Anatomical Optical Coherence Tomography for Long-Term, Portable, Quantitative Endoscopy

Leigh, Matthew S.; Armstrong, J.; Paduch, Alexandre; Walsh, Jennifer H.; Hillman, David R.; Eastwood, Peter R.; Sampson, David D.

doi:10.1109/tbme.2007.913409

Cited by 36 publications

(31 citation statements)

References 14 publications

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“…For the pressuredriven model, the Reynolds number is clearly time-dependent but will have a mean value that is very close to Re = 252 for case = 0. Simulations are run for 0.1 s using a time step of 5×10 −5 s. For both cases, the data used, and assuming a 1:4 ratio of airway cross-section in the velopharynx, give a volumetric flow rates through the system of approximately 5 litres/min, rising to 7.5 litres/min for the offset case = 0.5, that fall within the regime of 'quiet breathing' during sleep [29]. We initiate motion by releasing the flexible plate from an imposed deflection of amplitude 0.25 mm (at the tip) in the shape of the second in vacuo mode.…”

Section: Resultsmentioning

confidence: 99%

Motions of a cantilevered flexible plate in viscous channel flow driven by a constant pressure drop

Tetlow

Lucey

2009

Commun. Numer. Meth. Engng.

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SUMMARYAn improved approach for studying the stability of a cantilevered flexible plate positioned within twodimensional viscous channel flow is presented in the context of human upper-airway dynamics. Previous work has used constant inlet velocity conditions. Here we model a constant pressure drop that may better reflect inspiratory effort. Positioning of the flexible plate within the channel can also be varied. The constant pressure drop is imposed for each time step by computing appropriate inlet velocities. The Navier-Stokes equations are solved using an explicit finite-element method written specifically for the channel geometry within which the fully coupled plate moves. The motion of the plate, driven by the pressure-field, is modelled using classical thin-plate mechanics with the addition of the fluid shear-stress-induced tension term. The investigation focuses on low-amplitude motions of the flexible plate (soft-palate) that, when unstable, may be the precursors to snoring and airway blockage during sleep. We show that imposing constant inlet velocity conditions generates over-predictions of energy transfer between flow and flexible plate during inhalation. Finally, we show that offsetting the flexible plate within the channel leads to a reduction in oscillation frequency and a significant change to its energy interaction with the fluid flow.

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Section: Resultsmentioning

confidence: 99%

Motions of a cantilevered flexible plate in viscous channel flow driven by a constant pressure drop

Tetlow

Lucey

2009

Commun. Numer. Meth. Engng.

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“…The airway geometry was measured with anatomical optical coherence tomography (aOCT), a minimally invasive endoscopic technique based on OCT with a near-infrared light, specifically adapted to map the anatomy of internal organs such as the airway (Armstrong et al, 2003(Armstrong et al, , 2006Leigh et al, 2008;Walsh et al, 2008). The system consisted of an optical probe placed inside a sealed, transparent catheter, with a 3 mm outer diameter.…”

Section: Measurementsmentioning

confidence: 99%

Effect of the velopharynx on intraluminal pressures in reconstructed pharynges derived from individuals with and without sleep apnea

Cisonni

Lucey

Walsh

et al. 2013

Journal of Biomechanics

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The most collapsible part of the upper airway in the majority of individuals is the velopharynx which is the segment positioned behind the soft palate. As such it is an important morphological region for consideration in elucidating the pathogenesis of obstructive sleep apnea (OSA). This study compared steady flow properties during inspiration in the pharynges of 9 male subjects with OSA and 9 body-mass index (BMI)-and age-matched control male subjects without OSA. The k-ω SST turbulence model was used to simulate the flow field in subject-specific pharyngeal geometric models reconstructed from anatomical optical coherence tomography (aOCT) data. While analysis of the geometry of reconstructed pharynges revealed narrowing at velopharyngeal level in subjects with OSA, it was not possible to clearly distinguish them from subjects without OSA on the basis of pharyngeal size and shape alone. By contrast, flow simulations demonstrated that pressure fields within the narrowed airway segments were sensitive to small differences in geometry and could lead to significantly different intraluminal pressure characteristics between subjects. The ratio between velopharyngeal and total pharyngeal pressure drops emerged as a relevant flow-based criterion by which subjects with OSA could be differentiated from those without.

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“…aOCT aOCT uses a fiber-optic probe to measure airway dimensions (13,22). The probe, passed through the working channel of a bronchoscope, emits a near-infrared light beam toward the airway wall and detects the resulting reflections.…”

Section: Lung Functionmentioning

confidence: 99%

Elastic Properties of the Central Airways in Obstructive Lung Diseases Measured Using Anatomical Optical Coherence Tomography

Williamson¹,

McLaughlin²,

Noffsinger³

et al. 2011

Am J Respir Crit Care Med

102

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Rationale: Our understanding of how airway remodeling affects regional airway elastic properties is limited due to technical difficulties in quantitatively measuring dynamic, in vivo airway dimensions. Such knowledge could help elucidate mechanisms of excessive airway narrowing. Objectives: To use anatomical optical coherence tomography (aOCT) to compare central airway elastic properties in control subjects and those with obstructive lung diseases. Methods: After bronchodilation, airway lumen area (Ai) was measured using aOCT during bronchoscopy in control subjects (n 5 10) and those with asthma (n 5 16), chronic obstructive pulmonary disease (COPD) (n 5 9), and bronchiectasis (n 5 8). Ai was measured in each of generations 0 to 5 while airway pressure was increased from 210 to 20 cm H 2 O. Airway compliance (Caw) and specific compliance (sCaw) were derived from the transpulmonary pressure (PL) versus Ai curves. Measurements and Main Results: Caw decreased progressively as airway generation increased, but sCaw did not differ appreciably across the generations. In subjects with asthma and bronchiectasis, Caw and sCaw were similar to control subjects and the PL-Ai curves were left-shifted. No significant differences were observed between control and COPD groups. Conclusions: Proximal airway elastic properties are altered in obstructive lung diseases. Although central airway compliance does not differ from control subjects in asthma, bronchiectasis, or COPD, Ai is lower in asthma and the PL-Ai relationship is left-shifted in both asthma and bronchiectasis, suggesting that airways are maximally distended at lower inflating pressures. Such changes reflect alteration in the balance between airway wall distensibility and radial traction exerted on airways by surrounding lung parenchyma favoring airway narrowing. Clinical trial registered with Australian New Zealand Clinical Trials Registry (ACTRN12607000624482).

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Anatomical Optical Coherence Tomography for Long-Term, Portable, Quantitative Endoscopy

Cited by 36 publications

References 14 publications

Motions of a cantilevered flexible plate in viscous channel flow driven by a constant pressure drop

Motions of a cantilevered flexible plate in viscous channel flow driven by a constant pressure drop

Effect of the velopharynx on intraluminal pressures in reconstructed pharynges derived from individuals with and without sleep apnea

Elastic Properties of the Central Airways in Obstructive Lung Diseases Measured Using Anatomical Optical Coherence Tomography

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