Table Of ContentA Carl Zeiss interferometer in the thoroughly ventilated, air conditioned calibration room of the
Longworth Scientific Instrument Company, being used to test a vaporizer.
(By courtesy of Longworth Scientific Instrument Co. Ltd.)
Physics Applied
to Anaesthesia
second edition
D. W. Hill
M.Sc, PH.D., F.INST.P., F.I.E.E.
Reader in Medical Physics, Research
Department of Anaesthesics, Royal College of
Surgeons of England, and Institute of Basic
Medical Sciences, University of London
London: Butterworths
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1972
Suggested U.D.C. No. 53: 616-0895
ISBN 0 407 35751 3
Printed in Gt. Britain
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Foreword to First Edition
Shortly after the Research Department of Anaesthesics was founded
in the Royal College of Surgeons in 1957 under the chairmanship
of the late Professor R. F. Woolmer, Dr. Hill was appointed
lecturer in Physics. His book Physics Applied to Anaesthesia not only
reflects the range and depth of Dr. Hill's experience since his
appointment but also confirms the fundamental soundness of
Professor Woolmer's approach to the developing needs of Anaes
thesia. As Professor Woolmer's successor I am greatly honoured
that his pupil should have asked me to introduce his work.
Of recent years much has been written about the inadequacies
of medical education and the controversy has not been confined to
the undergraduate curriculum. Differences have arisen in the
postgraduate field and nowhere has this been more apparent than
in the specialty of Anaesthesia. The great technical advances of
the last decade have altered the pattern of the anaesthetist's duties
and increased the range of his responsibilities so much that there
has been a widespread demand for a radical change in training
programmes. In particular the curriculum for the Fellowship
examination in anaesthetics has been widely criticized and indeed
the need for revision has been fairly generally accepted for some
time. But there has also been an understandable reluctance to
upset an order which appeared both solid and incontrovertible.
However, the need for reform has finally prevailed and a decision
to revise the curriculum and the pattern of the examination has
now been taken. Shortly, Anatomy will lose its predominant
position in the primary examination to be replaced by Physics,
Clinical Measurement and Clinical Chemistry, subjects more
closely related to the needs of modern Anaesthesia. This decision
is undoubtedly the right one and marks a significant step in the
emancipation of the anaesthetist from a curriculum ordained more
by tradition and historical association than by present day require-
FOREWORD TO FIRST EDITION
ments. Many will agree that the reformers' case must have been
greatly strengthened by the substantial contributions made to
anaesthetics teaching and research by those physicists who have
chosen to work within the speciaHty.
Thus, Dr. Hill's book is opportune. Based on the series of lectures
on medical physics presented to the postgraduate students in the
Royal College of Surgeons he has expanded his material to ensure
that all aspects of his subject of interest to anaesthetists have been
covered. Dr. Hill combines an ease of expression with a wealth of
practical experience from which a substantial amount of this material
is derived. Scrutiny of his text reveals Dr. Hill's close association
with colleagues trained in many different scientific disciphnes
and emphasizes once again the advantages of a multi-disciphne
approach to research problems. The nature and extent of these
co-operative efforts augur well for the future of research in
Anaesthesia. Professor Woolmer's foresight in appointing a
physicist to his staff and encouraging him to become involved in
the general research activities of his department has been amply
justified.
Research Department of Anaesthetics
Royal College of Surgeons of England J. P. PAYNE
VI
Preface
During the four years that have elapsed between the publication of
the first and second editions of this book, there has been a consider
able consolidation in the teaching of physics as a subject for the
primary examination for the Fellowship examination in anaesthetics
of the Faculty of Anaesthetists of the Royal College of Surgeons of
England. Opportunity has been taken to revise the book and to
introduce additional material, for example, on computers. In this
connection, I would Uke to acknowledge a debt of gratitude to various
examiners, physicists providing courses for anaesthetists, readers of
the first edition and students on the primary courses run by the
Institute of Basic Medical Sciences and St. Thomas' Hospital for
helpful comments. Professor Payne and my colleagues in the
Research Department of Anaesthetics have continued to provide a
constant source of stimulation to investigate new methods and to
explain to doctors numerous concepts in physics.
The increase in size of this edition must inevitably mean that
readers will have to be selective to some extent. The questions on
physics set in the examination are of a practical nature, and students
are advised to seek the advice of senior colleagues as to which sections
of the book they should read in the greatest detail. For those wishing
to pursue particular topics it is hoped that adequate references have
been provided. Wherever possible, the SI system of units has been
used. Clearly the changeover to the general use of this system in
medical applications will take some time, if only for the fact that
the millimetre of mercury is still deeply enshrined for the measure
ment of blood pressure. Similarly, decisions will have to be taken
concerning the calibration of the pressure gauges on anaesthetic
machines.
In conclusion, I would Hke to express my best thanks to the staff
of the Medical Division of Butterworths who have given me loyal
support and paid great attention to detail.
D. W. HILL
vii
List of Abbreviations
Metre m Poise Ρ
Micrometre or micron μm Pound-force (similarly
Nanometre nm for kilogramme-force
Angstrom A etc) Ibf
Inch in Bar (10Myn/cm2) bar
Foot ft MiUibar mb
Square metre Atmosphere, standard atm
(similarly for square Atmosphere, absolute ata
centimetre, etc) m2 Atmosphere, gauge atg
Square inch (similarly MilUmetre of mercury mmHg
for square foot, etc) in2 (conventional) Torr
Cubic metre (similarly Joule J
for cubic centimetre. Erg erg
etc) m3 Kilowatt hour kWh
Cubic inch (similarly for Foot pound-force ft Ibf
cubic foot, etc) in3 Calorie cal
Litre 1 Kilocalorie kcal
Gallon gal Watt W
Second (time) s Horsepower hp
Minute (time) min Decibel dB
Hour h Degree Celsius °C
Day d Degree Kelvin Κ
Degree: minute: second Degree Fahrenheit op
(angle) o / // Candela cd
Radian rad Lumen Im
Radian per second rad/s Lux Ix
Cycle per second (hertz) Hz Hydrogen ion exponent pH
Revolution per minute rev/min Coulomb C
Gramme g Ampere A
Kilogramme kg Volt V
Pound lb Ohm Ω
Dyne dyn Farad F
Nev^ton Ν Henry Η
Stokes St Curie Ci
xiu
LIST OF ABBREVIATIONS
Prefixes denoting decimal multiples or sub-multiples
Indicating sub-multiples Indicating multiples
10-1 . deci d X 1012; tera Τ
10-2 . centi c X 109 . giga G
10-3 . jniUi m X 106 . jnega Μ
10-^ : micro μ X 103 : kilo k
10-^ : nano
η
10-12 . pico
Ρ
The symbols listed above are in accordance with British Standard
Specification 1991: Part 6:1963
XJV
Respiratory Symbols
1 Inspired gas
Ε Expired gas
A Alveolar gas
D Dead space gas
τ Tidal gas
Β Barometric
L Pulmonary
b Blood in general
a Arterial
c Capillary
ν Venous
V Mixed venous blood
F Fractional concentration in dry gas phase
Ρ Gas pressure in general
C Concentration in blood phase
S Saturation
R Respiratory exchange ratio
V Gas volume
V Gas volume per unit time
Q Blood volume per unit time
D Diffusing capacity
f Respiratory frequency
STPD Standard temperature, pressure, dry (0° C, 760 torr)
BTPS Body temperature, pressure, saturated with water
ATPS Ambient temperature, pressure, saturated with water
All the gas symbols are in subscript.
Dash above a symbol designates a mean value.
Examples:
FEN2 Fractional concentration of nitrogen in dry expired gas
PC02 Mean partial pressure of oxygen in capillary blood
PAO2—Pao2 Difference of the partial pressures of oxygen between
alveolar gas and arterial blood
XV
RESPIRATORY SYMBOLS
PB Barometric pressure
Cvco2 Concentration of carbon dioxide in venous blood
Svo2 Saturation of oxygen in mixed venous blood
Vi Inspired volume
VT Tidal volume
V02 Oxygen uptake, e,g, 245 ml STPD . min-^
DLCO Pulmonary diffusing capacity for CO,
e.g. 17 ml STPD . min-^ . torr-^
XV!
