Nasal blood flow.

Although the assessment of allergic reactions was subjective for many years, it is now possible to evaluate nasal blockage objectively by measuring nasal airway resistance. To explore the pathophysiology of nasal blockage, however, it is necessary to analyze the separate components of obstruction, including secretions, cellular infiltrates, and microcirculatory parameters. The preferred techniques for measuring nasal mucosal blood flow are laser-Doppler velocimetry and radioactive xenon washout. Laser-Doppler velocimetry allows the measurement not only of blood flow but also of blood volume, red blood cell speed, and pulsatility of flow. It also permits continuous measurement of microcirculatory parameters over time. This technique has been used to assess the nasal microvascular response to neurohormones, antigenic challenge, and histamine challenge with and without antihistamine pretreatment.