[Early continuous positive pressure in the labor room]

Effects of 2 modes of positive pressure ventilation on respiratory mechanics and gas exchange in foals

BACKGROUND

Continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) can improve respiratory mechanics and gas exchange, but different airway pressures have not been compared in foals.

HYPOTHESIS/OBJECTIVES

Assess the effect of different airway pressures during CPAP and PSV have on respiratory function in healthy foals with pharmacologically induced respiratory insufficiency. We hypothesized that increased airway pressures would improve respiratory mechanics and increased positive end-expiratory pressure (PEEP) would be associated with hypercapnia.

ANIMALS

Six healthy foals from a university teaching herd.

METHODS

A prospective, 2-phase, 2-treatment, randomized cross-over study design was used to evaluate sequential interventions in sedated foals using 2 protocols (CPAP and PSV). Outcome measures included arterial blood gases, spirometry, volumetric capnography, lung volume and aeration assessed using computed tomography (CT).

RESULTS

Sedation and dorsal recumbency were associated with significant reductions in arterial oxygen pressure (PaO₂ ), respiratory rate, and tidal volume. Continuous positive airway pressure was associated with improved PaO₂ , without concurrent hypercapnia. Volumetric capnography identified improved ventilation:perfusion (V/Q) matching and increased carbon dioxide elimination during ventilation, and spirometry identified decreased respiratory rate and increased tidal volume. Peak inspiratory pressure was moderately associated with PaO₂ and lung volume. Improved pulmonary aeration was evident in CT images, and lung volume was increased, particularly during CPAP.

CONCLUSIONS AND CLINICAL IMPORTANCE

Both CPAP and PSV improved lung mechanics and gas exchange in healthy foals with induced respiratory insufficiency.

Respiratory strategies for preterm infants at birth

Neonatologists treating extremely premature infants in the delivery room are faced with many dilemmas, not least how best to support their breathing. A balance must be struck between helping those infants who need it and not applying potentially harmful treatments to infants who might not need them. Crucial to this process is being able to identify infants who might benefit.

Continuous positive airway pressure: scientific and clinical rationale

PURPOSE OF REVIEW

To present recent data on the role of noninvasive ventilation in the respiratory management of newborn infants.

RECENT FINDINGS

Noninvasive ventilation is growing in popularity but is applied using widely varying devices and settings. Although short-term physiological advantages were reported for bubble and variable-flow continuous positive airways pressure, neither has convincingly shown superior clinically important outcomes. Continuous positive airways pressure may be used as the initial mode of support for very preterm infants but increased rates of pneumothorax in infants not receiving surfactant are a concern. Methods of administering surfactant without endotracheal intubation deserve further study. Nasal intermittent positive-pressure ventilation shows promise as a primary treatment for respiratory distress syndrome. Optimal pressure settings for continuous positive airways pressure and nasal intermittent positive-pressure ventilation remain uncertain.

SUMMARY

Noninvasive ventilation has partially fulfilled its promise as a gentler alternative to ventilation via an endotracheal tube. Appropriately designed randomized clinical trials are required to determine the best nasal interfaces and pressure generators.

Nasal CPAP or intubation at birth for very preterm infants

BACKGROUND

Bronchopulmonary dysplasia is associated with ventilation and oxygen treatment. This randomized trial investigated whether nasal continuous positive airway pressure (CPAP), rather than intubation and ventilation, shortly after birth would reduce the rate of death or bronchopulmonary dysplasia in very preterm infants.

METHODS

We randomly assigned 610 infants who were born at 25-to-28-weeks' gestation to CPAP or intubation and ventilation at 5 minutes after birth. We assessed outcomes at 28 days of age, at 36 weeks' gestational age, and before discharge.

RESULTS

At 36 weeks' gestational age, 33.9% of 307 infants who were assigned to receive CPAP had died or had bronchopulmonary dysplasia, as compared with 38.9% of 303 infants who were assigned to receive intubation (odds ratio favoring CPAP, 0.80; 95% confidence interval [CI], 0.58 to 1.12; P=0.19). At 28 days, there was a lower risk of death or need for oxygen therapy in the CPAP group than in the intubation group (odds ratio, 0.63; 95% CI, 0.46 to 0.88; P=0.006). There was little difference in overall mortality. In the CPAP group, 46% of infants were intubated during the first 5 days, and the use of surfactant was halved. The incidence of pneumothorax was 9% in the CPAP group, as compared with 3% in the intubation group (P<0.001). There were no other serious adverse events. The CPAP group had fewer days of ventilation.

CONCLUSIONS

In infants born at 25-to-28-weeks' gestation, early nasal CPAP did not significantly reduce the rate of death or bronchopulmonary dysplasia, as compared with intubation. Even though the CPAP group had more incidences of pneumothorax, fewer infants received oxygen at 28 days, and they had fewer days of ventilation. (Australian New Zealand Clinical Trials Registry number, 12606000258550.).

A randomized trial comparing oxygen delivery on intermittent positive pressure with nasal cannulae versus facial mask in neonatal primary resuscitation

AIM

To compare, in a prospective clinical trial, oxygen delivery on intermittent positive pressure with nasal cannulae versus facial mask in primary resuscitation of the newborn with moderate asphyxia.

METHODS

617 neonates with moderate asphyxia at birth were randomized: 303 were resuscitated by oxygen on intermittent positive pressure with nasal cannuale and 314 neonates by mask. Resuscitation followed the Neonatal Resuscitation Program guidelines of the American Academy of Pediatrics, 3rd edition.

RESULTS

Resuscitation through the nasal route less frequently requires chest compressions and intubations (26 neonates needed chest compression and 20 needed intubation out of 314 resuscitated by mask; five neonates needed chest compression and two needed intubation out of 303 resuscitated by nasal cannulae). Apgar scores, admission rates to neonatal intensive care units, air-leak syndromes, birthweight, gestational age, use of prenatal steroids and deaths did not differ between groups.

CONCLUSION

Oxygen delivery on intermittent positive pressure with nasal cannulae in primary resuscitation of the newborn with moderate asphyxia is a less aggressive and potentially advantageous alternative to the traditional oral route.

Surfactant therapy for respiratory distress syndrome in premature neonates: a comparative review

Exogenous surfactant therapy has been part of the routine care of preterm neonates with respiratory distress syndrome (RDS) since the beginning of the 1990s. Discoveries that led to its development as a therapeutic agent span the whole of the 20th century but it was not until 1980 that the first successful use of exogenous surfactant therapy in a human population was reported. Since then, randomized controlled studies demonstrated that surfactant therapy was not only well tolerated but that it significantly reduced both neonatal mortality and pulmonary air leaks; importantly, those surviving neonates were not at greater risk of subsequent neurological impairment. Surfactants may be of animal or synthetic origin. Both types of surfactants have been extensively studied in animal models and in clinical trials to determine the optimum timing, dose size and frequency, route and method of administration. The advantages of one type of surfactant over another are discussed in relation to biophysical properties, animal studies and results of randomized trials in neonatal populations. Animal-derived exogenous surfactants are the treatment of choice at the present time with relatively few adverse effects related largely to changes in oxygenation and heart rate during surfactant administration. The optimum dose of surfactant is usually 100 mg/kg. The use of surfactant with high frequency oscillation and continuous positive pressure modes of respiratory support presents different problems compared with its use with conventional ventilation. The different components of surfactant have important functions that influence its effectiveness both in the primary function of the reduction of surface tension and also in secondary, but nonetheless just as important, role of lung defense. With greater understanding of the individual surfactant components, particularly the surfactant-associated proteins, development of newer synthetic surfactants has been made possible. Despite being an effective therapy for RDS, surfactant has failed to have a significant impact on the incidence of chronic lung disease in survivors. Paradoxically the cost of care has increased as surviving neonates are more immature and consume a greater proportion of neonatal intensive care resources. Despite this, surfactant is considered a cost-effective therapy for RDS compared with other therapeutic interventions in premature infants.

[Noninvasive ventilation of premature infants]

In a retrospective study we evaluated a one year use of nasal continuous positive pressure in our intensive care neonatal unit. One hundred and twelve newborns with a mean gestational age of 30.8 weeks were treated with this technique: 41 were treated early after birth for moderate respiratory; 71 were treated later, either following extubation and assisted ventilation, or as treatment of apnoeas. The main adverse effects were bowel gaseous distension and delayed oral nutrition. Nasal continuous positive airway pressure reduced the duration of intubation and assisted ventilation and could be used more frequently as early first line treatment in respiratory distress.

Nasal CPAP in newborns with acute respiratory failure

Outcome in neonates with acute respiratory failure supported initially either by rescue mechanical ventilation (IPPV) or by nasal continuous positive airway pressure (NCPAP) was compared in a retrospective review of cases seen at King Edward VIII Hospital between January and December 2000. IPPV and NCPAP were required by 89 and 85 neonates, respectively. The median weights (1900 vs 1650 g), male to female ratios (1.74:1 vs 1.34:1) and median gestational ages (32 vs 34 weeks) were similar in the two groups. Of the 89 neonates who required IPPV, 17 failed initial NCPAP and seven required ventilatory support for secondary reasons after NCPAP was initially successful. In the remainder (n = 65) who initially received IPPV, the mortality rate was 39% (n = 25) compared with 25% (n = 21) in the group who received NCPAP initially. Sixty-three neonates (74%) were initially successfully supported with NCPAP alone. Of these, fifty (79%) required no further respiratory support until discharge and seven received IPPV subsequently, five of whom died; six who were not offered mechanical ventilation also died. NCPAP did not provide adequate respiratory support in 22 newborns (26%). Of these, 17 received IPPV, five of whom died, and five who were not offered mechanical ventilation also died. Hyaline membrane disease and congenital pneumonia were the common primary diagnoses in both groups. NCPAP was a useful adjunct to mechanical ventilation in treating newborns for a variety of disorders causing respiratory failure. The delay in instituting mechanical ventilation by initial use of NCPAP did not adversely affect outcome.

Chronic oxygen dependency in infants born at less than 32 weeks' gestation: incidence and risk factors

OBJECTIVE

To assess incidence and clinical risk factors of chronic oxygen dependency (COD) among survivors who were born at or before 31 weeks' gestation.

METHODS

This prospective, multicenter study enrolled 802 infants who were born at or before 31 weeks' gestation and admitted to 8 level III neonatal intensive care units in northern and eastern France from January 1 through December 31, 1997. Need for oxygen to maintain oxygen saturation between 92% and 96% was assessed at 28 days of life and at 36 and 42 weeks' postconceptional age (PCA). Stepwise logistic regression analysis was used to identify the incidence of COD and the risk factors related to its occurrence.

RESULTS

The mortality rate was 14%. Antenatal corticotherapy was administered to 51% of patients, surfactant therapy to 76% of the ventilated patients, and high-frequency oscillatory ventilation at day 1 to 32%. At 28 days and 36 and 42 weeks' PCA, respectively, 25%, 15%, and 6% of survivors had COD. After adjustment for intercenter variations, we identified the significant risk factors for COD at these dates: a low gestational age, a high score on the Clinical Risk Index for Infants, intrauterine growth restriction, and surfactant treatment.

CONCLUSION

COD incidence was high at 28 days of life but decreased dramatically by 42 weeks' PCA. This study confirmed previously reported risk factors and underlined the importance of intrauterine growth restriction and the Clinical Risk Index for Infants as significant risk factors.