Pulmonary mechanics in ventilated preterm infants with respiratory distress syndrome after exogenous surfactant administration: a comparison between two surfactant preparations

A neonatal in-vitro study on the effect of the inflation pressure on end-tidal carbon dioxide levels

BACKGROUND

Describing the association of the peak inflation pressure (PIP) with end-tidal carbon dioxide (ETCO2) is a prerequisite for the development of closed loop ventilation in neonatal intensive care. We aimed to develop an in-vitro system to study this relationship.

METHODS

A ventilator was connected to a test lung, supplied with a stable CO2 concentration from a cylinder. The PIP was altered and the change in ETCO2 per unit of PIP was calculated in three models mimicking respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) and viral bronchiolitis.

RESULTS

The median (IQR) change in ETCO2 per unit of PIP was 0.23(0.13-0.38) kPa/cmH2O, using 138 paired measurements of PIP and ETCO2. The median (IQR) change in ETCO2 per unit of PIP, was higher when starting at an ETCO2 > 6 kPa [0.43(0.33-0.58) kPa/cmH2O] compared to starting at an ETCO2 < 6 kPa [0.14(0.08-0.20) kPa/cmH2O, p < 0.001]. The median (IQR) change in ETCO2 per unit of PIP, was larger in the model of RDS [0.33(0.13-0.51) kPa/cmH2O] compared to the BPD [0.23(0.13-0.33) kPa/cmH2O, p = 0.043] and the bronchiolitis models [0.15(0.10-0.31) kPa/cmH2O, p = 0.017].

CONCLUSIONS

The change in ETCO2 in response to increasing PIP was larger for higher ETCO2 values and in a model simulating neonatal RDS, compared to BPD and bronchiolitis.

Animal derived surfactant extract versus protein free synthetic surfactant for the prevention and treatment of respiratory distress syndrome

BACKGROUND

A wide variety of surfactant preparations have been developed and tested including synthetic surfactants and surfactants derived from animal sources. Although clinical trials have demonstrated that both synthetic surfactant and animal derived surfactant preparations are effective, comparison in animal models has suggested that there may be greater efficacy of animal derived surfactant products, perhaps due to the protein content of animal derived surfactant.

OBJECTIVES

To compare the effect of animal derived surfactant to protein free synthetic surfactant preparations in preterm infants at risk for or having respiratory distress syndrome (RDS).

SEARCH METHODS

Searches were updated of the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2014), PubMed, CINAHL and EMBASE (1975 through November 2014). All languages were included.

SELECTION CRITERIA

Randomized controlled trials comparing administration of protein free synthetic surfactants to administration of animal derived surfactant extracts in preterm infants at risk for or having respiratory distress syndrome were considered for this review.

DATA COLLECTION AND ANALYSIS

Data collection and analysis were conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Fifteen trials met the inclusion criteria. The meta-analysis showed that the use of animal derived surfactant rather than protein free synthetic surfactant resulted in a significant reduction in the risk of pneumothorax [typical relative risk (RR) 0.65, 95% CI 0.55 to 0.77; typical risk difference (RD) -0.04, 95% CI -0.06 to -0.02; number needed to treat to benefit (NNTB) 25; 11 studies, 5356 infants] and a marginal reduction in the risk of mortality (typical RR 0.89, 95% CI 0.79 to 0.99; typical RD -0.02, 95% CI -0.04 to -0.00; NNTB 50; 13 studies, 5413 infants).Animal derived surfactant was associated with an increase in the risk of necrotizing enterocolitis [typical RR 1.38, 95% CI 1.08 to 1.76; typical RD 0.02, 95% CI 0.01 to 0.04; number needed to treat to harm (NNTH) 50; 8 studies, 3462 infants] and a marginal increase in the risk of any intraventricular hemorrhage (typical RR 1.07, 95% CI 0.99 to 1.15; typical RD 0.02, 95% CI 0.00 to 0.05; 10 studies, 5045 infants) but no increase in Grade 3 to 4 intraventricular hemorrhage (typical RR 1.08, 95% CI 0.91 to 1.27; typical RD 0.01, 95% CI -0.01 to 0.03; 9 studies, 4241 infants).The meta-analyses supported a marginal decrease in the risk of bronchopulmonary dysplasia or mortality associated with the use of animal derived surfactant preparations (typical RR 0.95, 95% CI 0.91 to 1.00; typical RD -0.03, 95% CI -0.06 to 0.00; 6 studies, 3811 infants). No other relevant differences in outcomes were noted.

AUTHORS' CONCLUSIONS

Both animal derived surfactant extracts and protein free synthetic surfactant extracts are effective in the treatment and prevention of respiratory distress syndrome. Comparative trials demonstrate greater early improvement in the requirement for ventilator support, fewer pneumothoraces, and fewer deaths associated with animal derived surfactant extract treatment. Animal derived surfactant may be associated with an increase in necrotizing enterocolitis and intraventricular hemorrhage, though the more serious hemorrhages (Grade 3 and 4) are not increased. Despite these concerns, animal derived surfactant extracts would seem to be the more desirable choice when compared to currently available protein free synthetic surfactants.

Animal derived surfactant extract versus protein free synthetic surfactant for the prevention and treatment of respiratory distress syndrome

BACKGROUND

A wide variety of surfactant preparations have been developed and tested including synthetic surfactants and surfactants derived from animal sources. Although clinical trials have demonstrated that both synthetic surfactant and animal derived surfactant preparations are effective, comparison in animal models has suggested that there may be greater efficacy of animal derived surfactant products, perhaps due to the protein content of animal derived surfactant.

OBJECTIVES

To compare the effect of animal derived surfactant to protein free synthetic surfactant preparations in preterm infants at risk for or having respiratory distress syndrome (RDS).

SEARCH METHODS

Searches were updated of the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2014), PubMed, CINAHL and EMBASE (1975 through November 2014). All languages were included.

SELECTION CRITERIA

Randomized controlled trials comparing administration of protein free synthetic surfactants to administration of animal derived surfactant extracts in preterm infants at risk for or having respiratory distress syndrome were considered for this review.

DATA COLLECTION AND ANALYSIS

Data collection and analysis were conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Fifteen trials met the inclusion criteria. The meta-analysis showed that the use of animal derived surfactant rather than protein free synthetic surfactant resulted in a significant reduction in the risk of pneumothorax [typical relative risk (RR) 0.65, 95% CI 0.55 to 0.77; typical risk difference (RD) -0.04, 95% CI -0.06 to -0.02; number needed to treat to benefit (NNTB) 25; 11 studies, 5356 infants] and a marginal reduction in the risk of mortality (typical RR 0.89, 95% CI 0.79 to 0.99; typical RD -0.02, 95% CI -0.04 to -0.00; NNTB 50; 13 studies, 5413 infants).Animal derived surfactant was associated with an increase in the risk of necrotizing enterocolitis [typical RR 1.38, 95% CI 1.08 to 1.76; typical RD 0.02, 95% CI 0.01 to 0.04; number needed to treat to harm (NNTH) 50; 8 studies, 3462 infants] and a marginal increase in the risk of any intraventricular hemorrhage (typical RR 1.07, 95% CI 0.99 to 1.15; typical RD 0.02, 95% CI 0.00 to 0.05; 10 studies, 5045 infants) but no increase in Grade 3 to 4 intraventricular hemorrhage (typical RR 1.08, 95% CI 0.91 to 1.27; typical RD 0.01, 95% CI -0.01 to 0.03; 9 studies, 4241 infants).The meta-analyses supported a marginal decrease in the risk of bronchopulmonary dysplasia or mortality associated with the use of animal derived surfactant preparations (typical RR 0.95, 95% CI 0.91 to 1.00; typical RD -0.03, 95% CI -0.06 to 0.00; 6 studies, 3811 infants). No other relevant differences in outcomes were noted.

AUTHORS' CONCLUSIONS

Both animal derived surfactant extracts and protein free synthetic surfactant extracts are effective in the treatment and prevention of respiratory distress syndrome. Comparative trials demonstrate greater early improvement in the requirement for ventilator support, fewer pneumothoraces, and fewer deaths associated with animal derived surfactant extract treatment. Animal derived surfactant may be associated with an increase in necrotizing enterocolitis and intraventricular hemorrhage, though the more serious hemorrhages (Grade 3 and 4) are not increased. Despite these concerns, animal derived surfactant extracts would seem to be the more desirable choice when compared to currently available protein free synthetic surfactants.

Surfactant

Exogenous pulmonary surfactant, widely used in neonatal care, is one of the best-studied treatments in neonatology, and its introduction in the 1990s led to a significant improvement in neonatal outcomes in preterm infants, including a decrease in mortality. This chapter provides an overview of surfactant composition and function in health and disease and summarizes the evidence for its clinical use.

Surfactant therapy for acute lung injury and acute respiratory distress syndrome

This article examines exogenous lung surfactant replacement therapy and its usefulness in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Surfactant therapy is beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 years with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. This article reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, focusing on its potential advantages in patients with direct pulmonary forms of these syndromes.

Surfactant for pediatric acute lung injury

This article reviews exogenous surfactant therapy and its use in mitigating acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) in infants, children, and adults. Biophysical and animal research documenting surfactant dysfunction in ALI/ARDS is described, and the scientific rationale for treatment with exogenous surfactant is discussed. Major emphasis is placed on reviewing clinical studies of surfactant therapy in pediatric and adult patients who have ALI/ARDS. Particular advantages from surfactant therapy in direct pulmonary forms of these syndromes are described. Also discussed are additional factors affecting the efficacy of exogenous surfactants in ALI/ARDS.

Overview of surfactant replacement trials

Clinical trials have evaluated the overall efficacy of surfactant therapy, as well as the relative efficacy of different surfactant preparations, the optimal timing of administration and the optimal dosage. Surfactant therapy leads to significant clinical improvement in infants at risk for, or having, respiratory distress syndrome (RDS). Clinical trials that compared the effects of synthetic or animal-derived surfactant preparations to placebo or no therapy demonstrate that surfactant therapy lead to rapid improvement in oxygenation, decreased ventilator support, decreased risk of pneumothorax, and mortality. Earlier treatment, prophylactic treatment of infants at high risk of developing RDS, and selective re-treatment leads to improved clinical outcome as well. Currently available animal-derived surfactants are superior to non-protein-containing synthetic surfactants. Ongoing evaluation will determine if important differences in animal-derived products are noted. Future trials will evaluate third-generation surfactant products and further refine what constitutes optimal use of surfactant.

Lung surfactants for neonatal respiratory distress syndrome: animal-derived or synthetic agents?

Exogenous surfactant therapy is widely used in the management of neonatal respiratory distress syndrome. Two types of surfactants are available: synthetic surfactants, and those derived from animal sources ("natural" surfactants). Both of these surfactants have been shown to be effective. In this article, we review the evidence to compare the two types of surfactants in terms of their physical properties, physiologic effects, and clinical outcomes. Natural surfactants have been shown to have advantages over synthetic surfactants in their physical properties and physiologic effects in animals, as well as in humans. A systematic review of 11 randomized clinical trials comparing natural and synthetic surfactants demonstrated that the use of natural surfactant preparations results in greater clinical benefits compared with synthetic surfactants. These benefits include a more rapid improvement in oxygenation and lung compliance after surfactant therapy, a decrease in the risk of mortality (typical relative risk 0.87; typical risk difference -0.02), and a decrease in the risk of pneumothorax (typical relative risk 0.63; typical risk difference -0.04). Although the use of natural surfactants results in a slightly increased risk of intraventricular hemorrhage (typical relative risk 1.09; typical risk difference 0.03), there is no increase in the risk of grade 3 or 4 intraventricular hemorrhage. There are theoretical but unproven risks of natural surfactants, such as transmission of infectious agents, immunogenicity and impurities in composition. The use of natural surfactants is preferred in most situations. In addition, clinicians should determine the costs of different types of surfactants in their individual practice settings and use this information in decision-making.

Current surfactant use in premature infants

Exogenous surfactant therapy has been a significant advance in the management of preterm infants with RDS. It has become established as a standard part of the management of such infants. Both natural and synthetic surfactants lead to clinical improvement and decreased mortality, with natural surfactants having additional advantages over currently available synthetic surfactants. The use of prophylactic surfactant administered after initial stabilization at birth to infants at risk for RDS has benefits compared with rescue surfactant given to treat infants with established RDS. In infants who do not receive prophylaxis, earlier treatment (before 2 hours) has benefits over later treatment. The use of multiple doses of surfactant is a superior strategy to the use of a single dose, whereas the use of a higher threshold for retreatment seems to be as effective as a low threshold. Adverse effects of surfactant therapy are infrequent and usually not serious. Long-term follow-up of infants treated with surfactant in the neonatal period is reassuring. In the future we are likely to see the development of new types of surfactants. Further research is required to determine the optimal use of surfactant in conjunction with other respiratory interventions.

A model of neonatal tidal liquid ventilation mechanics

Tidal liquid ventilation (TLV) with perfluorocarbons (PFC) has been proposed to treat surfactant-deficient lungs of preterm neonates, since it may prevent pulmonary instability by abating saccular surface tension. With a previous model describing gas exchange, we showed that ventilator settings are crucial for CO(2) scavenging during neonatal TLV. The present work is focused on some mechanical aspects of neonatal TLV that were hardly studied, i.e. the distribution of mechanical loads in the lungs, which is expected to differ substantially from gas ventilation. A new computational model is presented, describing pulmonary PFC hydrodynamics, where viscous losses, kinetic energy changes and lung compliance are accounted for. The model was implemented in a software package (LVMech) aimed at calculating pressures (and approximately estimate shear stresses) within the bronchial tree at different ventilator regimes. Simulations were run taking the previous model's outcomes into account. Results show that the pressure decrease due to high saccular compliance may compensate for the increased pressure drops due to PFC viscosity, and keep airway pressure low. Saccules are exposed to pressures remarkably different from those at the airway opening; during expiration negative pressures, which may cause airway collapse, are moderate and appear in the upper airways only. Delivering the fluid with a slightly smoothed square flow wave is convenient with respect to a sine wave. The use of LVMech allows to familiarize with LV treatment management taking the lungs' mechanical load into account, consistently with a proper respiratory support.

Feasibility of tidal volume-guided ventilation in newborn infants: a randomized, crossover trial using the volume guarantee modality

BACKGROUND AND AIM

Volume guarantee (VG) is a new composite mode of pressure-limited ventilation, available on the Dräger Babylog 8000 ventilator, which allows the clinician to set a target mean tidal volume to be delivered while still maintaining control over peak airway pressures. This study aimed to investigate the feasibility and efficacy of this mode of ventilation in premature newborn infants with respiratory distress syndrome (RDS).

METHODS

Two groups of infants were studied: those receiving synchronized intermittent positive pressure ventilation (SIPPV) in early phase of RDS (group 1) and those in recovery phase of RDS being weaned from artificial ventilation through synchronized intermittent mandatory ventilation (SIMV; group 2). Both groups of infants were studied over a 4-hour period. Before the start of the study, the infants were either receiving SIPPV (group 1) or SIMV (group 2). Infants in group 1 were randomized to either continue on SIPPV for the first hour of the study or to receive SIPPV plus VG for the first hour. Subsequently, the 2 modes were used alternately for the remaining three 1-hour periods. Similarly, infants in group 2 were randomized to either continue on SIMV for the first hour of the study or to receive SIMV plus VG for the first hour. Data on ventilation parameters and transcutaneous carbon dioxide and oxygen were collected continuously.

RESULTS

Forty infants were studied, 20 in each group. The mean (standard error) gestational age was 27.9 (0.3) weeks; birth weight was 1064 (60) g. No adverse events were observed during the study. Fractional inspired oxygen during SIMV plus VG was 0.31 (0.3); during SIMV, 0.31 (0.3); during SIPPV plus VG, 0.41 (0.4); and during SIPPV, 0.40 (0.4). Transcutaneous carbon dioxide pressure during SIMV plus VG was 6.0 (2.2) kPa; during SIMV, 5.9 (2.2) kPa; during SIPPV plus VG, 6.4 (2.9) kPa; and during SIPPV, 6.4 (2.8) kPa. Transcutaneous partial pressure of oxygen during SIMV plus VG was 8.4 (8.7) kPa; during SIMV, 8.6 (8.8) kPa; during SIPPV plus VG, 7.6 (4.0) kPa; and during SIPPV, 7.7 (4.2) kPa. None of these differences was statistically significant. The mean (standard error) peak inspiratory pressure used during SIMV was 17.1 (3.4) cm of water; during SIMV plus VG, 15.0 (7.5) cm of water; during SIPPV plus VG, 17.1 (9.3) cm of water; and during SIPPV, 18.7 (8.3) cm of water. The mean airway pressure during SIMV plus VG was 6.5 (3.1) cm of water; during SIMV, 6.9 (2.8) cm of water; during SIPPV plus VG, 9.6 (4.5) cm of water; and during SIPPV, 9.8 (4.6) cm of water.

CONCLUSION

VG seems to be a stable and feasible ventilation mode for neonatal patients and can achieve equivalent gas exchange using statistically significant lower peak airway pressures both during early and recovery stages of RDS.ventilation, airway pressure, volume guarantee, tidal volume.

Natural surfactant extract versus synthetic surfactant for neonatal respiratory distress syndrome

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To compare the effect of synthetic surfactant to natural surfactant in premature infants with established respiratory distress syndrome.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH terms: pulmonary surfactant; limits: age groups, newborn infant; publication type, clinical trial), previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, and journal hand searching in the English language.

SELECTION CRITERIA

Randomized controlled trials comparing administration of synthetic surfactants to administration of natural surfactant extracts in premature infants with respiratory distress syndrome were considered for this review.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including pneumothorax, patent ductus arteriosus, necrotizing enterocolitis, intraventricular hemorrhage (all intraventricular hemorrhage and severe intraventricular hemorrhage), chronic lung disease, retinopathy of prematurity, and mortality were excerpted by the primary reviewer (R. Soll). Data analysis was conducted according to the standards of the Neonatal Cochrane Review Group.

MAIN RESULTS

The meta-analysis supports a significant reduction in the risk of pneumothorax (typical relative risk 0.68, 95% CI 0.56, 0.83; typical risk difference -0.04 95% CI -0.06, -0.02). No disadvantages to natural surfactant extract treatment are noted regarding other outcomes. A trend towards reduced mortality is noted in association with natural surfactant extract treatment.

REVIEWER'S CONCLUSIONS

Both natural surfactant extracts and synthetic surfactant extracts are effective in the treatment of established respiratory distress syndrome. Comparative trials demonstrate greater early improvement in the requirement for ventilatory support and fewer pneumothoraces associated with natural surfactant extract treatment. On clinical grounds, natural surfactant extracts would seem to be the more desirable choice.

Comparison of respiratory function and fluid balance in very low birthweight infants given artificial or natural surfactant or no surfactant treatment

Exogenous surfactant administration improves respiratory function. The speed of improvement appears greater if a natural rather than an artificial surfactant is used, our aim was to determine if that effect was explained by differences in fluid balance, evidenced by the timing of the diuresis onset (i.e. output greater than input). Thirty infants (median gestational age 29 weeks), 10 given an artificial surfactant (Exosurf), 10 a natural surfactant (Survanta) and 10 no surfactant (controls) were studied. During the first three days, compliance and functional residual capacity were measured daily, arginine vasopressin (AVP) levels estimated on days 1, 3 and 5 and, in 8-hourly intervals, the median arterial/alveolar ratio was calculated for each individual and urine output and fluid input recorded. Throughout the three-day period, the median arterial/alveolar ratio was always significantly higher in the control compared to the two surfactant groups (p < 0.05). On day 3 the Exosurf-treated babies had lower compliance and functional residual capacity (p < 0.05) than the other two groups. Neither the timing of diuresis onset, timing of the maximum diuresis nor the AVP levels, however, differed significantly between the groups. Only surfactant treatment and type of surfactant, but not the timing of the onset nor of the maximum diuresis, related significantly to changes in lung function. These results do not support the hypothesis that differences in fluid balance explain differences in the lung function improvement rate following natural and artificial surfactant.

A risk-benefit assessment of natural and synthetic exogenous surfactants in the management of neonatal respiratory distress syndrome

Alveolar surfactant is central to pulmonary physiology. Quantitative and qualitative surfactant abnormalities appear to be the primary aetiological factors in neonatal respiratory distress syndrome (RDS) and exogenous replacement of surfactant is a rational treatment. Available exogenous surfactants have a natural (mammal-derived lung surfactants) or synthetic origin. Pharmacodynamic and clinical studies have demonstrated that exogenous surfactants immediately improve pulmonary distensibility and gas exchange; however, this is achieved more slowly and with more failures with synthetic surfactants. The ensuing advantageous haemodynamic effects are not so striking and they include an inconvenient increased left to right ductal shunt. Two strategies of administration have been used: prophylactic or rescue therapy to treat declared RDS. All methods of instillation require intubation. In addition to the early benefits (improved gas exchange and reduced ventilatory support) the incidence of classical complications of RDS, especially air leak events, is decreased except for the uncommon problem of pulmonary haemorrhage. The incidence of bronchopulmonary dysplasia is neither uniformly nor significantly reduced although the severity appears to be lessened. The overall incidence of peri-intraventricular haemorrhages is not diminished although separate trials have shown a decreased rate. The most striking beneficial effect of exogenous surfactants is the increased survival (of about 40%) of treated very low birthweight neonates. A small number of adverse effects has been described. The long term outcome of survivor neonates with RDS treated with surfactants versus control neonates with RDS not treated with surfactants is similar in terms of physical growth, at least as good in terms of respiratory status, with a similar or slightly better neurodevelopmental outcome. There is not clear benefit of exogenous surfactant therapy in extremely premature infants (< 26 weeks gestational age, birthweight < 750 g). The potential risks of contamination, inflammatory and immunogenic reaction and the inhalation of platelet activating factor remain a theoretical concern of surfactant therapy which has not been confirmed in clinical practice. The optimal timing of treatment favours prophylaxis over rescue treatment and early rescue treatment rather than delayed therapy. Meta-analyses suggest the clinical superiority of natural surfactant extracts over a synthetic one (colfosceril palmitate). The economic impact of surfactant therapy is favourable and the costs per quality-adjusted life year (QALY) for surviving surfactant treated infants are low. In conclusion, the mid and long term benefit/risk ratio clearly favours the use of exogenous surfactants to prevent or to treat RDS in neonates who have a gestational age of > 26 weeks or a birthweight of > 750 g, especially with the prophylactic strategy using natural surfactant extracts.

Repeated doses of the perfluorocarbon FC-100 improve lung function of preterm lambs

Intratracheal administration of a single dose of the perfluorocarbon FC-100 improves lung function in surfactant-deficient animals. In this study we compared the response to repeated doses of FC-100 (3 mL/kg 3% solution, n = 5) with that observed after administration of Exosurf (5 mL/kg, n = 5) to mechanically ventilated preterm lambs of 125 d of gestation. The initial dose of FC-100 rapidly increased arterial PO2, decreased arterial PCO2, and improved arterial pH. Also dynamic lung compliance markedly improved with this agent. Administration of an additional dose of FC-100 resulted in relatively similar changes, albeit of lesser magnitude than those observed with the initial dose. In contrast, Exosurf did not improve these variables even after three doses. All lambs treated with FC-100 survived the 6-h study period, whereas one of the five Exosurf-treated lambs survived (p < 0.05). Mean arterial blood pressure and heart rate decreased in those lambs that received FC-100, but not in surviving lambs that received Exosurf. Our data demonstrate that repeated intratracheal administration of the perfluorocarbon FC-100 improves lung function and survival of surfactant-deficient lambs better than the synthetic surfactant Exosurf. We speculate that tensio-active agents with properties different from surfactant, such as FC-100, might improve lung function in preterm neonates with diseases due to surfactant deficiency.

[Natural or artificial surfactants? Arguments in favour of natural surfactants]

The use of exogenous surfactant (ES) is an essential component for prevention and treatment of hyaline membrane disease (HMD). The ES available for clinical use are of two therapeutic classes: natural surfactants prepared from mammalian lung and artificial surfactants. The choice between these two classes of ES is controversial. In this overview, we present the arguments in favour of the preferential use of natural ES. The presence of hydrophobic specific proteins (SP-B and SP-C) provides to natural ES better surface tension properties than artificial ES. The in vitro greater efficacy of natural ES has been confirmed in vivo in experimental models of surfactant deficiency, human pharmacodynamic studies, and comparative clinical trials. Furthermore, the excellent clinical tolerance and harmlessness of natural ES has been firmly established. A meta-analysis of the comparative clinical trials between natural ES and one artificial ES (enrolling as many as 4400 babies treated for HMD) suggests that the use of natural ES compared to this artificial ES significantly reduces the neonatal mortality by 20%. In conclusion, all these arguments are in favor of the preferential use of natural ES for prevention and treatment of HMD.