We have spent the past few days searching for information or guidelines that could assist frontline medical workers in their fight against COVID-19. One of our translators found a tweet linking to a YouTube video and journal article describing how to hook up to four patients to a single ventilator. As we warned in our Imperial model explainer, every COVID-19 patient who needs ventilation but can’t receive it due to shortages in overwhelmed ICU’s will likely die.
Our Philippines Situation Report noted that only one in ten ICU beds in the Philippines have ventilators. We fear the same is true across much of Southeast Asia. What commissioned an illustrator to draw simplified ‘how to’ instructions to translate and distribute to hospitals, summarizing both the journal article and six minute video. What’s described below isn’t a miracle, but a hardware modification that might save a lot of lives in very specific contexts.
UPDATE: this has been vetted by a pulmunologist.
In 2006, Dr’s Greg Nayman and Charlene Babcock Irvin postulated that in times of crisis, one ventilator could be used to successfully intubate up to four patients at once. As hospitals brace for the oncoming flood of Covid 19 patients measures such as this might become necessary in order to save lives until the medical system is able to adapt to our new reality.
Ventilator modification was conceptualized as a way for hospitals without spare ventilators or extra personnel in times of crisis to stretch their existing supply of ventilators. Through the usage of simple materials, one ventilator could intubate two or four patients instead of just one. In their experiment, Nayman and Babcock used a Brigg’s “T-Tube from a respiratory therapists cart used for aerosols”. They cut the bags off and connected several tubes together into two “H” shapes. After creating the “H”’s they connected them to Hudson ventilator tubing with the adapters so that the air from the ventilator was evenly split between the four simulated patients and the returning air all went into the same exhaust port. If these materials are not available, medical staff are encouraged to use what they have on hand and be adaptable.
Their experiment lasted for twelve hours using both pressure control and volume control settings. The ventilator was checked intermittently at random intervals to simulate busy conditions. During the whole of the experiment airway pressures did not exceed the threshold for ventilator induced lung injury. Individual tidal volumes stayed consistently in the area of 471-507 mL, which approximates 7 mL/kg for a 70 kg individual. Studies show that ventilation within 6-8 mL/kg is associated with improved outcome in injured lungs.
In her accompanying video and in the study itself, Dr Babcock made several recommendations to anyone considering ventilator modification:
- Keep patients with similar lung sizes together
- Make sure that the resistance is the same
- Position patients in a “half star” configuration if tubing for all patients is the same length, heads facing the ventilator
These recommendations ensure that patients with similar needs for oxygen are positioned together. If patients with differing needs are placed on the same modified ventilator, there will be no way to ensure that an individual patient gets their appropriate amount of oxygen.
While ventilator modification is theoretically effective, it has only been successfully used on humans once. Dr Kevin Menes instructed staff to use Y-Tubing to modify ventilators to intubate two patients at once in the aftermath of the Las Vegas mass shooting. With his quick thinking he was able to keep the patients alive for hours until outside support could be provided. Due to the limited evidence and experimental usage of the ventilator modification technique, much remains unknown about ventilator modification. Cross contamination risk was not evaluated. Dr. Babcock theorizes that the risk is low because the air flow is a one way circuit, but without further study it is impossible to say for certain.
Ventilators were not designed to be used with more than one patient, ventilator modification should only be considered if existing resources fail to meet demand. To quote Dr. Babcock, “If it was me and I had four patients and they all needed intubation and I only had one ventilator, I would simply have a shared discussion meeting with all four families and say ‘I could pick one to live, or we could try to have all four live.’ But this is clearly off-label and would only be used in a dire circumstance, which we may see with Covid 19”.