Cough/sneeze analyzer and method
View Patent ↗A cough event is differentiated from a sneeze event of a test subject enclosed within a plethysmograph test chamber by measuring air pressure changes during the event, and comparing the pressure changes against criteria indicative of a cough to determine the likelihood that the event is a cough. Air pressure changes are recorded as pressure and/or sound values. A graphical record of a waveform of changes in the air pressure during an event relative to a baseline value is recorded, and a value is calculated that is indicative of the likelihood that the event is a cough based on the sizes of areas between the waveform and baseline during the event, said areas including a first area indicative of the change in air pressure during air inspiration, a second area indicative of the change in air pressure during air compression, and a third area indicative of the change in air pressure during expiration.
1. A method of differentiating between a cough and a sneeze of a test subject within a plethysmograph test chamber comprising:
a) measuring changes in the air pressure within the chamber during an event that is a cough or a sneeze; and
b) comparing the parameters of the air pressure changes against parameters indicative of a cough to determine the likelihood that the event is a cough instead of a sneeze.
2. The method of claim 1 , further including measuring the sound of the event and comparing the sound against criteria indicative of a cough.
3. The method of claim 1 , wherein the pressure changes are measured with a differential pressure transducer.
4. The method of claim 1 , wherein said plethysmograph includes a reference chamber, said pressure change being determined by comparing the pressure within the test chamber relative to the pressure within the reference chamber.
5. The method of claim 1 , wherein changes in air pressure are measured during air inspiration, during air compression, and during expiration.
6. A method of differentiating between a cough and a sneeze of a test subject within a plethysmograph test chamber comprising:
a) graphing a waveform of changes in the air pressure within the chamber during an event that is a cough or a sneeze relative to a baseline measurement;
b) measuring the size of the areas between the waveform and baseline during the event;
c) measuring the time between the waveform crossing certain thresholds; and
d) comparing the sizes and times of threshold crossings of the measured areas against sizes and times of threshold crossings indicative of a cough to determine the likelihood that the event is a cough instead of a sneeze.
7. The method of claim 6 , wherein said areas include a first area indicative of a waveform in air pressure during air inspiration, a second area indicative of a waveform in air pressure during air compression, and a third area indicative of a waveform in air pressure during expiration.
8. The method of claim 6 , further including adjusting the step of comparing for the weight of the test subject.
9. The method of claim 6 , further including measuring the timing between descending slopes of a portion of the waveform indicative of compressing and a subsequent portion of the waveform indicative of re-expansion.
10. The method of claim 6 , wherein said waveform is measured with a differential pressure transducer.
11. The method of claim 6 , wherein said plethysmograph includes a reference chamber, and wherein a pressure change is determined by comparing the pressure within the test chamber relative to the pressure within the reference chamber.
12. A method of differentiating between a cough and a sneeze of a test subject within a plethysmograph test chamber comprising:
a) graphing a waveform of changes in the air pressure within the chamber during an event that is a cough or a sneeze relative to a baseline measurement;
b) measuring the size of areas between the waveform and baseline during the event, said areas include a first area V1 indicative of a change in air pressure during air inspiration, a second area V2 indicative of a change in air pressure during air compression, and a third area V3 indicative of a change in air pressure during expiration;
c) computing the parameter V2wc to adjust for weight of the test subject by the formula
V 2 wc= 1000· V 2/ WT
where WT is the weight of the test subject; and
d) determining a volume possibility value fzyV2wc for the event by the formula
fzyV2wc
=
1
-
1
1
+
ⅇ
V2b
(
V2wc
-
V2a
)
where
V2a
=
V2wcThreshold
V2b
=
V2wcCrispness
V2a
V2a and V2b are constants, V2wcThreshold is a value at which the V2wcparameter is 50% certain to be a cough, and V2wcCrispness is a relative sharpness of the transition of the V2wc values between events being considered coughs or sneezes, said volume possibility value being indicative of the likelihood that the event is a cough.
13. The method of claim 12 , further including determining a sound possibility value fzyDHPC for the event by the formula
fzyDHPC= 1−1/(1+ e^ ( DHPCb* ( DHPC−DHPCa )))
where:
DHPCa=DHCPThreshold
DHPCb=DHPCCrispness/DHPCa
DHPC is the time from one half of the maximum of the pressure waveform in the are V2 to the time of one half of the minimum of the pressure waveform in the area V3, DHPCThreshold equals the value at which the DHPC timing is 50% certain to be a cough, and DHPCCrispness is a relative sharpness of the DHPC parameter in determining cough, said sound possibility value being indicative of the likelihood that the event is a cough.
14. The method of claim 13 , wherein said volume and timing possibility values are combined to create a combined possibility value fzyIsCough by the formula
fzyIs Cough=( fzyV 2wc *V 2 wc Weight+ fzyDHPC*DHPC Weight)/( V 2 wc Weight+ DHPC Weight)
where V2wcWeight equals the relative importance of the V2 parameter in determining cough, DHPCWeight equals the relative importance of the DHPC parameter in determining cough.
15. The method of claim 14 , further including determining if the event is a cough by comparing fzyISCough to a threshold value.
16. An apparatus for differentiating between a cough event and a sneeze event of a test subject comprising:
a) a plethysmograph having a test chamber for enclosing said test subject;
b) a measurement means for measuring air pressure changes within said chamber;
c) a recorder for recording changes measured by said measurement means; and
d) a processor with installed software capable of calculating a value based on the pressure changes during an event indicative of the likelihood that the event is a cough.
17. The apparatus of claim 16 , wherein said plethysmograph further includes a reference chamber, and said measurement means is a differential pressure transducer in communication with said test and reference chambers.
18. The apparatus of claim 16 , wherein said recorder is adapted to record air pressure changes as pressure values and as sound.
19. The apparatus of claim 16 , wherein said recorder is adapted to graphically record a waveform of changes in the air pressure within the chamber during an event relative to a baseline value, and said processor is adapted to calculate a value indicative of the likelihood that the event is a cough based on the sizes of areas between the waveform and baseline during the event, said areas including a first area indicative of a change in air pressure during air inspiration, a second area indicative of a change in air pressure during air compression, and a third area indicative of a change in air pressure during expiration.