Hypothesis

The Vibrant Soundbridge Floating Mass Transducer® (FMT) is part of a commercially available implantable hearing device in which the FMT can be placed in the round window niche (RW) or attached to a partial (V-PORP) or total ossicular replacement prosthesis (V-TORP) contacting the stapes head or footplate. The goal is to provide efficient transfer of sound vibration into the cochlea. The hypothesis is that the FMT location on the prosthesis is superior to the RW location.

Background

No direct comparisons of the three FMT sites have been performed using the same measurement location.

Methods

A new measurement method called the “Third Window” method (TW) was used in eleven fresh human temporal bones to compare the sites. A small hole was made into the scala tympani of the temporal bones preserving the endosteum. A reflective target was placed on the TW endosteum and displacement of the cochlear fluid was measured using a Polytec HLV-1000 laser Doppler vibrometer. The input to the FMT at all locations was a constant 316 millivolts (mV); the frequency range was 0.5 to 0.8 kHz.

Results

The V-PORP and V-TORP FMT locations both provided statistically significant better performance above 1.0 kHz than the RW site, but not below that frequency. The V-PORP and V-TORP responses were similar at all test frequencies.

Conclusion

In this temporal bone model, the FMT provided better higher frequency performance when attached to a PORP or TORP than in the RW niche.

Monitoring and assessing of patient respiratory function during conscious sedation are important because many drugs used for conscious sedation produce respiratory depression and subsequent hypoventilation. The purpose of this study is to assess the value of a dynamic air-pressure sensor for respiratory monitoring of clothed patients. Eight clothed adult volunteers were reclined on a dental chair positioned horizontally. The air bag for measuring air-pressure signals corresponding to respiration was placed on the seat back of the dental chair in the central lumbar area of the subject. The subject breathed through a face mask with a respirometer attached for measuring expiratory tidal volume. The air-pressure signals corresponding to respiration were obtained and the time integration values for air pressure during each expiration (∫Pexp) were calculated. The expiratory tidal volume (TVexp) was measured simultaneously by respirometer. The relationship between TVexp and ∫Pexp for each subject was assessed by a Pearson correlation coefficient. A strong correlation between TVexp and ∫Pexp was observed in all subjects. Measuring ∫Pexp by dynamic air-pressure sensor makes it possible to estimate respiratory volume breath by breath, and the respiratory pressure–time integral waveform was useful in visually monitoring the respiration pattern. We believe that in the future this device will be used to monitor respiratory physiology in clothed patients, contributing to safer sedative procedures.

For dental outpatients undergoing conscious sedation, recovery from sedation must be sufficient to allow safe discharge home, and many researchers have defined "recovery time" as the time until the patient was permitted to return home after the end of dental treatment. But it is frequently observed that patients remain in the clinic after receiving permission to go home. The present study investigated "clinical recovery time," which is defined as the time until discharge from the clinic after a dental procedure. We analyzed data from 61 outpatients who had received dental treatment under conscious sedation at the Hiroshima University Dental Hospital between January 1998 and December 2000 (nitrous oxide-oxygen inhalation sedation [n = 35], intravenous sedation with midazolam [n = 10], intravenous sedation with propofol [n = 16]). We found that the median clinical recovery time was 40 minutes after nitrous oxide-oxygen sedation, 80 minutes after midazolam sedation, and 52 minutes after propofol sedation. The clinical recovery time was about twice as long as the recovery time described in previous studies. In a comparison of the sedation methods, clinical recovery time differed (P = .0008), being longer in the midazolam sedation group than in the nitrous oxide-oxygen sedation group (P = .018). These results suggest the need for changes in treatment planning for dental outpatients undergoing conscious sedation.

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