Ventilator-associated pneumonia surveillance using two methods.

BACKGROUND: Ventilator-associated pneumonia surveillance is used as a quality indicator due to concerns that some cases may be preventable and may contribute to mortality. Various surveillance criteria exist for the purposes of national reporting, but a large-scale direct comparison has not been conducted. METHODS: A prospective cohort study applied two routinely used surveillance criteria for ventilator-associated pneumonia from the European Centre for Disease Control and the American Centers for Disease Control to all patients admitted to two large general intensive care units. Diagnostic rates and concordance amongst diagnostic events were compared. FINDINGS: A total of 713 at-risk patients were identified during the study period. The European surveillance algorithm returned a rate of 4.6 cases of ventilator-associated pneumonia per 1000 ventilation days (95% confidence interval 3.1-6.6) and the American surveillance system a rate of 5.4 (3.8-7.5). The concordance between diagnostic events was poor (Cohen's Kappa 0.127 (-0.003 to 0.256)). CONCLUSIONS: The algorithms yield similar rates, but the lack of event concordance reveals the absence of inter-algorithm agreement for diagnosing ventilator-associated pneumonia, potentially undermining surveillance as an indicator of care quality.

Ballistic and snake photon imaging for locating optical endomicroscopy fibres.

We demonstrate determination of the location of the distal-end of a fibre-optic device deep in tissue through the imaging of ballistic and snake photons using a time resolved single-photon detector array. The fibre was imaged with centimetre resolution, within clinically relevant settings and models. This technique can overcome the limitations imposed by tissue scattering in optically determining the in vivo location of fibre-optic medical instruments.

Endoscopic sensing of alveolar pH.

Previously unobtainable measurements of alveolar pH were obtained using an endoscope-deployable optrode. The pH sensing was achieved using functionalized gold nanoshell sensors and surface enhanced Raman spectroscopy (SERS). The optrode consisted of an asymmetric dual-core optical fiber designed for spatially separating the optical pump delivery and signal collection, in order to circumvent the unwanted Raman signal generated within the fiber. Using this approach, we demonstrate a ~100-fold increase in SERS signal-to-fiber background ratio, and demonstrate multiple site pH sensing with a measurement accuracy of ± 0.07 pH units in the respiratory acini of an ex vivo ovine lung model. We also demonstrate that alveolar pH changes in response to ventilation.