Apr 9, 2020
ED-intensivist Scott Weingart
has developed several protocols for airway management in COVID-19
patients, but each of those answers brings up more questions. In
this episode: ‘happy hypoxemia’, the 4 types of COVID patients,
Covid L vs H, is there a role for ECMO in severe disease, why
intubation should be a last resort, the importance of patient
positioning, and much more.
One of the most astounding things about treating
COVID-19 patients is how well they can look with extreme
- Patients with saturations of 50% (and
consistent ABGs) can be talking, mentating normally, and have
otherwise normal vital signs. Thus, this term: “the happy
- It is
not well understood why these patients are able to tolerate such
low sats without having compensatory measures, such as
led to a paradigm shift in the approach to managing
There are 4 types of COVID-19 patients:
- Those with mild
disease -- may never
enter the medical system.
hypoxemics” -- many
of these, if managed well, will be discharged without experiencing
cytokine storm or needing intubation.
- The hyperacute progression
patients -- these patients
decompensate rapidly. Many go into cardiac arrest hours after ED
arrival. Weingart believes these patients likely have the highest
viral load and are the most dangerous to the healthcare
- The indolent patients
-- may look like the “happy
hypoxemics” initially, but within 4-5 days develop cytokine storm
and require intubation.
- When ventilated, there are 2
COVID L (low elastance/not stiff/normal compliance)
- This is the “happy hypoxemic” phase
on the vent.
- The amount of gas in the lungs is
nearly normal and there is low lung recruitability.
- Easy to ventilate.
- These patients can be damaged
iatrogenically if you respond to their pulse ox with standard vent
- Best managed with high FiO2 which
allows you to limit the PEEP to just what you need.
- Recommended initial vent
ml/kg TV, 100% FiO2
- Increase the PEEP only if the patient is
desaturating on a high FiO2.
- Can turn into COVID H patients on the
COVID H (high elastance/stiff/low compliance)
- Increased permeability of the lung
leads to edema, atelectasis, decreased gas volume, and decreased TV
for a given inspiratory pressure.
degree of lung recruitability.
- Manifests similar to ARDS patients and responds
nicely to typical ARDS settings.
ARDSNet ladder applies only to this subset of COVID
Link to ARDSNet
How can you tell if a patient is COVID L or COVID
- Observe their plateau and driving pressures
when on 8 ml/kg TV.
L patients will respond like normal lungs.
H patients will respond with high plateau and driving pressures,
indicating terrible compliance and classic acute lung
What is the current treatment algorithm for the query
COVID patient who presents with a severe asthma
Use MDIs rather than nebulization to deliver
- Consider terbutaline or
epinephrine (0.3-0.5 mg IM).
- Many hospitals are not allowing
CPAP, so more of these patients may need to be intubated if they
with 8 ml/kg TV and high FiO2.
- Follow the expired flow graph to make sure the
respiratory rate is low enough to allow the patient to fully expire
- Link to EMCrit Dominating the Ventilator Part 2 on
Which techniques can be used to minimize the
aerosolization risk of intubation?
- Weingart argues that if you
procedure for intubation, the
risk is very low.
- Important measures
- wearing full PPE,
a negative pressure room if you can,
intubating while the patient is getting chest
- attaching viral filters to occlusive face
- avoiding bag-valve-mask
- keeping the face mask on the patient until
- releasing any pressure from the face mask
video laryngoscopy rather than DL,
- avoiding suctioning when you can,
- consider single operator bougie intubation
- Link to video demonstration of Dr. Chris Holmes’
Intubation Shield which seems ergonomically superior to other
aerosol containment boxes in use.
Does ECMO have a role for these patients?
Most centers are reserving ECMO for patients who only have single
- For patients with only
pulmonary failure, this would be veno-venous (VV) ECMO.
- For those who have recovered
from their lung issues but who have COVID myocarditis, they might
get veno-arterial (VA) ECMO.
- Many COVID patients have
multi-system organ failure and are being excluded from
- Old age has been another common
COVID ECMO exclusion.
COVID fluid management: keep them dry, but not too
Replace insensible and external losses (ie. due to vomiting or
Patients who you suspect are dehydrated based on history or a flat
IVC on ultrasound may benefit from 500-1000 ml of
- ED patients who you have no
reason to believe are dehydrated likely need no additional fluid
- In general, it is better to run
these patients dry, but monitor urine output and your ultrasound
findings to make sure the patient doesn’t develop renal failure due
- Consider early pressors if
COVID patients are hypotensive.
Non-invasive ventilation, done right, should be
Initially, people were worried about aerosolization and cautioned
against it. This is because standard noninvasive used masks which
vent to the environment.
- Weingart argues that the
Italian helmets and his closed circuit CPAP masks have minimal
dispersal and are much safer.
How is Weingart awake repositioning patients in the
He’s repositioning everyone every 60 minutes by asking them to
rotate from lying on their left side, to their right side, and then
- Prone positioning is an option,
but you need to verify it makes the patient feel better, not
- Complex if a patient is on CPAP (even more so
if a patient is intubated).
not appear to benefit COVID H patients.
What is being done during the apneic period, prior to
Weingart uses the CPAP set-up which allows for apneic CPAP.
- Keeps the lungs inflated with a
continuous source of oxygen, providing a high FiO2 and maintains
Link to EMCrit’s COVID CPAP
Pre-oxygenation Set-up without nasal cannula
Link to EMCrit’s COVID-19
Intubation Pack and Preox for Intubation
- Video demonstrating that apneic CPAP inflates
When COVID patients need supplemental oxygen, Weingart
uses a stepwise progression.
- 1st tier -- normal nasal
cannula @ 6 liter/minute
- 2nd tier -- Venturi mask up to
- 3rd tier -- nasal cannula plus
non-rebreather mask covered with a surgical mask
- 4th tier -- high flow nasal cannula
- 5th tier -- CPAP (using a
machine that’s been altered to allow filtering)
Weingart likes to keep his COVID L patients lightly sedated,
arguing that spontaneous breathing is good for their
- Deep sedation is preferred by
some to prevent self-extubations when patient monitoring is
Weingart is concerned about the deep sedation/paralysis required
when intubated patients share vents.
- What he finds more attractive
is splitting the vents between 2-4 patients to deliver CPAP,
allowing the patients to spontaneously breathe. This saves the
single ICU vents for patients who need individualized
- Gattinoni L. et al.
COVID-19 pneumonia: different
respiratory treatment for different phenotypes?
(2020) Intensive Care Medicine;
- Link to EMCrit’s COVID Airway Management
Link to EMCrit’s COVID CPAP Pre-oxygenation Set-up
without nasal cannula
Link to EMCrit’s COVID-19 Intubation Pack and Preox
- Link to EMCrit Dominating the Ventilator Part 2 on
Link to EMCrit Wee Alternatives to Vent