Sudden deafness (SD) is a sudden or rapidly progressive, partial or complete, typically unilateral sensorineural hearing impairment that has no known specific etiologic factor. This study was designed to compare, in a group of 168 consecutive patients with SD, the effect of anticoagulant therapy and carbogen inhalation therapy. Special attention was paid to the shape of the audiogram relative to the clinical outcome and the treatment modality. We found that the configuration of the audiogram of SD patients is prognostic of the outcome, and that patients with a low-frequency-sloping hearing impairment have a better prognosis compared to the patients with a high-sloping loss. Anticoagulant treatment was most effective in low-sloping hearing losses, while carbogen inhalation may be more effective for patients with high-sloping hearing losses.
The effects of carbogen (5% CO2: 95% O2) 10% CO2-in-air and 100% O2 on cochlear blood flow (CBF), skin blood flow (SBP), blood pressure (BP) and arterial blood gases were investigated in the anesthetized, respired or self-respiring guinea pig. In respired animals, CBF and SBF were increased with carbogen and 10% CO2-in-air and decreased with O2. BP was elevated with each gas. In freely breathing animals, only 10% CO2-in-air caused a small increase in CBF; both carbogen and O2 caused CBF to decrease. SPF changes were similar in form, but larger than those seen in respirated subjects. No consistent change in BP was seen during breathing of these mixtures. Arterial PO2 was increased by carbogen and 10% CO2-in-air for both groups. PCO2 increased for both CO2 gas mixtures during forced respiration; but in free-breathing animals PCO2 only increased for 10% CO2-in-air (normal PCO2 values were maintained with carbogen thorough increased breathing rate). The observed changes in CBF were consistent with a balance between a combined vasoconstrictive effect of PO2 and vasodilation effect of PCO2 on cochlear vessels. Analysis of cochlear vascular conductivity (CBF/BP) indicated that vasodilation was significant only with 10% CO2-in-air in respirated animals. In all other conditions the increased CBF apparently reflects the increase profusion pressure associated with respiration of each gas. For clinical purposes, while carbogen does not appear to directly cause vasodilation of cochlear vessels it does lead to an increased oxygenation of the cochlea blood and would appear to avoid the cochlear vasoconstriction caused by 100% O2.
Sudden sensorineural hearing loss (S-SNHL) is a common problem with a high recovery rate. However, little is known of the long-term prognosis of affected patients. The purpose of this follow-up study was to evaluate the long-term hearing results of S-SNHL patients. The sample consisted of 168 patients with S-SNHL treated with carbogen inhalation and/or anticoagulant therapy during the period 1982-89. A questionnaire was sent to these patients, and audiological investigations were carried out in a selection of these patients in 1997. Comparison of the different treatment methods showed that the difference observed in improvement of hearing was statistically significant between the carbogen inhalation and anticoagulant treatment groups. The hearing improvement achieved was stable for, on average, 8 years of follow-up. During the follow-up period, Ménière's disease was diagnosed in only 1 of the 116 patients who answered the questionnaire and no cases of acoustic neurinoma were diagnosed, indicating that establishment of a careful patient history and clinical and audiological investigations are sufficient for the diagnosis of S-SNHL. In general, the hearing improvement achieved in S-SNHL patients is stable during long-term follow-up.
The effects of repeated carbogen inhalation on peripheral tissue perfusion and oxygenation were assessed in 5 patients suffering from sudden hearing loss by means of continuously measured subcutaneous tissue oxygen and carbon dioxide tension, transcutaneous oxygen tension, laser Doppler red cell flux, and fingertip temperature. The subcutaneous oxygen tension increased clearly during the carbogen inhalation periods, and also, a smaller increase in subcutaneous carbon dioxide tension was simultaneously noticed. The changes in transcutaneous oxygen tension were even greater and the latency was shorter as compared with the subcutaneous gas tensions. The laser Doppler measurements showed no signs of vasoconstriction during the study. In conclusion, carbogen inhalation increases peripheral tissue oxygenation without microvascular vasoconstriction and with only a minor retention of carbon dioxide.
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