Alterations of diaphragm and rib cage morphometry in severe COPD patients by CT analysis

Although it is known that in patients with COPD acute hyperinflation determines shortening of the inspiratory muscles, its effects on both diaphragm and rib cage morphology are still to be investigated. In this preliminary study the relationships between hyperinflation, emphysema, diaphragm and rib cage geometry were studied in 5 severe COPD patients and 5 healthy subjects. An automatic software was developed to obtain the 3-D reconstruction of diaphragm and rib cage from CT scans taken at total lung capacity (TLC) and residual volume (RV). Dome surface area (Ado), radius of curvature, length (Ld) and position (referred to xiphoid level) of the diaphragm and antero-posterior (A-P) and transverse (T) diameters of rib cage were calculated at both volumes. Ado and Ld were similar in COPD and controls when compared at similar absolute lung volumes. Radius of curvature was significantly higher in COPD than in controls only at TLC. In COPD, the range of diaphragm position was invariantly below the xiphoid level, while in controls the top of diaphragm dome was always above it. Rib cage diameters were not different at TLC. A-P diameter was greater in COPD than in controls at RV, while T diameters were similar. In conclusion, in severe COPD diaphragm and rib cage geometry is altered at RV. The lower position of diaphragm is associated to smaller A-P but not transversal rib cage diameters, such that rib cage adopts a more circular shape.

Effect of lung resection on pleuro-pulmonary mechanics and fluid balance

The aim of the study was to determine in human patients the effect of lung resection on lung compliance and on pleuro-pulmonary fluid balance. Pre and post-operative values of compliance were measured in anesthetized patients undergoing resection for lung cancer (N=11) through double-lumen bronchial intubation. Lung compliance was measured for 10-12 cm H2O increase in alveolar pressure from 5 cm H2O PEEP in control and repeated after resection. No air leak was assessed and pleural fluid was collected during hospital stay. A significant negative correlation (r(2)=0.68) was found between compliance at 10 min and resected mass. Based on the pre-operative estimated lung weight, the decrease in compliance following lung resection exceeded by 10-15% that expected from resected mass. Significant negative relationships were found by relating pleural fluid drainage flow to the remaining lung mass and to post-operative lung compliance. Following lung re-expansion, data suggest a causative relationship between the decrease in compliance and the perturbation in pleuro-pulmonary fluid balance.

Registration of lung CT images acquired in different respiratory ranges with 4DCT and HRCT

Pulmonary image registration is challenging because of the unique structure of the lung, its high deformability and its non-uniform intensity change with breathing. In the present work we propose a new method for pulmonary image registration, based on the reconstruction and the combination of the main pulmonary structures to modify parenchyma intensity prior to the application of the registration algorithm. The algorithm has been applied to both four dimensional CT and multi-volume high resolution CT demonstrating an increased accuracy of the results with the application of the pulmonary structure enhancement, evaluated both on landmarks distance in 4DCT and structures' surface distance in HRCT.

Non-invasive three-dimensional imaging of human diaphragm in-vivo

Three-dimensional reconstruction of human diaphragm provide useful information on the functional anatomy of the respiratory system by the analysis of its geometry. The aim of the current work is the development of a new method for the 3D analysis of diaphragm geometry by the combination of free-hand Ultrasound (US) scans with an optoelectronic system of movement analysis for the tracking of the probe. 6 healthy subjects (age=24+/-2), have been measured with a free-hand US scanning of the abdomen in supine (SP) and seated position (ST), during breath-holding at Functional Residual Capacity (FRC) and Total Lung Capacity (TLC). For one of them, measurements have been repeated in supine position in an MR scan for the validation of the method. Posture has different implications on diaphragm geometry depending on the respiratory volume. At FRC the ray of curvature (rho) in ST is 101.1+/-43.1 mm higher than in SP (p=0.006), while at TLC, posture influences the position of the diaphragm with a caudo-cranial displacement from SP to ST of 23.4+/-16.7mm (p=0.019). Diaphragm geometry at different lung volumes is influenced by the posture. In SP, rho increases of 105.9+/-48.3 mm (p=0.008) and there is a cranio-caudal displacement (Deltay) of 47.54+/-15 mm (p=0.002) shifting from FRC to TLC. In ST, Deltay=31.1+/-13.5 mm (p=0.006) while rho increases not significantly. Percentage errors between MR and US 3D reconstructions are 2.1% and 10.46% for Deltay and TLC/FRC rho ratio, respectively. US 3D reconstruction is a reliable method for the assessment of diaphragm functional anatomy. Posture directly influence diaphragm geometry and hence respiratory mechanics.