Recorder for assessment of upper airway disorders

A simple audio data logger for objective assessment of snoring in the home

We have developed a portable device for patient use in logging snoring loudness in the home, for guiding treatment decisions and measuring the clinical effectiveness of treatment. The device uses a free field microphone and is positioned on a bedside table. The prototype devices contain no inherently expensive components and are simple to operate (producing only 5% patient error to date). They are portable, battery powered, rugged and produce digital data which are easily and automatically analysed, and these design parameters enable the devices to be used for first line patient assessment. Of the 75 recordings made so far from 30 patients, 85% were successful, yielding clinically useful data. Because it is sound levels which are recorded and not replayable sounds, patient privacy is maintained, resulting in excellent patient acceptance (to date no patient has refused). The device has a dynamic range of 45-90 dB sound pressure level and a frequency range of 30 Hz-5 kHz. Because snoring intensities often vary significantly throughout the night the device can measure continuously over 8 h.

Snoring assessment: do home studies and hospital studies give different results?

We have developed a device (Glan Clwyd Snore Box) suitable for the objective measurement of the loudness and duration of snoring. The device is simple for the patient to operate, portable, battery powered, and able to produce objective results. We have used the Snore Box to record the snoring at home and during sleep studies in the hospital. Twenty-nine patients were studied. Overall the Snore Index recorded in the home was greater than in the hospital (P < 0.001), the average difference being 67 snores/h. We conclude that snoring is more appropriately assessed at home than in the hospital. We suggest the deficit arises from sleeping in an unfamiliar environment and the presence of several wires connecting the patient to the recording monitor which interfere with natural sleep in the hospital setting.

Objective assessment of snoring before and after laser-assisted uvulopalatoplasty

Laser-assisted uvulopalatoplasty (LAUP) is an outpatient staged surgical procedure for the treatment of snoring. Each patient undergoes a series of procedures with the end point being patient and bed partner satisfaction in most cases. The purpose of this study was to objectively evaluate the frequency, pattern, and volume of snoring in patients prior to and following each LAUP procedure. A sonographic device, SNAP, which records oronasal respiration, was used to assess patients at home. A digital analysis of the frequency, pattern, and volume was then performed. Twenty-seven patients have been completely evaluated with this recording device. The findings demonstrate that the LAUP procedure alters the snoring sound. The maximum, average, and velum-like respiratory noise loudness all showed a statistically significant decrease when comparing the preoperative snoring to the final recording after treatment was completed. In addition, the fundamental frequency of the snoring increased significantly after each LAUP procedure. No change was seen in the snoring index following treatment. These objective results correlated well with the subjective responses of the patients and their bed partners. These findings are consistent with the hypothesis that the LAUP procedure alters snoring in a favorable manner by both objective data and subjective accounts.

Overnight pulse oximetry in snoring and non-snoring children

The effect of snoring on overnight pulse oximetry recordings in the paediatric community was investigated. A random sample of 222 children up to 10 years of age from the town of Frome, Somerset, UK, had overnight pulse oximetry performed in the home environment. The oximetry recordings obtained from 58 snoring and 164 non-snoring subjects were compared. No clinically relevant difference in oxygen saturation level could be detected between these two groups of children. In conclusion, snoring in children up to 10 years of age is common, 11% often snore. It is not associated with hypoxia as measured by overnight pulse oximetry. This would suggest that surgical intervention for the symptom of snoring alone is not indicated.

Obstructive sleep apnea

Obstructive sleep disorders and apnea are commonly seen in children of all ages. The obstruction usually causes snoring and varying periods of interrupted breathing during sleep. Obstructive sleep disorders cause multiple physiologic disturbances and should be treated before they become severe.

Reliability of sleep sonography in detecting upper airway obstruction in children

In children, lymphoid hyperplasia is by far the most common cause of airway obstruction during sleep, but the determination as to presence or degree of obstruction is seldom made objectively, because of the expense and stress of polysomnography. If audio recordings are made by parents at home with standardized equipment, however, obstruction can be recognized readily. Such recordings obtained from 50 patients were computer processed and the resulting displays were independently rated by two judges. Interobserver correlation was 0.87 and split-half reliability was 0.83, demonstrating very good reliability of the processing and scoring procedures. Recordings made on successive nights were highly consistent as well (test-retest reliabilities of 0.78 and 0.86 for the two raters). This recording method, which is well accepted by parents and children, has both clinical and research value in the assessment of airway obstruction.

Relief of upper airway obstruction by adenotonsillectomy

Adenotonsillectomy is often performed to relieve upper airway obstruction, even in children who do not present with severe apnea. Although adenotonsillectomy provides dramatic relief from obstructive sleep apnea, little evidence is available as to the efficacy of surgery in the far more prevalent cases of partial airway obstruction. We report the results of a prospective study of 100 children with adenotonsillar obstruction (without severe apnea) and 50 age-matched control children. The majority of patients exhibited appreciable sleep disturbances preoperatively, as compared to controls, and had substantial postoperative improvement, as demonstrated by parental questionnaire and sleep sonography--the computer-aided analysis of respiratory sounds. Mouth breathing and behavior problems were also prevalent preoperatively and were affected positively by adenotonsillectomy. It appears that surgery in such cases can have far-ranging benefits, even for the child whose obstruction does not demonstrate severe apnea.

The lateral neck radiograph in adenotonsillar hyperplasia

In this study we have considered whether the lateral neck radiograph is useful in predicting the degree of airway obstruction, and whether supine and erect views are more useful than a single film. We evaluated the supine and erect lateral neck radiographs of 50 patients with upper airway obstruction due to enlarged tonsils and adenoids. Our results show that the supine radiograph, which is technically easier to perform, is entirely satisfactory for appraising the size of the tonsils and adenoids, but that neither view tells us much about the degree of airway obstruction during sleep.