Ratgeber-Banner: HME-Filter und Beatmungsfilter

Choosing HME filters and bacterial filters for ventilation

4 min reading time

An HME filter exchanges heat and moisture in the breathing gas, a pure bacterial and viral filter only filters, and an HMEF combines both. When choosing a breathing filter, what counts is the product type, dead space, flow resistance, filtration performance according to the manufacturer, the 15/22 mm connectors and the specified tidal volume range for adults or children.

HME, HMEF or pure filter: the differences

The three product types look similar but perform different tasks. An HME (heat and moisture exchanger) absorbs heat and moisture from exhaled air and releases it with the next breath. A bacterial and viral filter retains particles in the gas flow. An HMEF combines both functions in a single component.

Type	Function	Key values in the data sheet
HME	Heat and moisture exchange	Moisture output, dead space, weight
Bacterial and viral filter	Filtration	Filtration performance, flow resistance, dead space
HMEF	Exchange and filtration	All of the above, plus weight

Which type is used at which point in the system is determined by your institution's standards and the instructions for use. For purchasing, the main thing is not to confuse the types: a pure HME has no filter function, even if it looks like an HMEF from the outside. Pay attention to the exact product name and item number.

Mechanical and electrostatic filters

There are two common types of filter media. Mechanical filters, often designed as a pleated hydrophobic membrane, retain particles through dense material. Electrostatic filters use an electrically charged non-woven fabric that attracts particles and often have lower flow resistance. Manufacturers state in their documentation how filter performance behaves under humidity. Compare this information if filters are to remain in the system for longer periods.

Comparing technical values correctly

The data sheet is the most important source for comparison. Put these values side by side:

Filtration performance: usually stated as a percentage for bacteria and viruses. Values are only comparable if you know the underlying test method. Test methods for breathing system filters are described in the ISO 23328 series of standards.
Dead space: the internal volume in millilitres. It plays a greater role with small tidal volumes, which is why there are separate versions for children.
Flow resistance: the pressure drop at a defined flow, stated in cmH2O or hPa.
Moisture output: stated for HMEs and HMEFs in mg H2O per litre. The test is described in the ISO 9360 series of standards.
Tidal volume range: the range for which the manufacturer intends the product.
Weight: relevant because many filters sit close to the patient on the breathing circuit.

Connectors, sizes and versions

Breathing filters use the standardised 15 mm and 22 mm conical connectors. Before ordering, check whether the combination of male and female connectors on both sides fits your breathing circuits, masks, tubes and bag valve masks. Other distinguishing features are:

Luer lock port for gas sampling, with a sealing cap
Straight or angled design
Versions for adults and children, with some manufacturers also for infants
HME versions with a connector for tracheostomy tubes
Type of packaging, for example individually packed, and sterility according to the manufacturer

Filters are often kept together with bag and mask as part of emergency equipment. Our article on choosing bag valve masks explains what to look for in the bag itself. You will also find suitable products in the Ventilation and Intubation and Emergency categories.

Change interval and demand planning

Breathing filters are single-use products. How long a filter may be used is stated exclusively by the manufacturer in the instructions for use. Your institution's standards may contain additional requirements. Therefore plan demand on the basis of this information and not by rules of thumb.

For storage, it has proven useful to keep the number of versions small. A few clearly labelled items for adults and children avoid mix-ups. Compare offers on the basis of the packaging unit, because each supplier on ShopMed24 sets its own packaging unit and price.

Selection checklist

Product type defined: HME, HMEF or pure filter
Filtration performance with test method stated in the data sheet
Dead space and tidal volume range suitable for the patient group according to the manufacturer
Flow resistance and, where relevant, moisture output compared
15/22 mm connectors compatible with existing systems
Gas sampling port, design and type of packaging clarified
Change interval according to the instructions for use included in demand planning

Related categories:

Frequently asked questions

What is the difference between an HME and an HMEF?

An HME only exchanges heat and moisture. An HMEF combines this exchange with a bacterial and viral filter in a single component.

Is a bacterial filter also a viral filter?

Many breathing system filters are specified by the manufacturer with a filtration performance for both bacteria and viruses. The values in the data sheet and the test method stated there are decisive.

Which connectors do breathing filters have?

The standardised 15 mm and 22 mm conical connectors are common. Before ordering, check whether the connectors fit your breathing circuits, masks and bag valve masks.

Are there breathing filters for children?

Yes, many manufacturers offer versions with a smaller dead space. The instructions for use state the tidal volume range for which a filter is intended.

How often is an HME filter changed?

The change interval is set by the manufacturer in the instructions for use, supplemented by your institution's standards. We do not give our own recommendation on this.

You will find suitable products in the Ventilation and Intubation category. If you are looking for a specific manufacturer's filter that is not listed, send us a product request.