Abstract: A noninvasive photoplethysmographic sensor platform for mobile animals such as small rodents, namely rats and mice is useful such as in a laboratory research environment. The noninvasive photoplethysmographic sensor platform may be a collar which provides an easily affixed, adjustable attachment mechanism that encircles the animal, such as the neck. The neck of the animal provides several particular advantages as a sensor mounting platform for photoplethysmographic sensors. For pulse oximetry, the neck location will provide significant blood flow under all conditions. For small mammals, such as rats and mice, transmittance pulse oximetry through the neck of the subject remains possible. The neck mounted collar also offers inherent bite resistance to the sensor platform.

Abstract: A noninvasive photoplethysmographic sensor platform for mobile animals such as small rodents, namely rats and mice is useful such as in a laboratory research environment. The noninvasive photoplethysmographic sensor platform may be a collar which provides an easily affixed, adjustable attachment mechanism that encircles the animal, such as the neck. The neck of the animal provides several particular advantages as a sensor mounting platform for photoplethysmographic sensors. For pulse oximetry, the neck location will provide significant blood flow under all conditions. For small mammals, such as rats and mice, transmittance pulse oximetry through the neck of the subject remains possible. The neck mounted collar also offers inherent bite resistance to the sensor platform.

Abstract: A humidifier for use with a pressure support system. The humidifier includes a body having an inlet, a fluid holding chamber, and an outlet. The inlet is positioned upstream and in fluid communication with the fluid holding chamber. The outlet is positioned downstream of and in fluid communication with the fluid holding chamber. A back-flow preventing valve is positioned upstream of the fluid chamber. The back-flow preventing valve is movable between an open position, in which the inlet is unblocked, and a closed position in which the inlet is blocked. In the closed position, the back-flow preventing valve prevents fluid, fluid vapor, or both from entering the pressure support via the inlet to the humidifier.

Abstract: A humidifier for use with a pressure support system. The humidifier includes a body having an inlet, a fluid holding chamber, and an outlet. The inlet is positioned upstream and in fluid communication with the fluid holding chamber. The outlet is positioned downstream of and in fluid communication with the fluid holding chamber. A back-flow preventing valve is positioned upstream of the fluid chamber. The back-flow preventing valve is movable between an open position, in which the inlet is unblocked, and a closed position in which the inlet is blocked. In the closed position, the back-flow preventing valve prevents fluid, fluid vapor, or both from entering the pressure support via the inlet to the humidifier.

Abstract: A gas delivery system that generates a pressurized flow of breathable gas for delivery to a patient. The system includes a primary gas delivery system for delivering a flow of pressured gas to the airway of a patient and supplemental gas delivery system. The supplemental gas delivery system is in the form of a modular gas regulator assembly that regulates the flow of supplemental gas from a gas source to the primary gas delivery system so that supplemental gas is delivered to the patient concomitant with the pressurized flow of breathable gas. The system allows the user to selectively control the gas concentration level of the supplemental gas, such as oxygen, helium, nitrogen or any combination thereof, and the pressurized flow of breathable gas delivered to the patient concomitantly.

Abstract: A gas delivery system comprising a pressure generator, a pressure sensor, a control valve, and a processor. The pressure generator pressurizes breathable gas for delivery to a patient. The pressure sensor measures a pressure difference between the pressurized breathable gas and atmospheric pressure. The control valve is disposed downstream from the pressure generator and is constructed and arranged to control a flow rate of the pressurized breathable gas. The processor controls the control valve to bring the flow rate of the pressurized breathable gas to substantially zero while the pressure generator is operating and, when the flow rate is substantially zero, determines at least one of atmospheric pressure, an atmospheric air density, or a density correction factor based at least in part on the pressure difference between the pressurized breathable gas and the atmospheric pressure.

Abstract: A pressure support system has a motor, a switching element that supplies power to motor windings, and a blower coupled to the motor. Rotation of the blower elevates a pressure of fluid in a patient circuit coupled to an outlet of the blower. A rotational speed controller maintains the motor at a set rotational speed corresponding to a selected pressure for the fluid in the patient circuit. The rotational speed of the motor is maintained by a switching signal provided by a rotational speed controller to the switching element to control the actuation of the switching element. A fluid parameter monitoring portion monitors a parameter associated with the flow of fluid in the patient circuit, such as the magnitude, direction, or volume, based on a characteristic, such as duty cycle, of the switching signal, or based on a characteristic of a control signal that is used to generate the switching signal.