Oxygen Supply & Delivery FAQ

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Continuous Positive Airway Pressure (CPAP) devices or modes apply constant pressure throughout the respiratory cycle via face mask or other interface to splint open the upper airway, increase lung volume, and increase intrathoracic pressure. CPAP provides no inspiratory muscle unloading and tidal ventilation remains completely dependent on the respiratory muscles.

Non-invasive ventilation (NIV) or Non-invasive positive pressure ventilation (NIPPV) applies two levels of pressure during the respiratory cycle – a pressure during the inspiratory phase that is greater than the pressure applied during exhalation.  This is effectively mechanical ventilation, and can unload the respiratory muscles and provide complete respiratory support.

Bilevel positive airway pressure (BIPAP) is a branded/trade name (by Phillips) for NIPPV/NIV as described above

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It depends on the positive pressure device and circuit being used. If a single limb circuit without an active exhalation valve is being used (e.g. a home NIPPV machine), then a vented mask or vented circuit must be used (i.e. fixed orifice resistor outlet). If a dual or single limb circuit with an active exhalation valve is being used, then an NIV mask without a vented port should be used.

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Boussignac is a low cost, easy to use facemask CPAP system that has no sensors, mechanical valves or electrical components. The system connects to an oxygen flowmeter/source that generates flow dependent pressure (8LPM ~3cmH20; 15LPM ~5cmH20; 23LPM ~10cmH20)

Traditionally used by prehospital providers for cardiogenic pulmonary edema

In patients with hypoxemic respiratory failure (non cardiogenic pulmonary edema), it is unclear if this device would work well in patients with high minute ventilation (Sehlin et al, Resp Care, June 2011).

At high flows will cause airway dryness and discomfort.

No leak compensation

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Most modern ventilators provide some form of NIPPV, however, there are significant differences in performance among devices. Much of the difference in performance is attributable to ability to compensate for large leaks (e.g. around the mask seal) and trigger latency. Newer ventilators may perform significantly better than older ventilators.

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Any time the patient can cough or sneeze into the room – the  risk of infection is increased. Some model studies show that if there is a mask leak – the high flow from the ventilator to compensate for the leak may force particles out into the room.

During the 2003 SARS CoV-1 outbreak, many healthcare workers became infected due to failure to implement adequate infection control precautions especially when performing aerosol generating procedures (Tran et al. PloS One 2012). However, because of the limited number of studies reporting NIPPV use in SARS CoV-1, the risk of infection could not be established with certainty. Moreover, in a Singapore study of SARS CoV-1, institution of rigorous protective measures (including air-purifying respirator units) for over 200 healthcare workers resulted in zero cases of infection (Lew et al JAMA 2003).

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Any time the patient can cough or sneeze into the room – the  risk of infection is increased.  It is not clear that adding high flow nasal oxygen makes this worse.  However, at a flow of 40-60 lpm if the patient coughs, model studies have shown some additional movement of particles in the room.

Healthcare worker infection from nosocomial transmission of SARS CoV-1was associated with lack of adequate infection control precautions especially in the presence of  aerosol generating procedures. By definition this would also include HFNC. However, the risk of health care worker infection from HFNC was reported to be substantially less (8%) compared to intubation (35%) and NIPPV (38%) (Raboud et al. Plos One 2010). Moreover, placement surgical masks over a HFNC reduces the emission and dispersion of coronavirus bioaerosols (Leung et al. Nat Med 2020)

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Here is a comparison table by ECRI.

(Please reference the manufacturers’ manuals as the accuracy of this table is not guaranteed).

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Here is a comparison table by ECRI

(Please reference the manufacturers’ manuals as the accuracy of this table is not guaranteed).

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This is somewhat controversial. 

For short periods of time (hours), NIPPV may be tolerated without humidity, but for longer periods of time (days) humidity is essential, especially at high FIO2 (100% oxygen from a tank or other high pressure source is ~anhydrous). Leaks with NIPPV (around a mask seal) create issues with humidification and is one reason HMEs don’t work well with NIPPV. 

For HFNC, most people find >6LPM NC intolerable without humidification, but with humidification most people don’t notice flow until it exceeds 15LPM and will tolerate >40LPM. With HFNC (and nasal CPAP) gas flow is unidirectional (in the nose and out the mouth) and thus there is no possibility for reclaiming moisture from the exhaled breath. Without heat and humidification most patients will find this intolerable.  

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Please reference the WHO Technical Specifications for Ventilators for a full list.

Some key considerations include whether the device can:

  • Optimally utilize locally available oxygen and power supplies
  • Deliver pressures (Inspiratory pressure 0-40cmH20, PEEP 0-20 cmH20), respiratory rates (tailored to the desired patient population), tidal volumes (that include at least 4-10cc/kg for the desired patient population), and FiO2 (21-100%)
  • Provide standard alarms and monitoring, including plateau pressure and tidal volume measurements
  • Proven reliability to deliver ventilation reliably for consecutive weeks
  • Be utilized with viral filters and humidification systems
  • Includes control modes and modes for weaning (at least AC-VC, AC-PC and PSV)

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The term transport ventilator can refer to a wide range of ventilators in terms of capability. Generally, the term ‘transport’ refers to the capability to use the ventilator for transporting patients during which time central power and pressurized gas supply may be limited. These ventilators usually have robust internal battery backups and the ability to function without a high pressure gas supply (e.g. they include a turbine or compressor to entrain room air to drive the ventilator). Most can also operate with either high or low pressure oxygen input. Many transport ventilators are designed to care for intensive care unit patients (See WHO Technical Specifications for Ventilators).

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Most transport ventilators are designed for continuous use for weeks or months at a time. There is scheduled preventative maintenance and the need for circuit and filter care as for any ventilator. Most of these ventilators are designed to operate for more than just a ‘transport time.’

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Many transport ventilators are specifically designed to care for critically ill patients and designed to do so for consecutive weeks or more.

See WHO Technical Specifications for Ventilators for care of severe COVID-19 patients

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    • When connected to a high pressure oxygen supply transport ventilators can deliver the FiO2, minute ventilation and pressures required to take care of most critically ill patients.
    • Transport ventilators are durable and designed for use in harsh environments
    • Transport ventilators usually have a turbine or compressor so that they can operate without a high pressure source of medical air. Most non-transport ventilators do not. When connected to a low pressure oxygen supply (such as an oxygen concentrator), transport ventilators may not be able to deliver the FiO2 required to take care of many critically ill patients.
    • Transport ventilators are often louder (especially compressor driven vents) than non-transport ventilators. If there are multiple patients in the same room on these vents, special attention may be required for monitoring. 
    • Transport ventilators may have limitations in terms of monitoring and displays  
    • Transport ventilators usually have at least the basic modes necessary for critical care, though may have fewer features for customization than traditional ICU ventilators 
    • Relative to some other non-transport ventilators, transport ventilators may have limited NIV functionality (HFNC, CPAP, BiPAP functions) or may not be as good with asynchronous patients
    • Transport ventilators can run without external power (for short periods of time), and without oxygen supply, or compressed air supply  
    • See these comparison tables of transport ventilators and non-transport ventilators by the ECRI. (Please reference the manufacturers’ manuals as the accuracy of this table is not guaranteed). 

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There are insufficient data to recommend significant deviations from traditional lung protective ventilation. This remains an ongoing area of debate with new data emerging. Please review current literature. (Link to ARDSnet Card)

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High pressure oxygen sources are capable of delivering oxygen at ~50psi/4bar to a device. These include oxygen cylinders (via regulator), oxygen plants via a compressor, liquid oxygen (via vacuum insulated evaporators) and very few portable oxygen concentrators (via additional compressor). High pressure oxygen is required for most ventilators, high flow nasal cannula and non-invasive positive pressure ventilators when taking care of critically ill patients.

Low pressure oxygen sources deliver oxygen at far less than <50psi/4bar. These include oxygen from a low flow flowmeter or a portable oxygen concentrator. Generally, these cannot deliver high enough oxygen concentrations to take care of severely hypoxemic patients.

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Ventilators without a turbine or compressor generally require both high pressure oxygen (green) and high pressure air (yellow) input to function appropriately, and cannot function at all without at least one of these

Ventilators with a turbine or compressor have the ability to entrain room air directly without a compressed air source; and have variable gas inputs depending on the manufacturer, including the ability to have some combination of:

  1. low pressure oxygen (e.g. from a portable concentrator), via common smooth bore oxygen tubing (this may require a reservoir to augment FiO2 and an adapter to connect to the device)
  2. high pressure (55psi/4bar) oxygen (from central pipes or a cylinder)
  3. high pressure air (usually not, as the turbine or compressor provides this)

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Most ventilators operate with 35-65 psig/4 bar inlet which is sufficient to operate the blender (i.e. what mixes 100% oxygen and air). Without adequate pressure the device may not function at all or with inaccurate delivery of volume, pressure and oxygen concentration. If a reliable high pressure gas supply is not present, consideration of ventilators with turbines or compressors may be critical.

Some ventilators that measure FiO2 will alarm if you connect something less than 100% oxygen to them.  Some ventilators (especially transport ventilators) may not have an FiO2 sensor and just display the blender fraction setting, not a direct measurement of concentration (this requires calibration during preventative maintenance).

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Some ventilators like the LTV 1200/2200, PB560 and Zoll 731 can run off of a low pressure oxygen supply. They utilize 21% air for the room via built in compressor or turbine and mix that with the low pressure oxygen input. Any ventilator running off of low flow oxygen usually will not allow you to use the blender – i.e. you can’t set the FiO2 as the FiO2 will be determined and change with minute ventilation changes and flow input. When using low pressure oxygen on devices with bias flow (flow during the expiratory time) and/or during NIV modes with leak compensation, the FiO2 can be diluted significantly.  For example, for the LTV1200 on a patient with 10 LPM minute ventilation and 5 or 10LPM input low pressure oxygen, max FiO2 is approximately 50 and 75% respectively. Slightly higher FiO2 may be observed with ventilators that offer an external reservoir (e.g. Zoll 731) on the compressor intake. Other ventilators that only accept low flow oxygen may be limited in the amount that can be delivered into the device at low pressure and thus be limited in FiO2 delivery (e.g. the PB 560 manufacturer recommendation is FiO2 max of 50%).

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Use this Oxygen supply calculator

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Use this Oxygen calculator

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Most portable oxygen concentrators use pressure swing adsorption to intake room air and output ~96% oxygen at 5 or 10LPM max, and at low pressure (this means far less than the 50psi/4bar needed to run HFNC, and most ventilators and NIPPV devices).  There are a few portable devices capable of higher flow / high pressure output. See manufacturer specifications as well as prior studies evaluating continuous performance variability in hot and humid environments (Peel et al, Anaesthesia, 2013).

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  • Large J size (6800 L) oxygen cylinders (filled at 137bar/~2000psi) commonly have a Bull Nose (BS 341) oxygen outlet. Many smaller cylinders have the same outlet. Pin Index cylinders (ISO 407) may be unavailable in some resource variable settings.  
  • A regulator with Bull Nose connector attaches to the tank to decrease the pressure from 137bar/2200psi to ~4 bar/50psi
  • Regulator outlet connectors vary (4 bar) high pressure connectors are 1/4” hose outlet, 3/8” BSP or Shrader (BS 5682) quick release (left to right in image).

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Ventilator connections vary but NIST connectors are common. Most ventilators are supplied with a high pressure hose with a NIST fitting on one or both sides and the other end of the hose with a fitting suitable to match the oxygen source (e.g. Shrader quick release)

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Low pressure outlets are most commonly attached to, and driven by, a flowmeter attached to a pressure regulator as shown, these types of outlets are simple push fit and similar to the outlets on oxygen concentrators (e.g. use smooth bore oxygen tubing)

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Most oxygen regulators will have a gauge attached, a full J size oxygen cylinder full will have a weight of 78kg (172lb) the oxygen contained in the cylinder weighs approximately 9kg (20)lb, Therefore gauging the volume of oxygen in a cylinder is difficult.

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  • Without access to an oxygen analyser it can be difficult to determine the gas contents in a cylinder. International standards for color of cylinders are not straightforward.
  • Most cylinders are filled using pressure swing adsorption (PSA) oxygen plants and thus have a maximum FiO2 of 95%  and often considerably less.
  • Older oxygen cylinders may be black with a white top. Outside of these standards many variations also exist.  All the cylinders in the images below contained oxygen.
  • Oxygen analysers should be used to determine gases before use. Cylinders require routine testing and cleaning by certified technicians. Outlet fittings should be examined for damage or corrosion.

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Below is a partial list of items to consider when caring for patients on a mechanical ventilator. Also included are partial lists of manufacturers’ ventilator accessories for two ventilators to serve as examples.

Parts inventory

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No. There are many different types of ventilator circuits and not all can be used interchangeably. Even for circuits that can functionally be used interchangeably (i.e. they will connect to the ventilator and patient), there may be differences in deadspace and circuit compliance that must be considered. If you would like to learn more, please see question “What different types of ventilator circuit exist?”

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  • There are multiple configurations of dual and single limb circuits (outlined below).
  • Note on humidification & circuit configuration: some dual and single limb circuits may contain a heated wire in the inspiratory limb to optimize heat & humidification delivery to the patient and to prevent excess condensation from accumulating when using an active heated humidification system. If an active heated humidification system is used in the absence of a heated wire inspiratory limb, a water trap is often needed. Some water traps may allow for emptying without circuit disconnect (an important consideration with COVID19). 
  • Dual limb circuit (Figure a, b and c) – used by most traditional critical care ventilators. Flow/pressure and PEEP are commonly measured/controlled in the machine, and thus no additional circuit transducer tubing is needed (a). Some circuits do use proximal flow/pressure sensors (b). These may include a heating element in the inspiratory limb and port for temperature monitoring (c). 
  • Standard single limb with built in leak (figure A) – mostly for non invasive devices
  • Standard single limb circuit with active exhalation valve and internal PEEP – (figure B and C) – These circuits are made by multiple manufacturers and can work with multiple vent models. 
  • Standard single limb circuit with active exhalation valve and manual PEEP – (figure D)
  • Standard single limb circuit with active exhalation valve, internal PEEP and proximal pressure sensor – (figure E) – this is one of the most common single limb circuit setups
  • Standard single limb circuit with active exhalation valve, internal PEEP and two proximal pressure/flow sensors – (figure F) – this is usually a proprietary circuit type that is commonly encountered and allows measurement of exhaled tidal volume

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  • Most ventilator circuits are not reusable (only a few are)
  • Check with the manufacturer specification and clinical guidelines to determine if reuse is safe
  • Steps for disinfection must be closely adhered to (see manufacturer specific instructions) 
  • Some reusable circuits may have a finite lifespan (e.g. a predefined number of sterilizing cycles).  

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Breathing circuits should be changed between new patients though do not necessarily need to be changed on a routine basis for the same patient; change the breathing circuit only if it has been soiled or damaged (Han, Liu. Respir Care 2010).

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The amount of water consumed per day by active humidification depends upon several factors including minute ventilation requirements and the ability of a specific humidification system to reach and maintain the goal of providing between 33 to 44 mgH2O/L of ventilation. Under ideal conditions (use of a heated wire circuit to prevent rainout) at low (5L/min), average for critical-illness (10L/min) and high (15 L/min) minute ventilation demands, the estimated daily consumption would be approximately the following: For the gas conditioning criteria of 33-44 mgH20/L estimated H2O consumption would be approximately 250-300, 500-600 and 700-1000 mL/day, respectively.

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Moisture present in patients’ lungs is rapidly lost at high breathing rates.

When breathing dry air, cilia stop functioning properly (in a matter of hours – Hirsch et al J Appl Physio 1975). When the moisture level becomes low, mucous in the patient’s lungs can become thick and hard, and quickly block the patient’s airways, or the endotracheal tube, stopping airflow. 

Additionally, heat is rapidly lost to non-humidified air.

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Passive systems:

  • Non-heated bubble humidifiers – are simple, low cost devices used with low flow oxygen delivery devices like nasal cannula or nasopharyngeal catheters. These devices require sterile or distilled water and are generally not efficient. Some may be reusable or single-use only.
  • Heat and Moisture Exchangers (HME) are simple, low cost components used with mechanical ventilators and CPAP or NIPPV devices. HMEs trap moisture and prevent it from being lost into the ventilator. They are not reusable.
    • Efficacy of these devices drop over time, causing increased resistance. Many manufacturers suggest a change every 24 hours, but studies have shown that an unsoiled device in some circumstances be used for several days (Ricard et al, AJRCCM 2000; Thomacot et al, CCM, 2002).
    • 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)
    • Read more about how often HMEs should be replaced

Active systems:

  • Active heated humidification systems use a reservoir of water and a heating element. Inhaled air is typically passed through this heated chamber to become humidified before it enters the patient. Ideally, the inspiratory limb of the circuit contains a heated wire to preserve the heat and humidification and to keep excess water from condensing and pooling in the circuit.
  • These systems require power, a supply chain for sterile or distilled water, and additional disposable tubing.

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  • It depends on the device setup. Ventilators may require ‘external’ filters (viral, HME, and fan, as well as air intake filters for turbine or compressor ventilators) and internal filters (oxygen inlet filter). Filters can provide three kinds of functions: 
    1. Filtering particulate matter
      • HEPA (high-efficiency particulate air) filters rated to 3 microns are generally considered ‘acceptable’ for bacterial and viral filtration. The term HEPA refers to the efficiency of capturing particles with a MPPS (most penetrating particle size) diameter of 0.3 microns.
      • Of note, machines that accept 50psi/4bar gas intake usually have internal bronze sintered filters to protect the machine from contaminated gas sources. On occasion additional external filters on the high pressure gas lines are required to prevent damage to the device.
    2. Preserving heat and moisture
      • Heat and Moisture Exchangers (HME) are commonly rated to 3 microns, the HEPA standard (and may be referred to as HME filters), but may not be.
      • Hygroscopic Condenser Humidifiers (HCH) are functionally the same as HMEs (though have a slightly different mechanism).
      • HMEs may be referred to as type I (adult) and type II (pediatricss), which differ in deadspace and functional tidal volume range.
      • Unless specifically designated as having capacity for ‘filtration’ (HMEF), HMEs do not provide adequate filtration of bacteria and viruses.
    3. Filtering bacteria and viruses
      • Bacterial/viral (B/V) filters are defined by the ability to filter particles with a diameter size of 3 microns though may be rated to particles as small as 0.2 microns, and do not necessarily provide heat/moisture preservation.
      • The minimum viral filtration efficiency (VFE) that is needed to ensure SARS COV-2 virus can not pass from the patient to the room or machine is unknown.
      • B/V filters with 99.97% ASTM efficiency or filters with >95% efficiency for MPPS of 0.3 microns may be recommended to prevent SARS-CoV-2 viral transmission though data and standards continue to evolve.
      • Diameter for SARS-CoV-2 virion is ~0.06-0.14 microns, hepatitis C is 0.03 microns and Staph aureus is 1 micron.

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  • Filters may be placed at the air intake, inspiratory limb, patient Wye, expiratory limb and/or exhaust port, however, placement at each of these sites does not provide equivalent function.  (Video of filter placement location)
  • Ideally a two filter setup should be used (Anesthesia Patient Safety Foundation):  
    • Inspiratory/Patient filter: the first filter should be placed between the circuit Wye connector and the patient and achieves two things: 1) protects the ventilator and the room from exhaled gases from an infected patient, 2) protects a non-infected patient from a possibly contaminated ventilator. If using an active heat and humidification system, then this should be a bacterial viral filter (not an HME). If not using active heat and humidification, then this should be an HMEF or a bacterial viral filter in series with an HME (HME should be between endotracheal tube and B/V filter). In a dual-limb ICU ventilator, the inspiratory bacterial viral filter may be placed on the inspiratory limb at the takeoff from the ventilator.
    • Expiratory filter: A second bacterial viral filter is recommended on the exhalation limb before the exhalation valve, to protect the room environment and healthcare staff from stray particles (and to protect the device in a dual limb circuit setup).    
  • Placement of filters between the circuit Wye and the patient’s endotracheal tube can add significant deadspace to the circuit, especially for pediatric patients.

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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

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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. 

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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

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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)

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The air intake on the Zoll ventilator is designed to be fitted with anti-bacterial/anti-viral filters. The LTV-1200 series and PB560 ventilators do not. Please consult the manufacturers’ websites for the most current information.

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  • 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 oftenThe 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

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Always reference the manufacturer’s recommendations. Generally wipe down the controls and external case of the equipment with a compatible disinfectant (e.g. sodium hypochlorite solution of 0.05% or 500 ppm for non-metal surfaces).  (WHO 2014)

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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.

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The service manual is available to certified/trained service partners. Of note, to perform a PM for the vent an external service tool (called RCS) is required.

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  • Not all ventilators are designed to function well at high altitude. Piston ventilators don’t have to compensate for altitude as the volume of the piston is constant regardless of the altitude.  It is blower based devices that rely on the control and measurement of tidal volume, which are impacted by changes in gas density.
  • Most ventilators can be calibrated at the factory to a given altitude – so if you know you are going to use it at 4600m – you can have it calibrated to that specific altitude.
  • A manufacturer may say ‘our ventilator compensates for altitude up to 10,000 feet.’ What this often means is that because of loss of compressible volume in the circuit – the set VT of 400 is only 360 ml, and when you go to altitude at 10,000 feet the tidal volume increases to 440 (80 ml or 20%) but it is still +/1 10% of the set VT and therefore meets the ASTM standard. That is not true compensation
  • One additional consideration is oxygen partial pressure delivered. At sea level, assuming normal ventilation (i.e. normal CO2), 50% FiO2 corresponds to an alveolar partial pressure of oxygen of ~300 mmHg; at 15,000 feet (4500m) delivery of 50% FiO2 corresponds to an alveolar partial pressure of oxygen of ~140 mmHg

(Tourtier et al, Trauma and Acute Care Surgery,  2010)(Rodriquez et al, Trauma and Acute Care Surgery, 2009)(Blakeman et al, Trauma and Acute Care Surgery, 2014)

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  • Hypoxemia is frequently defined as an arterial partial pressure of oxygen (PaO2) < 60 mmHg. 
  • Clinicians frequently use pulse oximeter oxygen saturation measurements (SpO2) of <90-94% to diagnose and initiate therapy for hypoxemia
  • There is variability in recommendations for SpO2 goals (ranging from >88 to >94%) in the management of respiratory failure patients. There are multiple trials ongoing to elucidate the optimal strategy. SpO2 goals may have significant implications on oxygen consumption. 

See chapter 6 of the WHO Severe Acute Respiratory Infection Toolkit for oxygen therapy initiation algorithms; see WFSA ANZCA Wall Chart

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