Respiratory mechanics in infants with severe bronchiolitis on controlled mechanical ventilation.

BACKGROUND: Analysis of respiratory mechanics during mechanical ventilation (MV) is able to estimate resistive, elastic and inertial components of the working pressure of the respiratory system. Our aim was to discriminate the components of the working pressure of the respiratory system in infants on MV with severe bronchiolitis admitted to two PICU's. METHODS: Infants younger than 1 year old with acute respiratory failure caused by severe bronchiolitis underwent neuromuscular blockade, tracheal intubation and volume controlled MV. Shortly after intubation studies of pulmonary mechanics were performed using inspiratory and expiratory breath hold. The maximum inspiratory and expiratory flow (QI and QE) as well as peak inspiratory (PIP), plateau (PPL) and total expiratory pressures (tPEEP) were measured. Inspiratory and expiratory resistances (RawI and RawE) and Time Constants (KTI and KTE) were calculated. RESULTS: We included 16 patients, of median age 2.5 (1-5.8) months. Bronchiolitis due to respiratory syncytial virus was the main etiology (93.8%) and 31.3% had comorbidities. Measured respiratory pressures were PIP 29 (26-31), PPL 24 (20-26), tPEEP 9 [8-11] cmH2O. Elastic component of the working pressure was significantly higher than resistive and both higher than threshold (tPEEP - PEEP) (P < 0.01). QI was significantly lower than QE [5 (4.27-6.75) v/s 16.5 (12-23.8) L/min. RawI and RawE were 38.8 (32-53) and 40.5 (22-55) cmH2O/L/s; KTI and KTE [0.18 (0.12-0.30) v/s 0.18 (0.13-0.22) s], and KTI:KTE ratio was 1:1.04 (1:0.59-1.42). CONCLUSIONS: Analysis of respiratory mechanics of infants with severe bronchiolitis receiving MV shows that the elastic component of the working pressure of the respiratory system is the most important. The elastic and resistive components in conjunction with flow profile are characteristic of restrictive diseases. A better understanding of lung mechanics in this group of patients may lead to change the traditional ventilatory approach to severe bronchiolitis.

Oxidative stress as a novel target in pediatric sepsis management.

Sepsis with secondary multisystem organ dysfunction syndrome is the leading cause of death in the pediatric intensive care unit. Increased reactive oxygen species may influence circulating and endothelial cells, contributing to inflammatory tissue injury and explaining the tissue hypoxia paradigm based on microvascular dysfunction. An impaired mitochondrial cellular oxygen utilization, rather than inadequate oxygen delivery, was claimed to play a more important role in the development of multisystem organ dysfunction syndrome. Anyway, it seems plausible that reactive oxygen species can mediate the pathophysiologic processes occurring in sepsis. However, the consensus guidelines for the management of patients with these conditions do not include the enhancement of antioxidant potential. Therefore, further investigation is needed to support interventions aimed to attenuate the severity of the systemic compromise by abrogating the mechanism of oxidative damage. Antioxidant supplementation currently in use lacks a mechanistic support. Specific pharmacologic targets, such as mitochondria or Nicotinamide Adenine Dinucleotide Phosphate-Oxidase (NADPH) oxidase system, need to be explored. Furthermore, the early recognition of oxidative damage in these seriously ill patients and the usefulness of oxidative stress biomarkers to define a cut point for more successful therapeutic antioxidant interventions to be instituted would offer a new strategy to improve the outcome of critically ill children.