Backup Emergency Ventilator Substitute (BEVS)
Single mode of service: Machine Control, Volume Control device
Leverages a manual “Positive Pressure Ventilation” device – Ambu bag
- Leverages a sterile, hospital provided, “Patient Circuit” of the Oxygen (O2) line, Ambu Bag, and Intubation Tube
- Settings of the device include Respiratory Rate (RR) and Vt (Tidal Volume)
- RR: Set by adjusting the input voltage on the motor
- Vt : Set by adjusting the cam lobes on the rotating shaft. Secondary course mechanism by including “shims” (blocks of wood) under the Ambu bag
- Hospital Provides: O2 source to set FiO2 (Fraction of Inspired Oxygen or oxygen concentration), Patient Circuit (O2, Ambu Bag, Intubation Tube)
- Assumptions: Most basic unit to begin with, adding features on top as reasonable:
- PEEP valve provided from Ambu Bag or Intubation Tube
- Exhale (Expiratory Cycle) gasses (CO2 ) currently vented to atmosphere – filtering virus addressed in “Upgrade” section. This means, without a proper filter, exposure is similar to a patient breathing/coughing without isolation
- Proper usage should include a redundant device on standby should the device fail in any way. Manually respirate the patient until the new device is switched on.
- Ambu bags are fairly consistently sized for adults – 1300mL (275x135mmm/10.8×5.3″), 1475mL (295x127mm/11.6×5″)
- RR: The device should target 8 – 40, however the typical breaths per minute in an ave adult 12-20, so it has to cover this range
- This site mentions 6-8mL/kg of body weight (https://www.sciencedirect.com/topics/medicine-and-dentistry/tidal-volume)
- 100lbs/45kg person = 270-360mL, 150lbs/68kg person = 408-544, 200lbs/90kg = 540-720mL
- 200–800mL (6.8-27oz or 0.9-3.4cups)
Ventilator Mode: Machine Control – this means that the machine (Beverly) is controlling the breathing of the patient. Meaning, if the patient is breathing on their own, this is likely not the right machine for them. Consult with your healthcare professional.
Ventilator Mode: Volume Control Device – this means that the machine (Beverly) is controlling the volume injected into the patient. Meaning, be very careful to understand how much their lung capacity is and adjust the machine accordingly. Consult with your healthcare professional.
- Patient Circuit: The portion of the device interacting with the patient, includes the Oxygen (O2) line, Ambu Bag, and Intubation Tube
RR (Respiratory Rate): Also seen as ‘f’ (frequency) or ‘bpm’ (breaths per minute) is the number of breaths in one minute of operation
Vt (Tidal Volume): Lung volume based on a breath
I:E ratio: Inspiratory-to-Expiratory ratio. Meaning the time the lungs are filling (inspiration) vs emptying (expiration).
- FiO2 (Fraction of Inspired Oxygen or oxygen concentration): The percentage or concentration of oxygen that a person inhales.
PEEP (Positive End Expiratory Pressure): The amount of pressure kept in the lungs on the expiration cycle to help prevent cyclic opening and collapsing alveoli. This helps to keep the lungs oxygenated.
Incentive Spirometer: Prevents lung atrophy. Device that measures how deeply you can inhale (breathe in). It helps you take slow, deep breaths to expand and fill your lungs with air. This helps prevent lung problems, such as pneumonia. When you’re bedridden, ill, or recovering from surgery this tool helps to exercises your lungs and fight off pneumonia by keeping them strong and from filling with liquid
Filtration of viral components on Exhale (Expiratory Cycle) – potentially leveraging water seal
- Power loss, O2 supply, Pressure (too low, too high), RR (within range), Vt (within range), Filters (cleanliness), Remote alerting
- Maximum pressure (40cmH2O), Plateau pressure (30cmH2O), PEEP (5-15cmH2O)
- Consider at-home supply of Oxygen – Oxygen concentrator
Consider at-home connection – can this leverage a mask as an interim solution?
Keep people off a ventilator:
- Leverage an Incentive Spirometer (re: Nebraska Medicine)
- All Covid-19 patients who die are getting pneumonia, but that additional complication is putting additional stress on other elements –
- EX: weak heart, pneumonia putts strain on the heart and the heart eventually fails.
Assist Detection Pressure – detect patient breathing
|03/26/2020||Viability: research, interview professional contacts (medical, engineer, marketing, etc.)|
|03/26/2020||Business: Register business, name, social media handles, etc.|
|03/27/2020||Device design begin|
|(04/13/2020)||FDA Contact- schedule meeting/submit request|
|(04/13/2020)||Public Launch- website, maker sign ups, donor sign ups, PR release *We are doing this here because your support will show the FDA our potential impact. If they approve our design and you make the ventilators, they will not run out!|
|(04/20/2020)||Hospital contact, sign ups|
|ongoing||Repeat until need is met.|
CNC CAM Files:
We used the X-Carve to cut the CAM and Axis fittings. However, you can use a Coping Saw, Jigsaw, or Scroll Saw and drill in order to cut it as well.
Design and BOM:
The BOM and all housing designs and dimensions. Simply print out the design sheets and trace them out!
- The design of this devices is based off of an ambubag of approximately 1600mL (measured using water)
- Depression of one lobe: approximately 1350mL (expels 250mL)
- Depression of both lobes: approximately 1100mL (expels 500mL)
- Informs a depression distance of 1.5″-4.0″ cam specs
- Alternate sized ambubags may require heightend axes and flap (for larger bags) or shims under the bag (for smaller bags)
Breath and Cam
- “I:E Ratio” or “Inspiratory:Expiratory Ratio” indicating the timeframe of inspiration of air into the lungs vs. the time of expiration out of the lungs.
- A rate of 1:1 means 1/2 inspiration and 1/2 expiration
- A rate of 1:2 means 1/3 inspiration and 1/3 expiration
- A rate of 1:3 means 1/4 inspiration and 1/4 expiration
- A rate of 1:4 means 1/5 inspiration and 4/5 expiration
- The breathing slope reflected below is represented linearly.
The Matlab script to generate the below Breath and Cam drawings is included in the below download:
- I:E Ratio of 1:1
- I:E Ratio of 1:2
- I:E Ratio of 1:3
- I:E Ratio of 1:4
The sign up is targeted for US distribution and will be updated pending FDA approval.
The tools and supplies are listed under the information for each ventilator. For the US, when we have a specific one approved by the FDA, we will post it.
We are using the donations to buy supplies and possibly operations if demand continues and/or increases. All personnel are currently volunteers. When the pandemic ends we will donate anything left over. Donations to GiveOxygen are currently not tax-deductible.