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Kaczka, David

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Kaczka

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David

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Kaczka, David
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    Observational Study of Changes in Epidural Pressure and Elastance During Epidural Blood Patch in Obstetric Patients
    (Elsevier BV, 2014) Pratt, Stephen; Kaczka, David; Hess, Philip
    Background During an epidural blood patch, we inject blood until the patient describes mild back pressure, often leading to injection of more than 20 mL of blood. We undertook this study to measure the epidural pressures generated during an epidural blood patch and to identify the impact of volume on epidural elastance in obstetric patients. Methods This study was performed in postpartum patients who presented for an epidural blood patch with symptoms consistent with a postdural puncture headache. After identification of the epidural space using loss of resistance to air or saline, we measured static epidural pressure after each 5-mL injection of blood. Models were then fitted to the data and the epidural elastance and compliance calculated. Results Eighteen blood patches were performed on 17 patients. The mean final volume injected was 18.9 ± 7.8 mL [range 6 to 38 mL]. The mean final pressure generated was 13.1 ± 13.4 mmHg [range 2 to 56 mmHg]. A curvilinear relationship existed between volume injected and pressure, which was described by two models: (1) pressure = 0.0254 × (mL injected)2 + 0.0297 × mL, or (2) pressure = 0.0679 × mL1.742. The value for r2 was approximately 0.57 for both models. We found no correlation between the final pressure generated and the success of the EBP. Conclusions We found a curvilinear relationship between the volume of blood injected during an epidural blood patch and the pressure generated in the epidural space. However, there was a large variation in both the volume of blood and the epidural pressure generated. The clinical importance of this finding is not known. A larger study would be required to demonstrate whether pressure is a predictor of success.
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    Analysis of Regional Mechanics in Canine Lung Injury Using Forced Oscillations and 3D Image Registration
    (Springer US, 2011) Kaczka, David; Cao, Kunlin; Christensen, Gary E.; Bates, Jason H. T.; Simon, Brett A
    Acute lung injury is characterized by heterogeneity of regional mechanical properties, which is thought to be correlated with disease severity. The feasibility of using respiratory input impedance (\(Z_{rs}\)) and computed tomographic (CT) image registration for assessing parenchymal mechanical heterogeneity was evaluated. In six dogs, measurements of (\(Z_{rs}\)) before and after oleic acid injury at various distending pressures were obtained, followed by whole lung CT scans. Each (\(Z_{rs}\)) spectrum was fit with a model incorporating variable distributions of regional compliances. CT image pairs at different inflation pressures were matched using an image registration algorithm, from which distributions of regional compliances from the resulting anatomic deformation fields were computed. Under baseline conditions, average model compliance decreased with increasing inflation pressure, reflecting parenchymal stiffening. After lung injury, these average compliances decreased at each pressure, indicating derecruitment, alveolar flooding, or alterations in intrinsic tissue elastance. However, average compliance did not change as inflation pressure increased, consistent with simultaneous recruitment and strain stiffening. Image registration revealed peaked distributions of regional compliances, and that small portions of the lung might undergo relative compression during inflation. The authors conclude that assessments of lung function using (\(Z_{rs}\)) combined with the structural alterations inferred from image registration provide unique but complementary information on the mechanical derangements associated with lung injury.