A portable, compact closed circuit ventilation device for manual ventilation of a patient undergoing a surgical or medical procedure that requires sedation as well as emergency management of respiratory failure. One example embodiment includes a closed breathing circuit having a manually squeezable bag, a carbon dioxide absorption canister, a plurality of valves, a gas port and a plurality of sensors for measuring Tidal Volume (TV), Peak Airway Pressure (PAP) and End Tidal CO2 (ETCO2). Another example embodiment includes an open breathing circuit having a bag, valves and sensors. A monitor displays the sensor measurements during the respiratory phases. In a spontaneously breathing patient the device may be used to assess the adequacy of patient's respiratory efforts. During manual or assisted ventilation, the monitor assures safe and efficacious ventilation by the closed breathing circuit.