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Pressure Regulation in a Mechanical Breathing Aid Disclosure Number: IPCOM000018244D
Original Publication Date: 2002-Apr-01
Included in the Prior Art Database: 2003-Jul-23
Document File: 1 page(s) / 144K

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Kiomars Fathollahzadeh: AUTHOR



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Pressure Regulation in a Mechani-cal Breathing Aid

Idee: Kiomars Fathollahzadeh, S-Solna


In order to regulate patient pressure, particularly in apressure controlled mode of ventilation, it is commonto employ a control algorithm that uses both inspira-tion and expiration pressure signals simultaneously.Since the pressure measurements are made in differ-ent locations a large time difference exists betweeninspiration and expiration pressure readings. Moreo-ver, the  time  difference  is  also  dependent  on  thelengths of tubing used in the inspiration and expira-tions  sides  of  the  external  pneumatic  circuit thatconnects a patient to the breathing aid. Thus the timedifference can typically vary from one or two milli-seconds to several tens of milliseconds.

This time difference causes different phase shifts atdifferent frequencies of the measured pressures. Thismakes it impossible  for  the  regulation  to  functionsatisfactorily if it is not adaptable to the particulartubing lengths. If adaptation does not occur then thesystem becomes unstable and oscillations in pressureoccur at about typically 100 Hz.

If the pressure regulation is based only on the inspi-ration pressure, that  is  the  expiration  pressure  de-pendency is  removed  from  the  control  algorithm,then the patient will experience only a slow pressureapplication; this is clinically unacceptable.

On the other hand, if the pressure regulation is basedonly on the expiration pressure then...