Up to date, expert answers to frequently asked questions (FAQ) about oxygen supply systems, respiratory care and pulse oximetry written by OCC & collaborators.
Replace bacterial/viral filters as frequently as supplies allow in accordance with the manufacturer’s recommendations. This recommendation may be as often as every 24 hours, though the optimal interval may differ by setting and determined by assessing the risk:benefit of circuit disconnects, availability of supplies and ability to monitor for malfunctioning filters. Depending on location of the filter placement, circuit setup, humidification system and patient factors, B/V filters may function for multiple weeks, though this would be ‘off-label’ use. If an HME is used, a viral filter can be changed only with signs of increased resistance and may last a week or more. If a heated humidifier is used, the filter in the expiratory limb should be evaluated every 24 hours for signs of increased resistance and may need to be replaced every couple days, although this interval is highly variable. Always refer to the manufacturer’s recommendation. Lifespan may be significantly shortened if nebulized medications are being utilized or if copious secretions are present. Of note, disconnecting circuits can cause risk of aerosolization to healthcare workers.
Passive systems using Heat and Moisture Exchangers (HME) trap moisture and prevent it from being lost from the patient.
- Efficacy of these devices drop over time, causing increased resistance. Manufacturers may suggest a change every 24 hours, but studies have shown that an unsoiled device in some circumstances be used for several days or up to 1 week (Ricard et al, AJRCCM 2000; Thomacot et al, CCM, 2002; AARC. Resp Care. 2012).
- Signs of an increase in resistance include an increase in PIP but no change in Plateau pressure or a prolonged expiratory flow time.
- The most common cause of HME partial occlusion or rise in resistance is from pulmonary edema fluid or blood. Mucus generally clumps in a dependent portion of the device without increasing resistance appreciably. (Davis et al Crit Care Med. 2000)
- Always see manufacturer’s specifications.
- All external filters should be inspected at least daily
- For turbine and compressor ventilators, external inlet filters and fan filters must be cleaned (if cleanable per manufacturer) or replaced at least monthly. For ventilators that allow, bacterial/viral filters should be placed proximal to external inlet filters.
- For example, the LTV-1200: The external inlet filter should be removed and cleaned once a month and can be reused. If operated in high dust or humidity environments, it may need to be cleaned more often. The filter can be cleaned with mild detergent and warm water by using a soft cleaning brush. The filter must be rinsed thoroughly of all detergent residue and must be dried completely prior to re-insertion. If the filter is damaged or cannot be thoroughly cleaned, it should be replaced. The external inlet filter appears to be a proprietary item (Reticulated Foam P/N 10258)
- The fan filter should be removed and cleaned at least once a month (same cleaning procedure as described for the inlet filter). It also can be reused. If the ventilator is being operated in high dust or humidity environments, it may need to be cleaned more often. If the filter is damaged or cannot be thoroughly cleaned, it should be replaced.
- The LTV-1200 model also has an oxygen inlet filter that must be inspected and cleaned on a regular basis. It also is cleaned using a mild cleanser, warm water and a soft brush. Rinse the filter thoroughly to remove all traces of the cleanser. Allow the filter to dry completely before replacing it in the ventilator. Inspect the filter for damage. If it is not intact, or shows signs of damage or cannot be completely cleaned, it should be replaced. The filter is a proprietary item (O2 Inlet Filter (P/N 19845-001) and the accompanying O-Ring (P/N10609)
- The Zoll 731 ventilator: has an internal 2-stage filtration system (an outer foam filter and inner disk filter) to protect the gas flow. External filters should be visually inspected on a daily basis (or more frequently) for dust build up during extended operation in harsh environments and changed when they appear dirty. Use of external filters will preserve the life of the proprietary internal filters (foam filter REF#: 465-0028-00, Air Intake Disk Filter (REF # 465-0027-00). If external filters are not (or cannot be) used, the internal filters must be visually inspected on a regular basis and replaced when dirty. Note: proprietary internal filters cannot be cleaned and reused: they must be replaced.
- The Medtronic PB560 has an external air inlet filter that is intended to be replaced (~monthly or more often) rather than reused
Always reference the manufacturer’s recommendations as this varies. Most vents require a self test upon startup or when used on a new patient. There is additional preventive maintenance at regular scheduled intervals. All external filters should be inspected at least daily and for turbine and compressor ventilators, external inlet filters and fan filters must be cleaned at least monthly.
Elimination of a machine mounted inspiratory filter – If a bacterial viral filter is used between the circuit Wye and the patient, then an additional inspiratory filter between the machine and the inspiratory limb may not be necessary to protect the patient (so long as the machine is kept clean and an airway mounted filter and/or expiratory limb filter is used). That is a big “if,” and the use of an inspiratory limb filter at the circuit takeoff is to eliminate this chance of error.
A single inspiratory filter setup (at the wye) has been suggested as an option in settings of severe shortage. This setup may create potential for error and subsequent contamination of the machine. Additionally, the use of one instead of two filters in series significantly decreased viral filtration efficiency. The impact on risk of viral contamination is unknown.
Expiratory limb filter extended use (i.e. not changing between patients) has been suggested by some as an option if severe shortage is faced and appropriate bacterial viral filter is used at the patient. APSF