One male and eleven female subjects were examined in order to compare their ventilatory and heart rate responsiveness to hypoxia at rest and during moderate exercise (60 W) .
1) The slopes of the ventilatory response curve to hypoxia (AVE) were 306.5±229.5 and 1, 082.9±928.3l⋅min^-1⋅mmHg at rest and during exercise, respectively. Significant difference (p<0.05) between the two groups was found.
2) The slopes of the hypoxia-heart rate response curve (A_HR) were 704.9±477.3 and 1, 165.5±587.8 beats⋅min^-1⋅mmHg at rest and during exercise, respectively. The latter was significantly greater than the former (p<0.05) .
3) A significant relationship between AVE and AHR was observed (p<0.05) .
4) The relationship between ΔV_E50 and ΔHR₅₀, the increments of ventilation and heart rate from room-air to end-tidal Po₂ 50 mmHg, was also significant (p<0.01) .
These results indicate that hypoxic ventilatory and heart rate responsiveness during exercise is significantly greater than at rest, and point to the highly synergistic nature of the relationship between respiratory and cardiac regulations.

BACKGROUND: Leukotriene receptor antagonists have been used to prevent virus-induced asthma exacerbations in autumn. Its efficacy, however, might differ with age and sex. OBJECTIVE: This study aimed to investigate whether pranlukast added to usual asthma therapy in Japanese children during autumn, season associated with the peak of asthma, reduces asthma exacerbations. It was also evaluated the effect of age and sex on pranlukast's efficacy. METHODS: A total of 121 asthmatic children aged 1 to 14 years were randomly assigned to receive regular pranlukast or not according to sex, and were divided in 2 age groups, 1–5 years and 6–14 years. The primary outcome was total asthma score calculated during 8 weeks by using a sticker calendar related to the days in which a child experienced a worsening of asthma symptoms. This open study lasted 60 days from September 15 to November 14, 2007. RESULTS: Significant differences in pranlukast efficacy were observed between sex and age groups. Boys aged 1 to 5 years had the lower total asthma score at 8 weeks (p = 0.002), and experienced fewer cold episodes (p = 0.007). There were no significant differences between pranlukast and control group in total asthma score at 8 weeks (p = 0.35), and in the days in which a child experienced a worsening of asthma symptoms (p = 0.67). CONCLUSION: There was a substantial benefit of adding pranlukast to usual therapy in asthmatic children, especially in boys aged 1 to 5 years, during autumn season.
Asian Continental Ancestry Group ; Asthma ; Child ; Child, Preschool ; Humans ; Leukotriene Antagonists ; Seasons