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Biomedical subjects

G Lingman

Publications and source records attributed to G Lingman.

At least 37 records · Page 2Linked to original sources
PubMed1991

Placental morphology in relation to umbilical artery blood velocity waveforms.

The association between umbilical artery flow velocity waveforms, placental morphology and arterial vascular pattern was investigated in 30 pregnant women at risk for intra-uterine growth retardation. The blood velocity waveform was assessed in the umbilical arteries with pulsed Doppler ultrasound. Placentas from fetuses with an end-diastolic zero flow were small and thick with an extrachorial configuration, marginal cord insertion, magistral or mixed allantochorial vessel pattern and few cotyledons. The incidence and the extension of gross lesions were slightly increased in these placentas compared to placentas from fetuses with a normal S/D ratio (peak systolic velocity/minimum diastolic velocity). Placentas from fetuses with an increased S/D ratio (greater than +2SD) were large and thin with a high maximum diameter/maximum thickness ratio. Heavily smoking mothers were overrepresented in the group, with an increased S/D ratio and corresponding SGA infants. End-diastolic zero flow in the umbilical artery was strongly correlated with placental developmental abnormalities.

Angiography↗
PubMed1991

Myocardial contractility in the anemic human fetus.

Severely anemic fetuses in Rh-isoimmunized pregnancies are often found to have hydrops and the etiology is debated. Fifteen fetal blood samplings were performed in nine fetuses for determination of the degree of anemia and of the acid-base balance. Waveform analysis was performed on the maximum blood velocity curve in the umbilical arteries and the ascending fetal aorta, obtained by means of a pulsed Doppler technique. The blood acceleration in the ascending aorta increased down to a hematocrit of 0.18 and a hemoglobin concentration of 65 g/l, which might constitute a cardiac response to the anemia aimed at maintaining the peripheral blood circulation. Below these levels there was a decrease in blood acceleration, which could be caused by impaired cardiac oxygenation. This relationship could be described as a six-power function (r = 0.87; p = 0.032). A second-power relationship was found between the umbilical artery pulsatility index and the blood acceleration in the fetal ascending aorta (r = 0.64; p = 0.0418), which suggests that the cardiac pump function can alter the blood velocity waveform in the umbilical arteries.

Journal Article↗
PubMed1991

Diameters of the common carotid artery and aorta change in different directions during acute asphyxia in the fetal lamb.

The aim of this experimental ultrasound study on six fetal lambs was to evaluate how blood flow variables and vessel diameters of the descending aorta and the common carotid artery change during fetal asphyxia in the acute preparation. When acute asphyxia was induced by obstructing the maternal aortic blood flow all fetuses reacted with significant decrease in the aortic diameter and blood flow. In the common carotid artery vessel diameter and the blood flow increased significantly. The results support the theory of a brain sparing effect during fetal distress with significant changes of blood vessel diameters occurring in opposite directions in the aorta and the common carotid artery, thereby contributing to the centralisation of circulation.

Animals↗
PubMed1990

Recording of blood flow velocity waveforms in the uteroplacental and umbilical circulation: reproducibility study and comparison of pulsed and continuous wave Doppler ultrasonography.

Reproducibility of the blood flow velocity waveforms (FVW) recorded from the umbilical artery and the arcuate arteries on the right and left side of the placenta was examined in 8 women with normal pregnancies and anterior placentas. The FVW were recorded using a 2-MHz pulsed Doppler ultrasound system in combination with a real-time linear-array scanner. The FVW were characterized by the pulsatility index (PI) and systolic/diastolic (S/D) ratio. For the PI, the mean coefficients of variation between six operator pairs in the umbilical artery and the left and right arcuate arteries were 8.4%, 26%, and 21.5%, respectively. These findings suggest that, in clinical practice, the umbilical artery FVW is reproducible, but the usefulness of arcuate artery FVW is limited by the wide variation of Doppler signals. Paired recordings of FVW were obtained from the umbilical, arcuate, and uterine arteries using pulsed wave and continuous wave Doppler ultrasonography in a randomized order in another 21 pregnant women with anterior placentas. There was no difference between the two Doppler modes for any of the measured waveform indices.

Arteries↗
PubMed1990

Anal sphincter function after delivery: a prospective study in women with sphincter rupture and controls.

Twenty-one consecutive women with anal sphincter muscle rupture during delivery (0.79%) and 15 controls were examined. The anal sphincter was immediately repaired in the study group and the function determined with anal profilometry at 3 days and 3 months after delivery, and in ten of the patients after 12 months. Anal sphincter strength was reduced soon after delivery in the controls but regained normal strength within 3 months. In the anal sphincter rupture group, an improvement was found over the first 3 months after delivery, but afterwards no further change occurred. The anal sphincter strength was significantly reduced compared to the control group, both soon after delivery and after 3 months. Their voluntary anal pressure increased from 1.7 kPa immediately after delivery to 3.2 kPa at 3 months in the study group and the corresponding values in the control group were 4.0 and 6.5 kPa, respectively. For the closing pressure, that is the resting pressure minus the rectal pressure, the values in the study group were 4.2 and 6.7 kPa, and in the control group 7.2 and 9.4 kPa, respectively. In the women with anal sphincter rupture, however, a significantly increased frequency of gas incontinence was found.

Adult↗
PubMed1990

Evaluation of blood flow velocity waveform in an animal model.

Blood flow velocity waveforms in the abdominal aorta of three anesthetized pigs were recorded by a combined 3.5-MHz real-time and 2-MHz pulsed-Doppler ultrasound. The flow velocity waveforms were analyzed for pulsatility index, systolic to diastolic ratio, rising slope, descending slope, and the minimum diastolic velocity, and then were compared with volume blood flow measured by electromagnetic flowmeter (Q), mean arterial pressure (MAP), and total peripheral resistance (TPR). Total peripheral resistance was calculated according to the formula TPR = MAP/Q. A total of 111 recordings were performed over a range of heart rate: 90-250 beats/min, of Q: 65-1318 mL/min, of MAP: 72-165 mmHg and of total peripheral resistance 0.10-2.17 mmHg x min/mL. A significant positive correlation was found between pulsatility index and total peripheral resistance (correlation coefficient r ranging 0.64-0.87) and between systolic to diastolic ratio and total peripheral resistance (r: 0.59-0.83). The minimum diastolic velocity showed a negative correlation to TPR(r: -0.68 - -0.76). The pulsatility index was dependent on the heart rate, mean arterial pressure and rising slope; however, the relations were not consistent in all experiments. The results indicate that the pulsatility index is a good indicator of the flow velocity waveform changes depending on changes in the peripheral vascular resistance, and that the relationship between the total peripheral resistance and pulsatility index is linear. The systolic to diastolic ratio proved to be comparable even though it is somewhat less effective in performance than the pulsatility index.

Animals↗
PubMed1990

Cerebral blood flow during labor in the human fetus.

A method is described for recording blood flow velocity waveforms from fetal cerebral vessels during labor, using a 2 MHz pulsed Doppler ultrasound technique. Fifteen healthy women with uncomplicated pregnancies and labor without signs of fetal distress participated in the study. With membranes ruptured and cervix orifice open 4-9 cm, the Doppler transducer was placed transvaginally on the fetal skull and the Doppler shift signals from the middle cerebral artery were located. The maximum velocity waveforms were recorded before, during and after uterine contractions and analysed off-line for pulsatility index (PI). No differences in the PI were found with regard to the uterine contractions. The results suggest an unchanged peripheral resistance in the fetal cerebral vascular bed during the first stage of normal labor.

Blood Flow Velocity↗
PubMed1989

Noninvasive assessment of cranial blood circulation in the fetus.

The blood velocity in the common carotid artery, umbilical artery and descending aorta of 15 term fetuses with birth weights appropriate for gestational age and 20 fetuses, ultrasonically suspected of intrauterine growth retardation (IUGR), was recorded by means of a technique combining real-time linear-array ultrasonography and 2-MHz pulsed Doppler ultrasound. The waveform of the maximum blood velocity was characterized by a pulsatility index (PI) indicating peripheral vascular resistance. In the normal fetuses, the mean PI was 1.89 (+/- 0.07 SEM) in the common carotid artery, 0.93 (+/- 0.04) in the umbilical artery and 2.19 (+/- 0.06) in the descending aorta. In the IUGR fetuses, the PI was higher than in the normal fetuses in the umbilical artery (1.19 +/- 0.04; p less than 0.05) and lower in the carotid artery (1.48 +/- 0.03; p less than 0.05). The changes of the PI were even more pronounced in 10 IUGR fetuses in whom cardiotocographic signs (late decelerations) of imminent asphyxia were present. The results indicate an increase in the peripheral vascular resistance in the placental circulation and the lower body, and a decrease in the cranial vascular resistance in the growth-retarded fetuses. Furthermore, these findings suggest that in chronic and acute fetal distress, there is a redistribution of the fetal circulation favoring the brain.

Blood Circulation↗
PubMed1989

Albumin transfusion in non-immune fetal hydrops: Doppler ultrasound evaluation of the acute effects on blood circulation in the fetal aorta and the umbilical arteries.

A case of non-immune fetal hydrops, diagnosed as mucopolysaccharidosis VII with hypoalbuminemia, was treated in utero with albumin transfusions via cordocentesis on five occasions. Blood samples were taken for analysis of full blood count and blood gases before and after the transfusions. Pulsed Doppler ultrasound examinations of the arterial waveform were performed in the umbilical arteries and the descending fetal aorta and analyzed for the pulsatility index (PI). The hemoglobin concentration and the hematocrit decreased from 111 +/- 5 g/l and 0.335 +/- 0.008 to 95 +/- 5 g/l and 0.282 +/- 0.023 (mean +/- SD), respectively, after the transfusions. The calculated blood volume increased more than the given volume, indicating an autotransfusion causing additional plasma volume expansion. The blood gases were not significantly changed by transfusion. The PI decreased both in the umbilical arteries (p less than 0.05) and the descending fetal aorta, indicating peripheral vasodilatation. A positive correlation was found between the umbilical artery PI and the hematocrit before and after the albumin transfusion (r = 0.59; p less than 0.05). This relation could be due to covariation with other factors, e.g. peripheral vasodilatation secondary to the increased blood volume and the puncture of the umbilical vein itself. No improvement of the hydrops was seen after the albumin transfusions. The fetus died in utero during spontaneous labor after 30 gestational weeks.

Albumins↗
PubMed1988

Long-term ailments due to anal sphincter rupture caused by delivery--a hidden problem.

Questionnaires concerning ailments were sent postpartum (mean two years) to 62 women with anal sphincter ruptures (ASR), who were compared with a matched control population. The frequency of anal sphincter rupture at the hospital during delivery in the period, 1978-82, was 0.7% (n = 63). Primiparity, instrumental deliveries, abnormal presentation, large babies and oxytocin stimulation were all risk factors. Of 59 women answering the questionnaire 37 (63%) stated that they had had ailments three months postpartum, mainly with pain and involuntary passage of flatus but also with dyspareunia and occasional incontinence of faeces. Long-term symptoms were noted by 28 (48%) of the women, mainly with involuntary passage of flatus but also perineal pain, dyspareunia and occasional incontinence of faeces. Long-term symptoms occurred in 7 (88%) of women with ASR also involving the anal mucosa, but only in 21 (39%) of those with ASR only. Three of the patients subsequently underwent reconstructive surgery, and three complained of psychological problems.

Adult↗
PubMed1987

Ultrasound measurement of fetal blood flow in predicting fetal outcome.

The efficacy of fetal blood flow assessment in predicting fetal outcome was evaluated in 159 pregnancies suspected of intrauterine growth retardation (IUGR). Blood flow in the fetal aorta and umbilical vein was measured with imaging and pulsed Doppler ultrasound. Volume blood flow values and variables describing the waveform of the maximum aortic blood velocity were checked for relations to subsequent fetal outcome. A new semi-quantitative velocity waveform variable, blood flow class (BFC), was designed and tested. The occurrence of IUGR, imminent fetal distress, a low Apgar score at 1 and 5 min, and a low pH in the umbilical artery and vein were adopted to characterize fetal outcome. Receiver operating characteristic curves were used to demonstrate the sensitivity and false positive rate, and the Cohen's Kappa index was used to compare the predictive capacity of the various blood flow variables. BFC, describing the blood velocity waveform with emphasis on its end-diastolic part, was found to be the most powerful marker of imminent fetal asphyxia (Kappa = 0.66) and of intrauterine growth retardation (Kappa = 0.48).

Blood Flow Velocity↗
PubMed1987

Fetal and uteroplacental haemodynamics during short-term atenolol treatment of hypertension in pregnancy.

Fetal circulation was studied by means of combined real-time and pulsed Doppler ultrasound in 14 women with pregnancy-associated hypertension before and during the first and third days of treatment with the beta 1-selective blocker, atenolol; in seven of the women the maternal uterine arcuate blood velocity waveform was also studied. Blood flow characteristics were normal both in the fetus and in the maternal arcuate artery, compared with those in uncomplicated pregnancies of corresponding gestational ages. Volume blood flow remained unchanged in the fetal descending aorta, and in the umbilical vein during atenolol treatment, whereas the pulsatility index increased in the fetal descending aorta and in the arcuate artery. This suggests that the peripheral vascular resistance, both on the maternal and fetal side of the placenta, increased during short-term antihypertensive treatment with atenolol.

Adult↗
PubMed1987

Fetal blood flow in diabetic pregnancy.

Forty pregnant diabetic women were examined with combined Doppler and real-time ultrasound. The volume blood flow in the fetal aorta and umbilical vein was higher and the pulsatility index (PI) in the aorta lower in the early third trimester, as compared with a reference group. Near term, the umbilical artery PI was higher in diabetic than in non-diabetic pregnancies, indicating a higher placental vascular resistance in the former group. The high umbilical artery PI occurred in fetuses who later developed distress in labor. Therefore, a high umbilical artery PI cannot be considered characteristic of diabetic pregnancy, although fetal distress might be more common in diabetic pregnancy. In addition, a high aortic volume flow was found in those fetuses who later develop distress in labor. This might be an expression of an early compensatory mechanism for increased placental vascular resistance. No specific flow variation was observed for any White class, or in association with hypertension or non-optimally regulated diabetes. The blood flow variables in growth-accelerated fetuses were comparable to those found in fetuses with normal weight. Since fetal distress might be more common in diabetic pregnancy, ultrasonic fetal blood flow measurements are recommended for antenatal fetal surveillance.

Adult↗
PubMed1987

Blood flow in the fetal descending aorta.

Doppler estimation of the blood flow in the descending aorta of the fetus and waveform analysis of the maximum aortic velocity provide valuable information on fetal circulation. When estimating fetal aortic flow, it is important to consider possible sources of error; even when recording the maximum aortic velocity for waveform analysis, to obtain reproducible results it is important to use a low high-pass filter, a well-defined angle of insonation, and a standardized site of measurement and to avoid periods of fetal breathing and activity. In normal pregnancy the time-averaged mean velocity in the descending aorta is stable throughout the third trimester. The weight-related flow is stable until 37 weeks, after which it falls slightly. The placental proportion of the flow in the thoracic descending aorta decreases toward term. In the aorta of normal fetuses there is positive flow throughout the whole heart cycle, which is due to the low vascular resistance in the placental circulation. The waveform of the aortic velocity can be characterized by the PI, which is stable during the last trimester of gestation. Caution is required when interpreting changes in the aortic PI, as it is not only affected by the peripheral resistance but also by the heart performance. Furthermore, PI is related to fetal heart rate. Near term different values of PI are found in different fetal behavioral states. In fetuses with retarded growth and in fetuses at distress, characteristic changes of the aortic velocity waveform have been reported by several researchers: the end-diastolic velocity diminishes and disappears, and in extreme cases a brief reversal of flow in diastole was observed. Consequently, the PI increases in such cases. The absence of the end-diastolic aortic velocity can easily be determined and is the best indicator of fetal status: in fetuses with absent end-diastolic velocity the incidence of perinatal mortality and morbidity is significantly higher than in fetuses with positive flow throughout the cycle. In pregnancies with hypertension or diabetes mellitus, normal aortic flow has been reported, as long as the fetuses were not growth retarded. In cases of severe Rh-isoimmunization, the mean aortic velocity correlates with fetal hematocrit. In hypoxic fetuses the mean velocity was reported to correlate with the degree of hypoxia, hypercarbia, and acidosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Aorta, Thoracic↗
PubMed1987

Fetal cardiac arrhythmias: Doppler assessment.

Pregnancies in which fetal cardiac arrhythmias are present are associated with an elevated perinatal and neonatal mortality. In this group various major and minor fetal malformations, including heart malformations, are more common. FECG and phonocardiogram give some information on the type of arrhythmia in favorable cases. Real-time imaging detects fetal heart malformations and late signs of heart failure. Fetal echocardiogram is of great aid for the classification of the arrhythmia and for the detection of heart malformations. By applying combined real-time linear array and pulsed Doppler technique in cases of fetal cardiac arrhythmia, important information on the fetal circulatory state can be obtained. Estimations of the volume blood flow guide the clinician in the practical handling of these cases. Volume blood-flow estimations can probably detect imminent fetal heart failure. Therapeutic effects can be followed, and the timing of delivery can be optimized taking the circulatory state into account. Within the fetal heart rate range 50 to 250 beats/min adequate blood circulation is usually maintained in the fetus. The peak velocity, the acceleration, and the rising slope are all increased in the postextrasystolic beat, indicating the existence of postextrasystolic potentiation in the fetal heart. These three parameters can be related to the ventricular filling time, supporting the opinion that the fetal heart follows the rules of the Frank Starling relationship. Fetal arrhythmias constitute also an experimental model for the study of fetal cardiac physiology.

Arrhythmias, Cardiac↗