A respiratory mask or other sealing interface can be used in combination with a nasal cannula or other unsealing interface in providing respiratory therapies for the treatment of COPD or OSA. The mask can act as a pressure vessel over the top of a nasal cannula, with the intention of increasing expiratory pressure whilst allowing the nasal cannula to provide a user with breathing gases of a high humidity and temperature. The ability to selectively apply increased expiratory pressure may be effective in reducing a user's breathing rate and thus beneficial in the treatment of respiratory distress.