This chapter deals with issues related to mechanical ventilation in general and considers those relevant to the obstetric patient in particular. The most common modes of mechanical ventilation are: volume-controlled continuous mandatory ventilation (VC-CMV), pressure-controlled continuous mandatory ventilation (PC-CMV), intermittent mandatory ventilation (IMV), continuous mandatory ventilation (CMV), airway pressure release ventilation (APRV) and positive end-expiratory pressure (PEEP). All patients receiving mechanical ventilation should be monitored by pulse oximetry. Non-invasive ventilation can be delivered nasally or by face mask, using either a conventional mechanical ventilator or a machine designed specifically for this purpose. The 2009 H1N1 influenza pandemic and the particular susceptibility of pregnancy in such circumstances reinforce the need to appraise the rationale for mechanical ventilation in such patients. Finally, APRV as a ventilatory paradigm, in particular, may be particularly useful in the pregnant patient with pneumonits, acute lung injury, or acute respiratory distress syndrome (ARDS).