Galioto GB (eds): Tonsils: A Clinically Oriented Update. Adv Otorhinolaryngol. Basel, Karger, 1992, vol 47, pp 260-266

Measurement of Mesopharyngeal Pressure in Patients with Obstructive Sleep Apnea Yasuo Koike, Kayoko Takeichi, Tatsuya Ishida, Mikio Yamaguchi, Shin-ya Ohtsu Department of Otolaryngology, University of Tokushima School of Medicine, Tokushima, Japan

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Many methods and techniques have been proposed for diagnosis of upper airway obstruction during sleep since Guilleminault et al. [1] reported the existence of sleep apnea syndrome due to airway obstruction in infants and children. These methods include the measurement of respiratory motion of the thorax, the registration of electroencephalogram, recording of 02 and CO 2 levels in the blood flow, and many others. Since the results of measurement with these methods have been considerably variable, however, it has not been easy to precisely assess the degree of airway constriction, or obstruction, from the results of measurement with these methods. Also, no definite means of determining the exact site of obstruction within the airway has so far been available. Although lateral X-ray films have been widely adopted for this purpose, it has been often difficult to pinpoint the virtual location of obstruction inside the upper respiratory system on these films. There is no need of lengthy explanation for the need of establishing an objective and reliable method for evaluating the degree of, and the site of, upper airway obstruction. On the other hand, close observation of the infants and children with sleep apnea syndrome suggested the existence of a strong negative pressure within the respiratory system of these patients. The measurement of air pressure inside the respiratory system has thus been undertaken, in the hope that this pressure may serve as an indicator of the degree of constriction, or obstruction, in the upper respiratory system. This pressure infor-

Mesopharyngeal Pressure and Sleep Apnea

261

Table 1. Classification of the subjects based on clinical symptoms and signs Group

A B

C D

Sex, m:f (total)

36:12 38:22 41 :16 27:9

(48) (60) (57) (36)

Symptom snoring

retracting respiration

(-) (+) (+) (+)

(-) (-)

(+) (+)

sleep apnea

(-)

(-) (-) (+)

mation was thought to be useful to elucidate the site of obstruction also if it could be measured at multiple locations inside the respiratory system.

The subjects of the present study consisted of 201 patients with adenotonsillar hypertrophy. The ages of the patients ranged from 7 months to 14 years. Otolaryngological examinations were made on these children while they were awake, and lateral X-ray pictures were taken to assess the degree of adenotonsillar hypertrophy. These subjects were classified into 4 groups on the basis of clinical symptoms and signs, as depicted in table 1. Group A consisted of the patients without evidence of upper airway obstruction. The cases in group B had snoring in common, without retracting respiration and sleep apnea episode. The children in group C had snoring and retracting respiration, but they had no episode of sleep apnea. The subjects in group D had sleep apnea, along with snoring and retracting respiration. An all-night polysomnography including mesopharyngeal pressure recording was performed on these subjects. Figure 1 shows the block diagram of the polysomnography employed. A miniaturized pressure transducer (Gaeltec S7b) was inserted into the mesopharynx through the nostril of the subject, and placed just below the palatine tonsils (fig. 2). The absolute value of the maximum amplitude of the pressure wave recorded during expiration and inspiration (mesopharyngeal pressure amplitude: MPA) was measured from the recorded data, and was adopted as an indicator of the negative pressure inside the respiratory system. Other parameters of the polysomnography included the breath stream sensed by a thermistor, the thorax movement picked up with a strain gauge, and the sound of snoring. In 46 cases the level of oxygen saturation was also registered with an oxygen saturation monitor (Criticare Systems 501), as shown in figure 1. The polysomnography was repeated I week after adenotonsillectomy on 59 patients, in order to observe the effect of surgery on the recorded parameters. Various quantitative indices including apnea index (AI) and arterial oxygen saturation (Sa02) were calculated from the recorded polysomnograms and were compared with the severity of clinical symptoms and signs.

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Materials and Methods

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Fig. 1. Block diagram of polysomnography.

Figure 3 shows the MPA values during sleep for the 4 subject groups. The MPA values for the patients in groups B, C, and D were significantly higher than those for the children in group A. The cases in group D, with obstructive sleep apnea, revealed evidently high MPA values. The children in group C, with retracting respiration and snoring, showed moderately high MPA values. The subjects in group B, with snoring only, demonstrated slightly high MPA values. It is apparent that the MPA value is closely associated with the severity of clinical symptoms and signs. The symptoms and signs of upper airway obstruction, such as obstructive sleep apnea, retracting respiration, and snoring, were apparently

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Results

Mesopharyngeal Pressure and Sleep Apnea

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improved after adenotonsillectomy. Figure 4 discloses the MPA values for each subject group after the surgery. The MPA values are seen to be remarkably reduced after the operation, and the difference in the mean MPA value among different subject groups was not significant any more. The close relationship between the MPA value and the degree of airway constriction can be known from this fact also. Figure 5 illustrates polysomnograms for 3 representative cases. The tracings on the left side (case 1) show the data for a boy with retracting respiration and snoring. The AI value for this patient was 0.7, which was within the normal limits, and the Sa02 was also within the normal range. The downward deviation of the mesopharyngeal pressure wave increased with time, however, and the MPA reached 63 em H 20, indicating the existence of a strong negative pressure. The tracings in the middle (case 2) demonstrates the data for a patient with retracting respiration and snoring. This patient could not be diagnosed as obstructive sleep apnea syndrome (OSAS) on the conventional standard, since the AI value for this case was 2.8 (within normal limits). This case, nevertheless, revealed an MPA value

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Fig. 2. Placement of the miniaturized pressure transducer in the mesopharynx.

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Measurement of mesopharyngeal pressure in patients with obstructive sleep apnea.

Galioto GB (eds): Tonsils: A Clinically Oriented Update. Adv Otorhinolaryngol. Basel, Karger, 1992, vol 47, pp 260-266 Measurement of Mesopharyngeal...
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