Meta-analysis of elective high frequency ventilation in preterm infants with respiratory distress syndrome

Mechanical ventilation in special populations

Optimal respiratory support can only be achieved if the ventilator strategy utilized for each individual patient at any given point in the evolution of their disease process is tailored to the underlying pathophysiology. The critically ill newborn infant requires individualized patient care when it comes to mechanical ventilation. This can only occur if the clinician has a good understanding of the different pathophysiologies of a variety of conditions that can lead to respiratory failure. In this chapter we describe the key pathophysiological features of bronchopulmonary dysplasia, meconium aspiration syndrome and lung hypoplasia syndromes with emphasis on congenital diaphragmatic hernia. We review available evidence to guide management an provide specific recommendations for pathophysiologically-based mechanical ventilation support.

Elective high-frequency oscillatory ventilation in preterm infants with respiratory distress syndrome: an individual patient data meta-analysis

Background

Despite the considerable amount of evidence from randomized controlled trials and meta-analyses, uncertainty remains regarding the efficacy and safety of high-frequency oscillatory ventilation as compared to conventional ventilation in the early treatment of respiratory distress syndrome in preterm infants. This results in a wide variation in the clinical use of high-frequency oscillatory ventilation for this indication throughout the world. The reasons are an unexplained heterogeneity between trial results and a number of unanswered, clinically important questions. Do infants with different risk profiles respond differently to high-frequency oscillatory ventilation? How does the ventilation strategy affect outcomes? Does the delay – either from birth or from the moment of intubation – to the start of high-frequency oscillation modify the effect of the intervention? Instead of doing new trials, those questions can be addressed by re-analyzing the individual patient data from the existing randomized controlled trials.

Methods/Design

A systematic review with meta-analysis based on individual patient data. This involves the central collection, validation and re-analysis of the original individual data from each infant included in each randomized controlled trial addressing this question.

The study objective is to estimate the effect of high-frequency oscillatory ventilation on the risk for the combined outcome of death or bronchopulmonary dysplasia or a severe adverse neurological event. In addition, it will explore whether the effect of high-frequency oscillatory ventilation differs by the infant's risk profile, defined by gestational age, intrauterine growth restriction, severity of lung disease at birth and whether or not corticosteroids were given to the mother prior to delivery. Finally, it will explore the importance of effect modifying factors such as the ventilator device, ventilation strategy and the delay to the start of high-frequency ventilation.

Discussion

An international collaborative group, the PreVILIG Collaboration (Prevention of Ventilator Induced Lung Injury Group), has been formed with the investigators of the original randomized trials to conduct this systematic review. In the field of neonatology, individual patient data meta-analysis has not been used previously. Final results are expected to be available by the end of 2009.

Continuous negative extrathoracic pressure combined with high-frequency oscillation improves oxygenation with less impact on blood pressure than high-frequency oscillation alone in a rabbit model of surfactant depletion

Background

Negative air pressure ventilation has been used to maintain adequate functional residual capacity in patients with chronic muscular disease and to decrease transpulmonary pressure and improve cardiac output during right heart surgery. High-frequency oscillation (HFO) exerts beneficial effects on gas exchange in neonates with acute respiratory failure. We examined whether continuous negative extrathoracic pressure (CNEP) combined with HFO would be effective for treating acute respiratory failure in an animal model.

Methods

The effects of CNEP combined with HFO on pulmonary gas exchange and circulation were examined in a surfactant-depleted rabbit model. After induction of severe lung injury by repeated saline lung lavage, 18 adult white Japanese rabbits were randomly assigned to 3 groups: Group 1, CNEP (extra thoracic negative pressure, -10 cmH₂O) with HFO (mean airway pressure (MAP), 10 cmH₂O); Group 2, HFO (MAP, 10 cmH₂O); and Group 3, HFO (MAP, 15 cmH₂O). Physiological and blood gas data were compared among groups using analysis of variance.

Results

Group 1 showed significantly higher oxygenation than Group 2, and the same oxygenation with significantly higher mean blood pressure compared to Group 3.

Conclusion

Adequate CNEP combined with HFO improves oxygenation with less impact on blood pressure than high-frequency oscillation alone in an animal model of respiratory failure.

Periventricular hemorrhagic infarction: risk factors and neonatal outcome

The aim of this study was to define the incidence, clinical associations, and short-term outcome of periventricular hemorrhagic infarction in the modern neonatal intensive care unit. From 5774 infants (birth weight<2500 gm), periventricular hemorrhagic infarction diagnosed by cranial ultrasound was identified and confirmed. gestational age-matched control infants were identified with normal cranial ultrasounds and detailed clinical data were obtained in both groups. Periventricular hemorrhagic infarction was confirmed in 58 infants. Incidence was 0.1% (1500-2500 gm), 2.2% (750-1500 gm), and 10% (<750 gm). Data across 6 study years reveal increased incidence in infants<750 gm. Compared with control infants, infants with periventricular hemorrhagic infarction had significantly greater association with assisted conception, intrapartum factors (emergency cesarean section, low Apgar scores), early neonatal complications (patent ductus arteriosus, pneumothorax, pulmonary hemorrhage), blood gas disturbances, and need for pressor, volume infusion, and respiratory support. Neonatal mortality of this group was 40% (n=23). Survivors had longer duration of mechanical ventilation and critical care stay compared with control subjects. Thirty-seven percent of survivors required cerebrospinal fluid shunt placement. Periventricular hemorrhagic infarction remains an important neurologic complication of prematurity. A growing population of survivors is apparent among infants with birth weight<750 gm. Multiple hemodynamic factors associated with periventricular hemorrhagic infarction cluster in the intrapartum and early neonatal periods.

Ventilation strategies and outcome in randomised trials of high frequency ventilation

OBJECTIVE

Randomised controlled trials comparing elective use of high frequency ventilation (HFV) with conventional mechanical ventilation (CMV) in preterm infants have yielded conflicting results. We hypothesised that the variability of results may be explained by differences in study design, ventilation strategies, delay in initiation of HFV, and use of permissive hypercapnia.

METHODS

Randomised controlled trials comparing the elective use of HFV with any form of CMV were identified. Trials were classified according to the ventilation strategies used for HFV and CMV and oscillator device employed. For cumulative meta-analyses, trials were arranged by the following covariables: mean duration until randomisation, Paco(2) limits, publication date, and sample size. Odds ratios (OR) and 95% confidence intervals were calculated using fixed and random effects models.

RESULTS

Seventeen randomised trials enrolling 3776 patients were included. Unlike previous meta-analyses, there was no significant difference in the incidence of bronchopulmonary dysplasia or death (OR 0.87, 0.75-1.00) and severe intraventricular haemorrhage grade 3-4 (1.14, 0.96-1.37). The incidence of air leaks (OR 1.23, 1.06-1.44) was significantly increased with HFV. Subgroup analyses and cumulative meta-analyses demonstrated that trial results were related to the ventilation strategies used for HFV and CMV. No influence was found for mean time to randomisation, degree of permissive hypercapnia, or sample size.

CONCLUSIONS

Heterogeneity among trials of elective HFV compared to CMV in preterm infants is mainly due to differences in ventilatory strategies. Optimising CMV strategy appeared to be as effective as using HFV in improving pulmonary outcome in preterm infants.

Partial liquid ventilation with low-dose perfluorochemical and high-frequency oscillation improves oxygenation and lung compliance in a rabbit model of surfactant depletion

BACKGROUND

Partial liquid ventilation (PLV) with perfluorochemical (PFC) has been advocated as a new therapy for acute respiratory distress syndrome in both clinical and animal studies, meconium aspiration syndrome, and RDS. PFC is referred to as liquid PEEP because it gets distributed to the most gravity-dependent regions of the lung due to its density. High-frequency oscillation (HFO) has been shown to prevent both acute and chronic lung injury in the management of very low birth weight infants with RDS, with gentle ventilation approach. Specifically, HFO with aggressive and adequate lung volume recruitment has been shown to reduce the incidence of chronic lung disease in very low birth weight infants. We hypothesized that PLV along with HFO might be effective in ARDS in an adult rabbit model.

OBJECTIVES

To examine the efficiency of low-dose PLV with with HFO on pulmonary gas exchange and lung compliance in a surfactant-depleted rabbit model.

METHODS

After induction of severe lung injury by repeated saline lung lavage, 19 adult white Japanese rabbits were randomized into two groups that received PLV with HFO (n=9) or HFO gas ventilation (n=10). Physiological and blood gas data were compared between the two groups by analysis of variance.

RESULTS

The HFO-PLV group showed improved total lung compliance with maintenance of significantly lower mean airway pressure as compared with the HFO-GAS group so as to keep SpO2>90%.

CONCLUSIONS

The addition of a low dose of PFC with HFO was effective in achieving adequate oxygenation, with a reduction in further lung injury in neonates.

Intraventricular hemorrhage in the premature neonate

Intraventricular hemorrhage in the premature neonate has been and continues to be a cause of morbidity and mortality in NICUs around the globe. Much information is available concerning the etiology and preventative and treatment strategies to reduce the incidence of IVH in this patient population. As neonatal caregivers are struggling to care for and protect infants who are surviving despite extreme prematurity, this survival is complicated by the infant's cerebral vasculature, which is very susceptible to hemorrhage; by respiratory problems that require the use of lifesaving, but potentially harmful, ventilation interventions; and by the infant's compromised ability to self-regulate vascular responses to stress. The preventative treatments being explored and proposed may come with debilitating and potentially lethal sequelae. Research continues, however. New recommendations are being proffered, and perhaps, in the near future, the incidence of IVH and its associated morbidity and mortality will decline dramatically.

Tracheal gas insufflation as a lung-protective strategy: physiologic, histologic, and biochemical markers

OBJECTIVE

Conventional mechanical ventilation in acute lung failure potentiates lung injury, which can be assessed by physiologic, histologic, and biochemical markers. Thus, new ventilation strategies are directed at reducing lung injury. Tracheal gas insufflation has been shown to reduce endotracheal tube prosthetic deadspace and peak inspiratory pressure during conventional mechanical ventilation. Our objective was to use physiologic, histologic, and biochemical markers to test the hypothesis that tracheal gas insufflation in acute lung injury is lung protective.

DESIGN

Animal experiment.

SETTING

University setting.

SUBJECTS

Juvenile rabbits (n = 12; 1.95 +/- 0.1 SE kg).

INTERVENTIONS

Rabbits were anesthetized, instrumented, paralyzed, and ventilated with Fio(2) = 1.0. Lung injury was induced with repeated saline lavage (10 mL/kg per lavage until Pao(2) </=150 mm Hg and compliance </=0.50 mL/cm H(2)O/kg for 30 mins). Animals were randomized to conventional mechanical ventilation with and without 0.5 lpm of continuous tracheal gas insufflation (Vygon endotracheal tube) for 4 hrs to maintain Paco(2) at 45-55 mm Hg by adjusting the peak inspiratory pressure; other conventional mechanical ventilation settings remained constant.

MEASUREMENTS AND MAIN RESULTS

Gas exchange and pulmonary mechanics were measured every 30 mins; plasma and pulmonary tissue were taken for cytokine and histologic evaluation after 4 hrs. Peak inspiratory pressure, tidal volume, and physiologic deadspace were significantly less (p < .05) in the tracheal gas insufflation animals when compared with conventional mechanical ventilation animals. Pao(2), positive end-expiratory pressure, mean airway pressure, vital signs, Paco(2), and respiratory resistance and compliance were not statistically different between the two groups. There was a difference (p < .05) in interleukin-8 tissue (pg/mug protein; dependent = 52.4 +/- 7.6 vs. nondependent = 32.8 +/- 4.2) and plasma levels (pg/mL; preinjury = 7.2 +/- 2.3 vs. postinjury = 118 +/- 58). Histology showed a trend toward protection of alveolar structures for tracheal gas insufflation.

CONCLUSIONS

Tracheal gas insufflation resulted in lower ventilatory requirements (peak inspiratory pressure, tidal volume, and deadspace) and a more favorable histologic trend than conventional mechanical ventilation. Tracheal gas insufflation offers potential as a lung-protective strategy for acute lung injury in the developing rabbit lung and may be a useful clinical adjunct to neonatal respiratory management.

Effect of air and heliox as carrier gas on CO2 transport in a model of high-frequency oscillation comparing two oscillators

OBJECTIVE

To study the effect of carrier gas on CO(2) transport during high-frequency oscillatory ventilation in a closed model.

DESIGN

In vitro model study.

SETTING

Respiratory research laboratory affiliated with a tertiary center for pediatric critical care.

SUBJECT

In vitro, closed-lung model consisting of a glass tube (9.8 x 1000 mm) covered at each end with balloons.

INTERVENTION

Air or heliox (80:20) at constant pressure was oscillated inside the model, comparing the Sensormedics 3100A and Hummingbird BMO-20N oscillators at equal amplitude.

MEASUREMENTS AND MAIN RESULTS

Tracer gas (CO(2)) was injected at one end of the model, and CO(2) concentration was measured at the opposite end. Speed of CO(2) transport was expressed as the time for the CO(2) concentration to reach 63% of the final concentration (the time constant). In room air, using the Hummingbird oscillator and increasing frequency stepwise from 5 to 20 Hz, the time constant decreased from 2813 to 457 secs (p =.05). Using the Sensormedics oscillator in room air at increasing frequency from 5 to 15 Hz, the time constant decreased from 1584 to 551 secs (p =.05). In heliox, using the Hummingbird oscillator, the speed of CO(2) transport increased by 85% (p =.029) at 5 Hz and by 28% (p =.05) at 15 Hz. With the Sensormedics oscillator using heliox, the speed of CO(2) transport increased by 16% at 5 Hz (p =.009) and 52% at 15 Hz (p =.008). Proportionally, the increase in CO(2) transport with heliox was greater at 5 Hz for the Hummingbird oscillator and at 15 Hz for the Sensormedics oscillator.

CONCLUSIONS

In a closed model, we showed that during high-frequency oscillatory ventilation in room air, CO(2) transport increases with increasing frequency for both ventilators. Using heliox as carrier gas significantly augmented CO(2) transport, but the increase is frequency and device dependent. The effect of heliox on oscillator performance and the clinical applicability of our findings require further study.

Risk factors for intraventricular hemorrhage in very low birth weight premature infants: a retrospective case-control study

OBJECTIVE

High-grade intraventricular hemorrhage (IVH) is an important cause of severe cognitive and motor neurologic impairment in very low birth weight infants and is associated with a high mortality rate. The risk of IVH is inversely related to gestational age and birth weight. Previous studies have proposed a number of risk factors for IVH; however, lack of adequate matching for gestational age and birth weight may have confounded the results. The purpose of this study was to identify variables that affect the risk of high-grade IVH, using a retrospective and case-control clinical study.

METHODS

From a cohort of 641 consecutive preterm infants with a birth weight of <1500 g, 36 infants with IVH grade 3 and/or 4 were identified. A control group of 69 infants, closely matched for gestational age and birth weight, was selected. Maternal factors, labor and delivery characteristics, and neonatal parameters were collected in both groups. Results of cranial ultrasound examinations, whether routine or performed in presence of clinical suspicion, were also collected. Univariate analysis and multivariate logistic regression analysis were performed.

RESULTS

High fraction of inspired oxygen in the first 24 hours, pneumothorax, fertility treatment (mostly IVF), and early sepsis were associated with an increased risk of IVH. A higher number of suctioning procedures, a higher first hematocrit, and a relatively low arterial pressure of carbon dioxide during the first 24 hours of life were associated with a lower occurrence. In the multivariate logistic regression model, early sepsis (odds ratio [OR]: 8.19; 95% confidence interval [CI]: 1.55-43.1) and fertility treatment (OR: 4.34; 95% CI: 1.42-13.3) were associated with a greater risk of high-grade IVH, whereas for every dose of antenatal steroid treatment there was a lower risk of high-grade IVH (OR: 0.52; 95% CI: 0.30-0.90) and each decrease in a mmHg unit of arterial pressure of carbon dioxide during the first 24 hours was associated with a lower risk of IVH (OR: 0.91; 95% CI: 0.83-0.98). This multivariate model had a sensitivity of 77%, a specificity of 75%, and a positive predictive value of 76%. The area under the curve derived from the receiver operator characteristic plots is 0.82.

CONCLUSIONS

Our results confirm that the development of IVH is associated with early sepsis and failure to give antenatal steroid treatment. We propose that fertility treatment (and especially IVF) may be a new risk factor, and more research is needed to assess its role.

Early use of high frequency ventilation in the premature neonate

This study evaluated whether the early use of high frequency ventilation (HFV) decreased the incidence of oxygen dependency at 36 weeks postconceptual age [chronic lung disease (CLD)] and improved developmental outcome. Neonates of less than 32 weeks gestational age needing ventilatory support for RDS who were admitted to a tertiary academic neonatal intensive care unit (NICU) within 6 h of birth were included in a prospective controlled clinical trial. With randomisation they were given either HFV (n=147) or conventional ventilation (CV) (n=153). As a primary outcome variable, ventilator and/or oxygen dependence at a postconceptual age of 36 weeks (CLD) was measured. Secondary outcome variables were: mortality at discharge, treatment failure, ventilator and/or oxygen dependence at 28-30 days (bronchopulmonary disease [BPD]), duration of ventilation, use of surfactant, days in oxygen and on continuous positive airway pressure (CPAP), survival without BPD or CLD, air leak, intracranial haemorrhages (ICH) grades 3 and 4, periventricular leukomalacia (PVL) grades 1 and 2, retinopathy of prematurity (ROP), patent ductus arteriosus (PDA), necrotising enterocolitis (NEC), developmental outcome at 7 to 12 months and if necessary at 18-24 months corrected age. The results showed that CLD (16.3 vs. 12.4%), BPD (33.3 vs. 36.6%), early cerebral abnormalities, mortality at discharge (17.2 vs. 13.2%), failure rate (11.6 vs. 6.5%) and motor and mental developmental outcome at a corrected age of 18 to 24 months (p>0.05) did not differ between the two groups.

CONCLUSION

Under the present study design HFV compared with CV did not decrease chronic lung disease and no developmental outcome differences could be found at a corrected age of almost 2 years.

Neonatal high-frequency ventilation. Past, present, and future

High-frequency ventilation has become established as an effective treatment modality in a variety of clinical situations. The laboratory and clinical investigations of these techniques have contributed tremendously to our understanding of the pathophysiology of respiratory failure and the important concept of maintaining adequate lung volume. Clinicians have come to appreciate better the factors involved in lung injury and the potential for damage to distant organs. The place of HFV in the therapeutic armamentarium will undoubtedly continue to evolve in the years to come. Of particular interest is the advent of advanced modes of fully synchronized and volume-targeted conventional mechanical ventilatory modes, along with the trend to use smaller tidal volumes and higher levels of PEEP with conventional ventilation. With these developments there seems to be a certain convergence of HFV and tidal ventilation that is the logical result of our improved understanding of respiratory pathophysiology. The available controlled trials of HFV versus tidal ventilation do not clearly differentiate whether improved outcomes are the result of HFV per se, or a reflection of the effects of optimizing lung volume, a benefit that may not be unique to HFV.

Recent advances in intubation and mechanical ventilation

The ideal care of the critically ill infant or child should demonstrate a seamless service starting with recognition of potential critical illness and initiation of early resuscitative interventions, escalating to advanced life support and skilled transfer to an appropriate location where intensive care can be continued. This article discusses advances in the package of respiratory care commencing with the decision to provide respiratory support, which includes the decision whether or not to intubate, leading to the choice of mechanical ventilatory support mode in the critically ill child. Indications for intubation include protection of the airway, airway toilet and the need for positive pressure support. Respiratory support may not always require additional airway protection or airway toilet. Non-invasive respiratory support includes continuous positive airway pressure, biphasic positive airway pressure, or negative extrathoracic pressure. Recent advances in understanding and management of acute lung injury, such as appropriate use of positive end-expiratory airway pressure, alveolar recruitment manoeuvres, high frequency ventilation and use of inhaled nitric oxide, will be discussed in the light of recent randomised controlled trials providing evidence of benefit.

Prospective randomized multicenter comparison of high-frequency oscillatory ventilation and conventional ventilation in preterm infants of less than 30 weeks with respiratory distress syndrome

BACKGROUND

Early use of high-frequency ventilation and exogenous surfactant is proposed as the optimal mode of ventilatory support in infants with respiratory distress syndrome. In very premature infants, we tested the hypothesis that high-frequency versus conventional ventilation could decrease exogenous surfactant requirements and improve pulmonary outcome, without altering the complication rate, including that of severe intraventricular hemorrhage.

METHODS

Preterm infants with a postmenstrual age of 24 to 29 weeks, presenting with respiratory distress syndrome were randomly assigned to high-frequency oscillatory ventilation (lung volume recruitment strategy) or conventional ventilation.

RESULTS

Two hundred seventy-three infants were enrolled. One hundred fifty-three had a postmenstrual age of 24 to 27 weeks, and 143 had a birth weight </=1000 g. One hundred thirty-four infants were randomized at 142 minutes of life (median) to receive conventional ventilation (mean postmenstrual age at birth: 27. 6 +/- 1.5 weeks; mean birth weight: 997 +/- 245 g); and 139 infants were randomized at 145 minutes of life to receive high-frequency ventilation (mean postmenstrual age at birth: 27.5 +/- 1.4 weeks; mean birth weight: 976 +/- 219 g). High-frequency ventilation, compared with conventional ventilation, was associated with a twofold reduction in the requirement for >/=2 instillations of exogenous surfactant (30% vs 62%; odds ratio:.27; 95% confidence interval:.16-.44) and no difference in pulmonary outcome. The incidence of severe intraventricular hemorrhage was 24% in the high-frequency group and 14% in the conventional ventilation group (adjusted odds ratio: 1.50; 95% confidence interval:.68-3.30).

CONCLUSION

Early use of high-frequency oscillatory ventilation in very premature infants decreases exogenous surfactant requirements, does not improve the pulmonary outcome, and may be associated with an increased incidence of severe intraventricular hemorrhage.

[Jargon of the neonatal intensive care unit]

Jargon, the specialized vocabulary and idioms, is frequently used by people of the same work or profession. The neonatal intensive care unit (NICU) makes no exception to this. As a matter of fact, NICU is one place where jargon is constantly developing in parallel with the evolution of techniques and treatments. The use of jargon within the NICU is very practical for those who work in these units. However, this jargon is frequently used by neonatologists in medical reports or other kinds of communication with unspecialized physicians. Even if part of the specialized vocabulary can be decoded by physicians not working in the NICU, they do not always know the exact place that these techniques or treatments have in the management of their patients. The aim of this article is to describe the most frequent jargon terms used in the French NICU and to give up-to-date information on the importance of the techniques or treatments that they describe.

Strategies for prevention of neonatal chronic lung disease

Chronic lung disease (CLD) of prematurity remains a substantial problem despite modern perinatal and neonatal care. CLD remains related to gestational age and lung immaturity, although it has become clear that severe initial lung disease is not a prerequisite for CLD to develop. Attempts to prevent CLD to date have not adequately addressed the multifactorial nature of the complex pathophysiology that leads to CLD. Thus, results have been modest at best. Prevention of CLD will require a multifaceted approach with specific interventions and care practices focused on different aspects of the pathway that leads to CLD. This review considers new information related to causation of CLD and the magnitude of the effect of prevention strategies tested to date. This article also advances the hypothesis that CLD is preventable with a global strategy of minimizing inciting events, optimizing management, and specific therapies aimed at intrinsic vulnerabilities.

Continuous tracheal gas insufflation in preterm infants with hyaline membrane disease. A prospective randomized trial

In mechanically ventilated neonates, the instrumental dead space is a major determinant of total minute ventilation. By flushing this dead space, continuous tracheal gas insufflation (CTGI) may allow reduction of the risk of overinflation. We conducted a randomized trial to evaluate the efficacy of CTGI in reducing airway pressure over the entire period of mechanical ventilation while maintaining oxygenation. A total of 34 preterm newborns, ventilated in conventional pressure-limited mode, were enrolled in two study arms, to receive or not receive CTGI. Transcutaneous Pa(CO(2)) (tcPa(CO(2))) was maintained at 40 to 46 mm Hg in both groups to ensure comparable alveolar ventilation. Respiratory data were collected several times during the first day and daily until Day 28. Both groups were similar at the time of inclusion. During the first 4 d of the study, the difference between peak pressure and positive end-expiratory pressure was significantly lower in the CTGI group by 18% to 35%, with the same tcPa(CO(2)) level and with no difference in the ratio of tcPa(O(2)) to fraction of inspired oxygen (245 +/- 29 versus 261 +/- 46 mm Hg [mean +/- SD] over the first 4 d). Extubation occurred sooner in the CTGI group (p < 0.05), and the duration of mechanical ventilation was shorter (median: 3.6 d; 25th to 75th quartiles: 1.5 to 12.0 d; versus median: 15.6 d; 25th to 75th quartiles: 7.9 to 22.2; p < 0.05) than in the non-CTGI group. CTGI allows the use of low-volume ventilation over a prolonged period and reduces the duration of mechanical ventilation.

Neonatal acute respiratory failure

Acute respiratory failure is the most common problem seen in the preterm and term infants admitted to neonatal intensive care units. In preterm infants, the most common cause of acute respiratory failure is respiratory distress syndrome caused by surfactant deficiency. Acute respiratory failure in term and near term infants is usually a result of meconium aspiration syndrome, sepsis, pulmonary hypoplasia, and primary pulmonary hypertension of the newborn. The response to various methods of treatment may vary, depending on the severity of respiratory failure and the cause of the acute respiratory failure. We reviewed the evidence for efficacy and current utilization of newer treatment modalities, including exogenous surfactant administration, high frequency ventilation, inhaled nitric oxide therapy, antenatal steroids for the prevention of respiratory distress syndrome, and use of postnatal steroids for the prevention of chronic lung disease.

First intention high-frequency oscillation with early lung volume optimization improves pulmonary outcome in very low birth weight infants with respiratory distress syndrome

OBJECTIVES

The lack of decline in chronic lung disease of prematurity despite the generalized use of surfactant and alternative modes of ventilation such as high-frequency oscillation (HFO) has been attributed to some misunderstanding of how HFO has to be used. We used a new ventilatory strategy in very low birth weight (VLBW) infants, by initiating HFO immediately after intubation and attempting early lung volume optimization before surfactant was administered.

STUDY DESIGN

The outcome of 32 VLBW infants, managed with first intention HFO over a period of 24 months (September 1, 1996 and August 31, 1998) was compared by chart review with 39 historical controls, consecutively managed with conventional mechanical ventilation (CMV) over a period of 24 months (January 1, 1994 and December 31, 1995).

SETTING

An 11-bed tertiary care pediatric and neonatal intensive care unit of a university teaching hospital.

RESULTS

The 2 groups of patients were similar in demographic distribution of birth weight, gestational age, race, and gender. Patients on first intention HFO were ventilator-dependent (median [95% confidence interval]: 5 [3-6] vs 14 [6-23] days) and oxygen-dependent (12 [4-17] vs 51 [20-60] days) for a shorter time than patients on CMV. The incidence of chronic lung disease at 36 weeks of gestational age was significantly lower in the HFO group compared with the CMV group (0% vs 34%).

CONCLUSIONS

First intention HFO with early lung volume optimization shortened the need for respiratory support and improved pulmonary outcome of VLBW infants with respiratory distress syndrome significantly.

High-frequency oscillatory ventilation does not decrease endothelin release in lung-lavaged rabbits

High-frequency oscillatory ventilation (HFO) has been shown to reduce lung injury and pulmonary arterial pressure (PAP). We hypothesized that HFO leads to decreased endothelin 1 (ET-1) and endothelin 3 (ET-3) release when compared to conventional mechanical ventilation (CMV) in lung-lavaged rabbits.

DESIGN

Prospective, randomized, controlled animal study. In 26 adult New Zealand White Rabbits ventilated by CMV or HFO under hypoxemic and normoxemic conditions after lung lavage (CMV-hypo: n = 5; CMV-normo: n = 8; HFO-hypo: n = 7; HFO-normo: n = 6) we recorded systemic and PAP, measured blood gases, ET-1 and ET-3 and calculated intrapulmonary venous admixture during a 4-h experiment. ET-1 was significantly increased after lavage (p < 0.05) with no further increase until the end of the experiment. Neither pulmonary arterial nor systemic arterial ET-1 differed between CMV and HFO or between hypoxemia and normoxemia. Systemic arterial ET-3, however, was significantly higher in HFO-hypo than in the other two groups ventilated under normoxemic conditions at the end of the experiment (HFO-hypo vs. CMV-normo, p < 0.05; HFO-hypo vs. HFO-normo, p < 0.05). PAP showed a continuous increase in all groups (p < 0.05). We did not find any correlation between PAP and ET-1 or ET-3. Intrapulmonary venous admixture increased in animals ventilated under hypoxemic conditions, whereas it decreased after lung lavage in those ventilated under normoxemic conditions until the end of the experiment (HFO-normo, p < 0.05).

CONCLUSIONS

This study suggests that HFO does not decrease ET-1 and ET-3 release compared to CMV in lung-lavaged rabbits. Hypoxemia, however, may increase ET-3 release from the lungs, leading to an increased intrapulmonary shunt.