ME™–Series Medical Dryers for Breath Gas Analysis
Perma Pure manufacturers a wide range of Medical Breath Dryers for Breath Gas Analysis designed to remove the most common source of problems in medical gas analysis – water vapor in the gas sample. Water vapor can cause condensation in sample lines and measurement cells as well as interference with CO2 monitoring. Perma Pure ‘s ME-Series medical breath dryers use Nafion™ membrane tubing technology to bring the humidity level to ambient conditions, removing up to 90% of the water while leaving the oxygen, carbon dioxide, and anesthesia gases unaffected and virtually eliminating this source of medical gas analyzer failure. View main features and benefits:
- Selective membrane technology removes only water vapor, leaving what you want to analyze intact
- Eliminates water interference in Infrared CO2 monitoring
- Removes up to 90% of the water with only a short length of Nafion™ tubing
- Low dead volume = Fast response time
- Wide variety of common medical connectors available interface with existing equipment designs – View connector types here.
- Proven results in capnography, anesthesia monitoring, and metabolic testing
Principle of Operation
In drying applications, ME-Series medical breath dryers transfer water vapor from a wet gas stream into the surrounding atmosphere. Drying is complete when the sample humidity level is equal to the ambient humidity level. Since drying proceeds as a First Order kinetic reaction, this level can be reached extremely quickly, usually within 100 to 200 milliseconds. This behavior makes the dryer ideal for applications involving a very humid sample at room temperature.
Since breath is saturated with water vapor, liquid water will begin to condense as soon as the temperature of the breath begins to fall. Various devices are used to remove this condensate from the expired breath sample, such as hydrophobic filters and water traps. Although these devices remove liquid water, they do not remove water vapor. They also add dead volume to the sample circuit and must be drained or replaced when filled with water. Since water vapor is not removed by any of these devices, the problems may be reduced but are not eliminated.
Intelligent Product Numbering System
The patented ME™-Series moisture exchangers are constructed with injection-molded fittings for a gas-tight seal, while a polypropylene braid surrounding the Nafion™ membrane provides strength and protection. This design produces a rugged sample line that rapidly removes water vapor from a breath sample. View connector types.
The ME-Series is available in a variety of tube diameters, lengths and fitting combinations to accommodate a wide range of flow rates. Choose the size based on your flow rate and dryness requirement and build your ME according to the selection guide and the part number table below:
Selecting the Right Medical Dryer for Your Application
Dryers are selected based on the target dryness or moisture level required and the flow rate that of the sample through the tubing, normally defined by what the analyzer requires. Below are performance curves for the four sizes of medical dryers – click on the curve to enlarge.
For Flow Rates of 0-150 cc/min: ME-050 Series
For Flow Rates of 0-400 cc/min: ME-060 Series
For Flow Rates of 0-1000 cc/min: ME-070 Series
For Flow Rates of 0-1000 cc/min: ME-110 Series
Frequently Asked Questions – Medical Dryers
What is an ME medical breath dryer?
An ME dryer is a short length of Nafion™ tubing with a protective outer braiding.
How does the ME dryer function?
As water vapor in breath travels through an ME Dryer, it is absorbed into the tubing and evaporates into the surrounding air. Conversely, this product will also function as a humidifier and add ambient moisture to dry cylinder gases. The amount of water vapor removed by or added to the tubing will depend on the relative humidity outside the tubing.
What are the benefits of using an ME dryer?
ME dryers prevent downtime of breath gas analyzers since the most common source of analyzer problems is condensable water vapor in the sample. Accuracy and precision of the analyzers also improve when water interferences are eliminated.
Where should the ME dryer be placed in the sample line?
When the dryer is located near the patient, the breath sample is still warm and will not have a chance to condense in the sample line. This placement is beneficial to the ME’s performance, as the water vapor transfer rate through the tubing increases at higher temperatures.
Should the ME Dryer be replaced after every procedure?
Since it is part of the sampling line, it should be treated as such. Some customers treat these dryers as disposable for hygiene reasons. The dryers are very durable and can theoretically be used for months without replacement. Each hospital, however, has its own guidelines and we defer to individual institutional policies.
What are the advantages of an ME Dryer compared to a water trap or HME?
Simplicity – A water trap collects liquids that must be drained periodically. Since the ME dryer is removing water vapor, no condensate is formed, and the potential for liquid carryover is eliminated. Further there is absolutely no operator interaction or maintenance required. Performance – The breath sample at the outlet of a water trap is still saturated (100% RH), whereas the ME will reduce the sample humidity to room levels (generally 30-50%RH). Analytical Accuracy – Using a water trap for moisture removal in the presence of water soluble compounds such as NO2 causes sample integrity problems, since they can dissolve out in the condensate. An ME Dryer will selectively remove water vapor without affecting the gases being measured.
Is a water trap or HME still needed?
No water trap is required to remove water. A filter to remove sputum is still desirable.
Can an ME dryer be sterilized?
The preferred method of sterilization is gamma radiation. Our recommendation is to utilize the dryer in the unsterilized condition and change it after each operation. If sterilization is desired, gamma radiation is the preferred method.
What is the size of an ME dryer?
The length of Nafion™ tubing required is determined by the sample flow rate and ambient humidity to which it is exposed. As a general rule of thumb, a 6″ dryer can be used for a sample flow rate of 75 cc/min and a 12″ dryer can be used for flows of 150 cc/min or less. Once the sample RH reaches ambient levels, moisture exchange ceases.
How cost effective is the ME Dryer?
Significant cost savings can be realized by the elimination of repairs and downtime of equipment caused by wet samples. No one can place a dollar value on preventing a gas monitor failure at a critical juncture during a medical procedure.
What is the proper disposal method for a used dryer?
The dryer can be disposed of using the same procedures as for any vinyl plastic components used in the hospital; land fill or special incineration. The product is very stable and will not decompose.
Can I clean the ME Dryer?
Because of the unique construction of the ME Series, Perma Pure strongly recommends against using liquid water or alcohols to clean them. Both liquid types have the tendency to swell the Nafion, possibly causing the material to deform and kink within the protection braiding during full contact, restricting gas flow and reducing drying performance. In situations where this type of cleaning is deemed necessary, in order to limit the swelling effect, Perma Pure recommends that the cleaning process be done quickly and that clean dry air be used immediately following the cleaning to quickly remove the moisture from the tubing after contact with liquid water or alcohol.