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A VALVE FOR THE TREATMENT OF HYDROCEPHALUS
562 A VALVE FOR THE TREATMENT OF
HYDROCEPHALUS SIR,-We were most interested to read Mr. Till’s description (Jan. 25) of the new valve which he and his colleagues have developed for use in the drainage of
progressive hydrocephalus.
This method takes into account any proximal or distal obstructions and any collateral flow present, and makes a complete and mainly accurate assessment of the changes to be expected from relief of a particular obstruction under consideration, regardless of its actual diameter, length, or
configuration. The Luton and Dunstable Hospital, Luton, Bedfordshire.
May we comment on one of Mr. Till’s criticisms of the more widely used Spitz-Holter valve-its alleged tendency to become blocked " quite often ". Ventriculo-atrial drainage incorporating a Spitz-Holter valve has been performed in over 60 patients in this hospital in the past four years. In no case has a valve subsequently become blocked; obstruction has been limited to the atrial catheter in 4, and to the ventricular catheter in another 3. Such blockage can reasonably be assumed to be a hazard, whatever the type of valve. Our purpose in drawing attention to this point is to reassure the family doctors who are responsible for the care of our patients at home, insofar as they may conclude that the SpitzHolter valve is particularly prone to blockage. In no way do we intend to criticise the new and cheaper valve, which we hope will live un to its earlv exnectations. Royal Hospital for Sick Children, Glasgow, C.3.
J. F. R. BENTLEY A. G. GRAHAM.
ARTERIAL STENOSIS
SIR,-It gratifying to find that Mr. Brice and his colleagues (Jan. 11) confirm our demonstration that (1) the normal diameter of a vessel is irrelevant in assessing the effect of a stenosis, and (2) the magnitude of the peripheral resistance determines the relative importance of a given stenosis in reducing blood-flow.1 We have shown further that the measurement of pressure, proximal and distal to the stenosis, can be used to calculate the relative diminution of flow, caused by that stenosis. The figure illustrates this calculation. Thus the flow through is
the stenosis is that fraction of the unobstructed
flow, with the
R. V. FIDDIAN. D. BYAR E. A. EDWARDS.
Harvard Medical School and Peter Bent Brigham Hospital, Boston, Massachusetts.
TREATMENT OF MUSCULAR DYSTROPHY
SIR,-In the Savill lecture which you published last week Dr. Walton writes that our trial of nucleotides and nucleosides in muscular dystrophyl was uncontrolled, Whether this deliberate statement is true or not will be obvious to anyone who has read our publication or the correspondence that followed your remarkable leader of June 22. In a disease so notoriously liable to brief subjective variation, more subtle means than double-blind
orthodoxy may give correspondingly more interesting information, as did the objective and exact controls devised for our trial of therapy. It is most gratifying to learn, therefore, that our original report has been so quickly followed by so many other confirmatory trials. Dr. Walton has frequently remarked 2-4 that when one considers treatment, it is difficult not to be despondent ", which may certainly be true if one examines substances like high-energy anabolic steroids ".3 This glum opinion from such a well-known figure might be disheartening were not the scientists among us well aware of the speed and power of the general assault on related problems now launched in the fields of modern molecular biology and elsewhere. Surely a cautious hopeful fortitude should be the rule. "
"
Knightswood Hospital, Glasgow.
W. H. S. THOMSON.
HOSPITAL VENTILATION
SIR,-Dr. Kenneth Nickol (Feb. 15) must be joking. To wait until the National Health Service (Anonyme, as the French would say) got together with some unspecified industrial physician and/or occupational hygienist, convened a committee of inquiry, issued a report, made recommendations and circulated them through regional boards, area committees, and house committees, would take ages and ages. Isn’t the matter too urgent for that sort of fun and games ? Relationship of flow, pressures, and resistance. F=flow in unobstructed vessel; Fl, flow through stenosed vessel. PI central arterial pressure, and proximal to a stenosis. P 2 = pressure resistance. distal to a stenosis. Pg= venous pressure.
Moreover, hospital consultants simply cannot be so impotent dim as Dr. Nickol implies. Surely a surgeon, who can say in his theatre, I will have my instruments autoclaved at 120°C before I use them", and "Iwill have my patients chilled to 30°C. before I plunge the knife into them ", can say with equal firmness in his wards, I will not have my patients cooked higher than 620F ", and nail thermometers on the
which is arrived at by dividing the the stenosis by the pressure proximal. If venous pressure is raised significantly, a correction must be introduced into the formula as Pg. This simple calculation for evaluating the significance of differential pressure readings across a stenosis does not take into account variations in
electrical contact thermometer noise if the ward temperature rose above 62cF, and went on making a hell of a noise until someone forced a window open to cool it down. The physician. who prescribes diets, drugs, and dosages, could surely add; "-and I insist that my patients have one breath of fresh air every six hours ", and, if need be, order some cylinders of the
or
=
Rp=peripheral
same
peripheral resistance,
pressure distal
to
but by artificially lowering peripheral resistance with heat, drugs, or other means appropriate to the area of interest, the maximum increase in flow that might be expected after removal of the stenosis may be determined.
peripheral resistance,
1.
Fiddian,
R.
V., Byar, D., Edwards, E.
A. Arch.
Surg. 1964, 88,
83.
"
"
walls. He could
even
which triggered off
1. 2. 3. 4.
a
rig
up
hell of
an a
Thomson, W. H. S., Guest, K. E. J. Neurol. Neurosurg. Psychiat. 1963, 26, 111. Walton, J. N. Res. Publ. Ass. nerv. ment. Dis. 1961, 38, 378. Walton, J. N. in Muscular Dystrophy in Man and Animals (edited by G. H. Bourne and M. N. Golarz); chap. 7. Basle, 1963. Walton, J. N. Lancet, 1964, i, 447.
HYDROCEPHALUS SIR,-We were most interested to read Mr. Till’s description (Jan. 25) of the new valve which he and his colleagues have developed for use in the drainage of
progressive hydrocephalus.
This method takes into account any proximal or distal obstructions and any collateral flow present, and makes a complete and mainly accurate assessment of the changes to be expected from relief of a particular obstruction under consideration, regardless of its actual diameter, length, or
configuration. The Luton and Dunstable Hospital, Luton, Bedfordshire.
May we comment on one of Mr. Till’s criticisms of the more widely used Spitz-Holter valve-its alleged tendency to become blocked " quite often ". Ventriculo-atrial drainage incorporating a Spitz-Holter valve has been performed in over 60 patients in this hospital in the past four years. In no case has a valve subsequently become blocked; obstruction has been limited to the atrial catheter in 4, and to the ventricular catheter in another 3. Such blockage can reasonably be assumed to be a hazard, whatever the type of valve. Our purpose in drawing attention to this point is to reassure the family doctors who are responsible for the care of our patients at home, insofar as they may conclude that the SpitzHolter valve is particularly prone to blockage. In no way do we intend to criticise the new and cheaper valve, which we hope will live un to its earlv exnectations. Royal Hospital for Sick Children, Glasgow, C.3.
J. F. R. BENTLEY A. G. GRAHAM.
ARTERIAL STENOSIS
SIR,-It gratifying to find that Mr. Brice and his colleagues (Jan. 11) confirm our demonstration that (1) the normal diameter of a vessel is irrelevant in assessing the effect of a stenosis, and (2) the magnitude of the peripheral resistance determines the relative importance of a given stenosis in reducing blood-flow.1 We have shown further that the measurement of pressure, proximal and distal to the stenosis, can be used to calculate the relative diminution of flow, caused by that stenosis. The figure illustrates this calculation. Thus the flow through is
the stenosis is that fraction of the unobstructed
flow, with the
R. V. FIDDIAN. D. BYAR E. A. EDWARDS.
Harvard Medical School and Peter Bent Brigham Hospital, Boston, Massachusetts.
TREATMENT OF MUSCULAR DYSTROPHY
SIR,-In the Savill lecture which you published last week Dr. Walton writes that our trial of nucleotides and nucleosides in muscular dystrophyl was uncontrolled, Whether this deliberate statement is true or not will be obvious to anyone who has read our publication or the correspondence that followed your remarkable leader of June 22. In a disease so notoriously liable to brief subjective variation, more subtle means than double-blind
orthodoxy may give correspondingly more interesting information, as did the objective and exact controls devised for our trial of therapy. It is most gratifying to learn, therefore, that our original report has been so quickly followed by so many other confirmatory trials. Dr. Walton has frequently remarked 2-4 that when one considers treatment, it is difficult not to be despondent ", which may certainly be true if one examines substances like high-energy anabolic steroids ".3 This glum opinion from such a well-known figure might be disheartening were not the scientists among us well aware of the speed and power of the general assault on related problems now launched in the fields of modern molecular biology and elsewhere. Surely a cautious hopeful fortitude should be the rule. "
"
Knightswood Hospital, Glasgow.
W. H. S. THOMSON.
HOSPITAL VENTILATION
SIR,-Dr. Kenneth Nickol (Feb. 15) must be joking. To wait until the National Health Service (Anonyme, as the French would say) got together with some unspecified industrial physician and/or occupational hygienist, convened a committee of inquiry, issued a report, made recommendations and circulated them through regional boards, area committees, and house committees, would take ages and ages. Isn’t the matter too urgent for that sort of fun and games ? Relationship of flow, pressures, and resistance. F=flow in unobstructed vessel; Fl, flow through stenosed vessel. PI central arterial pressure, and proximal to a stenosis. P 2 = pressure resistance. distal to a stenosis. Pg= venous pressure.
Moreover, hospital consultants simply cannot be so impotent dim as Dr. Nickol implies. Surely a surgeon, who can say in his theatre, I will have my instruments autoclaved at 120°C before I use them", and "Iwill have my patients chilled to 30°C. before I plunge the knife into them ", can say with equal firmness in his wards, I will not have my patients cooked higher than 620F ", and nail thermometers on the
which is arrived at by dividing the the stenosis by the pressure proximal. If venous pressure is raised significantly, a correction must be introduced into the formula as Pg. This simple calculation for evaluating the significance of differential pressure readings across a stenosis does not take into account variations in
electrical contact thermometer noise if the ward temperature rose above 62cF, and went on making a hell of a noise until someone forced a window open to cool it down. The physician. who prescribes diets, drugs, and dosages, could surely add; "-and I insist that my patients have one breath of fresh air every six hours ", and, if need be, order some cylinders of the
or
=
Rp=peripheral
same
peripheral resistance,
pressure distal
to
but by artificially lowering peripheral resistance with heat, drugs, or other means appropriate to the area of interest, the maximum increase in flow that might be expected after removal of the stenosis may be determined.
peripheral resistance,
1.
Fiddian,
R.
V., Byar, D., Edwards, E.
A. Arch.
Surg. 1964, 88,
83.
"
"
walls. He could
even
which triggered off
1. 2. 3. 4.
a
rig
up
hell of
an a
Thomson, W. H. S., Guest, K. E. J. Neurol. Neurosurg. Psychiat. 1963, 26, 111. Walton, J. N. Res. Publ. Ass. nerv. ment. Dis. 1961, 38, 378. Walton, J. N. in Muscular Dystrophy in Man and Animals (edited by G. H. Bourne and M. N. Golarz); chap. 7. Basle, 1963. Walton, J. N. Lancet, 1964, i, 447.