The Effects Of Carbogen Inhalation On Microvasculature Within Lateral Wall Of Cochlear And Hearing Function Following Acute Acoustic Trauma

Part One An intravital micrscopic observation method for cochlear microvasculature: its establishment and evaluationObjective:To investigate the microcirculation in the cochlear lateral wall in vivo, to improve the experimental method and evaluate its effectivenessMethods:The lateral walls of the cochlear in guinea pigs were carefully fenestrated and 3 indications were measured in stria vascular: the RBC cells column diameter (RBCCD), the blood flow velocity (BFV) and the blood flow states (BFS). Hearing level was assessed with auditory brainstem response (ABR) and the histology of the cochlear was studied with segmented basilar membrane.Results: In 15 minutes after the fenestration of the cochlear lateral wall, the blood flow in the microvasculature appeared normal, there was no aggregation of the RBC or microthrombus. The diameter of the RBC column was stable. The ABR threshold shift as well as the morphology of the basilar membrane of Corti's organ indicated no significant change compared with the control group.Conclusion: The improved experimental method for the study of microvasculature in cochlear lateral wall does not affect the normal microstructure as well as the blood flow in the cochlea. This method can achieve the real-time observation of the microcirculation in cochlear.Part Two The effects of carbogen inhalation on microvasculature within lateral wall of cochlear following acute acoustic traumaObjective:To explore the influence of carbogen on lateral wall microvasc- ulature of cochlear after acute acoustic trauma. Methods:40 guinea pigs were divided into 4 groups: group A (noise damage), group B (carbogen inhalation), group C (noise exposure + carbogen inhalation), and group D (the control group without any treatment).The diameter of the column of RBCs(RBC column diameter,RBCCD),blood flow velocity(BFV) and blood flow states(BFS) in microvascu- lature were measured and described under stereomicroscope.Results:The microvasculature in group A demonstrated a blood flow in contrary direction, granuliform flow, granular slow flow, and the aggregated erythrocytes. The RBCCD decreased 12.1% compared with group D(P<0.05). The BFV in group B showed a laminar or laminar granular flow, and the RBCCD increased 20.7% compared with group D. The blood condition in group C was the same as group D - laminar granular blood flow; the blood flow with contrary direction was less than group A, and the RBCCD was 17.4% lager than that of group A.Conclusion:Carbogen can dilate the RBCCD and increase the BFV in stria vascularies. Carbogen inhalation may be alleviate the damage of noise exposure.Part Three The effects of carbogen inhalation on hearing function and hair cell following steady military noise exposeObjective : To investigate the protective effect of carbogen on cochlear in acute acoustic trauma.Methods :40 guinea pigs were randomly divided into2 groups, : group A was exposed to the noise of 120±2dB SPL for 5 hours (n = 20), group B was exposed to the same noise and then treated with carbogen inhalation(n = 20). Auditory brainstem response (threshold as well as latent period), arterial blood gas and the morphology of the segmented basilar membrane were analyzed.Results :ABR threshold shifts in two groups were similar up to about 78 dB SPL on day one .The noise-exposed control group showed threshold shifts (measured by auditory brainstem response, ABR) of up to 63 dB SPL on day 3, and up to 56.8 Db SPL on day 14. Carbogen- inhalation subjects had significantly smaller ABR threshold shifts on day 3 and 14. Hair cell loss was equally on day 14. The segmented basilar membrane of both groups indicated no stereocillia of hair cell loss or disorder.Conclusion :Carbogen inhalation can preserve hearing function following acute acoustic trauma.