The following is a tutorial on basic airway pressure release ventilation (APRV) setup and troubleshooting.  Over the next few days, I’ll update with video showing how to setup both  the VELA and Draeger ventilators.

There are multiple theoretical advantages of APRV over conventional ventilator strategies (see review articles below) however some of the benefits specific to the COVID-19 patient population is the prevention of derecruitment and encouragement of spontaneous breathing with consequent decreased need for deep analgosedation.  While APRV can be set up directly in the newly intubated patient, it is perhaps easier to transition from more a more familiar conventional modality such as ACVC.

1.  After RSI, place pt on ACVC utilizing low tidal ventilation strategy per ARDSnet protocol. Initiate analgesia and sedation strategy.
2. Once PEEP has been titrated per ARDSnet PEEP/O2 tables, paralysis has worn off and the patient is spontaneously breathing, consider transition to APRV
3. Set Pressure high (Phigh). While still on ACVC, perform inspiratory hold and measure Plateau Pressure.  The plateau pressure will be your starting  Phigh in APRV.  Values are typically between 20-35 cmH20
4. Set Time high (Thigh) between 4-6s.  Longer Thigh will increase oxygenation
5. Set Pressure low (Plow) to 0* (see discussion below)
6. Set Time low (Tlow).  APRV relies on autopeep(iPEEP) to prevent derecruitment of alveoli, therefore your release time or Tlow is critical.  The longer the Tlow, the lower the iPEEP and the greater the likelihood of alveolar collapse.  In order to adjust Tlow we need to observe the patients expiratory flow waveform on the ventilator, targeting >50% T-PEFR (see below).  This will typically be between 0.2-0.8s in restrictive lung disease and 0.8-1.5s in obstructive lung disease.  The shorter the Tlow, the greater the mean airway pressure which will generally increase oxygenation.
7. Spontaneous Breathing is crucial in APRV.  Add pressure support of 5 (on VELA) or automatic tube compensation (on Draeger or Puritan Bennett) to help augment the patients own respiratory efforts which will assist in ventilation.
8. Troubleshooting Hypoxemia.  Overall, to improve oxygenation we need to increase mean airway pressure and/or recruit atelectatic alveoli.  Assuming your FiO2 is already 100%, consider the following steps:
   1. shorten Tlow up to T-PEFR 75%
   2. increase Phigh and Thigh simultaneously.  Phigh >35 may be required in the morbidly obese
9. Troubleshooting Hypercapnia.  Mild hypercapnia without severe acidemia can be tolerated in these patients.  Optimizing ventilation should be performed cautiously in a way that does not compromise oxygenation.
   1. Lighten sedation to encourage spontaneous ventilation.
   2. Increase Phigh and Thigh simultaneously.
   3. Lengthen Tlow by 0.05-1s increments up to 50% T-PEFR.  (while this will increase tidal volumes during release, this will also decrease mean airway pressure and likely worsen oxygenation)
   4. Increase Phigh while decreasing Thigh (not recommended).  while this will increase minute ventilation, it will also decrease mean airway pressure and worsen oxygenation.

Below is the table from the Habashi review article which details setup as well as troubleshooting. I highly encourage everyone to read the review prior to your first attempts using APRV.

T-PEFR – ventilator flow waveform (resusreview.com)

Great Review article by Nader Habashi on APRV

Alternative approach to Tlow/Plow settings*. (skip this part until comfortable with Habashi method) An alternative strategy for APRV has been proposed by Zhou et al.  The Zhou method is notably different in their approach to determining Tlow which is determined by starting with a Tlow of ~1s, multiplied by the time constant (resistance*compliance) and then targeting T-PEFR >50%.  In addition, Zhou also utilizes a starting Plow of 5 cmH20, while Habashi recommends Plow of 0.  Many pulmonary physiologists criticize APRV because it relies on autoPEEP(iPEEP) to prevent derecruitment of alveoli.   iPEEP does not uniformly affect the lung.  iPEEP will recruit healthy alveoli with increased compliance preferentially over diseased low compliant alveoli which could potentially worsen atelectatrauma.  With that in mind,  per the starling resistor model extrinsic PEEP and iPEEP are not additive unless extrinsic PEEP exceeds iPEEP.  Adding additional extrinsic PEEP with the ventilator (eg. Plow 5 cmH20) would likely not affect healthy alveoli already stented by iPEEP  but may prevent the full derecruitment of diseased/low compliance/stiff alveoli.  Adding Plow may prolong the release time necessary to reach T-PEFR 50-75%.

Below is Zhou’s alternative APRV initiation and titration strategy taken from their study protocol.  Of note, Zhou utilized Puritan Bennett ventilators (like our 840s) which likely explains some of the differences in initiation/setup.  While 840s can be used to provide APRV, the setup is less straight forward than on the VELAs and Draegers.

More recent review article summarizing trials as well as reviewing alternative strategy by Zhou.

another site with tutorial based on Habashi APRV strategy

https://resusreview.com/2013/aprv-ventilation-mode-introduction-basic-use-management-and-advanced-tips/

Any questions about setting this up? Grab me while I’m working clinically and I’ll walk you through it or call me anytime with questions 917-749-1004.

Some suggestions in terms of workflow for airway management.

The following  in an ongoing collaboration with Nick Caputo at Lincoln as we are attempting to develop a unified approach between sites to allow us all to learn from one another’s success and mistakes.  Check back frequently for updates as our supplies and what we know about the disease changes.

Ventilator shortage.  The hospital is facing a significant ventilator shortage.  In addition to our 7 VELA ventilators, there are 3 transport ventilators in radiology and 11 anesthesia machines in the OR.  1 transport ventilator should remain in radiology for use with patients requiring CT.  If OR ventilators are required, contact anesthesia for assistance in initial setup and questions.

We have 50 emergency transport ventilators with extremely limited capabilities.  Specifically, they are asynchronous and provide a maximum PEEP of 5cmH20 which makes them of limited value in the setting of severe ARDS.   The devices are a bit tricky to use, so look over the following visual guide and watch the video beforehand.  There is a ventilator in the admin office connected to a test lung and O2 cannister to practice with.

Dual Ventilation Strategy

Dual ventilation strategy should only be considered as a last resort.  If attempting to do so, the following protocol may improve safety.

Non-invasive ventilation. In light of impending ventilator shortage, it is prudent that we avoid any unnecessary intubation.  If clinical history suggests that there may be a reversible component of failure (eg. CHF, asthma) then it may be reasonable to attempt at short trial of NIV.  A few guidelines for NIV:

-NIV should only be attempted with our closed circuit ventilators with a non-vented facemask.  The single limb dedicated BiPAP machines have a vent in the mask which will aerosolize droplets into the room when the patient exhales
-Attach HEPA filter at the mask prior to Y connection of the tubing
-Place patient in isolation tent
-Ensure tight mask fit prior to initiation of ventilation
-If albuterol administration required, administer via MDI adapter or aerogen nebulizer as pictured below

Any questions don’t hesitate to contact me anytime.  text/call 917-749-1004.

To minimize potential aerosolization during administration of albuterol we are trying to utilize MDIs primarily.  For intubated patients or those requiring NIV you can administer albuterol MDIs via inline adapter.  Alternatively, the aerogen device also minimizes leak compared to the typical acorn nebulizers but it’s effect on droplet dispersal is unknown.

in-line MDI adapters and aerogen nebulizers are located on the respiratory cart behind the cardiac workstation, located on the same shelf as the VL blades.

Thank to Suzi Bentley for putting together the visual guide.

Below are updated resources for the management of sexual assault survivors.  Permanent links to the documents can also be found under the guidelines tab.

Sexual assault checklist

Sexual-Assault-Checklist

HIV PEP follow up information

HIV PEP Follow-up Information

HIV PEP starter pack information

HIV PEP Starter Pack Information

Tip sheet for ordering HIV PEP

Tip Sheet for Ordering HIV PEP

FRE form

FRE Form

SART bill of rights

SART BIll of Rights (1)