J. R. Rodarte

Effect of resection of the sternum and manubrium in conjunction with muscle transposition on pulmonary function

We recorded the changes in pulmonary function that occurred after removal of the sternum and manubrium and repair by pectoralis major muscle transposition in six patients. Of these patients, three had osteomyelitis of the manubrium and sternum, two had osteosarcoma of the sternum, and one had osteomyelitis and radionecrosis of the manubrium and sternum. Body plethysmography and the rebreathing, hypercapnic ventilatory response test with inductive plethysmographic recordings of chest-wall motion were performed preoperatively and postoperatively. Preoperatively, four of the six patients had evidence of mild to moderate chest-wall restriction. Pulmonary function was normal in the other two patients. Postoperatively, total lung capacity was unchanged but the vital capacity decreased 11.5% in the overall group. Static compliance, retractive force, and the steady-state diffusing capacity for carbon monoxide decreased modestly but significantly postoperatively. The expiratory flow rates and maximal voluntary ventilation remained unchanged. Preoperatively, the slope of the hypercapnic ventilatory response was less than that predicted. Postoperatively, the slope did not change. In three patients, however, increased dependence on the abdomen for breathing suggested a dynamic restriction of rib-cage motion. On the basis of our findings, we conclude that surgical removal of the sternum and manubrium in conjunction with muscle flap repair is a well-tolerated procedure. Any postoperative changes in pulmonary function are minor.

Effect of acute exposure to CO2 on lung mechanics in normal man

Abstract The effect of CO 2 on lung mechanics was examined in 10 healthy men at rest. Measurements were begun after each breathed an inspired concentration of 6 % CO 2 in air for 5 min. Lung volumes, expiratory flow-volume curves, static pressure-volume curves of the lung, and pulmonary conductance were measured. CO 2 breathing produced a small but statistically significant increase in total lung capacity. Pulmonary conductance measured by a flow-interruption technique increased markedly in one subject but decreased in all others. The decrease in conductance was not prevented by treatment with a bronchodilator and was considered the result of an increase in laryngeal resistance. There was no consistent effect of CO 2 breathing on any other parameter.

Lung Volumes and Closing Capacity with Continuous Positive Airway Pressure

Total lung capacity, vital capacity, residual volume, and functional residual capacity were determined by body plethysmography and the single-breath oxygen (SBO2) test was performed at 0, 5, and 11 cm H2O continuous positive airway pressure in healthy, awake, seated, spontaneously breathing subjects. Mean values for the absolute lung volume at which phase IV of the SBO2 test begins (closing capacity) did not change significantly with continuous positive airway pressure at 5 or 11 cm H2O. Mean total lung capacity, functional residual capacity, and residual volume increased significantly, and the mean closing volume, the lung volume above residual volume at which phase IV begins, decreased significantly with II cm H2O continuous positive airway pressure; differences at 5 cm H2O were not significant. The slope of the alveolar nitrogen plateau (phase III) obtained during the SBO2 test did not change with continuous positive airway pressure.

The mechanisms that limit expiratory flow.

Recent progress in modeling expiratory flow is reviewed. Two idealized flow limitating mechanisms are described: flow limitation at wave speed and viscous flow limitation. In the lung, both convection acceleration and viscous dissipation contribute to the pressure distribution that determines airways compression, but the first dominates at high and mid lung volumes and the second dominates at low lung volumes. A computer model describes the combined effects. This quantitative modeling is consistent with long-standing qualitative concepts of flow limitation and provides a basis for future work on modeling expiratory flow limitation in abnormal lungs.

Finite-element analysis of the strain variations in excised lobe of canine lung.

Abstract The excised right lower lobe of a 10-kg dogs lung was manually inflated to the total capacity and then deflated in a step-wise manner to record the three-dimensional displacements of small metallic markers, which were affixed to the pleural surface, by employing a computer-based biplane roentgen-videographic technique. The temporal and spatial changes of the strains in the lobe during deflation were determined by partitioning of the lobe into a finite number of tetrahedral regions. By taking the implanted markers as the vertices of the tetrahedrons and utilizing their changes in spatial coordinates, finite-element calculations of the strain variations in the lobe were performed. Sample results of strains are presented. It shows that except in the vicinity of one of the implanted markers, the normal strains are generally higher than the shearing strains in the deflating excised lobe.

Acute and Long-Term Effects of Fluosol-DA 20% on Respiratory System Mechanics and Diffusion Capacity in Dogs

We evaluated the acute and cumulative effects of Fluosol-DA 20% (Fluosol, Alpha Therapeutics, Los Angeles) on respiratory system mechanics and the diffusing capacity for carbon monoxide (DLCO) in six dogs. A total dose of 45 to 75 mL/kg was administered during a period of eight to 12 days. After a loading dose of 15 mL/kg was a dose of 10 mL/kg was administered intravenously on alternate study days in four dogs and on successive days in two dogs. There were no significant differences between the initial and final study day in total lung capacity (TLC), residual volume (RV), static lung compliance (CSTAT), dynamic lung compliance (CDYN), the retractive force at 50% at TLC (P50 TLC), and the diffusion capacity for carbon monoxide (CLCO). Although there was a small increase in the total pulmonary resistance (RTP, 0.8 to 1.8 cm H2O/L/s; P < .05), its absolute value remained in the normal range. In contrast to the lack of chronic dose-dependent and time-dependent changes in lung mechanics and DLCO, there was a transient decrease in CDYN, from 0.066 to 0.047 L/cm H2O, and an increase in RTP, from 1.44 to 4.83 cm H2O/L/s (P < .001), immediately following the infusion of Fluosol. We conclude that an increase in pulmonary resistance to airflow is part of the idiosyncratic acute reaction after the administration of Fluosol, while the repeated administration of Fluosol has little effect on pulmonary gas transfer assessed by CLCO and respiratory system mechanics.

Analysis of parenchymal deformation in excised canine lung lobes using rotationally-corrected strains

Abstract The pure deformation component of a general non-homogenous transformation of coordinates is used to obtain strains which are referenced to a local orthogonal coordinate system. The global orientation of the local coordinate system varies from point to point in a continuum, depending on the local rotation. By considering only pure strain, a much improved description of the deformation field in a highly deformable material such as lung parenchyma is obtained, compared to that calculated using classical elasticity strain components. This technique in part justifies the use of linear analyses to describe lung deformations, despite the presence of large strains.