Dados do Trabalho

Título

Brain compliance behavior during sleep – Initial analysis of a pilot study.

Resumo

Background. Intracranial compliance represents the cranium's ability to tolerate an increase in volume without a corresponding increase in intracranial pressure. Little is known about the impact of brain compliance on sleep. Our objective is to evaluate the behavior of brain compliance during sleep stage and wakefulness, through pulses morphology (P1, P2, P3) of intracranial pressure and P2/P1 ratio.
Method. The assessment of brain compliance was performed using the non-invasive intracranial pressure (NICP) method through the Brain4care® device overnight simultaneously with the performance of type I polysomnography (Alice 6, Phillips Respironics®). We evaluated brain compliance data in the first 10 minutes of each of the following situations: wakefulness (V), sleep N2 (N2), sleep N3 (N3) and REM (REM).
Results. The patient did not complain in using the Brain4Care® device throughout the night. We obtained the following P2/P1 ratios: V= 1.40; N2=1.30; N3=1.01 and in REM=1.03.
The P2/P1 ratio was higher in wakefulness when compared to REM sleep (p > 0.001); higher in N2 when compared to REM sleep (p > 0.001); and higher during wakefulness when compared to sleep (N2, N3 and REM) (p > 0.001). The behavior of the P2/P1 ratio was similar when comparing N3 and REM; and when comparing N2 and wakefulness.
Discussion. The main finding of this pilot study was that the P2/P1 ratio decreased during the night's sleep, being higher during wakefulness and N2 sleep. Contrary to our hypothesis, in the REM sleep stage, we observed a decrease in brain compliance compared to wakefulness. Although still an isolated study, this is an interesting finding, as brain metabolism increases during REM sleep, equivalent to what is observed in wakefulness. However, brain compliance in REM sleep is quite low, similar to N3 sleep, where brain metabolic activity is lower relative to other stages. Another possible cause of the increase in the P2/P1 ratio may be related to the presence of some hypopneas that occurred during N2 sleep, however these same obstructive events occurred in REM sleep.
The impact of sleep breathing disorders on brain compliance will be assessed in the future.
Conclusion. Brain compliance appears to be associated with sleep stages and is progressively reduced from wakefulness to N3 sleep. Brain compliance is no different in stage N3 and REM. Although sympathetic activity is higher in REM sleep, there was no increase in compliance during this period of high brain activity.

Palavras Chave

intracranial pressure; brain compliance; polysomnography; sleep; wakefulness.