Pulmonary edema and the development of exercise-induced hypoxemia in highly trained endurance athletes
Creators: name: Turner, Simon Patrick Duignan
Publisher: name: University of British Columbia
Year: 2008

description: Twelve healthy male endurance trained athletes (mean age=24.8 ± 3.3 yrs, ht.=181.4 ± 4.8 cm., wt.=75.3 ± 6.7 kg., V02max=67.9 ± 5.6 ml/kg/min) served as subjects in an experiment to examine the effects of changing plasma volume on the relationship between pulmonary diffusion capacity (DLCO) and arterial blood oxygen saturation (%Sa02) following intense exercise. Subjects were divided into two groups based on the minimum %Sa02 recorded (HP47201A ear oximeter) during a V02max test; Non-desaturaters (ND=4) %SaO2&gt;91.0 and Desaturaters (D=8) %SaO2&lt;91.0. Each subject performed two, 5 minute bouts of exercise on separate days (Mijnhardt electrically-braked cycle ergometer) at a floating workload (mean=370 ± 30 W) assigned to maintain a V 0 2 equal to 90% of the subjects previously determined VC^max. The two trials (PLACEBO and LASIX) were assigned in random, double blind manner. In each of the trials the percent change in plasma volume (%dPV) was measured using hematocrit and hemoglobin values from 3cc blood samples taken immediately prior to each DLCO test. The DLCO (single-breath carbon monoxide method) was measured at three points during each trial; immediately prior to ingestion of the capsule, three hours later (one half hour prior to exercise) and one hour after completion of the exercise bout. The %Sa02 was monitored throughout the exercise period. In the PLACEBO trial both groups showed no significant changes in either %dPV or bodyweight. There was also no significant change in Pre-Pill to Pre-Exercise DLCO but a significant decrease (p&lt;.05) in DLCO after exercise did occur for both groups. The ND had a decrease of 7.34% (41.75 + 5.43 to 38.69 + 4.87) while the D had a 6.49% decrease in DLCO (40.13 ± 5.36 to 37.52 + 4.29). There was no significant difference in the degree or pattern of change in DLCO following an exercise bout of this nature. The %SaC&gt;2 showed a significant 6.54% decrease during intense exercise (p&lt;.001 ). The ND had a 4.67% decrease in %Sa02 (97.9 ± 0.24 to 93.3 ± 1.26) while the D had a significantly greater decrease of 7.47% (97.5 + 0.91 to 90.2 + 1.01 ) (p&lt;.05). In the LASIX trial (40 mg furosemide) there was a significant 6.26% decrease in %dPV (p&lt;.001) and a 1.7 ± 0.44 kg (p&lt;.05) in bodyweight with no differences between ND and D. There was an overall significant decrease in DLCO values for D of 10.87% (40.84 + 4.27 to 36.40 ± 4.82, p&lt;.001) and 8.04% for the ND (40.16 ± 2.52 to 36.93 ± 3.74, p&lt;.01). Both the ND and D experienced significant and similar Pre-Pill to Pre-Exercise decreases in DLCO (ND=6.27%; D=4.67%, p&lt;.01). The Pre-Exercise to Post-Exercise decrease in DLCO was significant for D (6.43%, p&lt;.01) but not for ND (1.88%). During 5 minutes of intense cycling after ingestion of LASIX the D experienced a significant 7.76% decrease in %Sa02 (96.9 + 0.85 to 89.4 ±1.19, p&lt;.001) but the 3.03% change in %Sa02 for the ND was not significant. The correlations between percent decrease in %Sa02 and percent decrease in DLCO for ND and D in both trials were non-significant. As well, there was no significant difference between the magnitude of decrease in DLCO in the PLACEBO or LASIX conditions for both groups. Intense exercise results in a decrease in Post-Exercise DLCO which may indicate the formation of subclinical pulmonary edema. The reduction in plasma volume of the magnitude observed in this study after ingestion of 40mg of LASIX did not attenuate the significant decrease in Post-Exercise DLCO or the decrease in %Sa02 experienced by the D during intense exercise. Based on the comparison of values of %Sa02 and DLCO in both ND and D, it appears that the contribution of the changes in DLCO to the drop in %Sa02 during exercise is low.