Severe Acute Viral Bronchiolitis Research Articles

Respiratory effort during noninvasive positive pressure ventilation and continuous positive airway pressure in severe acute viral bronchiolitis.

To assess if noninvasive positive pressure ventilation (NIPPV) is associated with a greater reduction in respiratory effort as compared to continuous positive airway pressure (CPAP) during severe acute bronchiolitis, with both supports set either clinically or physiologically. Twenty infants (median [IQR] age 1.2 [0.9; 3.2] months) treated <24 h with noninvasive respiratory support (CPAP Clin, set at 7 cmH2 O, or NIPPV Clin) for bronchiolitis were included in a prospective single-center crossover study. Esogastric pressures were measured first with the baseline support, then with the other support. For each support, recordings were performed with the clinical setting and a physiological setting (CPAP Phys and NIPPV Phys), aiming at normalising respiratory effort. Patients were then treated with the optimal support. The primary outcome was the greatest reduction in esophageal pressure-time product (PTPES /min). Other outcomes included improvement of the other components of the respiratory effort. NIPPV Clin and Phys were associated with a lower PTPES /min (164 [105; 202] and 106 [78; 161] cmH2 O s/min, respectively) than CPAP Clin (178 [145; 236] cmH2 O s/min; p = 0.01 and 2 × 10-4 , respectively). NIPPV Clin and Phys were also associated with a significant reduction of all other markers of respiratory effort as compared to CPAP Clin. PTPES /min with NIPPV (Clin or Phys) was not different from PTPES /min with CPAP Phys. There was no significant difference between physiological and clinical settings. NIPPV is associated with a significant reduction in respiratory effort as compared to CPAP set at +7 cmH2 O in infants with severe acute bronchiolitis. CPAP Phys performs as well as NIPPV Clin.

The role of gene polymorphism of some immune response molecules in the development of acute virus-induced bronchiolitis

The aim of research: To investigate the genetic polymorphism of immune response molecules (TNFα-308G&gt; A (rs1800629), IL4-589C&gt;T (rs2243250), IL10-592C&gt; A (rs1800872), IL10-819C&gt; T (rs1800871), IL10-1082G&gt;A (rs1800896), IL-17A-197G&gt; A (rs2275913), IL- 17F-161His&gt; Arg (rs763780), TLR-2-753Arg&gt;Gln (rs5743708), TLR-6-249Ser&gt;Pro (rs5743810) and assess their prognostic value in the development of acute virus-induced bronchiolitis.Materials and methods. The study included children of the first year of life, whose average age was 4.2 ± 3.7 months. The main group consisted of 106 patients with moderate and severe acute viral bronchiolitis, more often associated with respiratory syncytial virus (56.6%). The control group consisted of 100 healthy children of the same age who had no signs of acute respiratory infection at the time of examination and did not receive passive immunoprophylaxis of respiratory syncytial infection. Genotyping was performed using the polymerase chain reaction method. The analysis of the results included the compliance with the Hardy-Weinberg law, the χ 2 test, the relative chance, and its 95% confidence interval. To assess the distribution of the claimed gene polymorphisms and their alleles, we used the general (χ2 test, df =2) and multiplicative (χ2 test, df =1) inheritance models.Results. It was revealed that the risk of developing acute viral bronchiolitis is increased compared to the healthy population in carriers of the following genotypes: CC, ST gene IL10-819C&gt; T (rs1800871), GG, AA gene IL-17A-197G&gt; A (rs2275913), HisHis gene IL-17F-161His&gt; Arg (rs763780), SerSer, SerPro gene TLR-6-249Ser&gt; Pro (rs5743810), GG gene TNF-α-308G&gt;A (rs1800629). The TT genotype of the IL10-819C&gt;T (rs1800871) gene is associated with a high risk of developing bacterial complications (pneumonia) in viral bronchiolitis. Carriers of genotypes AA, CC of the IL10-592C&gt; A (rs1800872) gene have an increased likelihood of a severe course of viral bronchiolitis.Conclusion. Genetic analysis of gene polymorphism IL10-592C&gt; A (rs1800872), IL10-819C&gt; T (rs1800871), IL-17A-197G&gt; A (rs2275913), IL-17F-161His&gt; Arg (rs763780), TLR-6-249Ser&gt; Pro (rs5743810), TNF-α-308 G&gt;A (rs1800629) can be used as a personalized developmental criterion acute virus-induced bronchiolitis in children, determining the severity of its course and the likelihood of complications.

Predicting the severity of viral bronchiolitis in children

Acute viral bronchiolitis is one of the common causes of hospitalization and mortality, especially among children in the first year of life who have risk factors (prematurity, congenital heart defects, bronchopulmonary dysplasia, immunosuppression). As factors associated with the severe course of bronchiolitis, along with the traditional ones, single nucleotide polymorphisms of the genes of the immune response molecules can be considered.The aim. Based on the analysis of clinical, laboratory and molecular genetic parameters, to identify prognostic criteria for the severe course of acute viral bronchiolitis in children.Materials and methods. The study included 106 children with acute viral bronchiolitis (severe course – 34, mild course – 72), the etiology of which in 67.9 % was respiratory syncytial virus. Forty-seven anamnestic, clinical, traditional laboratory and molecular genetic parameters were assessed as prognostic criteria. Determination of SNP genes of cytokines IL-4 (C-589T), IL-10 (G-1082A), IL-10 (C-592A), IL-10 (C-819T), TNF-α (G-308A), IL-17A (G197A), IL-17F (His161Arg), TLR2-753ArgGln, TLR6-Ser249Pro in venous blood was carried out by the polymerase chain reaction method.Results. An additional criterion for the risk of developing a severe course of bronchiolitis can be the mutant genotype (AA) SNP of the IL-10 gene (C-592A), which was detected exclusively in the group of patients with severe bronchiolitis, increasing the risk of developing a severe disease by 16.11 times (OR = 16.11; 95 % CI: 0.81–121.22, p = 0.02) in conjunction with already established modifying factors: the presence of congenital heart disease, bronchopulmonary dysplasia, prematurity, birth weight &lt; 1500 g. Based on a comprehensive assessment of the established risk factors, a method has been developed that allows calculate the likelihood of developing a severe course of acute viral bronchiolitis. Conclusion. The use of the developed prediction method will not only increase the likelihood of developing severe acute viral bronchiolitis in children, but also determine the priority group among children with predictors of severe viral bronchiolitis for priority immunoprophylaxis against RS-virus infection.

Differences of Medical Care for Acute Severe Viral Bronchiolitis in Two Urban Areas in Europe.

Acute viral bronchiolitis is a frequent disease in infancy. There is little knowledge on medical care of severely affected infants in different European countries. Infants (n=146) with bronchiolitis requiring respiratory support in winter season 2015/2016 treated in either one of two regions in Central Europe: South of greater Paris region in France (group 1) and Ruhr area in Germany (group 2). Retrospective chart review. Primary outcome parameter was duration of respiratory support. Infants in group 1 (n=96) were younger, suffered less frequently from neurologic disorders and had lower respiratory rates than in group 2 (n=50). CO2 levels and dyspnea score were similar. Ninety percent of infants in group 1 were treated by nasal Continuous Airway Pressure CPAP, while 80% of infants in group 2 were treated by High Flow Nasal Cannula HFNC. Duration of respiratory support was significantly shorter in group 1. Infants in group 2 received more frequently infusion therapy, more antibiotics and more inhalation therapy. Our results show better outcome for infants with viral bronchiolitis treated in France. Striking differences were the practice of respiratory support (nasal CPAP vs. HFNC) and the prescription of supportive treatments. Treatment approaches in severe acute viral bronchiolitis differ widely between a French and a German urban region.

L’anémie, un nouveau facteur de sévérité de la bronchiolite aiguë du nourrisson ?

IntroductionThe role of anemia is raised as a risk of low respiratory infection of the child, but there are no data on anemia as a severity factor in acute viral bronchiolitis (AVB) in infants. MethodsAll infants less than 16 weeks old admitted to Montpellier University Hospital from 2015/10/01 to 2016/04/01 for AVB were included in a retrospective observational study. The primary objective was to determine whether the hemoglobin (Hb) concentration on admission was an independent factor of clinical severity, judged by the modified Wood's clinical asthma score (m-WCAS). The secondary objective was to assess the impact of Hb level on the characteristics of hospitalization, including the type and duration of respiratory support. ResultsThe m-WCAS was used at least once during hospitalization in 180 out of 220 patients (82%), making it possible to distinguish patients with mild AVB (maximum m-WCAS<2, n=81) from patients with severe AVB (maximum m-WCAS>2, n=99). A logistic regression model indicated that the Hb concentration, for every 1g/dL decrement, was an independent factor of AVB severity (OR 1.16 [1.03–1.29], P=0.026). A level under 10g/dL on admission was associated with a higher use of continuous positive airway pressure (P<0.001), as well as a longer duration of respiratory support (P=0.01). ConclusionThis study suggested that anemia may influence the clinical expression of AVB in young infants.

Un score échographique pulmonaire simple peut-il prédire la durée de ventilation des nourrissons atteints de bronchiolite aiguë sévère ?

BackgroundLung ultrasound (LU) is a bedside point-of-care technique in critical care and emergency medicine. LU is quick and non-irradiating, and provides accurate diagnostic information when compared with chest radiographs. Specific LU signs have been described for bronchiolitis. This study aimed to evaluate the correlation between severity of LU-diagnosed lung lesions, using a quantitative LU score, and the length of non-invasive ventilation (LOV) for infants diagnosed with severe viral bronchiolitis. MethodsThis was a prospective observational single-center study conducted at a level 3 pediatric intensive care unit. A LU score was calculated for 47 infants under 6 months of age with severe acute viral bronchiolitis during the 2015–2016 epidemic, and the number of intercostal spaces with consolidation or interstitial syndrome was counted for each lung. The LU score is based on the presence of A lines or B-line artifacts and consolidation (0–2 points). The modified Wood score (mWCAS) was used to define clinical severity. Other parameters such as gestational age at birth, age, supplemental oxygen (LOS), and length of stay were recorded. All LU scans were later reviewed by two trained ultrasonographers to assess the score's inter-rater reproducibility. ResultsThe LU score on admission (3.5±2.6) did not correlate with LOV (69±68.6), mWCAS score (4±1.6), LOS (3±3.4), or length of stay (4±3.4). However, there was a significant correlation between the number of affected intercostal spaces on the right and LOS (Spearman's Rho 0.318; P=0.037). ConclusionThis is the first study to evaluate the use of LU in infants needing PICU admission for severe acute bronchiolitis. The LU score does not correlate with LOV, mWCAS, LOS, or length of stay, but the number of pathological intercostal spaces on the right side correlates significantly with LOS. Although LU scores have been validated for the newborn and the adult, this has been in the setting of restrictive lung diseases. Bronchiolitis is a predominantly obstructive lung disease and this may explain the lack of performance observed.

High flow nasal cannula (HFNC) versus nasal continuous positive airway pressure (nCPAP) for the initial respiratory management of acute viral bronchiolitis in young infants: a multicenter randomized controlled trial (TRAMONTANE study).

Nasal continuous positive airway pressure (nCPAP) is currently the gold standard for respiratory support for moderate to severe acute viral bronchiolitis (AVB). Although oxygen delivery via high flow nasal cannula (HFNC) is increasingly used, evidence of its efficacy and safety is lacking in infants. A randomized controlled trial was performed in five pediatric intensive care units (PICUs) to compare 7cmH2O nCPAP with 2L/kg/min oxygen therapy administered with HFNC in infants up to 6months old with moderate to severe AVB. The primary endpoint was the percentage of failure within 24h of randomization using prespecified criteria. To satisfy noninferiority, the failure rate of HFNC had to lie within 15% of the failure rate of nCPAP. Secondary outcomes included success rate after crossover, intubation rate, length of stay, and serious adverse events. From November 2014 to March 2015, 142 infants were included and equally distributed into groups. The risk difference of -19% (95% CI -35 to -3%) did not allow the conclusion of HFNC noninferiority (p=0.707). Superiority analysis suggested a relative risk of success 1.63 (95% CI 1.02-2.63) higher with nCPAP. The success rate with the alternative respiratory support, intubation rate, durations of noninvasive and invasive ventilation, skin lesions, and length of PICU stay were comparable between groups. No patient had air leak syndrome or died. In young infants with moderate to severe AVB, initial management with HFNC did not have a failure rate similar to that of nCPAP. This clinical trial was recorded in the National Library of Medicine registry (NCT 02457013).

Utilisation des lunettes nasales à haut débit chez les nourrissons hospitalisés en service d’accueil des urgences pédiatriques pour bronchiolite : étude observationnelle

High-flow nasal cannula oxygen therapy (HFNC) is a technique for noninvasive ventilation commonly used in pediatric intensive care units for respiratory distress, particularly in acute bronchiolitis. HFNC was introduced in the pediatric emergency department of the Reims university hospital for the treatment of infants with moderate to severe acute viral bronchiolitis. This retrospective observational study aimed to investigate the use of HFNC in a pediatric emergency ward, describing the groups of infants with acute viral bronchiolitis to be treated either with conventional oxygen therapy or with HFNC therapy. A total of 89 infants aged less than 6 months were included between December 2013 and April 2014. The choice of the type of oxygen used belonged to the pediatrician, according to his or her assessment of the clinical severity of the patient's condition, guided by a protocol of HFNC use for the treatment of moderate to severe bronchiolitis and limited by the availability of a single device in the department. Eighty-nine infants were included; 64% were boys. Fifty-seven infants (64%) had no medical history. At admission, 39 infants (46.4%) had tachypnea and 75 (84.3%) intercostal indrawing. RSV was found in 75 infants (97.4% of infants had a positive respiratory virology test). Seventy-six infants (85.4%) were treated with conventional oxygen therapy and 13 (14.6%) with HFNC. At admission, the mean weight for infants treated with HFNC was lower (P=0.03), the oxygen saturation level was 86.7% versus 93.5% (P=0.03) for conventional oxygen therapy. Moreover, modified Wood's score was higher and the mean PCO2 was 61.1 versus 49.9mmHg (P<0.01). Six infants treated with conventional oxygen therapy (7.9%) and six with HFNC (46.1%) were then transferred to an intensive care unit. HFNC therapy in the pediatric emergency ward seems to be an advantageous therapeutic option in the early treatment of infants with moderate to severe bronchiolitis, but further studies are needed to specify its indications and effectiveness.

High-flow nasal cannula: recommendations for daily practice in pediatrics.

High-flow nasal cannula (HFNC) is a relatively new device for respiratory support. In pediatrics, HFNC use continues to increase as the system is easily set up and is well tolerated by patients. The use of nasal cannula adapted to the infant’s nares size to deliver heated and humidified gas at high flow rates has been associated with improvements in washout of nasopharyngeal dead space, lung mucociliary clearance, and oxygen delivery compared with other oxygen delivery systems. HFNC may also create positive pharyngeal pressure to reduce the work of breathing, which positions the device midway between classical oxygen delivery systems, like the high-concentration face mask and continuous positive airway pressure (CPAP) generators. Currently, most of the studies in the pediatric literature suggest the benefits of HFNC therapy only for moderately severe acute viral bronchiolitis. But, the experience with this device in neonatology and adult intensive care may broaden the pediatric indications to include weaning from invasive ventilation and acute asthma. As for any form of respiratory support, HFNC initiation in patients requires close monitoring, whether it be for pre- or inter-hospital transport or in the emergency department or the pediatric intensive care unit.

Severe acute viral bronchiolitis and surfactant deficiency

Acute viral bronchiolitis is a common respiratory tract infection in infants and children that often results in hospitalization, and earlier studies have suggested that it is associated with deficiency of surfactant. In this issue of The Journal, Hartmann et al from the Universidade Federal do Rio Grande do Sul, Brazil, report on a study of surfactant use in 16 infants with acute viral bronchiolitis. They show that there were markedly reduced surfactant content and function compared with 16 controls. The authors suggest that the measurement of surfactant content and function might help to identify infants with bronchiolitis who would benefit from surfactant replacement therapy.Article page 1432▶ Acute viral bronchiolitis is a common respiratory tract infection in infants and children that often results in hospitalization, and earlier studies have suggested that it is associated with deficiency of surfactant. In this issue of The Journal, Hartmann et al from the Universidade Federal do Rio Grande do Sul, Brazil, report on a study of surfactant use in 16 infants with acute viral bronchiolitis. They show that there were markedly reduced surfactant content and function compared with 16 controls. The authors suggest that the measurement of surfactant content and function might help to identify infants with bronchiolitis who would benefit from surfactant replacement therapy. Article page 1432▶ Surfactant Deficiency in Infants with Severe Acute Viral BronchiolitisThe Journal of PediatricsVol. 164Issue 6PreviewTo evaluate surfactant content and function through the lamellar body count (LBC) and stable microbubble test (SMT) in mechanically ventilated infants with severe acute viral bronchiolitis. Full-Text PDF

Surfactant Deficiency in Infants with Severe Acute Viral Bronchiolitis

To evaluate surfactant content and function through the lamellar body count (LBC) and stable microbubble test (SMT) in mechanically ventilated infants with severe acute viral bronchiolitis. Controlled cross-sectional study of 32 infants receiving mechanical ventilation: 16 with a diagnosis of acute viral bronchiolitis and 16 with normal lungs. Tracheal fluid was collected and LBC was performed in an automated cell counter. Samples were kept frozen and thawed for testing. At the time of analysis, samples were diluted in a dithiothreitol solution, vortexed for 10 seconds, and aspirated by the cell counter. SMT was performed using the Pattle technique. In the bronchiolitis group, the median (IQR) LBC was significantly lower than in the control group: 130,000 (61,250-362,250) vs. 518,000 (180,250-896,000) lamellar bodies/μL; P = .003. Median (IQR) SMT values were also significantly lower in the bronchiolitis group: 10 (2-13) vs. 400 (261-615) microbubbles/mm2; P < .001. Infants with acute viral bronchiolitis have reduced surfactant content and function. We speculate that these simple tests may be useful to identify infants with bronchiolitis who would benefit from surfactant replacement therapy.

Epidemiological and genetic characteristics associated with the severity of acute viral bronchiolitis by respiratory syncytial virus

Objectiveto assess the epidemiological and genetic factors associated with severity of acute viral bronchiolitis (AVB) by respiratory syncytial virus (RSV). Data source: the key words “bronchiolitis”, “risk factor”, “genetics” and “respiratory syn-cytial virus”, and all combinations among them were used to perform a search in the PubMed,SciELO, and Lilacs databases, of articles published after the year 2000 that included individualsyounger than 2 years of age. Data synthesis: a total of 1,259 articles were found, and their respective summaries were read. Of these, 81 were selected, which assessed risk factors for the severity of AVB, and were read in full; the 60 most relevant studies were included. The epidemiologic factors associated with AVB severity by RSV were prematurity, passive smoking, young age, lack of breastfeeding, chronic lung disease, congenital heart disease, male gender, ethnicity, viral coinfection, low weight at admission, maternal smoking during pregnancy, atopic dermatitis, mechanical ventilation in the neonatal period, maternal history of atopy and/or asthma during pregnancy, season of birth, low socioeconomic status, Down syndrome, environmental pollution, living at an altitude > 2,500 meters above sea level, and cesarean section birth. Conversely, some children with severe AVB did not present any of these risk factors. In this regard, recent studies have verified the influence of genetic factors on the severity of AVB by RSV. Polymorphisms of the TLRs, RANTES, JUN, IFNA5, NOS2, CX3CR1, ILs, and VDR genes have been shown to be associated with more severe evolution of AVB by RSV. Conclusionthe severity of AVB by RSV is a phenomenon that depends on the varying degrees of interaction among epidemiological, environmental, and genetic variables.

Epidemiological and genetic characteristics associated with the severity of acute viral bronchiolitis by respiratory syncytial virus

Objectiveto assess the epidemiological and genetic factors associated with severity of acute viral bronchiolitis (AVB) by respiratory syncytial virus (RSV). Data sourcethe key words “bronchiolitis”, “risk factor”, “genetics” and “respiratory syncytial virus”, and all combinations among them were used to perform a search in the PubMed, SciELO, and Lilacs databases, of articles published after the year 2000 that included individuals younger than 2 years of age. Data synthesisa total of 1,259 articles were found, and their respective summaries were read. Of these, 81 were selected, which assessed risk factors for the severity of AVB, and were read in full; the 60 most relevant studies were included. The epidemiologic factors associated with AVB severity by RSV were prematurity, passive smoking, young age, lack of breastfeeding, chronic lung disease, congenital heart disease, male gender, ethnicity, viral coinfection, low weight at admission, maternal smoking during pregnancy, atopic dermatitis, mechanical ventilation in the neonatal period, maternal history of atopy and/or asthma during pregnancy, season of birth, low socioeconomic status, Down syndrome, environmental pollution, living at an altitude > 2,500 meters above sea level, and cesarean section birth. Conversely, some children with severe AVB did not present any of these risk factors. In this regard, recent studies have verified the influence of genetic factors on the severity of AVB by RSV. Polymorphisms of the TLRs, RANTES, JUN, IFNA5, NOS2, CX3CR1, ILs, and VDR genes have been shown to be associated with more severe evolution of AVB by RSV. Conclusionthe severity of AVB by RSV is a phenomenon that depends on the varying degrees of interaction among epidemiological, environmental, and genetic variables.

Evolução e característica de lactantes com bronquiolite viral aguda submetidos à ventilação mecânica em uma unidade de terapia intensiva pediátrica brasileira

To describe the characteristics and the outcome of infants with acute viral bronchiolitis submitted to mechanical ventilation. We performed a retrospective study enrolling all infants (less than 12 months old) admitted with the diagnosis of acute viral bronchiolitis and submitted to mechanical ventilation in an university affiliated Brazilian pediatric intensive care unit between March, 2004 and September, 2006 (3 consecutives winters). The mechanical ventilation parameters' employed on 1st, 2nd, 3rd, 7th day and before extubation were evaluated as well as the evolution (mortality rate, presence of acute respiratory distress syndrome and the prevalence of complications). The groups were compared using the Student t test, the Mann-Whitney U test and the Chi-square test. Fifty-nine infants were included (3.8 ± 2.7 months old, 59% male), with 9.0 ± 9.4 days on mechanical ventilation. Prior mechanical ventilation, non invasive ventilation was instituted in 71% of children. Anemia was observed in 78% of the sample. In 51 infants (86.5%) the lower airway obstructive pattern was maintained up to tracheal extubation with a nil mortality and low prevalence of pneumothorax (7.8%). Acute respiratory distress syndrome occurred in 8 infants (13.5%), with higher mortality and a higher prevalence of pneumothorax (62.5%). The declining mortality in acute viral bronchiolitis is observed even in non developed regions, involving children with high rates of anemia and premature labor. The low mortality is associated with the maintenance of the lower airway obstructive pattern during the period on mechanical ventilation. The development of acute respiratory distress syndrome is associated with increased mortality and higher prevalence of complications, representing the actual challenge in the management of children with severe acute viral bronchiolitis.

Nasal continuous positive airway pressure decreases respiratory muscles overload in young infants with severe acute viral bronchiolitis

To determine the efficacy of nasal continuous positive airway pressure (nCPAP) on respiratory distress symptoms and respiratory effort in young infants with acute respiratory syncytial virus bronchiolitis. Prospective study. The paediatric intensive care unit of a university hospital. Twelve infants less than 3 months of age, with severe respiratory distress. Respiratory distress was quantified with a specific scoring system. Oesophageal pressure (Pes) was measured during spontaneous ventilation before and after nCPAP, delivered through an infant-adapted ventilator. Simultaneous recording of gastric pressure (Pgas) was performed in the five oldest patients. The respiratory distress score decreased after nCPAP, particularly accessory muscles' use and expiratory wheezing. The breathing pattern was modified, with shorter inspiratory and longer expiratory time. Pes swings and PTPes(insp), two indices of inspiratory effort, were reduced by 54 (+/-4)% and 59 (+/-5)%. PTPgas(exp), an indicator of expiratory muscles activity, was completely abolished. A significant correlation was observed between the respiratory distress score and Pes swings at baseline and after nCPAP. In young infants with severe acute respiratory syncytial virus bronchiolitis, nCPAP rapidly unloads respiratory muscles and improves respiratory distress symptoms.

Exogenous surfactant treatment for severe acute viral bronchiolitis: case report

OBJECTIVE: To describe the possible clinical and laboratory effects of exogenous surfactant instillation into the tracheal tube of a child with severe acute bronchiolitis undergoing mechanical ventilation. CASE REPORT: a 2-month-old girl with clinical diagnosis of acute viral bronchiolitis underwent mechanical ventilation. She required high positive inspiratory peak pressure (35 to 45 cmH(2)O) and high inspiratory fraction of oxygen (FiO(2) = 0.9), but showed no clinical response or improvement in the arterial blood gas analysis. An exogenous surfactant (Exosurf(R), Glaxo - 50 mg/kg) was used to facilitate the use of a less aggressive ventilatory strategy. RESULTS: Four hours after surfactant administration, it was possible to reduce the positive peak inspiratory pressure (PIP) from 35 to 30 cmH(2)O, and FiO(2) from 0.9 to 0.6; and to increase the positive end-expiratory pressure (PEEP) from 6 to 9 cmH(2)O. During this period the paO(2)/FiO(2) ratio increased from 120 to 266. At the end of 24 hours, FiO(2) could be reduced to 0.4. DISCUSSION: Surfactant inactivation may be a decisive factor in the unfavorable evolution of some severe cases of acute bronchiolitis. The tracheal instillation of exogenous surfactant, in these cases, allows us to adopt less aggressive ventilatory strategies, and promotes rapid clinical responses.