Abstract: A modular ventilator according to the present disclosure may include a ventilator core and a ventilator service module. The ventilator core provides the basic functionality necessary for delivering suitably oxygenated air to a patient without most or all typical patient monitoring functions except a basic alarm or safety alert triggered by loss of pressure at the output. Additional patient monitoring functions are embodiment in the removable ventilator service module, which may be powered by its own power source and/or by the power source of the ventilator core when coupled thereto. The ventilator core is configured for low cost manufacture and ease of operation and may be portable so as to be easily deployable in a non-hospital setting. The ventilator core may employ a venture-based O2 regulator for adjusting the oxygen-air mixture at the output, which may facilitate the manufacture of the ventilator core at lower cost than conventional ventilators.