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Biomedical subjects

G Dimitriou

Publications and source records attributed to G Dimitriou.

At least 55 records · Page 3Linked to original sources
PubMed1999

Neonatal lung function in very immature infants with and without RDS.

Some infants, despite being born at low gestations (< 28 weeks gestational age) do not develop RDS and are not surfactant treated. The changes in lung function during the neonatal period in such infants have not been explored, hence it is unknown whether they are similar to those of surfactant treated infants with RDS of similar gestational age. Such data would facilitate assessment of the impact of surfactant administration on the lung function abnormalities of very immature infants with RDS. We, therefore, compared the results of neonatal lung function measurements from immature infants with RDS who received surfactant to those from infants with non-RDS respiratory distress not so treated and matched to the RDS infants for gestational age and within 10% of birthweight. Compliance and functional residual capacity (FRC) were measured daily for the first five days and then at 1, 2 and 4 weeks in 16 infants, median gestational age 27 weeks (range 25-27 weeks). Although exogenous surfactant administration to the immature infants with RDS was associated with improvements in lung function, the non RDS, non surfactant treated infants had both higher compliance (p < 0.05) and lung volumes (p < 0.01) throughout the perinatal period. These results demonstrate surfactant administration does not fully correct the perinatal lung function abnormalities of very immature infants with RDS.

Birth Weight↗
PubMed1998

Comparative effects of theophylline and caffeine on respiratory function of prematurely born infants.

The aim of this study was to determine the relative effects of theophylline and caffeine on neonatal respiratory function. Fifty-three preterm infants (45 infants with a median gestational age of 28 weeks, range 24-34 weeks completed the protocol) were randomized to receive either theophylline (loading dose 4 mg/kg followed by 4 mg/kg/day) or caffeine (loading dose 10 mg/kg followed by 5 mg/kg/day). Compliance of the respiratory system (CRS), strength of Hering Breuer reflex and the inspired oxygen concentration requirement were measured immediately prior to, 24 h and 7 days after commencing therapy. There was no statistically significant difference in the patient characteristics of the two groups, but only the theophylline group contained immature infants (i.e. < 26 weeks gestational age (n = 7)). At 24 h, there was a significant improvement in CRS and reduction in supplementary oxygen requirements in the caffeine group (p < 0.01), in the theophylline group no such significant effects were seen. In the study population overall, after 7 days of treatment in both the theophylline and caffeine groups there was an improvement in CRS (p < 0.05 and p < 0.01 respectively) and a reduction in the inspired oxygen concentration (p < 0.05 and p < 0.01 respectively). There was, however, a significant reduction in the strength of the Hering Breuer reflex only in the caffeine group (p < 0.05) and this was a decrease which related to the change in CRS (p < 0.05). The only statistically significant difference in the magnitude of change in CRS, reflex strength or supplementary oxygen requirements between the two groups was that the reduction in inspired oxygen requirement in the caffeine group was greater than that in the theophylline treated infants at 24 h (p < 0.05). We conclude theophylline and caffeine have similar effects on neonatal respiratory function, but our results suggest caffeine administration may be associated with an earlier onset of action.

Bronchodilator Agents↗
PubMed1998

Lung volume measurements in infants with and without chronic lung disease.

UNLABELLED: Infants born prematurely who develop chronic lung disease (CLD) have airways obstruction and hence may have low lung volume. The aim of this study was to test that hypothesis and ascertain whether the nature of the comparison control group influenced the results. Sixteen infants who were oxygen dependent for more than 28 days (CLD) and eight infants without CLD had measurements of functional residual capacity (FRC) at 14 and 28 days. The 16 CLD infants consisted of eight less than 27 weeks gestational age (group A) and eight greater than 26 weeks gestational age (group B). The eight infants without CLD (group C) were each matched for gestational age and gender to infants in group B. Group A compared to group C had lower FRCs both at 14 days (median 18 ml/kg vs 27 ml/kg, P < 0.01) and 28 days (median 20 ml/kg vs 26 ml/kg, P < 0.05), but group A differed from group C with respect to both gestational age (P < 0.01) and birth weight (P < 0.01). The FRC results of group B were lower than those of their matched controls (group C) only at 28 days (median 22 vs 26 ml/kg, P < 0.05). Overall, the FRC results at 14 and 28 days correlated significantly with the duration of oxygen and ventilator dependence and weakly with gestational age. CONCLUSION: These results support the hypothesis that FRC results are lower in infants with CLD compared to those without CLD when measured in the neonatal period and emphasize the importance of an appropriate control group. Measurement of lung volume may facilitate assessment of the response to therapies for CLD.

Birth Weight↗
PubMed1998

Serial lung volume measurements during the perinatal period in infants with abdominal wall defects.

METHODS: Daily measurements of lung volume (functional residual capacity, FRC) were made during the perinatal period in eight infants (median gestational age, 37 weeks; range, 34 to 38 weeks) with abdominal wall defects. RESULTS: On the first day of life and before surgical intervention, four infants had FRCs below the reference range; the occurrence of low lung volumes was not significantly related to gestational age or diagnosis. Lung volume was further, but only temporarily, impaired by surgical closure of the abdominal wall defect, with a reduction in the median FRC from 25 mL/kg (range, 18 to 36) preoperatively to 12 mL/kg (range, 5 to 19) on the first postoperative day (P < .02). CONCLUSION: These data are consistent with abnormal antenatal lung growth in certain infants with abdominal wall defects.

Abdominal Muscles↗
PubMed1998

Comparison of airway pressure-triggered and airflow-triggered ventilation in very immature infants.

Failure of patient-triggered ventilation in very immature infants may be due to the use of inappropriate triggering systems. Two types of airflow trigger were therefore compared consecutively to an airway pressure (SLE) triggering system. Each comparison was made in 10 infants, < or =28 weeks of gestation. Comparison was made of the delivered volume, trigger performance and blood gases using each system for 1 h. Both comparisons showed that the airflow triggering systems performed better: one (Draeger Babylog 8000) had a higher sensitivity (p < 0.01) and the other (Bird VIP airflow trigger), in which inflation was terminated by sensing a reduction in inspiratory flow, had a lower degree of asynchrony (p < 0.01) and a tendency to deliver higher volumes. These results suggest that triggering systems sensing airflow changes may be superior to those sensing airway pressure changes in very immature infants. The use of a mechanism to synchronize the termination of inflation to the end of the patient's inspiration may offer further advantages.

Humans↗
PubMed1998

Assessment of prematurely born children at follow-up using a tidal breathing parameter.

Prematurely born children frequently have respiratory problems at follow-up. A non-invasive and easily performed lung function test would greatly facilitate their evaluation and appropriate treatment. We have, therefore, assessed whether the shape of the tidal breathing expiratory flow curve would give useful information in such a population. One hundred and twenty traces were randomly selected from plethysmographic measurements of thoracic gas volume and airway resistance made during a follow-up study of a prematurely born population. The children had a median gestational age of 29 (range 23-35, interquartile range 27-31) weeks and postnatal age at the time of measurement of 11 (range 6-24, interquartile range 7-13) months. From the flow and volume signals, the mean time to reach peak tidal expiratory flow as a proportion of the total expiratory time (tPTEF : tE) was determined for each child. The median tPTEF : tE differed significantly between children who, in the neonatal period, had or had not required mechanical ventilation (p < 0.001) and had or had not had an increased inspired oxygen requirement (p < 0.01), and who were or were not symptomatic at follow-up (p < 0.001). Logistic regression analysis demonstrated that a low tPTEF : tE ratio was independently associated with symptom status. These results suggest that assessment of a tidal breathing parameter during follow-up of prematurely born children may be useful. As tPTEF : tE can be measured without sedation, relatively quickly and with simple equipment, potentially large study populations could be investigated, and this technique should now be evaluated in a non-sedated group of young prematurely born children.

Birth Weight↗
PubMed1998

Influence of ethnic origin on respiratory distress syndrome in very premature infants.

AIM: To determine whether the incidence of respiratory distress syndrome (RDS) is related to ethnic origin in very premature infants (< or = 32 weeks of gestational age and birthweight < or = 2.0 kg). METHOD: A retrospective cohort study was performed to determine the incidence of respiratory disorders in African, Caribbean, and caucasian infants. An African infant was matched with two infants (one of Caribbean and one of caucasian descent) for gestational age and birth order and, if several eligible matching infants were found, for gender and approximate birth date. Fifty African infants (median gestational age 28 weeks, range 23-32) were matched with an infant of Caribbean and one of caucasian descent. RESULTS: Compared with the incidence of RDS in African infants (40%), that in caucasian infants (75%) was significantly higher (p < 0.05), while the incidence in the Caribbean infants (54%) did not differ significantly. Regression analysis showed that ethnic origin was related to the occurrence of RDS independent of gestational age, size for dates, antenatal steroids, hypertension during pregnancy, premature rupture of membranes, maternal smoking, mode of delivery and infant gender. CONCLUSION: The enhanced lung maturation found in certain ethnic groups, even when born prematurely, has implications for clinical management.

Africa↗
PubMed1998

Volume delivery during high frequency oscillation.

AIM: To examine the delivered volume during "high volume strategy" high frequency oscillation, used as rescue treatment in preterm infants; and to identify factors, other than frequency and oscillatory amplitude, influencing the magnitude of volume delivery. METHOD: Twenty infants (median gestational age 29 weeks) were studied on 45 occasions. Two oscillator types were used (SensorMedics and SLE). Delivered volume was measured under clinical conditions with the arterial blood gases within a predetermined range. A specially calibrated pneumotachograph system was used. RESULTS: Overall, the median delivered volume was 2.4 ml/kg (range 1.0 to 3.6 ml/kg); on 32 occasions the delivered volume was greater than 2.0 ml/kg and on seven greater than 3.0 ml/kg. The delivered volume related significantly to disease severity; there was an inverse correlaton between delivered volume and both the oxygenation index (OI) (r = -0.51) and AaDO2 (r = -0.54). CONCLUSION: Delivered volume during HFO may, in certain infants, exceed the anatomical dead space, permitting some direct alveolar ventilation.

High-Frequency Ventilation↗
PubMed1998

Comparison of respiratory function and fluid balance in very low birthweight infants given artificial or natural surfactant or no surfactant treatment.

Exogenous surfactant administration improves respiratory function. The speed of improvement appears greater if a natural rather than an artificial surfactant is used, our aim was to determine if that effect was explained by differences in fluid balance, evidenced by the timing of the diuresis onset (i.e. output greater than input). Thirty infants (median gestational age 29 weeks), 10 given an artificial surfactant (Exosurf), 10 a natural surfactant (Survanta) and 10 no surfactant (controls) were studied. During the first three days, compliance and functional residual capacity were measured daily, arginine vasopressin (AVP) levels estimated on days 1, 3 and 5 and, in 8-hourly intervals, the median arterial/alveolar ratio was calculated for each individual and urine output and fluid input recorded. Throughout the three-day period, the median arterial/alveolar ratio was always significantly higher in the control compared to the two surfactant groups (p < 0.05). On day 3 the Exosurf-treated babies had lower compliance and functional residual capacity (p < 0.05) than the other two groups. Neither the timing of diuresis onset, timing of the maximum diuresis nor the AVP levels, however, differed significantly between the groups. Only surfactant treatment and type of surfactant, but not the timing of the onset nor of the maximum diuresis, related significantly to changes in lung function. These results do not support the hypothesis that differences in fluid balance explain differences in the lung function improvement rate following natural and artificial surfactant.

Biological Products↗
PubMed1997

Inhaled versus systemic steroids in chronic oxygen dependency of preterm infants.

UNLABELLED: The speed of action and side-effects of systemic verus inhaled steroids was compared in infants with mild-moderate oxygen dependency. Forty infants (median gestational age 27 weeks) were randomized to receive either 10 days of dexamethasone (systemic group) or budesonide (100 micrograms qds) (inhaled group). At randomization, there was no significant difference in the gestational or postnatal age, inspired oxygen requirements or compliance of the respiratory system of the two groups. After 36 h of treatment, there were significant changes (P < 0.01) in both the inspired oxygen concentration and compliance of the respiratory system in the systemic but not the inhaled group. Only after 1 week of inhaled therapy were improvements in respiratory status noted but, even at that time, the inspired oxygen requirement was significantly lower in the systemic versus the inhaled group. In the systemic group only, however, were there significant increases in blood pressure. CONCLUSION: Systemically administered rather than inhaled steroids appear to have a faster onset of action.

Administration, Inhalation↗
PubMed1997

Risk factors for hyperinflation in young schoolchildren born prematurely.

UNLABELLED: Lung function abnormalities, including hyperinflation, are common in young children born prematurely. The aim of this study was, in such patients, to determine factors associated with hyperinflation, that is an elevated lung volume. Lung volume was estimated by measuring functional residual capacity (FRC) before and after bronchodilator therapy in 41 5-year-old children who had been born prematurely at a median of 30 weeks gestational age. Hyperinflation was defined as an FRC greater than 120% of that predicted for height and a positive bronchodilator response as a greater than or equal to 10% change in FRC. Twelve (29%) of the children were symptomatic at 5 years, their median FRC (132%) was significantly higher than that of the asymptomatic children (109%), P < 0.01). Twelve (29%) children were hyperinflated; a greater proportion of the hyperinflated compared to the non-hyperinflated patients were symptomatic at 5 years (7 or 58% versus 5 or 17%) (P < 0.05) and responded to bronchodilator therapy (9 or 75% versus 4 or 14%) (P < 0.01). Regression analysis demonstrated that hyperinflation related significantly only to current symptom status, but not perinatal variables. CONCLUSION: Hyperinflation in young children born prematurely reflects current symptom status and not adverse neonatal events.

Bronchodilator Agents↗
PubMed1997

Perioperative assessment of respiratory compliance and lung volume in infants with congenital diaphragmatic hernia: prediction of outcome.

BACKGROUND/PURPOSE: Infants who have congenital diaphragmatic hernia (CDH) have high mortality and morbidity. The aim of this study was to determine the relative ability of the results of serial measurements of compliance of the respiratory system (CRS) and lung volume (functional residual capacity (FRC)) to predict poor outcome: death or oxygen dependency at 28 days. In addition, the authors wished to document the evolution of any lung function abnormalities during the perioperative period. METHODS: Daily measurements of CRS and FRC were made in the first week of life and subsequently during week 2 in 16 infants who had a median gestational age of 38 weeks and birth weight of 3.2 kg. RESULTS: Seven infants had a poor outcome: five died and two others remained oxygen dependent beyond 28 days. The infants who had a poor outcome were characterized on day 1 by a significantly lower CRS, but not FRC (P < .05). In comparison with results from day 1, the median CRS of the infants overall had significantly improved only by week 2 (P < .05), there was no such significant change in FRC with increasing postnatal age. At week 2, only the CRS results differed significantly between those infants who had and who did not have poor outcome (P < .05). CONCLUSION: The results of serial measurements of CRS, rather than FRC are the more useful predictor of outcome in infants who have CDH.

Female↗
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↗
PubMed1997

Changes in lung volume, compliance and oxygenation in the first 48 hours of life in infants given surfactant.

Changes in lung volume (functional residual capacity) compliance and oxygenation in the first 48 h of life in infants given surfactant replacement therapy were studied. Fourteen infants, median gestational age 30 weeks (range 26-35), who were given two doses of an artificial surfactant (Exosurf) at approximately 2 h of age and 12 h later, were examined. Compared to baseline, functional residual capacity, compliance of the respiratory system and oxygenation, significantly improved at 24 and 48 hours, but specific compliance (compliance/functional residual capacity) decreased. The greater changes, however, were experienced between baseline and 24 h. These data suggest that the elevation of FRC over the first 48 hours of life may be due to increased distension as well as recruitment of alveoli.

Gestational Age↗
PubMed1996

Lung volume measurements immediately after extubation by prediction of "extubation failure" in premature infants.

To test the hypothesis that premature infants in whom extubation fails in the first 10 days of life have low volume lungs, functional residual capacity (FRC) was measured in the first hour after extubation. Once extubated, infants received the appropriate level of inspired oxygen necessary to maintain acceptable arterial oxygen saturation. After humidification, oxygen was bled into a headbox, and FRC was assessed using a helium gas dilution technique and a specially designed infant circuit. The results were related to extubation failure, which was diagnosed when the infant required nasal continuous positive airway pressure or re-intubation and ventilation within 48 hours. The latter two forms of respiratory support were instituted by the clinical team, whenever the infant developed recurrent or severe apnea or respiratory acidosis. Infants were eligible for entry into the study when born prematurely and extubated within the first 10 days of life. Twenty infants initially ventilated for respiratory distress syndrome at a median gestational age of 29 weeks (range, 26-36 weeks) were studied at a median postnatal age of 3 days (range, 1-7 days). All were receiving theophylline. Extubation failed in seven infants, who did not differ significantly from the rest of the cohort regarding gestational age, birthweight, postnatal age, or inspired oxygen concentration (F(I)O2) at extubation, but their maximum F(I)O2 during ventilation was higher than in those infants who did not require reintubation (P < 0.05). In the infants who failed extubation, the median FRC was 19 ml/kg (range, 12-27 ml/kg), which was lower than that of the infants in whom extubation was successfully accomplished (median, 28 ml/kg; range, 19-37 ml/kg; P < 0.01). An FRC of less than 26 ml/kg had a sensitivity of 71% and specificity of 77% in predicting extubation failure. These results support the hypothesis that a very low lung volume relates to extubation failure in the first 10 days of life.

Female↗
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↗