Bernard E. Pennock

The Diffusing Capacity as a Predictor of Arterial Oxygen Desaturation during Exercise in Patients with Chronic Obstructive Pulmonary Disease

We evaluated 48 patients with chronic obstructive pulmonary disease by means of pulmonary-function and exercise testing to determine whether any tests of pulmonary function could predict the development of arterial desaturation during exercise. We found that only two indexes--diffusing capacity and forced expiratory volume in one second (FEV1)--were predictive of desaturation. The diffusing capacity was more specific and sensitive than FEV1. A diffusing capacity above 55 per cent of predicted was 100 per cent specific in excluding desaturation, as compared with an 82 per cent specificity for an FEV1 above 55 per cent of predicted. With this cutoff point, the sensitivity of the diffusing capacity was 68 per cent, as compared with 46 per cent for the FEV1. Both the frequency and the magnitude of arterial desaturation increased substantially when the diffusing capacity was below 55 per cent of predicted. Testing the diffusing capacity should be useful in identifying which patients with chronic obstructive lung disease are likely to become desaturated during exercise and may therefore benefit from oxygen therapy.

Composition and characterization of the lipids of garfish (Lepisosteus osseus) olfactory nerve, a tissue rich in axonal membrane

The garfish olfactory and trigeminal nerves were studied for their lipid composition. Cholesterol was the only neutral lipid found in both nerves. The phospholipids constituted about 73, and 64%, respectively, of the olfactory and trigeminal nerve total lipids. Cerebrosides and sulfatide were found only in the myelinated trigeminal nerve. An unidentified glycolipid was found in the olfactory nerve lipid extract. The phospholipid fraction in both nerves was composed mainly of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and sphingomyelin. Minor components were phosphatidylinositol, phosphatidic acid and diphosphatidylglycerol. As compared with the phospholipid composition of the myelinated trigeminal nerve, the olfactory nerve had less phosphatidylethanolamine and more phosphatidylcholine and phosphatidylinositol. The phosphatidylethanolamine fraction was rich in plasmalogen but only small amounts of plasmalogen were found in phosphatidylcholine and phosphatidylserine. Substantial amounts of alkyl glyceryl ether types were found in both phosphatidylethanolamine and phosphatidylcholine. A distinctive characteristic of the lipids of the olfactory nerve was the presence of large proportions of long chain, highly unsaturated fatty acids. These fatty acids, namely C20:4 and C22:6, were preferentially located in phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol.

Local lung ventilation in critically ill patients using nonradioactive xenon-enhanced transmission computed tomography

Nonradioactive xenon is sufficiently radiodense to increase the density of gas-containing lung as seen in a computed tomography (CT) scan. Subtraction of a baseline CT scan from the xenon-enhanced CT scan can accentuate gas space differences by subtracting fixed tissue densities. The baseline scan and the scan obtained during wash-in of xenon (before equilibration) allow circulation of local ventilation. The xenon CT scan, thus, provides more precise information about distribution of ventilation than planar radiogas techniques. The technical aspects of application to a critically ill patient and the mathematical basis of the technique are presented.

Descriptive ventilatory mechanics from noninvasive analog display of ribcage and abdominal flow

A rapidly responding analog display of ventilatory flow at the mouth, ribcage and abdomen allows interpretation of the relative activity of the diaphragm, accessory inspiratory muscles and abdominal expiratory muscles. These relative movements are exaggerated by having volunteers perform the ventilatory maneuvers of sniff, rapid exhalation and cough. Activity and regional lung flow can change in time periods in the tens of milliseconds. These rapid (within an inspiratory or expiratory time) relational changes in respiratory muscle activity and regional lung flow have not previously been demonstrated with a simple noninvasive measurement.