REEVUE device measures oxygen consumption (VO2) and estimates Resting Metabolic Rate (RMR) based on the measured VO2 using an assumed respiratory quotient (RQ=0.83). Resting metabolic rate can also be referred to as Resting Energy Expenditure (REE).

Measurement of energy requirements can be used for nutritional assessment. A typical application would be for counseling obese patients on their caloric intake requirements.

During a test the patient breathes through a mouthpiece with unidirectional breathing valves. These valves allow the patient to breath in ambient air and then direct the expiratory gas down a hose to the device. The flow rate of the expiratory gas is measured and the patient's tidal volume and respiratory rate is calculated. The expiratory gas passes through a mixing chamber so that the mixed expiratory oxygen concentration can be found. The oxygen concentration of the mixed expiratory gas is measured.

Oxygen consumption can be expressed as the volume of oxygen breathed in minus the volume of oxygen breathed out. This can be described as:

[VO2 - VI|IO2 - VE|E O2] (1)

where VO2 is the oxygen consumption, VI is the inspiratory volume, FIO2 is the inspiratory oxygen fraction, VE is the expiratory volume, and FEO2 is the expiratory oxygen fraction.

Since the REEVUE only measures the expiratory volume of gas breathed out, the inspired volume must be estimated. This is similar to other legally marketed medical devices. When measuring both CO2 and O2 this is often referred as the Haldane method.

To estimate the inspired volume, the components of the expiratory and inspiratory volumes need to be accounted for. In estimating the inspiratory volume the REEVUE requires an estimate of the Respiratory Quotient (Ro). The REEVUE uses an assumed RO of 0.83. The RO is defined as:

RQ = VCO2 / VO2 (2)

where VCO2 is the carbon dioxide eliminated by the patient's breathing.

An estimate of Resting Energy Expenditure (REE) is calculated using the Weir Equation with the assumed RO value of 0.83. Substituting for the VCO2 using the RO and the VO2 the Weir Equation can be expressed as:

Calories = { 3.941 VO2-STPD + 1.106 RQ VO2-STPD } x { 1 - 0.082 PF } (3)

Where

Calories .......... is the calories burned per liter of oxygen consumed. PF ......................is the fraction of total energy production due to protein oxidation.

Typical values for Pr range from 0.08 to 0.2, corresponding to 8 to 20% protein. We selected a default value of 0.125 for our calculations. In reporting (REE) in Kcal/day, this simplifies to:

RMRKcal/day = 6.925 x VO2-ml/min-STPD (4)

Here's a breakdown of the acceptance criteria and study details for the REEVUE Indirect Calorimeter, based on the provided 510(k) summary:

REEVUE Indirect Calorimeter: Acceptance Criteria and Study Details

1. Table of Acceptance Criteria and Reported Device Performance

Non-Clinical Performance Criteria (Nitrogen Injection Method):

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