– Treatment of Hypoxia and Respiratory Failure
– – NIV and HFNC
– – Intubation
– – – Airway Assessment
– – – Maximise 1st pass success
– – – Drugs
– – – Preoxygenation
– – – Re-oxygenation
– – – Apnoeic Oxygenation
This forms one section of our COVID-19 Emergency Department Assessment & Management Guideline
There are a number of alterations to the usual peri-intubation process that need to be made in order to minimise the risk of infection to attending staff. While there remains some resistance to the routine use of intubation checklists in EDs, as COVID-19 intubations represent a significant deviation from routine practice with high risks to staff, the use of a purpose designed COVID-19 intubation checklist should be considered mandatory in every department. Additionally, frequent and repeated simulation is recommended for staff training for what is a complex, unfamiliar and high stress clinical scenario.
Given the added complexity of the peri-intubation process and the need for the intubation team to carefully don PPE, the pre-intubation preparation period can take significant time. Consequently decisions regarding intubation need to be made early, as the team will not be able to safely intervene to intubate a crashing patient.
The peri-intubation process is high risk for aerosol generation. PPE appropriate for AGPs is required by all staff in the room and some centres use additional precautions (see PPE for “highest risk” AGPs), especially for the intubator at the highest risk. If practical and available use a single room, ideally a negative pressure room. Limit staff present at tracheal intubation to one intubator, one airway assistant and one to team lead/administer drugs/monitor patient (COVID-19 AMP) together with 1-2 “runners” positioned immediately outside the room, to provide additional assistance if and when required. Where an “ante room” exists connected to a negative pressure room used for intubation, ideally 1 “door” runner” (“dirty runner”) should be stationed within this also wearing PPE appropriate for AGPs, while an “outside room” runner (“clean runner”) stands outside of the ante room to source equipment and drugs that are unexpectedly needed and pass them to the “door runner”.
There is a balance between bringing into the room as much equipment that is most likely required for intubation safety and needing to minimise the amount of equipment that is contaminated by entering the room that will need to be either cleaned or discarded post intubation. Consequently backup safety equipment that has a low chance of being used, like a hyper-angulated video laryngoscope blade or cricothyrotomy equipment, may be best left outside the room in the “clean” area but still readily available if called for.
It is critical that departments ensure that all viral filters used for NIV or the peri-intubation period are rated as high efficiency viral/bacterial filters with >99.9% filtration. Viral filters can be stand alone filters or can be HME (Heat Moisture Exchange) filters with high efficiency viral filtration properties. However some HME filters do not have these required properties so this must be confirmed before stocking in critical care areas.
A standard ED airway assessment should be performed as permitted by patient clinical state and performed from as distant a position from the patient as possible. However awake intubation for predicted difficult intubation is not advisable due to high risk of disease spread. If difficult intubation is predicted, consider alternatives such as “priming” for CICO Rescue (Can’t Intubate, Can’t Oxygenate) prior to delivering pre-intubation sedation/paralysis i.e position person at the patient’s neck fully prepared as per the Vortex CICO status “SET”.
Epicentre anecdotes report a high number of patients with pharyngeal oedema above the cords on intubation with some difficulty passing a flexible bougie and the use of a less flexible stylet type introducer being suggested as an alternative. (EMRAP live 31/3/20)
Maximise 1st pass success
- All standard of care aspects of optimal intubation management should be employed to maximise first pass success.
- Specifically, this should include using the most capable intubator who is readily available to intubate (COVID-19, AMP, ANZICS, SAS) and using video laryngoscopy (VL) (ANZICS, SAS). Additionally VL can allow the intubator to maintain a greater distance from the patient’s mouth to reduce disease spread. (SAS)
Give a high dose paralytic to ensure adequate and rapid paralysis to minimise the length of the apnoeic period and to reduce risk of coughing in the peri-intubation period for staff safety.
There is no consensus on dosing but Suxamethonium 1.5mg-2mg/kg or Rocuronium 1.5mg/kg have been suggested. The standard 1.2mg/kg dose of rocuronium is arguably most appropriate for the rapid sequence intubation of well patients – in unwell patients higher doses have been suggested to absolutely minimise the risk of coughing and ensure rapid paralysis.
Some advocate rocuronium as the preferred choice over suxamethonium as for the former, the lack of muscular fasciculations (with attendant reduced muscular oxygen consumption) may prolong time to desaturations while the longer period of paralysis further reduces the risk of coughing in the peri-intubation period.
In haemodynamically unstable patients ketamine is the sedation drug of choice. However even in the stable patients, ketamine could still be argued to be the preferred agent, for if the patient does not cooperate with preoxygenation, ketamine can be administered prior to intubation as part of a DSI (Delayed Sequence Intubation) approach – dissociative procedural sedation to enable preoxygenation. Even if ketamine is not chosen as the preferred intubating agent, it should be taken into the room to enable DSI if required.
- Most suitable preoxygenation options within ED’s are the Bag Valve Mask (BVM) with PEEP valve or the Mapleson C circuits.
- For most EDs, using a BVM with a PEEP valve is likely to be the most practical and familiar option for the ED provider.
- Regardless of device choice, modifications are required to maximise safety including holding the mask with a 2 handed approach, attaching a viral filter between the mask and the rest of the equipment and avoiding positive pressure ventilations where possible.
- VAPOX protocol (Ventilator Assisted Preoxygenation) has strong theoretical benefits for the intubation of patients who remain hypoxic on NRM but it is not recommended for preoxygenation of COVID-19 patients. For more information click here.
- Minimise the interval between removal of patient’s protective mask and the application of the BVM (or Mapleson) connected face mask with viral filter attached. (SAS)
- A minimum of 5 minutes of preoxygenation is recommended to fully pre-oxygenate the patient.
- Some sources suggest to depressurise the circuit (remove PEEP) during the apnoeic period, prior to removal of the face mask from the patient and before the intubation attempt to reduce the risk of viral dispersal from chest deflation.
Patients who are hypoxic on face mask oxygen are at higher risk of mortality on intubation if they are not optimised prior to intubation. Consequently a preoxygenation device with a low risk of viral dispersal to staff and that can provide PEEP will be required. Additionally for simplicity the same device should generally be used for re-oxygenation (see below) between intubation attempts.
The most suitable options for preoxygenation within ED’s are the Bag Valve Mask (BVM) or Mapleson C circuits. (SAS) For both options, key requirements include:
- Placing a viral filter between the mask and the rest of the equipment
- The viral filter should be applied directly to the face mask as an increased number of connections between the face mask and filter increase the opportunity for disconnection on the patient side. (SAS)
- Monitoring continuous waveform capnography (SAS) by placing a CO2 monitor between viral filter and the rest of the device or (ideally) attaching a CO2 sampling line to the viral filter (if such equipment is available). A triangular rather than a square CO2 trace or a low numerical value can indicate mask leak (SAS) and being pre-attached can remove a task required post intubation before connecting to the ventilator.
- Using a 2 hand grip on the mask to minimise face mask air leak. (SAS)
- Generally avoiding positive pressure manual ventilation during preoxygenation. During the post-paralysis apnoeic period, patients with severe disease may require manual ventilation to prevent profound desaturation. To minimise the risk of aerosolisation of airway secretions, this should be performed as a two person technique, with the airway assistant gently squeezing the bag and adjusting the level of PEEP as required. (SAS)
For most departments, the simplest and most familiar option would be to use the Bag Valve Mask (BVM) as the preoxygenation device with a PEEP valve attached to provide PEEP.
The Mapleson C circuit is an alternative that can deliver PEEP and has the advantage of bag deflation providing an indication of mask leak. However it is generally not widely available or commonly utilised in EDs.
VAPOX protocol (Ventilator Assisted Preoxygenation) has strong theoretical benefits for the intubation of patients who remain hypoxic on NRM. However for COVID-19 there are a number of modifications that need to be made to ensure staff safety that both increase cognitive load in a high stress situation and reduce some of the usual benefits of VAPOX protocol. Consequently it is not recommended for COVID-19 preoxygenation. For more information see the addendum at the end of this post.
Minimise the interval between removal of patient’s protective mask and the application of the BVM or Mapleson connected face mask with viral filter attached. (SAS)
A minimum of 5 minutes of preoxygenation is recommended to fully pre-oxygenate the patient.
At the end of the post-paralysis apnoeic period, when the preoxygenation device is removed from the patient, the deflation of the lungs (that were splinted under the pressure of PEEP) exposes staff to additional risk of viral dispersal. The level of risk this affords is unclear, though some sources recommended to depressurise the circuit during the apnoeic period prior to removal of the preoxygenation device. Examples of how this can be achieved are:
- BVM: Dial PEEP valve to zero or disconnect the PEEP valve
- Mapleson C: Open the APL (adjustable pressure limiting) valve to zero
Disconnecting the BVM bag or the Mapleson C circuit from their connection to the viral filter is another option to depressurise the circuit, but this is not recommended due to the attendant risk of accidental disconnection of the viral filter from the face mask at that time.
Re-oxygenation between failed intubation attempts
Re-oxygenation will be most practically achieved using the same device chosen for the preoxygenation of the patient e.g. if a BVM was chosen for preoxygenation it should be used for re-oxygenation. This should be performed as a 2 person technique with a 2 handed mask grip as described above
Some sources suggest using a Supra-Glottic Airway (SGA) instead of a face mask (i.e. remove the mask from the BVM) for more effective delivery of re-oxygenation with potentially less air leak.(Alfred Guideline) However removal of the SGA for successive attempts at intubation may result in dispersal of viral droplets. Where an SGA is used, use of a second-generation device is recommended as its higher seal pressure during positive pressure ventilation decreases the risk of aerosolisation of virus containing fluid particles. (SAS)
Summary: the balance of risks and benefits favours avoiding the use of nasal cannula for apnoeic oxygenation.
Nasal cannula with oxygen flow at 10-15L/min are generally considered routine peri-intubation care during contemporary ED intubation to extend the safe apnoea period. There is concern regarding potential viral aerosolisation to intubating staff (SAS) though it is unclear how substantial viral aerosolisation would be at these flow rates, particularly given there is dispute about the same for HFNC at far higher flow rates, albeit with staff typically located further away than intubators are.
A further consideration is that in critically ill patients with respiratory failure and shunt physiology requiring PEEP, apnoeic oxygenation may not add additional benefit as suggested by the FELLOW trial (Semler 2016). Consequently balancing possible risks and limited benefits in this population, suggests avoiding the use of apnoeic oxygenation nasal cannula.
Post Intubation Care
- ARDSnet based, high PEEP “lung protective” ventilation was the prevailing recommendation early the pandemic although the recognition of the L & H patient phenotypes (see Oxygenation Overview section) has resulted in an alternative high FiO2, intermediate PEEP (8-10cm H20) strategy recommended for type L patients.
- The ETT cuff should be immediately inflated, prior to any attempts at ventilation post intubation to minimise expired air leak to staff.
- Consider immediate connection to the ventilator post intubation to avoid serial connections/disconnections of equipment as each poses a risk of accidental disconnection and viral dispersal.
- Do not use auscultation of the chest to confirm ETT placement and depth as this increases proximity of the intubator to the patient’s expired air without yet confirmed ETT placement.
- The ETT should always be clamped prior to any planned disconnection.
- Accidental circuit disconnection, particularly during patient transport is a high risk to staff. Consequently special care should be taken to secure points at risk of disconnection post intubation with dressing such a “tegaderm” or tape.
- In-line suction is recommended to be used within the ventilator circuit and this has significant implications for the set up of your viral filters, CO2 monitoring and timing of disconnections of the circuit.
- PPE appropriate for AGPs should be worn by any staff attending an intubated patient at all times.
Ventilator settings: the ARDSnet high PEEP “lung protective” ventilation was the prevailing recommendation early in the pandemic with low tidal volumes (starting at 6ml/kg based on ideal body weight) with high PEEP (using a PEEP-FiO2 table). However since the release of the Gattinoni paper revealing the L and H phenotypes (See Oxygenation Overview section) it is thought that while an appropriate strategy for the H phenotype with high resistance (low compliance, high lung weight and high recruitability, this strategy may have been contributing to alveolar pressure injury and poor outcomes in the L phenotype.
For the L phenotype, a high FiO2, intermediate PEEP (8-10cmH20) strategy has been advocated. Additionally, Gattinoni recommends that “once intubated and deeply sedated, the Type L patients, if hypercapnic, can be ventilated with volumes greater than 6 ml/kg (up to 8-9 ml/kg), as the high compliance results in tolerable strain without the risk of VILI.”
Gattinoni also recommends that while CT scan is the best too to distinguish between Type L and Type H patients, if not available surrogate markers can be used such as respiratory system compliance and recruitability.
The use of a tape measure to determine a patient’s height and calculate ideal body weight to avoid common overestimation of the patient’s weight and resultant excessive tidal volumes, is advocated in the LOV-ED protocol.
The ETT cuff should be immediately inflated, prior to any attempts at ventilation post intubation to minimise expired air leak to staff. (ANZICS, SAS)
For post intubation ventilation, some sources recommend immediate connection of the ventilator to the ETT (via CO2 monitor and viral filter) instead of ventilating with the BVM or Mapleson C in order to reduce the number of connections and disconnections, as each poses a risk of accidental disconnection and viral dispersal.
Confirmation of ETT placement and depth should occur through:
- Visualising passage through the cords
- Alignment of the ETT black vocal cord marker with the vocal cords.
- ETT misting
- End tidal CO2 trace
- Post intubation CXR when appropriate
Specifically, this should not include auscultation of the chest as this increases proximity of the intubator to the patient’s expired air without yet confirmed ETT placement.
The ETT should always be clamped prior to any planned disconnection.
Reports from regions experiencing high volumes of COVID-19 patients, suggest that there is a significant risk of viral dispersal to staff from the accidental disconnection of the ventilator circuit and this risk is highest during transport of the patient out of the ED. Accidental disconnections can occur at any point of the ventilator circuit between:
- Patient and ETT (extubation)
- ETT and viral filter
- Viral filter and in line CO2 monitor (if separate devices)
- In line CO2 monitor and the ventilator tubing
- Ventilator tubing and the ventilator.
Consequently special care should be taken to secure points at risk of disconnection post intubation with dressing such a “tegaderm” or tape.
In-line suction is recommended to be placed in the ventilator circuit. As this can not be provided through the viral filter, the in-line suction device will need to be placed distal to the viral filter. This can be achieved in 1 of 2 ways:
- Planned disconnection of the circuit post intubation (with attendant ETT clamping) between ETT and viral filter post intubation
- The use of a 2nd viral filter that is pre-connected (before intubation) just distal to the ventilator tubing with the in-line suction pre-connected just distal to this. Immediately post intubation, the 1st viral filter will need to be removed before connection of the ETT to the circuit. This approach has implications for the CO2 monitoring device.
- If the CO2 monitoring is provided by attachment of a sampling line to the viral filter side port, this line will simply need to be removed from 1st filter and rapidly attached to 2nd filter post intubation.
- If the CO2 monitoring is provided by an in-line monitoring device:
- This can be left in place and connected directly to the in-line suction on its distal side. The disadvantage of this set up is that the CO2 monitoring device is now distal to the 2nd viral filter which can result in clogging of the sensor with secretions (not removed through suctioning) resulting in further planned disconnections of the circuit. To avoid this, the CO2 monitor would need to be moved proximal to the 2nd viral filter immediately post intubation at the same time as the 1st viral filter is being removed.
- Alternatively the CO2 in line monitor can be pre-connected before intubation proximal to the 2nd filter but this attends a large disadvantage of not being able to use this during preoxygenation and re-oxygenation.
Due to the ever present risk of accidental disconnection of the ventilator circuit, PPE appropriate for AGPs is recommended at all times for staff attending an intubated patient.