These are for use with ICU ventilators that have the ability to provide NIV, and are commonly used to provide NIV in Europe.
Setup 1: Non-vented mask in a dual-limb system: Recommended
The majority of guidance where NIV is indicated in the treatment of COVID-19 patients recommends the use of a non-vented mask in a dual-limb system (where venting is not required) to reduce caregiver exposure to aerosolization. However, many regions will see these ventilators required for invasive ventilation, and the use of NIV on single-limb systems (dedicated NIV ventilators, Bi-level and CPAP devices) may be necessary.
Dedicated NIV ventilators, Bi-level and CPAP devices are generally single-limb systems. These single limb systems require venting of the patients exhaled breath to prevent the buildup of CO2 .
- A non-vented mask with an exhalation port should be used rather than a vented mask.
- Vented masks could worsen contamination of the environment.
- Ensure the employed ventilator mode supports the use of non-vented masks and exhalation ports.
Setup 2: Non-vented mask in a single-limb system exhalation port filter: Recommended
- Ideally an exhalation port with reduced jetting should be used. Typically, this has a shroud around the exhalation holes to reduce air entrainment and an array of small holes creating a diffuse flow.
- An exhalation port with the ability for the exhaust to go through a filter should be employed to reduce aerosol dispersion.
- A low resistance-to-flow filter is recommended to reduce CO2 rebreathing and maximize the percentage of gases being filtered.
Setup 3: Non-vented mask in a single-limb system in line filter: Not Recommended
Some guidance recommends the system uses a filter between the mask and exhalation port. There are some major drawbacks of this setup.
Fisher & Paykel Healthcare don’t recommend this setup if you already have an exhalation port which allows a filter to be attached to reduce aerosols being released into the environment.
Reasons we do not recommend this setup include:
- This will likely increase dead space, work of breathing and potentially reduce the efficacy of treatment.
- Triggering and pressure delivery may be affected due to the resistance to flow of the filter.
- Inspiratory flow may be exhausted out the port before reaching the patient due to the inline filter’s resistance to flow.
- Secretion accumulation may cause filter blockage.
- Frequent replacement of the filter is required, which in this setup involves breaking the circuit, increasing the risk of infection for caregivers.
Setup 4: Use of altered vented masks for NIV: Not Recommended
The COVID-19 pandemic has led to an increase in demand for medical products such as NIV masks, and has also highlighted the potential for shortages. Customers and healthcare professionals have asked for guidance on using vented masks such as (OSA CPAP masks and vented hospital masks) to deliver NIV in hospital in case non-vented NIV masks are unavailable.
While the intended use allows for vented CPAP masks to be used in the hospital, there is an increased risk of aerosols jetting into the environment because of the vented configuration.
And as above vented NIV masks are not recommended for the same reason.
The following guidance can be used to highlight the main considerations in the case that a vented hospital or CPAP mask is the only option for delivering NIV in the hospital. It is not a recommended setup.
- Covering of the exhaust flow/venting holes can pose a risk to the patient. If the holes are sealed, there MUST BE another source of leak in order to flush out CO2. This may increase the dead space of the mask.
- There are typically two types of vented mask:
- Vented hospital masks commonly used in the delivery of NIV. When aerosol generation is not a concern, these masks are normally single-patient use
- Vented CPAP masks that are typically used by patients with OSA in a home setting, but often also used in respiratory wards and sleep labs.
- The exhaust flow holes in CPAP masks are similar to a vented NIV mask and it is difficult to filter the air from them.
- The same precautions as above regarding aerosolization from NIV masks, such as wearing appropriate PPE, should be taken when using CPAP masks.
- The source of leak could be in the form of an exhalation port such as the F&P RT017.
- A filter can be placed over the exhaust port of the RT017 exhalation port (see setup diagram below).
- Most exhalation ports will not directly connect to a vented mask and will require a 22mm Female – 22mm Female connector.
Setup 5: PEEP Valve Setup: Not Recommended
A low-cost method of delivering CPAP to patients in hospitals is to use a non-vented NIV mask and a Peak End Expiratory Pressure (PEEP) valve with a flow source or pressurized source of air. The exhaust in this setup exits when the PEEP valve is activated and may require a filter to reduce aerosols being released into the environment.
- The following should be taken into consideration when a filter is added to the PEEP valve setup:
- The considerations regarding aerosolization and NIV therapy as set out above.
- The considerations regarding filter selection as set out above.
- The filter must be monitored for blockages and replaced as required.
- The replacement of the filter in this setup will interrupt the therapy delivery.
- The delivered pressure will be higher than the PEEP valve setting due to the pressure drop across the filter, particularly when higher flow rates are used. A higher resistance to flow filter will result in the patient experiencing higher pressures.
- A safety pressure relief valve must be used in this setup, particularly if the flow source is wall air, as the occlusion of the filter may cause high pressures to build up.
- There may also be additional back pressure experienced by the patient upon exhalation due to the resistance in flow of the filter. This may negatively affect work of breathing.