Abnormal Spirometry Medical Risk in Aviation Conference Royal Aeronautical Society, Dec 2017 Professor Howard Branley MBChB MSc MD FCCP FRCP FRAeS Consultant in Respiratory Medicine
What I want to cover What is spirometry? Why do spirometry? Asthma & its natural history Aeromedical concerns with asthma Assessment of asthma control Asthma treatment: (non)-pharmacological Asthma in aviators
What is Spirometry Measurement of expiratory volumes from TLC down to RV FEV1 and F(VC) FER = forced expiratory ratio = FEV1 / (F)VC = normally > 70%
Why do Spirometry? FER < 70% defines airflow obstruction/limitation In aviation, mainly due to - asthma (commonly) - COPD (less commonly) Asthma - airflow limitation is VARIABLE - may have normal FER, which can become rapidly abnormal
What is asthma? Asthma is a chronic inflammatory condition. Characterised by: - Reversible airways obstruction Bronchial hyperresponsiveness (BHR)
Natural history of childhood asthma 70% experience symptomatic asthma in adulthood Of the other 30% (asymptomatic), 60% have BHR i.e. an asthmatic tendency Hopkirk JA 1984 Aviat Space Environ Med 1984,55(5):419-421
Asthma: Aeromedical concerns Incapacitation from bronchospasm/hypoxaemia: - cold air - dry air - exposures (smoke, fumes) - decompression & pneumothorax - URTI/LRTI - stress Incapacitation may be sudden or subtle.
Management of Asthma in Aviation Assessment of asthma control Be alert for adverse drug reactions Regulatory requirements vs. Clinical requirements
CAA, Spirometry & Asthma (1) Spirometry is required for: - Initial class 1 Class 1 on clinical indication Class 2 on clinical indication FER < 70% - needs evaluation by Cons Resp Med
CAA, Spirometry & Asthma (2) Initial class 1 h/o asthma - CAA Cons in Resp Med Existing class 1 new asthma - CAA Cons in Resp Med Existing class 1 established asthma & stable - local Cons in Resp Med (exercise spiro & details of Rx) Initial class 2 - local Cons in Resp Med (exercise spiro & details of Rx)
CAA, Spirometry & Asthma (3) May be disqualifying H/o asthma attacks requiring Rx/TCI - 5 years class 1-2 years class 2 Repeated OCS / frequent exacerbations
Assessment of asthma control (1) Aim No asthma adverse history & minimal Rx (ICS < 800mcg BDP equivalent) Adverse Hx High levels Rx including OCS, theophylline, MTX etc Recurrent symptoms (cough, wheeze, SOB etc) Recurrent exacerbations Nocturnal wakening indicates poor control & impacts on sleep quality with potential for fatigue & reduced performance
Assessment of asthma control (2) Lung Physiology Spirometry FEV 1 /FVC ratio (normal > 70%) Bronchial reactivity (6 minute free running). Measure FEV 1 : (i) at baseline; (ii) at end of exercise; and (iii) 10 mins postexercise. Control relative to FEV1 drop Well (< 10%) Moderate (11-16%) Suboptimal (16-20%) Poor (> 20%)
Bronchial Reactivity Testing Exercise (6 mins) vs Chemical Challenge Exercise: free run or treadmill? Chemical Challenge: direct or indirect?
Exercise (6 min run) Running is most asthmagenic form of exercise Drop in PEFR with exercise - free run 47% - treadmill 33% - bicycle 25% - swimming/walking 13-15%
Free run vs Treadmill Free run Treadmill Outside Regulate speed Adverse weather Indoors Reproducibility? Can monitor HR/BP/rhythm
Chemical Challenge Direct Indirect Histamine, methacholine Mannitol Direct bronchoconstriction 20% drop in FEV1 Increase osmolarity of airway surface causes mast cell mediator release 15% drop in FEV1
Bronchial Reactivity Test Form To be completed by an accredited specialist in Respiratory Medicine and returned to AME (for Class 2) or CAA AMS* (for Class 1). Please see UK CAA asthma certification guidance for further information. Fees incurred in providing reports are the responsibility of the applicant and not the CAA. CAA Reference Number: Name: DOB: Reason for Request: Abnormal lung function: Class 1: FEV 1 /FVC <70% History of asthma: Class 2: Peak flow <80% predicted Other Current or past diagnosis of asthma (within 5 yrs Class 1 or 2 yrs for Class 2) needing regular (> once per 3 months) use of any inhaler Other clinical reason:.. List of current medication taken........ Contraindications for Exercise Spirometry: YES Active illness (e.g. URTI, fever, current treatment for cold, etc.) Cardiovascular abnormalities (e.g. suspicious history, abnormal findings during examination incl ECG, etc) Other:... NO UK CAA Bronchial Reactivity Test Form 1 of 2 September 2012 v1.0
Bronchial Reactivity Test (6 minute free running test): (A) Resting FEV 1 (ml)... (B) Immediate post-exercise FEV 1... (ml) =... % fall [(A-B)/A] (C) 10 minutes post-exercise FEV 1... (ml) =... % fall [(A-C)/A] Please tick ONE: 10% FEV 1 fall 11-15% FEV 1 fall 16-20% FEV 1 fall > 20% FEV 1 fall If further investigations/information/discussion required, please specify: If any follow-up requirements, please specify: Test conclusions: Any additional comments: Name (Print):... GMC No:... Signature:... Date of Signing:... Please send the completed form to AME for Class 2 or AMS for Class 1: Authority Medical Section Medical Department CAA Gatwick Airport South West Sussex RH6 0YR UK CAA Bronchial Reactivity Test Form 2 of 2 September 2012 v1.0
Outcomes post BRT Class 1/2 Certification: Criteria Well-controlled asthma: No adverse history, satisfactory spirometry, fall in FEV 1 of less than or equal to 10% on Bronchial Reactivity Test, inhaled corticosteroids less than 800µg day Moderately controlled asthma: No adverse history, satisfactory spirometry, fall in FEV 1 of 11-16% on Bronchial Reactivity Test, or inhaled corticosteroids equal to or greater than 800µg day Sub-optimally controlled asthma: No adverse history, satisfactory spirometry, fall in FEV 1 of 16-20% on Bronchial Reactivity Test Uncontrolled asthma: Fall in FEV 1 of greater than 20% on Bronchial Reactivity Test AND/OR adverse history Certification Unrestricted Class 1 Unrestricted Class 2 Class 1 OML Unrestricted Class 2 Class 2 OSL Unfit all Classes
Non-pharmacological measures Allergen avoidance (e.g. HDM) Smoking cessation Weight reduction if appropriate
Pharmacological measures SABA ICS < 800mcg BDP equivalent LABA Cromoglycate (not really used in adults) NOT High dose ICS (>800mcg) OCS Theophyllines Disease-modifying Rx e.g. MTX
UK CAA Incapacitation Study Review of all incapacitations in 2004 16145 Class 1 holders in 2004 720 pilot episodes of TU (4.5%) 36 incapacitations (0.2%) - 2 PE - 4 pneumothorax - nil asthma Evans S et al Aviat Space Environ Med. 2012 Jan;83(1):42-49
Prevalence of asthma in military 14% asymptomatic military personnel (US Army) have airflow obstruction 23% of the above have worsening BHR on exercise Morris MJ et al Mil Med. 2007 Nov;172(11):1194-7
Outcome of asthma in Israeli Air Force 19 asthmatic pilots 1988-2005 No sudden incapacitation or safety breaches from asthma 2 were grounded (1y and 23y after diagnosis) Carter D et al Aviat Space Environ Med. 2006 Aug;77(8):838-41.
Thank you hbranley@gmail.com 020 3773 5399