What are the guidelines around using nebulisers with COVID-19 patients?
There may be differences in guidelines concerning COVID-19 patients in different countries. Please consult the health authority guidance in your specific region. The World Health Organization (WHO) guidelines recommend using airborne precautions when performing an aerosol-generating procedure (AGPs)1.
What is the difference between medical aerosols and bioaerosols?
These are two very different types of aerosol. Medical aerosols are aerosolised medications delivered to the patient that do not contain pathogens. Bioaerosols are airborne particles that are living (bacteria, viruses and fungi) or originate from living organisms. Bioaerosol can include suspensions of airborne pathogens. It’s important to note that medical aerosols can become bioaerosols if they are contaminated.
During mechanical ventilation, is there any chance of releasing contaminated aerosol and exposing healthcare workers when you open the medication cup?
The Aerogen Solo is designed so that the medication reservoir is isolated from the breathing circuit and therefore this would minimise the potential for contaminated fluid entering the medication cup. Unlike jet nebulisers, opening the Aerogen Solo medication cup does not allow for escape of flow from the ventilator. Therefore no fluid will be released from the nebuliser when the medication is added to the cup. To ensure that no infectious material is introduced into the medication cup, it is important that the caregiver administering the treatment uses proper aseptic technique, and uses the appropriate personal protective equipment. Aerosol produced by the Aerogen solo is medical aerosol and does not contain contaminates unless it is contaminated by a user that is not using proper aseptic technique. It cannot be contaminated by the ventilator circuit or patient.
Can you use the Aerogen Solo for continuous nebulisation during mechanical ventilation?
The Aerogen Solo system is suitable for intermittent and continuous nebulisation. For continuous use, the life of the Aerogen Solo nebuliser and the Continuous Nebulisation Tube Set CNTS have been qualified for use for a maximum of 7 days. The Aerogen (CNTS) is an accessory specific to the Aerogen Solo nebuliser which enables safe continuous infusion of liquid medication for aerosolisation2. When using the Aerogen Solo for continuous nebulisation during mechanical ventilation, it is advised to utilise an active humidification system with a heated humidifier, as opposed to a Heat and Moisture Exchanger filter (HME/F). There are several problems associated with continuous nebulisation of medication when using a HME. Due to increased moisture in the tubing there may be a need to frequently break the breathing circuit to replace the HME which may increase the risk of infection. It could also potentially increase the patient’s work of breathing and autoPEEP, if the condition of the HME is not monitored sufficiently.
Can you advise on best placement of the Aerogen Solo during mechanical ventilation?
When utilising a bias flow, Ari et al. and Berlinski et al. demonstrated improved deposition when the Aerogen Solo was placed on the dry side of the humidifier compared to at the wye, with both adult and paediatric settings3,4. However, some of the current guidelines for treatment of patients with suspected or confirmed COVID-19 recommend to avoid water based humidification and to use a HME/F5. Bennett et al. compared aerosol delivery with active humidification and a HME with the Aerogen Solo placed between the wye and endotracheal tube during simulated adult and paediatric mechanical ventilation, and showed that aerosol delivery was substantially equivalent across the two modes of humidification6. If using a passthrough HME, placement at the outlet of the ventilator with bias flow in the inspiratory limb is recommended. It is important to remember to reactivate the HME post treatment. Aerogen only recommends the use of HMEs approved for aerosol delivery.
Can you use a HME while delivering aerosol with the Aerogen Solo?
When using a HME, the Aerogen Solo should be placed between the HME and the patient. Placing the nebuliser back at the ventilator will likely affect the functionality of the HME and it may impede the aerosol and limit the amount reaching the patient. Only use with HME devices whose manufacturer’s instructions allow use with a nebuliser, and always follow the HME manufacturer’s instructions. Ensure that the total combined volume of nebuliser, T-piece and/or HME is suitable for the tidal volume being delivered and does not increase dead space to the extent that it adversely impacts the ventilatory parameters of the patient. Always monitor the resistance to flow and excessive rain-out and change the HME device as per manufacturer’s instructions. Do not use a filter or HME between the nebuliser and patient airway. Always position ventilator circuits so that fluid condensate drains away from the patient. Always connect a bacteria filter to the expiratory inlet of the ventilator, otherwise the function of the expiratory channel may be degraded2.
Can you deliver an effective dose using the Aerogen Solo during mechanical ventilation?
ugernier et al. documented lung dose with the Aerogen Solo in a randomised trial of neurosurgical patients with healthy lungs. They compared volume-controlled ventilation and pressure support ventilation. They demonstrated lung deposition of 10.5 ± 3.0 and 15.1 ± 5.0 % of the nominal dose with the Aerogen Solo during pressure support and volume-controlled ventilation, respectively (p < 0.05). Higher endotracheal tube and tracheal deposition was observed during pressure support8. An earlier study showed that only 3 % lung dose during ventilation with use of a jet nebuliser9.