• Get the demographics right. These include age, height, sex and race. Often the junior doctor will not accurately record height, however this is one of the most important parameters to assess the patient’s normal range of lung volumes
• Explanation to the patient. It is always important to explain to the patient the test and why it is being performed
• Positioning: ensure the patient is sitting upright with abdomen lengthened and chest expanded either sitting in a chair or at the least with their legs hanging over the side of the bed with their feet touching the ground
• Coaching:Explain to the patient the technique i.e. “Take a big breath in, put your lips around the tube, blow out as hard and fast and continue until you have no breath left”. You may like to demonstrate the technique to the patient first to clarify the technique. It is important to encourage the patient to blow as hard as they can for as long as possible. Encourage them to continue blowing whilst they are expiring so they give their maximum effort
• Reproducibility: There needs to be at least 3 reproducible results. If the patient continues to get better, repeat the test until there are three reproducible results. Reproducibility to ensure they have given their maximum effort is crucial to the accuracy of the results

• Spirometric ratio – FEV1/FVC – < 0.7 is indicative of obstruction. > 0.7 can be either a normal or restrictive pattern
  • NB: a patient may have a high ratio if they have not completed full expiration
  • NB: Ensure you record the absolute ratio (not the ‘percent predicted’ of the ratio)
• FEV1 – will give an indication of the severity of disease. As FEV1 decreases severity increases In the context of spirometric ratio < 0.7:
  • FEV1 >80% – mild COPD
  • FEV1 < 50% is considered severe disease
• FVC – a decrease in both FEV1 and FVC may indicate restrictive lung disease and would need to be confirmed with formal lung volume testing in the lung function lab
• Always look at both the absolute volume in litres, as well as the percentage of predicted (and ensure that you put both of these numbers in the patient’s notes when recording the result).
  • Eg: Spirometry: FEV1 2.4L (51%), FVC 4.2L (70%), FEV1/FVC = 0.57

• After the initial testing, with 3 reproducible results, give the patient 4 puffs of salbutamol via spacer, allow 5 minutes to take effect, and then perform the test again
• If the FEV1/FVC increases by 200mls and 12% then this is a significant reversible obstruction and suggests that there may be asthmatic component
• If there is no significant reversible component, it is important not to assume that bronchodilators are no longer effective in this patient, they should continue their bronchodilator in this setting

• Flow volume loops have two measurements
  • Flow (In Litres/second) – y axis
  • Volume (In Litres) – x axis

Flow volume loops gives us an indication of the generation of flow through the respiration cycle. The patterns of the flow volume loop can be indicative of certain respiratory conditions as demonstrated in the diagram below.

• To investigate a restrictive lung picture
• In patients with difficulties with compliance to testing. The technicians are skilled in ensuring a patient is fully compliant and that the most accurate result is achieved
• Lung Volumes done by body plethosmography allow us to measure lung volumes and gas exchange.

This allows us to make inferences into their respiratory disease. It may demonstrate a problem with diffusion such as in emphysema or pulmonary fibrosis that may impair gas exchange

• In this case the anesthetist is able to implement interventions if appropriate
• In the case of severe COPD where a patient is below their baseline, this may mean a delay in the surgery to ensure their lung function is as best as it can be before theatre, by administering medications such as steroids and bronchodilators prior to surgery to optimise function
• Knowing the results of a patient’s spirometry also allows the anesthetist to risk stratify their choice of anesthetic, in this case of abdominal surgery, if the patient has severe COPD a spinal may be more appropriate to mitigate the risk of needing an intubation for this patient

• Identify patients which are likely to need spirometry
• Interpret the results accurately
• Communicate these results concisely to the relevant team both written and verbal

• A chest x-ray will rule out if the patient has concomitant pneumonia
• If the chest x-ray shows consolidation then the patient has pneumonia, which will require different management than purely an exacerbation of COPD

• Document in the notes and discharge summary the patients baseline spirometry as it allows us to refer to this to assess if the patient is below baseline for future admissions
• Almost all patients with an acute respiratory disorder will require Spirometry to adequately assess how unwell they are compared to their baseline
• Spirometry is an effort dependent test. The patient is required to their best effort to ensure an accurate results

• http://www.frca.co.uk/images/flow_volume.gif