Upper airway reflexes and Anaesthesia

286 Pages·2015·14.53 MB·English

Upper airway reflexes and Anaesthesia
A Thesis submitted to the University of Leicester for the degree of
Doctor of Medicine.
Dr Jeremy Adam Langton
Senior Lecturer in Anaesthesia.
UMI Number: U555196
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Contents
Summary.........................................................................................5
Publications & presentations.........................................................6
Declaration......................................................................................9
Acknowledgements......................... 10
List of Figures........................... 11
List of Tables..................................................................................13
List of abbreviations......................................................................15
Chapter 1.......................................................................................17
The importance of the Larynx and Upper airwav reflexes to
anaesthesia
i) Upper airway reflexes and anaesthesia.
ii) The consequences of laryngospasm in the peri-operative period
iii) Anaesthetic agents and their effects on the reactivity of the upper
airway.
iv) The function of the larynx in the peri-operative period
Chanter 2.......................................................................................44
Upper airwav structure and function
i) Anatomy of the upper airway
ii) Upper airway physiology - Reflexes and receptors of the upper
respiratory tract.
Chapter 3 .......................................................................................81
Background to the thesis
i) Historical development of methods to measure the sensitivity of
upper airway reflexes.
ii) NH3 vapour : chemistry and toxicology.
Chanter 4.......................................................................................95
Methodology
i) Development and description of the method used to measure the
sensitivity of upper airway reflexes.
ii) Development of the method to measure the movements of the vocal
cords on induction of anaesthesia.
Chanter 5.......................................................................................137
Study 5.1 ;The effect of age on the sensitivity of upper airway reflexes.
Chapter 6........................................................................................148
Smoking and Anaesthesia
Study 6.1 ; The effect of cigarette smoking on the sensitivity of upper
airway reflexes and the changes that occur on stopping
smoking for 24hr.
Study 6.2; The effect on the sensitivity of upper airway reflexes of
stopping smoking for 25 days.
Chapter 7........................................................................................183
The effects of benzodiazepines on the sensitivity of upper airwav
reflexes.
Study 7.1: The effect of oral diazepam on the sensitivity of upper airway
reflexes.
Study 7.2: The effect of intravenous Diazemuls, midazolam and
flumazenil on the sensitivity of upper airway reflexes.
Chapter 8........................................................................................209
Study 8.1; The effect of ethyl alcohol on the sensitivity of upper airway
reflexes.
Chapter 9........................................................................................224
Study 9.1; The effect of breathing Entonox on the sensitivity of upper
airway reflexes.
Chapter 10.......................................................................................236
Study 10.1: Vocal cord movements on induction of anaesthesia using
either thiopentone or propofol.
Chapter 11.......................................................................................247
Conclusions & clinical recommendations.
Chanter 12.......................................................................................255
References and published papers.
4
Summary
In this thesis I describe the importance of upper airway reflexes to
anaesthesia and discuss the anatomy and physiology relating to normal
upper airway function and protective airway reflexes.
The measurement of upper airway reflexes has not previously been fully
investigated in humans and I describe the background to the measurement
of the sensitivity of upper airway reflexes and outline a technique to
measure the sensitivity of upper airway reflexes. Using this technique I
have explored the changes in the sensitivity of upper airway reflexes that
occur due to ageing and following adroinistration of drugs. Smokers are
loiown to have an increased incidence of coughing and laryngospasm on
induction of anaesthesia. The effect of cigarette smoking and the changes
in the sensitivity of upper airway reflexes which occur on stopping
smoldng were investigated. Benzodiazepines are commonly used for
premedication and intravenously to produce sedation, the effects of these
drugs on the sensitivity of upper airway reflexes was examined as well as
the effect of the reversal agent flumazenil. Patients who have consumed
ethyl alcohol may readily aspirate gastric contents with fatal consequences.
The effect of ethyl alcohol on the sensitivity of upper airway reflexes is
measured and the relevance to anaesthetists providing emergency
anaesthesia is discussed. The inhalation of nitrous oxide and oxygen
mixtures is frequently used for analgesic purposes in groups of patients
known to have full stomachs and who are at risk from aspiration of gastric
contents. I have studied the effects of nitrous oxide and oxygen mixtures
on upper airway reflexes. The final chapter of this thesis uses a fibre-optic
method of measuring the movements of the vocal cords on induction of
anaesthesia, to examine the actions of two commonly used anaesthetic
induction agents on the sensitivity of upper airway reflexes.
Publications
Parts of this thesis have already been presented to
meetings and published as abstracts and as full papers as
detailed below, these full papers are included in chapter 12.
Abstracts
1 Langton J.A., Wilson L, Barker P., Smith G.
Preliminary observations of vocal cord movements
following induction of anaesthesia with thiopentone or
propofol. Br J Anaesth 1990;65:4:582P-583P.
2 Langton J.A., Murphy P., Barker P., Smith G.
A portable method to assess upper airway reactivity.
Br J Anaesth 1991;67;5:648P-649P.
3 Murphy P., Langton J.A., Barker P., Smith G.
An investigation of the effect of oral diazepam on upper
airway reactivitv.Br J Anaesth 1991;67;5:660P-661P.
4. Erskine R., Murphy P., Langton J.A.
The effect of age on the sensitivity of upper airway
reflexes.Br J Anaesth 1992:69:5:538P-539P.
5 Erskine R.J., Murphy P.J., Langton J.A.
The effect of stopping smoldng on upper airway reflexes.
Br J Anaesth 1993:70:4:478P.
6 Murphy P., Ersldue R., Rabey P., Langton J.A.
The effect of Entonox on the sensitivity of upper airway
reflexes. Obstetric Anaesthetists Association. Sept 1992.
7 Erskine R., Murphy P., Langton J.A.
Measurement of the sensitivity of upper airway reflexes.
Roval Society of Medicine Breathing Club 1992.
Erskine R., Murphy P., Langton J.A., Smith G.
Upper airway reactivity in smokers and non-smokers.
Abstract 197, World Congress of Anaesthesiologists
The Hague June 1992.
Full Publications
1 Barker P., Langton J.A., Wilson LG., Smith G.
Movements of the vocal cords on induction of
anaesthesia with thiopentone or propofol.
Br J Anaesth 1992;69:23-25.
2 Langton J.A.,Murphy P.,Barker P., Key A.,Smith G.
Measurement of the sensitivity of upper airway reflexes.
Br J Anaesth 1993:70:126-130.
3 Murphy P., Langton J.A., Barker P., Sndth G.
The effect of oral diazepam on the sensitivity of
upper airway reflexes.Br J Anaesth 1993:70:131-134.
Erskine R. J., Murphy P. J., Langton J.A., Smith G.
Effect of age on the sensitivity of upper airway reflexes.
BrJ Anaesth 1993;70:574-575.
5 Murphy P., Erskine R.; Langton J.A.
The effects of intravenous Diazemuls, midazolam and
flumazenil on the sensitivity of upper airway reflexes.
Anaesthesia 1993 (in press).
6 Erskine R., Murphy P., Langton J.A.
The effects of ethyl alcohol on the sensitivity of upper
airway reflexes. Alcohol and Alcoholism 1993 (in press).
7 Langton J.A., Erskine R., Murphy P.
The effect of chronic cigarette smoldng and stopping
smoldng, on the sensitivity of upper airway reflexes.
Br J Anaesth (submitted).
Langton J.A., Murphy P., Ersldne R.
The effects of entonox on the sensitivity of upper airway
reflexes, (in preparation).