Biomedical subjects

G Dimitriou

Publications and source records attributed to G Dimitriou.

63 records · Page 4Linked to original sources

PubMed1996

Early measurement of lung volume--a useful discriminator of neonatal respiratory failure severity.

Respiratory distress syndrome (RDS) is characterized by lungs having collapsed alveoli (atelectasis) which reduces the volume of the gas-containing spaces of the lung. It seems likely, therefore, that measurement of lung volume might discriminate between infants with severe respiratory failure due to RDS and those with minimal respiratory distress. To test this hypothesis, lung volume was measured at end expiration, that is functional residual capacity (FRC), in 40 infants (median gestational age 29 weeks, range 24-35) all mechanically ventilated from birth. FRC was measured using a helium gas dilution technique at a median of 3 h of age. The infants were divided into two groups according to their FRC results: group A (n = 29) low FRC (FRC < 24 ml kg-1) and group B (n = 11) normal FRC (FRC > or = 24 ml kg-1). The clinicians were unaware of the FRC results. There was no significant difference in the gestational age or birthweight of the two groups, but group A were characterized by a significantly greater proportion requiring surfactant replacement therapy (p < 0.01), a higher maximum peak inspiratory pressure (p < 0.01) and inspired oxygen requirement (p < 0.01). A low FRC had 79% sensitivity and 91% specificity in predicting a requirement for surfactant replacement therapy. We conclude that measurement of FRC in the first hours of life does allow discrimination of disease severity.

Functional Residual Capacity↗

PubMed1996

Respiratory morbidity in young school children born prematurely--chronic lung disease is not a risk factor?

UNLABELLED: Children born prematurely and recruited into a prospective follow up study were examined at 5 years of age. Our aim was to determine aetiological associations of respiratory symptoms in such children and, in particular, to determine the importance of severe chronic lung disease (CLD, oxygen dependence beyond 36 weeks post conceptional age). Respiratory status was documented from parental history in 103 children of median gestational age 29 weeks (range 23-35), 17 of whom had suffered from severe CLD. In 90 of the 103 children lung function had been assessed at 1 year of age. Regression analysis revealed that neither severe CLD nor other perinatal variables, but only a family history of atopy, significantly related to a positive symptom status. A high airways resistance at 1 year also significantly related to positive symptom status. CONCLUSION: Reduction in severe CLD (oxygen dependence beyond 36 weeks postconceptional age) may make relatively little impact on respiratory morbidity in young school children born prematurely.

Bronchopulmonary Dysplasia↗

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

Prognostic indicators in congenital diaphragmatic hernia.

Congenital diaphragmatic hernia is associated with significant mortality and morbidity. The aim of this study was to compare a series of tests with respect to prediction of outcome. Tidal volume and compliance of the respiratory system (CRS) were measured preoperatively and on the first and second postoperative days. The maximum and modified ventilation indexes and the maximum Paco2 were noted for the first 6 hours of life and the first 6 hours postoperatively. In addition, it was recorded whether the stomach was within the ipsilateral hemithorax preoperatively. Twenty infants were studied (median gestational age, 38 weeks; range, 31 to 40), six of whom had a poor outcome, ie, they died or remained oxygen-dependent after 28 days. A CRS of less than 0.18 mL/cm H2O/kg was the most accurate predictor of poor outcome, with 66% sensitivity and 100% specificity. The authors conclude that lung function measurement are useful in the assessment of infants with congenital diaphragmatic hernia.

Carbon Dioxide↗

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

The appearance of "early" chest radiographs and the response to surfactant replacement therapy.

We have assessed whether the appearance of the chest radiograph performed within the first 2 h of birth was predictive of the response to exogenous surfactant replacement therapy (SRT), as indicated by changes in sensitive indices of disease severity, that is lung volume (functional residual capacity (FRC)) and oxygenation (a/A ratio). 18 premature infants who received two doses of a synthetic surfactant (Exosurf) were studied. The appearances of chest radiographs taken prior to the first and immediately after the second dose of SRT were scored for lung volume, degree of inflation, presence of opacification, interstitial shadows and air bronchograms. At similar times, FRC was measured and the a/A ratio calculated. Although following SRT, the chest radiograph score decreased (p < 0.01) and the FRC (p < 0.01) and a/A ratio (ns) improved, there was no significant relationship between the change in chest radiograph score and either the change in FRC or a/A ratio. In addition, only the post-SRT chest radiograph appearance correlated significantly with the respective FRC, a/A ratio and outcome (death or oxygen dependency beyond 28 days). Although the appearance of an early chest radiograph is frequently used as an indicator of the need for SRT, these results demonstrate that, unlike the post-SRT radiograph, it is a poor predictor of the response to SRT and outcome.

Functional Residual Capacity↗

PubMedDate not supplied

Neonatal outcome following early onset preterm premature rupture of the membranes--a case controlled study.

A case-controlled study was performed to determine whether preterm premature rupture of the membranes (PPROM), particularly if occurring in the second trimester, increased the duration of ventilatory support or hospital admission. Infants born after membrane rupture of at least 24 hours duration and prior to 37 weeks of gestation were identified. It was possible to match for gestational age and birthweight 40 PPROM infants, 15 of whom had onset of rupture of the membranes (ROM) prior to 27 weeks of gestation, with a control (an infant whose mother had not suffered PPROM). A greater proportion of the mothers of the PPROM infants had received antenatal steroids (p<0.01), had an antepartum hemorrhage (p=0.06) or delivered vaginally (p<0.02). More PPROM infants had pulmonary hypoplasia (p<0.03) or infection (p<0.01). Overall, however, and if only those matched pairs where membrane rupture had occurred prior to 27 weeks of gestation were considered, there were no statistically significant differences in the duration of ventilatory support or hospital admission. Step-wise regression analysis confirmed that in the study population overall and in the matched pairs where membrane rupture had occurred at less than 27 weeks of gestation, neither the duration of ventilation nor hospital admission significantly related to PPROM. These findings have implications when counselling parents.

Case-Control Studies↗