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9.L6 Nitric oxide levels in exercise
The effects of exercise on levels of exhaled NO in healthy, athletic adults, and those with
respiratory and/or cardiac disease has been investigated, with a few studies also done in
children. In healthy adults, the measurement of exhaled NO with exercise (treadmill or
bicycle) showed a decrease when measuring the absolute levels in single breaths, but there
was a two to three fold increase in NO output taking into account the increased ventilatory
minute volume @ersson, Wiklund et al. 1993; Iwamoto, Pendergast et al. 1994; Trolin, Anden
et al. 1994; Phillips, Giraud et al. 1996; Yasuda, Itoh et al. L997). The increased output more
closely related to increased ventilation than increased blood flow @hillips, Giraud et al. 1996)
and significantly correlated with CO2 production (Iwamoto, Pendergast et al. 1994). Two
studies assessed the contribution from nasal or oral exhalations showing that most of the NO
coming from the lower airways (Lundberg, Rinder et al. 1997; Yasuda, Itoh et al. 1997) and
from the airway rather than alveolar compartment @ersson, Wiklund et al. 1993). The nasal
cavity NO reduced by 47Vo after one minute and 76Vo after five minutes of exercise
(Lundberg, Rinder et al. 1997).
There have been many studies done in elite athletes. When compared to those with lower
levels of fitness, the athletes had a significantly more linear increase in NO output (Maroun,
Mehta et al. 1995; Chirpaz-Oddou, Favre-Juvin et al. L997; Sheel, Edwards et al. 2000;
Verges, Flore et al. 2005). This output correlated well with oxygen consumption, COz
production, minute ventilation and heart rate (Chirpaz-Oddou, Favre-Juvin et al. 1997).In one
study, athletes that developed exercise induced hypoxemia had lower levels of NO compared
to those who did not seen (Kippelen, Caillaud et al. 2N2), but this was not confirmed in
another (Sheel, Edwards et al. 2000). Exercise in cold challenge conditions resulted in lower
levels of exhaled NO output being achieved and a slower time to recovery with lower FEVr
(Therminarias, Flore et al. 1998; Pendergast, Krasney et al. 1999). These results suggested
that physical conditioning increases expiratory NO output during exercise and this may be due
to an increased vascular and/or epithelial production of NO. The enhanced vascular NO
production may be the result of increased share stress or of an up regulation of the endothelial
NOS gene expression (Maroun, Mehta et al. 1995).
Can NO predict development of exercise induced bronchospasm? Higher baseline levels were
significantly associated with bronchoconstriction and histamine responsiveness in atopic
rather than non-atopic steroid naive healthy conscripts (Rouhos, Ekroos et al. 2005). In 50
consecutive subjects, a ROC curve yielded a value of 0.636 when comparing those who did
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