Randomized trial of high-frequency oscillatory ventilation versus conventional ventilation: effect on systemic blood flow in very preterm infants

Should SVC flow be a routine measure when performing targeted neonatal echocardiography? A narrative review

Superior vena cava is commonly used in neonatal hemodynamics and is suggested to be the best available non-invasive marker for systemic circulation in preterm infants. Inter- and intra-observer variability remain to be an issue. Its association with neonatal outcomes is has not been established. This is a narrative review about this marker, its use, and its potential pitfalls.

OBJECTIVE

This is a narrative review about SVC flow in preterm infants, physiology, techniques of measurement and its potential association with outcomes.

SOURCES

Literature revie mainly PubMED.

SUMMARY OF THE FINDINGS

SVC flow measurement has some limitations and pitfalls.

CONCLUSIONS

SVC flow association with neonatal outcomes, still needs to be established in further research.

Impact on cerebral hemodynamics of the use of volume guarantee combined with high frequency oscillatory ventilation in a neonatal animal respiratory distress model

High-frequency oscillatory ventilation (HFOV) is an alternative to conventional mechanical ventilation (CMV). Recently, the use of volume guarantee (VG) combined with HFOV has been suggested as a safe strategy capable of reducing the damage induced by ventilation in immature lungs. However, the possible impact of this new ventilation technique on cerebral hemodynamics is unknown. To evaluate the cerebral hemodynamics effect of HFOV combined with VG in an experimental animal model of neonatal respiratory distress syndrome (RDS) due to surfactant deficiency compared with HFOV and CMV+VG (control group). Eighteen newborn piglets were randomized, before and after the induction of RDS by bronchoalveolar lavage, into 3 mechanical ventilation groups: CMV, HFOV and HFOV with VG. Changes in cerebral oxygen transport and consumption and cerebral blood flow were analyzed by non-invasive regional cerebral oxygen saturation (CrSO2), jugular venous saturation (SjO2), the calculated cerebral oxygen extraction fraction (COEF), the calculated cerebral fractional tissue oxygen extraction (cFTOE) and direct measurement of carotid artery flow. To analyze the temporal evolution of these variables, a mixed-effects linear regression model was constructed. After randomization, the following statistically significant results were found in every group: a drop in carotid artery flow: at a rate of -1.7 mL/kg/min (95% CI: -2.5 to -0.81; p < 0.001), CrSO2: at a rate of -6.2% (95% CI: -7.9 to -4.4; p < 0.001) and SjO2: at a rate of -20% (95% CI: -26 to -15; p < 0.001), accompanied by an increase in COEF: at a rate of 20% (95% CI: 15 to 26; p < 0.001) and cFTOE: at a rate of 0.07 (95% CI: 0.05 to 0.08; p < 0.001) in all groups. No statistically significant differences were found between the HFOV groups.

CONCLUSION

No differences were observed at cerebral hemodynamic between respiratory assistance in HFOV with and without VG, being the latter ventilatory strategy equally safe.

WHAT IS KNOWN

• Preterm have a situation of fragility of cerebral perfusion wich means that any mechanical ventilation strategy can have a significant influence. High-frequency oscillatory ventilation (HFOV) is an alternative to conventional mechanical ventilation (CMV). Recently, the use of volume guarantee (VG) combined with HFOV has been suggested as a safe strategy capable of reducing the damage induced by ventilation in immature lungs. Several studies have compared CMV and HFOV and their effects at hemodynamic level. It is known that the use of high mean airway pressure in HFOV can cause an increase in pulmonary vascular resistance with a decrease in thoracic venous return.

WHAT IS NEW

• The possible impact of VAFO + VG on cerebral hemodynamics is unknown. Due the lack of studies and the existing controversy, we have carried out this research project in an experimental animal model with the aim of evaluating the cerebral hemodynamic repercussion of the use of VG in HFOV compared to the classic strategy without VG.

Effect of ventilator modes on neonatal cerebral and peripheral oxygenation using near-infrared spectroscopy

AIM

The effect of ventilator modes on regional tissue oxygenation in premature neonates with respiratory distress syndrome (RDS) has yet to be delineated. Previous studies have looked at global oxygen delivery and have not assessed the effects on regional tissue oxygenation. Our aim in this study was to assess such tissue oxygenation in premature babies with RDS in relation to differing modes of ventilation using near-infrared spectroscopy (NIRS).

METHODS

In 24 stable preterm infants with RDS, undergoing elective wean in ventilator mode, cerebral and muscle tissue oxygenation were assessed using NIRS. Infants were weaned from high-frequency oscillator or jet ventilator to conventional invasive ventilation (CV) or extubated from CV to non-invasive mechanical ventilation. Data at 30 minutes prior and at one hour after change in ventilator mode were compared (paired t test).

RESULTS

In babies changed from high-frequency oscillation to CV, jet to CV and CV to non-invasive ventilation, the differences in cerebral NIRS (mean ± SD) were 1.7 ± 9.9%, 2.3 ± 5.7% and 2.1 ± 8.4%, respectively. The concomitant changes in muscle NIRS were -2.9 ± 8.5%, 8.1 ± 9.7% and 3.6 ± 22.4%, respectively. No changes were statistically significant.

CONCLUSION

Our data suggest that there is no alteration in regional tissue oxygenation related to ventilator mode in stable preterm infants with improving RDS.

Superior vena cava flow: Role, assessment and controversies in the management of perinatal perfusion

The superior vena cava (SVC) is a large vein responsible for the venous return of blood from structures located superior to the diaphragm. The flow in the SVC can be assessed with Doppler ultrasound and can be used as a proxy for cerebral perfusion. Early clinical research studies showed that low SVC flow, particularly if for a prolonged period, was associated with short term morbidity such as intraventricular hemorrhage, mortality, and poorer neurodevelopmental outcomes. However, these findings have not been consistently reported in more recent studies, and the role of SVC flow in early management and as a predictor of poor long-term neurodevelopment has been questioned. This paper provides an overview of SVC assessment, the expected range of findings, and reviews the role of SVC flow as a diagnostic and monitoring tool for the assessment of perinatal perfusion.

A review of superior vena cava flow measurement in the neonate by functional echocardiography

Neonatologists have begun using superior vena cava flow as assessed by functional echocardiography to facilitate real-time decision-making on cardiovascular care. This review aims to describe the basis of the technique, summarise the evidence for its use and compare the technique to existing clinical, biochemical and radiological techniques for assessing neonatal circulatory status.

CONCLUSION

Although echocardiographic measurements of superior vena cava flow, like other measures of perfusion, are not perfect, their noninvasive nature and ability to facilitate real-time decision-making means that at present, they remain the best available methodology of monitoring central perfusion in the neonatal population.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease. A newer form of ventilation called high frequency oscillatory ventilation has been shown in experimental studies to result in less lung injury.

OBJECTIVES

The objective of this review was to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) on the incidence of chronic lung disease (CLD), mortality and other complications associated with prematurity and assisted ventilation in preterm infants who were mechanically ventilated for respiratory distress syndrome (RDS).

SEARCH METHODS

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conference and symposia proceedings; and from expert informants and handsearching of journals by The Cochrane Collaboration, mainly in the English language. The search was updated in January 2009 and again in November 2014.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who required assisted ventilation. Randomisation and commencement of treatment needed to be as soon as possible after the start of CV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the review authors. The standard effect measures were relative risk (RR) and risk difference (RD). From 1/RD the number needed to benefit (NNTB) to produce one outcome was calculated. For all measures of effect, 95% confidence intervals (CIs) were used. For interpretation of subgroup analyses, a P value for subgroup differences as well as the I(2) statistic for between-subgroup heterogeneity were calculated. Meta-analysis was performed using both a fixed-effect and a random-effects model. Where heterogeneity was over 50%, the random-effects model RR was also reported.

MAIN RESULTS

Nineteen eligible studies involving 4096 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 to 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The risk of CLD in survivors at term equivalent gestational age was significantly reduced with the use of HFOV but this effect was inconsistent across studies, even after the meta-analysis was restricted to studies that applied a high lung volume strategy with HFOV. Subgroup analysis by HFOV strategy showed a similar effect in trials with a more strict lung volume recruitment strategy, targeting a very low fraction of inspired oxygen (FiO2), and trials with a less strict lung volume recruitment strategy and with a somewhat higher or unspecified target FiO2. Subgroup analyses by age at randomisation, routine surfactant use or not, type of high frequency ventilator (oscillator versus flow interrupter), inspiratory to expiratory (I:E) ratio of high frequency ventilator (1:1 versus 1:2) and CV strategy (lung protective or not) could not sufficiently explain the heterogeneity. Pulmonary air leaks, defined as gross air leaks or pulmonary interstitial emphysema, occurred more frequently in the HFOV group, whereas the risk of severe retinopathy of prematurity was significantly reduced.Although in some studies an increased risk of severe grade intracranial haemorrhage and periventricular leukomalacia was found, the overall meta-analysis revealed no significant differences in effect between HFOV and CV. The short-term neurological morbidity with HFOV was only found in the subgroup of two trials not using a high volume strategy with HFOV. Most trials did not find a significant difference in long-term neurodevelopmental outcome, although one recent trial showed a significant reduction in the risk of cerebral palsy and poor mental development.

AUTHORS' CONCLUSIONS

There is evidence that the use of elective HFOV compared with CV results in a small reduction in the risk of CLD, but the evidence is weakened by the inconsistency of this effect across trials. Probably many factors, both related to the intervention itself as well as to the individual patient, interact in complex ways. In addition, the benefit could be counteracted by an increased risk of acute air leak. Adverse effects on short-term neurological outcomes have been observed in some studies but these effects are not significant overall. Most trials reporting long-term outcome have not identified any difference.

Transitional hemodynamics in preterm infants with a respiratory management strategy directed at avoidance of mechanical ventilation

BACKGROUND

Early respiratory management of very low birth weight infants has changed over recent years to a practice of early use of CPAP with early selective surfactant administration, and decreased use of mechanical ventilation. One strategy is to use the combination of surfactant and prompt extubation to nasal continuous positive airway pressure (INtubate, SURfactant, Extubate, or INSURE). The aim of this study is to describe blood flow and ductal flow in a prospective cohort during the transitional period when this respiratory management strategy is used.

METHODS

Inborn infants <29week gestation underwent INSURE within 30min of birth using 200mg/kg Curosurf. Blood pressure and blood flow parameters (RVO, LVO, SVC flow, ductus arteriosus) were measured at 6, 24 and 72h of age and information on morbidity was collected.

RESULTS

Sixty-eight infants with a median (range) weight of 940 (450-1380) g were studied. 13 (19%) patients needed mechanical ventilation within 72h of life (INSURE failure). Blood flows and blood pressure were within reported ranges. Eleven (16%) patients had a blood pressure <gestational age and 9 (13%) patients had low blood flow.

CONCLUSION

These data show a low prevalence of low blood pressure and low blood flow in the first 3days after INSURE as compared to cohorts where mechanical ventilation was preferred during transition. We speculate that altered ventilation strategies have helped decrease the incidence of low blood flow and low blood pressure.

Weight corrected percentiles for blood vessel diameters used in flow measurements in preterm infants

BACKGROUND

Blood flow measurements are an integral part of haemodynamic assessment of the newborn infant. Most variability of Doppler derived blood flow is caused by diameter measurements. Population based percentiles of diameter measurements would be useful for training of clinicians undertaking blood flow measurements and allow rapid identification of outliers.

METHODS

Diameter measurements of pulmonary valve annulus, ascending aorta and the superior vena cava using standardised methodology were collected retrospectively from 9 prospective studies on transitional haemodynamics in preterm infants. Data were analysed to calculate weight corrected percentiles of diameters used for blood flow measurements.

RESULTS

We analysed 2870 measurements in 694 preterm infants less than 1750 g. The median gestational age was 27 weeks (range 23 to 34 weeks) and the median time of measurement was 22 h after birth (range 0.5 h to 70 days). 76% of measurements were performed while the infant received mechanical ventilation and 20% received cardiovascular support. Mean diameters increased with weight and standard deviations were comparable over the weight range.

CONCLUSION

Data from this large combined series provide a reference range for blood vessel diameters in the population most often measured. The data permits recognition of outliers and could be used to trigger review of measurements that fall outside the normal range.

The diagnostic value of a single measurement of superior vena cava flow in the first 24 h of life in very preterm infants

Low superior vena cava (SVC) flow has been associated with intraventricular haemorrhage (IVH) in very preterm infants. We studied the diagnostic value of a single measurement of SVC flow within the first 24 h of life in very preterm infants and its association with occurrence or extension of IVH in a setting of limited availability of neonatal echocardiography. Preterm infants who were born at less than 30 weeks gestation and who had an echocardiogram within 24 h after birth were eligible. Baseline, clinical and ultrasound data were collected. A total of 165 preterm infants were included. Low SVC flow (<41 ml/kg/min) occurred in six infants and was associated with severe IVH and extension of IVH, although this was not significant after adjusting for confounders. The only independently associated variable with low SVC flow was admission temperature (odds ratio 0.27, p = 0.001). A review of SVC flow values shows that these are higher now than initially reported. This study does not show an association of low SVC flow and severe IVH or extension of IVH after adjusting for confounders as a single measurement of SVC flow did not add any diagnostic value in this cohort. Thus, the exact role of SVC flow measurements in the circulatory assessment of preterm infants remains to be elucidated. However, admission temperature may have an effect on systemic blood flow in very preterm infants.

Elective high-frequency oscillatory versus conventional ventilation in preterm infants: a systematic review and meta-analysis of individual patients' data

BACKGROUND

Population and study design heterogeneity has confounded previous meta-analyses, leading to uncertainty about effectiveness and safety of elective high-frequency oscillatory ventilation (HFOV) in preterm infants. We assessed effectiveness of elective HFOV versus conventional ventilation in this group.

METHODS

We did a systematic review and meta-analysis of individual patients' data from 3229 participants in ten randomised controlled trials, with the primary outcomes of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age, death or severe adverse neurological event, or any of these outcomes.

FINDINGS

For infants ventilated with HFOV, the relative risk of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age was 0.95 (95% CI 0.88-1.03), of death or severe adverse neurological event 1.00 (0.88-1.13), or any of these outcomes 0.98 (0.91-1.05). No subgroup of infants (eg, gestational age, birthweight for gestation, initial lung disease severity, or exposure to antenatal corticosteroids) benefited more or less from HFOV. Ventilator type or ventilation strategy did not change the overall treatment effect.

INTERPRETATION

HFOV seems equally effective to conventional ventilation in preterm infants. Our results do not support selection of preterm infants for HFOV on the basis of gestational age, birthweight for gestation, initial lung disease severity, or exposure to antenatal corticosteroids.

FUNDING

Nestlé Belgium, Belgian Red Cross, and Dräger International.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease (CLD). A newer form of ventilation called high frequency oscillatory ventilation (HFOV) has been shown to result in less lung injury in experimental studies.

OBJECTIVES

The objective of this review is to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) on the incidence of chronic lung disease, mortality and other complications associated with prematurity and assisted ventilation in preterm infants who are mechanically ventilated for respiratory distress syndrome (RDS).

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching by the Cochrane Collaboration, mainly in the English language. The search was updated in January 2009.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who required assisted ventilation. Randomisation and commencement of treatment needed to be as soon as possible after the start of CV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the various authors. The standard effect measures are relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) to produce one outcome were calculated. For all measures of effect, 95% confidence intervals were used. In subgroup analyses the 99% CIs are also given for summary RRs in the text. Meta-analysis was performed using a fixed effects model. Where heterogeneity was over 50%, the random effects RR is also given.

MAIN RESULTS

Seventeen eligible studies of 3,652 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 - 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The effect of HFOV on CLD in survivors at term equivalent gestational age was inconsistent across studies and the reduction was of borderline significance overall. The effect was similar in trials with a high lung volume strategy for HFOV targeting at very low FiO(2) and trials with a high lung volume strategy with somewhat higher or unspecified target FiO(2). Subgroups of trials showed a significant reduction in CLD with HFOV when no surfactant was used, when piston oscillators were used for HFOV, when lung protective strategies for CV were not used, when randomisation occurred at two to six hours of age, and when inspiratory:expiratory ratio of 1:2 was used for HFOV. In the meta-analysis of all trials, pulmonary air leaks occurred more frequently in the HFOV group.In some studies, short-term neurological morbidity with HFOV was found, but this effect was not statistically significant overall. The subgroup of two trials not using a high volume strategy with HFOV found increased rates of Grade 3 or 4 intraventricular haemorrhage and of periventricular leukomalacia. An adverse effect of HFOV on long-term neurodevelopment was found in one large trial but not in the five other trials that reported this outcome. The rate of retinopathy of prematurity is reduced overall in the HFOV group.

AUTHORS' CONCLUSIONS

There is no clear evidence that elective HFOV offers important advantages over CV when used as the initial ventilation strategy to treat preterm infants with acute pulmonary dysfunction. There may be a small reduction in the rate of CLD with HFOV use, but the evidence is weakened by the inconsistency of this effect across trials and the overall borderline significance. Future trials on elective HFOV should target those infants who are at most risk of CLD (extremely preterm infants), compare different strategies for generating HFOV and CV, and report important long-term neurodevelopmental outcomes.

Effect of lung recruitment on pulmonary, systemic, and ductal blood flow in preterm infants

OBJECTIVE

To determine the effect of lung recruitment on pulmonary, systemic, and ductal blood flow in preterm infants treated with primary high-frequency ventilation (HFV).

STUDY DESIGN

Thirty-four infants (median gestational age, 28 weeks) were included in this prospective cohort study. Changes in oxygenation in response to stepwise changes in the continuous distending pressure (CDP) were used to monitor lung recruitment during HFV. For each individual patient, the opening pressure (CDPo), closing pressure (CDPc), and optimal pressure (CDPopt) were determined. Ultrasound measurements of right ventricular output (RVO), superior vena cava (SVC), and ductus arteriosus (DA) flow were performed at the start of recruitment (CDPs), CDPo, and CDPopt.

RESULTS

Increasing the CDP from 8 (CDPs) to 20 (CDPo) cmH(2)O resulted in a decreased RVO (mean difference, -17%; 95% CI, -24, -10%) and unchanged SVC flow and ductal shunting. Transient low RVO and SVC flow values at CDPo were seen in 3 and 2 infants, respectively.

CONCLUSIONS

Lung recruitment during HFV in preterm infants does not appear to result in clinically relevant changes in pulmonary, systemic, and ductal blood flow.

Cardiovascular and pulmonary consequences of airway recruitment in preterm lambs

Increases in positive end-expiratory pressure (PEEP) improve arterial oxygenation in preterm infants, but the effects on cardiopulmonary hemodynamics are understood poorly. We aimed to determine the effect of increased PEEP on cardiopulmonary hemodynamics and to compare measurements from indwelling flow probes with Doppler echocardiography. Preterm lambs (129 ± 1 days) were ventilated initially with a tidal volume of 7 ml/kg and 4 cmH2O of PEEP. In ramp lambs ( n = 7), PEEP was increased by 2-cmH2O increments to 10 cmH2O and then in decrements back to 4 cmH2O. PEEP was unchanged in controls ( n = 6). Doppler echocardiographic flow measurements in the left pulmonary artery (LPA) and ductus arteriosus (DA) were correlated with flow probe measurements. Compared with controls, high PEEP reduced LPA flow from baseline (10-cmH2O PEEP: 43 ± 8% vs. control: 83 ± 21%; P = 0.029). High PEEP increased the proportion of right-to-left (R-L) shunting through the DA, with a trend to an increased oxygenation index compared with controls (oxygenation index: 44.5 ± 13.5 at 10-cmH2O PEEP vs. 19.4 ± 4.5 in controls; P = 0.07). Increasing PEEP decreased heart rate (17 beats/min; P = 0.03) and tended to lower systolic arterial pressure (5.0 mmHg; P = 0.052) compared with controls. Doppler echocardiography measurement of LPA flows correlated strongly with indwelling flow probe ( r2 = 0.73, P < 0.001), except during highly turbulent flows. Increases in PEEP have significant cardiopulmonary consequences in preterm lambs, including reduced LPA flow and increased R-L shunt through the DA. These changes are likely due to the concomitant increase in downstream pulmonary vascular resistance and increased cardiovascular constraint induced by PEEP.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease (CLD). Conventional IPPV is provided at 30-80 breaths per minute, while a newer form of ventilation called high frequency oscillatory ventilation (HFOV) provides 'breaths' at 10 - 15 cycles per second. This has been shown to result in less lung injury in experimental studies.

OBJECTIVES

The objective of this review is to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) in preterm infants who are mechanically ventilated for respiratory distress syndrome (RDS), on the incidence of chronic lung disease, mortality and other complications associated with prematurity and assisted ventilation.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching by the Cochrane Collaboration, mainly in the English language. The search was updated in April 2007.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who were given IPPV. Randomisation and commencement of treatment needed to be as soon as possible after the start of IPPV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the various authors. The standard effect measures are relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) to produce one outcome were calculated. For all measures of effect, 95% confidence intervals were used. In subgroup analyses the 99% CIs are also given for summary RRs in the text. Meta-analysis was performed using a fixed effects model. Where heterogeneity was over 50%, the random effects RR is also given.

MAIN RESULTS

Fifteen eligible studies of 3,585 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 - 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The effect of HFOV on CLD in survivors at term equivalent gestational age was inconsistent across studies and the reduction was of borderline significance overall. Subgroups of trials showed a significant reduction in CLD with HFOV when high volume strategy for HFOV was used, when piston oscillators were used for HFOV, when lung protective strategies for CV were not used, when randomisation occurred at two to six hours of age, and when inspiratory:expiratory ratio of 1:2 was used for HFOV. In the meta-analysis of all trials, pulmonary air leaks occurred more frequently in the HFOV group. In some studies, short-term neurological morbidity with HFOV was found, but this effect was not statistically significant overall. The subgroup of two trials not using a high volume strategy with HFOV found increased rates of Grade 3 or 4 intraventricular haemorrhage and of periventricular leukomalacia. An adverse effect of HFOV on long-term neurodevelopment was found in one large trial but not in the five other trials that reported this outcome. The rate of retinopathy of prematurity is reduced overall in the HFOV group.

AUTHORS' CONCLUSIONS

There is no clear evidence that elective HFOV offers important advantages over CV when used as the initial ventilation strategy to treat preterm infants with acute pulmonary dysfunction. There may be a small reduction in the rate of CLD with HFOV use, but the evidence is weakened by the inconsistency of this effect across trials and the overall borderline significance. Future trials on elective HFOV should target those infants who are at most risk of CLD (extremely preterm infants), compare different strategies for generating HFOV and CV, and report important long-term neurodevelopmental outcomes.

Lung Recruitment Using Oxygenation during Open Lung High-Frequency Ventilation in Preterm Infants

RATIONALE

Changes in oxygenation are often used to guide the recruitment procedure during open lung high-frequency ventilation in preterm infants. However, data on the feasibility and safety of this approach in daily clinical practice are limited.

OBJECTIVE

To prospectively collect data on ventilator settings, gas exchange, and circulatory parameters before and after surfactant therapy during open lung high-frequency ventilation.

METHODS

In 103 preterm infants with respiratory distress syndrome, the opening, closing, and optimal pressures were determined during high-frequency ventilation by increasing and decreasing stepwise the continuous distending pressure, defining optimal recruitment as adequate oxygenation using a fraction of inspired oxygen not exceeding 0.25. This procedure was repeated after each surfactant treatment.

MEASUREMENTS AND MAIN RESULTS

The mean presurfactant opening and optimal continuous distending pressures were, respectively, 20.5 +/- 4.3 and 14.0 +/- 4.0 cm H2O, with a fraction of inspired oxygen of 0.24 +/- 0.04. Surfactant treatment enabled a reduction in the mean optimal pressure of almost 6 cm H2O without compromising oxygenation. Blood pressure and heart rate remained stable and no air leaks were observed during the recruitment procedures. The mortality rate and the incidence of severe intracranial hemorrhage or periventricular leukomalacia and chronic lung disease at 36 wk were comparable to previously reported data.

CONCLUSION

Open lung high-frequency ventilation using oxygenation to guide the recruitment process is feasible and safe in preterm infants and enables a reduction of the fraction of inspired oxygen below 0.25 in the majority of preterm infants with respiratory distress syndrome.

Chorioamnionitis with or without funisitis increases the risk of hypotension in very low birthweight infants on the first postnatal day but not later

OBJECTIVE

To evaluate the relation between chorioamnionitis and hypotension in very low birthweight infants.

METHODS

Retrospective cohort study in infants with a birth weight of <1500 g born between January 2002 and September 2004. The placentas were examined for evidence of chorioamnionitis and funisitis. Hypotension was defined by the use of vasopressors.

RESULTS

Of 105 infants, 37 (35%) were chorioamnionitis positive. The onset of hypotension had a skewed distribution: day 1 for 30 episodes and scattered from day 2 to day 19 for the remaining 22. Of the 30 infants who developed hypotension on day 1, 17 (57%) were chorioamnionitis positive. The mean maturity of the chorioamnionitis positive group was 27.91 weeks, marginally less than the mean maturity of 29.05 weeks of the chorioamnionitis negative group (p = 0.05). After adjustment of the effects for confounding variables (birth weight, gestation, surfactant therapy, mechanical ventilation on day 1, high frequency oscillatory ventilation, patent ductus arteriosus), chorioamnionitis was the significant factor in line with hypotension developing on day 1 (adjusted odds ratio 5.14, 95% confidence interval 1.51 to 17.50). There was no evidence that hypotension developing after day 1 was associated with chorioamnionitis.

CONCLUSIONS

There is a strong association between chorioamnionitis and hypotension developing on day 1 in very low birthweight infants.