Gabriel Dimitriou

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, ≤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 patients inspiration may offer further advantages.

Comparison of airway pressure and airflow triggering systems using a single type of neonatal ventilator

The performances of two triggering systems using a single neonatal ventilator type (SLE) were compared. Eight infants, gestational age 27–30 wk, were each recorded during two 1‐h periods of patient‐triggered ventilation (PTVs), one with airway pressure and one with airflow triggering. The airflow trigger had a shorter trigger delay (p < 0.02), higher sensitivity (p < 0.02) and lower asynchrony rate (p < 0.02).

Effect of posture on oxygenation and respiratory muscle strength in convalescent infants

Objective: To determine if differences in respiratory muscle strength could explain any posture related effects on oxygenation in convalescent neonates. Methods: Infants were examined in three postures: supine, supine with head up tilt of 45°, and prone. A subsequent study was performed to determine the influence of head position in the supine posture. In each posture/head position, oxygen saturation (Sao2) was determined and respiratory muscle strength assessed by measurement of the maximum inspiratory pressure (Pimax). Patients: Twenty infants, median gestational age 34.5 weeks (range 25–43), and 10 infants, median gestational age 33 weeks (range 30–36), were entered into the first and second study respectively. Results: Oxygenation was higher in the prone and supine with 45° head up tilt postures than in the supine posture (p<0.001), whereas Pimax was higher in the supine and supine with head up tilt of 45° postures than in the prone posture (p<0.001). Head position did not influence the effect of posture on Pimax or oxygenation. Conclusion: Superior oxygenation in the prone posture in convalescent infants was not explained by greater respiratory muscle strength, as this was superior in the supine posture.

Elective use of nasal continuous positive airways pressure following extubation of preterm infants.

Abstract The aim of this study was to determine whether elective use of nasal continuous positive airways pressure (CPAP) following extubation of preterm infants was well tolerated and improved short- and long-term outcomes. A randomized comparison of nasal CPAP to headbox oxygen was undertaken and a meta-analysis performed including similar randomized trials involving premature infants less than 28 days of age. A total of 150 infants (median gestational age 30 weeks, range 24–34 weeks) were randomized in two centres. Fifteen nasal CPAP infants and 25 headbox infants required increased respiratory support post-extubation and 15 nasal CPAP infants and nine headbox infants required re-intubation (non significant). Eight infants became intolerant of CPAP and were changed to headbox oxygen within 48 h of extubation; 19 headbox infants developed apnoeas and respiratory acidosis requiring rescue nasal CPAP, 3 ultimately were re-intubated. Seven other trials were identified, giving a total number of 569 infants. Overall, nasal CPAP significantly reduced the need for increased respiratory support (relative risk, 0.57, 95% CI 0.43–0.73), but not for re-intubation (relative risk 0.89, 95% CI 0.68–1.17). Nasal CPAP neither influenced significantly the intraventricular haemorrhage rate reported in four studies (relative risk 1.0, 95% CI 0.55, 1.82) nor that of oxygen dependency at 28 days reported in six studies (relative risk 1.0, 95% CI 0.8, 1.25). In two studies nasal CPAP had to be discontinued in 10% of infants either because of intolerance or hyperoxia.nConclusion Elective use of nasal continuous positive airways pressure post-extubation is not universally tolerated, but does reduce the need for additional support.

Prediction of extubation failure in preterm infants

Objective: To identify whether the results of assessment of respiratory muscle strength or respiratory load were better predictors of extubation failure in preterm infants than readily available clinical data. Patients: Thirty six infants, median gestational age 31 (range 25–36) weeks and postnatal age 3 (1–14) days; 13 were < 30 weeks of gestational age. Methods: Respiratory muscle strength was assessed by measurement of maximum inspiratory pressure generated during airway occlusion, and inspiratory load was assessed by measurement of compliance of the respiratory system. Results: Overall, seven infants failed extubation—that is, they required reintubation within 48 hours. These infants were older (p < 0.01), had a lower gestational age (p < 0.01), and generated lower maximum inspiratory pressure (p < 0.05) than the rest of the cohort. Similar results were found in the infants < 30 weeks of gestational age. Overall and in those < 30 weeks of gestational age, gestational age and postnatal age had the largest areas under the receiver operator characteristic curves. Conclusion: In very premature infants, low gestational age and older postnatal age are better predictors of extubation failure than assessment of respiratory muscle strength or respiratory load.

Colloid infusion in the perinatal period and abnormal neurodevelopmental outcome in very low birth weight infants

Abstract. In very low birth weight (VLBW) infants, colloid infusion is associated with impaired perinatal lung function and increased oxygen dependency duration. The aim of this study was to determine whether perinatal colloid infusion was associated with abnormal neurodevelopmental outcome. All perinatal fluid input (crystalloid and colloid) given to VLBW infants entered into a randomised trial was recorded. At 1 and/or 2 years, the neurodevelopmental status of VLBW infants was routinely assessed. Of 131 survivors, median gestational age 27 weeks (range 23–33 weeks), 95 were seen at follow-up. Nineteen had abnormal neurodevelopmental outcome and differed significantly from the rest of the cohort with regard to their birth weight, magnitude of colloid infusion received and the proportions who had received postnatal steroids, suffered prolonged oxygen dependency or having had intracerebral haemorrhage/periventricular leucomalacia development. Regression analysis demonstrated that only colloid infusion related significantly to abnormal neurodevelopmental outcome independent of other variables. Conclusion: These data suggest that colloid infusion should be used with caution in the perinatal period.

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

BACKGROUND/PURPOSEnInfants 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.nnnMETHODSnDaily 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.nnnRESULTSnSeven 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).nnnCONCLUSIONnThe results of serial measurements of CRS, rather than FRC are the more useful predictor of outcome in infants who have CDH.

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.

Comparative effects of theophylline and caffeine on respiratory function of prematurely bora 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.

Morbidity in infants with antenatally-diagnosed anterior abdominal wall defects

Abstractu2002The aims of this study were to compare the morbidity of infants with gastroschisis (GS) with that of infants with exomphalos (EX) without lethal abnormalities and to identify factors predictive of adverse outcome: a requirement for parenteral nutrition (PN) for over 1 month and hospital admission for over 2 months. The medical records of 45 infants with anterior wall defects (32 with GS) diagnosed antenatally who consecutively received intensive care in one institution from 1993 were reviewed. Both the GS and EX infants had a median gestational age of 37 weeks, but the former were lighter at birth (Pu2009<u20090.01). Fourteen infants (all with GS) were able to start feeds only after 2 weeks; 10 (8 with GS) developed liver dysfunction; and 5 (all with GS) died. The GS compared to the EX infants required a longer period of PN (median 20 vs 10 days, Pu2009<u20090.01) and longer hospital admission (median 40 vs 25 days, Pu2009<u20090.01). In the GS group the time to start feeding related independently to prolonged hospital stay, and the existence of structural bowel abnormalities (SBA) related independently to both measures of adverse outcome, with a positive predictive value of 100%. We conclude that infants with GS, particularly those with SBA, suffer greater morbidity than infants with EX without lethal abnormalities.