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Relationships of labyrinthine fluid pressures and blood flow
Insights
This study found that labyrinthine blood flow in cats lacks autoregulation. Changes in systemic arterial pressure directly impact perilymph pressure, suggesting a link to local blood flow when the cochlear aqueduct is blocked.
Area of Science:
- Physiology
- Neuroscience
- Otolaryngology
Background:
- Cerebral blood flow autoregulation is well-established.
- Similar autoregulation of labyrinthine blood flow has been hypothesized but not proven.
- The relationship between systemic pressure and inner ear fluid pressure is not fully understood.
Purpose of the Study:
- To investigate the autoregulation of labyrinthine blood flow.
- To determine the influence of systemic arterial pressure changes on perilymph and cerebrospinal fluid (CSF) pressures.
- To examine the role of the cochlear aqueduct (CA) in pressure regulation.
Main Methods:
- Experiments were conducted on cats with a blocked cochlear aqueduct (CA).
- Systemic arterial pressure, perilymph pressure, and CSF pressure were monitored.
- The influence of CSF and central venous pressures on perilymph pressure was assessed.
Main Results:
- No direct correlation was observed between systemic arterial pressure and CSF pressure, attributed to cerebral blood flow autoregulation.
- CSF and central venous pressures had minimal and delayed effects on perilymph pressure with a blocked CA.
- A direct correlation was found between systemic arterial pressure and perilymph pressure, mediated by local labyrinthine blood flow.
Conclusions:
- Labyrinthine blood flow does not appear to be autoregulated.
- There is a direct relationship between labyrinthine fluid pressure and blood flow when the cochlear aqueduct is obstructed.
- Systemic arterial pressure directly influences inner ear pressure via local blood flow changes.
Abstract:
Control of labyrinthine blood flow analogous to the autoregulation of cerebral blood flow has been suggested but not experimentally demonstrated. This study concerns the influence of systemic arterial pressure changes on the perilymph and CSF pressures in cats with the cochlear aqueduct (CA) blocked. No direct correlation was found between changes in arterial and CSF pressure. This seemed to be due to the efficient autoregulation of the global cerebral blood flow--a main factor for CSF pressure regulation. The CSF and central venous pressures induced little and much delayed influence on the perilymph pressure when the CA was blocked. However, there was a direct correlation between changes in systemic arterial pressure and the perilymph pressure. This relationship seemed to be mediated via changes in local labyrinthine blood flow. The study indicated a lack of autoregulation of labyrinthine blood flow and a direct correlation between labyrinthine fluid pressure and blood flow when the CA was obstructed.