Abstract: A system that enables the accurate monitoring of tidal volume of a patient when using a Bain, Mapleson D or similar type of patient breathing circuit in an anesthesia system. The system allows the use of flow sensors positioned at the machine or distal end of the patient breathing circuit and not at the less desirable patient or proximal end of the patient breathing circuit. Thus, the flow sensors can be positioned out of the way of the patient and will provide a measurement of the tidal volume of the patient. A CPU is used to take into account, the additional fresh gas provided to the patient breathing circuit during the expiration cycle to correct the flow monitored in the main breathing tube that supplies the gas to the patient from a ventilator or breathing bag.

Abstract: An apnea detection system is disclosed for use with a medical ventilator and which detects the volume of gas delivered by the ventilator to a patient and also the volume of gas exhaled by the patient. The two flow measurements are compared, preferably in a microprocessor, to determine whether an apnea condition exists by comparing, against a known standard, the two detected volumes. The volume of the exhaled gas must be a predetermined percentage of the volume of gas delivered to the patient within a predetermined time period or an alarm is activated indicating an apnea condition.

Abstract: An audible waveform system is provided that senses a parameter relating to the ventilation of a patient. The system produces short bursts of sound of a predetermined frequency as the changes occur in that parameter based on certain increments of change. The bursts themselves are preferable at a frequency that is the same for equal pressures but increases and decreases in frequency as the parameter increases or decreases, respectively. In the preferred embodiment, the system provides an audible waveform based on the pressure in the patient airway so that the clinician can receive information relating to that waveform conveniently and without taking attention away from other monitors and/or alarms.

Abstract: A control system where the clinician can have manual control of the state for various alarms, generally volume alarms and apnea alarms. The control is interactive, that is, while the clinician can manually set the state in a variety of settings, the control system automatically overrides the clinician's selection to activate both the volume and apnea alarms wherever the mechanical ventilator is turned on. In addition, there is another override where a breath is detected by the ventilator to turn all of the alarm systems from both being inactive to both alarms being active.

Abstract: An algorithm is disclosed that enables the display for a medical ventilator to automatically adjust its wave characteristics depending on the settings for that ventilator established by the clinician. As the respiratory rate, or rate at which the ventilator provides breaths to the patient, is changed by the user, the rate of sweep of the waveform generator displaying that data is also changed to insure that the data is displayed in the most relevant manner. As another parameter, as the pressure limit in the patient circuit is set by the clinician, the waveform vertical scale is adjusted to make sure the particular limit of pressure is displayed. As the pressure limit or the respiratory rate are changed in the ventilator by the clinician, the waveform of he data displayed also is automatically modified to make that data best presentable to the clinician.

Abstract: An improved system for the determining the collapse of a bellows within a canister as part of a ventilator system for delivering breaths to a patient via a patient circuit. The system measures the pressure in the bellows canister external of the bellows and measures the pressure within the interior of the bellow. A processor compares the pressures and determines when the pressure within the canister exceeds a predetermined offset in excess of the pressure within the interior of the bellows to conclude that the bellows is in a collapsed condition. In the preferred embodiment, the processor also uses, as input data, the flow delivered by the ventilator to the bellows canister to determine that offset value. When a bellows empty condition is determined, various actions can be taken, among them to signal an alarm and also to change various functions of the ventilator to prevent further difficulties in the overall system.