920
glycaemic control to congenital malformations or to preconception care, which has been established in so many other studies. Our experience is that diabetic women who do not seek preconception care may differ socioeconomically from those who do, but the diabetes of those who do not is not inherently more difficult to treat since after four weeks of outpatient management they achieve blood glucose and glycohaemoglobin values similar to those who had preconception care. We suspect that Gregory and Tattersall’s antipathy against pre-pregnancy care is caused by the low rate of anomalies (3/139, 2-2%) in a series they reported to the Royal College of Physicians. Their success without preconception care is probably attributable to improved diabetes care for all women in their community so that unplanned pregnancies are not at great risk for congenital malformations. Similar success has been reported from Sweden6 and improved diabetic care for all is an important public health goal. However, until it is achieved widely, we believe that recruiting diabetic women for preconception care is a cost-effective method to reduce the most serious cause of perinatal mortality and morbidity
relation of
in infants of diabetic mothers. Department of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of California, San Francisco. California 94143, USA
JOHN L. KITZMILLER THOMAS BUCHANAN DONALD COUSTAN
1 Furhmann K, Reiher H, Semmler K, et al. Prevention of congenital malformation infants of insulin-dependent diabetic mothers. Diabetes Care 1983; 6: 219-23. 2. Damm P, Molsted-Pedersen L. Significant decrease in congenital malformations
3. 4.
5.
6.
m
in
newborn infants of an unselected population of diabetic women Am J Obstet Gynecol 1989; 161: 1163-67. Steel JM, Johnstone FD, Hepbum DA, Smith AF. Can pre pregnancy care of diabetic women reduce the risk of abnormal babies? BMJ 1990, 301: 1070-74. Kitzmiller JL, Gavin LA, Gin GD, Jovanovic-Petersen L, Main EK, Zigrang WD. Preconception care of diabetes: glycemic control prevents congenital anomalies JAMA 1991; 265: 731-36. Jovanovic L, Druzin M, Peterson CM. Effect of euglycaemia on the outcome of pregnancy in insulin-dependent diabetic women as compared to normal control subjects. Am J Med 1981; 71: 921-27. Hanson U, Persson B, Thunell S. Relationship between haemoglobin A1C in early type 1 (insulin dependent) diabetic pregnancy and the occurrence of spontaneous abortion and fetal malformation in Sweden Diabetologia 1990; 33: 100-04.
Inappropriate sensor application in pulse oximetry SIR,-Professor Southall and Dr Samuels (Aug 22, p 481) report an artifact during neonatal application of pulse oximetry. This finding has also been described for adult finger probes’ and for reflectance sensors in fetal pulse oximetry.2 In each case, false low readings were seen when sensors were not well applied. We have investigated this effect under laboratory conditions, with two wavelengths commonly used in pulse oximetry (660 and 940 nm), by use of a set-up for separate analysis of the pulsatile (AC) and non-pulsatile (DC) components of the signal. An investigator’s finger was stabilised in a purpose-built mould from where the distance to the sensors could be varied in 1 mm steps. Readings were made while the plethysmographic waveform confirmed arterial modulation of the signal. Results were calculated as R values:
AC(660)/DC(660) AC(940)/DC(940) Through an oximeter’s algorithm, the R value is inversely related to R =
the reading it gives for the oxygen saturation. We showed that if light is allowed to shunt from light source to photo-detector by reflection off a skin surface, the individual components of the signal are affected differently, with the overall result that R increases with the distance between finger and sensors (figure). By contrast, despite increasing finger-to-sensor gap, R remains constant if shunting is avoided; this occurs either in proper transmission mode or if at least one of the sensor pairs makes contact, thereby ensuring that all of the received light signal has traversed tissue. These data clearly show that even a small gap between sensors and skin can give rise to substantially false measurements. Using commercial oximeters, we have been able to artificially reduce the oxygen saturation reading on a healthy adult finger from 99% to 61% through this effect alone, while still obtaining an arterial pulse waveform.
R values for distances of 0
(full contact) to 4 mm between finger. []without shunting; with shunting, due to reflection of light from skin
sensors
and
surface
With the continually expanding use of pulse oximetry in various clinical settings, manufacturers should take heed of such potentially serious artifacts and incorporate software into their oximeters that will exclude the generation of nonsense readings. Perinatal Research and Monitoring Unit, and Biomedical Engineering Unit. Queen’s Medical Centre, Nottingham NG7 2UH, UK
1. Kelleher JF, Ruff RH. The Penumbra effect.
JASON U. GARDOSI DAMIANOS DAMIANOU CATHARINA M. SCHRAM
vasomotion-dependent pulse oximeter
artifact due to probe malposition. Anesthesiology 1989, 51: 787-91. 2. Gardosi JO, Schram CM, Symonds EM. Adaptation of pulse oximetry monitoring during labour. Lancet 1991, 337: 1265-67.
Intravenous
to
fetal
immunoglobulin for multifocal motor neuropathy
SIR,-Dr Charles and colleagues (July 18, p 182) record improvement with intravenous immunoglobulin therapy (IVIG) in a patient with multifocal motor neuropathy (MMN).’ We report our experience in 5 patients with MMN receiving monthly IVIG, who were assessed serially by quantitative myometry and electrophysiology. 1 patient has now been followed for 12 months. 4 men and 1 woman (aged 46-54 years) were investigated prospectively. Disease duration at entry was 14 years in the woman and 10, 3, 2, and 1-5 years, respectively, in the men. All had slowly progressive unilateral or bilateral arm weakness and atrophy with electrophysiological evidence of denervation and multifocal conduction block typical of MMN.’ 2 had failed to improve with corticosteroids, and 2 had undergone thoracic outlet decompression. Ganglioside antibody titres were done in 4 patients at Dr A. Pestronk’s laboratory, Washington University, St Louis. 3 had very high titres, ranging from 10 500 IgM anti-GM, and 15 188 IgM anti-asialo-GM to a low of 1060 IgM anti-GM,; in the fourth case, anti-GM, antibodies were not detected. Informed consent was obtained before administration of IVIG 30 g daily for 5 days (Intragam, Commonwealth Serum Laboratories, Australia). Electrophysiological studies and quantitative myometry were done before treatment. At about monthly intervals patients received a further 30 g IVIG daily for 3 days, and had nerve conduction studies and myometry.
glycaemic control to congenital malformations or to preconception care, which has been established in so many other studies. Our experience is that diabetic women who do not seek preconception care may differ socioeconomically from those who do, but the diabetes of those who do not is not inherently more difficult to treat since after four weeks of outpatient management they achieve blood glucose and glycohaemoglobin values similar to those who had preconception care. We suspect that Gregory and Tattersall’s antipathy against pre-pregnancy care is caused by the low rate of anomalies (3/139, 2-2%) in a series they reported to the Royal College of Physicians. Their success without preconception care is probably attributable to improved diabetes care for all women in their community so that unplanned pregnancies are not at great risk for congenital malformations. Similar success has been reported from Sweden6 and improved diabetic care for all is an important public health goal. However, until it is achieved widely, we believe that recruiting diabetic women for preconception care is a cost-effective method to reduce the most serious cause of perinatal mortality and morbidity
relation of
in infants of diabetic mothers. Department of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of California, San Francisco. California 94143, USA
JOHN L. KITZMILLER THOMAS BUCHANAN DONALD COUSTAN
1 Furhmann K, Reiher H, Semmler K, et al. Prevention of congenital malformation infants of insulin-dependent diabetic mothers. Diabetes Care 1983; 6: 219-23. 2. Damm P, Molsted-Pedersen L. Significant decrease in congenital malformations
3. 4.
5.
6.
m
in
newborn infants of an unselected population of diabetic women Am J Obstet Gynecol 1989; 161: 1163-67. Steel JM, Johnstone FD, Hepbum DA, Smith AF. Can pre pregnancy care of diabetic women reduce the risk of abnormal babies? BMJ 1990, 301: 1070-74. Kitzmiller JL, Gavin LA, Gin GD, Jovanovic-Petersen L, Main EK, Zigrang WD. Preconception care of diabetes: glycemic control prevents congenital anomalies JAMA 1991; 265: 731-36. Jovanovic L, Druzin M, Peterson CM. Effect of euglycaemia on the outcome of pregnancy in insulin-dependent diabetic women as compared to normal control subjects. Am J Med 1981; 71: 921-27. Hanson U, Persson B, Thunell S. Relationship between haemoglobin A1C in early type 1 (insulin dependent) diabetic pregnancy and the occurrence of spontaneous abortion and fetal malformation in Sweden Diabetologia 1990; 33: 100-04.
Inappropriate sensor application in pulse oximetry SIR,-Professor Southall and Dr Samuels (Aug 22, p 481) report an artifact during neonatal application of pulse oximetry. This finding has also been described for adult finger probes’ and for reflectance sensors in fetal pulse oximetry.2 In each case, false low readings were seen when sensors were not well applied. We have investigated this effect under laboratory conditions, with two wavelengths commonly used in pulse oximetry (660 and 940 nm), by use of a set-up for separate analysis of the pulsatile (AC) and non-pulsatile (DC) components of the signal. An investigator’s finger was stabilised in a purpose-built mould from where the distance to the sensors could be varied in 1 mm steps. Readings were made while the plethysmographic waveform confirmed arterial modulation of the signal. Results were calculated as R values:
AC(660)/DC(660) AC(940)/DC(940) Through an oximeter’s algorithm, the R value is inversely related to R =
the reading it gives for the oxygen saturation. We showed that if light is allowed to shunt from light source to photo-detector by reflection off a skin surface, the individual components of the signal are affected differently, with the overall result that R increases with the distance between finger and sensors (figure). By contrast, despite increasing finger-to-sensor gap, R remains constant if shunting is avoided; this occurs either in proper transmission mode or if at least one of the sensor pairs makes contact, thereby ensuring that all of the received light signal has traversed tissue. These data clearly show that even a small gap between sensors and skin can give rise to substantially false measurements. Using commercial oximeters, we have been able to artificially reduce the oxygen saturation reading on a healthy adult finger from 99% to 61% through this effect alone, while still obtaining an arterial pulse waveform.
R values for distances of 0
(full contact) to 4 mm between finger. []without shunting; with shunting, due to reflection of light from skin
sensors
and
surface
With the continually expanding use of pulse oximetry in various clinical settings, manufacturers should take heed of such potentially serious artifacts and incorporate software into their oximeters that will exclude the generation of nonsense readings. Perinatal Research and Monitoring Unit, and Biomedical Engineering Unit. Queen’s Medical Centre, Nottingham NG7 2UH, UK
1. Kelleher JF, Ruff RH. The Penumbra effect.
JASON U. GARDOSI DAMIANOS DAMIANOU CATHARINA M. SCHRAM
vasomotion-dependent pulse oximeter
artifact due to probe malposition. Anesthesiology 1989, 51: 787-91. 2. Gardosi JO, Schram CM, Symonds EM. Adaptation of pulse oximetry monitoring during labour. Lancet 1991, 337: 1265-67.
Intravenous
to
fetal
immunoglobulin for multifocal motor neuropathy
SIR,-Dr Charles and colleagues (July 18, p 182) record improvement with intravenous immunoglobulin therapy (IVIG) in a patient with multifocal motor neuropathy (MMN).’ We report our experience in 5 patients with MMN receiving monthly IVIG, who were assessed serially by quantitative myometry and electrophysiology. 1 patient has now been followed for 12 months. 4 men and 1 woman (aged 46-54 years) were investigated prospectively. Disease duration at entry was 14 years in the woman and 10, 3, 2, and 1-5 years, respectively, in the men. All had slowly progressive unilateral or bilateral arm weakness and atrophy with electrophysiological evidence of denervation and multifocal conduction block typical of MMN.’ 2 had failed to improve with corticosteroids, and 2 had undergone thoracic outlet decompression. Ganglioside antibody titres were done in 4 patients at Dr A. Pestronk’s laboratory, Washington University, St Louis. 3 had very high titres, ranging from 10 500 IgM anti-GM, and 15 188 IgM anti-asialo-GM to a low of 1060 IgM anti-GM,; in the fourth case, anti-GM, antibodies were not detected. Informed consent was obtained before administration of IVIG 30 g daily for 5 days (Intragam, Commonwealth Serum Laboratories, Australia). Electrophysiological studies and quantitative myometry were done before treatment. At about monthly intervals patients received a further 30 g IVIG daily for 3 days, and had nerve conduction studies and myometry.
