Strain-specific differences in lung tissue viscoelasticity of mechanically ventilated infant Sprague-Dawley and Wistar rats.

Rats are often used in ventilator-induced lung injury (VILI) models. However, strain-specific susceptibility for VILI has not been elucidated yet. The aim of this study was to demonstrate strain-specific differences in VILI in infant Sprague-Dawley and Wistar rats. VILI was compared in 2-wk-old pups after 8 h of protective or injurious ventilation. Pups were ventilated with tidal volumes (VT) of ∼7 mL/kg and positive end-expiratory pressures (PEEP) of 6 cmH2O (VT7 PEEP6) or with VT of ∼21 mL/kg and PEEP 2 cmH2O (VT21 PEEP2). Interleukin-6, macrophage inflammatory protein-2 (MIP-2), inflammatory cells, and albumin in bronchoalveolar lavage fluid (BALF); histology; and low-frequency forced oscillation technique (LFOT) and pressure-volume (PV) maneuvers were assessed. Alveolar macrophages, neutrophils, and MIP-2 derived from BALF revealed more pronounced VILI after VT21 PEEP2 in both strains. LFOT and PV analyses demonstrated rat strain-specific differences both at baseline and particularly in response to VT21 PEEP2 ventilation. Sprague-Dawley rats showed higher airway and tissue resistance and elastance values with no difference in hysteresivity between ventilation strategies. Wister rats challenged by VT21 PEEP2 experienced significantly more energy dissipation when compared with VT7 PEEP6 ventilation. In conclusion, both rat strains are useful for VILI models. The degree of VILI severity depends on ventilation strategy and selected strain. However, fundamental and time-dependent differences in respiratory system mechanics exist and reflect different lung tissue viscoelasticity. Hence, strain-specific characteristics of the respiratory system need to be considered when planning and interpreting VILI studies with infant rats.

Individualized lung recruitment during high-frequency ventilation in preterm infants is not associated with lung hyperinflation and air leaks.

UNLABELLED: Lung recruitment during high-frequency ventilation (HFV) in preterm infants with respiratory distress syndrome (RDS) has been associated with an increased risk of lung hyperinflation and air leaks. Individualizing the lung recruitment procedure to the severity of lung disease of each patient might reduce these risks. In this prospective cohort study, we evaluated chest X-ray (CXR) characteristics during individualized oxygenation-guided lung recruitment with HFV in preterm infants with RDS, before and after surfactant therapy. Two pediatric radiologists scored radiolucency, the presence of lung hyperinflation, and/or air leaks following lung recruitment during HFV in 69 infants before and 39 infants after surfactant treatment. Following lung recruitment, the median radiolucency score was 2, with 44 (64 %) infants having a score ≤2. Only mild to moderate hyperinflation was seen in 13 (19 %) infants, with no air leaks. After the surfactant, the radiolucency score improved in 62 % of 39 paired CXRs (p < 0.001). Mild to moderate hyperinflation was seen in nine (24 %) patients. During the entire admission, only four (6 %) of the patients developed air leaks. CONCLUSION: The risk of significant hyperinflation and air leaks is low when using an individualized oxygenation-guided recruitment procedure during HFV in preterm infants with RDS. WHAT IS KNOWN: • Lung recruitment during high-frequency ventilation in preterm infants with respiratory distress syndrome is associated with an increased risk of lung hyperinflation and air leaks. What is New: • The risk of lung hyperinflation and air leaks is low when using an individualized oxygenation-guided lung recruitment procedure during high-frequency ventilation in preterm infants with respiratory distress syndrome.

Efectos del sevoflurano en la lesión pulmonar inducida por la ventilación mecánica en un modelo experimental de pulmón sano / Effects of sevoflurane on ventilator induced lung injury in a healthy lung experimental model

Introducción y objetivo. El daño pulmonar inducido por la ventilación mecánica (VILI) provoca una respuesta inflamatoria sistémica, con elevación en sangre y tejidos de IL-1, IL-6 y TNF-α. Conocidos los efectos citoprotectores de sevoflurano en diferentes modelos experimentales, este podría tener un comportamiento similar ante el VILI. El objetivo de este estudio es valorar el efecto de sevoflurano en el VILI. Material y métodos. Estudio experimental, prospectivo, controlado y aleatorizado. Se utilizaron 20 ratas hembra. Los animales fueron ventilados mecánicamente sin sevoflurano en el grupo control y con sevoflurano al 3% en el grupo tratado (grupo SEV). Se provocó el VILI mediante una presión inspiratoria máxima de 35 cmH2O sin presión positiva al final de la expiración durante 20 min (tiempo LESIÓN). Después, los animales fueron ventilados 30 min con una presión inspiratoria máxima de 12 cmH2O y 3 cmH2O de presión positiva al final de la expiración (tiempo 30 min POSLESIÓN). Se registraron la frecuencia cardiaca, las presiones arteriales sistólica, diastólica y media, el pH, la PaO2 y la PaCO2. Se analizó la ratio peso húmedo/seco del tejido pulmonar. Resultados. No existieron diferencias estadísticamente significativas en los parámetros gasométricos ni en la frecuencia cardiaca entre los 2 grupos en estudio. La PAM fue significativamente mayor en el grupo control, pero dentro de límites clínicos normales. El porcentaje de edema pulmonar y las concentraciones de TNF-α e IL-6 en tejido pulmonar en el grupo de animales ventilados con sevoflurano fueron menores que en el grupo control. Conclusiones. Sevoflurano atenúa el VILI en pulmón previamente sano, en un modelo experimental de VILI subclínico en ratas (AU)

Introduction and objective. Ventilator-induced lung injury (VILI) causes a systemic inflammatory response in tissues, with an increase in IL-1, IL-6 and TNF-α in blood and tissues. Cytoprotective effects of sevoflurane in different experimental models are well known, and this protective effect can also be observed in VILI. The objective of this study was to assess the effects of sevoflurane in VILI. Material and methods. A prospective, randomized, controlled study was designed. Twenty female rats were studied. The animals were mechanically ventilated, without sevoflurane in the control group and sevoflurane 3% in the treated group (SEV group). VILI was induced applying a maximal inspiratory pressure of 35 cmH2O for 20 min without any positive end-expiratory pressure for 20 min (INJURY time). The animals were then ventilated 30 min with a maximal inspiratory pressure of 12 cmH2O and 3 cmH2O positive end-expiratory pressure (time 30 min POST-INJURY), at which time the animals were euthanized and pathological and biomarkers studies were performed. Heart rate, invasive blood pressure, pH, PaO2, and PaCO2 were recorded. The lung wet-to-dry weight ratio was used as an index of lung edema. Results. No differences were found in the blood gas analysis parameters or heart rate between the 2 groups. Blood pressure was statistically higher in the control group, but still within the normal clinical range. The percentage of pulmonary edema and concentrations of TNF-α and IL-6 in lung tissue in the SEV group were lower than in the control group. Conclusions. Sevoflurane attenuates VILI in a previous healthy lung in an experimental subclinical model in rats (AU)

Evaluación del cumplimiento de un protocolo de prevención de Neumonía asociada a Ventilación mecánica en una UCI polivalente / Assessment of compliance of a pneumonia prevention protocol associated mechanical ventilation in a polyvalent ICU

Objetivos: 1.Analizar el cumplimiento del protocolo mediante el registro del 80% de los cuidados de enfermería. 2. Describir la evolución de la densidad de incidencia de NAVM durante el periodo del estudio. Metodología: Estudio descriptivo retrospectivo de los años 2009, 2010 y 2011. Se registró la realización de los cuidados incluidos en la prevención de NAVM en todos los pacientes en tratamiento con ventilación mecánica (VM) >24 horas, considerando que estaban cumplidos si el registro era = 80%. Se calculó el número de episodios NAVM por 1000 días de VM en el periodo del estudio. Resultados: Se incluyeron un total de 94 pacientes. El cumplimiento de las medidas fue superior al 80% excepto en la valoración de la escala de Ramsay. El número de episodios de NAV por año fue 12,8 episodios por 1000 días de VM en 2008 y tras la implantación del protocolo fue de 4,57 en 2009, 6,83 en 2010 y 2,71 en 2011. Conclusiones: 1. La frecuencia de registro de los cuidados ha sido buena. Para la mejora del registro de la valoración de la sedación, se hace necesaria la posibilidad de implantar un protocolo para el destete. 2. La incidencia de NAVM ha descendido tras la implantación del protocolo (AU)

Aims: 1. Analyze compliance of 80% of the protocol. 2. Describe the evolution of the density of VAP during the study period. Methodology: Retrospective and descriptive study in years 2009, 2010 and 2011. They record the delivery of care including the prevention of VAP in all patients on mechanical ventilation (MV) >24 hours, considering they were met if the record was = 80%. We calculated the number of episodes of VAP per 1000 days of VM in the study period. Results: A total of 94 patients were included. The performance of all measures was over 80% less except Ramsay assessment scale. The numbers of episodes of VAP per year were 12.8 for 1000 days of mechanical ventilation in 2008 and then implementation measures were 4.57 episodes in 2009, 6.83 episodes in 2010 and 2.71 episodes in 2011. Conclusions: Frequency of care record has been good. To improve the record of the assessment of sedation, it is necessary the possibility of implementing a protocol for weaning. 2. The incidence of VAP has declined after implementation of the protocol (AU)