A respiratory muscle endurance training device (RMET) includes a chamber and a patient interface. In one implementation, one or both of a CO2 sensor or a temperature sensor can be coupled to the chamber or patient interface to provide the user or caregiver with indicia about the CO2 level in, or the temperature of, the chamber or patient interface and/or the duration of use of the device. In another implementation and the RMET may have a fixed volume portion adjustable to contain a measured portion of a specific patients inspiratory volume capacity. Methods of using the device are also provided.