In his comprehensive review of the hyperventilation syndrome1 Gardner points out the difficulties in terminology and definition that have dogged this complicated and confused area. As he states, it is physiologically inappropriate to use the term “hyperventilation” in the absence of demonstrated hypocapnia. The term “hyperventilation syndrome” has, however, gained wide currency both in research studies and in clinical practice, often without precise diagnostic criteria being specified or hypocapnia rigorously demonstrated. This situation may …