Am. J. Respir. Crit. Care Med., Vol 154, No. 6, Dec 1996, 1741-1747.
Role of chemosensitivity in intrathoracic pressure changes during obstructive sleep apnea
E Sforza, A Boudewijns, B Schnedecker, M Zamagni and J Krieger
Sleep Disorders Unit, University Hospital Strasbourg, France.
We tested the hypothesis that the awake ventilatory response to hypoxia and
hypercapnia may contribute to the variability of respiratory effort
developed in response to upper airway obstruction in obstructive sleep
apnea syndrome. The polygraphic recordings of 38 patients diagnosed as
having obstructive sleep apnea on the basis of an apnea+hypopnea index
greater than 10 were examined. All subjects received hypoxic and
hypercapnic ventilatory tests the day before the nocturnal polysomnography.
Thirty apneas during non-rapid eye movement (NREM) sleep and at least 10
apneas during rapid eye movement sleep were analyzed. For each considered
apnea, we measured esophageal pressure (Pes) swings during the first three
breaths preceding apnea and during the first three and last three occluded
efforts occurring during the apnea. We considered as indices of respiratory
effort the overall increase from the minimum to the maximum Pes (delta
Pes), the rate of increase of Pes during apnea (RPes), and the maximal
respiratory effort at the end of apnea (Pes max fin). In NREM sleep, all
three indices of respiratory effort were correlated positively with the
awake ventilatory response to hypoxia or hypercapnia and with the apnea
index. No correlation was found between the indices of respiratory effort
and body mass index, age, pulmonary function tests, awake blood gases,
apnea duration, and apnea desaturation. In rapid eye movement sleep, none
of the considered variables predicted the degree of respiratory effort. In
conclusion, our results suggest that the degree of ventilatory response to
upper airway occlusion in obstructive sleep apnea may be influenced by the
sensitivity of central neural drive to chemical stimuli.
