A gas routing module for insertion within a respiratory treatment apparatus is adapted to couple within a gas ports interface of a discrete compartment of a chassis of the respiratory treatment apparatus. The gas routing module comprises:- a plurality of gas routing channels adapted for gas communication with expired airflow； and- a gas ports interface, the gas ports interface including a plurality of gas ports in gas communication with the plurality of gas routing channels, wherein the gas ports interface comprises two or more of:(a) a port for expiratory pressure sensing,(b) a port for a PEEP air supply, and(c) a set of ports for expiratory flow sensing through one or more of the plurality of gas routing channels of the module.
