I am a student working on a project dealing with Mechanical ventilators. I am trying to design a system that can measure Airway Pressure during Mechanical ventilation, using a stand-alone airway pressure sensor. I realize that the Airway Pressure is the difference between pressure in the breathing circuit and the ambient air. However, if I do a gauge measurement (i.e., measuring circuit pressure with reference to ambient pressure), the ambient pressure is changing all the time, thereby causing a continuous drift in my airway pressure measurement. How do I overcome this scenario? Can I use an absolute measurement instead (i.e., measuring circuit pressure with reference to vacuum)?
I have left this one alone hoping someone who got the question better might help you. Here is what I think, and I hope someone else will back me up or provide more insight so I can get it. If I could have a dollar for every peak pressure measurement I have witnessed over the >30 yrs I have been at the bedside as an RT I would be a billionaire. I have adjusted alarms and PEEPS, pressure control, and pressure support all based on either direct measurement of pressures or measurements relayed from the pressure sensing sites within the ventilator, the vent tubing or airway adapter. One of the devices I had the most fun with used esophogeal pressure measurements which are supposed to better reflect intrathoracic pressures. None, not one ever of these pressures that I was monitoring or using etc. had to be so precise that the relatively minor fluctuations that occur in ambient pressures relative to the measured pressures really mattered. You are splitting some very fine hairs with what ever you are looking at and I am not sure how it will really matter if you have a peak pressure of 25 cmH2O pressure when the barometer is a 745 mmHg or at 750 mmHg.