The system described comprises a respiratory therapy flow device, a respiratory circuit, and an exhalation valve. The device includes an exhalation pressure control port. The exhalation valve is removably engaged with the exhalation pressure control port and the respiratory circuit. The valve comprises a lid, a diaphragm, and a housing body. The housing body comprises a ramped lock configured to engage the respiratory therapy flow device at the exhalation pressure control port. Responsive to an engagement between the valve and the exhalation pressure control port, the lid forms a compression seal with the exhalation pressure control port, the diaphragm forms a compression seal with the lid, and the diaphragm is selectively controlled via gas pressure received through the exhalation pressure control port such that gas in the respiratory circuit flows to the ambient atmosphere during exhalation by the subject.
