A cheap and easy-to-build ventilation system

This is an untried idea which may be of value for emergency ventilation of Covid-19 patients when expensive ventilation systems and specialists for intubation are not available.

The volume of air introduced into the lungs will depend on

1. The size of the bellows (We assume it would be about 30 x 30 cms)
2. The length of stroke from the crank mechanism (we assume it would be about 20 cms)
3. The efficiency of the seal between the plywood arch and the chest and waist of the patient. (We assume it would retain, 60% to 80% of the induced vacuum and pump pressure.)

At these dimensions, the bellows cycle should move up about 9 litres of air every cycle. Even allowing for inefficiencies and throat constrictions, etc., the lungs should have an air flow of approximately 2-3 litres every pump cycle, which we assume would be about every 8 seconds.

The above drawing assumes that some low-speed gear mechanism can be fitted to a crank directly below the bellows. Obviously this will not always be available.

Low speed geared drive mechanism

The main problem we expect in Third World regions will be in obtaining some very high-ratio gear mechanism to drive the pump cycle at this slow speed but with not-inconsiderable force. At only one stroke every 8 seconds it needs to use off-the-shelf A/C electric motors obtained almost everywhere.

One solution, may be this use of an inverted bicycle. The electric motor shaft could easily be fitted with a choice of variable-size wooden hubs (which can be turned up on the motor itself, if no lathe is available).

The hub would then drive the inflated rear wheel of the bicycle by friction. In combination with the bicycle crank-chain/sprocket reductions, this would give low rotational speeds, and higher drive-power through the gear-effect.