title: Acute effects of smoking on autonomic modulation: analysis by Poincaré plot.
abstract: BACKGROUND
  Smoking affects the autonomic function.
  
  
  OBJECTIVE
  To investigate the acute effects of smoking on the autonomic modulation and the post-smoking recovery of the heart rate variability (HRV) index through Poincaré plot and linear indices.
  
  
  METHODS
  A total of 25 young smokers underwent beat-to-beat analysis of heart rate in the sitting position after 8 hours of tobacco abstinence, for 30 minutes at rest, 20 minutes while smoking and 30 minutes after smoking. The analysis of variance for repeated measures, followed by Tukey's test or Friedman's test followed by Dunn's test, were applied depending on the normality of data, with p < 0.05.
  
  
  RESULTS
  While smoking, there was a decrease in the indices: SD1 (23.4 ± 9.2 vs 13.8 ± 4.8), SD1/SD2 ratio (0.31 ± 0.08 vs 0.2 ± 0.04), RMSSD (32,7 ± 13 vs 19.1 ± 6.8), SDNN (47.6 ± 14.8 vs 35.5 ± 8.4), HFnu (32,5 ± 11.6 vs 19 ± 8.1) and the RR interval (816.8 ± 89 vs 696.5 ± 76.3) in relation to the rest period, whereas increases in the LFnu index (67.5 ± 11.6 vs 81 ± 8.1) and the LF/HF ratio (2.6 ± 1.7 vs 5.4 ± 3.1) were observed. The visual analysis of the plot showed a lower dispersion of RR intervals while smoking. Except for the SD1/SD2 ratio, the other indices presented recovery of values 30 minutes after smoking.
  
  
  CONCLUSIONS
  Smoking resulted in acute modifications of the autonomic control, characterized by sympathetic activation and vagal withdrawal, presenting recovery 30 minutes after smoking.
authors.affiliation: Faculdade de Ciências e Tecnologia, UNESP, Presidente Prudente, São Paulo-SP, Brazil.
authors.forename: Beatriz Martins
authors.initials: BM
authors.lastname: Manzano
authors.forename: Luiz Carlos Marques
authors.initials: LC
authors.lastname: Vanderlei
authors.forename: Ercy Mara
authors.initials: EM
authors.lastname: Ramos
authors.forename: Dionei
authors.initials: D
authors.lastname: Ramos
mesh_terms: D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult