Is ventilation heterogeneity related to asthma control?

Svenningsen, Sarah; Nair, Parameswaran; Guo, Fumin; McCormack, David G.; Párraga, Grace

doi:10.1183/13993003.00393-2016

Cited by 63 publications

(58 citation statements)

References 37 publications

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“…If these lung regions were mechanistically responsible for asthma symptoms, then one could postulate that the key to treating difficult-to-control asthma lies within these areas. Hence, this lends significance to the associations between ventilation defects and asthma control reported by SVENNINGSEN et al [2], given that they studied patients with quite severe asthma who were relatively young (mean age 46 years) who were highly symptomatic, with high Asthma Control Questionnaire (ACQ) scores, had a range of airflow obstruction (forced expiratory volume in 1 s/forced vital capacity ratio down to 0.33) and nearly half were oral corticosteroid dependent.…”

Section: @Erspublicationsmentioning

confidence: 72%

“…reduced ventilation due to airway narrowing per se [15]. Perhaps this because researchers' attentions have been drawn to the visually dramatic nature of ventilation defects, which again have been elegantly demonstrated using hyperpolarised 3 He MRI by SVENNINGSEN et al [2] in this issue of the European Respiratory Journal. It is uncertain what causes these defects but the fact that they tend to persist over time [16] and can be induced acutely by bronchoconstriction [3,4,14], which is also repeatable between sessions [14], suggests a structural basis to their presence, rather than being due simply to mucus plugging.…”

Section: @Erspublicationsmentioning

confidence: 99%

“…Tomographic imaging methods include hyperpolarised noble gas magnetic resonance imaging (MRI) (e.g. helium-3 or xenon) [2], positron emission tomography [3], single photon emission computed tomography (CT) [4,5] and oxygen enhanced MRI [6], where the distribution of a tracer gas is imaged. Inert-gas washout tests are based on the simple principle that regions of the lung that ventilate poorly or not at all (i.e.…”

Section: @Erspublicationsmentioning

confidence: 99%

“…An important question raised by the observations of SVENNINGSEN et al [2] is whether ventilation defects could directly contribute to asthma symptoms? The ACQ is based on retrospective recall of symptoms from the previous week, which could conceivably be attributed to spontaneous airway narrowing and closure.…”

Section: @Erspublicationsmentioning

confidence: 99%

“…If it is due to tissue remodelling, this would explain a lack of corticosteroid responsiveness but how could this be treated? MBNW indices specific to acinar and conductive airway function may be more sensitive to regional ventilation defects than the LCI used in the SVENNINGSEN et al [2], and should ideally be used in future studies. Are there more practical ways than sophisticated and expensive ventilation imaging can be justified in proof-of-concept studies, more practical methods will be needed in later stage studies, for example, washout tests and oscillatory impedance techniques could be considered.…”

Section: @Erspublicationsmentioning

confidence: 99%

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Complex lung function in severe asthma: seeing is believing

King

Thamrin

2016

Eur Respir J

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@ERSpublicationsTechniques to partition airway dysfunction could improve understanding of severe asthma http://ow.ly/N7zD301wFn6Difficult-to-treat or severe asthma remains a common problem and a challenge for healthcare providers. It affects up to 10% of asthmatic individuals, who continue to suffer high disease burden and healthcare costs [1]. This clinical problem still exists despite many advances in the understanding of the underlying basis of asthma and improved management strategies, which include targeted anti-inflammatory therapy with monoclonal antibodies. Research effort continues, with exploration of different aspects of pathophysiology such as genomics, proteomics, inflammation, airway remodelling and airway smooth muscle abnormalities. In this context, the examination of complex lung function at the whole-organ level becomes increasingly important. There have been many technical advances in functional imaging and in complex measures of lung function that can now be used to explore the pathophysiology of asthma at the whole-organ level, and which can be more directly related to clinical manifestations of disease such as symptoms and airway hyperresponsiveness.Measuring patterns of ventilation (ventilation distribution) is a way to characterise lung function that is highly relevant in obstructive lung diseases, and goes far beyond spirometry, peak flow and lung volumes. Ventilation distribution can be quantified visually using three-dimensional (tomographic) ventilation imaging techniques as well as functionally using inert-gas washout tests. Tomographic imaging methods include hyperpolarised noble gas magnetic resonance imaging (MRI) (e.g. helium-3 or xenon) [2], positron emission tomography [3], single photon emission computed tomography (CT) [4,5] and oxygen enhanced MRI [6], where the distribution of a tracer gas is imaged. Inert-gas washout tests are based on the simple principle that regions of the lung that ventilate poorly or not at all (i.e. altered distribution) delay the clearance (i.e. washout) of a marker gas from the lung during normal tidal breathing. Thus, 100% oxygen can be used to "wash out" the resident nitrogen over multiple breaths, which is the basis of the multiple-breath nitrogen washout (MBNW). Similarly, if low concentrations of inert gases such as sulfur hexafluoride or helium are introduced into the lung, then their pattern of clearance from the lung reflects ventilation distribution.Ventilation imaging and inert-gas washout tests are thus two different yet complementary methods for characterising ventilation distribution. Ventilation imaging shows where functional abnormalities occur, how extensive they are and how they are colocated. Conversely, inert-gas washout measures ventilation that has been averaged across the entire lung but probes much finer length scales than those afforded by the resolution of modern imaging techniques. Ventilation distribution measured from inert-gas washouts is determined by the small airways; studies in smokers [7] and bone marrow transplant...

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Section: @Erspublicationsmentioning

confidence: 72%