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Biomedical subjects

T M Adamson

Publications and source records attributed to T M Adamson.

36 records · Page 2Linked to original sources
PubMed1983

Computerised nutritional data management in neonatal intensive care.

We report a minicomputer based recording, reporting, and research system for patient data management in the neonatal intensive care unit (NICU). It is moderately priced, transportable, and independent of a central computer. It requires only a desk top and standard power supply, and successfully meets the medical documentation, communication, and research needs of the NICU. The first phase of programme development has enabled us to process growth and nutritional data from infants on complex parenteral and enteral nutrition. The system is well suited to medical users and provides a practical interactive data management system with many potential applications in the NICU.

Australia↗
PubMed1981

Hospital referrals of home births in the intrapartum and postpartum periods.

Twenty home birth patients referred for hospital management were reviewed. Eleven mothers were referred in labour and nine infants in the first week after birth. The clinical presentation and neonatal outcome are described. The majority had antenatal factors suggesting increased perinatal risk. Careful patient selection, prompt detection and early referral of complications, and adequate facilities for infant resuscitation should minimise the risks of home birth. More research is required on the population requesting home birth and its outcome.

Adolescent↗
PubMed1981

A morphologic and morphometric analysis of fetal lung development in the sheep.

In the sheep, fetal lung development proceeds to a later stage of maturity than in smaller laboratory animals. Of the four stages in pulmonary development recognizable in this species - embryologic, pseudoglandular, canalicular, and aveolar - the latter three are described in the present study using histologic, morphometric, and ultrastructural techniques. During the pseudoglandular stage, the major airways developed centrifugally. Cartilaginous, glandular, muscular, vascular, and neural elements were present in major airway walls from an early age. During the canalicular stage, volume expansion of the lung was accomplished by rapid growth of large terminal spaces. In the final stage, alveoli were formed following subdivision of the large terminal spaces by alveolar crests. The alveolar lining epithelium differentiated during the latter two stages producing a large increase in alveolar surface area, particularly during the alveolar stage; a large increase in pulmonary capillary surface area also accompanied alveolar development. Thus, just prior to birth, the fetal sheep lung has a well-developed air-way system and alveolar network, in preparation for postnatal gas exchange.

Animals↗
PubMed1981

Development of patterns of respiratory activity in unanesthetized fetal sheep in utero.

Respiratory activity (diaphragmatic electromyogram) was recorded in six unanesthetized in utero fetal lambs, between 0.7 of gestation and term. Respiratory patterns generated by the fetus showed developmental changes that included 1) an emergence of a periodic modulation of respiratory rate producing alternating active and quite phases (mean cycle length of 37 min between 130 and 140 days' gestation; 2) an increase in percentage apnea (expiratory time greater than 10 s) from 20% at 110 days to 60% at 140 days; and 3) a linear decrease in the 2-h average respiratory rate, while mean rate during active phases showed no consistent gestational decline. Electrocortical and electroocular activity was monitored in three of six fetuses; however, discrete sleep state patterns could not be consistently identified. The results demonstrate a gestational change in the respiratory patterns of the developing fetus and suggest an orderly maturation of the mechanisms controlling respiratory neuronal output.

Anesthesia↗
PubMed1980

Morphological effects of chronic bilateral phrenectomy or vagotomy in the fetal lamb lung.

The relationship between fetal espiratory activity and fetal lung development has been studied at the cellular level using two experimental models. Chronic bilateral phrenectomy over a period of 20-28 days during the last trimester of the fetal lamb resulted in hypoplastic lungs, although cellular maturity, as indicated by the presence of alveolar epithelial Type II cells, was present. In the lungs from fetal lambs undergoing sham operations for a similar time course there was evidence of enhanced alveolar proliferation when compared with lungs from normal fetal sheep of a similar gastational age, most probably as a result of operative stress. Following chronic bilateral vagotomy no changes in size or histology of the fetal lamb lungs were detected. At an ultrastructural level, however, inclusions of Type II cells consistently showed the loss of the typical osmiophilic lamellated appearance. These results indicate the importance of the fetal breathing apparatus in maintaining a volume of lung liquid which is adequate for normal pulmonary development, particularly during the phase in which alveoli are formed.

Animals↗
PubMed1977

Morphological effects of chronic tracheal ligation and drainage in the fetal lamb lung.

The relationship between lung liquid flow and fetal lung development has been studied at the cellular level using ultrastructural techniques. Continuous in utero tracheal ligation and drainage (over a period of 21-28 days) both result in malformations of the developing fetal lamb lung. Ligated lungs are larger, and drained lungs are smaller, than normal lungs at a similar gestational age. These changes are not merely due to altered lung liquid volume, but actual tissue growth thas been affected. Future alveolar wall thinning is enhanced in ligated lungs and inhibited in drained lungs, whilst the presence of differentiated alveolar type II cells (probably related to surfactant production) is decreased in ligated lungs and markedly enhanced in drained lungs. These results indicate the importance of fetal lung liquid in the regulation of pulmonary development in the fetus.

Animals↗
PubMed1976

Carbonate dehydratase (carbonic anhydrase) and the fetal lung.

Carbonic anhydrase activity (carbonic dehydratase, EC 4.2.1.1) has been detected in the fetal lungs of stillborn human infants and rhesus monkeys, but a role for this enzyme in the fetal lung has not been elucidated. In utero the mammalian lung develops as a liquid-filled structure, the liquid being secreted by the lung. In the fetal lamb this liquid, when compared with plasma, has a high chloride and a low bicarbonate concentration, suggesting a possible role for carbonate dehydratase. Studies on 10 fetal lambs confirmed the presence of carbonate dehydratase in the lung. Levels at 60-66 days were negligible and rose to 0.30 Meldrum Roughton units/mg protein at about 140 days (term 147 days), with little change after birth. In another six fetal lambs at 135-136 days, inhibition of this enzyme with 100 mg acetazolamide suppressed the mean rate of secretion of lung liquid by 64.5% (P less than 0.005), which correlated with a significant drop in chloride concentration (P less than 0.001). This magnitude of changes in secretion after acetazolamide is of the same order as that occurring in the secretion of cerebrospinal fluid when carbonate dehydratase is inhibited. This observation supports the hypothesis that carbonate dehydratase in fetal lung affects the secretion of lung liquid, although its mechanism is as yet unknown.

Acetazolamide↗
PubMed1975

Lung liquid production and composition in the "in utero" foetal lamb.

Experiments were carried out on foetal lambs in utero from 103 to 133 days' gestation, to measure the daily flow and solute composition of liquid from the foetal lung. The mean daily flow from foetuses with a tracheal fistula was 231 ml/day (9.6 ml/h), while the mean hourly flow in foetuses with a tracheal loop was 5.1 ml/h. The pattern of flow of lung liquid was intermittent and irregular, with short periods of rapid flow interspersed with longer periods of slow and no flow. The Na+, Ca2+, Mg2+, Cl- and urea concentrations showed no significant change with increasing gestational age, but the K+ concentration showed a significant rise. It is concluded that the lung of the foetal lamb behaves as an exocrine gland, secreting a substantial volume of liquid of a relatively constant composition.

Animals↗
PubMed1975

Diaphragmatic activity and lung liquid flow in the unanesthetized fetal sheep.

For some time it has been suggested that breathing movements are made "in utero" and recently measurements of tracheal pressure and lung liquid flow in chronic fetal preparations have led to the hypothesis that rapid changes in these parameters are the result of respiratory muscle activity. To test this hypothesis diaphragmatic electrical activity was measured in seven chronic unanesthetized fetal sheep preparations and correlated with lung liquid flow and tracheal pressure. Diaphragmatic activity led to a fall of tracheal pressure and movement of a small volume of lung liquid into the lung. After the activity ceased, tracheal pressure returned to normal and flow diminished to zero or was directed out of the lung. The breathing pattern was unassociated with the net movement of lung liquid out of the lung. A histogram of the interval between breaths revealed a changing pattern of activity throughout gestation. The pattern was significantly altered after premature delivery of one animal with a respiratory problem. These observations provide evidence that respiratory muscles are active "in utero" and that the pattern of activity changes throughout gestation.

Animals↗
PubMed1975

Modification of respiratory center output in the unanesthetized fetal sheep "in utero".

Diaphragmatic electromyographic activity, tracheal and amniotic fluid pressures, lung liquid flow, and carotid and jugular venous pressures were measured on eight fetal lambs who survived for periods of 9-43 days postoperatively. The fetal gestational age ranged from 98 to 113 days at operation. Respiratory center output of the fetus as indicated by electromyographic activity was modified by the following stimuli. It was suppressed by anesthesia and fetal hypoxia (Pao2 = 12 mmHg), tonically reduced by lung inflation, and stimulated by cyanide injections (150-600 mug) into the fetal jugular vein. Neuromuscular transmission to the diaphragm was blocked with d-tubocurarine (0.2-0.6 mg). These experiments indicate that central and motor pathways to the diaphragm are sufficiently mature by 101 days in the fetal sheep to permit their output to be modified by chemical and mechanical stimuli.

Amniotic Fluid↗
PubMed1970

Effect of asphyxia due to umbilical cord occlusion in the foetal lamb on leakage of liquid from the circulation and on permeability of lung capillaries to albumin.

1. Experiments were performed on foetal lambs, exteriorized at Caesarean section, to determine the effects of asphyxia on the leakage of liquid from the circulation and on the permeability of lung capillaries to albumin. Following a period of control observation (30-120 min) the foetus was asphyxiated by occlusion of the umbilical cord for 5-10 min and then allowed to recover while observations were continued for a further 20-80 min.2. Measurements were made of the lymph flow from the lungs, that had drained via the thoracic duct; of protein concentration in lymph and plasma; of arterial blood haematocrit, pH, P(O2) and P(CO2); and of arterial and left atrial pressures and heart rate. Human serum albumin labelled with (125)I was infused intravenously during the control period and (125)I count rates were followed in plasma and lymph throughout the experiment. Values for the transfer coefficient of albumin (E/V min(-1), i.e. interstitial fluid clearance of albumin per unit of lung interstitial fluid volume) were determined during control, cord-occlusion and post-occlusion periods.3. During cord occlusion arterial and left atrial pressure, haematocrit and plasma protein concentration all rose, returning to the control value by 20 min after release of cord occlusion. The haematocrit values indicated that about 9% of the blood volume was temporarily lost from the circulation. Lung lymph flow also increased, reaching a maximum in the 5 min period after release of occlusion and returning to the control level 15 min later. Values for E/V of albumin were at no time significantly different from those during the control period.4. It was concluded that acute foetal asphyxia produced by umbilical cord occlusion caused an increased leakage of liquid from the circulation in general. This effect was temporary and was probably due to an increase in capillary pressure during cord occlusion. The asphyxia had no persistent effect on the permeability of lung capillaries to albumin.

Albumins↗
PubMed1969

Composition of alveolar liquid in the foetal lamb.

1. Experiments were performed on foetal lambs at gestations between 125 days and term. The foetus was exteriorized at Caesarean section with the umbilical cord and placental attachment maintained intact. Samples of liquid from the alveolar parts of the lung were withdrawn through a tracheal cannula and samples of lung lymph, plasma and amniotic liquid were also obtained. Measurements were made of total osmolality, concentrations of electrolytes and urea, pH and P(CO2). Titrations were carried out with N/10 HCl and N/10 NaOH. The water content of the liquids was estimated and concentrations expressed per kg H(2)O.2. In alveolar liquid [H(+)], [K(+)] and [Cl(-)] were higher and [Ca(2+)], [phosphates] and [HCO(3) (-)] were lower than in plasma or lymph. In amniotic liquid osmolality [Na(+)], [Cl(-)] and [Ca(2+)] were lower and [phosphates] higher than in plasma or lymph. Alveolar liquid/plasma ratios of [HCO(3) (-)], [Ca(2+)], [Cl(-)] and [K(+)] differed from ultra filtrate/plasma ratios of these ions.3. Titration curves demonstrated a very small amount of buffering in alveolar liquid at its in vivo pH of 6.27 mostly due to HCO(3) (-) at an average concentration of 2.8 mM/kg H(2)O.4. It is concluded that foetal alveolar liquid is not an ultrafiltrate of plasma nor a mixture of amniotic liquid and plasma ultrafiltrate, but a special material elaborated by the foetal lung.

Amniotic Fluid↗