British Journcil of Obstetrics und Gynuecology
March 1990, Vol. 97, pp. 277-279
CORRESPONDENCE Uterine activity during spontaneous labour after previous lower-segment caesarean section Dear Sir, Arulkumaran et ul. [ Br J Obstet Gynuecol(l989) 96, 933-9381 describc quantification of intrauterine pressure by integration of its recording, which I and others did in the early 1970s.While this calculation of uterine activity was able to separate the various pathological labour groups, in my experience it was of no more clinical use than uterine palpation in the individual patient. I doubt thc authors’ claim that ‘The use of an intrauterine catheter provides accurate information and enables the uterine activity to be computed’ for a simple reason. Once the mcmbranes are ruptured, the intra-amniotic cavity is no longer a closed system and Pascal’s law does not apply. With leakage of fluid, there can be isolated pockets of different intrauterine pressures during contractions. For as stated by Csapo (1970),‘When an open catheter is placed intra-amniotically from below, through a micropuncture of the amniotic membrane. the intrauterine pressure is accurately recorded for a short period until the leakage of amniotic fluid seriously distorts it’. Neuman et al. (1972) monitored 12 parturients with two transcervical catheters and one intrauterine pressure transduccr simultaneously. These investigators found a coefficient of variation >23% in intrauterine pressure rccordings, and concludcd that ‘no singlc utcrine pressure observation is an accurate reflection of uterine pressure during labor’. Using either multiple open intrauterine catheters o r solid transducer-tipped catheters, I have found 15-28% variations in pressure readings between two recorders in the same uterine contraction. Given the interest in the use of uterinework calculation technique in Europe, I believc that these investigators should confirm their assumptions of the precision of intrauterine pressure recordings after mcmbranc rupture before proceeding with future studies. Robert C. Goodlin I00 Jusmine St Denver, CO 80204, USA
References Arulkumaran S . , Gibb D. M. F., Ingemarsson I.. Kitchencr H. C. & Ratnam S. S. (1989) Uterine activity during spontaneous labour after previous lower-segment caesarean section. Br J Obstel GynaecolY6,933-938. Csapo A. (1970) The diagnostic significance of thc intrauterine prcssurc. Obstet Gynecol Sun, 25, 403-435. Neuman M. R., Jordan J. A . , Roux J. F. & Knoke J. D. (1972) Validity of intrauterine pressure
measurements with transcervical intra-amniotic catheters and an intra-amnioticminiature pressure transducer duringlabor. Gynecollnvest 3,165-175.
Authors’ reply Dear Sir, We thank Dr Goodlin for his comments. In the absence of a reference we have been unable to tracc his work to which hc alludes. His quotation from the paper by Csapo (1970) is incomplete; in thc same paragraph Csapo states ‘The changes observed in intrauterine pressure are determined by the extent of rupture, thc position of the mother and the leakage control of the fetal head. Only when the descending head completely prevents the Icakage of amniotic fluid is the loss of pressure corrected’. Neuman et al. (1972) compared pressures derived from fluid-filled catheters with those from an intrauterine sensor. They showed only slight differences between these methods which are understandable given the inherent inaccuracy of fluid-filled devices. The intrauterine catheter provides information about the pressure within the pocket in which the transducer tip is lying. This pressure may not be representative of the entire intrauterine cavity if there are different pockets of amniotic fluid. However, if the transducer tips lie in different pockets, the fact that these catheters passcd transcervically reached thcse spaces suggests that there is some communication at least by a film of fluid and the pressure should be equal according to Pascal’s law. Steer et al. (1978) compared the simultaneous pressure readings from a Gaeltec catheter and fluid-filled
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March 1990, Vol. 97, pp. 277-279
CORRESPONDENCE Uterine activity during spontaneous labour after previous lower-segment caesarean section Dear Sir, Arulkumaran et ul. [ Br J Obstet Gynuecol(l989) 96, 933-9381 describc quantification of intrauterine pressure by integration of its recording, which I and others did in the early 1970s.While this calculation of uterine activity was able to separate the various pathological labour groups, in my experience it was of no more clinical use than uterine palpation in the individual patient. I doubt thc authors’ claim that ‘The use of an intrauterine catheter provides accurate information and enables the uterine activity to be computed’ for a simple reason. Once the mcmbranes are ruptured, the intra-amniotic cavity is no longer a closed system and Pascal’s law does not apply. With leakage of fluid, there can be isolated pockets of different intrauterine pressures during contractions. For as stated by Csapo (1970),‘When an open catheter is placed intra-amniotically from below, through a micropuncture of the amniotic membrane. the intrauterine pressure is accurately recorded for a short period until the leakage of amniotic fluid seriously distorts it’. Neuman et al. (1972) monitored 12 parturients with two transcervical catheters and one intrauterine pressure transduccr simultaneously. These investigators found a coefficient of variation >23% in intrauterine pressure rccordings, and concludcd that ‘no singlc utcrine pressure observation is an accurate reflection of uterine pressure during labor’. Using either multiple open intrauterine catheters o r solid transducer-tipped catheters, I have found 15-28% variations in pressure readings between two recorders in the same uterine contraction. Given the interest in the use of uterinework calculation technique in Europe, I believc that these investigators should confirm their assumptions of the precision of intrauterine pressure recordings after mcmbranc rupture before proceeding with future studies. Robert C. Goodlin I00 Jusmine St Denver, CO 80204, USA
References Arulkumaran S . , Gibb D. M. F., Ingemarsson I.. Kitchencr H. C. & Ratnam S. S. (1989) Uterine activity during spontaneous labour after previous lower-segment caesarean section. Br J Obstel GynaecolY6,933-938. Csapo A. (1970) The diagnostic significance of thc intrauterine prcssurc. Obstet Gynecol Sun, 25, 403-435. Neuman M. R., Jordan J. A . , Roux J. F. & Knoke J. D. (1972) Validity of intrauterine pressure
measurements with transcervical intra-amniotic catheters and an intra-amnioticminiature pressure transducer duringlabor. Gynecollnvest 3,165-175.
Authors’ reply Dear Sir, We thank Dr Goodlin for his comments. In the absence of a reference we have been unable to tracc his work to which hc alludes. His quotation from the paper by Csapo (1970) is incomplete; in thc same paragraph Csapo states ‘The changes observed in intrauterine pressure are determined by the extent of rupture, thc position of the mother and the leakage control of the fetal head. Only when the descending head completely prevents the Icakage of amniotic fluid is the loss of pressure corrected’. Neuman et al. (1972) compared pressures derived from fluid-filled catheters with those from an intrauterine sensor. They showed only slight differences between these methods which are understandable given the inherent inaccuracy of fluid-filled devices. The intrauterine catheter provides information about the pressure within the pocket in which the transducer tip is lying. This pressure may not be representative of the entire intrauterine cavity if there are different pockets of amniotic fluid. However, if the transducer tips lie in different pockets, the fact that these catheters passcd transcervically reached thcse spaces suggests that there is some communication at least by a film of fluid and the pressure should be equal according to Pascal’s law. Steer et al. (1978) compared the simultaneous pressure readings from a Gaeltec catheter and fluid-filled
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