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Biomedical subjects

K Campbell

Publications and source records attributed to K Campbell.

At least 181 records · Page 10Linked to original sources
PubMed1982

Patterns of gross fetal body movements over 24-hour observation intervals during the last 10 weeks of pregnancy.

Continuous measurements of gross fetal body movements were made with an ultrasonic real-time scanner for periods of 24 hours in 31 women. Fetuses made 0 to 130 gross fetal body movements per hour which accounted for 0% to 50% of the time. At 38 to 39 weeks' gestational age, fetuses demonstrated a peak in activity between 2100 and 0100 hours. The longest period of complete absence of gross fetal body movements was 75 minutes. Maternal meals and glucose concentrations did not influence gross fetal body movements.

Activity Cycles↗
PubMed1981

Effects of synthetic glucocorticoid administration on human fetal breathing movements at 34 to 35 weeks' gestational age.

Fetal breathing movements were measured in six women who had received exogenous glucocorticoids throughout pregnancy and in whom the endogenous circadian rhythm in cortisol was absent or had been suppressed. Studies were performed for 24-hour observation periods while women received prednisone and then one week later on the same women after equivalent doses of dexamethasone. Fetal breathing movements occurred 29.9% +/- 1.9% of the time in the prednisone-treated group and this was not changed in the same fetuses after dexamethasone treatment. There was a significant increase in the percentage of time spent making breathing movements during the second and third hours following breakfast, lunch, and dinner (P less than 0.001). A fourth peak in fetal breathing activity occurred in the late evening and seemed to be related to the time of the evening glucocorticoid medication. These data were compatible with the hypothesis that maternal glucocorticoid concentrations may influence patterns of fetal breathing movements at 34 to 35 weeks' gestational age.

Blood Glucose↗
PubMed1981

Effects of external physical stimulation on fetuses near term.

Measurements were made in 17 healthy pregnant women between 36 and 42 weeks' gestational age 90 minutes before and after a standard physical stimulus. The mean fetal heart rate was 138 +/- 0.4 bpm; the median value of the 5-minute standard deviation of successive heartbeat intervals was 30.3 msec, and the percentage of time spent making gross fetal body movements was 11.1% +/- 0.4%. These measurements did not change following stimulation of fetuses. Fetal breathing movements diminished over the 180-minute observation period but did not appear to be changed by fetal stimulation. During studies, periodic increases separated by periodic decreases in fetal heart rate, fetal heart rate variability, gross fetal body movements, and fetal breathing movements were measured, and these changes did not seem to be related to external stimulation of fetuses. Periodic changes in these measurements may have been related to underlying patterns of fetal behavior but were not usually influenced by external physical stimulation of fetuses.

Female↗
PubMed1980

A definition of human fetal apnea and the distribution of fetal apneic intervals during the last ten weeks of pregnancy.

Fetal breathing movements were studied over 24-hour observation periods for a total of 744 hours in 31 healthy pregnant women at 30 to 39 weeks' gestational age. An analysis of 165,786 breath-to-breath intervals in eight fetuses demonstrated that 97% of breath-to-breath intervals were less than 6 seconds in duration. It was concluded that a breath-to-breath interval of 6 seconds or more is a rational definition of fetal apnea during the last 10 weeks of pregnancy. An analysis of intervals during which time no fetal breathing activity occurred in the 31 fetuses demonstrated that prolonged episodes of apnea were distributed in a similar fashion at different gestational ages. The longest periods of apnea were 65 minutes at 30 to 31 weeks, 105 minutes at 34 to 35 weeks, and 120 minutes at 38 to 39 weeks. No periods of apnea of more than 45 minutes were measured during the second and third hours following maternal meals. A useful strategy for recognition of significant fetal apnea would be to make observations during the second and third hours following maternal meals when apneic lengths greater than 45 minutes were not observed in this highly selected group of normal fetuses.

Apnea↗
PubMed1980

Circadian rhythms in maternal plasma cortisol and estriol concentrations at 30 to 31, 34 to 35, and 38 to 39 weeks' gestational age.

In order to examine the relationship between circadian rhythms in different steroids, cortisol and estriol were measured by radioimmunoassay in maternal venous plasma taken at 30- to 60-minute intervals over 24 hours from nine healthy women at 30 to 31, 11 at 34 to 35, and 10 at 38 to 39 weeks' gestation. Maternal cortisol was maximal at 0730 to 0830 hours and fell significantly to its lowest concentration between 1830 and 0130 hours. At 30 to 31 and 34 to 35 weeks there was a significant circadian rhythm in estriol concentrations which was inversely related to the circadian rhythm in cortisol. At 38 to 39 weeks mean estriol concentrations were significantly higher than those at 30 to 31 and 34 to 35 weeks but there was no significant circadian pattern. We concluded that there is an inverse relationship between maternal cortisol and estriol at 30 to 31 and 34 to 35 weeks, which would be consistent with a maternal effect on fetal adrenal function. The increase in mean concentration and absence of circadian rhythm in maternal plasma estriol at term might suggest an additional positive stimulus to fetal adrenal function. The existence of patterns in maternal estriol concentrations must be taken into account in the u;se of sequential measurements of this hormone during the last 10 weeks of pregnancy.

Circadian Rhythm↗
PubMed1980

Human and automatic validation of a phase-locked loop spindle detection system.

A further test of a phase-locked loop spindle detector is described. On the basis of comparison with both human visual scoring and with a second automatic system employing complex demodulation techniques, the detector's performance would appear to be adequate for most laboratories' needs. The errors in detection were largely shared by the two automatic systems.

Adult↗
PubMed1980

Time series analysis of human foetal breathing activity at 30-39 weeks gestation.

Thirty-one healthy human fetuses were each observed with a real-time scanner continuously for 24 h. The percentage of time spent breathing was computed for each 5 min observation period during the 24 h which produced a time series of 288 observations for each fetus. Box-Jenkins modelling techniques and analysis of frequency spectrum distribution were used to quantify mathematically the human fetal breathing data. The data was described mathematically by a first-order auto-regression z(t)=0.7 z(t-1) + epsilon(t) which confirmed and quantified the episodic nature of foetal breathing activity. Evaluation of the spectral distribution of the fetal breathing movements identified a significant band of pseudo-periodic components with repeat periods ranging from 100 to 500 min (P less than 0.001). Results of this study indicated that the occurrence of fetal breathing movements were non-random and that Box-Jenkins modelling results and spectral power distribution may be useful in identification and description of any fetal breathing patterns which differ from normal patterns.

Female↗
PubMed1980

A comparison of the effects of high frequency--low tidal volume and low frequency--high tidal volume mechanical ventilation.

Ten neonates with severe lung disease were studied while mechanically ventilated with standard volume preset infant ventilators, using two different ventilatory patterns. Slow ventilatory rates and high tidal volumes were alternated with rapid rates and low tidal volumes; minute ventilation, FIo2, PEEP, and I:E ratios were held constant. Peak inspiratory pressure, mean airway pressure, expiratory time, Pao2, Paco2, pH, and arterial blood pressure were measured and compared for each frequency-tidal volume combination. The best arterial oxygenation occurred at the combination of settings that produced the highest mean airway pressure and always during low frequency-high tidal volume ventilation (P less than 0.001). Changes in oxygenation appeared to be directly related to changes in MAP. A second experiment examined two different ventilator systems' responses to changes in ventilatory rate. When the rate of one ventilator (Bourns LS104 volume preset) was increased, MAP increased. When the rate of the other ventilator (Bennett PR2 pressure preset) increased, MAP decreased. These observations suggest that there is a direct relationship between MAP and orterial oxygenation, and that the supposed advantages of one ventilatory pattern over the other may be secondary to inadvertent changes in subtle pressure-time relationships within the respiratory cycle and incidental changes in MAP. These changes may vary from one ventilator to another.

Humans↗
PubMed1980

Diurnal changes in maternal plasma oestrone and oestradiol at 30 to 31, 34 to 35 and 38 to 39 weeks gestational age.

Diurnal changes in the concentrations of oestrone (E1) and oestradiol (E2) in maternal peripheral plasma have been measured in samples of blood taken at one hour intervals from women at 30 to 31, 34 to 35 and 38 to 39 weeks of pregnancy. There was a significant effect of time of sampling on the plasma concentration of E1 at all stages of gestation, and circadian changes in the levels of E1 were apparent at 34 to 35 and 38 to 39 weeks. Peak values were measured around 0830 to 0930 hours, and troughs occurred between 0130 and 0530 hours. Significant effects of time of sampling on the plasma concentration of E2 were found at 34 to 35 and 38 to 39 weeks of pregnancy; night-time concentrations were lower than the peak values at 0730 to 0830 hours. The relation of these changes to the circadian rhythms in the concentrations of cortisol and oestriol in maternal plasma are discussed.

Circadian Rhythm↗
PubMed1980

Patterns of human fetal breathing during the last 10 weeks of pregnancy.

Continuous measurements of human fetal breathing movements and gross fetal body movements were made with an ultrasonic real-time scanner for periods of 24 houro 31 weeks' gestation, a significant increase in fetal breathing movements occurred during the second and third hours after meals; this pattern apparently followed an increase in maternal plasma glucose concentrations. At 38 to 39 weeks' gestation, fetal breathing movements increased during the second and third hours after breakfast, but the troughs seen before lunch and supper at 30 to 31 weeks' gestation were not present. Fetal breathing movements diminished over the day and reached a minimum between 1900 and 2400 hours. Fetal breathing activity increased in both groups between 0400 and 0700 hours while mothers were asleep; this was not related to an increase in maternal glucose concentrations. Absence of fetal breathing movements was observed for up to 122 minutes in this analysis of 480 hours in 20 patients. These data show that much more information must be obtained on factors that normally influence fetal breathing activity. Only then can research strategies be suggested for clinical evaluation of the usefulness of fetal breathing movements in the assessment of fetal health.

Blood Glucose↗