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Befuktning av inandningsgas i en ventilator
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2009 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Humidification of Inspiration Gas in a Ventilator (English)
Abstract [sv]

Långtidsbehandling med ventilator utan tillräcklig befuktning kan torka ut en patients luftvägar

med olika komplikationer som följd. Målet för detta examensarbete var att utveckla en ny teknik

för att befukta och värma inandningsgasen. Ett fungerande koncept och en prototyp som styrker

konceptet skulle tas fram.

Marknaden för befuktare studerades och de vanligast använda befuktningsmetoderna granskades

för att hitta svagheter som behövde åtgärdas. De två vanligaste befuktartyperna är Heated

Humidifier och Heat and Moisture Exchanger. Den främsta nackdelen med Heated Humidifier

var dess tendens att övermätta luften med kondensutfällning som följd, och med Heat and

Moisture Exhanger att inte tillräckliga fukt- och temperaturnivåer nåddes.

Därför togs en ny design fram med målet att kunna styra fukt och temperatur oberoende av

varandra. MATLAB och Simulink från The MathWorks användes för att modellera systemet.

Komponenter såsom sensorer för temperatur och fukt, värmare och befuktare utvärderades för

prototypen. För fukt- och temperaturmätning valdes standardsensorer medan värmaren var av

egen design. Nebulisatorn för fuktgenereringen hämtades från en hembefuktare. Styrsystemet

och användargränssnittet utvecklades i National Instruments LabView.

Arbetet resulterade i en fungerande prototyp bestående av befuktare, slangsystem och sensorer.

Oberoende styrning av temperatur och fuktighet uppnåddes även om en koppling mellan dessa

storheter var tydlig under övergångsförlopp. Godtagbara fysiologiska förhållanden nåddes utan

kondensutfällning i slangarna. Byte av nebulisatorn, förbättring av regleringen och en metod för

att upptäcka kondens är några av förbättringsförslagen.

Abstract [en]

Long term treatment with mechanical ventilation without proper humidification can dry a

patient’s airways which causes various complications. The aim of this Master’s thesis was to

develop a new technique to humidify and heat the inspired gas. The scope was limited to the

design of a new working concept and the creation of a prototype as proof-of-concept.

The ventilator humidifier market was studied, and the most prevalent humidification techniques

used today were assessed to identify the weaknesses that needed to be addressed. The two most

common designs for humidification were found to be the Heated Humidifier and the Heat and

Moisture Exchanger. The Heated Humidifier tended to oversaturate the inspired gas which led to

condensation in tubing, while the passive Heat and Moisture Exchanger could not deliver

sufficient amounts of heat or moisture.

Therefore, a design for actively controlling both heat and moisture delivery independently

through feedback control was created. MATLAB and Simulink from The MathWorks were used

to model the system and assess its feasibility. Various components for the prototype were

evaluated such as temperature and humidity sensors, heaters, and humidifiers. The choice of

sensors ultimately fell on off-the-shelf products while a custom heating solution was created. A

nebulizer unit extracted from a consumer grade room humidifier was used for moisture delivery.

The user interface and the control system were created on a computer using LabView from

National Instruments.

A functional prototype including humidifier, tubing, and sensors was developed. Independent

control of temperature and humidity was successfully attained, though the interdependence of the

two variables was not completely eliminated during transitions. Acceptable physiological

conditions were achieved without tube condensation. Changing the nebulizer, improving system

control and developing a condensation detection method are some of the suggested

improvements.

Place, publisher, year, edition, pages
2009.
Series
MMK 2009:06 MDA332
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-99480OAI: oai:DiVA.org:kth-99480DiVA: diva2:542303
External cooperation
Maquet Critical Care AB,Erik Cardelius
Uppsok
Technology
Supervisors
Examiners
Available from: 2012-07-31 Created: 2012-07-31 Last updated: 2012-07-31Bibliographically approved

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