Background: respiratory physicians are often asked to assess subjects charged with failure to provide evidential breath specimens for alcohol analysis in police stations. In the UK two 3-minute cycles are allowed to produce two specimens, each requiring a continuous even blow of around 6-12 seconds in duration. Spirometry is useful both diagnostically and in the assessment of technique required to perform this respiratory manoeuvre. FeNO testing has not been described in the medicolegal literature, but the technique needed to perform this test is the most similar to evidential breath testing.

Methods: we describe 91 consecutive individuals who underwent FeNO testing with a NIOX VERO meter in our clinic in the evaluation of failure to provide evidential breath specimens. Subjects were allowed up to 10 attempts. All subjects underwent clinical assessment and spirometry testing.

Results: 82/91 (90%) subjects succesfully provided a FeNO sample. 9/91 (10%) were unable to do FeNO due to suboptimal technique. According to NICE criteria 10/91 (11%) subjects had high readings ?40ppb, 12/91 equivocal 25-39ppb and 69/91 (76%) normal <25. Asthma was newly diagnosed in 3/22 (14%) subjects with high or equivocal readings.  

Conclusion: FeNO testing is a useful tool in the evaluation of failure to provide breath alcohol cases, for the diagnosis of asthma, assessment of asthma control, and also the ability to perform a similar respiratory manoeuvre to evidential breathalyser testing.