Category Archives: Lung injury

Spectroscopic approach to capillary-alveolar membrane damage: APPENDIX (2)

Lung injury

The amount of HES in the fluids varied from 0.03 to 3 |ig/mL. For cross-validation of the training set, the leave-one-out method was applied, which is commonly used for evaluating the prediction ability of training processes. It is performed by sequentially removing a single spectrum from the training set, then training the classifier on the remaining spectra. Prediction is made for that single test spectrum. This process is repeated for each spectrum in the training set, and the classifier returned to the training set after each test so that the set remains the same size. ventolin inhalers

Spectroscopic approach to capillary-alveolar membrane damage: APPENDIX (1)

Lung injury

Feature space reduction: A problem when applying linear disciminant analysis to IR spectra is dimensionality. Generally, the spectra to be analyzed consist of many attributes (number of data points) compared with a relatively small number of patients, which form a sparse set in a high-dimension. To circumvent this, an ‘attribute selection’ methodology for spectral feature selection was used, that reduces the dimension (number of data points) by selecting certain subregions in the spectral range of interest that contain the most diagnostic information for the classification. buy levaquin online

Spectroscopic approach to capillary-alveolar membrane damage: CONCLUSIONS (2)

Spectral normalization: A major problem for the classification of bronchial washing spectra is the large variation in absorption intensities due to the unknown dilution factor involved in sample collection. Therefore, the influence of this unknown dilution factor must be eliminated. One way to address this problem is band-area normalization, which is based on an integration method. First, one has to define an area that remains constant in the spectroscopic region of interest so that every spectrum can be ra-tioed to this area; thus, a fraction factor is obtained. buy ampicillin

Spectroscopic approach to capillary-alveolar membrane damage: CONCLUSIONS (1)

Lung injury

The IR-bronchial washing assay method is useful for determining the pulmonary leakage in ARDS, and is particularly sensitive for evaluating the pulmonary leakage in patients who have ALI – the early stage of ARDS. This makes it especially important for supportive treatment. In contrast with other methods used to determine pulmonary microvas-cular permeability, the IR-based HES assay uses no radioactive tracers and requires little sample preparation. flovent inhaler

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (7)

The IR-bronchial washing assay represents a novel diagnostic methodology to the microvascular injury-induced pulmonary edema. However, the method is only valid over a certain period following HES infusion. Over time, HES is broken down into smaller size molecules, and, therefore, the specificity of the method is inevitably lost. Clinical pharmacokinetic and pharmacodynamic studies showed that, over a 12 h period, the average size of infused PENTASPAN (200/0.5 HES) is approximately 11.28 nm , which should still restrict the molecules within the pulmonary capillaries.

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (6)

Lung injury

Although the interstitial HES level depends on the HES level in the circulatory system, the appearance of HES in a patient’s plasma and bronchial washings exhibits a phase difference (ie, a time course difference). Generally, infused HES takes a very short time to flow into most organs in the body; however, the time for HES to infiltrate the inter-stitium from capillaries is much longer than that in the circulatory system. In addition, HES in the circulatory system has a much shorter half-life than in the interstitium, because alpha-amylases present in the tissue and in the circulation act at different rates. buy ortho tri-cyclen

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (5)

Classification of pulmonary HES leakage in a patient population: The clinical data and HES leakage determined for the IR-bronchial washing assay are given in Table 1. Using the criteria of the consensus committee from the report of the American-European Consensus Conference on ARDS , a comparison can now be made between the clinical PaO2/FiO2 values and the HES leakage as determined from the IR spectra. Patients (n=55) with PaO2/FiO2 less than 300 mmHg (which included both ARDS and ALI patients), were placed in the injury group, while patients (n=12) with PaO2/FiO2 greater than 300 mmHg were placed in the risk group.

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (4)

The patient died four days postinjury. Autopsy histology showed acute diffuse alveolar damage with hyaline membranes and superimposed bronchopneumonia (Figure 3). Frozen autopsy tissue was prepared for IR microscopic examination as 10 |u,m thin unstained sections. The thin section was placed onto a calcium fluoride window and allowed to dry. A spectrometer equipped with a 15x objective microscope (Bruker Optik, Karlsruhe, Germany) was used for IR pathological examination.

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (3)

IR pathology of pulmonary HES leakage: A demonstration of the pulmonary leakage in an ARDS patient was perfo-med by IR microscopy using autopsy material from a 49-year-old male who presented to the trauma service at the Health Sciences Centre, Winnipeg, Manitoba. The patient was involved in a motor vehicle accident in which a tractor-trailer rolled over him, and he sustained a fractured pelvis with a significant retroperitoneal hematoma. Over the next 48 h, the patient developed clinical signs of ALI/ARDS. He received antibiotics, ventilatory support and continuous venovenous hemodialysis. PENTASPAN was administered for oncotic manipulation. The IR spectra of the bronchial washings, collected 3 h after infusion of PENTASPAN, contained HES.

Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (2)

Lung injury

The alveolar HES concentration depends on the levels of circulating HES, as well as on the pulmonary capillary permeability and surface area. IR spectra provide a simple means of grossly estimating the leakage of the pulmonary vasculature. In a patient with no apparent lung injury, the alveolar HES concentration differs markedly from the plasma HES loading (Figure 1). In a healthy lung, only a very low molecular weight fraction of infused HES would be expected to diffuse between the alveolar and intravascu-lar space.

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