Mixed Expired Gas Analysis

Our decision to use mixed expired gas analysis instead of Breath-by-breath analysis is based on the ever decreasing time that is available for analysing each breath directly (often less than 500ms). Timing has implications concerning repeatability, where sampling conditions should remain as constant as possible.

The COVOX Mixed Expired Gas Chamber has an internal capacity of just 500 ml, allowing much quicker sampling than standard sized chambers due to the small volume of air required to flush the chamber. The design eliminates end tidal volume bias, and being constructed of thin walled thermo-plastic, quickly assumes the temperature of exhaled air, preventing condensation within the chamber itself.

See Redbackbiotek for their Mixing Chamber Vs Breath by Breath article.

The COVOX Metabolic Cart detects instantaneous inspired respiratory air during each breath using a Fleisch pneumotachograph, the device we use, which due to its excellent linearity and turn down ratio of 20:1, allows accurate measurement of pulmonary ventilation (Ve) from rest to VO2max. The single flow head  meets ISO 26782:2009 spirometry standard, ISO 23747:2007 and fulfills all the ATS/ERS:2005 guidelines.

Accuracy Typically +/- 2 %,

Min Flow 0.02 l/s, Max Flow 16 l/s

The advantages of Fleisch diagnostic flow measuring systems include: Accurate and linear measurements throughout the flow range, robustness and no moving parts. Pneumotach moisture contamination is avoided by measuring inspired respiratory air, thereby eliminating surface condensation and contamination from moisture in the breath. An ultra low resistance filter is used to capture dust particles, further protecting the flow head.

COVOX uses the Teledyne UFO oxygen sensor, which was specifically developed as a reliable alternative to paramagnetic and optical sensors. The Teledyne UFO utilises fuel cell technology that is inherently rugged and forgiving.

Unlike many other sensors the UFO is insensitive to shock, vibration and will withstand exposure to moisture without damage. With an average response time of 100 milliseconds, the UFO is one of the fastest oxygen sensors in general use.

The sensor meets ISO 7767 (1997), ASTM F1462-93, and CE Medical Devices Directives.

Accuracy better than +/- 1.0% Reading

Resolution 0.1%

Preventive maintenance is not required. The gas sampling circuit is protected against the accumulation of expired gas moisture using a Perma Pure Nafion dryer. A reflux arrangement removes the need for regular dryer replacement.

Hybrid.

The COVOX Approach is to use simultaneously, breath-by-breath measurement of pulmonary ventilation (where sensors are capable of high sampling rates), and a mixed expired gas chamber for Oxygen and Carbon dioxide analysis.

Industrial. At the heart of the system is an embedded  industrial PC, running under the Windows Embedded Operating system. All the components used in the construction has a history of industrial use - reliability being of prime importance.