PubMed Health⌕ Search

Biomedical subjects

F Giffin

Publications and source records attributed to F Giffin.

At least 19 recordsLinked to original sources
PubMed1997

Prospective study of lung volumes in young asthmatic children.

In a 9-y prospective study, the occurrence and duration of lung volume abnormalities in 21 young asthmatic children (median age at recruitment 4 y, range 3-8 y) was determined. The median functional residual capacity (FRC) at recruitment was 135% of that predicted for height (range 79-187%) and 13 children were hyperinflated. The median FRC decreased significantly after 3 y of follow-up and by 9 y only one child remained hyperinflated. We conclude that persistent elevation of lung volume in young asthmatic children appears to be uncommon.

Age Distribution↗
PubMed1996

Temporary impairment of lung function in infants with anterior abdominal wall defects who have undergone surgery.

Compliance of the respiratory system (CRS) was measured before and after surgical intervention in 14 infants who had anterior abdominal wall defects (AWD) (7 exomphalos, 7 gastroschisis). The median gestational age was 37 weeks (range, 34 to 40) and median birth weight was 2.38 kg (range, 1.94 to 3.45). The infants had stiff lungs before surgery (median CRS, 0.58 mL/cm H2(O)/kg). During the first and second postoperative days, the median CRS decreased to 0.33 mL/cm H2(O)/kg (P < .05). In seven cases, measurements also were obtained on the third and fourth postoperative days, which showed an increase in the median CRS (day 3, 0.47 mL/cm H2(O)/kg; P < .05). These findings show that in infants with AWD, primary surgical closure is associated with deterioration of lung function, but this effect is temporary.

Abdominal Muscles↗
PubMed1996

The Hering-Breuer reflex in ventilated children.

The authors tested the hypothesis that, in the paediatric population, the Hering-Breuer reflex would be provoked by the positive pressure inflation of mechanical ventilation (IPPV), and that the strength of the reflex would relate to the child's age and compliance of the respiratory system (CRS). During IPPV, changes in air flow, volume and airway pressure were recorded simultaneously. From the traces, expiratory times and CRS were calculated. The mean expiratory time (Te1) prior to each inflation and the mean expiratory time (Te2) immediately following an inflation were determined. The presence of the reflex was indicated by Te2 being longer than Te1, and the strength of the reflex was calculated as the difference between Te2 and Te1 expressed as a percentage of Te1. Twenty children were studied who had a mean age of 0.7 years (range 0.1-9.8 years). The reflex was provoked in 19 of the 20 patients and was not seen in the oldest patient. The strength of the reflex varied from 22 to 144% and was inversely related to postnatal age significantly (r = -0.73) but not CRS or inflation volume. It is concluded that the Hering-Breuer reflex is provoked during IPPV in young children; whether, as in neonates, this influences the efficacy of ventilation deserves investigation.

Aging↗
PubMed1996

Urinary excretion of adrenocortical steroid metabolites by pre-term human infants: trends from birth until 3 months post term.

We report trends in urinary steroid excretion in serial 24 hour collections made using a novel method based on "Supersorb" type disposable nappies. Using capillary column gas chromatography, we quantified nine cortisol metabolites (FM) and 11 steroid sulphates (SM) in 6 infants born at 29-31 weeks gestation on 9 occasions until 24 weeks post delivery. In all infants, SM excretion increased progressively until 33-39 weeks (mean 36.8) post conception to maxima of (all values mg/24 h) 2.6-11.7 and then declined to 5-15% of peak values at the end of the study period in 4 infants born after a period of labour but to only 54 and 71% in 2 infants born without labour. FM levels showed a wide range which was not correlated with body weight, eg: on week 1, 0.06-0.20 and on week 24, 0.15-0.72. progression over this period was essentially linear. The ratio (mean (SD)) of 11-oxo/11-hydroxy metabolites decreased from 10.0 (8.2) to 2.3 (0.4) in the same period, p = < 0.10, while that of 20-oxo/20-hydroxy metabolites increased from 0.18 (0.07) to 1.08 (0.42), p = < 0.04. The ratio of metabolites with 5 oxygen functions relative to 6 increased from 0.38 (0.16) to 1.36 (0.43), p = < 0.04. Excretion of 5 alpha-tetrahydrocortisol began to rise at 44-47 wk post conception, but, unexpectedly, that of the 5 beta epimer began to rise sooner, at 39-41 wk, reaching a peak at 44-51 wk and then declining. The ratio of 5 beta/5 alpha epimers was 11.71 (11.1) at the peak and 1.14 (0.87) at 24 weeks, p = < 0.07. We conclude that, using a collection method which is reliable, non-stressful and repeatable at frequent intervals, new information on the evolution of steroid secretion and metabolism postpartum is emerging.

Adrenal Cortex Hormones↗
PubMed1996

Tidal breathing parameters in the first week of life and subsequent cough and wheeze.

BACKGROUND: Assessment of tidal breathing parameters may be a useful method of predicting respiratory problems in early childhood. Low values of TPTEF/TE (the ratio of the proportion of time to reach peak tidal expiratory flow to total expiratory time) outside the neonatal period have been significantly related to respiratory tract illness with wheezing in boys in the first year of life. METHODS: TPTEF/TE measurements in the perinatal period were evaluated in nonsedated infants and the predictive value of this early measurement for subsequent respiratory morbidity during infancy was assessed. Flow during tidal breathing was measured while the infant slept quietly in a plethysmograph using a Fleisch pneumotachograph inserted into an infant face mask. Recruitment continued until traces from 60 infants with 10 consecutive flow curves without artefacts were obtained. In addition, plethysmographic measurements of airway resistance (Raw) and thoracic gas volume (TGV) were measured and specific conductance (sGaw) calculated. Parents recorded their infant's cough and wheeze during the first 12 months of life. RESULTS: Sixty five measurements were made in 60 infants with a mean age of two days and gestational age of 40 weeks. Two observers separately calculated TPTEF/TE ratios on 25 traces randomly selected from the pool of 60. The mean difference between the two observers was -0.004 (limits of agreement 0.048 to -0.056). Thirteen infants became symptomatic (wheeze, with or without cough); their median TPTEF/TE ratio (0.349) was significantly lower than the rest of the cohort (median 0.412) and they also had significantly higher Raw and lower sGaw. The positive predictive value of a low TPTEF/TE ratio, however, was only 41%. CONCLUSIONS: These results suggest that the use of this test in the prediction of future respiratory disease in an individual is limited.

Cohort Studies↗
PubMed1995

Does a family history of atopy influence lung function at follow-up of infants born prematurely?

The aim of this study was to assess whether a family history of atopy influenced lung function at follow-up of infants born prematurely. Analysis was made of thoracic gas volume and airways resistance measurements performed at 1 year of age in 86 infants born at a median gestational age of 29 weeks. These measurements had been made during a prospective follow-up study. The 30 infants with a family history of atopy were found to have a higher airways resistance (median 35 cmH2O/l/s) than the 56 infants without such a family history (median 30 cmH2O/l/s) (p < 0.05). However, when the results from 18 infants with a family history of atopy were compared with 18 controls who were matched for requirement for neonatal ventilation, parental smoking and were within at least 1 week of gestational age, no significant difference in airways resistance was found between the two groups. Multiple regression analysis demonstrated that gestational age and birth weight explained the apparent relationship between a family history of atopy and an elevated airways resistance at follow-up.

Adult↗
PubMed1995

Chest radiograph appearance at 24 h of age--prediction of chronic oxygen dependency.

Chronic oxygen dependence is associated with immaturity, male sex and low birthweight, but amongst that high risk group further criteria are necessary to predict those most at risk. We previously developed a chest radiograph scoring system which, when used at 1 month of age, proved useful in predicting chronic oxygen dependency at 36 weeks post-conceptional age (PCA). We have now assessed whether the scoring system, if applied at 24 h of age, added predictive value to readily available demographic and ventilatory data. 50 infants, birthweight less than 1200 g and ventilated from birth, were examined. They had a median gestational age of 27 weeks (range 23-34), birthweight of 886 g (range 470-1172) and chest radiograph score of 7 (range 2-13). Univariate analysis revealed that oxygen dependency at 28 days and 36 weeks PCA was significantly associated with low gestational age, male sex and high ventilatory requirements, in addition to a high chest radiograph score. Stepwise regression analysis, however, demonstrated that a high chest radiograph score predicted oxygen dependence at 28 days, independent of immaturity, low birthweight, male sex and high ventilatory requirements. A chest radiograph score of more than 5 rendered an infant four times more likely to be oxygen dependent at 28 days than those with lower scores. We conclude the chest radiograph appearance at 24 h of age could be used as a criterion to institute interventional strategies aimed at reducing chronic oxygen dependence.

Chronic Disease↗
PubMed1994

Disease severity and optimum mean airway pressure level on transfer to high frequency oscillation.

The aim of this study was to assess whether the severity of the infant's lung disease determined the most appropriate change in mean airway pressure (MAP) level to use on transfer from conventional ventilation to high frequency oscillation (HFO). In addition, we wished to assess whether the oscillatory frequency employed affected gas exchange. Ten premature infants with respiratory distress syndrome (RDS) were studied at a mean postnatal age of 1.5 days. During HFO, the infants were studied at a MAP equivalent of that used during conventional ventilation (baseline MAP), then at 2 and 5 cmH2O above baseline at 10 Hz. At the MAP identified as optimum, that is, the one associated with the best oxygenation, the infants were then studied at 10, 15 and 20 Hz. Each oscillatory setting was maintained for 20 minutes after which time arterial blood gases were measured. Prior to transfer to the oscillator, the peak inspiratory pressure was recorded, the P(A-a)O2 calculated and compliance of the respiratory system (Crs) measured. In nine infants, the optimum baseline MAP was +5 cmH2O. Oxygenation at that level was better than on conventional ventilation (P < 0.05), but there was no significant change in CO2 elimination. The optimum MAP was related to the peak pressure during conventional ventilation (P < 0.01) and inversely related to Crs (P < 0.01). There was no significant relationship with the P(A-a)O2. At the optimum MAP, the only significant effect of frequency was an impairment of oxygenation at 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

High-Frequency Ventilation↗
PubMed1994

Relationship between lung function results in the first year of life and respiratory morbidity in early childhood in patients born prematurely.

The relationship between lung function results at 6 months and 1 year of age to respiratory symptoms in the first 3 years of life in prematurely born population has been determined. In 88 infants (median gestational age, 29 weeks) thoracic gas volume (TGV) and airway resistance (R(aw)) was measured and specific conductance (SGaw) calculated at 6 months and 1 year of age. During 3 years of prospective follow-up neither TGV measured at either 6 months or 1 year, nor R(aw) and SGaw at 6 months, differed significantly between infants who were asymptomatic or symptomatic. At 1 year, however, R(aw) and SGaw were significantly higher and lower respectively in patients who were symptomatic than in those who were asymptomatic in any of the 3 years. An elevated R(aw) (> or = 50 cmH2O/L/s) measured at 1 year, but not at 6 months, was associated with a significant relative risk of symptoms in the first, second, and third year of life. We conclude that in prematurely born patients an abnormal airway resistance at 1 year predicts symptoms in early childhood.

Age Factors↗
PubMed1994

Effect of positive end expiratory pressure and mean airway pressure on respiratory compliance and gas exchange in children with liver disease.

The effect of positive end expiratory pressure (PEEP) and mean airway pressure (MAP) on respiratory compliance and gas exchange was assessed in children with liver disease. In the first study of 12 patients, PEEP was decreased either by 3 cmH2O below the baseline level (the child's original level) or to 0 cmH2O and then increased to 3 cmH2O above the baseline. Decreasing PEEP impaired compliance (P < 0.01), and oxygenation (P < 0.05), whereas increasing PEEP improved compliance (P < 0.05) and oxygenation (P < 0.05). Neither increasing nor decreasing PEEP caused significant changes in the carbon dioxide levels. In the second study, 24 children were studied at their baseline settings and then after increasing the PEEP by 3 cm H2O while simultaneously lowering the peak inspiratory pressure (PIP) to maintain MAP constant (12 children had lung function measurements). In the group overall increasing PEEP while decreasing PIP resulted in an insignificant change in paO2, but a significant increase paCO2 (P < 0.01) and reduction in tidal volume (P < 0.01), the change in compliance was not significant. After a second period at the baseline settings, in 12 children inspiratory time (TI) was increased while keeping MAP constant by reducing PIP. No significant change in paO2 or compliance was experienced, but paCO2 increased (P < 0.05) and tidal volume decreased (P < 0.01). In the other 12 children MAP was increased by prolonging TI. Increasing MAP had a variable effect and the changes in paO2 and paCO2 were not significant. No critical MAP level with regard to oxygenation was demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Does the duration of oxygen dependence after birth influence subsequent respiratory morbidity?

The relationship of respiratory morbidity at follow up to the development and type of "neonatal" chronic lung disease has been assessed. Three groups, each of ten infants matched for gestational age and gender, were compared. Group A had Type I chronic lung disease and group B bronchopulmonary (BPD), the most severe form of neonatal chronic lung disease (Type II CLD); group C had developed neither Type I or Type II CLD. Group B compared to group A compared to group C required a significantly longer duration of oxygen therapy on the neonatal unit. All three groups were prospectively followed; the occurrence of symptoms was documented in each of the first 3 years of life and lung function was measured using a plethysmographic technique at the end of year 1. In all 3 years a significantly greater proportion of groups A and B were symptomatic compared to group C, but there was no significant difference in the proportion so affected between groups A and B. Airway resistance was higher in both groups A and B compared to C but only reached statistical significance on comparing groups A and C. We conclude oxygen dependency beyond 1 month of age, irrespective of the development of BPD, significantly increases respiratory morbidity at follow up.

Airway Resistance↗
PubMed1994

Prediction of respiratory morbidity in the third year of life in children born prematurely.

We have tested the hypothesis that recurrent respiratory symptoms in the third year of life in patients born prematurely were more likely to reflect a family history of atopy rather than adverse neonatal events. Comparison of 28 symptomatic and 72 asymptomatic children revealed that a family history of atopy (p < 0.01), prolonged dependence on respiratory support in the neonatal period (p < 0.01) and extreme immaturity (p < 0.02) were significantly commoner in the symptomatic group. The relative risk of having symptoms was 2.27 for a family history of atopy, 2.48 for prolonged dependence on respiratory support and 1.7 for low gestational age. We conclude that respiratory morbidity in the third year of life following premature delivery has a multifactorial aetiology.

Child↗
PubMed1993

The effect of variations in positive end expiratory pressure on gas exchange in ventilated children with liver disease.

The effect of varying the positive and expiratory pressure (PEEP) level during mechanical ventilation has been assessed in ten children with liver disease, mean age 3.8 years. PEEP was increased 3 cmH2O above the child's original (baseline) PEEP level and then decreased either by 3 cmH2O below the baseline or to 0 cmH2O. In all ten children increasing the PEEP above the baseline improved oxygenation; in the group overall the median PaO2 increased from 90 mmHg to 97 mmHg (P < 0.01). In eight of ten children decreasing the PEEP level below the baseline resulted in a deterioration in oxygenation; in the group overall the median PaO2 decreased from 91 mmHg to 82 mmHg (P < 0.05). Changes in PEEP levels, however, did not result in clinically significant alterations in PaCO2, heart rate or blood pressure. We conclude that modest increases in PEEP are well tolerated in children with liver disease and result in an improvement in oxygenation.

Carbon Dioxide↗
PubMed1978

The development of vision in cats after extended periods of dark-rearing.

The time course of development of visual acuity for square wave gratings was measured behaviourally in a number of cats that were reared in total darkness until they were either 4 (5 cats) or 6 (1 cat) months of age. Less extensive measurements were also made on animals reared in a similar manner until they were either 1 1/2 or 10 months old. Initially, all the animals appeared to be blind, but signs of vision became evident after periods of time in an illuminated environment that ranged from a few days, in the case of animals dark-reared for only 1 1/2 to 4 months, to 1 to 2 months for those animals that were deprived for 6 months or more. Thereafter, visual acuity as measured on a jumping stand progressively improved, reaching, in the case of animals deprived for 4 months, values that were comparable to those of normal animals (6.9 cycles/deg) after 4 months of exposure to light. The animal deprived for 6 months remained apparently blind for a month and eventually attained an acuity (5.7 cycles/deg) that was somewhat less than that of normal animals. The fact that such high acuities can be achieved after periods of binocular deprivation that extend throughout the classically defined "critical period" suggest that the effect of dark-rearing is somehow to impede the natural decline with age in the degree to which cortical neurones are susceptible to environmental modification.

Animals↗
PubMed1978

The rate of recovery of vision after early monocular deprivation in kittens.

1. Fifteen kittens were monocularly deprived of vision by suturing the lids of the right eye together for various periods of time at different ages. A simple behavioural technique was used to assess the immediate effects of the period of monocular deprivation on the visual acuity of the deprived eye as well as the time course of any subsequent recovery.2. The extent of the recovery of vision was measured under conditions where the animal was either forced to use its deprived eye by performing a reverse suture or where the animal had both eyes open after the initial period of monocular occlusion.3. The initial effects of monocular deprivation were graded in severity according to the age at which the deprivation was imposed, ranging from apparent blindness in animals deprived at 6 weeks of age to only a small loss of acuity in kittens deprived at 12 weeks of age.4. The effects of deprivation imposed from birth were particularly severe, leading to a temporary blindness. Nevertheless after a period of time that became progressively longer with increasing deprivation, all animals showed some recovery of pattern vision over the course of the next 2 or 3 months. The extent of this recovery became progressively less as the period of deprivation was prolonged. There was even some recovery of vision (an acuity of 2.5 cycles/deg) in animals that were deprived throughout the duration of the ;critical period' to 4 months of age.5. Direct comparison of the rate of behavioural recovery between animals that were reverse sutured with that of litter-mates that received binocular input after monocular occlusion to either 45 or 60 days of age proved to be remarkably similar, although the acuity that was eventually attained by the reverse sutured animals was always slightly higher.6. The recoveries observed after reverse suturing were reasonably well correlated with changes observed in the ocular dominance of visual cortical cells under similar circumstances.7. Although the recovery in these animals can be accounted for by the simple notion of a competitive interaction between the two eyes, the recovery observed in animals that had both eyes open after the initial period of deprivation cannot be so readily explained. Evidently there must be an additional non-competitive mechanism of recovery.

Age Factors↗
PubMed1977

A behavioural technique for the rapid assessment of the visual capabilities of kittens.

A behavioural method is described for the measurement of various visual spatial acuities in kittens as young as thirty days of age. Expamples are given of applications of the technique to measurement of the visual acuity for gratings in normal kittens as well as to studies of the time course of behavioural recovery from the effects of early monocular visual deprivation.

Age Factors↗
PubMed1976

Behavioural compensation of cats after early rotation of one eye.

Two cats, each with one eye surgically rotated by about 90, were trained (by two different behavioural methods) to discriminate horizontal from vertical stripes using the normal eye alone. When they had mastered the discrimination, the normal eye was occluded and the rotated eye was tested for transfer with neither stimulus reinforced. Both cats responded immediately and consistently to the same stimulus that they had learned to choose with the normal eye. These animals seem to have adapted to eye-rotation not only in terms of spatial localization but also in terms of the recognition of the orientation of contours. These behavioural compensations cannot be accounted for by simple changes in the organization of the visual cortex.

Adaptation, Physiological↗