Building The Next Generation of VO2 Masks

In the ear­ly spring of 2023, I began inves­ti­gat­ing build­ing my own VO2 mask as an ama­teur ath­lete and pro­fes­sion­al tech enthu­si­ast. I stum­bled upon direc­tions to build one, which you can view here.

Accord­ing to the orig­i­nal design­er, “The out­put includes con­tin­u­ous out­put of VO2, calo­ries con­sumed, vol­umes of expired gas, as well as per­form­ing such func­tions as Basal Meta­bol­ic Rate.”

The device looked like it would work, so I ordered the parts, print­ed them in the GK 3D print­er and put it all togeth­er. I was dis­sat­is­fied with the results.

The ven­ti­la­tion tube threads were weak, and there was no VCO2 option or pres­sure option (for cor­rect­ing for alti­tude.) It was a lit­tle bulky for some of the exer­cis­es an ath­lete would do in the nor­mal course of work­ing out (pull ups, almost any­thing with a bar in the ante­ri­or plane), and from my expe­ri­ence was more an exer­cise in what could be than a great work­ing mask. 

How­ev­er, it was a superb start. It allowed for cal­i­bra­tion against local air, and the bat­tery life was good for at least 3 hours with read­ings every 5 sec­onds, about 2,160 readings.

The orig­i­nal design­er had got­ten it to work well enough to out­put accu­rate data as mea­sured against a lab unit, so I knew it was possible.

“We test­ed the device in a phys­i­ol­o­gy lab against a $60,000 machine and found it gave the about the same results.”

Rab­bit­creek, Instructables

They had also inte­grat­ed it with Zwift, a pop­u­lar bik­ing app, and to an iOS app called Sensirion.

The thing was (is) cool, but I thought there’s plen­ty of room for cre­ative improvement.

Before we go deep­er, I’ll give a lit­tle back­ground for read­ers new to the GK blog. I’m active in the out­doors and tech-savvy enough to fol­low instruc­tions, add some prob­lem solv­ing, and either deploy or improve geeky projects. Along with a group of like-mind­ed geeks, I’ve worked in the Arduino and Plat­formio worlds to build projects track­ing WiFi and Blue­tooth users and devel­oped a soil mois­ture sen­sor hous­ing

We’ve also devel­oped a radio bridge that moved data from rtl_433 to a pub­lic LoRaWAN.

On the phys­i­cal side, I’ve run long dis­tances, lift­ed heavy weights, flown paraglid­ers, and par­tic­i­pat­ed in a bunch of sports, most­ly endurance relat­ed. I’ve pad­dled the Catali­na Clas­sic (32 mile open ocean pad­dle), was an ath­lete in the very first Cross­Fit Games, run Leadville, and a mil­lion years ago rep­re­sent­ed the USA in inter­na­tion­al com­pe­ti­tion as a Naval Pen­tathlon ath­lete (came in 5th on both of the swims.) I’ve used com­mer­cial prod­ucts like Oura rings, wear­able force plates, stride ana­lyz­ers, and heart rate monitors. 

I’ve also been a sol­dier, with all the usu­al expe­ri­ences there; long march­es, heavy back­packs, jump­ing out of planes, div­ing under­wa­ter, lots of guns and explo­sives. Basi­cal­ly, most of the things in the brochure.

All of that is to say I thought of myself as an excel­lent user for a VO2 mask; some­one who could build it, use it, and improve it. I looked around at the options, and they all face two big problems:

First, they’re super expen­sive. The VO2 Mas­ter is prob­a­bly the clos­est thing out there to what I’d want. It’s a very cool piece of kit but at $6k a unit it ain’t going main­stream, and as of this writ­ing it did­n’t have the abil­i­ty to mea­sure VCO2, which is incred­i­bly impor­tant if you want to get the max­i­mum val­ue out of the uncom­fort of putting a mask on your face while you work out.

We’ll take a very short diver­sion here into what VO2 and VCO2 are, and why they matter.

First, the obvi­ous thing: VO2. It’s stands for Vol­ume of Oxy­gen, and a mea­sure of the oxy­gen in your exhaled breath. If you can do that accu­rate­ly enough, and you know how much oxy­gen is in the air around you (from cal­i­brat­ing before you put the mask on) then you know how much oxy­gen you’re using.

Very sim­ply, the more oxy­gen you can con­sume, the more meta­bol­i­cal­ly fit you are. 

VO2 mea­sure­ments for the most part are only used for elite and pret­ty good ath­letes to show off at par­ties, most­ly because it’s so damn dif­fi­cult to get read­ings fre­quent­ly enough to inform your train­ing. You go to a lab, strap on a mask attached to a hose attached to a “met cart” (meta­bol­ic cart), and then a tech­ni­cian makes you work hard­er and hard­er on a bike, tread­mill, or if you’re fan­cy, a row­er until you decide you’ve had enough. 

The tech goes through your read­ings with you, explains what they mean, and typ­i­cal­ly sug­gests what you might do to improve. It’s very cool, but it’s a cum­ber­some met­ric to obtain.

I’m NOT say­ing it’s not a legit­i­mate mark­er, I’m just say­ing that because it’s so dif­fi­cult to get read­ings, it’s not real­ly that prac­ti­cal to care about your VO2.

In a per­fect world, you’d want to see VO2 (and VCO2, more on that in a minute) as eas­i­ly as you see your heart rate. That way you can tell if the work­outs (“inter­ven­tions” in lab-speak) are working.

Ok, so what about VCO2? That’s the Vol­ume of Car­bon Diox­ide you exhale. If you know how much car­bon diox­ide you pro­duce AND how much oxy­gen you con­sume, you can math a lit­tle and fig­ure out how many calo­ries you’re burn­ing, and if those calo­ries are com­ing from burn­ing fat or carbs. 

With­out going into why some­one might want to know that, I’ll just drop this: A device that can show you VO2 and VCO2 accu­rate­ly, in real time, in the field (mean­ing you can wear the thing any­where, not just be hooked up with a plas­tic octo­pus on your face in a lab) does­n’t cur­rent­ly exist on the market.

DIY ver­sions like the one I built do exist, but they ain’t ready for prime time. That brings us back to where we are now: Build­ing a VO2/VCO2 mask ready for the market. 

That’s what I’m work­ing on now, and it is very like­ly that’s why you’re read­ing this; you’re try­ing to fig­ure out what the heck Gris­tle King Inc is and why I asked you for help with build­ing a mask. Now you know. 

My goal is to build a mask that 

• retails for less than $600
• accu­rate­ly reads VO2 and VCO2 in real time
• trans­mits short and long distances
• has a dis­play mech­a­nism for that data (app, watch, tablet, etc)
• is com­fort­able enough to wear that an ath­lete seri­ous about mon­i­tor­ing it can tol­er­ate it for hours 
• easy enough to use that you don’t need much more than the tech­ni­cal abil­i­ty to put togeth­er an Ikea cabinet.

That’s the deal. If you can help, I’d love to hear from you.