Biomedical subjects

A Greenough

Publications and source records attributed to A Greenough.

At least 19 recordsLinked to original sources

PubMed1995

Antiviral therapy in neonatal chronic lung disease.

Infants born prematurely who develop chronic lung disease frequently suffer acute respiratory deteriorations. In a randomized trial, we assessed if treatment of such relapses with the antiviral agent Ribavirin increased the speed of recovery and improved lung function at follow-up. During the acute deterioration and its treatment, respiratory rate and requirement for respiratory support were recorded. Once discharged from hospital, respiratory symptoms and admissions for chest-related illnesses were documented. Infants were recalled at 6 months of age for lung function measurements. Forty-four infants (23 given Ribavirin), median gestational age of 26 weeks, completed the trial and had lung function measurements at 6 months. Although viral infections were identified in relatively few patients, the interim analysis demonstrated Ribavirin administration for 3 days was associated with a greater reduction in respiratory rate and inspired oxygen concentration (P < 0.02). At follow-up, there was no significant difference between groups in the proportion of infants who were symptomatic or required re-admission to hospital for chest-related illnesses; the Ribavirin group, however, had lower airways resistance (P < 0.01) and higher specific conductance (P < 0.02). We conclude that antiviral therapy seems to speed the rate of recovery from acute respiratory deteriorations seen in preterm infants with chronic lung disease; this is associated with improved lung function, but not lower respiratory morbidity, at follow-up.

Administration, Inhalation↗

PubMed1995

Meconium aspiration syndrome--prevention and treatment.

Meconium aspiration syndrome (MAS) is a common neonatal problem and, sadly, results in acute and chronic respiratory morbidity. Although meconium aspiration can occur prior to delivery even in the absence of labour, in many infants this condition could be prevented by appropriate suctioning at birth. More accurate prediction of high risk patients and greater use of amnioinfusion may further reduce the occurrence of MAS. In infants with severe respiratory failure both high frequency ventilation and extracorporeal membrane oxygenation have a role. The place for either steroid or exogenous surfactant therapy in MAS remains to be defined.

Amniotic Fluid↗

PubMed1995

Volume delivery during positive pressure inflation--relationship to spontaneous tidal volume of neonates.

Volume delivery by positive pressure inflation was determined in 20 premature infants and 10 infants born at term on days 1 and 2. The spontaneous tidal volume, respiratory rate and inspiratory to expiratory (I:E) ratio were measured daily in the first week of life in an additional group of 20 infants born prematurely. Measurements were made using a pneumotachograph only when the infants were stable and had acceptable blood gases for at least 2 h. There was variability between individuals but the median delivered volume by positive pressure ventilation ranged between 4.9 and 6.1 ml/kg on days 1 and 2 and within the groups of different maturity. There was no significant difference in the results of infants born prematurely or at term or when studied on days 1 or 2. The median spontaneous tidal volume during the first week of life varied between 5.4 and 6.7 ml/kg; respiratory rate between 72 and 80 breaths/min and I:E ratio from 0.67 to 0.77. Postnatal age had no significant effect on the results. These results suggest volume delivery by positive pressure inflation during a stable period of ventilation is similar to the spontaneous tidal volume.

Forced Expiratory Flow Rates↗

PubMed1995

High frequency oscillation, respiratory activity and changes in blood gases.

Spontaneous respiratory activity during high frequency oscillation (HFO) and its relationship to changes in blood gases on transfer to HFO has been assessed. Eighteen infants were studied, median gestational age 27 weeks and postnatal age 1 day. Simultaneous measurements of changes in oesophageal and airway pressure, flow and volume were made during a period of conventional ventilation and then during HFO. From these recordings, the infants' spontaneous respiratory rate during the two ventilatory techniques were calculated. Arterial blood gases were measured immediately before and after a 30-min period of HFO. All the infants were breathing during conventional ventilation (median rate of 55 breaths/min). On transfer to HFO, the respiratory rate of the whole group decreased to a median of 23 breaths/min (P < 0.001), but only five infants became apnoeic. The changes in respiratory rate did not relate significantly to changes in PaCO2. Oxygenation deteriorated in four of the five apnoeic infants and in the two infants who became agitated during HFO. In the remaining 11 infants, whose median respiratory rate was 28 breaths/min (range 15-77) during HFO, oxygenation improved by a median of 12 mmHg (range 4-42). We conclude that, in the majority of infants, spontaneous respiratory activity during HFO is compatible with improvements in blood gases.

Carbon Dioxide↗

PubMed1995

Patient-triggered ventilation.

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Humans↗

PubMed1995

Surfactant replacement therapy for non-respiratory distress syndrome neonatal respiratory disease--research or clinical application?

Research studies have highlighted both physiological and pathological evidence to incriminate surfactant abnormality and/or deficiency in many neonatal respiratory diseases. Data from animal models and clinical studies support the concept that surfactant replacement therapy (SRT) may have a role to play in such problems. There is now, therefore, a need to perform further randomized controlled trials to assess the appropriate clinical application of SRT in non-respiratory distress syndrome neonatal respiratory disease.

Hernia, Diaphragmatic↗

PubMed1995

Functional residual capacity to thoracic gas volume (FRC:TGV) ratio in healthy neonates.

Gas trapping has been suggested to be common in healthy newborns in the immediate postnatal period. To determine the veracity of that finding, functional residual capacity (FRC) and thoracic gas volume (TGV) were measured in such a population and the FRC:TGV ratios were related to measurements of airway resistance (RAW). FRC was assessed by a helium gas dilution technique, TGV and RAW by plethysmography. Twenty-four healthy infants born at term were studied at a median age of 2 days (range 1-5 days). None had respiratory problems, nor had their mothers undergone invasive antenatal procedures. Their median FRC, which was 27.1 (range 23.8-32.0) ml kg-1, was significantly lower than their TGV (median 29.8, range 26-33 ml kg-1, P < 0.01). The mean 'within subject' difference between FRC and TGV was 2.5 (range 0.3-5.5) ml kg-1. The median FRC:TGV ratio was 0.93 (range 0.82-0.99). Eight infants had an FRC:TGV ratio less than 0.9, two of whom were studied on the first postnatal day. No infant with a low (< 0.9) FRC:TGV ratio had an abnormal RAW. The differences between FRC and TGV demonstrated in this study were smaller than documented in earlier series, suggesting the degree of gas trapping may previously have been over-estimated.

Airway Resistance↗

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

Preterm prelabour amniorrhexis: intrauterine infection and interval between membrane rupture and delivery.

This study aimed to determine if fetal bacteraemia and amniotic fluid infection at the time of membrane rupture reduces the interval between membrane rupture and the onset of labour in pregnancies complicated by preterm prelabour amniorrhexis. Sixty nine pregnancies with preterm prelabour amniorrhexis at 12-36 weeks' gestation that were managed expectantly had spontaneous onset of labour. In all cases cordocentesis and amniocentesis were performed and fetal blood and amniotic fluid were cultured for aerobic and anaerobic bacteria. In the group with negative fetal blood and amniotic fluid cultures (group 1) the median interval from amniorrhexis to delivery was 41 days (range 1-161) and there was an inverse correlation between gestational age at amniorrhexis and delivery interval. In the group with negative fetal blood but positive amniotic fluid cultures (group 2) the median amniorrhexis to delivery interval was nine days (range 1-37), and in the group with positive fetal blood cultures (group 3) the interval was two days (range 1-5). These findings suggest that pregnancies complicated by preterm prelabour amniorrhexis and fetal bacteraemia undergo spontaneous labour within five days of membrane rupture, and if labour does not occur then infection is unlikely.

Amniotic Fluid↗

PubMed1995

Measurement of lung volume and optimal oxygenation during high frequency oscillation.

Twelve infants, median gestational age 27 weeks and postnatal age 1 day, were examined to determine whether oxygenation improves on transfer to high frequency oscillation (HFO). Lung volume was assessed before transfer to HFO by measuring functional residual capacity (FRC) using a helium gas dilution technique and specially designed infant circuit. On transfer to HFO, the inspired oxygen was initially kept constant, but the mean airway pressure (MAP) increased until maximum oxygenation was achieved (optimal MAP). The median FRC of the 12 infants before HFO was 8.1 ml/kg (range 4.7 to 28.7) and their median alveolar-arterial oxygen gradient (A-aDO2) 484 mm Hg. On transfer to HFO, oxygenation did not improve in two infants, but, overall, the A-aDO2 fell to a median of 289 mm Hg (p < 0.05). The median optimal MAP was 18.5 cm H2O (range 10.6 to 24.4) and this had an inverse correlation with the FRC before starting HFO (p < 0.01). The median change in MAP needed to maximise oxygenation on HFO also correlated negatively with FRC (p < 0.01).

Functional Residual Capacity↗

PubMed1995

Synchronous intermittent mandatory ventilation modes compared with patient triggered ventilation during weaning.

The efficacy of combining rate and pressure reduction during weaning by synchronous intermittent mandatory ventilation (SIMV) were compared with weaning by patient triggered ventilation (PTV) (pressure reduction alone) in two randomised trials. Regardless of ventilation mode, pressure was reduced to the same level according to the size of the infant. In the first trial, the SIMV rate was also reduced progressively to a minimum of 20 breaths/minute, and in the second to five breaths/minute. Forty premature infants aged 15 days of age or less were randomly allocated into each trial. No significant differences were found in the first trial between ventilation modes in either the duration of weaning or the number of infants in whom weaning failed. In the second trial, the duration of weaning was shorter by PTV than by SIMV (median 24 hours, range 7-432 v 50 hours, range 12-500; p < 0.05); weaning failed in two infants in the PTV group and in five in the SIMV group. It is concluded that weaning by a combination of pressure and rate reduction, such as can be achieved during SIMV, offers no significant advantage over pressure reduction alone.

Ductus Arteriosus, Patent↗

PubMed1995

Ethnic origin and lung function of infants born prematurely.

BACKGROUND: Ethnic origin has an important influence on the lung function of adults and young children but its effect during infancy, particularly following premature delivery, is unclear. METHODS: The results from infants of pure Afro-Caribbean (subjects) and pure Caucasian (controls) descent, all of whom were born prematurely (median gestational age 28 weeks), were compared. Fifty subjects were each retrospectively matched with a control for gestational age, sex, and requirement for neonatal ventilation. Lung function measurements were performed at similar postnatal ages in each pair. The median postnatal ages of the two groups at the time of study was seven and eight months, respectively. Lung function was assessed by measurement of functional residual capacity (FRC) by a helium gas dilution technique and plethysmographic measurement of thoracic gas volume (TGV) and airways resistance (Raw), from which specific conductance (sGaw) was calculated. RESULTS: No differences were found between the subjects and controls regarding FRC or TGV, but Raw was higher and sGaw lower in the subjects. The mean Raw of the subjects was 50.3 cm H2O/1/s and of the controls was 44.1 cm H2O/1/s (95% confidence intervals of the difference 1.5 to 10.9). CONCLUSIONS: Prematurely born infants of Afro-Caribbean origin have more severe lung function abnormalities at approximately 7-8 months of age than those of Caucasian origin. This merits further investigation.

Black People↗

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

Influence of lung function and reflex activity on the success of patient-triggered ventilation.

The influence of lung function and reflex activity on the success of patient-triggered ventilation (PTV) has been determined. Lung function was assessed by measurement of compliance using a single breath technique. Reflex activity was assessed by measurement of the strength of Hering Breuer reflex indicated by the degree of prolongation of expiration following end inspiratory occlusion. PTV was considered to have failed if the infant became apnoeic or required an increased level of respiratory support. Twenty premature infants (median gestational age 29 weeks) in the recovery stage of respiratory distress, were studied at a median postnatal age of 2.5 days. PTV failed ultimately in six infants, although compliance of the respiratory system of that group did not differ significantly from the rest of the cohort, their Hering Breuer reflex was significantly weaker (P < 0.01). In addition, the infants in whom PTV failed were significantly more immature and of lower birthweight (P < 0.01) compared with those in whom it succeeded. We conclude that failure of PTV is more likely in immature infants who have a weak Hering Breuer reflex.

Humans↗

PubMed1994

Birth weight and hospital readmission of infants born prematurely.

OBJECTIVE: To determine whether the hospital readmission rate of infants born prematurely was greatest in those whose birth weight was less than 750 g. DESIGN: A prospective cohort study. SETTING: Regional neonatal intensive care unit. PATIENTS: Consecutive very-low-birth-weight (< 1500 g) infants admitted to the neonatal intensive care unit; infants with congenital abnormalities were excluded. Two-year follow-up was completed for 109 (90.8%) of these patients. MEASUREMENTS/MAIN RESULTS: Following discharge from the neonatal intensive care unit, infants were seen at 6-month intervals at which time a detailed history was taken and examinations were performed. Hospital admissions were documented and confirmed from the medical records. Infants with birth weights of less than 750 g and those of very-low gestational age (< or = 28 weeks) made up the greatest number of admissions and had the longest hospital stays. In the first year of life, the duration of stay was inversely related to birth weight. CONCLUSION: Increased survival of extremely low-birth-weight infants has important implications for resource allocation of pediatric beds.

Birth Weight↗

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

Measurement of thoracic gas volume in patients born prematurely: should occlusion be made at end-inspiration or end-expiration?

It has been suggested that in infants born at term thoracic gas volume (TGV) may be more accurately estimated in a plethysmograph if end-inspiratory (TGVl) rather than end-expiratory (TGVE) occlusions are used. The aim of this study was to assess whether the timing of occlusion affected TGV results in patients born very prematurely. Fifteen children with a median gestational age of 28 weeks (range 23-34) and postnatal age of 10 months (range 6-24) were studied. Measurements of TGV and airway resistance (R(aw)) were made in a whole body plethysmograph after sedation with chloral hydrate. End-expiratory and end-inspiratory occlusions were performed randomly in each subject. Overall, TGVl was significantly lower than TGVE (median, TGVl 233 mL; range, 130-498. Median TGVE 250 mL; range, 132-604; P < 0.05; 95% confidence intervals for the difference, 4-50 mL). In 13 infants, TGVl was lower than TGVE; the remaining two patients did not differ significantly from the rest of the group and neither had neonatal chronic lung disease. In only five infants did TGVl lie below the 95% confidence intervals of TGVE, however, two-way analysis of variance with replicated measurements showed a significant difference between TGVE and TGVl (P < 0.05). The median R(aw) was 55 cmH2O/L/s (range, 36-71). A significant positive correlation was found between R(aw) and TGVE-TGVl (r2 = 0.5, P < 0.01). We conclude that in children born very prematurely and with high R(aw) occlusion at end-expiration rather than end-inspiration yields higher TGV results at follow-up.

Airway Resistance↗