Reactive Airways Dysfunction Syndrome and tetrafluoroethane inhalation

Reactive airways dysfunction syndrome (RADS) is usually associated with toxic fumes, irritants or smoke exposure, usually within an enclosed space resulting in higher inhalation exposure (Brooks). There has been a single case of probable RADS described after tetrafluorethane exposure with improvement with time but persistent reduction in lung function (Doshi).

Tetrafluorethane is a relatively inert gas and does not have the characteristic irritation associated with the usual causes of RADS. Heating of tetrafluorethane, which apparently did not occur with your patient, could generate irritants such as hydrogen fluoride and carbonyl halides. Tetrafluorethane has a LD50 of more than 1500 gm/m3 in rats although high dose inhalation could cause acute hallucination and hypoxia. However, these acute effects would not usually cause on going asthma.

I would be concerned that your patient could have vocal cord dysfunction (paradoxical vocal fold motion) that may have been precipitated by the volatile hydrocarbon exposure. This is based upon personal experience with a group of young women exposed to volatile organic hydrocarbons in a gymnasium who presented with stridor and shortness of breath with wheezing (Powell). Similar reports are in the literature with both systemic and respiratory complaints (Staudenmayer; Jones).

There has been a report of vitamin D therapy apparently improving RADS (Varney). It is difficult to interpret such reports as proving RADS is difficult so evaluating case reports is challenging. Nevertheless, I thought this may be of value.

In summary, I would recommend a thorough evaluation to be as confident as possible that the symptoms are due to RADS and not the result of VCD. Studies you may consider include lung volume studies by plethysmography to verify air trapping is present (increased lung volumes), diffusion capacity to exclude an interstitial process is responsible for the shortness of breath, careful review of spirometry with flow volume loops to look for inspiratory dysfunction, cardiac ultrasound to evaluate pulmonary hypertension, bronchoprovocation studies if her lung function will permit, rhinolaryngoscopy when she is symptomatic and possibly high resolution CT imaging of the chest to evaluate bronchiolitis or diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). A dynamic CT scan is also a consideration to exclude tracheomalacia if data suggests this is a possibility. I agree with minimizing systemic corticosteroids due to minimal benefit and significant side effects. Finally, if RADS is still suspected, you may want to consider vitamin D therapy, recognizing this based upon one case report. A pulmonary consultation to be certain a right heart catheterization is not needed to exclude pulmonary hypertension or bronchoscopy is also a consideration. However, there is little to offer as to specific therapy for RADS.

Brooks, Stuart M., M. A. Weiss, and I. L. Bernstein. "Reactive airways dysfunction syndrome (RADS). Persistent asthma syndrome after high level irritant exposures." Chest Journal 88.3 (1985): 376-384.

1. Varney VA, Evans J, Bansal AS. Successful treatment of reactive airways dysfunction syndrome by high-dose vitamin D. J Asthma Allergy. 2011;4:87-91. doi: 10.2147/JAA.S19107. Epub 2011 Sep 22.
2. Staudenmayer, Herman, et al. "Mass psychogenic illness: psychological predisposition and iatrogenic pseudo-vocal cord dysfunction and pseudo-reactive airways disease syndrome." Journal of Medical Toxicology 7.2 (2011): 109-117.
Jones, Timothy F., et al. "Mass psychogenic illness attributed to toxic exposure at a high school." New England Journal of Medicine 342.2 (2000): 96-100.
3. Powell, Scott A., et al. "Mass psychogenic illness presenting as acute stridor in an adolescent female cohort." Annals of Otology, Rhinology & Laryngology 116.7 (2007): 525-531.

Am J Ther. 2014 Aug 18. [Epub ahead of print]
R-134a (1,1,1,2-Tetrafluoroethane) Inhalation Induced Reactive Airways Dysfunction Syndrome.
Doshi V1, Kham N, Kulkarni S, Kapitan K, Henkle J, White P.
11Division of Pulmonary & Critical Care Medicine, Southern Illinois University School of Medicine, Springfield, IL; and 2Division of Internal Medicine, Southern Illinois University School of Medicine, Springfield, IL.
Abstract
R-134a (1,1,1,2-tetrafluoroethane) is widely used as a refrigerant and as an aerosol propellant. Inhalation of R-134a can lead to asphyxia, transient confusion, and cardiac arrhythmias. We report a case of reactive airways dysfunction syndrome secondary to R-134a inhalation. A 60-year-old nonsmoking man without a history of lung disease was exposed to an air conditioner refrigerant spill while performing repairs beneath a school bus. Afterward, he experienced worsening shortness of breath with minimal exertion, a productive cough, and wheezing. He was also hypoxic. He was admitted to the hospital for further evaluation. Spirometry showed airflow obstruction with an FEV1 1.97 L (45% predicted). His respiratory status improved with bronchodilators and oral steroids. A repeat spirometry 2 weeks later showed improvement with an FEV1 2.5 L (60% predicted). Six months after the incident, his symptoms had improved, but he was still having shortness of breath on exertion and occasional cough.

I hope this information is of help to you and your patient.

All my best.
Dennis K. Ledford, MD, FAAAAI