Gas Flow Control Kits

The control of the flow of a gas such as Helium is an important part of the successful use of the Hypoxic (low oxygen) method.

The tap provided on commercially available, disposable ‘Balloon Time’ Helium cylinders is not designed to provide such control.

To solve the problem Exit has designed a simple jet gas flow control which replaces the nylon and rubber valve provided with the cylinders (see cylinder fittings and jet above right). In the photo, the replaced nylon and rubber fitting is shown at top; the exposed brass replacement fittings show the coupling to the cylinder, the jet and the tail end for attachment of a plastic hose. The tool used to insert the jet is shown on the bottom of the photo.

The second photo shows the assembled fitting with the nylon-rubber attachment it replaces.

A full cylinder has a pressure of ~ 1700 kPa (220 psi). This should be checked before use. With the coupling modification (shown), a cylinder can be switched on fully and the initial gas flow to the bag will be ~ 15 litres/min.

About 20 minutes of useful flow follows, before the rate drops below 5 litres/min. See graph of pressure, flow rate and gas volume plotted with time for the large (420 litre) and small (250 litre) Helium cylinders below (Graph #1 & #2).

Operational time is the period the system will provide the necessary gas flow rate to ensure there is no build-up of CO2 inside the Exit bag. The minimum flow has been determined to be ~5 litres/min (see graph #3 below). Operational time for the large cylinder is ~ 20 minutes. For the smaller ~ 12 minutes.

Videos detailing construction (including videos) of the flow control kit, along with more detail on the Flow Rate, Pressure and Volume changes with time for small (250 litre) and large (420 litre) disposable Helium cylinders, are featured in The Peaceful Pill eHandbook.