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Negative pressure and reductio ad absurdum
Medical Hypotheses 14: 407-412, 1984
NEGATIVE
PRESSURE
M. Gerard
Baggot,
AND REDUCTIO
P.O.
AD ABSURDUM
Box 697, Granite
City,
Illinois
62040
U.S.A.
ABSTRACT The popular theory of “Negative Pressure”, and its implications, conflict with the facts established by radiologists, divers, submarines and modern aviation. Though pressure in the body (belly or thorax) may at times seem negative, under ordinary circumstances it cannot be less than atmospheric, and in fact averages slightly more. The spontaneous movement of air from a pneumothorax or pneumoperitoneum, out into the atmosphere, proves this. The fact that elimination of a pneumoperitoneum or pneumothorax can take days or more, proves that pressure in the pleural or peritoneal cavities averages only slightly greater than pressure in the lymphatics/ veins/ atmosphere. Using Euclid’s test for a hypothesis of examining its implications, one finds that negative pressure cannot exist in the body. Further, function of the contractile organs; heart, lungs, bowels, uterus, etc. are favored by pressure which stays close to neutral or zero, that is atmospheric. Atmospheric pressure is the bottom line, whereas “Negative Pressure” like “vacuum” is merely a theoretical concept. Key Words: Negative piration. Epidural.
Pressure. Heart. Lungs. Circulation. Divers. Air. Embolism. Atomospheric.
Res-
INTRODUCTION The phrase “Negative Pressure” occurs in connection with the thorax, (1) respiration., (2) aad the epidural (ext&m-al space. (3! When I published my paper, “Abdominal Disproportion in Pregnant, Surgical, and Other Patients” (4), the late Professor G. W. Theobald (5) told me he believed that in gravid women, intra-abdominal pressure was sometimes “negative” (6). 407
“Negative Pressure” is defined by Webster’s Dictionary as “less than existing atmospheric pressure taken as a zero of (7) The human body is a muco-cutaneous (compressreference”. ible) bag containing liquid and gaseous fluids with a skeleton. Therefore, if pressure in any area within the body, tended to fall below atmospheric, intra-integumentary gases or liquids would immediately flow into that space so that atmospheric pressure would be maintained. Insofar, as the thoracic or abdominal capacities can vary to a limited extent, and the bulk of their contents are contractile air-bags, in theory the lungs or bowels might contract to the point where a vacuum was tending to develop, as the contents became smaller than the cavity. Then one might say there was a negative, pressure in the belly or thorax. i. e. sub-atmospheric However, atmospheric pressure outside the body acting on the integument would mould or crush it, obliterating any space with a lesser pressure, while simultaneously, air already dissolved in the bloodstream would bubble out into the low pressure area. These effects never happen under ordinary circumstances. Imagine For example, if intrapleural pressure really were “negative”, i.e. less than atmospheric, we would all have bilateral pneumothorax (and be dead from respiratory failure), because the nitrogen dissolved in our blood would bubble out, e.g. into the pleural cavities. In divers ascending too rapidly, pressure throughout the body is higher than atmospheric. These patients get air emboli as theair comes out of solution. Does it first appear in the thoracic or abdominal cavities where there is supposed to be a “negative” pressure? Not at all! She Stoops
To Conquer
(Goldsmith)
Some ladies find when they bend down, as viscera tend to move from pelvis to chest, air enters the vagina. Resumption of the erect posture then expresses the air with an embarassing noise, i. e. “vaginal garrulitas”. Now pressure in the upper abdomen -is tending to fall but (as the viscera incline pelvicwards) air does not bubble out there, so the fall cannot reach sub-atmosThe radiologist does not see gas under her diaphragm. pheric levels. The movement of air in and out of the bowels and respiratory tract is well known, (which gases remain part of the atmosphere, not of the intra-muco-cutaneous nor intra-integumcntary contents) and iatrogenic gas-pockets occur. Otherwise, free gas inside
408
the body is rarely seen, e. g. when there has been a breach in the muco-cutaneous envelope (perforated ulcer, ruptured bleb, etc. ) that produced by bacteria, or in babies who died in utero.
(8) Supposing Inhalation occurs, when the chest expands, because pressure in the bodv and/or air chambers cannot be less than existing a$nospheric pressure. If air cannot enter through the trachea, a hole in the thoracic wall or a wound in the neck, thoracic expansion cannot occur, except by commensurate expansion of some intra-thoracic viscera, generally the vessels. The subject who cannot inhale because of a respiratory obstruction, as he tries vainly to fill his lungs with air, congests them with intra-integumentary fluids which flow in from tissues outside the thorax. Depending on how long and how hard the patient tried to inhale before dying, at autopsy his lungs show more or less congestion with petechial hemorrhages. (9) To those familiar with the problems of divers, submarines and pressurized planes, these points are elementary. (10) Even those who have merely traveled in jet aircraft have learned from their ears, that pressure in the body is tied to prevailing If pressure throughout the body ever did atmospheric pressure. fall, one would shrink, at least until the skeleton showed through (as in starvation/dehydration) compressed by the atmosphere until pressure inside the body was atmospheric (or more) once again. Nix ! If
i. e. as
in the than atmospheric, These the trachea. space until
space
one
were “negative”, see gas there, would flowing into the expressure was The
409
pressure be set and kept at zero no deviation. Business
(i. e. atmospheric)
with little
or
As Usual
Therefore, when the thoracic surgeon opens the chest, the heart does not usually show any reaction, because this entry of atmospheric= into the chest, does not change intra-thoracic Again, if intra-thoracic fell below atmospheric pressure, pressure. exhalation would be difficult to impossible. Whereas, if intrathoracic pressure rose above zero, inhalation would be hindered or stopped altoghether, as exemplified in bilateral tension pneumothorax. The intrapulmonary pressure of an explosive cough or sneeze is certainly not “negative” nor subatmospheric, neither is it the same as intra-thoracic pressure. Pressure
Gradient
If intra-abdominal pressure fell below atmospheric, defecation, parturition, emesis, micturition, etc. would be difficult to impossible. If intra-abdominal pressure rose above atmospheric, deglutition would be difficult or impossible and the contents would tend to be squeezed out of the bowel, uterus, and bladder. Also inhalation, i. e. descent of the diaphragm with elevation of the rib Abdominal distention is cage, would be hampered or prevented. and before the introduction of Aba potentially grave condition, it was a common cause dominal Decompression by Wagensteen, Incidentally, if the body were not alof postoperative morbidity. ready saturated with air, in cases of paralytic ileus, the air which distends the bowels, would exit, via the blood-stream and the lungs, rapidly and without causing such morbid pressure in the belly. (11) Spontaneous elimination of a pneumothorax, or pneumoperitoneum does occur, because pressure in the pleural or peritoneal cavities is not “negative” but in fact must be greater than atmospheric, at times, since such air masses flow out into the atmosphere via the circulation. During exhalation intra-thoracic pressure exceeds its baseline, i. e. atmospheric, but during inhalation does not normally fall below it. I say “elimination” since these unusual masses of air are not really “absorbed” because the body is already saturated with air, at atmospheric pressure. Spontaneous pneumothorax arises when the air chamber contracts, e. g. coughing. As the lungs tend to get smaller than the thorax, pressure in the latter tends to fall and a vacuum tends to arise therein. Realization of these tendencies is impossible, so the pleural cavity expands and atmospheric pressure there, is
410
maintained by influx of gas, from elsewhere the air-chambers, i. e. pneumothorax.
in the body,
usually
CONCLUSION The misleading term “negative pressure” should be abandoned, since really there is no such thing. “Potentially subatmospheric” or even “pseudo-negative” might be used instead. Better still, function and disorders of the thorax, and its viscera should be considered in the light of the “Law of the Thorax” which it should fit them, is, “The thorax must not alone contain its viscera, while an intra-thoracic viscus should fit its host and its fellows”. (12) When the pleura is breached, why does the lung collapse? It collapes because of its inherent contractility, and under its own weight, (once the pneumothorax relieves it of the duty of filling the hemithorax). The spontaneous return of collapsed lung to normal will be discussed in another communication. (13) I have already explained the difference between atelectasis and detelectasis, i. e. collapsed lung. (14,15,16) REFERENCES Publishers, Inc., R. : The Yearbook Editor Otto Glasser, p. 1107, Chicago,
1.
Mantz, Frederick Medical Physics, 1950.
2.
Lee, J. Alfred & Atkinson, R. S. : A synopsis of anesWilliams & Wilkins, p. 365 & p. 531, Baltimore, thesia. 1964.
3.
Adriani, Charles
4.
Theobald,
John: Techniques and procedures C. Thomas, p. 433, Springfield, G. W. :
c5 .
6.
:
7.
8.
M.H
E
of anesthesia. 1964.
9.
Rentoul, prudence
Edgar & Smith, and Toxicology,
Hamilton: Glaister’s Medical Jurisp. 135, Edinburgh and London, 1973.
10.
Bennett, P. B. & Elliot, of diving and compressed da11 and Cassell, 1969.
11.
as exemplified by abdominal wound Baggot, M. G. : Herniation dehiscence; varieties, etiology and management. Journal of the Irish Medical Association, 71:54, Feb., 1978.
12.
complications Baggot, M. G. : Common and inter-related anesthesia, surgery and obstetrics. Current Researches In Anesthesia And Analgesia, 33:1, Jan. -Feb., 1954.
13.
Baggot, piratory
14.
of the lungs, atelectasis, Baggot, M. G. : Massive collapse The American and intravascular pulmonic hypervolemia. Journal of Surgery, 85:2, pp 184-186, Feb., 1953.
15.
Baggot. M. G. : The architectural function of the pulmonary capillaries. Letter to The Editor, The Lancet, pp 492-493, Sept., 1957.
16.
Baggot, M. G. : Massive collapse of the lungs. The Journal, J. A. M. A., April, 1961.
D. H. : The physiology and medicine air work. London, Balliere, Tin-
baffles M. G. : The valves, system. (to be published).
412
and sphincters
of
of the res-
Letters
To
NEGATIVE
PRESSURE
M. Gerard
Baggot,
AND REDUCTIO
P.O.
AD ABSURDUM
Box 697, Granite
City,
Illinois
62040
U.S.A.
ABSTRACT The popular theory of “Negative Pressure”, and its implications, conflict with the facts established by radiologists, divers, submarines and modern aviation. Though pressure in the body (belly or thorax) may at times seem negative, under ordinary circumstances it cannot be less than atmospheric, and in fact averages slightly more. The spontaneous movement of air from a pneumothorax or pneumoperitoneum, out into the atmosphere, proves this. The fact that elimination of a pneumoperitoneum or pneumothorax can take days or more, proves that pressure in the pleural or peritoneal cavities averages only slightly greater than pressure in the lymphatics/ veins/ atmosphere. Using Euclid’s test for a hypothesis of examining its implications, one finds that negative pressure cannot exist in the body. Further, function of the contractile organs; heart, lungs, bowels, uterus, etc. are favored by pressure which stays close to neutral or zero, that is atmospheric. Atmospheric pressure is the bottom line, whereas “Negative Pressure” like “vacuum” is merely a theoretical concept. Key Words: Negative piration. Epidural.
Pressure. Heart. Lungs. Circulation. Divers. Air. Embolism. Atomospheric.
Res-
INTRODUCTION The phrase “Negative Pressure” occurs in connection with the thorax, (1) respiration., (2) aad the epidural (ext&m-al space. (3! When I published my paper, “Abdominal Disproportion in Pregnant, Surgical, and Other Patients” (4), the late Professor G. W. Theobald (5) told me he believed that in gravid women, intra-abdominal pressure was sometimes “negative” (6). 407
“Negative Pressure” is defined by Webster’s Dictionary as “less than existing atmospheric pressure taken as a zero of (7) The human body is a muco-cutaneous (compressreference”. ible) bag containing liquid and gaseous fluids with a skeleton. Therefore, if pressure in any area within the body, tended to fall below atmospheric, intra-integumentary gases or liquids would immediately flow into that space so that atmospheric pressure would be maintained. Insofar, as the thoracic or abdominal capacities can vary to a limited extent, and the bulk of their contents are contractile air-bags, in theory the lungs or bowels might contract to the point where a vacuum was tending to develop, as the contents became smaller than the cavity. Then one might say there was a negative, pressure in the belly or thorax. i. e. sub-atmospheric However, atmospheric pressure outside the body acting on the integument would mould or crush it, obliterating any space with a lesser pressure, while simultaneously, air already dissolved in the bloodstream would bubble out into the low pressure area. These effects never happen under ordinary circumstances. Imagine For example, if intrapleural pressure really were “negative”, i.e. less than atmospheric, we would all have bilateral pneumothorax (and be dead from respiratory failure), because the nitrogen dissolved in our blood would bubble out, e.g. into the pleural cavities. In divers ascending too rapidly, pressure throughout the body is higher than atmospheric. These patients get air emboli as theair comes out of solution. Does it first appear in the thoracic or abdominal cavities where there is supposed to be a “negative” pressure? Not at all! She Stoops
To Conquer
(Goldsmith)
Some ladies find when they bend down, as viscera tend to move from pelvis to chest, air enters the vagina. Resumption of the erect posture then expresses the air with an embarassing noise, i. e. “vaginal garrulitas”. Now pressure in the upper abdomen -is tending to fall but (as the viscera incline pelvicwards) air does not bubble out there, so the fall cannot reach sub-atmosThe radiologist does not see gas under her diaphragm. pheric levels. The movement of air in and out of the bowels and respiratory tract is well known, (which gases remain part of the atmosphere, not of the intra-muco-cutaneous nor intra-integumcntary contents) and iatrogenic gas-pockets occur. Otherwise, free gas inside
408
the body is rarely seen, e. g. when there has been a breach in the muco-cutaneous envelope (perforated ulcer, ruptured bleb, etc. ) that produced by bacteria, or in babies who died in utero.
(8) Supposing Inhalation occurs, when the chest expands, because pressure in the bodv and/or air chambers cannot be less than existing a$nospheric pressure. If air cannot enter through the trachea, a hole in the thoracic wall or a wound in the neck, thoracic expansion cannot occur, except by commensurate expansion of some intra-thoracic viscera, generally the vessels. The subject who cannot inhale because of a respiratory obstruction, as he tries vainly to fill his lungs with air, congests them with intra-integumentary fluids which flow in from tissues outside the thorax. Depending on how long and how hard the patient tried to inhale before dying, at autopsy his lungs show more or less congestion with petechial hemorrhages. (9) To those familiar with the problems of divers, submarines and pressurized planes, these points are elementary. (10) Even those who have merely traveled in jet aircraft have learned from their ears, that pressure in the body is tied to prevailing If pressure throughout the body ever did atmospheric pressure. fall, one would shrink, at least until the skeleton showed through (as in starvation/dehydration) compressed by the atmosphere until pressure inside the body was atmospheric (or more) once again. Nix ! If
i. e. as
in the than atmospheric, These the trachea. space until
space
one
were “negative”, see gas there, would flowing into the expressure was The
409
pressure be set and kept at zero no deviation. Business
(i. e. atmospheric)
with little
or
As Usual
Therefore, when the thoracic surgeon opens the chest, the heart does not usually show any reaction, because this entry of atmospheric= into the chest, does not change intra-thoracic Again, if intra-thoracic fell below atmospheric pressure, pressure. exhalation would be difficult to impossible. Whereas, if intrathoracic pressure rose above zero, inhalation would be hindered or stopped altoghether, as exemplified in bilateral tension pneumothorax. The intrapulmonary pressure of an explosive cough or sneeze is certainly not “negative” nor subatmospheric, neither is it the same as intra-thoracic pressure. Pressure
Gradient
If intra-abdominal pressure fell below atmospheric, defecation, parturition, emesis, micturition, etc. would be difficult to impossible. If intra-abdominal pressure rose above atmospheric, deglutition would be difficult or impossible and the contents would tend to be squeezed out of the bowel, uterus, and bladder. Also inhalation, i. e. descent of the diaphragm with elevation of the rib Abdominal distention is cage, would be hampered or prevented. and before the introduction of Aba potentially grave condition, it was a common cause dominal Decompression by Wagensteen, Incidentally, if the body were not alof postoperative morbidity. ready saturated with air, in cases of paralytic ileus, the air which distends the bowels, would exit, via the blood-stream and the lungs, rapidly and without causing such morbid pressure in the belly. (11) Spontaneous elimination of a pneumothorax, or pneumoperitoneum does occur, because pressure in the pleural or peritoneal cavities is not “negative” but in fact must be greater than atmospheric, at times, since such air masses flow out into the atmosphere via the circulation. During exhalation intra-thoracic pressure exceeds its baseline, i. e. atmospheric, but during inhalation does not normally fall below it. I say “elimination” since these unusual masses of air are not really “absorbed” because the body is already saturated with air, at atmospheric pressure. Spontaneous pneumothorax arises when the air chamber contracts, e. g. coughing. As the lungs tend to get smaller than the thorax, pressure in the latter tends to fall and a vacuum tends to arise therein. Realization of these tendencies is impossible, so the pleural cavity expands and atmospheric pressure there, is
410
maintained by influx of gas, from elsewhere the air-chambers, i. e. pneumothorax.
in the body,
usually
CONCLUSION The misleading term “negative pressure” should be abandoned, since really there is no such thing. “Potentially subatmospheric” or even “pseudo-negative” might be used instead. Better still, function and disorders of the thorax, and its viscera should be considered in the light of the “Law of the Thorax” which it should fit them, is, “The thorax must not alone contain its viscera, while an intra-thoracic viscus should fit its host and its fellows”. (12) When the pleura is breached, why does the lung collapse? It collapes because of its inherent contractility, and under its own weight, (once the pneumothorax relieves it of the duty of filling the hemithorax). The spontaneous return of collapsed lung to normal will be discussed in another communication. (13) I have already explained the difference between atelectasis and detelectasis, i. e. collapsed lung. (14,15,16) REFERENCES Publishers, Inc., R. : The Yearbook Editor Otto Glasser, p. 1107, Chicago,
1.
Mantz, Frederick Medical Physics, 1950.
2.
Lee, J. Alfred & Atkinson, R. S. : A synopsis of anesWilliams & Wilkins, p. 365 & p. 531, Baltimore, thesia. 1964.
3.
Adriani, Charles
4.
Theobald,
John: Techniques and procedures C. Thomas, p. 433, Springfield, G. W. :
c5 .
6.
:
7.
8.
M.H
E
of anesthesia. 1964.
9.
Rentoul, prudence
Edgar & Smith, and Toxicology,
Hamilton: Glaister’s Medical Jurisp. 135, Edinburgh and London, 1973.
10.
Bennett, P. B. & Elliot, of diving and compressed da11 and Cassell, 1969.
11.
as exemplified by abdominal wound Baggot, M. G. : Herniation dehiscence; varieties, etiology and management. Journal of the Irish Medical Association, 71:54, Feb., 1978.
12.
complications Baggot, M. G. : Common and inter-related anesthesia, surgery and obstetrics. Current Researches In Anesthesia And Analgesia, 33:1, Jan. -Feb., 1954.
13.
Baggot, piratory
14.
of the lungs, atelectasis, Baggot, M. G. : Massive collapse The American and intravascular pulmonic hypervolemia. Journal of Surgery, 85:2, pp 184-186, Feb., 1953.
15.
Baggot. M. G. : The architectural function of the pulmonary capillaries. Letter to The Editor, The Lancet, pp 492-493, Sept., 1957.
16.
Baggot, M. G. : Massive collapse of the lungs. The Journal, J. A. M. A., April, 1961.
D. H. : The physiology and medicine air work. London, Balliere, Tin-
baffles M. G. : The valves, system. (to be published).
412
and sphincters
of
of the res-
Letters
To