Removable and/or replaceable humidifier

1. A respiratory treatment apparatus comprising:

a positive airway pressure device to provide a source of flow of air at positive to ambient;

a humidifier housing having a gas inlet to receive sealably the flow of air at positive pressure from said source in use and a gas outlet adapted to be connected to a gas conduit to deliver humidifier gas to a patient mask;

a plate positioned within the humidifier housing;

a water distribution member forming a water envelope for receiving liquid water, the water distribution member being fitted into the humidifier housing and including an upper wall and a lower wall between which the water envelope is formed, the upper wall being a semi-permeable material positioned below but spaced from the plate, and the lower wall being a heat conductive material;

an electric heater in thermal contact with the lower wall and adapted to heat the liquid water to form water vapor;

a gas passage layer between the gas inlet and the gas outlet, the gas passage layer configured to permit a gas flow to flow from the gas inlet to the gas outlet, the water distribution member being configured and arranged to deliver water vapor to the gas passage layer;

wherein:

the plate splits the gas passage layer into a humidification passage and a dry gas passage, the humidification passage being positioned between the upper wall of the water distribution member and the plate, the dry gas passage being positioned between the plate and a wall of the humidifier housing above the plate,

an amount of the gas flow entering into the humidification passage and the dry gas passage is variable, and

the semi-permeable upper wall of the water distribution member is configured to deliver the water vapor but not the liquid water to the humidification passage; and

the water distribution member has a flange that is sandwiched between the humidifier housing and a base plate connected to the humidifier housing.

2. The respiratory treatment apparatus according to claim 1 , wherein the plate is configured to direct a portion of gas from the gas flow away from the humidification passage and into the dry gas passage.

3. The respiratory treatment apparatus according to claim 1 , wherein the humidification passage includes a valve for varying the gas flow through the humidification passage and wherein the dry gas passage includes a valve for varying the gas flow through the dry gas passage.

4. The respiratory treatment apparatus according to claim 1 , wherein during use the gas flow is configured to be split between the humidification passage and the dry gas passage such that a humidification flow added to a dry gas flow equals the gas flow, wherein reducing the humidification flow increases the dry gas flow and increasing the humidification flow decreases the dry gas flow, wherein the gas flow enters the gas passage layer at a first humidity and exits the gas passage layer at a second higher humidity.

5. The respiratory treatment apparatus according to claim 1 , wherein the dry gas passage includes a dry gas flow regulator and the humidification passage includes a humidification flow regulator, wherein the dry gas flow regulator and the humidification flow regulator are variable to vary a humidity level the gas flow at the gas outlet.

6. The respiratory treatment apparatus to claim 5 , wherein the dry gas flow regulator is a butterfly valve and the humidification flow regulator is a separate butterfly valve.

7. The respiratory treatment apparatus according to claim 1 , further comprising a sliding shutter, the sliding shutter including an aperture and a blocker, the sliding shutter being movable, wherein during use when the blocker blocks the gas flow through the dry gas passage, gas is directed to the humidification passage, and wherein when the aperture is aligned with the dry gas passage, gas is permitted to flow through the dry gas passage.

8. The respiratory treatment apparatus according to claim 1 , wherein the semi-permeable upper wall of the water distribution member forms a portion of the humidification passage and the humidifier housing forms a separate portion of the dry gas passage.

9. The respiratory treatment apparatus according to claim 1 , wherein the humidifier housing is detachable from the positive airway pressure device.

10. The respiratory treatment apparatus according to claim 1 , wherein the water distribution member has a thickness of about 1-10 mm.

11. The respiratory treatment apparatus according to claim 1 , wherein the water distribution member has a thickness of less than about 2 mm.

12. The respiratory treatment apparatus according to claim 1 , wherein the water distribution member and the heater are removably attached to the humidifier housing.

13. The respiratory treatment apparatus according to claim 12 , wherein the base plate supports the heater, and wherein the base plate, the water distribution member and the heater are removably attached to the humidifier housing.