Counterlung for a rebreathing apparatus

1. A breathing hose configured to duct inhaled and exhaled gas between a user and a rebreather apparatus, the breathing hose comprising:

a non-collapsible flexible outer tube; and

a collapsible inner tube located within the non-collapsible flexible outer tube, wherein a first end of the collapsible inner tube is affixed about an interior of the non-collapsible flexible outer tube at a first location and a second end of the collapsible inner tube is affixed about the interior of the non-collapsible flexible outer tube at a second location, the collapsible inner tube being configured for fluid communication with a mouthpiece of the rebreather apparatus;

wherein the collapsible inner tube is configured to inflate between its first and second ends and expand to the interior of the non-collapsible flexible outer tube between the first location and the second location to accommodate the exhaled gas of the user passing through the mouthpiece, and to deflate to accommodate the inhaled gas of the user passing through the mouthpiece.

2. The breathing hose of claim 1 , wherein the collapsible inner tube has a size that is configured to accommodate at least a portion of a breath volume of the user.

3. The breathing hose of claim 2 , wherein the collapsible inner tube has a size that is configured to accommodate a maximum breath volume of the user.

4. The breathing hose of claim 1 , wherein the collapsible inner tube is made of a non-stretch material having no bias in either the full or empty state.

5. The breathing hose of claim 1 , wherein the collapsible inner tube is pre-formed with a memory to create positive and/or negative pressure to counteract hydrostatic pressure imbalances.

6. The breathing hose of claim 1 , wherein the breathing hose further comprises an inhale hose and an exhale hose, and

wherein the collapsible inner tube is made of an elastic material to thereby bias gas to move through the rebreather apparatus toward the inhale hose.

7. The breathing hose of claim 1 , further comprising:

a hollow member located inside the collapsible tube, the hollow member extending along at least part of a length of the collapsible inner tube,

wherein the hollow member is configured to prevent complete collapse of the inner tube under hydrostatic pressure.

8. The breathing hose of claim 7 , wherein the hollow member comprises a hollow tube or a spiral.

9. The breathing hose of claim 1 , wherein the collapsible inner tube is configured to function as an in-hose counterlung.

10. The breathing hose of claim 1 , wherein the collapsible inner tube is configured to act, along with the rebreather unit, to maintain a constant total volume of gas in the lungs of the user and in the rebreather unit throughout a breathing cycle.

11. The breathing hose of claim 1 , wherein the collapsible inner tube is configured to perform functions of a counterlung to thereby act to maintain a constant total volume of gas in the lungs of the user and in the rebreather unit throughout a breathing cycle.

12. The breathing hose of claim 1 , wherein the breathing hose is configured to act as a counterlung in the rebreather apparatus.

13. A method of using a breathing hose configured to duct inhaled and exhaled gas between a user and a rebreather apparatus, the breathing hose including a non-collapsible flexible outer tube and a collapsible inner tube located within the non-collapsible flexible outer tube, the method comprising:

connecting the breathing hose to a rebreather apparatus, wherein the collapsible inner tube of the breathing hose is configured for fluid communication with a mouthpiece of the rebreather apparatus and the collapsible inner tube is configured to inflate between a first end of the collapsible inner tube affixed about an interior of the non-collapsible flexible outer tube at a first location and a second end of the collapsible inner tube affixed about the interior of the non-collapsible flexible outer tube at a second location and expand to the interior of the non-collapsible flexible outer tube between the first location and the second location to accommodate the exhaled gas of the user passing through the mouthpiece, and to deflate to accommodate the inhaled gas of the user passing through the mouthpiece;

further connecting the breathing hose to an external air tank to thereby form a closed circuit rebreather apparatus or a semi closed circuit rebreather apparatus;

recycling unused oxygen and nitrogen in a user's breath as the user breathes air supplied by the closed circuit rebreather apparatus or semi closed circuit rebreather apparatus;

injecting oxygen from the external air tank into the breathing hose to thereby compensate for metabolic usage of oxygen by the user from the inhaled gas; and

removing carbon dioxide from the exhaled gas.