Reactive airway dysfunction syndrome: Are we missing these patients?

Introduction

The term reactive airway dysfunction syndrome (RADS) was first used by Brooks et al. to describe asthma-like illnesses in patients developing after single exposure to high level of irritating aerosols.¹ Diagnostic criteria given by the American College of Chest Physicians (ACCP)² include

• 1.Absence of preexisting respiratory illness, asthma or asthma mimic.
• 2.Onset of asthma after a single accident/exposure to irritant gases, vapour, fume or smoke in very high concentration.
• 3.Onset of symptoms within 24 h of exposure.
• 4.Positive test for bronchial hyperreactivity.
• 5.Airflow obstruction may or may not be present.
• 6.Exclusion of any other disorder explaining the symptom and finding.

Given the lack of knowledge about RADS and similarity of symptoms with a much more common illness (asthma), these patients are often recognised retrospectively and after a considerable delay.³ Exposure to airway irritants in the military environment is not uncommon. Smoke inhalation and hydrogen fluoride and various other airway irritant exposures are reported in the literature.4, 5 We report a case of RADS in a Navy diver after closed space smoke inhalation during an accidental fire onboard.

Case report

A 31-year-old Navy diver male patient was referred for recurrent episodes of cough and breathlessness after exposure to smoke during a fire accident onboard. He had no prior history of episodic cough, breathlessness or wheeze. There was no prior history of seasonal cough, cold going to chest or allergies. There was no history of bronchial asthma in family. He was a non-smoker with no significant history of exposure to environmental tobacco smoke. Being a diver, he was undergoing regular medical examination including spirometry, electrocardiogram (ECG) and chest radiograph. All his tests before the accident were normal, as is essential to continue with diving duties. He was exposed to fire in a closed compartment for approximately 30 min during the accident. Immediately after the exposure, he developed cough and breathlessness and was nebulised with bronchodilators at the primary care setting. After this, he continued to have episodes of cough and breathlessness, especially on exposure to irritants such as smoke, diesel fumes or cold air-conditioned environment. He also had an episode of feeling tightness in the chest and feeling asphyxiated during a diving assignment requiring early termination of diving. On reporting to our centre, almost 9 months after the accident, he was comfortable at rest. His general physical examination at rest was within normal limits with a pulse rate of 84/min, blood pressure of 128/82 mm Hg and respiratory rate of 18/min. His chest examination revealed bilateral end expiratory wheeze on forced expiration. Evaluation revealed normal haemoglobin, total leucocyte count, differential leucocyte count, renal function and liver function. ECG, 2D Echo, chest radiograph, arterial blood gas analysis and high-resolution computerised tomography were all normal. He underwent spirometry that revealed moderate obstruction (FEV1%: 60.5%, FEV1: 1.83L [51% predicted], FVC: 3.02L [80% predicted]). His lung volumes and diffusion capacity of carbon monoxide were normal. The test for bronchial hyperreactivity was not performed in favour of patient safety as the patient already had moderate obstruction on spirometry. He was diagnosed as having RADS as he fulfilled all the ACCP diagnostic criteria for diagnosis of RADS. He was immediately taken off all diving duties and was started on inhaled steroids and bronchodilators. He is asymptomatic on medication and is under regular follow-up.

Discussion

The peculiarities of the Naval warfare predispose the seafarers to peculiar pulmonary injuries. Constrained living spaces, compartmentalisation, electric equipment, lack of proper ventilation and armaments onboard predispose the Ship to the worst enemy of the seafarer—fire. Any fire on a ship exposes the sailors to burn injuries due to fire and also closed-space smoke inhalation injuries (SIIs). These exposures can have immediate as well as long-term consequences.

Despite its description by Brooks et al. in 1985,¹ RADS still lacks clarity.³ Difficulty in estimating the incidence of this entity arises due to lack of precise information on duration and quantity of exposure⁶ and a possible lack of awareness, similarity of symptoms to asthma and lack of availability of appropriate diagnostic tools especially in the primary care setting.

Clinical presentation includes development of asthma-like symptoms within 24 h of single high-level exposure to airway irritants.⁶ The recognised causal agents include household agents (floor sealant and spray paint), industrial exposures (welding, perfumes and pesticides), chemicals (sulphuric acid and ammonia), fire and smoke inhalation, burning paint smoke etc.³ In our patient, symptoms developed after single high-level exposure to smoke within 24 h of exposure. RADS needs to be differentiated from a preexisting asthma with worsening of symptoms after irritant exposure.⁶ In our patient, a detailed history did not reveal any preexisting respiratory symptoms. Also, there was no history of asthma in family. Being a diver, prior spirometry results were available for comparison. All the results of his spirometry performed before the exposure, as a part of diving medical examination, were normal. These facts were used to exclude a preexisting asthma. An individual exposed to short-term irritants may recover completely despite the severity of initial symptoms.⁷ That will not qualify them as having RADS. In our previous report of two cases, who developed acute lung injury after closed-space smoke inhalation,⁴ both achieved complete symptomatic and radiological recovery and had a normal spirometry after treatment. In RADS, however, persistent symptoms after exposure are required for diagnosis.⁶ These patients develop non-specific bronchial hyperreactivity resulting in bronchospasm in response to various environmental stimuli.⁶ Our patient also had persistent symptoms for 9 months after exposure and also had history of worsening of symptoms on exposure to various environmental allergens.

Although the pathological changes and their temporal evolution is not fully defined, various authors have described mucous gland hyperplasia with mild inflammatory response⁷ and airway inflammation with basement membrane thickening and subepithelial fibrosis.⁸ It is postulated that massive epithelial damage leads to activation of neurogenic inflammation and release of proinflammatory cytokines by activated mast cell and macrophages with recruitment of inflammatory cells.⁶

The patients with RADS are treated as patients with asthma as no significant advances have been made in the management of this condition.⁶ Corticosteroids⁹ and high-dose vitamin D³ have been used. We managed our patient with inhaled steroids and bronchodilators with significant symptomatic relief. The recognition of RADS and discontinuation of diving duties will definitely help in avoiding a life-threatening diving accident in these patients.

These patients can easily be missed and continue to be treated as asthmatic patients which affects the true assessment of prevalence of RADS. Owing to obvious reasons, prevalence of RADS is likely to be more in the military environment than other occupations. Also, correct recognition will also help in correct assessment of disability for these patients. It is suggested that all those involved in fire accidents be encouraged to get themselves evaluated at the nearest military hospital at the earliest. If suspicion of RADS is there, these patients can be referred to a respiratory centre for further evaluation. These patients will be unfit for diving duties and posting to high altitude areas. In our patient, the asphyxiation episode he had during diving could have proved fatal. These accidents can be avoided by early and proper diagnosis of these patients.

Conclusion

RADS is a distinct possibility, especially in the high-risk military environment. The living conditions predispose the Naval sailors to these risks much more than other fighting arms. Awareness of this condition and appropriate intervention at correct time can prevent life-threatening accidents.

Conflicts of interest

The authors have none to declare.