Nedocromil sodium and diphenhydramine HCl ameliorate exercise‐induced arterial hypoxemia in highly trained athletes

INTRODUCTION: Exercise‐induced arterial hypoxemia (EIAH) has been observed in highly trained endurance athletes during near maximal exercise, which may be influenced by a histamine‐mediated inflammatory response at the pulmonary capillary‐alveolar membrane. In order to test this hypothesis, we examined whether the mast cell stabilizer nedocromil sodium (NS) and H(1)‐receptor antagonist diphenhydramine HCL (DH) would ameliorate EIAH and mitigate the drop in arterial oxyhemoglobin saturation (S(a)O(2)) during intensive exercise. METHODS: Seven highly trained male cross country runners (age, 21 ± 2 years; V̇O(2max), 74.7 ± 3.5 ml·kg(−1)·min(−1)) participated in the study. All subjects completed a maximal exercise treadmill test to exhaustion, followed by three 5‐min constant‐load exercise bouts at 70%, 80%, and 90% V̇O(2max). Prior to testing, subjects received either placebo (PL), NS, or DH. RESULTS: Compared to PL, there was a significant treatment effect on S(a)O(2) (p < 0.001) for both NS and DH during both constant‐load exercise and at V̇O(2max). Post hoc tests revealed S(a)O(2) values, compared to PL, were significantly higher at V̇O(2max) and during DH trials and higher with NS at constant‐load intensities except at 70% (p = 0.13). CONCLUSION: The findings provide further evidence that histamine contributes directly or indirectly to the development of EIAH during intense exercise in highly trained athletes.