CO2 measurement
How is Carbon Dioxide Rebreathing measured?
The method developed by CPSC for measuring carbon dioxide rebreathing makes use of a mechanical machine that breathes in and out like an infant. (Reference 1) Carbon dioxide gas is metered into the lung at a rate representing infant metabolism and allowed to reach equilibrium. A CO2 analyzer is used to measure the CO2 concentration in the breathing circuit.
Breathmeter is a recent development combining an infant breathing model with an internal carbon dioxide analyzer. It is used for direct measurement of surfaces to quantify CO2 rebreathing.
CO2 Method Schematic
The CO2 method makes use of CO2 gas, a breathing machine, sample pump and CO2 analyzer. The probe is the same 3-inch hemisphere used for airflow testing.
new Rebreathing Analyzer
Self-containedd Portable CO2 Rebreathing Measurement Kit
The standard method and apparatus for measuring rebreathing makes use of a breathing machine, carbon dioxide gas and a carbon dioxide analyzer. Carbon dioxide is metered into a mechanically actuated lung and connected to an infant breathing model. With normal breathing, some CO2 is exhausted to the atmosphere with each exhaled breath. With bedding applied to the model’s face, rebreathing may occur and the concentration of CO2 will tend to rise in the model as it would in a live infant.
Soft sleep surfaces and infant products are known to be a potential factor for the occurrence of respiratory hazards. These hazards include airflow resistance and carbon dioxide rebreathing. The breathing model and CO2 analyzer provide a method of measuring the relative tendency of surfaces to retain exhaled breath and return it to the infant, leading to reduced oxygen and excessive CO2 delivery, a hazard.
The breathing machine models a sleeping infant. The respiratory rate and tidal volume are fixed and the probe models the face of an infant. Carbon dioxide is metered into the operating lung at a rate that models an infant’s rate of metabolism, resulting in a system that breathes oxygen in and carbon dioxide out, just like a live infant. When the probe is applied to a sleep surface, the level of CO2 rebreathing can be measured accurately and repeatably.
Breathmeter is based on a design developed at the US Consumer Product Safety Commission in 1979. (see references below) Carleton, Porter and Donahue published a paper describing the breathing machine and analyzer. Breathmeter uses the same breathing rate, tidal volume, residual volume and measurement technique as Carleton. The probe was developed By Dr. Erin Mannen’s BabiLab at Boise State University. The removable “nose” on the probe permits rebreathing measurements on all surfaces.