Method and apparatus for analyzing pulmonary performance
A pulmonary testing device and method are provided that measure an inspired volume of a selected gas component. In one configuration, the selected gas component is injected into the device in an airway of the device upstream of a gas analyzer. The device has opposing open ends, one for the patient's mouth and the other for inspiration of air.
1. A pulmonary testing device, comprising:
a body with first and second ends, the first end comprising a mouthpiece for a patient and the second end being open to the ambient atmosphere;
at least two test gas injectors positioned proximate to the second end forming a junction between each of the at least two test gas injectors and the body of the device, the injectors each being angled away from the first end at an angle measured relative to a centerline of the body and wherein the angle is less than 90 degrees, whereby a test gas is introduced into the body via the junctions at a direction away from the first end;
a flow rate measuring device operable to determine a flow rate of gas being at least one of inspired and expired by the patient;
a gas analyzer operable to measure a concentration of a selected test gas component during inhalation; and
a controller operable to determine a volume of the selected test gas component, wherein the controller determines a volume of the selected test gas component by measuring the gas flow rate and using the concentration of the selected test gas-component measured by the gas analyzer.
2. The testing device of claim 1 , further comprising:
a plurality of first valves in communication with a plurality of flow restrictors, the flow restrictors each imparting a different degree of flow resistance; and
a plurality of second valves in communication with a plurality of corresponding vessels, each of the vessels comprising a gas having a composition different than the gases in the other vessels, wherein the first and second valves are controlled by the controller to provide a test gas of a desired gas composition and/or flow rate.
3. The testing device of claim 1 , wherein the first and second ends lie along a centerline of the device.
4. The testing device of claim 1 , wherein the controller is configured to change a composition of the test gas while the mouthpiece is in the patient's mouth.
5. The testing device of claim 1 , wherein the controller is configured to change a flow rate of the test gas.
6. The testing device of claim 1 , wherein the controller comprises a logical circuit operable to determine an inspired volume of a selected gas component of the test gas using the following equation:
V
X
=
∑
(
ⅆ
V
I
ⅆ
t
F
X
)
i
Δ
T
i
where V X is the total volume of the selected gas component X inspired by the patient,
ⅆ
V
I
ⅆ
t
is the inspired flow rate over a sample interval (measured by the flow rate measuring device), F X is the fraction of the inspired gas flow during the sample interval that represents the selected component X (measured by the gas analyzer), ΔT i is a sample interval, i is the reference indicating which member the sample interval represents in a set of sample intervals.
7. The testing device of claim 1 , wherein the angle at which the at least two injectors is angled away from the first end is between about 10 degrees and about 75 degrees.
8. A pulmonary testing device, comprising:
a body with a first end and multiple second ends, the first end comprising a mouthpiece for a patient and at least one of the multiple second ends being open to the ambient atmosphere;
at least two test gas injectors positioned proximate to at least one of the second ends forming a junction between each of the at least two test gas injectors and the body of the device, the injectors each being angled away from the first end at an angle measured relative to a centerline of the body and wherein the angle is less than 90 degrees, whereby a test gas is introduced into the body via the junctions at a direction away from the first end;
a flow rate measuring device operable to determine a flow rate of gas being at least one of inspired and expired by the patient;
a gas analyzer operable to measure a concentration of a selected test gas component during inhalation; and
a controller operable to determine a volume of the selected test gas component, wherein the controller determines a volume of the selected test gas component by measuring the gas flow rate and using the concentration of the selected test gas-component measured by the gas analyzer.
9. The testing device of claim 8 , further comprising:
a plurality of first valves in communication with a plurality of flow restrictors, the flow restrictors each imparting a different degree of flow resistance; and
a plurality of second valves in communication with a plurality of corresponding vessels, each of the vessels comprising a gas having a composition that differs from gases in each of the other plurality of vessels, wherein the first and second valves are controlled by the controller to provide a test gas of at least one of a desired gas composition and flow rate.
10. The testing device of claim 8 , wherein the angle at which the at least two injectors is angled away from the first end is between about 10 degrees and about 75 degrees.