Effects of positive end-expiratory pressure, carbon dioxide and body position on intracranial pressure measured by ultrasound assessment of optic nerve sheath diameter

Abstract

Introduction. The optic nerve is surrounded by layers of meninges and cerebrospinal fluid, which is why intracranial pressure affects the optic nerve sheath. Noninvasive measurement of the optic nerve sheath diameter is simple, accurate, repeatable and with minimal side effects. Effects of positive end-expiratory pressure on intracranial pressure. The application of positive end-expiratory pressure plays a significant role in improving gas exchange, but it leads to an increase in intrathoracic and central venous pressure, cerebral blood volume, reduces arterial and cerebral perfusion pressure and thus futher increases intracranial pressure. The effect of positive end-expiratory pressure depends on basal intracranial pressure and respiratory system compliance. Effects of carbon dioxide on intracranial pressure. Hypercapnia leads to cerebral vasodilatation and increases cerebral blood flow and intracranial pressure. Hypocapnia reduces intracranial pressure, but its prolonged effect may lead to cerebral ischemia. Effects of body position on intracranial pressure. Body position affects intracranial pressure, primarily by affecting cerebral venous drainage. Conclusion. Body position, application of positive end-expiratory pressure, and changes in carbon dioxide can affect intracranial pressure, which is why its monitoring is of importance. Numerous studies show that their effects on intracranial pressure can be easily monitored by ultrasound assessment of optic nerve sheath diameter.