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Computer simulation - a tool for optimisation of ventilator setting in critical lung disease

Uttman, Leif LU (2002)
Abstract (Swedish)
Popular Abstract in Swedish

Respiratorbehandling är nödvändig då en patient på grund av kronisk eller akut lungsjukdom inte själv kan upprätthålla ett adekvat gasutbyte. Bakomliggande orsaker kan vara kronisk obstruktiv lungsjukdom, lunginflammation, blodförgiftning eller trauma. Respiratorbehandling kan i sig orsaka ytterligare skador på redan sjuka eller skadade lungor. Bland de faktorer som har identifierats som farliga finns högt luftvägstryck och övertänjning av lungvävnad. I åtskilliga studier har man undersökt strategier för att minska risken att tillfoga patienter lungskada. Det har exempelvis utmynnat i att låg andetagsvolym nu anses vara en av de viktigaste beståndsdelarna i ett lungskyddande ventilationsmönster.... (More)
Popular Abstract in Swedish

Respiratorbehandling är nödvändig då en patient på grund av kronisk eller akut lungsjukdom inte själv kan upprätthålla ett adekvat gasutbyte. Bakomliggande orsaker kan vara kronisk obstruktiv lungsjukdom, lunginflammation, blodförgiftning eller trauma. Respiratorbehandling kan i sig orsaka ytterligare skador på redan sjuka eller skadade lungor. Bland de faktorer som har identifierats som farliga finns högt luftvägstryck och övertänjning av lungvävnad. I åtskilliga studier har man undersökt strategier för att minska risken att tillfoga patienter lungskada. Det har exempelvis utmynnat i att låg andetagsvolym nu anses vara en av de viktigaste beståndsdelarna i ett lungskyddande ventilationsmönster. Det finns emellertid så många kombinationer av respiratorinställningar att det är omöjligt att resonera sig fram till en optimal inställning.



Det övergripande målet med denna avhandling var att utveckla och utvärdera en metod för datorsimulering av respiratorbehandling baserad på den enskilde patientens fysiologi. För att nå detta mål krävdes utveckling av metoder för analys av lungfunktion samt fördjupade kunskaper om hur en omställning av respiratorn påverkar gasutbytet.



Det kunde bekräftas att datorsimulering gör det möjligt att förutspå hur omställningar av viktiga respiratorparametrar påverkar luftvägstryck och gasutbyte. Den omfattande analys av lungfunktionen som presenteras kan ge viktig information om patientens komplexa fysiologi vid kritisk lungsjukdom, prognos och svar på behandling. Resultaten anger vägar för fortsatt utveckling av ett system för ”målorienterad respiratorinställning”. Denna princip innebär att läkaren anger vilka mål som skall uppnås med behandlingen. Datorn ger beslutsstöd genom att beräkna hur respiratorn skall ställas in för att nå målen. (Less)
Abstract
Increasing attention is paid to mechanical ventilation as one cause behind aggravation of lung injury. Lung protective ventilation can be achieved e.g. by minimising tidal lung collapse and re-expansion and by the use of small tidal volume allowing some degree of permissive hypercapnia. The ventilator and the sick lung comprise a very complex system. Identification of a ventilator setting that with respect to respiratory rate, tidal volume, I:E ratio, PEEP, etc is optimal with respect to desired physiological effects is therefore difficult.



The main objective behind this thesis was to develop and validate a system for computer simulation of respiratory mechanics and gas exchange that allows prediction of physiological... (More)
Increasing attention is paid to mechanical ventilation as one cause behind aggravation of lung injury. Lung protective ventilation can be achieved e.g. by minimising tidal lung collapse and re-expansion and by the use of small tidal volume allowing some degree of permissive hypercapnia. The ventilator and the sick lung comprise a very complex system. Identification of a ventilator setting that with respect to respiratory rate, tidal volume, I:E ratio, PEEP, etc is optimal with respect to desired physiological effects is therefore difficult.



The main objective behind this thesis was to develop and validate a system for computer simulation of respiratory mechanics and gas exchange that allows prediction of physiological effects of resetting the ventilator. To reach this objective, methods for characterisation of lung physiology, which require little or no disturbance of the breathing pattern, were developed. Complementary studies of how gas exchange is affected by ventilator setting were performed.



Longer time for equilibration between inspired and alveolar gas decreased airway dead space. When, in acute lung injury, PaO2 increased in response to PEEP, alveolar dead space decreased and vice versa. The hypothesis that mechanical behaviour and CO2 elimination after resetting respiratory rate and tidal volume could be predicted by simulation in healthy pigs was confirmed. Further, the hypothesis that immediate effects of moderate PEEP increments on mechanics and CO2 elimination in patients with acute lung injury could be predicted by simulation was also confirmed. Future development of the lung model used for simulation was outlined so as to include how time for gas equilibration affects gas exchange and to account for non-linear elastic properties. Iterative simulation may be a tool in future goal-oriented ventilation strategies. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Hedenstierna, Göran
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Adult · Swine, Computer Simulation ·Artificial Respiration ·Pulmonary Gas Exchange · Respiratory Dead Space · Respiratory Mechanics · Respiratory Distress Syndrome, Physiology, Fysiologi
pages
102 pages
publisher
Leif Uttman, Dept. of Clinical Physiology, University Hospital, SE-221 85 Lund, Sweden,
defense location
Föreläsningssal 1, University Hospital, Lund
defense date
2002-12-11 10:15
ISBN
91-628-5443-7
language
English
LU publication?
yes
id
6c794ced-22b1-4f58-ad2f-0eec70b04020 (old id 465210)
date added to LUP
2007-10-08 11:13:49
date last changed
2016-09-19 08:45:06
@misc{6c794ced-22b1-4f58-ad2f-0eec70b04020,
  abstract     = {Increasing attention is paid to mechanical ventilation as one cause behind aggravation of lung injury. Lung protective ventilation can be achieved e.g. by minimising tidal lung collapse and re-expansion and by the use of small tidal volume allowing some degree of permissive hypercapnia. The ventilator and the sick lung comprise a very complex system. Identification of a ventilator setting that with respect to respiratory rate, tidal volume, I:E ratio, PEEP, etc is optimal with respect to desired physiological effects is therefore difficult.<br/><br>
<br/><br>
The main objective behind this thesis was to develop and validate a system for computer simulation of respiratory mechanics and gas exchange that allows prediction of physiological effects of resetting the ventilator. To reach this objective, methods for characterisation of lung physiology, which require little or no disturbance of the breathing pattern, were developed. Complementary studies of how gas exchange is affected by ventilator setting were performed.<br/><br>
<br/><br>
Longer time for equilibration between inspired and alveolar gas decreased airway dead space. When, in acute lung injury, PaO2 increased in response to PEEP, alveolar dead space decreased and vice versa. The hypothesis that mechanical behaviour and CO2 elimination after resetting respiratory rate and tidal volume could be predicted by simulation in healthy pigs was confirmed. Further, the hypothesis that immediate effects of moderate PEEP increments on mechanics and CO2 elimination in patients with acute lung injury could be predicted by simulation was also confirmed. Future development of the lung model used for simulation was outlined so as to include how time for gas equilibration affects gas exchange and to account for non-linear elastic properties. Iterative simulation may be a tool in future goal-oriented ventilation strategies.},
  author       = {Uttman, Leif},
  isbn         = {91-628-5443-7},
  keyword      = {Adult · Swine,Computer Simulation ·Artificial Respiration ·Pulmonary Gas Exchange · Respiratory Dead Space · Respiratory Mechanics · Respiratory Distress Syndrome,Physiology,Fysiologi},
  language     = {eng},
  pages        = {102},
  publisher    = {ARRAY(0xb765b18)},
  title        = {Computer simulation - a tool for optimisation of ventilator setting in critical lung disease},
  year         = {2002},
}