Competition for Intrathoracic Space Reduces Lung Capacity in Patients With Chronic Heart Failure: Population Characteristics
The TTC volume (TTCV) was determined as follows: (1) the posteroanterior and lateral view-digitized tracings were divided vertically into five sections, with the upper two sections equally divided into 2.75-cm segments, and the third and fourth sections equally divided between the most superior border of the diaphragm and lower border of the second section; (2) the fifth section included the region from the dome of the diaphragm to the insertion of the diaphragm with the rib cage; (3) and the volume of each elliptical cylindroid was calculated using the following formula:
TTCV = (1/4то) X Dx X D2 X D3
where D1 is the width across the posteroanterior view, D2 is the depth from the lateral view, and D3 is the height of the posteroanterior view. Total thoracic volume was defined as the sum of each of the individual segment volumes (Fig 1). in detail
Total cardiac volume was calculated using the following formula:
cardiac volume = (1/6to) X Dj X D2 X D3
where D1 is the long diameter measured by establishing the longest line from the junction of the superior venous pedicle with the right atrium to the apex of the left ventricle from the posteroanterior view of the cardiac silhouette, D2 is the transverse diameter defined as the sum of two perpendicular lines extended from D1 to the furthest points of the left and right ventricular borders, and D3 is the depth of the cardiac silhouette defined as the longest diameter on the lateral view approximately perpendicular to D1 (Fig 1).
Total diaphragmatic volume was calculated using the following equation:
diaphragmatic volume = (то/6) X Dx X D2 X D3
where D1 is the distance from the base of the of the posteroan-terior view to the peak of the left diaphragm dome, D2 is the distance from the base of the posteroanterior view to the peak of the right diaphragm dome, and D3 is the width of the base of the lateral view (Fig 1). Total pulmonary blood and parenchymal tissue volumes were estimated using a modified formula for body surface area, as follows: pulmonary blood volume = 1.947 X body weight X height parenchymal tissue volume = 5.8 X body weight
Total lung volume was calculated as the sum of the cardiac, diaphragmatic, pulmonary blood, and parenchymal tissue volumes subtracted from the TTCV, as follows:
total lung volume = TTCV — (cardiac volume + diaphragmatic volume + pulmonary blood volume + parenchymal tissue volume)
As standard practice, participants were asked to maximally inspire immediately prior to obtaining the radiograph, and all radiographs were taken at a distance of 72 inches to ensure consistent target/film distances. To account for radiograph beam divergence, a correction factor (0.729) was applied to the final volumetric calculations.
Figure 1. Representative digitized coordinate data plotted to demonstrate posteroanterior and lateral chest radiograph views with measurement sections as outlined in the “Materials and Methods” section.