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Biomedical subjects

D J Henderson-Smart

Publications and source records attributed to D J Henderson-Smart.

At least 109 records · Page 6Linked to original sources
PubMed1985

Relation between apnoea duration and type and neurological status of preterm infants.

The incidence, duration, and type of apnoea were determined in 28 preterm infants born at 27 to 34 weeks' gestation, using polygraphic records of abdominal breathing movements and nasal airflow. Of the 1520 episodes of apnoea of 10 or more seconds duration, 1002 (66%) lasted 10 to 14 seconds, 311 (20%) lasted 15 to 20 seconds, and 207 (14%) lasted more than 20 seconds. Overall, 69% were central in type, 20% were mixed, and 11% were purely obstructive. With increasing duration of apnoea, the proportion of episodes of central apnoea decreased (69 to 29%) while that of mixed apnoea increased (20 to 60%). Eight infants had obstructive apnoea of more than 20 seconds duration. When they were compared with the 10 infants of similar gestational age and birthweight who had central or mixed apnoea, they had a higher incidence of intraventricular haemorrhage, hydrocephalus, positive pressure ventilation via an endotracheal tube, and abnormal neurological development during the first year of life.

Airway Obstruction↗
PubMed1985

Clonidine hydrochloride--a safe and effective antihypertensive agent in pregnancy.

A prospective, double-blind, randomized controlled trial was carried out, comparing alpha-methyldopa and clonidine hydrochloride in 100 pregnant women with hypertension. There was no difference in hypotensive effect or reported maternal side effects with either agent. There was one neonatal loss in each group (98% survival). Neither drug caused clinically significant hypotension nor rebound hypertension in the neonates. Clonidine hydrochloride, like methyldopa, appears to be a safe antihypertensive agent in pregnancy.

Adult↗
PubMed1984

The effect of intra-amniotic injection of triiodothyronine on pulmonary maturity in lambs at 130 days gestation.

Saline or triiodothyronine (T3) (50-1000 micrograms) was injected into the amniotic sac of 17 pregnant ewes under general anesthesia at 130 days gestation. Forty-eight h later, the lambs were delivered by hysterotomy. Cord plasma T3 and cortisol and amniotic fluid T3 were assayed, and the maturity of the fetal lung was assessed in terms of its pressure-volume response and its surfactant (lamellar body phospholipid) content. With the highest dose of T3, cord plasma T3 and cortisol were raised, and lung maturity was enhanced compared with saline-treated controls; the pressure-volume curve showed increased hysteresis on inflation and deflation, and the lung retained air on return to zero pressure. There was also an apparent, but not statistically significant, increase in the lamellar body phospholipid content of the lung. Irrespective of treatment, lungs which were more mature, in terms of their pressure-volume characteristics, tended to contain a higher proportion of lamellar body phospholipid relative to total phospholipid.

Amnion↗
PubMed1983

Clinical apnea and brain-stem neural function in preterm infants.

We assessed the relation between clinical apnea and brain-stem neuronal function in 58 preterm babies. The brain-stem conduction time of the auditory evoked response (Wave V-I interval) was longer in babies with apnea than in those without it at a similar postconceptional age (at 32 to 33 weeks: mean, 6.16 vs. 5.35 msec, P less than 0.001; at 34 to 35 weeks: mean, 5.98 vs. 5.33 msec, P less than 0.002). The number of apneas per day decreased over a period that was similar to the period during which brainstem conduction time decreased. In general, apneas ceased when the conduction time decreased to the levels observed in babies of a similar age who did not have apnea. Short brain-stem conduction times were observed in some infants who had prenatal stress, such as intrauterine growth retardation or maternal hypertension. These results suggest that the occurrence of apnea in preterm infants is correlated with neural function in the brain stem.

Apnea↗
PubMed1982

Asynchronous respiratory activity of the diaphragm during spontaneous breathing in the lamb.

1. Direct simultaneous recordings from chronically implanted electrodes in different parts of the diaphragm were made in young lambs in which laryngeal adductor (thyroarytenoideus) and intercostal electromyograms, airflow, tracheal pressure and electrocorticogram and electro-oculograms for behavioural state were also recorded.2. An asynchrony of diaphragmatic contraction occurred which was dependent on sleep state. The vertebral portion showed maximal post-inspiratory activity while the lateral paratendinous portion usually terminated abruptly with end-inspiration, reciprocating closely with the onset of expiratory laryngeal adductor activity during quiet sleep. The contraction of the sternal portion was similar to the vertebral portion. In active (rapid eye movement) sleep there was no expiratory laryngeal constriction and post-inspiratory activity occurred in all portions of the diaphragm. During the characteristic bursts of rapid breathing in active sleep all post-inspiratory activity disappeared and the diaphragm contracted synchronously.3. General anaesthesia (Halothane/N(2)O or Nembutal) abolished expiratory laryngeal adductor activity and the discharge pattern became similar in all parts of the diaphragm.4. Intrathoracic vagotomy of Xylocaine blockade below the recurrent laryngeal nerves abolished post-inspiratory activity in all parts of the diaphragm, in contrast to the effect on expiratory laryngeal adductor activity which increased.5. Sustained ;tonic' electromyographic activity was often recorded from the costal and to a lesser extent the paratendinous portion of the diaphragm. This activity related to adjacent intercostal activity:ipsilateral intercostal blockade with local anaesthetic (Xylocaine 1%) abolished both the intercostal and the ;tonic' activity of the costal margins of the diaphragm. Conversely ipsilateral phrenic nerve blockade abolished all but the ;tonic' activity which related to intercostal activity.6. Interpretation of the respiratory activity of the diaphragm could not be made adequately from conventionally placed electrodes (i.e. costal, sternal slip or surface) during spontaneous breathing in unanaesthetized lambs. Simultaneous recordings showed that while expiratory flow and duration were actively controlled by expiratory laryngeal adductor activity and the diaphragm, the latter performed asynchronously. While both laryngeal and diaphragmatic expiratory functions were substantially under vagal control, the former increased and the latter decreased with reduced vagal input.

Anesthesia, General↗
PubMed1981

Fetal lung maturation assessment after administration of glucocorticoid.

The concentration of lamellar body (or surfactant) phospholipid in amniotic fluid generally increases as gestation proceeds and the fetal lungs mature. However, when glucocorticoid is administered prior to 35 weeks' gestation to accelerate fetal lung maturation, the ensuing increase in lamellar body phospholipid, to levels indicative of lung maturity, may be followed by a decrease to levels which suggest a reversion to lung immaturity. Estimations of fetal lung maturity should be interpreted with caution following the administration of glucocorticoid.

Amniotic Fluid↗
PubMed1981

Oxygen and carbon dioxide tensions, breathing and heart rate in normal infants during the first six months of life.

Daytime measurements were made of the relationship between sleep state, cardio-respiratory changes and oxygen (transcutaneous PO2) and carbon dioxide (mass spectrometer alveolar PCO2) tensions in eleven normal infants from birth to 6 months of age. Sequential records were made at 1 week, 1, 3 and 6 months. The babies were not restrained, slept in a cot, and were constantly observed. Heart rate was higher in active sleep than in quiet sleep at all ages and rose between 1 week and 1 month (P less than 0.01) in both quiet sleep and active sleep and then decreased at 3 and 6 months. Respiratory rate only changes with age in active sleep at 6 months, showing a decrease (P less than 0.05) but was higher in active sleep that in quiet sleep at 1 month (P less than 0.002) and 3 months (P less than 0.02). A fall in heart rate (less than 100 beats/min) occurred chiefly in association with apnoea. The incidence of apnoea (of greater than 3 s duration) varied widely between babies at the same age and in the same baby at different ages but was most common in the first 3 months of life. No evidence of obstructive apnoea was found and no apnoea of greater than 12 s duration was observed. Period breathing occurred in all babies at 1 month normally following sighs but was uncommon at 1 week and 3 months and absent at 6 months. A fall in transcutaneous PO2 did not precede but often resulted from an episode of periodic breathing.

Aging↗
PubMed1981

Measurement of "lamellar body phospholipid" in amniotic fluid as a method for assessing fetal lung maturity.

A simple, rapid micro-method, suitable for use in a routine clinical laboratory, is described for isolating a surfactant fraction from 0.1 mL of human amniotic fluid and measuring its phospholipid content. We determined the phospholipid content of this fraction, referred to as "lamellar body phospholipid," in 451 samples of amniotic fluid collected within two days of delivery and related the data to the respiratory performance of the newborn in every case; 112 of the infants were delivered at 28-37 weeks gestation. The incidence of hyaline membrane disease was inversely related to the concentration of lamellar body phospholipid in the amniotic fluid. Eleven of 12 infants with lamellar body phospholipid values less than 25 mg/L and four of 44 infants with lamellar phospholipid values between 25 and 50 mg/L developed hyaline membrane disease or other serious respiratory problems possibly related to lung immaturity, whereas all of 395 infants with lamellar body phospholipid values of 50 mg/L or more were free from respiratory problems of this nature. The incidence of transient tachypnea was greatest when the lamellar body phospholipid value was between 25 and 50 mg/L, suggesting that this condition may be related to a degree of lung maturity.

Amniotic Fluid↗
PubMed1980

Incidence of the respiratory distress syndrome in infants of diabetic mothers--perinatal influences.

This survey of 73 infants of insulin dependent (ID) diabetic mothers and 70 infants of gestational diabetics (GD) born at King George V Memorial Hospital between January, 1968 and December, 1975, showed that all 12 babies with RDS were from the ID group. RDS was the cause of all 6 neonatal deaths and together with the 5 stillbirths gave this high risk group a 15% mortality rate. Since no deaths occurred in the GD group, the overall mortality was 8%. In the 6 years, 1970-1975, RDS occurred 21 times more often in babies of ID mothers than in control babies born to non-diabetics. Babies born to ID mothers were of significantly lower mean gestational age than those born to the GD mothers. Within the ID group, those babies with RDS were of significantly lower gestation than those without and the mean gestation was similar to control babies with RDS. Provided the diabetes is controlled and fetal welfare ensured, later delivery, following documentation of lung maturity, may lower the incidence of RDS and therefore perinatal mortality and morbidity.

Diabetes Complications↗
PubMed1979

Reduced lung volume during behavioral active sleep in the newborn.

In a previous study of newborn infants we observed overall rib cage collapse during active sleep and postulated that the lungs also could be deflated, leading to reduced oxygen stores and circumstances favoring the rapid development of hypoxemia during apnea. In this study, thoracic gas volume (TGV) has been measured directly by occlusion plethysmography in six normal babies during behavioral quiet and active sleep and related to the different movements of the rib cage and abdomen-diaphragm that occur during each sleep state. TGV was significantly reduced in each baby during active sleep and was associated with rib cage deflation and increased abdomen-diaphragm excursions. The average reduction of TGV was 31% when compared with the volume in quiet sleep and did not depend on the order in which the sleep states were tested. The reduced lung volume in active sleep could have implications for the regulation of breathing in that state. A reduction of lung oxygen stores in active sleep suggests an age-related vulnerability of the young infant to hypoxemia.

Diaphragm↗
PubMed1979

Ventilatory responses to hypoxaemia during sleep in the newborn.

Ventilatory responses to rapidly developing hypoxaemia during N2-rebreathing were compared for active and quite sleep in three newborn lambs and four puppies. In lambs, active sleep was associated with: (i) development of ribcage deflation during inspiration, which persisted during progressive hypoxaemia; (ii) depressed ventilatory response to hypoxaemia despite increments of respiratory rate; (iii) delayed arousal. In the puppies, inspiratory collapse of the ribcage did not occur in active sleep and the ventilatory responses during hypoxaemia were similar to those in quite sleep. While apparently defective when related to adults, these responses to hypoxaemia in the lamb are normal. This study illustrates the importance of considering behavioural state and species differences when studying the regulation of breathing, particularly during development.

Animals↗