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An appropriate inspiratory flow pattern can enhance CO2 exchange, facilitating protective ventilation of healthy lungs

Walther Sturesson, Louise LU ; Malmkvist, G. LU ; Allvin, S.; Collryd, M.; Bodelsson, M. LU and Jonson, B. LU (2016) In British Journal of Anaesthesia 117(2). p.243-249
Abstract

Background In acute lung injury, CO2 exchange is enhanced by prolonging the volume-weighted mean time for fresh gas to mix with resident alveolar gas, denoted mean distribution time (MDT), and by increasing the flow rate immediately before inspiratory flow interruption, end-inspiratory flow (EIF). The objective was to study these effects in human subjects without lung disease and to analyse the results with respect to lung-protective ventilation of healthy lungs. Methods During preparation for intracranial surgery, the lungs of eight subjects were ventilated with a computer-controlled ventilator, allowing breath-by-breath modification of the inspiratory flow pattern. The durations of inspiration (TI) and... (More)

Background In acute lung injury, CO2 exchange is enhanced by prolonging the volume-weighted mean time for fresh gas to mix with resident alveolar gas, denoted mean distribution time (MDT), and by increasing the flow rate immediately before inspiratory flow interruption, end-inspiratory flow (EIF). The objective was to study these effects in human subjects without lung disease and to analyse the results with respect to lung-protective ventilation of healthy lungs. Methods During preparation for intracranial surgery, the lungs of eight subjects were ventilated with a computer-controlled ventilator, allowing breath-by-breath modification of the inspiratory flow pattern. The durations of inspiration (TI) and postinspiratory pause (TP) were modified, as was the profile of the inspiratory flow wave (i.e. constant, increasing, or decreasing). The single-breath test for CO2 was used to quantify airway dead space (VDaw) and CO2 exchange. Results A long MDT and a high EIF augment CO2 elimination by reducing VDaw and promoting mixing of tidal gas with resident alveolar gas. A heat and moisture exchanger had no other effect than enlarging VDaw. A change of TI from 33 to 15% and of TP from 10 to 28%, leaving the time for expiration unchanged, would augment tidal elimination of CO2 by 14%, allowing a 10% lower tidal volume. Conclusions In anaesthetized human subjects without lung disease, CO2 exchange is enhanced by a long MDT and a high EIF. A short TI and a long TP allow significant reduction of tidal volume when lung-protective ventilation is required. Clinical trial registration NCT01686984.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
capnography, intermittent positive pressure ventilation, pulmonary gas exchange
in
British Journal of Anaesthesia
volume
117
issue
2
pages
243 - 249
publisher
Macmillan
external identifiers
  • scopus:84992426945
  • wos:000383191500015
ISSN
0007-0912
DOI
10.1093/bja/aew194
language
English
LU publication?
yes
id
cdfd26a7-a388-468a-8d09-216d5f38990c
date added to LUP
2016-11-16 15:35:23
date last changed
2017-08-06 05:13:35
@article{cdfd26a7-a388-468a-8d09-216d5f38990c,
  abstract     = {<p>Background In acute lung injury, CO<sub>2</sub> exchange is enhanced by prolonging the volume-weighted mean time for fresh gas to mix with resident alveolar gas, denoted mean distribution time (MDT), and by increasing the flow rate immediately before inspiratory flow interruption, end-inspiratory flow (EIF). The objective was to study these effects in human subjects without lung disease and to analyse the results with respect to lung-protective ventilation of healthy lungs. Methods During preparation for intracranial surgery, the lungs of eight subjects were ventilated with a computer-controlled ventilator, allowing breath-by-breath modification of the inspiratory flow pattern. The durations of inspiration (T<sub>I</sub>) and postinspiratory pause (T<sub>P</sub>) were modified, as was the profile of the inspiratory flow wave (i.e. constant, increasing, or decreasing). The single-breath test for CO<sub>2</sub> was used to quantify airway dead space (V<sub>Daw</sub>) and CO<sub>2</sub> exchange. Results A long MDT and a high EIF augment CO<sub>2</sub> elimination by reducing V<sub>Daw</sub> and promoting mixing of tidal gas with resident alveolar gas. A heat and moisture exchanger had no other effect than enlarging V<sub>Daw</sub>. A change of T<sub>I</sub> from 33 to 15% and of T<sub>P</sub> from 10 to 28%, leaving the time for expiration unchanged, would augment tidal elimination of CO<sub>2</sub> by 14%, allowing a 10% lower tidal volume. Conclusions In anaesthetized human subjects without lung disease, CO<sub>2</sub> exchange is enhanced by a long MDT and a high EIF. A short T<sub>I</sub> and a long T<sub>P</sub> allow significant reduction of tidal volume when lung-protective ventilation is required. Clinical trial registration NCT01686984.</p>},
  author       = {Walther Sturesson, Louise and Malmkvist, G. and Allvin, S. and Collryd, M. and Bodelsson, M. and Jonson, B.},
  issn         = {0007-0912},
  keyword      = {capnography,intermittent positive pressure ventilation,pulmonary gas exchange},
  language     = {eng},
  month        = {08},
  number       = {2},
  pages        = {243--249},
  publisher    = {Macmillan},
  series       = {British Journal of Anaesthesia},
  title        = {An appropriate inspiratory flow pattern can enhance CO<sub>2</sub> exchange, facilitating protective ventilation of healthy lungs},
  url          = {http://dx.doi.org/10.1093/bja/aew194},
  volume       = {117},
  year         = {2016},
}