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The device is indicated for use in mechanically ventilated neonate, infant and pediatic patients where the precise and direct measurement of oxygen uptake (VO2), carbon dioxide excretion (VCO2), resting energy expenditure (REE) and respiratory quotient (RQ) will allow the attending physician to plan and monitor an optimal nutrition regime for the patient in terms of substrate composition and utilization.

The NICU V'O2 device is an indirect calorimeter that allows accurate and precise quantification of oxygen consumption (V'O2), carbon dioxide excretion (V'CO2), resting energy expenditure (REE, the number of calories consumed per day) and respiratory quotient (RQ, the ratio of V'CO2 to V'O2) in mechanically ventilated patients. Patients include neonate, infant and pediatric patients with a body weight from 0.5 kg, low minute ventilation, high respiratory rate, and receiving fluctuating and/or elevated inspiratory oxygen concentrations. The device functions by measuring oxygen concentration (using laser diode sensor technology) and carbon dioxide concentration (using NDIR infrared sensor technology) in inspired and expired gas as well as inspiratory flow. The inspiratory flowmeter (differential pressure type pneumotach) is attached at the patient inspiratory outlet of the ventilator. An inspiratory gas sample line is connected to the inspiratory limb of the patient breathing circuit, and an expiratory gas sample line is connected to the ventilator exhaust. The device automatically alternates between these two sample points. Oxygen consumption is determined by comparing the amounts of oxygen in inspired and expired gas, and carbon dioxide excretion is determined by comparing the amounts of carbon dioxide in expired and inspired gas, respectively, per unit of time. These amounts are calculated from the primary measurements of oxygen and carbon dioxide concentrations and gas flow. The resting energy expenditure (or resting metabolic rate), which is defined as the number of calories the body expends daily during resting conditions, is calculated from the values of oxygen consumption and carbon dioxide excretion using the modified Weir equation: REE = (V'O2 x 3.941 + V'CO2 x 1.106) x 1440 kcal min / day L Respiratory Quotient is calculated as the ratio of carbon dioxide produced by the patient to oxygen consumed by the patient. The duration of measurement can be from tens of minutes to 24 hours, partly because the inspiratory flowmeter only sees dry gas and therefore does not significantly change calibration over time. The device consists of two main components. An analyzer unit to which the patient is connected via gas sample and flowmeter pressure lines, and a computer running the dedicated software application under the Windows operating system. The software application works in conjunction with the hardware, and the computer presents in real time measured signals and computed physiological parameters, both as numeric and graphical data. The computer is the main control interface for the ICU staff using the device and offers options for offline data management. The device is powered through an external medical AC/DC power supply.