Portable device for estimating a gas concentration released by a medium
A measuring device is disposed against a medium, the device extending between a contact face applied facing the medium and a distal end, and including a lateral wall extending between the contact face and the distal end. The device includes: at the level of the contact face, an admission opening through the contact face collecting a transcutaneous gas of interest emitted through the medium; a measuring chamber including a gas sensor measuring a concentration of the gas of interest flowing through the measuring chamber; and a collecting chamber connected to the measuring chamber and delimited by an opening on the lateral wall, the collecting chamber including a lateral opening admitting a vector gas into the collecting chamber. The measuring chamber is disposed between the contact face and the collecting chamber. The device includes a pump driving a vector gas through the collecting chamber to an evacuation opening.
1 . A measuring device configured to be disposed against a medium, the device extending between a contact face configured to be applied facing the medium and a distal end, the device including a lateral wall extending between the contact face and the distal end, the device comprising:
at a level of the contact face, an admission opening configured to collect a gas of interest emitted through the medium, the admission opening being through the contact face;
a measuring chamber including a gas sensor, the gas sensor being configured to measure a concentration of the gas of interest flowing through the measuring chamber, the measuring chamber being delimited by the lateral wall and disposed above the contact face;
a collecting chamber connected to the measuring chamber by an opening, the collecting chamber including a lateral opening through the lateral face so as to admit a vector gas into the collecting chamber, the collecting chamber being delimited by the lateral wall and disposed above the measuring chamber such that the measuring chamber is disposed between the contact face and the collecting chamber;
a pump configured to drive the vector gas admitted through the lateral opening across the collecting chamber to an evacuation opening; and
collecting openings, distributed across a collecting plate, said collecting plate separating the measuring chamber and the collecting chamber, so that driving the vector gas through the collecting chamber induces a reduction or a partial pressure of the gas of interest in the collecting chamber, thereby inducing diffusion of the gas of interest from the contact face to the collecting chamber via the measuring chamber, through the collecting openings.
2 . The device as claimed in claim 1 , further comprising a heat source configured to heat the contact face to a temperature greater than 37° C.
3 . The device as claimed in claim 1 , wherein the evacuation opening is oriented about an evacuation axis perpendicular or perpendicular to within 30° to the contact face, the collecting chamber opening into the evacuation opening.
4 . The device as claimed in claim 1 , wherein the evacuation opening is through the lateral wall of the collecting chamber.
5 . The device as claimed in claim 1 , wherein the gas sensor of the measuring chamber is disposed at a distance less than 8 mm from the contact face.
6 . The device as claimed in claim 1 , wherein the gas sensor is an optical sensor including an infrared source configured to emit infrared light and a photodetector, the measuring chamber being such that the gas of interest flows in the measuring chamber between the infrared source of and the photodetector in a flow direction perpendicular or perpendicular ±30° to the contact face.
7 . The device as claimed in claim 6 wherein the infrared source is configured to produce a flat light beam parallel or parallel to within ±30° to the contact face.
8 . The device as claimed in claim 7 , wherein a thickness of the flat light beam in a direction of a transverse axis perpendicular to the contact face is less than 5 mm.
9 . The device as claimed in claim 8 , wherein the measuring chamber includes two walls parallel to the contact face, each wall being reflective to the infrared light emitted by the infrared source, the walls delimiting the flat light beam in which the infrared light propagates between the infrared source and the photodetector.
10 . The device as claimed in claim 9 , wherein a reflecting wall forms the contact face.
11 . The device as claimed in claim 10 , wherein the reflecting wall nearest the contact face is configured to be heated so as to heat the medium.
12 . The device as claimed in claim 9 , wherein:
each reflecting wall includes transverse baffles;
each transverse baffle of a reflective wall extends toward an opposite reflective wall;
a gap is formed between each transverse baffle and the reflective wall opposite it the transverse baffle;
a transverse baffle of a reflective wall extends between two transverse baffles of the opposite reflective wall; and
se that the light emitted by the light source propagates between the successive transverse baffles before reaching the detector.
13 . The device as claimed in claim 1 , wherein an air flowrate of the pump is between 0.1 and 10 mL/min.
14 . A method of estimating a concentration of a gas of interest in a medium using a device as claimed in claim 1 , the device being applied so that the contact face is disposed facing the medium, the pump being activated, the method comprising:
a) estimating a gas of interest concentration in the measuring chamber; and
b) from the gas of interest concentration in the measuring chamber resulting from step a) estimating the partial pressure of the gas of interest given off by the medium.
15 . The method as claimed in claim 14 , wherein the medium is the skin of a user, the skin extending over a blood vessel, and step b) includes:
(i) on the basis of the gas of interest concentration in the measuring chamber resulting from step a) estimating a transcutaneous gas of interest concentration;
(ii) estimating a concentration or partial pressure of the gas of interest dissolved in medium on the basis of the transcutaneous gas of interest concentration resulting from sub-step (i).
16 . The method as claimed in claim 14 , wherein the medium to be analyzed is a solid or liquid medium.
17 . The method as claimed in in claim 14 , wherein the vector gas is air.
18 . The device of claim 1 , wherein the collection openings are distributed across a cross section greater than 1 cm 2 .