Nasal Air Puff Promotes Default Mode Network Activity in Mechanically Ventilated Comatose Patients: A Noninvasive Brain Stimulation Approach

Objectives: Coma state and loss of consciousness are associated with decreased brain activity, including and especially gamma oscillations, which are involved in neural network integrity, as well as the default mode network (DMN). This condition can be aggravated by mechanical ventilation since nasal respiration, known to drive functional neural oscillations, is diminished. Hence, we proposed that rhythmic nasal air-puffing in mechanically ventilated comatose patients may promote brain activity and improve network connectivity.

Materials and Methods: We assessed the activity, complexity, and connectivity of the DMN using electroencephalography (EEG) in fifteen comatose patients (eight males) admitted to the intensive care unit due to opium poisoning before and during the application of nasal air-puff. Air-puffing into the nasal cavity was done using a nasal cannula via an electrical valve (open duration of 630ms) with a frequency of 0.2 Hz.

Results: Our analyses demonstrated that nasal air-puffing enhanced gamma power (30-40 Hz) oscillation in the DMN. Additionally, the coherency and synchrony between DMN regions were increased during nasal air-puffing. Recurrence quantification analysis (RQA) analysis revealed that global complexity and irregularity of EEG, which is typically seen during wakefulness and conscious state, were increased during rhythmic nasal air-puffing.

Conclusions: Rhythmic nasal air-puffing, as a non-invasive brain stimulation method, opens a new window into modifying the brain connectivity integration in comatose patients, which potential can influence their outcome by reducing the adverse effect of mechanical ventilation on brain activity.