title: Analysis of physiological variables during acute hypoxia and maximal stress test in adolescents clinically diagnosed with mild intermittent or mild persistent asthma.
abstract: OBJECTIVE
  To analyze adolescents clinically diagnosed with asthma, in terms of the physiological changes occurring during acute hypoxia and during a maximal stress test.
  
  
  METHODS
  This was a descriptive, cross-sectional study involving 48 adolescents (12-14 years of age) who were divided into three groups: mild intermittent asthma (MIA, n = 12); mild persistent asthma (MPA, n = 12); and control (n = 24). All subjects were induced to acute hypoxia and were submitted to maximal stress testing. Anthropometric data were collected, and functional variables were assessed before and after the maximal stress test. During acute hypoxia, the time to a decrease in SpO2 and the time to recovery of SpO2 (at rest) were determined.
  
  
  RESULTS
  No significant differences were found among the groups regarding the anthropometric variables or regarding the ventilatory variables during the stress test. Significant differences were found in oxygen half-saturation pressure of hemoglobin prior to the test and in PaO2 prior to the test between the MPA and control groups (p = 0.0279 and p = 0.0116, respectively), as was in the oxygen extraction tension prior to the test between the MIA and MPA groups (p = 0.0419). There were no significant differences in terms of the SpO2 times under any of the conditions studied. Oxygen consumption and respiratory efficiency were similar among the groups. The use of a bronchodilator provided no significant benefit during the hypoxia test. No correlations were found between the hypoxia test results and the physiological variables.
  
  
  CONCLUSIONS
  Our findings suggest that adolescents with mild persistent asthma have a greater capacity to adapt to hypoxia than do those with other types of asthma.
authors.affiliation: Laboratory of Exercise Physiology and Human Performance, Federal University of Santa Maria, Santa Maria, Brazil. w12martin@yahoo.com.ar
authors.forename: Martin
authors.initials: M
authors.lastname: Maldonado
authors.forename: Luiz Osório Cruz
authors.initials: LO
authors.lastname: Portela
mesh_terms: D000208:Acute Disease; D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D001249:Asthma / Q000145:classification / Q000503:physiopathology*; D002648:Child; D004812:Epidemiologic Methods; D005080:Exercise Test; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D005082:Physical Exertion / Q000502:physiology*