Testing Procedure (RVC)

You will need to explain that there will be two different blows performed for this procedure; the relaxed manoeuvre and the forced manoeuvre.

Firstly, of course you must ensure you have the correct patient.


Date of birth


Hospital number

  • Gain verbal consent
  • Appropriate hand washing procedures
  • Measure the patient’s height and weight
  • Height must be measured without shoes. If unable to measure height use arm span instead
  • Enter date of birth or age, gender, ethnicity, height and weight into the spirometer
  • Ethnicity – this should be entered as per spirometer manufacturer’s instructions
  • Ask patient about any pre-test instructions and contraindications
  • Check that the correct date and time are shown
  • Prepare the patient and the equipment to perform the baseline RVC followed by the baseline FVC
  • Ensure the patient is sitting UPRIGHT and is not slouching – this will reduce lung volumes
  • Ensure their shoulders are relaxed – to ensure the lungs can inflate optimally within the thorax
  • Apply nose clip (especially for RVC manoeuvres)
  • Achieve x3 accurate and repeatable RVC manoeuvres
  • Achieve x3 accurate and repeatable FVC manoeuvres
  • Record baseline spirometry results in electronic or paper template, using the largest FEV1 and RVC or FVC (performed to standard) to determine the
  • FEV1/RVC and FEV1/FVC ratios
  • If the patient is unable to perform either manoeuvre acceptably, record why this is not possible and refer for a specialist assessment if necessary
  • Appropriate hand washing procedures

Explain and demonstrate the procedure to the patient so that they understand what is required of them, and why it is important to perform each manoeuvre as best they can.

You will need to explain that there will be two different blows performed for this procedure; the RVC manoeuvre and the FVC manoeuvre. They will need to perform each type of blow on several occasions.

The following video illustrates how to perform a ‘Relaxed’ Vital Capacity (RVC). There are three main reasons for performing a RVC before a FVC manoevure:

The RVC is expected to be greater than the FVC as intra-thoracic pressure (which compresses the airways) is less with the former technique.

This sets the benchmark for the FVC manoeuvre and adds another assessment of airways patency (the FEV1/RVC ratio)
It is an easier test to perform which prepares the patient for the more physically demanding FVC manoeuvre.

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