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  • Poster presentation
  • Open Access

Bi-level positive airway pressure produces an increase of sympathetic response in healthy young men

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Critical Care200711 (Suppl 3) :P72

  • Published:


  • Heart Rate
  • Frequency Domain
  • Heart Rate Variability
  • Activity Reduction
  • Spontaneous Breathing


To evaluate healthy young men's heart rate variability with and without noninvasive positive pressure ventilation (NPPV).


Eleven healthy men (22 ± 2.2 years) were evaluated. The heart rate and R-R intervals (R-Ri) were recorded in a sitting position during spontaneous breathing and NPPV application (600 min each). The NPPV was delivered using a bi-level positive airway pressure (BiPAP) applied via a nasal mask with inspiratory and expiratory levels of 20 and 13 cmH2O, respectively. The heart rate and its variability were analyzed in the time domain by the RMSSD (root mean square of the squares of the differences between successive R-Ri) and SDNN (standard deviation of all R-Ri) indexes of R-Ri (ms); and in the frequency domain by the low-frequency (LF) and high-frequency (HF), in normalized units (nu), and the LF/HF ratio. For statistical analysis, the paired t test was used with a level of significance of 5%.


No significant differences were observed in the time domain between two conditions. In the frequency domain, however, the LF bands presented significant higher values (0.6 ± 0.2 vs 0.8 ± 0.2) and HF bands lower values (0.4 ± 0.2 vs 0.2 ± 0.2) during NPPV compared with spontaneous breathing.


The NPPV application produced autonomic modulation adjustments, with a parasympathetic cardiac activity reduction and a sympathetic increase in healthy male youngsters.

Authors’ Affiliations

Departamento de Fisioterapia e Núcleo de Pesquisa em Exercício Físico, Universidade Federal de São Carlos, São Carlos, SP, Brazil


© BioMed Central Ltd 2007