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P213 Falling flat: a comparison of inspiratory flow volume loops in patients with inducible laryngeal obstruction and asthma
  1. C Slinger1,
  2. H Wilson1,
  3. A Vyas1,
  4. R Slinger2
  1. 1Lancashire Teaching Hospitals NHS Trust, Preston, UK
  2. 2Lancaster University, Lancaster, UK

Abstract

Introduction The differential diagnosis of refractory breathlessness can be challenging, involving a systematic assessment of potential causes and aggravating co-morbidities. The index of suspicion for referral for specialist assessment of conditions such as Inducible Laryngeal Obstruction (Ilo) may be heightened using available clinical assessment tools, for example, the Inspiratory arm of the flow volume loop (FVL). Sterner (2009) found Ilo to be the most common diagnosis in patients with a consistently abnormal inspiratory loop. Morris & Christopher (2013) found 52% of patients with Ilo had flattened inspiratory loop. The current gold standard for objectively assessing for Ilo is Laryngoscopy.

Aims and objectives To investigate the presence of an abnormal inspiratory FVL in a sample of patients with symptoms of breathlessness, and to analyse whether this is a predictor of specific causes of breathlessness.

Methods Patient notes and FVL results were reviewed according to characteristic abnormalities of the inspiratory curve (flattened, absent and truncated) for people referred to a tertiary airways service for symptoms of breathlessness over a 22 month period. Assessment information was collated for patients (n=324) diagnosed with asthma, Ilo or both. Patient demographics and detailed assessment information were compared across these groups to look for potential patterns and predictors.

Results 59% of patients with Ilo (with or without asthma) had an abnormal inspiratory FVL, compared to 42% of patients without Ilo. For patients with Ilo as their sole diagnosis, 62% had an abnormal FVL. A chi-square analysis showed that an abnormal inspiratory FVL was significantly more common in patients with a diagnosis of Ilo (χ2= 4.47; p≤0.05) compared to patients without.

A binary logistic regression assessed the relationship between an abnormal inspiratory FVL and Ilo diagnosis. The model was significant (χ 2 =5.1 (1, N=324) p=0.02) indicating that FVL was a significant predictor of Ilo, and odds ratios suggested that patients with Ilo were twice as likely to have an abnormal loop.

Conclusions In patients with breathlessness symptoms that are refractory to optimal medical treatment, observation of the FVL may indicate the potential for further specialist assessment for Ilo with provocation videolaryngoscopy.

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