Nunn's Applied Respiratory Physiology

663 Pages·1993·0.21 MB·English

by  J. F. Nunn (Auth.)

Nunn's Applied Respiratory Physiology
Fourth edition
J.F. Nunn
MD, DSc, PhD, FRCS, FRCA, FANZCA(Hon), FFARCSI(Hon)
Formerly Head of Division of Anaesthesia, Medical Research Council Clinical Research Centre;
Honorary Consultant Anaesthetist, Northwick Park Hospital, Middlesex; Previously, Professor of
Anaesthesia, University of Leeds; Dean of Faculty of Anaesthesia, Royal College of Surgeons of England
Foreword by John W. Severinghaus
Cardiovascular Research Institute, San Francisco; Department of Anaesthetics, University of California
S J U T T E R W O R TH
Ε I Ν Ε Μ Α Ν Ν
Butterworth-Heinemann Ltd
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vX^ A member of the Reed Elsevier group
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TOKYO TORONTO WELLINGTON
First published 1969
Reprinted 1971 (twice), 1972, 1975
Second edition 1977
Reprinted 1978, 1981
Third edition 1987
Reprinted 1989
Fourth edition 1993
© Butterworth-Heinemann Ltd 1993
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ISBN 0 7506 1336 X
Printed and bound in Great Britain by The University Press, Cambridge
Hypnos and the Flame
(original photograph courtesy of Dr John W. Severinghaus)
Foreword to the fourth edition
In every era, whether the Reformation or the genetic revolution, fad captures the
crowd. Protestant theologian Rheinhold Niebuhr depicted the role of the remnant
to be preservation of culture and tradition (his neo-orthodoxy), as the Western
world largely turned to secular humanism. During the quarter century since John
Nunn's book first appeared, the drama of clones, codons, channels and genomes
has swept blood and gas under the rug in medical schools, cornered the funds and
co-opted a generation of inquiry. Respiratory research, proceeding in relative
obscurity, seldom seen in Science, Nature or The Times, nevertheless accounts for
much of the 5000 pages a year now published by the Journal of Applied Physiology.
For students entering anaesthesia, ill-prepared to manage pulmonary problems,
Applied Respiratory Physiology fulfils the role of the remnant. What a rarity! A
single-authored medical text, thrice updated, the essence needed by newcomers
and old-timers alike, extracted from the world's literature without assistance,
barely increasing its bulk, while keeping it clear, concise and comprehensive. Who
else would be the only one to catch his own minor Latin translation error in an
earlier edition?
With John Nunn's update of lung science, let me refresh the 'Flame for Hypnos'
metaphor, in which Flame stood for learning, facts and science. CP. Snow's
two-cultures, humanities and sciences, arose, in Robert Pirsig's view*, when the
primacy of Quality, as defended in the dialogues of Plato by Phaedrus a sophist,
collapsed under Socrates' weighty support of Truth and Fact, the roots of science.
Until it conceived nuclear fission, Science could largely ignore Ethics. Now the two
cultures must be rejoined if we would survive. So too, as the tools of Hypnos
matured, a vigilant remnant unmasked slights of Quality that had been too long
condoned. New emphases emerged in anaesthesiology: Safety, Quality Control and
Continuing Medical Education. The gain with each new device or drug wants new
skill and care, that the offspring of Hypnos might excel in every action and remove
each risk to life and health. These two views of reality, Sophists' Quality and
Socratic Truth, have come to be recognized as co-essential. Thus may Hypnos
restore the Hellenic cloak of Phaedrus.
John W. Severinghaus
*Zen and the Art of Motorcycle Maintenance.
xiii
Preface to the first edition
Clinicians in many branches of medicine find that their work demands an extensive
knowledge of respiratory physiology. This applies particularly to anaesthetists
working in the operating theatre or in the intensive care unit. It is unfortunately
common experience that respiratory physiology learned in the preclinical years
proves to be an incomplete preparation for the clinical field. Indeed, the emphasis
of the preclinical course seems, in many cases, to be out of tune with the practical
problems to be faced after qualification and specialization. Much that is taught does
not apply to man in the clinical environment while, on the other hand, a great many
physiological problems highly relevant to the survival of patients find no place in
the curriculum. It is to be hoped that new approaches to the teaching of medicine
may overcome this dichotomy and that, in particular, much will be gained from the
integration of physiology with clinical teaching.
This book is designed to bridge the gap between pure respiratory physiology and
the treatment of patients. It is neither a primer of respiratory physiology nor is it a
practical manual for use in the wards and operating theatres. It has two aims.
Firstly, I have tried to explain those aspects of respiratory physiology which seem
most relevant to patient care, particularly in the field of anaesthesia. Secondly, I
have brought together in review those studies which seem to me to be most relevant
to clinical work. Inevitably there has been a preference for studies of man and
particular stress has been laid on those functions in which man appears to differ
from laboratory animals. There is an unashamed emphasis on anaesthesia because I
am an anaesthetist. However, the work in this speciality spreads freely into the
territory of our neighbours.
References have been a problem. It is clearly impracticable to quote every work
which deserves mention. In general I have cited the most informative and the most
accessible works, but this rule has been broken on numerous occasions when the
distinction of prior discovery calls for recognition. Reviews are freely cited since a
book of this length can include only a fraction of the relevant material. I must
apologize to the writers of multi-author papers. No one likes to be cited as a
colleague, but considerations of space have precluded naming more than three
authors for any paper.
Chapters are designed to be read separately and this has required some
repetition. There are also frequent cross-references between the chapters. The
principles of methods of measurement are considered together at the end of each
chapter or section.
XV
xvi Preface to the first edition
In spite of optimistic hopes, the book has taken six years to write. Its form,
however, has evolved over the last twelve years from a series of lectures and
tutorials given at the Royal College of Surgeons, the Royal Postgraduate Medical
School, the University of Leeds and in numerous institutions in Europe and the
United States which I have been privileged to visit. Blackboard sketches have
gradually taken the form of the figures which appear in this book.
The greater part of this book is distilled from the work of teachers and
colleagues. Professor W. Melville Arnott and Professor K. W. Donald introduced
me to the study of clinical respiratory physiology and I worked under the late
Professor Ronald Woolmer for a further six years. My debt to them is very great. I
have also had the good fortune to work in close contact with many gifted colleagues
who have not hesitated to share the fruits of their experience. The list of references
will indicate how much I have learned from Dr John Severinghaus, Professor
Moran Campbell, Dr John Butler and Dr John West. For my own studies, I
acknowledge with gratitude the part played by a long series of research fellows and
assistants. Some fifteen are cited herein and they come from eleven different
countries. Figures 2, 3, 6, 11 and 15 [Figures 5.3, 3.4 and 3.1 in the fourth edition]
which are clearly not my blackboard sketches, were drawn by Mr H. Grayshon
Lumby. I have had unstinted help from librarians, Miss M. P. Russell, Mr W. R.
LeFanu and Miss Ε. M. Reed. Numerous colleagues have given invaluable help in
reading and criticizing the manuscript.
Finally I must thank my wife who has not only borne the inevitable preoccupa-
tion of a husband writing a book but has also carried the burden of the paper work
and prepared the manuscript.
J.F.N.
Preface to the fourth edition
Respiratory physiology as taught to my generation of medical students in the 1940s
bore little relevance to clinical practice. The situation was transformed by the major
war-time advances achieved by the American workers Fenn, Rahn, Otis and Riley,
and then presented in spectacular fashion to the medical public in The Lung by
Comroe and his co-authors. The first edition of Applied Respiratory Physiology was
written at the time when measurement of arterial Pco and Po had just become
2 2
practicable in the clinical field. The new understanding of the factors which control
these important quantities in health and disease could now be applied, and those
who practised acute medicine in the 1950s will remember what an immense advance
this was. The first edition was written to transmit this new knowledge to a wider
clinical sphere. It was an exciting time and clinical respiratory physiology was then
in the forefront of progress, enjoying the glamour which is now the preserve of
molecular biology.
Respiratory research did not stand still but moved into new and exciting areas,
which required a second edition, written in the mid 1970s. Among the new
developments were the identification of the central chemoreceptors, improved
understanding of mechanisms of pulmonary oedema, recognition of the role of free
radicals in oxygen toxicity and elucidation of further non-respiratory functions
of the lungs. It had become clear that reduction in functional residual capacity
underlay many of the abnormalities of pulmonary function during anaesthesia and
it had been shown that changes in levels of 2,3-diphosphoglycerate could displace
the oxyhaemoglobin dissociation curve. Respiratory physiologists were moving into
novel fields which often paralleled those in other disciplines of medicine.
New fields of research continued to emerge and the third edition, written in the
mid 1980s, required a change in format with the first part of the book devoted to
basic principles, now with a full chapter on the non-respiratory functions of the
lung. There were major advances in our understanding of the medullary neurons
concerned with breathing, and in the distribution of ventilation and perfusion to
respiratory units of different ventilation/perfusion ratios. The second part of the
book was devoted to applications and permitted a much more detailed and
systematic discussion of new advances in understanding of applied situations. In
every section of the applications there were major advances to review. They
included an explosion of knowledge in the role of pharyngeal obstruction in the
respiratory disorders of sleep, and in our understanding of exercise at extreme
altitude. There were many new developments in artificial ventilation, recognition
xvii
xviii Preface to the fourth edition
of the histology of pulmonary barotrauma and a novel approach to extracorporeal
removal of carbon dioxide. There was a great expansion in understanding the role
of free radicals in oxygen toxicity, and this was associated with important studies of
the mechanisms of pulmonary tissue damage in the adult respiratory distress
syndrome.
Since the third edition, the pace of respiratory research has quickened and
diversified to an extent, much of which could not have been anticipated. In
particular, how many of us would have guessed that nitric oxide would play such a
crucial role in pulmonary vasomotor control and that this highly reactive free-
radical gas would appear to have an important role in therapy of the adult
respiratory distress syndrome? The relationship between oxygen consumption and
delivery in disease has become a valuable field of research, and there have been
further important developments in the mechanisms and significance of pharyngeal
obstruction in sleep and anaesthesia. The pulse oximeter has ushered in a new era
of continuous clinical monitoring of oxygenation. The simulated laboratory ascent
of Everest has provided much detail of high altitude physiology and confirmed the
earlier field studies of West, Pugh and others. We now have the earliest intimations
of respiratory studies by West during prolonged weightlessness in space. Un-
derstanding of the pulmonary effects of anaesthesia have been revolutionized by
the outstanding tomographic studies by Hedenstierna and his colleagues in
Stockholm. Milic-Emili has again broken new ground, this time in the time-
dependence of lung mechanics due to viscoelastic flow in lung tissue. Finally, I
thought the time was ripe to present a chapter on the atmosphere, which is basic to
respiration and can no longer be taken for granted as an unchanging entity.
The formidable task of assimilation of this new knowledge has been helped by an
unprecedented explosion in major books on respiration, including the Handbooks
of the American Physiological Society, the immense Scientific Foundation (Crystal
and West) and the many volumes on specific topics produced by Marcel Dekker.
The total shelf length of these volumes is measured in metres, and condensation of
the essential information into a book of this length has been a daunting task.
I wish to express my personal gratitude to all those who have helped me in my
understanding of the many new concepts, and in particular to Michael Halsey,
David and Barbara Royston, Warren Zapol, Goran Hedenstierna, John Severing-
haus, Bryan Marshall, Milic-Emili, John West and Gordon Drummond. British
Airways kindly reviewed the information on commercial flying. Erwald Weibel has
again provided wonderful electron micrographs and Louise Perks has translated
concepts into intelligible diagrams. I am specially indebted to John Severinghaus
for contributing his arresting Foreword to the fourth edition to cap his Foreword to
the first edition of twenty-four years ago. Finally and not least my dear wife has
once again borne the burden of a preoccupied husband immersed in papers and
word-processors for an inordinate length of time. 1
J.F.N.
Chapter 1
The atmosphere
The atmosphere of the earth has a composition and pressure which is unique in the
solar system. It has evolved by a complex chain of circumstances in which biological
influences have been of major importance. In turn many species, including Homo
sapiens, have evolved to derive maximal benefit from the present state of the
gaseous environment. However, major changes in the atmosphere now appear to
be taking place, largely as a result of human intervention. If these changes continue
into the future, there will inevitably be a deterioration of quality of life and survival
for some but not all species.
Pressure and composition of the atmosphere
Sea level pressure is 101.3 kPa (760 mmHg or 1033 cmH 0). The pressure declines
2
with increasing altitude and Table 15.1 shows the standardized relationship
between pressure and altitude, from which there are some important exceptions
(page 339). The troposphere has a relatively constant composition and extends
from sea level to the tropopause, which is at an altitude of 17 km at the equator and
6-8 km at the poles. The mean altitude is about 11 km, where the pressure is 23 kPa
(173 mmHg). Temperature also falls progressively with altitude in the troposphere
to reach a minumum of -56°C at the tropopause. This provides the cold trap
beyond which the escape of water vapour is greatly curtailed. Above the tropo-
pause is the stratosphere, the lower part of which includes the operating altitudes of
jet airliners. Temperature rises with altitude in the stratosphere to reach a
temperature close to 0°C at the stratopause (50 km). The stratosphere is exposed to
both ionizing radiation and intense ultraviolet radiation which causes photodisso-
ciation of gases. This results in many chemical changes that cannot occur in the
troposphere, including, for example, the formation of ozone.
The composition of the earth's atmosphere is quite unlike that of any other body
in the solar system (Table 1.1). Small bodies, such as Mercury and most of the
planets' satellites, have a gravitational field which is too weak for the retention of
any atmosphere at all (Figure 1.1). The large planets (Jupiter, Saturn, Uranus and
Neptune) have a gravitational field which is sufficiently strong to retain all gases,
including helium and hydrogen, thereby ensuring the retention of a reducing
3
4 The atmosphere
Table 1.1 Composition of the atmosphere of the earth (by volume in dry gas)
Nitrogen 78.084% Neon 18.18 p.p.m.
Oxygen 20.946% Helium 5.24 p.p.m.
Argon 0.934% Methane 1.70 p.p.m.
Carbon dioxide 0.035% Krypton 1.14 p.p.m.
Hydrogen 0.50 p.p.m.
Nitrous oxide 0.28 p.p.m.
Ozone 0.10* p.p.m.
Xenon 0.086 p.p.m.
CFCs 0.003 p.p.m.
*Very variable
1000 •
Jupiter
-130°C
Saturn
100 -\ too hot too cold -185°C
< Neptune
-200° C
Î
10 -\ hydrogen
Uranus
retained
-215°C
Earth
15°C
1 -4 Venus
480° C
Mars
φ -50°C
0.H Mercury
' 430°C Titan
^ <V-180°C Ο
0.01 -4 Ô Ganymede ^ ^ Triton
-190°C ?-240°C
Moon
atmosphere
Pluto
lost 9 A
-230°C
0.001
0.3 10 50
Distance from sun - relative to Earth
Figure 1.1 The planets and some of their larger satellites, plotted according to distance from the sun
(abscissa) and mass (ordinate), both scales being logarithmic and relative to Earth. Mean surface
temperatures are shown. Potential for life as we know it exists only within the parallelogram surrounding
the earth.
atmosphere. The gravitational field of Earth is intermediate, resulting in a
differential retention of the heavier gases (oxygen, carbon dioxide and nitrogen),
while permitting the escape of hydrogen and helium. This is crucial to the
development of an oxidizing atmosphere. Water vapour (molecular weight only 18)
would be lost from the atmosphere were it not for the cold trap at the tropopause.