Letters Section Editor: Robert M. Golub, MD, Senior Editor.
To the Editor: In their randomized trial, Dr Cohen and colleagues1 studied the use of high-flow oxygen in the treatment of cluster headache. There are some points of clarification that would help with interpreting the study.
First, for all drugs there is a dosing system, but for oxygen it can be occult. The fraction of inspired oxygen (FIO2) is the volume percentage of oxygen that is inhaled and is analogous to the absorbed (not the prescribed) dose for other drugs. Although in the past FIO2 was invasively sampled through the trachea, it can be measured noninvasively and calculated by parameters obtained from mass spectrometry for different breathing systems.2 Because the main dosing system of normobaric oxygen therapy is FIO2, knowing the range of effective FIO2 delivered in this trial would allow prescribing oxygen by different breathing systems to treat cluster headache.
Haghshenas SM, Panahkhahi M, Taheri A. High-Flow Oxygen for Cluster Headache. JAMA. 2010;303(15):1481. doi:10.1001/jama.2010.441