Breath Analyzer

Nothing new there.
Important thing is to get the back pressure in the sensing head right else it will effect the patient.
It's all about the sensor (and a good DC couple amplifier), the rest is just a load of software.
Too much back oressure allows collapsed airways to expand and become more efficient.
That's why people with emphysema often exhale through pursed lips.
This field is well researched and well documented. My previous job was pretty much in the field of respiratory instrumentation. I designed one about 20 years ago.

This thread may be of interest.

Del

I agree that monitoring must not affect the flow of breathed in-out air. Even though this field is well researched, there is always something to do to find new parameters that are valuable.

I have CPAP machine for my wife and it has pressure sensor and assists her in breathing when she gets sleep apnea attack.

Current experiment goes farther and uses high frequency components in the range of 500Hz to 10kHz to get low frequency envelop of 0.1Hz to 10Hz to look at what is happening in high frequency zone during breathing and how it correlated to low frequency breath pressure envelop of 1 to 60 breath cycles per minute.

Amplifier board is shown here. PCB size is 2" x 2" and there is a threshold detector potentiometer for noise rejection.

Dr. Shyam, interesting breath analysis project. Just a thought here : Have you ever looked into the use of breath analysis (as in the level of trace gases) to relate it to medical conditions or ailments? I used to play around with old reconditioned Gas Chromatographs a few years ago and tried to get into this. The idea was to set up a cheap, easy and rapid system of preliminary diagnosis. More a form of screening. I subsequently moved on and have not worked with GC's since.

I guess that your problem with this as a technique is how consistant is the baseline for 'healthy' patients. I suspect that this baseline is more probably a base range so wide that any small variation in 'unhealthy' folks would be obscured. In instrumentation speak "the noise would be greater than the signal".

JH Assoc : Note the differences in a GC Fingerprint often stand out can be quite unique for people with different ailments. The project intended to set up a database and to establish the common trends in the fingerprint for different ailments. We did not carry this out to the end. I believe other groups have done this. It is found that a particular ailment will give rise to a GC Fingerprint that has peaks for certain gases or volatiles. The breath has traces of gases that vary depending on diet, ailments, eating habits, etc. A pity I don't have access to such equipment any more.

In this experiment we are monitoring lung cavity and wind pipe audio resonance signals associated with breathing cycle. In fact breathing cycle can very drastically and that is important only when we are looking at air volume used by the lungs generally during exercise. In natural breathing the demand of oxygen changes the breathing rate. Air volume used by each person differs considerably and this also has greater impact on the breathing rate. While sleeping the breathing rate drops down and during dreams and sleep disorders it can fluctuate.

There are three major informations here.

Breathing rate

Breath volume

Audio sound / noise components in breathed in-out air

Breathing can stop for a minute and that is all possible and normally brain skips many breath cycles during sleep apnea and then gives a jurk of heavy breath to wake up the person or to restart in some what awake condition of slightly awared condition of the body.

For normal observations, we look at those primary three signals for a person willing to be tested in fully awake condition and during excercise runs under stress tests.

Sleep disorder Sleep Apnea has been extensively studied and lots of instruments are already developed now by many manufacturers. Sleep analysis software are also very good one and provide wealth of information.

Yes I do have a separate experiment for chemical analysis using IMS. However, this current design is for physical parameter to which chemical sample can be taken online for analysis in parallel. Some people do LASER GC, but that requires larger optical setup. IMS is compact and can be hooked easily.

There are much better GC machines available now if one has the $$, but basically these apply a rapid thermal ramp to the oven, with a short capillary column that can largely speed up the analysis, thus making possible many more screenings per work shift.

My dad was a physician - he used a stethoscope.

He could diagnose asthma, apnea, rattles, pneumonia, heart problems, etc, just by listening.

GW, sounds like your dad was a great General Practitioner. Is he still practicing? These guys are not easy to come by these days. Some good Osteopaths can obtain an enormous amount of info relating to the condition of muscle tissue simply by touch.

Stethoscope transmits sound through body walls and here we can get the same signal cleaner through lungs and wind pipe linked air cavity to the sensor. We can also get low frequency signal which otherwise can't be heard as it is below 1Hz.