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Lung volumes and lung mechanics in anesthetized children

Thorsteinsson, Adalbjörn LU (2001)
Abstract (Swedish)
Popular Abstract in Swedish

LUNGVOLYMER OCH LUNGMEKANIK HOS BARN UNDER ANESTESI Avhandlingen är avsedd att fylla luckor i vårt vetande vad gäller normal utveckling av lungvolymer och lungans elasticitet hos barn, från tidiga spädbarnstiden till tonåren. Speciellt har tidigare funnits en brist på data hos barn yngre än skolåldern. Undersökningarna gjordes i narkos och under muskelavslappning.



Mätningar:



· Absoluta lungvolymer mättes med en spårgasteknik (utsköljning av svavelhexafluorid).



· Förhållandet mellan luftvägstryck och lungvolym (respiratoriska systemets tryck/volym-diagram) mättes under en långsam utandning med gradvis sjunkande luftvägstryck ( 3 - 0... (More)
Popular Abstract in Swedish

LUNGVOLYMER OCH LUNGMEKANIK HOS BARN UNDER ANESTESI Avhandlingen är avsedd att fylla luckor i vårt vetande vad gäller normal utveckling av lungvolymer och lungans elasticitet hos barn, från tidiga spädbarnstiden till tonåren. Speciellt har tidigare funnits en brist på data hos barn yngre än skolåldern. Undersökningarna gjordes i narkos och under muskelavslappning.



Mätningar:



· Absoluta lungvolymer mättes med en spårgasteknik (utsköljning av svavelhexafluorid).



· Förhållandet mellan luftvägstryck och lungvolym (respiratoriska systemets tryck/volym-diagram) mättes under en långsam utandning med gradvis sjunkande luftvägstryck ( 3 - 0 kPa).



· I en annan studie gjordes försök att detaljanalysera tryck/volym-diagrammet och särskilja lungans inflytande från det som berodde på tryck från omgivande vävnader. Detta gjordes genom att inte bara mäta luftvägstryck, utan också trycket i matstrupen. Trycket i matstrupen används nämligen ofta hos vakna patienter, för att ge en uppfattning om trycket i lungsäcken.



· I en avslutande studie användes återigen spårgas, nu i ett försök att hitta den punkt under utandningen då luftvägsavstängning börjar uppträda.



Huvudfynd:



I. Absolut lungvolym, räknad per kg kroppsvikt, var mindre hos unga spädbarn än hos äldre barn.



II. Den mest uttalade kvalitativa förändringen (alltså med storleksfaktorn eliminerad) i tryck/volym-diagrammets utseende, inträffade under första levnadsåret.



III. I ryggläge förblev trycket i matstrupen positivt även när den långsamma utandningen fortskridit till låga lungvolyme. Trycket steg t.o.m. i vissa fall. När man ändå försökte göra en analys av lungans, respektive omgivande vävnaders betydelse för tryck/volym-diagrammet verkade omgivande vävnader ha liten inverkan (de svarade för cirka 1/10 av lungans inverkan, hos de yngsta).



IV. Luftvägsstängning syntes inträffa vid högre lungvolymer när mätningen gjordes efter en djup föregående inandning (till luftvägstrycket 3, i stället för 2 kPa).



Tolkning av fynden och möjliga kliniska konsekvenser:



I. Lungan är alltså mindre, i förhållande till vikten, hos små barn än hos större. Ändå vet vi från andras studier att syrgaskonsumtionen är större. Detta antyder att små barn kan ha minskad förmåga att tåla påfrestningar som tillfälligt avbrott i andningen (som ibland vid inledning av narkos), ökat syrgasbehov (som vid feber), och inskränkningar i lungans möjligheter att expandera (som vid vätska i lungsäcken eller uttalad lunginflammation).



II. Respiratoriska systemet hos unga spädbarn har mindre elastisk återfjädring än hos äldre individer. Detta återspeglar förmodligen ett lägre innehåll i lungorna av ämnet elastin.



III. När lungornas elasticitet skall bedömas hos respiratorbehandlade spädbarn krånglar man oftast bara till det om man försöker renodla lungans och omgivande vävnaders bidrag till respiratoriska systemets totala elasticitet. Man får vanligen en tillräckligt bra uppfattning om elasticiteten i lungorna genom att bara mäta ett tryck vid undersökningen, nämligen luftvägstrycket.



IV. Höga inandningstryck öppnar upp annars sammanfallna luftvägar, som sedan snabbt tycks stänga vid påföljande utandning. Fyndet kan tyda på att stora andetag ger slitskador i lungorna men måste tolkas med försiktighet. (Less)
Abstract
The thesis was intended to fill gaps in the knowledge regarding the normal development of lung volumes and lung mechanics in children, from young infancy to the mid-teens. In particular, data were previously lacking regarding pre-school children. The studies were done during anesthesia and muscle relaxation.



Measurements:



· Absolute lung volume was obtained with a tracer gas method (sulfur hexafluoride washout).



· Relation between airway pressure and lung volume (pressure-volume relation of the respiratory system) was asssessed during a slow intermittently interrupted expiration from 30 to 0 cm H2O of airway pressure.



· In a further study, attempts were made to... (More)
The thesis was intended to fill gaps in the knowledge regarding the normal development of lung volumes and lung mechanics in children, from young infancy to the mid-teens. In particular, data were previously lacking regarding pre-school children. The studies were done during anesthesia and muscle relaxation.



Measurements:



· Absolute lung volume was obtained with a tracer gas method (sulfur hexafluoride washout).



· Relation between airway pressure and lung volume (pressure-volume relation of the respiratory system) was asssessed during a slow intermittently interrupted expiration from 30 to 0 cm H2O of airway pressure.



· In a further study, attempts were made to separate P-V relations of the respiratory system into lung and chest wall components. This was done by analyzing esophageal pressure - that was taken to represent pleural pressure - in addition to airway pressure.



· In a final study, a tracer gas was again used, now in an attempt to find the point during expiration, where significant airway closure occurred.



Main findings:



I. Absolute lung volumes, per kg body weight, were less in young infants than in older children.



II. The most marked qualitative change (size factor eliminated) in the pressure-volume relation of the respiratory system occurred during infancy.



III. In the supine position, esophageal pressure paradoxically remained positive as expiration continued towards low lung volumes and even increased in some instances. When an attempt was made, anyway, to separately assess the various contributions to "total elastance", the chest wall contribution was relatively minor (about 1/10th in infants).



IV. The airway "closing phenomenon" occurred at a higher lung volume when the measurement maneuvre included a deep foregoing inspiration (to 30 rather than 20 cm H2O of airway pressure).



Interpretation and possible clinical implications of findings:



I. The lung is smaller, in relation to weight, in infants than in older subjects. Yet it is known from other studies that the rate of oxygen consumption at rest is greater. This suggests that infants will have reduced tolerance to stresses such as increased oxygen requirement (e.g. due to fever), apnea (e.g. during tracheal intubation), and restriction of lung capacity (e.g. resection of lung parenchyma, pneumonia, hydrothorax).



II. The respiratory system of small infants has less elastic recoil than that of older subjects. This probably reflects a low elastin content in the lungs, as described by others.



III. In the clinical assessment of mechanically ventilated infants, it is seldom worth the effort to separate P-V relations into lung and chest wall components - the simpler alternative of studying only respiratory system P-V relations will give an adequate picture of lung mechanics, if the infant is deeply sedated and temporarily relaxed. The same is probably true also for older children.



IV. High insufflation pressures will recruit otherwise collapsed airways, that will close early during the subsequent expiration. The relevance of this finding to conditions prevailing during regular breathing (mechanical or spontaneous) is, at most, speculative. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Sjöstrand, Ulf, Anestesi- och Intensivvårdskliniken, Akademiska Sjukhuset, Uppsala
organization
publishing date
type
Thesis
publication status
published
subject
keywords
sulfur hexafluoride, Anaesthesiology, lung volumes, lung compliance, Anesthesia: pediatric, functional residual capacity, intensive care, Anestesiologi, ventilation inhomogeneity, intensivvård, airway closure
pages
98 pages
defense location
Föreläsningssal 1, Centralblocket, Universitetssjukhuset i Lund
defense date
2001-06-08 13:00
ISBN
91-628-4727-9
language
English
LU publication?
yes
id
1d46b32d-b9b5-4ea9-b043-9013a0102423 (old id 41655)
date added to LUP
2007-08-01 16:22:16
date last changed
2016-09-19 08:45:16
@phdthesis{1d46b32d-b9b5-4ea9-b043-9013a0102423,
  abstract     = {The thesis was intended to fill gaps in the knowledge regarding the normal development of lung volumes and lung mechanics in children, from young infancy to the mid-teens. In particular, data were previously lacking regarding pre-school children. The studies were done during anesthesia and muscle relaxation.<br/><br>
<br/><br>
Measurements:<br/><br>
<br/><br>
· Absolute lung volume was obtained with a tracer gas method (sulfur hexafluoride washout).<br/><br>
<br/><br>
· Relation between airway pressure and lung volume (pressure-volume relation of the respiratory system) was asssessed during a slow intermittently interrupted expiration from 30 to 0 cm H2O of airway pressure.<br/><br>
<br/><br>
· In a further study, attempts were made to separate P-V relations of the respiratory system into lung and chest wall components. This was done by analyzing esophageal pressure - that was taken to represent pleural pressure - in addition to airway pressure.<br/><br>
<br/><br>
· In a final study, a tracer gas was again used, now in an attempt to find the point during expiration, where significant airway closure occurred.<br/><br>
<br/><br>
Main findings:<br/><br>
<br/><br>
I. Absolute lung volumes, per kg body weight, were less in young infants than in older children.<br/><br>
<br/><br>
II. The most marked qualitative change (size factor eliminated) in the pressure-volume relation of the respiratory system occurred during infancy.<br/><br>
<br/><br>
III. In the supine position, esophageal pressure paradoxically remained positive as expiration continued towards low lung volumes and even increased in some instances. When an attempt was made, anyway, to separately assess the various contributions to "total elastance", the chest wall contribution was relatively minor (about 1/10th in infants).<br/><br>
<br/><br>
IV. The airway "closing phenomenon" occurred at a higher lung volume when the measurement maneuvre included a deep foregoing inspiration (to 30 rather than 20 cm H2O of airway pressure).<br/><br>
<br/><br>
Interpretation and possible clinical implications of findings:<br/><br>
<br/><br>
I. The lung is smaller, in relation to weight, in infants than in older subjects. Yet it is known from other studies that the rate of oxygen consumption at rest is greater. This suggests that infants will have reduced tolerance to stresses such as increased oxygen requirement (e.g. due to fever), apnea (e.g. during tracheal intubation), and restriction of lung capacity (e.g. resection of lung parenchyma, pneumonia, hydrothorax).<br/><br>
<br/><br>
II. The respiratory system of small infants has less elastic recoil than that of older subjects. This probably reflects a low elastin content in the lungs, as described by others.<br/><br>
<br/><br>
III. In the clinical assessment of mechanically ventilated infants, it is seldom worth the effort to separate P-V relations into lung and chest wall components - the simpler alternative of studying only respiratory system P-V relations will give an adequate picture of lung mechanics, if the infant is deeply sedated and temporarily relaxed. The same is probably true also for older children.<br/><br>
<br/><br>
IV. High insufflation pressures will recruit otherwise collapsed airways, that will close early during the subsequent expiration. The relevance of this finding to conditions prevailing during regular breathing (mechanical or spontaneous) is, at most, speculative.},
  author       = {Thorsteinsson, Adalbjörn},
  isbn         = {91-628-4727-9},
  keyword      = {sulfur hexafluoride,Anaesthesiology,lung volumes,lung compliance,Anesthesia: pediatric,functional residual capacity,intensive care,Anestesiologi,ventilation inhomogeneity,intensivvård,airway closure},
  language     = {eng},
  pages        = {98},
  school       = {Lund University},
  title        = {Lung volumes and lung mechanics in anesthetized children},
  year         = {2001},
}