Correction of hypercapnia improves cognitive efficiency and attention in a brain-injured patient

Abstract

Correction of obstructive sleep apnea (OSAS) by non-invasive continuous pressure ventilation (CPAP) allows an improvement of attentional and executive functions, especially post-stroke. On the other hand, in chronic obstructive pulmonary disease, correction of hypercapnia by bilevel positive airway pressure ventilation (BiPAP) improves cognitive impairment. We present a case of a brain-injured patient who remains hypercapnic despite an effective CPAP for the correction of an OSAS. We present a 36-year-old patient with visuo-spatial disorders, dysexecutive syndrome, cerebellar syndrome, swallowing disorders after a rupture of a right vertebral artery aneurysm 2 years before. Oral feeding by adapted texture (mixed), tracheotomy, CPAP for OSAS for several months were needed. We performed cognitive assessments (MoCA: Montreal Cognitive Assessment and BAWL: Attentional Battery William Lennox), pre- (T1) and post- (T2) correction of hypercapnia by night BiPAP, 2 months later. After correction of hypercapnia (T1 PaCO 2 = 7.36 kPa or 55 mmHg then T2 PaCO 2 = 5.86 kPa or 44 mmHg), improvement of: Global cognitive efficiency (MoCA score: + 4/30); Attention (MoCA attention items: +2/6); Simple reaction times (BAWL: –32 ms, from percentile 5 at T1 to percentile 15 at T2); Memory encoding (MoCA 5 words test: + 2/5 points and no false memories anymore). In addition, dysphagia improves by mealtime reduction (50 min versus 1h40) and laryngeal penetration decrease, which allows a withdrawal of the tracheotomy. In this case, the improvement of global cognitive capacities, attention and cognitive processing speed seems to result from the decrease of capnia. The persistence of sequelae of the intracranial aneurysm rupture (specially visuo-spatial and cerebellar) suggests that improvements on cognitive functions stem from the correction of hypercapnia. This case suggests the importance of a normalization of capnia in brain-injured patients with ventilatory disorders to improve the cognitive (global and attentional) capacities and autonomy in daily life (feeding and tracheotomy withdrawal). Larger studies are needed to confirm this.