Gases mixing and measuring for a medical device

A method for determining a characteristic of gases flowing through an apparatus along a gases flow path from a first end of the apparatus to a second end of the apparatus, the apparatus comprising a first ultrasonic sensor positioned at the first end and a second ultrasonic sensor positioned at the second end, a downstream direction defined along the gases flow path from the first end to the second end and an upstream direction defined along the gases flow path from the second end to the first end, the method comprising:

• transmitting a downstream acoustic pulse train from the first ultrasonic sensor and detecting the downstream acoustic pulse train at the second ultrasonic sensor;
• determining a downstream time of flight based at least in part on the downstream acoustic pulse train;
• transmitting an upstream acoustic pulse train from the second ultrasonic sensor and detecting the upstream acoustic pulse train at the first ultrasonic sensor;
• determining an upstream time of flight based at least in part on the upstream acoustic pulse train;
• determining a temperature of the gases flowing along the gases flow path at an inlet of the apparatus using a first temperature sensor;
• determining a temperature of the gases flowing along the gases flow path at an outlet of the apparatus using a second temperature sensor;
• determining the characteristic of the gases based at least in part on the downstream time of flight, the upstream time of flight, and the temperature of gases flowing along the gases flow path at the inlet and outlet of the apparatus;
• and
• determining a pressure of the gases flowing in the flow path using a pressure sensor,
• wherein the gases are configured to flow from a portion of the gases flow path upstream of the apparatus, the portion of the gases flow path comprising a gases flow guide configured to improve laminar flow of the gases prior to entering the apparatus, the gases flow guide located downstream of a gases source,
• wherein the apparatus comprises a single gases measuring chamber defined by a housing of the apparatus, wherein the first and second ultrasonic sensors, the first and second temperature sensors, and the pressure sensor are located at the single gases measuring chamber, and wherein the single gases measuring chamber is coaxial with a gases mixing chamber.

A gases delivery apparatus comprising:

• a gases mixing chamber configured to receive gases from a gases source, the gases mixing chamber comprising a gases flow path from a first end of the gases mixing chamber to a second end of the gases mixing chamber and at least one mixing element situated within the gases flow path;
• a humidification system;
• and
• a gases measurement apparatus comprising:
• a gases measuring chamber configured to receive the gases from the gases mixing chamber, wherein the gases measuring chamber and the gases mixing chamber are coaxial, the gases measuring chamber comprising a gases flow path from a first end of the gases measuring chamber to a second end of the gases measuring chamber, wherein a downstream direction is defined along the gases flow path from the first end to the second end and an upstream direction is defined along the gases flow path from the second end to the first end;
• a controller;
• and
• the gases measuring chamber further comprising:
• a first ultrasonic sensor positioned at the first end of the gases measuring chamber, the first ultrasonic sensor configured to transmit a downstream acoustic pulse train in a first measurement phase, to detect an upstream acoustic pulse train in a second measurement phase, and to send a signal to the controller;
• a second ultrasonic sensor positioned at the second end of the gases measuring chamber, the second ultrasonic sensor configured to transmit the upstream acoustic pulse train in the second measurement phase, to detect the downstream acoustic pulse train in the first measurement phase, and to send a signal to the controller;
• a first temperature sensor at an inlet of the gases measuring chamber, the first temperature sensor configured to measure temperature of the gases flowing in the gases flow path at the inlet;
• a second temperature sensor at an outlet of the gases measuring chamber, the second temperature sensor configured to measure temperature of the gases flowing in the gases flow path at the outlet;
• and
• at least one pressure sensor configured to measure a pressure of the gases flowing in the gases flow path;
• wherein the controller is configured to determine a characteristic of the gases based at least in part on a signal received from the first ultrasonic sensor, a signal received from the second ultrasonic sensor, a signal from the first temperature sensor, and a signal from the second temperature sensor,
• wherein the at least one mixing element is configured to mix gases in the gases flow path of the gases mixing chamber and to improve laminar flow of the gases before the gases enter the gases flow path of the gases measuring chamber, the at least one mixing element located downstream of the gases source.