Randomized controlled trial comparing nasal intermittent positive pressure ventilation and nasal continuous positive airway pressure in premature infants after tracheal extubation / Estudo controlado e randomizado entre uso de ventilação positiva intermitente e pressão positiva contínua em vias aéreas em recém-nascidos prematuros após a extubação traqueal

Summary Objective: To analyze the frequency of extubation failure in premature infants using conventional mechanical ventilation (MV) after extubation in groups subjected to nasal intermittent positive pressure ventilation (nIPPV) and continuous positive airway pressure (nCPAP). Method: Seventy-two premature infants with respiratory failure were studied, with a gestational age (GA) ≤ 36 weeks and birth weight (BW) > 750 g, who required tracheal intubation and mechanical ventilation. The study was controlled and randomized in order to ensure that the members of the groups used in the research were chosen at random. Randomization was performed at the time of extubation using sealed envelopes. Extubation failure was defined as the need for re-intubation and mechanical ventilation during the first 72 hours after extubation. Results: Among the 36 premature infants randomized to nIPPV, six (16.6%) presented extubation failure in comparison to 11 (30.5%) of the 36 premature infants randomized to nCPAP. There was no statistical difference between the two study groups regarding BW, GA, classification of the premature infant, and MV time. The main cause of extubation failure was the occurrence of apnea. Gastrointestinal and neurological complications did not occur in the premature infants participating in the study. Conclusion: We found that, despite the extubation failure of the group of premature infants submitted to nIPPV being numerically smaller than in premature infants submitted to nCPAP, there was no statistically significant difference between the two modes of ventilatory support after extubation.

Resumo Objetivo: analisar a frequência de falha da extubação em recém-nascidos pré-termo (RNPT) em uso de ventilação mecânica (VM) convencional após a extubação traqueal nos grupos submetidos à ventilação por pressão positiva intermitente por via nasal (nIPPV) e pressão positiva contínua em vias aéreas (nCPAP). Método: foram estudados 72 RNPT portadores de insuficiência respiratória, com idade gestacional (IG) ≤ 36 semanas e peso de nascimento (PN) > 750 g, que necessitaram de entubação traqueal e ventilação mecânica. O estudo foi controlado e randomizado a fim de garantir a aleatoriedade na escolha dos integrantes dos grupos. A randomização foi realizada no momento da extubação por meio de envelopes selados. Falha da extubação foi definida como necessidade de reentubação e ventilação mecânica durante as primeiras 72 horas após a extubação. Resultados: entre os 36 RN randomizados para nIPPV, seis (16,6%) apresentaram falha de extubação em comparação a 11 (30,5%) dos 36 RN randomizados para nCPAP. Não houve diferença estatística entre os dois grupos de estudo em relação a PN, IG, classificação do RN e tempo de VM. A principal causa de falha da extubação foi a ocorrência de apneia. Complicações gastrointestinais e neurológicas não ocorreram nos RNPT participantes do estudo. Conclusão: constatamos que no grupo dos RNPT submetidos à nIPPV, apesar da falha da extubação ser numericamente menor que nos RNPT submetidos à nCPAP, não houve diferença estatisticamente significante entre os dois modos de suporte ventilatório após a extubação.

Pulmonary surfactants and their role in pathophysiology of lung disorders.

Surfactant is an agent that decreases the surface tension between two media. The surface tension between gaseous-aqueous interphase in the lungs is decreased by the presence of a thin layer of fluid known as pulmonary surfactant. The pulmonary surfactant is produced by the alveolar type-II (AT-II) cells of the lungs. It is essential for efficient exchange of gases and for maintaining the structural integrity of alveoli. Surfactant is a secretory product, composed of lipids and proteins. Phosphatidylcholine and phosphatidylglycerol are the major lipid constituents and SP-A, SP-B, SP-C, SP-D are four types of surfactant associated proteins. The lipid and protein components are synthesized separately and are packaged into the lamellar bodies in the AT-II cells. Lamellar bodies are the main organelle for the synthesis and metabolism of surfactants. The synthesis, secretion and recycling of the surfactant lipids and proteins is regulated by complex genetic and metabolic mechanisms. The lipid-protein interaction is very important for the structural organization of surfactant monolayer and its functioning. Alterations in surfactant homeostasis or biophysical properties can result in surfactant insufficiency which may be responsible for diseases like respiratory distress syndrome, lung proteinosis, interstitial lung diseases and chronic lung diseases. The biochemical, physiological, developmental and clinical aspects of pulmonary surfactant are presented in this article to understand the pathophysiological mechanisms of these diseases.