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MODIFICATIONS OF A SPIROMETER FOR TIMED CAPACITY AND MID-EXPIRATORY FLOW MEASUREMENTS
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New Inventions MODIFICATIONS OF A SPIROMETER FOR TIMED CAPACITY AND MID-EXPIRATORY FLOW MEASUREMENTS THE percentages of the total vital capacity expired in 1, 2, and 3 seconds indicate the degree of obstructive impairment of ventilation (Gaensler 1). Leuallen and Fowler 2 have shown the additional value of measurement of mid-expiratory flow-rates
early emphysema. We describe here a simple modification a spirometer in general use, which records the total vital capacity and any volume expired during a pre-set timeinterval of 0’1-3’0 sec. (in a similar fashion to the modification described by Gaensler) but in addition permits easy and rapid calculation of flow-rates from the start of mid-expiration. The only alteration to the ordinary spirometer is the insertion of a pin into the top of the counterweight to project horizontally through the slot in the counterweight cylinder. The extra attachments (see figure) are: in of
(1) A solenoid mounted on the bracket supporting the recording disc, in such a way that its rod holds the pointer. When the solenoid is energised from the timer, the rod is raised and the pointer released.
(2) A fixed microswitch mounted above and to the side of the counterweight and kept open, when the counterweight is at its highest position, by the counterweight pin. (3) A second microswitch, mounted on the side of the counterweight cylinder, can be moved on a scale calibrated downwards from 0 to 1600 c.cm. (4) A third switch, mounted above the fixed microswitch, determines which of the two microswitches is brought into operation. (5) An electronic timer graduated from 0-1 to 3-0 sec. can be energised by a momentary electrical impulse.
The end of the bracket supporting the recording disc acts as an indicator for the total vital capacity. For timed capacity, the timer is set to the interval required, and the fixed micro1.
2.
Gaensler, E. A. Amer. Rev. Tuberc. 1951, 64, 256. Leuallen, E. C., Fowler, W. S. ibid. 1955, 72, 783.
switch is brought into operation. As the spirometer bell rises, the counterweight descends, its pin closes the microswitch, and the timer is actuated. The pointer is held until it has registered the amount expired during the set interval, after which the solenoid rod is raised and the pointer released to travel round with the disc. For flow-rates from the start of midexpiration, the movable microswitch is brought into operation and is then set to a position on the scale corresponding to a quarter of the total vital capacity. This amount is therefore expired before the counterweight pin closes the microswitch. Consequently the pointer registers the first quarter of the vital capacity together with the amount expired during the interval, after the first quarter, for which the timer is set (0’1-3’0 sec.). By subtraction of the quarter of the vital capacity it is easy to calculate flow-rates from the start of the mid-expiratory
phase. Timed capacity could, of course, be estimated solely by setting the movable microswitch to 0 on its scale. On this machine two microswitches have been included to avoid having the movable microswitch to 0 after every estimation of mid-expiratory flow, and to avoid repeated settings of it, if it is desired to estimate the value of timed capacity after the expiration of certain fixed amounts. to set
This modified spirometer is proving of use as an aid to clinical assessment, but it is hoped that its main value will be in the early diagnosis of emphysema and estimation of its progress, by enabling routine serial observations to be made on patients under supervision with chronic chest disease. Its simplicity of operation is a great advantage in outpatient work, where observations have to be made on many patients in a short time. At this clinic health visitors have been trained in its use and make most of the estimations. As it is an adaptation of equipment already in use, unnecessary expenditure has been avoided. The modifications were made by Messrs. Venner Electronics, Ltd., New Malden, Surrey, and our thanks are due to Mr. D. R. Ollington for his help.
S. GILLIS M.D.
Finchley Chest Clinic, London
Lpool
B. A. BUTTERWORTH M.R.C.P.
A MODIFIED FOLEY CATHETER THE soft latex-rubber Foley self-retaining catheter is probably the most popular instrument for continued drainage of the bladder, but, unfortunately, in some cases its pliability makes its passage through the prostatic urethra impossible.
overcome this difficulty, a metal introducer is often used but, with the standard pattern of catheter, the tip of the introducer easily slips through the eye of the catheter and may injure the urethra (see figure, A).
To
A minor but useful modification of the catheter is shown in the figure, B. In this pattern the eyes of the instrument are receded 2 cm. from its tip; the end of the introducer sits comfortably within the cul-de-sac so formed without risk of displacement and can be used with complete safety. The catheter was made for me by Messrs. Wm. Warnes and Co. and is a modification of the Warnes balloon catheter. I wish to thank Mr. E. L. Tugwell for the photograph. Radcliffe Infirmary, Oxford
H. ELLIS M.CH. Oxon., F.R.C.S.
r
New Inventions MODIFICATIONS OF A SPIROMETER FOR TIMED CAPACITY AND MID-EXPIRATORY FLOW MEASUREMENTS THE percentages of the total vital capacity expired in 1, 2, and 3 seconds indicate the degree of obstructive impairment of ventilation (Gaensler 1). Leuallen and Fowler 2 have shown the additional value of measurement of mid-expiratory flow-rates
early emphysema. We describe here a simple modification a spirometer in general use, which records the total vital capacity and any volume expired during a pre-set timeinterval of 0’1-3’0 sec. (in a similar fashion to the modification described by Gaensler) but in addition permits easy and rapid calculation of flow-rates from the start of mid-expiration. The only alteration to the ordinary spirometer is the insertion of a pin into the top of the counterweight to project horizontally through the slot in the counterweight cylinder. The extra attachments (see figure) are: in of
(1) A solenoid mounted on the bracket supporting the recording disc, in such a way that its rod holds the pointer. When the solenoid is energised from the timer, the rod is raised and the pointer released.
(2) A fixed microswitch mounted above and to the side of the counterweight and kept open, when the counterweight is at its highest position, by the counterweight pin. (3) A second microswitch, mounted on the side of the counterweight cylinder, can be moved on a scale calibrated downwards from 0 to 1600 c.cm. (4) A third switch, mounted above the fixed microswitch, determines which of the two microswitches is brought into operation. (5) An electronic timer graduated from 0-1 to 3-0 sec. can be energised by a momentary electrical impulse.
The end of the bracket supporting the recording disc acts as an indicator for the total vital capacity. For timed capacity, the timer is set to the interval required, and the fixed micro1.
2.
Gaensler, E. A. Amer. Rev. Tuberc. 1951, 64, 256. Leuallen, E. C., Fowler, W. S. ibid. 1955, 72, 783.
switch is brought into operation. As the spirometer bell rises, the counterweight descends, its pin closes the microswitch, and the timer is actuated. The pointer is held until it has registered the amount expired during the set interval, after which the solenoid rod is raised and the pointer released to travel round with the disc. For flow-rates from the start of midexpiration, the movable microswitch is brought into operation and is then set to a position on the scale corresponding to a quarter of the total vital capacity. This amount is therefore expired before the counterweight pin closes the microswitch. Consequently the pointer registers the first quarter of the vital capacity together with the amount expired during the interval, after the first quarter, for which the timer is set (0’1-3’0 sec.). By subtraction of the quarter of the vital capacity it is easy to calculate flow-rates from the start of the mid-expiratory
phase. Timed capacity could, of course, be estimated solely by setting the movable microswitch to 0 on its scale. On this machine two microswitches have been included to avoid having the movable microswitch to 0 after every estimation of mid-expiratory flow, and to avoid repeated settings of it, if it is desired to estimate the value of timed capacity after the expiration of certain fixed amounts. to set
This modified spirometer is proving of use as an aid to clinical assessment, but it is hoped that its main value will be in the early diagnosis of emphysema and estimation of its progress, by enabling routine serial observations to be made on patients under supervision with chronic chest disease. Its simplicity of operation is a great advantage in outpatient work, where observations have to be made on many patients in a short time. At this clinic health visitors have been trained in its use and make most of the estimations. As it is an adaptation of equipment already in use, unnecessary expenditure has been avoided. The modifications were made by Messrs. Venner Electronics, Ltd., New Malden, Surrey, and our thanks are due to Mr. D. R. Ollington for his help.
S. GILLIS M.D.
Finchley Chest Clinic, London
Lpool
B. A. BUTTERWORTH M.R.C.P.
A MODIFIED FOLEY CATHETER THE soft latex-rubber Foley self-retaining catheter is probably the most popular instrument for continued drainage of the bladder, but, unfortunately, in some cases its pliability makes its passage through the prostatic urethra impossible.
overcome this difficulty, a metal introducer is often used but, with the standard pattern of catheter, the tip of the introducer easily slips through the eye of the catheter and may injure the urethra (see figure, A).
To
A minor but useful modification of the catheter is shown in the figure, B. In this pattern the eyes of the instrument are receded 2 cm. from its tip; the end of the introducer sits comfortably within the cul-de-sac so formed without risk of displacement and can be used with complete safety. The catheter was made for me by Messrs. Wm. Warnes and Co. and is a modification of the Warnes balloon catheter. I wish to thank Mr. E. L. Tugwell for the photograph. Radcliffe Infirmary, Oxford
H. ELLIS M.CH. Oxon., F.R.C.S.
r