Incorrect performance of the breath hold method in the old underestimates cerebrovascular reactivity and goes unnoticed without concomitant blood pressure and end-tidal CO(2) registration.

BACKGROUND AND
PURPOSE: The breath hold maneuver is a convenient and frequently used method to assess cerebrovascular reactivity (CR). This study aimed to assess feasibility and reproducibility of this method in healthy older persons.
METHODS: Twenty-five healthy volunteers, aged 75 (SD 4) years, performed 2 consecutive breath holds after careful instruction. Blood pressure (BP-Finapres), cerebral blood flow velocity (CBFV-Transcranial Doppler), and end-tidal CO(2) (capnography) were measured continuously. As reference standard, CR was determined by hyperventilation and CO(2) -inhalation. These measurements were repeated after 3 months in 11 randomly selected subjects.
RESULTS: Despite apparent compliance with instructions during performance of breath holding, only 29 of the 50 breath holds (58%) had been accurately executed, which was identified only from BP and end-tidal CO(2) measurements. Incorrect breath holds led to underestimation of CR. For valid breath holds, reproducibility was comparable to the reference method (coefficient of variation 19.4% and 17.6%, respectively).
CONCLUSION: The number of inaccurate breath holds was unacceptably high, moreover, these could not be identified from CBFV registrations alone. Therefore, reports of CR based on breath holds in older subjects without coregistration of BP and either end-tidal CO(2) or chest-expansion should no longer be acceptable.