Underestimation of the peak flow variability in asthmatic children: evaluation of a new formula.

@article{Vargas2005UnderestimationOT,
  title={Underestimation of the peak flow variability in asthmatic children: evaluation of a new formula.},
  author={Mario H. Vargas and H{\'e}ctor Hern{\'a}n Ruiz-Guti{\'e}rrez and Concepci{\'o}n Espinosa-Serafin and Guillermo Z{\'u}{\~n}iga-V{\'a}zquez and Mar{\'i}a Elena Yuriko Furuya},
  journal={Pediatric pulmonology},
  year={2005},
  volume={39 4},
  pages={325-31}
}
Asthma guidelines suggest evaluation of peak expiratory flow (PEF) variability, but timing for the two PEF measurements is not mentioned. Usual formula calculates amplitude as percentage of mean day-night PEF values. Since PEF circadian changes follow a sinusoidal function, we reasoned that variability might be calculated by measuring PEF at 4 pm (PEF(1… CONTINUE READING