Forensic Science, 6 (1975) 229-234 0 Elsevier Sequoia S.A., Lausanne -
229 Printed
in the Netherlands
THE SIGNIFICANCE OF THE POSTMORTEM DISCOVERY GASTRIC CONTENTS IN THE AIR PASSAGES BERNARD
H. KNIGHT
The Welsh National (Gt. Britain) (Received
OF
November
School
of Medicine,
21, 1975;
accepted
Institute December
of Pathology,
Royal
Infirmary,
Cardiff
19,1975)
SUMMARY The significance of the finding of gastric contents in the air passages at postmortem examination is discussed and references quoted to indicate that without clinical corroboration of aspiration of gastric contents, the purely autopsy diagnosis of such aspiration is to be regarded with reservation. In a series of routine medicolegal autopsies, gastric contents were shown to be present in a quarter of all cases, irrespective of the cause of death. This figure also appeared to hold for autopsies upon infants and the special dangers of ascribing infant victims of the “sudden death in infancy syndrome” to the aspiration of vomit is pointed out.
Terms such as “aspiration of vomit”, “inhalation of stomach contents” etc., are quite frequently employed as the sole cause of death in certifying cases after autopsy. These are not necessarily synonymous with choking on food, the occurrence of which is rarely in doubt, especially in the senile and mentally defective. The essential difference is that the latter condition refers to blockage of the glottis, larynx or trachea by large masses of food which are in the process of being swallowed, as opposed to the regurgitation of gastric contents, which is the reflux of food that has already been swallowed. That death can occur from the latter condition is not denied, but it is the frequency with which it genuinely occurs and the standard of its proof by the pathologist, which is in dispute. The author of this paper considers that as a primary cause of death, terms such as “inhalation of stomach contents” are considerably over-employed in situations where there is no corroborative clinical evidence. This applies particularly to deaths of small infants, notably in the “‘sudden infant death syndrome”. Here the results may be particularly unfortunate, in that some coroners feel obliged to hold an inquest, thus reinforcing the guilt feelings of the parents.
HISTORICAL
ASPECTS
Disregarding for a moment the 2 different types of airway blockage mentioned above, “choking on food” is well documented in medical history,
230
even if very uncritically recorded. Four centuries before Christ, Hippocrates warned that “it is bad for drinking to provoke a slight cough or for swallowing to be forced”. Anacreon, the Greek poet, was alleged to have died from inhalation of a grape seed even earlier than the time of Hippocrates. In Britain, Godwin, Earl of Wessex, on being accused by Edward the Confessor in 1053 A.D. of having murdered Alfred the Etheling, protested his innocence saying “if I am guilty, may this bread choke me”. He ate the bread and fell down in a fit and died - possibly natural justice. The English poet, Humphrey Gilbert, died in 1583 from choking caused by a piece of mutton in his glottis. It will be noted that all these cases were based upon clinical observation and the author submits that they are more valid than if the cause of death had been declared after an autopsy without antemortem observation. More recent experiences have cast doubts on the validity of finding gastric contents in the main air passages. Such material may arrive in the respiratory tubes by one of 4 ways. (i) Diversion into the larynx during swallowing - “food going the wrong way”. (ii) True antemortem regurgitation, sometimes a sufficiently long time before death to give rise to acid digestion and necrosis, even aspiration pneumonia, in the lung, (Mendelson’s syndrome) El]. (iii) Agonal reflux during the process of dying. (iv) Postmortem passive transfer from the stomach to the air passages. Fetterman and Moran [2], in 1942, found that 5.7% of all autopsies on medical patients revealed microscopic food particles in the lungs associated with inflammatory changes. Innes et al. [3] found 6% of 750 laboratory rats, to have fragments of bone in their air passages derived from fish-meal food. In both these instances, it was not clear whether the food had entered the air passages during swallowing or had been regurgitated. That agonal reflux can occur is common knowledge. Food in the air passages is frequently seen in cattle after rapid slaughter by pole-axing injuries to the head. In anaesthesia, Weiss [4] and Culver et al. [5] investigated regurgitation by placing Evan’s blue dye into the stomach during 300 anaesthetics. Regurgitation occurred in 26% of cases and aspiration into the lungs in 16%. These were living cases, with expert clinical observers present. Evaluation of the situation after death was not nearly so satisfactory. In 1956, the Association of Anaesthetists investigated 1000 deaths associated with anaesthesia of which 110 were ascribed to “aspiration of vomit” [6]. The authors commented on the difficulty of pathological diagnosis and placed cases in this category only when the clinical history justified it. An extensive investigation and survey of the literature was made by Gardner in 1958. He quoted a large number of cases associated with various conditions and commented thus. “In most of the cases quoted, the evidence of antemortem aspiration of vomit is circumstantial. Autopsy findings in this condition are often inconclusive, because gastric contents may reach the
231
bronchi after death. Proper appreciation of this possibility is essential when interpreting morbid anatomical appearances in the lungs and it is remarkable that the subject has hitherto received so little attention.” Gardner placed barium sulphate suspension into the stomachs of 10 patients immediately after death, using a stomach tube. The tubes were then removed and the bodies sent to the mortuary in the usual way. At autopsy 24-48 hours later, radiographs were taken of the lungs, and barium was found in the lungs of 7 of the 10 bodies. It was present even in the alveoli in some cases, and Gardner presumed that manipulation of the body and of the lungs had caused this postmortem phenomenon. He concludes, “the presence of gastric contents in the lungs at autopsy, often ascribed to antemortem or agonal aspiration, is not in itself conclusive evidence of such a happening, unless immediately after death and before moving the body, the trachea has been blocked with an obturator”. In the second experiment, Gardner gave barium sulphate suspension in a palatable drink to 94 postoperative or debilitated patients. Barium reached the lungs in 10 of these patients but it was not possible to tell whether the barium had entered the air passages during swallowing or whether it had regurgitated, from the stomach. In order to distinguish between these causes, Gardner then introduced barium sulphate directly into the stomach by a tube in 51 patients and found that only one subsequently displayed barium in the air passages. This occurred during the passage of a gastric tube to relieve abdominal distention, during which process the patient died. From these results, Gardner deduced that true regurgitation of stomach contents during life was relatively rare and that most cases of aspiration of food particles occurred during the swallowing process. He further commented that “the presence of gastric contents in the bronchi, or even in the alveoli, cannot be taken as evidence of antemortem aspiration, unless immediately after death and before the body has been moved, measures have been taken to prevent gravitation of the gastric contents in the lungs. Furthermore, it may be very difficult to differentiate microscopically between antemortem and postmortem aspirations, because vital cellular reactions continue in the lungs after clinical death”. Gardner appears to favour postmortem spillage of gastric contents into the air passages as an alternative explanation to agonal aspiration. “Aspiration of vomit is often dismissed as an agonal phenomenon. Sometimes this may be so, but more often it is the coup de grace in an ill patient who might otherwise have a chance of survival. This diagnosis may also be made erroneously in an attempt to explain morbid anatomical appearances that have in fact resulted from gravitation of gastric contents into the lungs after death.” The present author has the same conviction that regurgitation of stomach contents as a cause of death is ill-founded unless supported by clinical evidence. As a small pilot investigation, the total incidence of gastric contents in the air passages was examined in a consecutive series of autopsies.
232
In 100 consecutive routine coroner’s autopsies conducted in the Forensic Medicine section of a university Institute of Pathology, the air passages were inspected with particular reference to contained stomach contents. The presence of any obvious naked-eye foreign material in the lower pharynx, glottis, larynx or lower air passages was recorded. During the first part of the recording, evidence was also sought for the presence of gastric contents invisible to naked-eye inspection. This was done in several ways. Firstly, washings of the tracheal and bronchial mucosa with saline were subjected to pH testing both by indicator fluid and by use of the pH meter. However, it was found that even where there was high acidity in the stomach itself, the pH range of the fluids from the air passages rarely dropped below 5 or 6, even where small macroscopic particles of gastric contents were visible. This appeared due to the buffering action of autolysed mucosa and bronchial mucus. Another more successful method was to take scrapings of the trachea and bronchial lining, together with control samples of gastric contents and compare them microscopically. This was, not unnaturally, an excellent method of confirming the presence of gastric contents, but it was found that where no naked-eye material was present, no microscopic evidence was found. After a number of such cases, the reliance upon naked-eye appearances was used as the sole index of gastric aspiration. Indeed, this is more logical a criterion, if substantial mechanical obstruction is being sought as a significant factor in the death.
RESULTS
Quite fortuitously, the number of autopsies studied between the commencement of the series and the presentation of this paper was exactly 100. Of these, 25 cases (and therefore 25%) revealed macroscopic gastric contents in the air passages at autopsy. The causes of death appeared to show no significant variation from the general run of the whole series of routine medicolegal autopsies. In no case did the clinical history (admittedly often poorly detailed), suggest regurgitation of stomach contents and in no case was this considered to be the primary cause of death, there always being adequate underlying pathological lesions to account for the death. Due to the prevalence in some areas of the use of “aspiration of vomit” as the definitive cause of death in small infants suddenly and unexpectedly found dead, records of sudden infant deaths dealt with by the Department were examined over the last 5 years. In these cases, particular note is always taken of the presence of foreign material in the air passages. Of 37 typical cot deaths, where a classical history was combined with lack of any positive visceral pathological findings at autopsy, 9 cases showed the presence of gastric contents in the air passages. This incidence of 24% is virtually identical with that found in the adults, though with such small numbers no great significance is claimed for this coincidence. However, it is felt that it is justifiable to assume that the frequency of gastric contents in the air passages at autopsy is of the same order in infants as in adults.
233
CONCLUSIONS
Death due to the impaction in the larynx of a bolus of swallowed food is undisputed and the presence of a large mass of undigested material blocking the glottis or main air passages is a well-known phenomenon, familiar to most coroner’s pathologists. The occurrence of genuine antemortem regurgitation of stomach contents is also unchallengeable and where well established acid digestion, aspiration pneumonia, etc., is seen in the lungs, this may well be the explanation, though Gardner’s work suggests that a far more common reason is direct inhalation of food as it is being swallowed. However, the fact that one quarter of routine autopsies studied bad macroscopic gastric contents in the air passages, indicates that the standard of proof required before one can confidently state that aspiration of stomach contents is the cause of death, is usually beyond the grasp of any pathologist if he does not have unequivocal clinical corroboration. It is inconceivable to suggest that 25% of a coroner’s routine series of autopsies have died of aspiration of vomit, where in every case there was adequate underlying pathological cause for their demise. Regurgitation of vomit may well be the terminal event which ends life at a particular moment - the coup de grace mentioned by Gardner - but it may also be due to (i) agonal regurgitation or (ii) postmortem overspill. The use of the term “regurgitation of vomit” as the definitive cause of death may in certain circumstances cause extreme personal distress and reinforcement of self-recrimination, as in the parents of victims of the sudden infant death syndrome. Even in these more enlightened times, it may still occasionally lead to an inquest and a verdict of accidental death or death by misadventure. As the majority of cot deaths - in this series, threequarters - died in similar circumstances with no gastric contents in the air passages, it seems hard to understand why the 25% minority are labelled as ‘“aspiration of vomit” when there is no evidence to suggest that the aetiology of the sudden infant death syndrome is any different in this group to the majority. It may be the only positive postmortem finding, but this fact should not be used as a convenient label for the death, considering the unfortunate sequelae that may result. In conclusion, the results of this small series tend to confirm the conviction that although the existence of true regurgitation of stomach contents is not denied, it is often employed as the sole cause of death in conditions where the lack of corroborative clinical evidence render the standard of proof quite unacceptable.
REFERENCES 1 C. L. Mendelson, Aspiration of stomach contents into anaesthesia, Am. J. Obstet. Gynecol., 52 (1946) 191-206.
the
lungs
during
obstetric
234 2 G. H. Fetterman and T. J. Moran, Food aspiration pneumonia, P. Med. J., 45 (1942) 810-812. 3 J. Innes, P. Yevich and E. J. Donati, Note on the origin of some fragments of bone in the lungs of laboratory animals, AMA Arch. Pathol., 61 (1956) 401-406. 4 W. A. Weiss, Regurgitation and aspiration of stomach contents during inhalation anaesthesia, Anaesthesiol., 11 (1950) 102-109. 5 G. Culver, H. Make1 and H. Beecher, The Frequency of aspiration of gastric contents by the lungs during anaesthesia and surgery, Ann. Surg., 133 (1951) 289-292. 6 G. Edwards, H. Morton, E. Pask and W. Wylie, Death associated with anaesthesia: Report on 1000 cases, Anaesthesia, 11 (1956) 194-220. 7 A. M. N. Gardner, Aspiration of food and vomit, Q. J. Med., 27 (1958) 227-242.
229 Printed
in the Netherlands
THE SIGNIFICANCE OF THE POSTMORTEM DISCOVERY GASTRIC CONTENTS IN THE AIR PASSAGES BERNARD
H. KNIGHT
The Welsh National (Gt. Britain) (Received
OF
November
School
of Medicine,
21, 1975;
accepted
Institute December
of Pathology,
Royal
Infirmary,
Cardiff
19,1975)
SUMMARY The significance of the finding of gastric contents in the air passages at postmortem examination is discussed and references quoted to indicate that without clinical corroboration of aspiration of gastric contents, the purely autopsy diagnosis of such aspiration is to be regarded with reservation. In a series of routine medicolegal autopsies, gastric contents were shown to be present in a quarter of all cases, irrespective of the cause of death. This figure also appeared to hold for autopsies upon infants and the special dangers of ascribing infant victims of the “sudden death in infancy syndrome” to the aspiration of vomit is pointed out.
Terms such as “aspiration of vomit”, “inhalation of stomach contents” etc., are quite frequently employed as the sole cause of death in certifying cases after autopsy. These are not necessarily synonymous with choking on food, the occurrence of which is rarely in doubt, especially in the senile and mentally defective. The essential difference is that the latter condition refers to blockage of the glottis, larynx or trachea by large masses of food which are in the process of being swallowed, as opposed to the regurgitation of gastric contents, which is the reflux of food that has already been swallowed. That death can occur from the latter condition is not denied, but it is the frequency with which it genuinely occurs and the standard of its proof by the pathologist, which is in dispute. The author of this paper considers that as a primary cause of death, terms such as “inhalation of stomach contents” are considerably over-employed in situations where there is no corroborative clinical evidence. This applies particularly to deaths of small infants, notably in the “‘sudden infant death syndrome”. Here the results may be particularly unfortunate, in that some coroners feel obliged to hold an inquest, thus reinforcing the guilt feelings of the parents.
HISTORICAL
ASPECTS
Disregarding for a moment the 2 different types of airway blockage mentioned above, “choking on food” is well documented in medical history,
230
even if very uncritically recorded. Four centuries before Christ, Hippocrates warned that “it is bad for drinking to provoke a slight cough or for swallowing to be forced”. Anacreon, the Greek poet, was alleged to have died from inhalation of a grape seed even earlier than the time of Hippocrates. In Britain, Godwin, Earl of Wessex, on being accused by Edward the Confessor in 1053 A.D. of having murdered Alfred the Etheling, protested his innocence saying “if I am guilty, may this bread choke me”. He ate the bread and fell down in a fit and died - possibly natural justice. The English poet, Humphrey Gilbert, died in 1583 from choking caused by a piece of mutton in his glottis. It will be noted that all these cases were based upon clinical observation and the author submits that they are more valid than if the cause of death had been declared after an autopsy without antemortem observation. More recent experiences have cast doubts on the validity of finding gastric contents in the main air passages. Such material may arrive in the respiratory tubes by one of 4 ways. (i) Diversion into the larynx during swallowing - “food going the wrong way”. (ii) True antemortem regurgitation, sometimes a sufficiently long time before death to give rise to acid digestion and necrosis, even aspiration pneumonia, in the lung, (Mendelson’s syndrome) El]. (iii) Agonal reflux during the process of dying. (iv) Postmortem passive transfer from the stomach to the air passages. Fetterman and Moran [2], in 1942, found that 5.7% of all autopsies on medical patients revealed microscopic food particles in the lungs associated with inflammatory changes. Innes et al. [3] found 6% of 750 laboratory rats, to have fragments of bone in their air passages derived from fish-meal food. In both these instances, it was not clear whether the food had entered the air passages during swallowing or had been regurgitated. That agonal reflux can occur is common knowledge. Food in the air passages is frequently seen in cattle after rapid slaughter by pole-axing injuries to the head. In anaesthesia, Weiss [4] and Culver et al. [5] investigated regurgitation by placing Evan’s blue dye into the stomach during 300 anaesthetics. Regurgitation occurred in 26% of cases and aspiration into the lungs in 16%. These were living cases, with expert clinical observers present. Evaluation of the situation after death was not nearly so satisfactory. In 1956, the Association of Anaesthetists investigated 1000 deaths associated with anaesthesia of which 110 were ascribed to “aspiration of vomit” [6]. The authors commented on the difficulty of pathological diagnosis and placed cases in this category only when the clinical history justified it. An extensive investigation and survey of the literature was made by Gardner in 1958. He quoted a large number of cases associated with various conditions and commented thus. “In most of the cases quoted, the evidence of antemortem aspiration of vomit is circumstantial. Autopsy findings in this condition are often inconclusive, because gastric contents may reach the
231
bronchi after death. Proper appreciation of this possibility is essential when interpreting morbid anatomical appearances in the lungs and it is remarkable that the subject has hitherto received so little attention.” Gardner placed barium sulphate suspension into the stomachs of 10 patients immediately after death, using a stomach tube. The tubes were then removed and the bodies sent to the mortuary in the usual way. At autopsy 24-48 hours later, radiographs were taken of the lungs, and barium was found in the lungs of 7 of the 10 bodies. It was present even in the alveoli in some cases, and Gardner presumed that manipulation of the body and of the lungs had caused this postmortem phenomenon. He concludes, “the presence of gastric contents in the lungs at autopsy, often ascribed to antemortem or agonal aspiration, is not in itself conclusive evidence of such a happening, unless immediately after death and before moving the body, the trachea has been blocked with an obturator”. In the second experiment, Gardner gave barium sulphate suspension in a palatable drink to 94 postoperative or debilitated patients. Barium reached the lungs in 10 of these patients but it was not possible to tell whether the barium had entered the air passages during swallowing or whether it had regurgitated, from the stomach. In order to distinguish between these causes, Gardner then introduced barium sulphate directly into the stomach by a tube in 51 patients and found that only one subsequently displayed barium in the air passages. This occurred during the passage of a gastric tube to relieve abdominal distention, during which process the patient died. From these results, Gardner deduced that true regurgitation of stomach contents during life was relatively rare and that most cases of aspiration of food particles occurred during the swallowing process. He further commented that “the presence of gastric contents in the bronchi, or even in the alveoli, cannot be taken as evidence of antemortem aspiration, unless immediately after death and before the body has been moved, measures have been taken to prevent gravitation of the gastric contents in the lungs. Furthermore, it may be very difficult to differentiate microscopically between antemortem and postmortem aspirations, because vital cellular reactions continue in the lungs after clinical death”. Gardner appears to favour postmortem spillage of gastric contents into the air passages as an alternative explanation to agonal aspiration. “Aspiration of vomit is often dismissed as an agonal phenomenon. Sometimes this may be so, but more often it is the coup de grace in an ill patient who might otherwise have a chance of survival. This diagnosis may also be made erroneously in an attempt to explain morbid anatomical appearances that have in fact resulted from gravitation of gastric contents into the lungs after death.” The present author has the same conviction that regurgitation of stomach contents as a cause of death is ill-founded unless supported by clinical evidence. As a small pilot investigation, the total incidence of gastric contents in the air passages was examined in a consecutive series of autopsies.
232
In 100 consecutive routine coroner’s autopsies conducted in the Forensic Medicine section of a university Institute of Pathology, the air passages were inspected with particular reference to contained stomach contents. The presence of any obvious naked-eye foreign material in the lower pharynx, glottis, larynx or lower air passages was recorded. During the first part of the recording, evidence was also sought for the presence of gastric contents invisible to naked-eye inspection. This was done in several ways. Firstly, washings of the tracheal and bronchial mucosa with saline were subjected to pH testing both by indicator fluid and by use of the pH meter. However, it was found that even where there was high acidity in the stomach itself, the pH range of the fluids from the air passages rarely dropped below 5 or 6, even where small macroscopic particles of gastric contents were visible. This appeared due to the buffering action of autolysed mucosa and bronchial mucus. Another more successful method was to take scrapings of the trachea and bronchial lining, together with control samples of gastric contents and compare them microscopically. This was, not unnaturally, an excellent method of confirming the presence of gastric contents, but it was found that where no naked-eye material was present, no microscopic evidence was found. After a number of such cases, the reliance upon naked-eye appearances was used as the sole index of gastric aspiration. Indeed, this is more logical a criterion, if substantial mechanical obstruction is being sought as a significant factor in the death.
RESULTS
Quite fortuitously, the number of autopsies studied between the commencement of the series and the presentation of this paper was exactly 100. Of these, 25 cases (and therefore 25%) revealed macroscopic gastric contents in the air passages at autopsy. The causes of death appeared to show no significant variation from the general run of the whole series of routine medicolegal autopsies. In no case did the clinical history (admittedly often poorly detailed), suggest regurgitation of stomach contents and in no case was this considered to be the primary cause of death, there always being adequate underlying pathological lesions to account for the death. Due to the prevalence in some areas of the use of “aspiration of vomit” as the definitive cause of death in small infants suddenly and unexpectedly found dead, records of sudden infant deaths dealt with by the Department were examined over the last 5 years. In these cases, particular note is always taken of the presence of foreign material in the air passages. Of 37 typical cot deaths, where a classical history was combined with lack of any positive visceral pathological findings at autopsy, 9 cases showed the presence of gastric contents in the air passages. This incidence of 24% is virtually identical with that found in the adults, though with such small numbers no great significance is claimed for this coincidence. However, it is felt that it is justifiable to assume that the frequency of gastric contents in the air passages at autopsy is of the same order in infants as in adults.
233
CONCLUSIONS
Death due to the impaction in the larynx of a bolus of swallowed food is undisputed and the presence of a large mass of undigested material blocking the glottis or main air passages is a well-known phenomenon, familiar to most coroner’s pathologists. The occurrence of genuine antemortem regurgitation of stomach contents is also unchallengeable and where well established acid digestion, aspiration pneumonia, etc., is seen in the lungs, this may well be the explanation, though Gardner’s work suggests that a far more common reason is direct inhalation of food as it is being swallowed. However, the fact that one quarter of routine autopsies studied bad macroscopic gastric contents in the air passages, indicates that the standard of proof required before one can confidently state that aspiration of stomach contents is the cause of death, is usually beyond the grasp of any pathologist if he does not have unequivocal clinical corroboration. It is inconceivable to suggest that 25% of a coroner’s routine series of autopsies have died of aspiration of vomit, where in every case there was adequate underlying pathological cause for their demise. Regurgitation of vomit may well be the terminal event which ends life at a particular moment - the coup de grace mentioned by Gardner - but it may also be due to (i) agonal regurgitation or (ii) postmortem overspill. The use of the term “regurgitation of vomit” as the definitive cause of death may in certain circumstances cause extreme personal distress and reinforcement of self-recrimination, as in the parents of victims of the sudden infant death syndrome. Even in these more enlightened times, it may still occasionally lead to an inquest and a verdict of accidental death or death by misadventure. As the majority of cot deaths - in this series, threequarters - died in similar circumstances with no gastric contents in the air passages, it seems hard to understand why the 25% minority are labelled as ‘“aspiration of vomit” when there is no evidence to suggest that the aetiology of the sudden infant death syndrome is any different in this group to the majority. It may be the only positive postmortem finding, but this fact should not be used as a convenient label for the death, considering the unfortunate sequelae that may result. In conclusion, the results of this small series tend to confirm the conviction that although the existence of true regurgitation of stomach contents is not denied, it is often employed as the sole cause of death in conditions where the lack of corroborative clinical evidence render the standard of proof quite unacceptable.
REFERENCES 1 C. L. Mendelson, Aspiration of stomach contents into anaesthesia, Am. J. Obstet. Gynecol., 52 (1946) 191-206.
the
lungs
during
obstetric
234 2 G. H. Fetterman and T. J. Moran, Food aspiration pneumonia, P. Med. J., 45 (1942) 810-812. 3 J. Innes, P. Yevich and E. J. Donati, Note on the origin of some fragments of bone in the lungs of laboratory animals, AMA Arch. Pathol., 61 (1956) 401-406. 4 W. A. Weiss, Regurgitation and aspiration of stomach contents during inhalation anaesthesia, Anaesthesiol., 11 (1950) 102-109. 5 G. Culver, H. Make1 and H. Beecher, The Frequency of aspiration of gastric contents by the lungs during anaesthesia and surgery, Ann. Surg., 133 (1951) 289-292. 6 G. Edwards, H. Morton, E. Pask and W. Wylie, Death associated with anaesthesia: Report on 1000 cases, Anaesthesia, 11 (1956) 194-220. 7 A. M. N. Gardner, Aspiration of food and vomit, Q. J. Med., 27 (1958) 227-242.
