Left atrial enlargement and reduced physical function during aging.

Diastolic dysfunction, often seen with increasing age, is associated with reduced exercise capacity and increased mortality. Mortality rates in older individuals are linked to the development of disability, which may be preceded by functional limitations. The goal of this study was to identify which echocardiographic measures of diastolic function correlate with physical function in older subjects. A total of 36 men and women from the Louisiana Healthy Aging Study, age 62-101 yr, received a complete echocardiographic exam and performed the 10-item continuous-scale physical-functional performance test (CS-PFP-10). After adjustment for age and gender, left atrial volume index (ρ = -0.59; p = .0005) correlated with the total CS-PFP-10 score. Increased left atrial volume index may be a marker of impaired performance of activities of daily living in older individuals.

Low positive end-expiratory pressure does not exacerbate nebulized-acid lung injury in dogs.

It is not clear if low end-expiratory pressures contribute to ventilator-induced lung injury in large animals. We sought to determine whether ventilation with a low level of positive end-expiratory pressure (PEEP) worsens preexisting permeability lung injury in dogs. Lung injury was initiated in 20 mongrel dogs by ventilating with nebulized 3N hydrochloric acid until a lower inflection point (LIP) appeared on the respiratory system pressure-volume loop. One group of 10 dogs was then ventilated for 4 hours with PEEP set below the LIP (low PEEP), whereas the remaining group of dogs was ventilated for the same time period with similar tidal volumes but with PEEP set above the LIP (high PEEP). We found histologic evidence of reduced alveolar volumes in the low-PEEP animals. However, there were no differences in neutrophil infiltration, lung lobe weights, pulmonary capillary hemorrhage or congestion, or arterial endothelin-1 concentration between the 2 protocol groups. In conclusion, we were unable to demonstrate that ventilation with PEEP set below the LIP exacerbates hydrochloric acid-induced lung injury in dogs.

Estimation of pulmonary artery occlusion pressure by an artificial neural network.

OBJECTIVE: We hypothesized that an artificial neural network, interconnected computer elements capable of adaptation and learning, could accurately estimate pulmonary artery occlusion pressure from the pulsatile pulmonary artery waveform. SETTING: University medical center. SUBJECTS: Nineteen closed-chest dogs. INTERVENTIONS: Pulmonary artery waveforms were digitally sampled before conventional measurements of pulmonary artery occlusion pressure under control conditions, during infusions of serotonin or histamine, or during volume loading. Individual beats were parsed or separated out. Pulmonary artery pressure, its first time derivative, and the beat duration were used as neural inputs. The neural network was trained by using 80% of all samples and tested on the remaining 20%. For comparison, the regression between pulmonary artery diastolic pressure and pulmonary artery occlusion pressure was developed and tested using the same data sets. As a final test of generalizability, the neural network was trained on data obtained from 18 dogs and tested on data from the remaining dog in a round-robin fashion. MEASUREMENTS AND MAIN RESULTS: The correlation coefficient between the pulmonary artery diastolic pressure estimate of pulmonary artery occlusion pressure and measured pulmonary artery occlusion pressure was.75, whereas that for the neural network estimate of pulmonary artery occlusion pressure was.97 (p <.01 for difference between pulmonary artery diastolic pressure and pulmonary artery occlusion pressure estimates). The pulmonary artery diastolic pressure estimate of pulmonary artery occlusion pressure showed a bias of 0.097 mm Hg (limits of agreement -7.57 to 7.767 mm Hg), whereas the neural network estimate of pulmonary artery occlusion pressure showed a bias of -0.002 mm Hg (-2.592 to 2.588 mm Hg). There was no significant change in the bias of the neural network estimate over the range of values tested. In contrast, the bias for the pulmonary artery diastolic pressure estimate significantly increased with the increasing magnitude of the pulmonary artery occlusion pressure. During round-robin testing, the neural network estimate of pulmonary artery occlusion pressure showed suboptimal performance (correlation coefficient between estimated and measured pulmonary artery occlusion pressure.59). CONCLUSIONS: A neural network can accurately estimate pulmonary artery occlusion pressure over a wide range of pulmonary artery occlusion pressure under conditions that alter pulmonary hemodynamics. We speculate that artificial neural networks could provide accurate, real-time estimates of pulmonary artery occlusion pressure in critically ill patients.

Pulmonary capillary pressure during acute lung injury in dogs.

OBJECTIVES: To measure pulmonary capillary pressure and pulmonary artery occlusion pressures both during control conditions and during acute lung injury and to evaluate the effects of inotropic therapy and volume loading on these measurements after lung injury. DESIGN: Prospective, randomized, controlled laboratory trial. SETTING: University research laboratory. SUBJECTS: Eighteen heartworm-free mongrel dogs. INTERVENTIONS: Dogs were anesthetized (sodium pentobarbital, 30 mg/kg intravenously), intubated, and mechanically ventilated. A femoral artery and vein and the right external jugular vein were cannulated. After a median sternotomy, two pulmonary artery catheters were inserted via the jugular vein into the left and right lower lobar pulmonary arteries. Oleic acid (0.03 mL/kg) was administered to all dogs via the left pulmonary artery catheter, whereas the right lower lobe served as control. A baseline group of dogs received no further interventions, whereas two additional groups were given dobutamine (30-60 microg x kg(-1) x min(-1)intravenously) or saline boluses (1-2 L) before measurements were obtained after oleic acid lung injury. MEASUREMENTS AND MAIN RESULTS: Capillary pressure was estimated in both lower lung lobes by using the pulmonary artery occlusion method. Pulmonary capillary and pulmonary artery occlusion pressures were measured before and 2 hrs after oleic acid administration. Left lower lobar capillary pressure increased in all three groups, as did the difference between capillary pressure and pulmonary artery occlusion pressure. Capillary pressure in the control right lower lobe increased significantly only in the saline-loaded dogs, whereas the difference between the right-sided capillary and occlusion pressures increased only in the dogs given dobutamine. CONCLUSIONS: Oleic acid lung injury increases pulmonary capillary pressure independent of pulmonary artery occlusion pressure. The gradient between the two pressures was not significantly affected by volume loading or dobutamine infusion.