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Fetal respiratory movements: A nomogram for fetal thoracic and abdominal respiratory movements
Fetal respiratory movements: A nomogram for fetal thoracic and abdominal respiratory movements
STEEl\ NELDAM, M.D. Copenhagen, Denmark A nomogram for fetal thoracic and abdominal amplitudes during respiration is presented. The correlation coefficient between the thoracic amplitude and gestational age was 0.973, and that for the abdominal amplitude was 0.920, thus suggesting a strong correlation between gestational age and respiratory amplitude (p < 0.001), whereas no correlation was found between respiratory amplitude and fetal weight. The respiratory amplitudes were not influenced by intake of meals or time of the day when examination was carried out. The respiratory amplitudes were found to be very reproducible (SEM 0.1 mm, N = 42). This new noninvasive method to predict the respiratory distress syndrome seems to be very promising. (AM. J. Oesn:r. GYNECOL. 142:867, 1982.)
EARLIER REPORTS on fetal respiratory movements (FRM) suggested a relationship between the cessation of FRM and the appearance of gasping and fetal hypoxia.~. 2 We thought that it was important to examine the relationship between intrauterine FRM and postnatal respiratory capacity. The most common way to investigate the clinical significance of fetal respiration is by the fetal breathing index (FBI), 3 • 4 which is the time that the fetus breathes during a period of observation, expressed as a percentage of that observation period. But the problem with this parameter is that, because of the enormous variation,'' its clinical significance is of low reliability. Our preliminary report" suggested a relationship between diminished intrauterine respiratory amplitude and postnatal respiratory distress syndrome (RDS). Therefore, in this study, we aimed to investigate the thoracic and abdominal respiratory amplitudes, and to
construct a nomogram for this new noninvasive parameter for postnatal respiratory capacity.
Material and methods
Reprint request\: Steen Neldam, M.D., Department of Obstetrics and G.vnecology YB,402J, Blegdamsvej 9, DK-2100, Copenhagen, Denmark.
Among 35 normal pregnancies which resulted in healthy infants without postnatal respiratory problems, the thoracic and abdominal amplitudes during fetal respiration were measured at 10 different gestational ages in each fetus from the twenty-ninth to forty-first week. The equipment for these measurements consisted of a Honeywell LS-6B fiber optic recorder and an Aloka SSD-202 Echo Camera S, a linear-array scanner with a 64 element probe. The equipment was modified with a select-line facilitv. which was built into the Echo Camera. For indication a bright-up signal was added to the signal on the screen of the SSD-202, at the place of the selected line. This meant that all movements under this line were recorded on the light-sensitive paper on the Honeywell optic recorder. Fig. 1 shows such a recording. The scan of fetal thoracic and abdominal wall movements was performed as a longitudinal scan in the median plane, and the selected line was placed on the middle of the sternum and just beneath the diaphragm (Fig. 2). The amplitude of the thoracic and abdominal movements could then be measured directly on the paper, as shown in Fig. l, when the selected line was placed respectively at T and A (Fig. 2). Most of the scanning was performed before noon and lasted :30 minutes.
J002-9378/82/070867+03$00.30/0© 1982 The C. V. Mosby Co.
867
From the Department of Obstetrics and Gynecology YB,4021 and the Department of Diagnostic Ultrasound Y, RigshospitalPt, Univmity Hospital. Received for publication july 27, 1981. AcceptedNovember2, 1981.
868
Neldam \m.
J
April I, 191<2 Obstet. Gn1ecoL
A5mm
Fig. l. Fetal respiratory amplitude measurements at fortieth gestational week. !'\ormal pregnam\. = thoracic: A = abdominal amplitude.
T
T A
Fig. 2. Diagram of longitudinal scan of fetal thoracic and abdominal wall movements in median plane. Selected line placed on middle of sternum and just beneath diaphragm.
The measurements were done on at least 10 equal respirations.
Resuits Fig. 3 shows the nomogram constructed after 350 scans of 35 normal pregnancies which resulted in healthy infants without postnatal respiratory problems. The .correlation coefficient betv;een the thoracic amplitude and gestational age was 0.973, and that for the abdominal amplitude was 0.920, thus suggesting a strong correlation between gestational age and respiratory amplitude (p < 0.001 ). We have also correlated
the thoracic and abdominal amplitudes to the weight of the fetuses to examine whether the above-mentioned correlation was dependent on increasing weight of the fetus during pregnancy. The correlation coefficients were 0.-t 126 and 0.3451, respectively, in 46 normal pregnancies, and 0.5493 and o.:t~ 74 t!)r the thoracic and abdominal amplitudes, respectiveiv, in 54 diabetic pregnancies which resulted in healthy infants without postnatal respiratory problems. This correlation is not significant (p > 0.1). The intrauterine respiratory amplitude was also investigated in six hospitalized women with preterm labor between the thirty-second and thirty-eighth gestational weeks at R AM, II AM, I :30 PM , 4:30 PM, and 9:30 PM, each time for 30 minutes to evaluate the influence of meals and the hour of the day on this parameter. The thoracic amplitude was ~1.2 ± 0.2 mm (mean± SEM) and the abdominal amplitude was ~~.6 ± 0.3 (N = 30). To investigate the intrapatient variation, 16 normal pregnant women were studied by means of three registrations of 30 minutes' duration in the morning after breakfast. The respiratory J.mp!itudes '".rere again measured over at least 10 equal regular respirations. The thoracic amplitude was 2.9 ± 0.1 mm (mean± SEM),andtheabdominalamplitudewas3.:~ ± O.I (N = 42).
Volume 142 ~umber 7
THORACAL AMPLITL()E
Fetal respiratory movements: Nomogram
rrm
:r ,
NORMAL N=35
r=0,973 p<0,001
CO!'JF!OENCE LIMITS:t2SD
2
WEEKS Cf r-2r0---.24--2-r8--3r2---,36--40"T'"'""-•GESTATION ABDOMINAL AMPLITUDE mm
si
NORMAL N=35
r=0,920 p<0,001 COI\FIDENCE LIMITS ±2SD
4
3
2
WEEKS OF r-2r0---,24--28-r--3r2---,3.-6-4·0----. GESTATION
Fig. 3. Nomogram based on 350 scans in 35 normal pregnancies which eventuated in healthy infants without postnatal respiratory problems.
869
Comment This study showed that the fetal thoracic and abdominal respiratory amplitudes increase significantly (p < 0.001) during pregnancy, and that the confidence limits are reasonably narrow. Fetal respiratory amplitude (FRA) is also very reproducible and not influenced, as is the FBI, by the hour of the day or by meals. 4 The lack of correlation between FRA and fetal weight, but positive correlation of FRA to gestational age and normal postnatal respiratory capacity, indicates that the size and shape of the respiratory amplitude depend on the neuromuscular development of the respiratory muscles and the compliance of the lungs and thoracic cage. The clinical applicability of this parameter was pointed out in our preliminary study,5 in which seven fetuses whose respiratory amplitude diminished more than 2 SD developed RDS (2,154 ± 192 g, mean± SEM). The amniotic lecithin was normal in three of those cases, and not measured in the other four. The other 310 fetuses had normal respiratory amplitudes and no postnatal respiratory problems." Measurement of fetal respiratory amplitude seems to be a means by which to predict postnatal respiratory problems in infants. Further investigation of this new noninvasive method is recommended. I wish to express my gratitude to Arne S9\rensen, M.Sc.E.E., Medical Technical Department, Rigshospitalet, for his modifications of the equipment.
From the thirty-eighth gestational week, the abdominal amplitude was found to be significantiy greater than the thoracic amplitude (p < 0.05, Wilcoxoniviann-\Vhitney tank sum test).
REFERENCES I. Boddy, K., and Dawes, G. S.: Fetal breathing, Br. Med. Bull. 31:3, 1975. 2. Trudinger, B. J., Gordon, B., Grudzenskas, J. G .. Hull, M.G. R., Lewis, P.J., and Arrans, M. E. L.: Fetal breathing movements and other test of fetal well-being. A comparative evaluation, Br. Med.J. 2:~77, 1979. 3. Manning, F. A., Platt, L. D., and Sipos, L.: Antepartum
fetal evaluation: Development of a fetal biophysical prohle, AM.j. 0BSTET. GYNECOL. 136:787, 1980. 4. Lewis, P., and Boylan, P.: Fetal breathing. A review, AM.j. 0BSTET. GYNECOL. 134:587. 1979. 5. Neldam, S.: Fetal body and respiratory movements, in Kurjak, A., Rippmann, E. T., and Sulovic, V., editors: Current status of EPH Gestosis, International Congress Series No~ 534, Amsterdam, 1981, Excerpta Medica, pp. 224-229.
STEEl\ NELDAM, M.D. Copenhagen, Denmark A nomogram for fetal thoracic and abdominal amplitudes during respiration is presented. The correlation coefficient between the thoracic amplitude and gestational age was 0.973, and that for the abdominal amplitude was 0.920, thus suggesting a strong correlation between gestational age and respiratory amplitude (p < 0.001), whereas no correlation was found between respiratory amplitude and fetal weight. The respiratory amplitudes were not influenced by intake of meals or time of the day when examination was carried out. The respiratory amplitudes were found to be very reproducible (SEM 0.1 mm, N = 42). This new noninvasive method to predict the respiratory distress syndrome seems to be very promising. (AM. J. Oesn:r. GYNECOL. 142:867, 1982.)
EARLIER REPORTS on fetal respiratory movements (FRM) suggested a relationship between the cessation of FRM and the appearance of gasping and fetal hypoxia.~. 2 We thought that it was important to examine the relationship between intrauterine FRM and postnatal respiratory capacity. The most common way to investigate the clinical significance of fetal respiration is by the fetal breathing index (FBI), 3 • 4 which is the time that the fetus breathes during a period of observation, expressed as a percentage of that observation period. But the problem with this parameter is that, because of the enormous variation,'' its clinical significance is of low reliability. Our preliminary report" suggested a relationship between diminished intrauterine respiratory amplitude and postnatal respiratory distress syndrome (RDS). Therefore, in this study, we aimed to investigate the thoracic and abdominal respiratory amplitudes, and to
construct a nomogram for this new noninvasive parameter for postnatal respiratory capacity.
Material and methods
Reprint request\: Steen Neldam, M.D., Department of Obstetrics and G.vnecology YB,402J, Blegdamsvej 9, DK-2100, Copenhagen, Denmark.
Among 35 normal pregnancies which resulted in healthy infants without postnatal respiratory problems, the thoracic and abdominal amplitudes during fetal respiration were measured at 10 different gestational ages in each fetus from the twenty-ninth to forty-first week. The equipment for these measurements consisted of a Honeywell LS-6B fiber optic recorder and an Aloka SSD-202 Echo Camera S, a linear-array scanner with a 64 element probe. The equipment was modified with a select-line facilitv. which was built into the Echo Camera. For indication a bright-up signal was added to the signal on the screen of the SSD-202, at the place of the selected line. This meant that all movements under this line were recorded on the light-sensitive paper on the Honeywell optic recorder. Fig. 1 shows such a recording. The scan of fetal thoracic and abdominal wall movements was performed as a longitudinal scan in the median plane, and the selected line was placed on the middle of the sternum and just beneath the diaphragm (Fig. 2). The amplitude of the thoracic and abdominal movements could then be measured directly on the paper, as shown in Fig. l, when the selected line was placed respectively at T and A (Fig. 2). Most of the scanning was performed before noon and lasted :30 minutes.
J002-9378/82/070867+03$00.30/0© 1982 The C. V. Mosby Co.
867
From the Department of Obstetrics and Gynecology YB,4021 and the Department of Diagnostic Ultrasound Y, RigshospitalPt, Univmity Hospital. Received for publication july 27, 1981. AcceptedNovember2, 1981.
868
Neldam \m.
J
April I, 191<2 Obstet. Gn1ecoL
A5mm
Fig. l. Fetal respiratory amplitude measurements at fortieth gestational week. !'\ormal pregnam\. = thoracic: A = abdominal amplitude.
T
T A
Fig. 2. Diagram of longitudinal scan of fetal thoracic and abdominal wall movements in median plane. Selected line placed on middle of sternum and just beneath diaphragm.
The measurements were done on at least 10 equal respirations.
Resuits Fig. 3 shows the nomogram constructed after 350 scans of 35 normal pregnancies which resulted in healthy infants without postnatal respiratory problems. The .correlation coefficient betv;een the thoracic amplitude and gestational age was 0.973, and that for the abdominal amplitude was 0.920, thus suggesting a strong correlation between gestational age and respiratory amplitude (p < 0.001 ). We have also correlated
the thoracic and abdominal amplitudes to the weight of the fetuses to examine whether the above-mentioned correlation was dependent on increasing weight of the fetus during pregnancy. The correlation coefficients were 0.-t 126 and 0.3451, respectively, in 46 normal pregnancies, and 0.5493 and o.:t~ 74 t!)r the thoracic and abdominal amplitudes, respectiveiv, in 54 diabetic pregnancies which resulted in healthy infants without postnatal respiratory problems. This correlation is not significant (p > 0.1). The intrauterine respiratory amplitude was also investigated in six hospitalized women with preterm labor between the thirty-second and thirty-eighth gestational weeks at R AM, II AM, I :30 PM , 4:30 PM, and 9:30 PM, each time for 30 minutes to evaluate the influence of meals and the hour of the day on this parameter. The thoracic amplitude was ~1.2 ± 0.2 mm (mean± SEM) and the abdominal amplitude was ~~.6 ± 0.3 (N = 30). To investigate the intrapatient variation, 16 normal pregnant women were studied by means of three registrations of 30 minutes' duration in the morning after breakfast. The respiratory J.mp!itudes '".rere again measured over at least 10 equal regular respirations. The thoracic amplitude was 2.9 ± 0.1 mm (mean± SEM),andtheabdominalamplitudewas3.:~ ± O.I (N = 42).
Volume 142 ~umber 7
THORACAL AMPLITL()E
Fetal respiratory movements: Nomogram
rrm
:r ,
NORMAL N=35
r=0,973 p<0,001
CO!'JF!OENCE LIMITS:t2SD
2
WEEKS Cf r-2r0---.24--2-r8--3r2---,36--40"T'"'""-•GESTATION ABDOMINAL AMPLITUDE mm
si
NORMAL N=35
r=0,920 p<0,001 COI\FIDENCE LIMITS ±2SD
4
3
2
WEEKS OF r-2r0---,24--28-r--3r2---,3.-6-4·0----. GESTATION
Fig. 3. Nomogram based on 350 scans in 35 normal pregnancies which eventuated in healthy infants without postnatal respiratory problems.
869
Comment This study showed that the fetal thoracic and abdominal respiratory amplitudes increase significantly (p < 0.001) during pregnancy, and that the confidence limits are reasonably narrow. Fetal respiratory amplitude (FRA) is also very reproducible and not influenced, as is the FBI, by the hour of the day or by meals. 4 The lack of correlation between FRA and fetal weight, but positive correlation of FRA to gestational age and normal postnatal respiratory capacity, indicates that the size and shape of the respiratory amplitude depend on the neuromuscular development of the respiratory muscles and the compliance of the lungs and thoracic cage. The clinical applicability of this parameter was pointed out in our preliminary study,5 in which seven fetuses whose respiratory amplitude diminished more than 2 SD developed RDS (2,154 ± 192 g, mean± SEM). The amniotic lecithin was normal in three of those cases, and not measured in the other four. The other 310 fetuses had normal respiratory amplitudes and no postnatal respiratory problems." Measurement of fetal respiratory amplitude seems to be a means by which to predict postnatal respiratory problems in infants. Further investigation of this new noninvasive method is recommended. I wish to express my gratitude to Arne S9\rensen, M.Sc.E.E., Medical Technical Department, Rigshospitalet, for his modifications of the equipment.
From the thirty-eighth gestational week, the abdominal amplitude was found to be significantiy greater than the thoracic amplitude (p < 0.05, Wilcoxoniviann-\Vhitney tank sum test).
REFERENCES I. Boddy, K., and Dawes, G. S.: Fetal breathing, Br. Med. Bull. 31:3, 1975. 2. Trudinger, B. J., Gordon, B., Grudzenskas, J. G .. Hull, M.G. R., Lewis, P.J., and Arrans, M. E. L.: Fetal breathing movements and other test of fetal well-being. A comparative evaluation, Br. Med.J. 2:~77, 1979. 3. Manning, F. A., Platt, L. D., and Sipos, L.: Antepartum
fetal evaluation: Development of a fetal biophysical prohle, AM.j. 0BSTET. GYNECOL. 136:787, 1980. 4. Lewis, P., and Boylan, P.: Fetal breathing. A review, AM.j. 0BSTET. GYNECOL. 134:587. 1979. 5. Neldam, S.: Fetal body and respiratory movements, in Kurjak, A., Rippmann, E. T., and Sulovic, V., editors: Current status of EPH Gestosis, International Congress Series No~ 534, Amsterdam, 1981, Excerpta Medica, pp. 224-229.