CT in the Evaluation of the Upper Airway in Healthy Subjects and in Patients With Obstructive Sleep Apnea Syndrome

doi:10.1378/chest.113.1.111

Chest

Volume 113, Issue 1, January 1998, Pages 111-116

https://doi.org/10.1378/chest.113.1.111 Get rights and content

Aim

To study if the caliber of the upper airway, measured by CT, allows us to distinguish patients with obstructive sleep apnea syndrome (OSAS) from healthy people.

Patients and methods

Sixteen OSAS patients (with an apnea-hypopnea index >10) and 39 healthy volunteers were studied. Polysomnography and CT of the upper airways during awake periods were performed in both groups. We used third-generation equipment (Toshiba model TCT 600QT). The area of the nasopharynx, oropharynx, and hypopharynx (in inspiration and expiration), the uvula diameter, and retropharyngeal tissue were evaluated. The simultaneous identification of the variables that differentiate between control and OSAS groups was determined by a multivariate discriminant model.

Results

The retropharyngeal tissue in OSAS men was greater than those of the control men (10.3±3.6 mm vs 6.4±2.7 mm; p<0.01). The multivariate analysis was performed on the 29 men (14 OSAS and 15 non-OSAS) who had information compiled in the selected parameters. The retropharyngeal tissue, expiratory hypopharynx, and uvular diameter are used to create a discriminant model (Wilks’ λ=0.556; p<0.01). Two non-OSAS and five OSAS patients were incorrectly classified by this model as members of the other group (total rate of error, 24.14%). Therefore, the point estimates of specificity and sensitivity are 86.67% and 64.29%, respectively, for this model. The Pearson correlation coefficient between body mass index and retropharyngeal tissue is 0.63 (p<0.001).

Conclusions

CT could play an important role in studying the upper airway in patients with OSAS. The determination of the retropharyngeal tissue by CT could be a useful procedure to evaluate OSAS.

Section snippets

Subjects Studied

Seventy patients were submitted to upper airway studies using CT between 1992 and 1994. Only 55 subjects completed the study, 36 men and 19 women, with an age range from 25 to 75 years (mean±SD: 45±11 years), 27 of whom were smokers (pack-year index >10).

Exclusion criteria of the 15 remaining were as follows: (1) lack of cooperation by the patient or incapacity to carry out the required inspirations-expirations (nine cases); (2) weight higher than 130 kg (three cases); and (3) technical failure

Results

The results obtained by comparing the mean values of the upper airway measurements between men and women in the control group are detailed in Table 1. The retropharyngeal tissue was wider in men than in women (6.4±2.7 mm vs 3.6±2.6 mm; p<0.05) as well as the inspiratory hypopharynx area (588.4±198.9 mm² vs 402.8±153.4 mm²; p<0.05). The inspiratory and expiratory oropharynx areas were also greater in men, although these differences are not statistically significant (p<0.1).

The results obtained

Discussion

Our study demonstrates that the upper airway measured by CT is different in OSAS patients than that from healthy subjects during the daytime. Among the parameters studied, the one that allows us to better differentiate between control and OSAS subjects is the RT.

Several methodologic points should be considered. We have used CT to evaluate the upper airway because of the following reasons: it presents an elevated accuracy; it is a quick and nonbothersome technique; cooperation by the patient is

References (29)

W Stanford et al.
Effects of awake tidal breathing, swallowing, nasal breathing, oral breathing, and the Müller and Valsalva maneuvers on the dimensions of the upper airway: evaluation by ultrafast computerized tomography
Chest
(1988)
V Hoffstein et al.
Roentgenographic dimensions of the upper airway in snoring patients with and without obstructive sleep apnea
Chest
(1991)
JW Bloom et al.
Risk factors in a general population for snoring: importance of cigarette smoking and obesity
Chest
(1988)
R Alvarez-Sala et al.
El síndrome de apnea del sueño
Med Clin (Barc)
(1986)
CE Sullivan et al.
Sleep apnea—pathophysiology: upper airway and control of breathing
TD Bradley et al.
Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea
N Engl J Med
(1986)
JR Galvin et al.
Obstructive sleep apnea: diagnosis with ultrafast CT
Radiology
(1989)
MG Stein et al.
Cine CT in obstructive sleep apnea
AJR Am J Roentgenol
(1987)
P Caballero et al.
La tomografía computarizada de la vía aérea superior en el síndrome de apnea del sueño
Med Clin (Barc)
(1995)
P Caballero et al.
Computertomographie der oberen Atemwege-kann sie neue Erkenntnisse zur Ursache des obstruktiven Schlafapnoesyndroms liefern
Atemweg Lungenkrank
(1994)

EF Haponik et al.

Computerized tomography in obstructive sleep apnea: correlation of airway size with physiology during sleep and wakefulness

Am Rev Respir Dis

(1983)

SR Ell et al.

Cine CT demonstration of nonfixed upper airway obstruction

AJR Am J Roentgenol

(1986)

ST Kuna et al.

Effects of nasal airway positive pressure on upper airway size and configuration

Am Rev Respir Dis

(1988)

N Yildirim et al.

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome

Am Rev Respir Dis

(1991)

Cited by (81)

Upper Airway Areas, Volumes, and Linear Measurements Determined on Computed Tomography During Different Phases of Respiration Predict the Presence of Severe Obstructive Sleep Apnea
2018, Journal of Oral and Maxillofacial Surgery
The objective of this study was to analyze the potential of using low-dose volumetric computed tomography (CT) during different phases of respiration for identifying patients likely to have severe obstructive sleep apnea (OSA), defined as a respiratory disturbance index (RDI) higher than 30.
A prospective study was undertaken at the Ramathibodi Hospital (Bangkok, Thailand). Patients with diagnosed OSA (N = 82) were recruited and separated into group 1 (RDI, ≤30; n = 36) and group 2 (RDI, >30; n = 46). The 2 groups were scanned by low-dose volumetric CT while they were 1) breathing quietly, 2) at the end of inspiration, and 3) at the end of expiration. Values for CT variables were obtained from linear measurements on lateral scout images during quiet breathing and from the upper airway area and volume measurements were obtained on axial cross-sections during different phases of respiration. All CT variables were compared between study groups. A logistic regression model was constructed to calculate a patient's likelihood of having an RDI higher than 30 and the predictive value of each variable and of the final model.
The minimum cross-sectional area (MCA) measured at the end of inspiration (cutoff point, ≤0.33 cm²) was the most predictive variable for the identification of patients likely to have an RDI higher than 30 (adjusted odds ratio [OR] = 5.50; 95% confidence interval [CI], 1.76-17.20; sensitivity, 74%; specificity, 72%,), followed by the MCA measured at the end of expiration (cutoff point, ≤0.21 cm²; adjusted OR = 3.28; 95% CI, 1.05-10.24; sensitivity, 70%; specificity, 68%).
CT scanning at the ends of inspiration and expiration helped identify patients with an RDI higher than 30 based on measurement of the MCA. Low-dose volumetric CT can be a useful tool to help the clinician rapidly identify patients with severe OSA and decide on the urgency to obtain a full-night polysomnographic study and to start treatment.
Passive movement of human soft palate during respiration: A simulation of 3D fluid/structure interaction
2012, Journal of Biomechanics
This study reconstructed a three dimensional fluid/structure interaction (FSI) model to investigate the compliance of human soft palate during calm respiration. Magnetic resonance imaging scans of a healthy male subject were obtained for model reconstruction of the upper airway and the soft palate. The fluid domain consists of nasal cavity, nasopharynx and oropharynx. The airflow in upper airway was assumed as laminar and incompressible. The soft palate was assumed as linear elastic. The interface between airway and soft palate was the FSI interface. Sinusoidal variation of velocity magnitude was applied at the oropharynx corresponding to ventilation rate of 7.5 L/min. Simulations of fluid model in upper airway, FSI models with palatal Young's modulus of 7539 Pa and 3000 Pa were carried out for two cycles of respiration. The results showed that the integrated shear forces over the FSI interface were much smaller than integrated pressure forces in all the three directions (axial, coronal and sagittal). The total integrated force in sagittal direction was much smaller than that of coronal and axial directions. The soft palate was almost static during inspiration but moved towards the posterior pharyngeal wall during expiration. In conclusion, the displacement of human soft palate during respiration was mainly driven by air pressure around the surface of the soft palate with minimal contribution of shear stress of the upper airway flow. Despite inspirational negative pressure, expiratory posterior movement of soft palate could be another factor for the induction of airway collapse.
Patterns in pharyngeal airflow associated with sleep-disordered breathing
2011, Sleep Medicine
Citation Excerpt :
Our immediate question for this feasibility study was “Can pharyngeal airflow be objectively evaluated?” This proof of concept and feasibility study was designed utilizing Computed Tomography (CT) and Computational Fluid Dynamics (CFD) modeling [5–7]. CFD has been increasingly used to assess upper airway anatomy and airflow, and to explore virtual reality surgery in SDB [8–12].
To establish the feasibility of a noninvasive method to identify pharyngeal airflow characteristics in sleep-disordered breathing.
Four patients with sleep-disordered breathing who underwent surgery or used positive airway pressure devices and four normal healthy controls were studied. Three-dimensional CT imaging and computational fluid dynamics modeling with standard steady-state numerical formulation were used to characterize pharyngeal airflow behavior in normals and pre-and post-treatment in patients. Dynamic flow simulations using an unsteady approach were performed in one patient.
The pre-treatment pharyngeal airway below the minimum cross-sectional area obstruction site showed airflow separation. This generated recirculation airflow regions and enhanced turbulence zones where vortices developed. This interaction induced large fluctuations in airflow variables and increased aerodynamic forces acting on the pharyngeal wall. At post-treatment, for the same volumetric flow rate, airflow field instabilities vanished and airflow characteristics improved. Mean maximum airflow velocity during inspiration reduced from 18.3 ± 5.7 m/s pre-treatment to 6.3 ± 4.5 m/s post-treatment (P = 0.002), leading to a reduction in maximum wall shear stress from 4.8 ± 1.7 Pa pre-treatment to 0.9 ± 1.0 Pa post-treatment (P = 0.01). The airway resistance improved from 4.3 ± 1.4 Pa/L/min at pre-treatment to 0.7 ± 0.7 Pa/L/min at post-treatment (P = 0.004). Post-treatment airflow characteristics were not different from normal controls (all P ⩾ 0.39).
This study demonstrates that pharyngeal airflow variables may be derived from CT imaging and computational fluid dynamics modeling, resulting in high quality visualizations of airflow characteristics of axial velocity, static pressure, and wall shear stress in sleep-disordered breathing.
Pre-operative ultrasound prediction of difficult airway management in adult patients: A systematic review of clinical evidence
2023, European Journal of Anaesthesiology
Correlation analysis of upper airway morphology in patients with obstructive sleep apnea and anatomically small retruded mandibles
2023, Cranio - Journal of Craniomandibular and Sleep Practice
Retropalatal and retroglossal spaces evaluation: a CT study
2022, Egyptian Journal of Otolaryngology

View all citing articles on Scopus

View full text

Chest

Clinical InvestigationsCT in the Evaluation of the Upper Airway in Healthy Subjects and in Patients With Obstructive Sleep Apnea Syndrome

Aim

Patients and methods

Results

Conclusions

Section snippets

Subjects Studied

Results

Discussion

Chest

Chest

Chest

El síndrome de apnea del sueño

Med Clin (Barc)

Sleep apnea—pathophysiology: upper airway and control of breathing

Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea

N Engl J Med

Obstructive sleep apnea: diagnosis with ultrafast CT

Radiology

Cine CT in obstructive sleep apnea

AJR Am J Roentgenol

La tomografía computarizada de la vía aérea superior en el síndrome de apnea del sueño

Med Clin (Barc)

Computertomographie der oberen Atemwege-kann sie neue Erkenntnisse zur Ursache des obstruktiven Schlafapnoesyndroms liefern

Atemweg Lungenkrank

Computerized tomography in obstructive sleep apnea: correlation of airway size with physiology during sleep and wakefulness

Am Rev Respir Dis

Cine CT demonstration of nonfixed upper airway obstruction

AJR Am J Roentgenol

Effects of nasal airway positive pressure on upper airway size and configuration

Am Rev Respir Dis

The effect of posture on upper airway dimensions in normal subjects and in patients with the sleep apnea/hypopnea syndrome

Am Rev Respir Dis

Clinical Investigations
CT in the Evaluation of the Upper Airway in Healthy Subjects and in Patients With Obstructive Sleep Apnea Syndrome