Ventilatory response to CO2 in patients with snoring,obstructivehypopnoea and obstructive apnoea

Obstructive sleep apnoea (OSA) is caused by an obstruction of the upper airway. Sufficientsensitivity to CO₂ in the respiratory centre is known to be a critical factor for adequatetone in the upper airway muscles. The hypothesis of this study is, therefore, that the ventilatoryresponse to CO₂ is reduced in patients with OSA. Twenty-six patients who sufferedfrom snoring, 19 snoring patients with obstructive hypopnoea (OH) and 33 snoring patients withobstructive apnoea (OA), were studied. The control group consisted of 25 subjects from a randomsample with no history of snoring or daytime sleepiness. Tests of the hyperoxic and hypoxicventilatory response to CO₂ were performed, as well as static and dynamic spirometry.Subjects in the OA group displayed a higher hyperoxic (E_E/F_etCO _2hy=12·6 l min^?1/%) and hypoxic (E_E/F_etCO _2ho=15·7 l min^?1/%) ventilatory responseto CO₂ than patients with obstructive hypopnoea(E_E/F_etCO_2hy=8middot;6 l min^?1/%; E_E/F_etCO _2ho=15·2 l min^?1/%), snorers(E_E/F_etCO _2hy=8·4 l min^?1/%;E_E/F_etCO _2ho=12·7 l min^?1/%) and non-snorers(E_E /F_etCO _2hy=7·6 l min^?1/%;E_E/F_etCO _ho=9·6 l min^?1/%). Multiple regression analysis revealsthat neck circumference, apnoea index, oxygen desaturation index, PCO ₂ and sex (male gender) are correlated with E_E/F_etCO _2hy (R²=0·43).Multiple regression analysis also reveals that ERV (expiratory reserve volume) and sex (malegender) are correlated with E_E/F_etCO _2ho ((R²=0·21). Arguing against thehypothesis, patients with OSA displayed an increased hyperoxic and hypoxic ventilatory responseto CO₂ . Nocturnal apnoea frequency and the obesity factor in OSA may havecontributed to these results.