The latest blogs and tweets from intensivists state that mechanical ventilation is key for treating patients with ARDS from COVID-19.
In this post, I’ll describe the ARDSNet ventilation protocol, as described in the guidebook manual for doctors at Massachusetts General Hospital. The ARDS network is a research network formed by the National Institute of Health and National Heart, Lung, and Blood Institute to carry out clinical trials for ARDS. http://www.ardsnet.org/
A good introduction to the ARDSNet protocol is seen in the following youtube video: https://www.youtube.com/watch?v=uXKc6gIcp0c.
The typical settings for a mechanical ventilator are seen below: mode, tidal volume, respiratory rate, I:E ratio, Positive End Expiration Pressure (PEEP), and Fraction of Inspired Oxygen (FiO2).
In brief, the goal of mechanical ventilators is to achieve appropriate oxygenation and ventilation with appropriate lung protection. Oxygenation is the delivery of oxygen to the blood which gets sent to the rest of the body. Ventilation refers to the removal of carbon dioxide waste.
In brief, our oxygenation goal is to achieve a PaO2 of 55-80 mmHg and SpO2 of 88-95%. To achieve this goal, we modify FiO2 to increase the amount of oxygen in the air that someone will breathe or increase PEEP to keep the alveoli in the lungs open. Once we are at our oxygenation goal, we titrate according to the following chart.
The Italian experience has been that patients with COVID respond well to FiO2 above 0.9. See http://www.ventilab.org/2020/02/29/ventilazione-meccanica-e-polmonite-da-coronavirus/ for more details. If instead PEE is increased to the highest values, oxygenation in their experience was obtained with an FiO2 of 0.5-0.7.
Ventilation is critical to achieving appropriate acid-base balance in a patient. The goal pH is 7.3 to 7.45 and determined through regular arterial blood gas measurements. To achieve this goal, we modify tidal volume and respiratory rate as described below.
To ventilate without damaging the lung, our tidal volume goal is 6 mL/kg and platea pressure is less than 30.
For more details, I attached below the Massachusetts General Hospital guidebook for treating ARDS.