Jump to comment:

• FEV1/PEF ratio: The forgotten measure of upper airway obstruction
  Daniel K C Lee
  Published on: 9 January 2022

• Published on: 9 January 2022

  FEV1/PEF ratio: The forgotten measure of upper airway obstruction

  • Daniel K C Lee, Prashant S Borade, Nicholas J Innes

  Dear Editor,

  Several measures exist to aid the diagnosis of upper airway obstruction (UAO). These include subjective clinical signs such as the presence of stridor and objective measures such as the pattern of the flow-volume curve. However, by far the simplest and easily measured, but yet relatively unknown and underutilised, is the forced expiratory volume in 1 second (FEV₁) / peak expiratory flow (PEF) rat...

  Show More

  Dear Editor,

  Several measures exist to aid the diagnosis of upper airway obstruction (UAO). These include subjective clinical signs such as the presence of stridor and objective measures such as the pattern of the flow-volume curve. However, by far the simplest and easily measured, but yet relatively unknown and underutilised, is the forced expiratory volume in 1 second (FEV₁) / peak expiratory flow (PEF) ratio. We wish to reignite attention to the use of this uncomplicated measurement through presentation of an interesting clinical case.

  A 57-year old lady presented to our respiratory clinic with a complaint of inspiratory stridor. She did not have any other significant respiratory symptoms. There were no overt symptoms of gastroesophageal reflux or oesophageal dysfunction. On direct questioning, she denied any symptoms consistent with collagen vascular disease or vasculitis, except Raynaud’s phenomenon. Her medications included losartan for hypertension and amitriptyline for depression. She is a never-smoker. Clinical examination was unremarkable apart from a soft inspiratory stridor, which was heard best above the suprasternal notch. Her blood biochemistry, haematology, autoimmune, and vasculitic screen were unremarkable. Spirometry showed FEV₁ of 2.79L (110% predicted), forced vital capacity (FVC) of 3.57L (120% predicted), FEV₁/FVC ratio of 78%, and PEF of 396L/min (105% predicted). Her calculated FEV₁/PEF ratio was 7.05ml/L/min. The pattern of the expiratory flow-volume curve was normal with a slight plateau in the inspiratory flow-volume curve (Figure 1). Flexible fibre-optic bronchoscopy demonstrated a subglottic stenosis (Figure 2).

  Several pioneering studies have previously determined the usefulness of the FEV₁/PEF ratio in diagnosing UAO.^1-3 FEV₁ is defined as the volume measured during the initial 1 second of a forced expiration from full inspiration and PEF is defined as the maximum flow rate maintained for at least 10 milliseconds during a forced expiration from full inspiration. Therefore, in UAO where the embarrassment is in the pre-carina upper airway, one would intuitively expect the FEV₁/PEF ratio to increase, as chronologically, PEF would be affected more than FEV₁, with the former reflecting more proximal airway per se. Evidently, the FEV₁/PEF ratio has been shown to be significantly higher in patients with UAO compared to patients with asthma, chronic obstructive pulmonary disease, and normal subjects.^1;2 A value of above 10ml/L/min was initially thought to represent UAO,^1;2 although this was subsequently found to vary between 7ml/L/min and 12ml/L/min depending on the different subgroups of UAO such as extrathoracic, fixed, and variable intrathoracic.³

  Therefore, although definitive procedures such as flexible fibre-optic bronchoscopy are needed to confirm the diagnosis of UAO, straightforward practical measurements that are useful in day-to-day clinical practice such as the FEV₁/PEF ratio, which is easily obtainable through simple spirometry, may aid in either prompting initial consideration or confirming clinical suspicion of such a diagnosis.

  Daniel K C Lee, MB, BCh, MRCP, MD
  Prashant S Borade, MB, BS, MD
  Nicholas J Innes, MB, BS, FRCP
  Department of Respiratory Medicine, Ipswich Hospital, Heath Road, Ipswich IP4 5PD, Suffolk, England, United Kingdom

  References

  1. Empey DW. Assessment of upper airways obstruction. BMJ 1972; 3: 503-505.
  2. Rotman HH, Liss HP, Weg JG. Diagnosis of upper airway obstruction by pulmonary function testing. Chest 1975; 68: 796-799.
  3. Mellisant CF, Van Noord JA, Van de Woestijne KP, Demedts M. Comparison of dynamic lung function indices during forced and quiet breathing in upper airway obstruction, asthma, and emphysema. Chest 1990; 98: 77-83.

  Figure 1
  Expiratory and inspiratory flow-volume curve

  

  Figure 2
  Subglottic stenosis found on flexible fibre-optic bronchoscopy

  

  Show Less

  Conflict of Interest:
  None declared.

  • Back to top