Characterization of acinar airspace involvement in asthmatic patients by using inert gas washout and hyperpolarized ³helium magnetic resonance

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• 作者：Sherif Gonem ; PhD^a ; Steven Hardy ; MPhys^b ; Niels Buhl ; PhD^b ; Ruth Hartley ; MB ; ChB^a ; Marcia Soares ; BSc^a ; Richard Kay ; PhD^c ; Rino Costanza ; PhD^d ; Per Gustafsson ; PhD^e ; Christopher E. Brightling ; PhD^a ; John Owers-Bradley ; PhD^b ; Salman Siddiqui ; PhD^a ; ^{ss338@le.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Asthma ; small airways ; acinus ; physiology
• 刊名：Journal of Allergy and Clinical Immunology
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：137
• 期：2
• 页码：417-425
• 全文大小：1044 K

文摘

The multiple-breath inert gas washout parameter acinar ventilation heterogeneity (S_acin) is thought to be a marker of acinar airway involvement but has not been validated by using quantitative imaging techniques in asthmatic patients.

Objective

We aimed to use hyperpolarized ³He diffusion magnetic resonance at multiple diffusion timescales and quantitative computed tomographic (CT) densitometry to determine the nature of acinar airway involvement in asthmatic patients.

Methods

Thirty-seven patients with asthma and 17 age-matched healthy control subjects underwent spirometry, body plethysmography, multiple-breath inert gas washout (with the tracer gas sulfur hexafluoride), and hyperpolarized ³He diffusion magnetic resonance. A subset of asthmatic patients (n = 27) underwent quantitative CT densitometry.

Results

Ninety-four percent (16/17) of patients with an increased S_acin had Global Initiative for Asthma treatment step 4 to 5 asthma, and 13 of 17 had refractory disease. The apparent diffusion coefficient (ADC) of ³He at 1 second was significantly higher in patients with S_acin-high asthma compared with that in healthy control subjects (0.024 vs 0.017, P < .05). S_acin correlated strongly with ADCs at 1 second (R = 0.65, P < .001) but weakly with ADCs at 13 ms (R = 0.38, P < .05). ADCs at both 13 ms and 1 second correlated strongly with the mean lung density expiratory/inspiratory ratio, a CT marker of expiratory air trapping (R = 0.77, P < .0001 for ADCs at 13 ms; R = 0.72, P < .001 for ADCs at 1 second).

Conclusion

S_acin is associated with alterations in long-range diffusion within the acinar airways and gas trapping. The precise anatomic nature and mechanistic role in patients with severe asthma requires further evaluation.