Respiratory support in children

Respiratory failure is defined by the inability of the respiratory system to adequately deliver oxygen or remove carbon dioxide from the pulmonary circulation resulting in hypoxemia, hypercapnia or both. A wide variety of disease processes can lead to respiratory failure in children. Multiple interventions can support the paediatric patient with respiratory failure, from simple oxygen delivery devices to high frequency oscillatory ventilation and extracorporeal membrane oxygenation. This article will review available devices to improve oxygenation and ventilation, their advantages and disadvantages, and help guide physicians in the management of children with respiratory failure.     

LONG‐TERM FOLLOW UP OF PATIENTS WITH SMALL GASTROINTESTINAL STROMAL TUMORS IN THE STOMACH USING ENDOSCOPIC ULTRASONOGRAPHY‐GUIDED FINE‐NEEDLE ASPIRATION BIOPSY

Background: Gastrointestinal stromal tumors (GIST) are one of the most common mesenchymal tumors of the gastrointestinal tract. GIST are defined by positive immunohistochemical staining for KIT or CD34 and thus are generally diagnosed after surgery. Because small GIST are rarely diagnosed before surgery, the clinical course of these small tumors is not clear. The aim of the present study was to follow changes in size and configuration of small GIST that were pathologically confirmed using endoscopic ultrasonography‐guided fine‐needle aspiration biopsy (EUS‐FNAB). Methods: Between July 1997 and December 2003, 16 tumors in 16 patients (10 men and 6 women) with an immunohistochemical diagnosis of GIST were regularly followed in our hospital. The median patient age when EUS‐FNAB was performed was 62 years (range 26–82 years) and the median follow‐up period was 4.9 years (range 0.5–9.6 years). Results: Fourteen tumors showed no remarkable changes in size and shape during follow up compared with the initial diagnosis. Two tumors enlarged: one tumor approximately doubled its diameter in 8 years and the other tumor increased from 1.8 cm at diagnosis to up to 10 cm after only 2 years. Doubling time of the latter tumor was calculated as 3.1 months. Conclusions: We conclude that EUS‐FNAB might be a good modality for final diagnosis of GIST without surgery, and that GIST without rapid growth on follow up can be endoscopically followed.     

Relative permeability of nasal, tracheal, and bronchoalveolar mucosa to macromolecules in rats exposed to ozone

Nasal, tracheal and bronchoalveolar injuries resulting from acute ozone exposure of rats were investigated by permeability changes. 99mTc-labeled diethylenetriaminepentaacetate (DPTA) and 125I-labeled bovine serum albumin (BSA) were selectively instilled into localized airway regions of anesthetized rats exposed to 0.8 ppm 03 or clean air for 2 h. Transmucosal transfer of the radiolabeled tracers was detected by counting the radioactivity in blood samples collected at short postinstillation time intervals. Permeability measurements were made on d 0, 1, and 2 after O3 exposure to analyze the extent and persistence of tissue injury in the nasal, tracheal, and bronchoalveolar regions. Normal mucosal permeability was low in nose, intermediate in bronchoalveolar zone, and high in trachea. The O3-related injury, reflected by elevated permeability, was substantial in the trachea and bronchoalveolar zone but was minimal in the nose immediately after the exposure. Abnormal permeability persisted for less than 24 h in the trachea but for more than 24 h in the bronchoalveolar zone. The results are consistent with the properties of O3 of causing greater injury in the smaller airways and the alveolar zone than in the trachea.     

IEC-18, a nontransformed small intestinal cell line for studying epithelial permeability.

Small intestinal epithelium is leaky and allows permeation of hydrophilic molecules of various sizes. Passively absorbed hydrophilic permeability probes have been shown to permeate across intestinal epithelium mainly through the paracellular pathways. In this study we introduce microporous filter-grown IEC-18 epithelial cells, a nontransformed small intestinal cell line, as a in vitro model of intestinal epithelium for the study of epithelial permeability. IEC-18 cells, originally derived from native rat ileal crypts, form confluent epithelium when grown on hydrated collagen-coated Millicell-CM permeable inserts (Millipore Corp., Bedford, Mass.). With scanning and transmission electron microscopy, the presence of tight junctions and desmosomes between cells and the development of microvilli at the apical surface were confirmed. Immunofluorescent labeling of ZO-1 proteins and desmoplakins verified the presence of tight-junctional proteins (ZO-1) and desmosomes in the intercellular junctions of confluent IEC-18 epithelium. The net electrical resistance of IEC-18 epithelium (28 omega-cm2) was similar to resistance values obtained from small intestinal tissue with (50 to 100 omega-cm2) or without (20 to 45 omega-cm2) muscularis and serosal layers. Assessment of mannitol and dextran permeation revealed early "maturation" of paracellular pathway, with increasing restriction of permeation to both probes through day 4. Resistance across IEC-18 epithelium also reached plateau levels between 4 and 7 days. Permeability studies with various probes indicate that cross-sectional diameter rather than molecular weight of the probe is the important determinant of permeation rate. IEC-18 epithelium selectively restricted the permeation of probes proportional to probe size; permeation of larger probes such as albumin was negligible. We conclude that cultured IEC-18 epithelial cells, because of their native crypt origin, similarity in resistance to small intestinal epithelia, retention of ability to differentiate into villus-like enterocytes, and permeability characteristics, are a useful model of intestinal epithelium for the study of permeability and paracellular transport.