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TAPERED NYLON-REINFORCED-LATEX ENDOTRACHEAL TUBES
693
CpAH calculations,
direct
measurements showed that in most
animals
this
para-
directly related to blood-presThe shape of sure. the regression line suggested by the results in fig. 2 indicates that autoregulameter
was
tion of renal bloodflow in response to a change in perfusion
pressure28-28 mayalso exist even under the above conditions. It is doubtful, however, whether these results can be taken as evidence against the ischaemic origin of the shock kidney ", since P.A.H. extraction in these experiFig. 2-The relation between percentage ments decreased in a change in calculated total renal vascular resistance and percentage change parallel fashion to in blood-pressure. renal blood-flow and rose promptlv with replacement of blood or an equal volume of iso-oncotic dextran. To test this further, renal cineradiography was carried out before and during hypotension by injecting 60%’Urografin ’ into the aorta above the origins of the renal arteries. Standard diameters across the perfused area in the kidney, during the " capillary " phase of the arteriograms, were measured from the cinematographic pictures, in reference to the known width of the catheter. The table shows that the diameter of the perfused area of the kidney decreased by about 10% during hypotension, which corresponds to the width of the cortex in the dog kidney.
only a measure of the supply of blood to the proximal tubule, where it is secreted; and (2) of the possible aglomerular blood paths through the kidney, arteriovenous shunting may be a more physiological mechanism, and applicable to more mammalian species, than has been previously considered, since it occurred under conditions of acute hypotension which cannot be equated with shock. J. JIRKA Prague V. GANZ M.D. Prague V. FENCL M.D. Prague J. H. CORT M.D. Yale, PH.D. Cantab. R. TRÁVNÍČEK M.D.
Institute for Cardiovascular Research, Prague, Czechoslovakia Institute for Clinical and Experimental Surgery,
M.D.
Prague
Brno
New Inventions
"
The most likely explanation for these findings is that arteriovenous shunts have opened up early in the stage of acute hypotension, blood being excluded from the cortical circulation. This old concept 29 has been more recently elaborated in detail by Trueta et al.,30 and most vigorously
TAPERED NYLON-REINFORCED-LATEX ENDOTRACHEAL TUBES THE rigidity of the wall of a reinforced-latex tube limits the possible size of the connector. This means that the lumen is unnecessarily reduced, unless a larger connector is inserted into the flaccid proximal (machine) end of soft latex. In that case, however, the tube length cannot be adjusted; furthermore, the junction itself is a weak point because kinking is likely. I have introduced tapered tubes which have two advantages: (1) a larger connector can be used; and (2) the length is adjustable, since the tube can be cut. This does not weaken it; and it will still withstand boiling. The tubes, of latex, are reinforced by a nylon helix. This runs the whole length of the tube, and there is no flaccid section of latex at the proximal end. The metal connector (which can be of any type) thus fits against a rigid wall (fig. 1). The following sizes (Magill scale) are available: plain tubes, 1-10; cuffed tubes, 3-10. These refer to the distal (patient)
DIAMETER OF THE PERFUSED PORTION OF THE DOG KIDNEY DURING
INTRA-ARTERIAL CINERADIOGRAPHY
Two diameters were measured by taking a constant angle from the end segment of the catheter, and all measurements were corrected to absolute values from the known width of the catheter. Figures are averages.D.
Fig. 2.
contested by a large number of investigators (e.g., Maxwell et’ al. 31) who have argued that such a mechanism might exist only under extremely pathological conditions, and even then only in the rabbit. Anatomical evidence for the opening of shunts during acute hypotension has recently been presented by Gomori.s2 The present data suggest that: (1) particularly under conditions of reduced perfusion pressure, CPAH is in fact 26. Winton, F. R. Modem Views on the Secretion of Urine; p. 61. Boston, 1956. 27. Pappenheimer, J. R., Kinter, W. B. Amer. J. Physiol. 1956, 185, 377, 391. 28. Hardin, R. A., Scott, J. B., Haddy, F. Amer. J. Physiol. 1960, 199, 1192. 29. Gross, C. F. Essai sur la structure microscopique du rein. Strasbourg, Paris, Geneva, 1868. 30. Trueta, J., Barclay, A. E., Daniel, P. M., Pritchard, M. M. L. Studies on the Renal Circulation. Oxford, 1947. 31. Maxwell, M. H., Breed, E. S., Smith, H. W. Amer. J. Med. 1950, 9, 216. 32. Gömori, P. (1960) First International Congress of Nephrology, abstract of papers, Excerpta Med., international congress series, no. 29.
end. The tubes are tapered so that one of two connectors will fit them all. Sizes 1-6 have a distal end 2 in. long, a 3 in. tapered middle piece, and a proximal end, 2 in. or longer, of size 7 (Magill scale). In sizes 7-10 the distal end is 3 in. long, the tapered centre piece 4 in., and the proximal end (size 11) 2 in. or longer (sections A, B, and C in fig. 2). The internal and external diameters at either end of the tube conform to the specifications and manufacturing tolerances for Magill tubes in extruded natural rubber, and so do the sizes of the cuff and inflating tube. We have used our tubes for some time; they have proved entirely satisfactory. They should be cleaned with soap, water, and a brush, and then boiled for three minutes to sterilise them. The tubes have been developed by the British Oxygen, Company, and can be obtained from A. Charles King, Devonshire Street, London, W.1.
Queen Victoria Hospital, East Grinstead, Sussex
G. E. HALE ENDERBY M.A., M.B.
Cantab.,
F.F.A.
R.C.S., D.A.
CpAH calculations,
direct
measurements showed that in most
animals
this
para-
directly related to blood-presThe shape of sure. the regression line suggested by the results in fig. 2 indicates that autoregulameter
was
tion of renal bloodflow in response to a change in perfusion
pressure28-28 mayalso exist even under the above conditions. It is doubtful, however, whether these results can be taken as evidence against the ischaemic origin of the shock kidney ", since P.A.H. extraction in these experiFig. 2-The relation between percentage ments decreased in a change in calculated total renal vascular resistance and percentage change parallel fashion to in blood-pressure. renal blood-flow and rose promptlv with replacement of blood or an equal volume of iso-oncotic dextran. To test this further, renal cineradiography was carried out before and during hypotension by injecting 60%’Urografin ’ into the aorta above the origins of the renal arteries. Standard diameters across the perfused area in the kidney, during the " capillary " phase of the arteriograms, were measured from the cinematographic pictures, in reference to the known width of the catheter. The table shows that the diameter of the perfused area of the kidney decreased by about 10% during hypotension, which corresponds to the width of the cortex in the dog kidney.
only a measure of the supply of blood to the proximal tubule, where it is secreted; and (2) of the possible aglomerular blood paths through the kidney, arteriovenous shunting may be a more physiological mechanism, and applicable to more mammalian species, than has been previously considered, since it occurred under conditions of acute hypotension which cannot be equated with shock. J. JIRKA Prague V. GANZ M.D. Prague V. FENCL M.D. Prague J. H. CORT M.D. Yale, PH.D. Cantab. R. TRÁVNÍČEK M.D.
Institute for Cardiovascular Research, Prague, Czechoslovakia Institute for Clinical and Experimental Surgery,
M.D.
Prague
Brno
New Inventions
"
The most likely explanation for these findings is that arteriovenous shunts have opened up early in the stage of acute hypotension, blood being excluded from the cortical circulation. This old concept 29 has been more recently elaborated in detail by Trueta et al.,30 and most vigorously
TAPERED NYLON-REINFORCED-LATEX ENDOTRACHEAL TUBES THE rigidity of the wall of a reinforced-latex tube limits the possible size of the connector. This means that the lumen is unnecessarily reduced, unless a larger connector is inserted into the flaccid proximal (machine) end of soft latex. In that case, however, the tube length cannot be adjusted; furthermore, the junction itself is a weak point because kinking is likely. I have introduced tapered tubes which have two advantages: (1) a larger connector can be used; and (2) the length is adjustable, since the tube can be cut. This does not weaken it; and it will still withstand boiling. The tubes, of latex, are reinforced by a nylon helix. This runs the whole length of the tube, and there is no flaccid section of latex at the proximal end. The metal connector (which can be of any type) thus fits against a rigid wall (fig. 1). The following sizes (Magill scale) are available: plain tubes, 1-10; cuffed tubes, 3-10. These refer to the distal (patient)
DIAMETER OF THE PERFUSED PORTION OF THE DOG KIDNEY DURING
INTRA-ARTERIAL CINERADIOGRAPHY
Two diameters were measured by taking a constant angle from the end segment of the catheter, and all measurements were corrected to absolute values from the known width of the catheter. Figures are averages.D.
Fig. 2.
contested by a large number of investigators (e.g., Maxwell et’ al. 31) who have argued that such a mechanism might exist only under extremely pathological conditions, and even then only in the rabbit. Anatomical evidence for the opening of shunts during acute hypotension has recently been presented by Gomori.s2 The present data suggest that: (1) particularly under conditions of reduced perfusion pressure, CPAH is in fact 26. Winton, F. R. Modem Views on the Secretion of Urine; p. 61. Boston, 1956. 27. Pappenheimer, J. R., Kinter, W. B. Amer. J. Physiol. 1956, 185, 377, 391. 28. Hardin, R. A., Scott, J. B., Haddy, F. Amer. J. Physiol. 1960, 199, 1192. 29. Gross, C. F. Essai sur la structure microscopique du rein. Strasbourg, Paris, Geneva, 1868. 30. Trueta, J., Barclay, A. E., Daniel, P. M., Pritchard, M. M. L. Studies on the Renal Circulation. Oxford, 1947. 31. Maxwell, M. H., Breed, E. S., Smith, H. W. Amer. J. Med. 1950, 9, 216. 32. Gömori, P. (1960) First International Congress of Nephrology, abstract of papers, Excerpta Med., international congress series, no. 29.
end. The tubes are tapered so that one of two connectors will fit them all. Sizes 1-6 have a distal end 2 in. long, a 3 in. tapered middle piece, and a proximal end, 2 in. or longer, of size 7 (Magill scale). In sizes 7-10 the distal end is 3 in. long, the tapered centre piece 4 in., and the proximal end (size 11) 2 in. or longer (sections A, B, and C in fig. 2). The internal and external diameters at either end of the tube conform to the specifications and manufacturing tolerances for Magill tubes in extruded natural rubber, and so do the sizes of the cuff and inflating tube. We have used our tubes for some time; they have proved entirely satisfactory. They should be cleaned with soap, water, and a brush, and then boiled for three minutes to sterilise them. The tubes have been developed by the British Oxygen, Company, and can be obtained from A. Charles King, Devonshire Street, London, W.1.
Queen Victoria Hospital, East Grinstead, Sussex
G. E. HALE ENDERBY M.A., M.B.
Cantab.,
F.F.A.
R.C.S., D.A.