NHLBI workshop summary. Biology of lung preservation for transplantation.

The types of animal models that are used for assessing lung preservation, and the types of interventions that are likely to prove of value, must be carefully selected. For example, the events of warm ischemia are not necessarily the same as those that occur during cold preservation. Warm ischemia has often been used as a means of accelerating the degree of ischemic injury, but the events may not be qualitatively the same. Nonetheless, the use of different types of lung injury models contributes to our overall understanding of mechanisms of lung injury associated with transplantation. Pathologic studies of lung injury ischemia and reperfusion may not prove helpful, as they may be nonspecific and insensitive. To compare results of different preservation methods, a standardized animal model would be most helpful if a universally accepted one could be identified. This would include standard measurements of lung function, standard techniques of transplantation, and follow-up studies of several days' duration after transplantation. Such a model could serve as the ultimate test of preservation methods following its development in a variety of the animal models. It must be emphasized that whereas animal models generally begin with a normal lung that is preserved, the clinical situation differs because the donor lungs may be far from normal at the outset due to the effects of brain death, hemodynamic instability, infection, trauma, and a host of other factors. Thus, the limits of safe preservation in a clinical situation may well be significantly less than the safe preservation time demonstrated in the laboratory.(ABSTRACT TRUNCATED AT 250 WORDS)     

Usefulness of noninvasive diagnostic tools for diagnosis of acute pulmonary embolism in patients with a normal chest radiograph

The value of bedside examination and noninvasive tests in the diagnosis of acute pulmonary embolism (PE) among patients with a normal chest radiograph was investigated. Normal chest radiographs were present in 20 of 260 patients (8%) with acute PE and in 113 of 642 (18%) with suspected acute PE, in whom the diagnosis was excluded. A partial pressure of oxygen in arterial blood less than or equal to 70 mm Hg in a dyspneic patient with a normal chest radiograph was more often seen among patients with PE (9 of 17, 53%) than among patients in whom PE was excluded (18 of 93, 19%; p less than 0.01). However, no combinations of blood gases, signs and symptoms were strictly diagnostic. High probability ventilation/perfusion scans among patients with a normal chest radiograph were indicative of PE in only 6 of 9 patients (67%). Among patients with low-probability ventilation/perfusion scans, 8 of 47 (17%) had PE. This study showed that the combination of dyspnea and hypoxia in a patient with a normal chest radiograph is a useful clue to the diagnosis of PE. Although intuition suggested that ventilation/perfusion scans would yield better results in patients with a normal chest radiograph, the ability to diagnose PE by ventilation/perfusion scans in this subset of patients was not enhanced, except by a reduction of the percentage of patients with intermediate probability scans.     

Protein composition of lung fluids in acute alloxan edema in dogs.

In 11 anesthetized dogs with acute alloxan-induced pulmonary edema, we measured the protein composition of 1-mul samples of plasma, free interstitial fluid, alveolar fluid, and airway fluid. We obtained plasma and airway fluid at regular intervals as edema developed. We sampled alveolar fluid by pleural micropuncture in the unfrozen, excised lung and free interstitial fluid from perivascular cuffs in the frozen, excised lung. The average (+/- 1 SD) total protein concentration of plasma was 4.9 +/- 0.6, airway fluid 4.4 +/- 0.7, free interstitial fluid 4.9 +/- 0.7, and alveolar fluid 5.2 +/- 0.8 g/100 ml. The average fractions of albumin were 0.42 +/- 0.05, 0.50 +/- 0.05, 0.49 +/- 0.06, and 0.49 +/- 0.07, respectively. By paired analysis, the protein concentration of interstitial fluid was not significantly different from alveolar fluid. The protein concentration of airway fluid was significantly less than that in interstitial and alveolar fluid. The albumin fraction of the three lung fluids was identical but significantly different from plasma. We conclude that in alloxan-induced pulmonary edema the lung fluids contain high concentrations of protein and the alveolar epithelial membrane becomes freely permeable to protein molecules.     

Complications and validity of pulmonary angiography in acute pulmonary embolism.

BACKGROUND. The Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) addressed the value of ventilation/perfusion scans in acute pulmonary embolism (PE). The present study evaluates the risks and diagnostic validity of pulmonary angiography in 1,111 patients who underwent angiography in PIOPED. METHODS AND RESULTS. Complications were death in five (0.5%), major nonfatal complications in nine (1%), and less significant or minor in 60 (5%). More fatal or major nonfatal complications occurred in patients from the medical intensive care unit than elsewhere: five of 122 (4%) versus nine of 989 (1%) (p less than 0.02). Pulmonary artery pressure, volume of contrast material, and presence of PE did not significantly affect the frequency of complications. Renal dysfunction, either major (requiring dialysis) or less severe, occurred in 13 of 1,111 (1%). Patients who developed renal dysfunction after angiography were older than those who did not have renal dysfunction: 74 +/- 13 years versus 57 +/- 17 years (p less than 0.001). Angiograms were nondiagnostic in 35 of 1,111 (3%), and studies were incomplete in 12 of 1,111 (1%), usually because of a complication. Surveillance after negative angiograms showed PE in four of 675 (0.6%). Angiograms, interpreted on the basis of consensus readings, resulted in an unchallenged diagnosis in 96%. CONCLUSIONS. The risks of pulmonary angiography were sufficiently low to justify it as a diagnostic tool in the appropriate clinical setting. Clinical judgment is probably the most important consideration in the assessment of risk.