THE PRESSURE-VOLUME RELATIONSHIP OF THE NORMAL PULMONARY CAPILLARY BED

Pulmonary hemorrhage resulting from bungee jumping

Pulmonary hemorrhage is a relatively common complication of blunt chest trauma. Occasionally, it may result from pulmonary barotrauma after scuba diving or from sports activities not associated with barotrauma such as long breath-hold diving. We report a case of symmetric diffuse upper lobe hemorrhage resulting from a bungee jump in a previously healthy man. Bungee jumping is an increasingly popular sport with relatively few reported injuries. To our knowledge pulmonary hemorrhage in this setting has not yet been described.

Single-breath carbon monoxide diffusing capacity

Measurement of DL(CO) remains a clinically useful way to assess transfer of gases across the lung. It is important, however, to be vigilant in controlling the sources of variation and to be aware of those that remain when interpreting the measured values.

Pulmonary diffusing capacity and pulmonary capillary blood volume during parabolic flights

Data from the Spacelab Life Sciences-1 (SLS-1) mission have shown sustained but moderate increase in pulmonary diffusing capacity (DL). Because of the occupational constraints of the mission, data were only obtained after 24 h of exposure to microgravity. Parabolic flights are often used to study some effects of microgravity, and we measured changes in DL occurring at the very onset of weightlessness. Measurements of DL, membrane diffusing capacity, and pulmonary capillary blood volume were made in 10 male subjects during the 20-s 0-G phases of parabolic flights performed by the "zero-G" Caravelle aircraft. Using the standardized single-breath technique, we measured DL for CO and nitric oxide simultaneously. We found significant increases in DL for CO (62%), in membrane diffusing capacity for CO (47%), in DL for nitric oxide (47%), and in pulmonary capillary blood volume (71%). We conclude that major changes in the alveolar membrane gas transfers and in the pulmonary capillary bed occur at the very onset of microgravity. Because these changes are much greater than those reported during sustained microgravity, the effects of rapid transition from hypergravity to microgravity during parabolic flights remain questionable.

Effect of high negative inspiratory pressure on single breath CO diffusing capacity

We measured the single breath diffusing capacity for carbon monoxide (DLcoSB) using a three-equation method to describe CO uptake in 10 normal seated subjects who either voluntarily inhaled slowly (0.5 L/sec) to total lung capacity (TLC), or inhaled slowly to TLC with maximal effort through a high inspiratory resistance which created high negative inspiratory pressure. Subjects then immediately exhaled slowly at a voluntarily controlled exhaled flow. Single breath maneuvers were performed in duplicate both with and without high negative inspiratory pressure while subjects were seated upright at rest and during steady-state bicycle exercise. We found that high negative inspiratory pressure increased DLcoSB by 10.5 +/- 4.9% (mean +/- 1 SD) at rest (P less than 0.001). In 7 subjects low level exercise alone increased DLcoSB by a similar amount (12.1 +/- 7.3%; P = 0.005). In six of the subjects there was a significant correlation between the increase in DLcoSB during high negative inspiratory pressure at rest and the increase in DLcoSB during steady-state exercise (r = 0.89; P less than 0.01). During steady-state exercise, high negative inspiratory pressure further increased DLcoSB 6.4 +/- 6.3% compared to exercise alone (P = 0.05). We conclude that the increase in DLcoSB with high negative inspiratory pressure at rest is a simple reproducible method of assessing recruitment of the pulmonary capillary bed in man.

Noninvasive measurement of pulmonary transvascular protein flux in normal man

Onset of lung edema is usually associated with increase in the pulmonary transvascular flux of water and proteins. Clinical measurement of these parameters may aid in early diagnosis of pulmonary edema, and allow differentiation between "cardiogenic" and "noncardiogenic" types base on the magnitude of the detected changes. We have previously described a noninvasive method for estimating transvascular protein flux in lung (Gorin, A. B., W. J. Weidner, R. H. Demling, and N. C. Staub, 1978. Noninvasive measurement of pulmonary transvascular protein flux in sheep. J. Appl. Physiol. 45: 225-233). Using this method we measured the net transvascular flux of [113mIn]transferrin (mol wt, 76,000 in lungs of nine normal human volunteers. Plasma clearance of [113In]transferrin occurred with a T1/2 = 7.0 +/- 2.6 h (mean +/- SD). The pulmonary transvascular flux coefficient, alpha, was 2.9 +/- 1.4 X 10(-3) ml/s (mean +/- SD) in man, slightly greater than that previously measured in sheep (2.7 +/- 0.7 X 10(-3) ml/s; mean +/- SD). The pulmonary transcapillary escape rate is twofold greater than the transcapillary escape rate for the vascular bed as a whole, indicating a greater "porosity" of exchanging vessels in the lung than exists for the "average" microvessel in the body. Time taken to reach half-equilibrium concentration of tracer protein in the lung interstitium was quite short, 52 +/- 13 min (mean +/- SD). We have shown that measurement of pulmonary transvascular protein flux in man is practical. The coefficient of variation of measurements of alpha (between subjects) was 0.48, and of measurements of pulmonary transcapillary escape rates was 0.39. In animals, endothelial injury commonly results in a two- to threefold increase in transvascular protein flux. Thus, external radioflux detection should be a suitable means of quantitating lung vascular injury in human disease states.

The effects of acute ethanol ingestion on pulmonary diffusing capacity

Single breath diffusing capacities for carbon monoxide (DLco) were measured in 12 normal supine subjects before and after ingestion of 15 to 30 ml of 95 percent ethanol (ETOH) to determine if alcohol could acutely change the DLco. Both DLco and specific DLco (DLco/alveolar volume) were significantly decreased 90 minutes after the ingestion of alcohol. This change may be due to a direct effect of alcohol on the alveolar capillary interface by possibly interfering with a carbon monoxide carrier molecule. Another plausible explanation for the reduced diffusing capacity after ingestion of alcohol may be redistribution of blood from the lung to the periphery secondary to the hemodynamic effects of alcohol.