Hi Chee Siang

Try  the paper

Measurement of Respiratory Flow with Ultrasonic Sensor Using the Technique of Forced Oscillations

Will Almeida; Bruno Costa; Sebastian Catunda; Raimundo Freire; Francisco Santos

2006 IEEE Instrumentation and Measurement Technology Conference Proceedings Year: 2006, Pages: 1368 - 1372, 

This is an alternative way that may help.

In relation to the use of EMG, you may try the paper

Measurement of Breathing Frequency, Airflow, and Lung Volumes

http://aibolita.com/sundries/25610-measurement-of-breathing-frequency-airflow-and-lung-volumes.html

Good luck

Maki Habib

The proxy in sleep apnoea measurements is SpO2.

If you can find a Mac-friendly device to do this, do let me know, I can only find Windows-compatible devices/software.

Good question. The answer is longer than you might expect.

Respiration, compared to other biosignals, is annoying. Really accurate measurement (like spirometry) interferes with your ability to measure someone normally. (Have you ever tried breathing normally with your nose clamped shut, or an orofacial mask on?) Less accurate measurement, well, is less accurate.

Off the top of my head, there are about seven 'normal' ways of measuring respiration.

1. spirometry/mask

2. nasal cannula (with a variety of different sensors picking up the flow information)

3. piezo belt 

4. RIP belt

5. other measurements of "chest wall excursion" (webcam, magnetometer, accelerometer etc.)

6. ECG / PPG / oximeter transform

7. thoracic impedance

Transthoracic EMG is possible too but it's not at all common - is that what you've planned? I've never tried it.

They all have benefits and drawbacks - they are more or less accurate, they return more or less accurate aspects of the respiratory cycle (cycle length, expiratory/inspiratory times, tidal volume, etc.), they all vary with utility when oxygen requirements and measurement environments change (e.g. in COPD, the respiratory cycle is impaired, during exercise the respiratory cycle is obviously exaggerated) and they are more or less expensive, easy to use, and easy to purchase.

In general, a nasal cannula can do a good job at rest (and there's a tonne of research on various builds you can find easily).

So, more questions:

a) are you looking for cycle length or more? (tidal volume etc.)

b) are people healthy, at rest, etc.?

c) we haven't gotten to CO2/O2 yet... is this involved?

thanks. We are only interested at the moment in healthy people at rest, and when they are doing a range of normal daily activity (like walking, lying down, etc).

I am predominantly interested in detecting breathing events (inhale , exhale), with a possibility of detecting volume of air flow, using only surface EMG sensors.

Have you come across any relevant literature ??