Methods and clinical significance of studying chemical drives.

Studying chemical control of ventilation implies evaluation of both chemoreceptor functions taken into account however the mechanical factors influencing the effector organs. The role of abnormal chemical drives has been demonstrated in COPD patients. More recently the role of abnormal chemical drives was studied during sleep. Absent or severely depressed drives may facilitate the development of central apneas and hypoventilation. High drives may lead to periodic breathing eventually with central apneas as well. Most intriguing therefore is the role of chemical drives in the pathogenesis of the obstructive and central sleep apnea syndrome. There is accumulating evidence that fluctuations in the drive to breathe may adversely affect the upper airway patency and facilitate upper airway closure and obstructive apneas. Interaction with chemical drives (eg by administration of acetazolamide) has been shown to improve central (and eventually also obstructive) sleep apnea. Studying chemical drives will probably be clinically useful in solving the complex mechanisms controlling ventilation during sleep in patients with and without underlying airway or lung disease.