IntroductionDiagnostic coronary angiography utilises radiographic contrast media to delineate epicardial coronary lesions and assess left ventricular function. While contrast media is essential for the radiographic visualisation of coronary vessels, there are certain risks and complications associated with its use. One such complication is contrast-induced nephropathy (CIN). CIN is a life-threatening dose-dependent reaction and is commonly defined as a decrease in renal function 24-48 hours after contrast media administration, with a rise in serum creatinine levels of more than 25% from the baseline (or an absolute increase greater than 0.5 mg/dL) three to five days after the procedure. [1][2][3][4][5][6][7][8][9] Preventative measures for CIN in cardiovascular procedures include pre-hydration, prophylactic administration of N-acetylcysteine and utilisation of iso-osmolar/hypo-osmolar contrast media. However, reducing the volume of contrast media within the procedure was found to be the most effective. [10][11][12][13][14] Cigarroa, et al. 15 and Freeman, et al. 16 both investigated the significance of an adjusted volume of contrast media to patient's body weight and serum creatinine level (maximum radiographic contrast dose (MRCD)) in relation to the occurrence of CIN. CIN developed in 2% of cases when the calculated MRCD for a group of patients was not exceeded, and a 15-fold increase in incidence for a group where MRCD was exceeded. Similarly Rihal, et al. 12 reported a 12% increase in the risk of nephropathy with each 100 mL administered to the patient. As CIN has been found to be the third leading cause of acute renal failure in patients (10% of all admitted cases), it is essential that contrast load is kept to a minimum in any examinations requiring contrast media. 3,17 Coronary angiography can be performed using either singleplane or biplane imaging equipment. Single-plane imaging involves the use of one x-ray tube to acquire images at different angles and requires a separate injection of contrast for each cine angiography run. Biplane imaging utilises two x-ray tubes and is capable of acquiring two simultaneous projections with a single contrast injection. Therefore, it is assumed that contrast load will not only be reduced, but screening time and overall procedural time will be shorter.In biplane imaging, the screening time is inclusive of the total fluoroscopy and cine angiography time for both planes. The screening time should therefore be shorter for biplane imaging than single-plane imaging as it acquires two images simultaneously. Additionally, as the setup of the two C-arms require less movement throughout the procedure, the use of biplane equipment would accordingly assist in reducing procedural time when compared to single-plane imaging. Furthermore, because the runs are calculated from each individual plane, biplane should result in a slightly greater number of cine angiography runs than single-plane imaging. Where single-plane will complete the nine standard projections, biplane will produce ...

Both diaphragm shape and tension contribute to transdiaphragmatic pressure, but of the three variables, tension is most difficult to measure. We measured transdiaphragmatic pressure and the global shape of the in vivo canine diaphragm and used principles of mechanics to compute the tension distribution. Our hypotheses were that 1) tension in the active diaphragm is nonuniform with greater tension in the central tendon than in the muscular regions; 2) maximum tension is essentially oriented in the muscle fiber direction, whereas minimum tension is orthogonal to the fiber direction; and 3) during submaximal activation change in the in vivo global shape is small. Metallic markers, each 2 mm in length, were implanted surgically on the peritoneal surface of the diaphragm at 1.5-to 2.0-cm intervals along the muscle bundles at the midline, ventral, middle, and dorsal regions of the left costal diaphragm and along a muscle bundle of the crural diaphragm. Postsurgery, a biplane videofluoroscopic system was used to determine the in vivo threedimensional coordinates of the markers at end expiration and end inspiration during quiet breathing as well as at end-inspiratory efforts against an occluded airway at lung volumes of functional residual capacity and at one-third maximum inspiratory capacity increments in volume to total lung capacity. A surface was fit to the marker locations using a two-dimensional spline algorithm. Diaphragm surface was modeled as a pressurized membrane, and tension distribution in the active diaphragm was computed using the ANSYS finite element program. We showed that the peak of the diaphragm dome was closer to the ventral surface than to the dorsal surface and that there was a depression or valley in the crural region. In the supine position, during inspiratory efforts, the caudal displacement of the dorsal region of the diaphragm was greater than that of the dome, and the valley along the crural diaphragm was accentuated. In contrast, at lower lung volumes in the prone posture, the caudal displacement of the dome was greater than that of the crural region. At end of inspiration, transdiaphragmatic pressure was ϳ6.5 cmH2O, and tensions were nonuniform in the diaphragm. Maximum principal stress 1 of central tendon was found to be greater than 1 of the costal region, and that was greater than 1 of the crural region, with values of 14 -34, 14 -29, and 4 -14 g/cm, respectively. The corresponding data of the minimum principal stress 2 were 9 -18, 3-9, and 0 -1.5 g/cm, respectively. Maximum principal tension was approximately parallel to the muscle fibers, whereas minimum tension was essentially orthogonal to the longitudinal direction of the muscle fibers. In the muscular region, 1 was ϳ3-fold 2, whereas in the central tendon, 1 was only ϳ1.5-fold 2.respiratory muscle mechanics; chest wall mechanics; finite element modeling; membrane mechanics THE SHAPE OF THE DIAPHRAGM is vital for converting muscle tension into transdiaphragmatic pressure (P di ) and muscle shortening into volume displacement. It i...

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