Abstract PR592

Abstract

Background & Objectives: Central venous pressure (CVP) is routinely used as an indicator of hemodynamics in patients receiving surgery and intensive care. When measuring CVP in a supine position, it is necessary to adjust the location of the pressure transducer to the uppermost level of the right atrium (RA) for accurate measurement. This study was aimed to reveal the most appropriate prediction of the RA during expiratory phase by using inspiratory phase computed tomography (CT) images. Materials & Methods: The medical records of preoperative patients with non-chronic obstructive pulmonary disease who underwent CT were retrospectively reviewed. We measured all distances and ratios using CT images obtained in both the inspiratory and expiratory phases. The anterior posterior (AP) diameter of the thorax was measured at the mid-sternum level, while the largest vertical distance from the uppermost RA level to the back surface was also measured as RA height. RA thorax ratio was defined as the ratio of RA height to AP diameter of the thorax. (Figure 1) We attempted to predict the expiratory RA height using the following 2 formulae for comparison; formula 1, Predicted expiratory RA height = overall average inspiratory RA thorax ratio x expiratory AP diameter of thorax, and formula 2, Predicted expiratory RA height = individual inspiratory RA thorax ratio x expiratory AP diameter of thorax. For statistical analyses, we used linear regression and Bland-Altman analyses. P less than 0.05 was considered statistically significant. Results: 15 patients (mean age 48.1±24.7 years, 8 males) were subjected. There was a significant correlation between RA height and AP diameter of the thorax in both phases (inspiratory phase: R2=0.56, expiratory phase: R2=0.68). Additionally, the coefficient of both regression lines were approximately the same as 0.75. The RA thorax ratio for the inspiratory and expiratory phases also showed a significant correlation R2=0.80) In a Bland-Altman plot with Formula 1, the fixed bias was -0.34 mm and 95% limit of agreement ranged from -19.44 to 18.75 mm, whereas those were -1.31 mm and -9.72 to 7.10 mm with Formula 2.Conclusion: Because CT is commonly taken in expiratory phase, the RA thorax ratio in expiratory phase is unknown in most of the patients. Our findings showed that the RA thorax ratio was not changed by respiratory cycle. Therefore, the RA height in expiratory phase could be predicted by the RA thorax ratio in inspiratory phase and thickness of thorax in expiratory phase. Additionally, the predicted value of Formula 2 showed better agreement, indicating that the RA thorax ratio should be obtained from each individual to predict the RA height precisely. Disclosure of Interest: None declared