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. 2007 Nov;30(11):1503-8.
doi: 10.1093/sleep/30.11.1503.

Sonographic measurement of lateral parapharyngeal wall thickness in patients with obstructive sleep apnea

Kin-Hung Liu  1 , Winnie C W Chu, Kin-Wang To, Fanny W S Ko, Mabel W C Tong, Jeff W S Chan, David S Hui
Affiliations

Sonographic measurement of lateral parapharyngeal wall thickness in patients with obstructive sleep apnea

Kin-Hung Liu et al. Sleep. 2007 Nov.

Abstract

Introduction: Lateral parapharyngeal wall (LPW) thickness may be a predominant anatomic factor causing airway narrowing in apneic subjects. In this study, we explored sonographic measurement of the LPW thickness and compared the results with LPW thickness measured by magnetic resonance imaging (MRI). We also investigated the association between sonographic measurement of LPW thickness and apnea-hypopnea index (AHI).

Method: Seventy-six patients with suspected obstructive sleep apnea (OSA) underwent ultrasound examination of LPW thickness after overnight polysomnography. Fifteen out of 76 subjects also participated in correlation and reliability studies of sonographic and MRI measurements of LPW thickness.

Results: There was good correlation between measurements of LPW thickness on ultrasound and MRI (r = 0.78, P = 0.001), although Bland-Altman analysis indicated overestimation of LPW thickness by ultrasound, when compared with the LPW as measured by MRI. The sonographic measurement of LPW thickness had high reproducibility, with intraclass correlation coefficients of 0.90 and 0.97 for intraoperator and interoperator reliability, respectively. Fifty-eight subjects with significant OSA (AHI > or = 10/h) had a higher body mass index, larger neck circumference, and greater LPW thickness measured by ultrasound than those (n = 18) with an AHI of less than 10 per hour. LPW thickness had a positive correlation with AHI on univariate analysis (r = 0.37, P = 0.001). On multivariate analysis, LPW thickness had a positive independent association with AHI after adjustment for age, sex, neck circumference, and body mass index. The positive association of LPW thickness with AHI remained significant in both univariate and multivariate analyses of men only (n = 62).

Conclusions: Sonographic measurement of LPW thickness is a novel and reliable technique and had good correlations with measurement by MRI and the severity of OSA. Ultrasound may provide an alternative imaging modality with easy accessibility and lower cost in OSA research.

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Figures

Figure 1
Figure 1
Scanning position of the lateral parapharyngeal wall. Patient lies supine on a 350 soft pad, with the infraorbital meatal baseline perpendicular to the scanning table. The transducer is placed longitudinally on the lateral side of the neck, just inferior to the occiput. The dotted line indicates the infraorbital meatal baseline.
Figure 2
Figure 2
Ultrasound image of the lateral parapharyngeal wall. The internal carotid artery is shown by Doppler imaging (long arrow), and the lateral wall of pharynx is represented by the echogenic interface (arrow heads) while the lumen cannot be clearly appreciated due to complete obscuration by gas shadowing (open arrow). The lateral parapharyngeal wall thickness is measured with caliber x——x.
None
Cross-sectional magnetic resonance image (MRI) showing measurement of the lateral parapharyngeal wall (LPW) thickness at the retropalatal level. ◀—▶indicates the LPW-transverse thickness measured on MRI. Lateral parapharyngeal fat pads are indicated by open arrows, airway is indicated by arrow head and internal carotid arteries are indicated by curved arrows. ⇠⇢ Indicates the LPW-oblique thickness measured on MRI.
Figure 4
Figure 4
Pearson correlation between the lateral parapharyngeal wall (LPW) thickness on ultrasound and LPW-transverse thickness measured by magnetic resonance imaging (MRI).
Figure 5
Figure 5
Bland-Altman plot demonstrates poor agreement between lateral parapharyngeal wall (LPW)-transverse thickness measured by magnetic resonance imaging (MRI) and LPW thickness measured by ultrasound. Due to the differences in both the site and the plane of measurements, all LPW thickness measurements are overestimated on ultrasound (limits of agreements: −0.62cm; −2.54cm).
Figure 6
Figure 6
Bland-Altman plot demonstrates closer agreement between lateral parapharyngeal wall (LPW)-oblique thickness on magnetic resonance imaging (MRI) and LPW thickness on ultrasound, with limits of agreements: (1.28cm; −1.30cm).
Figure 7
Figure 7
Pearson correlation between the lateral parapharyngeal wall thickness measured on ultrasound and the apnea-hypopnea index.
See this image and copyright information in PMC

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