Capnographic measurement of bronchospasm requires linking the patient to a capnograph via a sampling catheter fixed to the upper lip and introduced into the nostril for a few millimeters. The analog output of the apparatus is connected to an analog-digital conversion card slotted into a PC computer. Specific software converts PeCO2 data into capnographic waveform, measures shape indices and draws their trend curves.


The patient, 4 to 99 years old, should be relaxed and resting, either awake or asleep .

Patient during capnographic recording



The catheter (1mm x 1.5m) is fixed to the upper lip using adhesive tape. It enters the nostril for a few millimeters.

 Catheter fixed to the upper lip

 A significant recording requires good nasal permeability which can be improved using a nasal decongestant.



An infra-red aspirating CO2 monitor continuously draws a sample from expelled gas, measures PeCO2, draws its time-related waveform and sends the data to the analog output of the apparatus.

Normal crenellated traceShark-fin appearance



Analog-digital conversion card : analog output of the CO2 monitor is connected to a specific conversion card (Digimétrie R) slotted into a PC computer. This card converts the analog signal into numeric data. 


PC computer : The conversion card is slotted into an 8 bit ISA connector of a PC computer (DOS or Windows).



Software : Specific DOS-Windows software (Capno R) processes numeric data and measures capnographic indices.

It combines 4 simultaneous functions performed in real-time:

Length of recording is unlimited (12-24 hours). Display allows use of a controllable zoom (1h-12h/screen).

In addition, software has semi-automatic validity functions which clear invalid trends related to deteriorated cycles.

Screen capture of the capnography software

Screen capture:

Upper window : capnographic waveform (one minute scrolling / screen) .
Middle band : mean values (and SD) of the capnographic measurements for the minute elapsing.
Lower window : Capnographic indice trends using a controllable zoom.
At the top : rolling menu for accessing software functions.
At the bottom : quick access to main functions.


Finaly, computerized capnography provides bronchospasm assessment which is:

Automation of the method allows monitoring of asthma in various conditions.