Measurement Procedure

  • Sit upright (with good posture) or stand comfortably. If possible, look away from the computer screen so you cannot view the data as it’s being collected (so you won’t subconsciously alter your breathing pattern).
  • Hold the Spirometer in an upright position.
  • Place the flow head’s mouthpiece in your mouth, between the teeth, and make a good seal with your lips. Keep your tongue flat so it doesn’t obscure the opening.

Note: You may find biting the flow head is a good way to hold it in position.

  • If required, attach the nose clip or hold your nose to ensure that all breathing is done through the mouth. (This is necessary if the results need to be qualitative, but is not normally required for breathing pattern studies). 
  • Make time to adapt to breathing into the flow head and practice any procedures you need to follow. You may find it easier to be talked through each part of the routine or to follow a card of instructions. 
  • Breathe quietly in order to become accustomed to the apparatus and attain a stable breathing pattern. Air expired from the lungs is measured as positive flow, inspired air as negative.
  • Rest the Spirometer on the work surface between uses to prevent the heat of your hand affecting the results. 

Note: Don’t expect perfect results first time. The Spirometer is an unnatural breathing device and time is required to learn how to breathe naturally through it.

Health and Safety considerations

    • The flow heads are capable of trapping sub-micron sized microbes. They have cross contamination efficiency for both bacteria and virus of 99.9% @ 55L/min and 750L/min.
  • Each student should use their own flow head. There is a possibility that infective agents trapped in the filter can become freed during inhalation and breathed back into the test subject’s system. This represents a point of possible cross contamination. It is not sufficient to simply wipe the mouth piece of the flow head with an antiseptic wipe and pass the apparatus on to the next subject. This only cleanses the area in contact with the mouth, it does not disinfect the filter or the internal surfaces of the flow head.
  • The ‘fixed’ flow head will not need to be changed with each use as long as the outlet side is protected by the test subject’s flow head. 
  • If the ‘fixed’ flow head is accidentally used by a test subject, then it should be replaced. 
  • Test subjects should not be overstressed by the activities that use the Spirometer. The instructor should make efforts to check the subject is healthy and has no history of cardiovascular or respiratory problems e.g. asthma.
  • The nature of the Spirometer means that some subjects will feel discomfort when using the apparatus. Efforts should be made to put the test subject at ease. Stop the investigation if the test subject’s discomfort becomes too great.
  • The length of the apparatus should not be increased under any circumstance. The apparatus does not contain a flow control valve and therefore increases the anatomical dead space of the subject.

Practical notes

  • Do not try to force the flow heads into the plastic moulding as this could damage the moulding and cover the sensing hole.
  • Best results are obtained if the test subject has become used to breathing through the apparatus before commencing an investigation. A five minute acclimatisation period is recommended. With experience and practice the pattern becomes normal. 
  • It is quite normal for the test subject to experience increased salivation when they first use the Spirometer. Keep the flow heads in the upright position to avoid problems with condensation developing. 
  • After prolonged use the inside of the spirometer’s housing tube may become coated with condensation. It is advisable to check for this occasionally and wipe away as needed. The amount formed will depend upon the temperature of the room and the level of breathing.
  • The nose clip is used to prevent air from entering or leaving the nose as the subject is breathing. It should be used if the results need to be qualitative, e.g. during volume measurements when the air that passes through the nose should not be included. For studies and comparison of breathing patterns a nose clip is not necessary.
  • Make sure that when the Spirometer is in the test subject’s mouth that there is a good seal and that the tongue is kept flat so it does not obscure the opening (they may find biting the Spirometer tube is the best position)
  • Two small lugs are moulded into the housing tube; these have been provided for a thin line or lanyard (e.g. a glasses lanyard) to be attached to support the Spirometer during use.
  • The flow heads carry the and are made from plastic recycle type 5: Polypropylene (PPE). They also carry a ? mark to indicate and confirm that they are for single use (individual) only.
  • If the Spirometer is used with a data logger that records 10 bit instead of 12 bit data (e.g. EasySense Flash, Q3 or Q5) the quality of samples will be lower. This will become more noticeable when data is used to perform calculations (e.g. to derive volume).
  • A 20 ms intersample time (or less) is recommended for the best results.


 NOTE: Single use (individual) only logo.


  • AirFlow – the default range of the Spirometer. This returns a simple change in flow over time.
  • Volume – the airflow has simple integration applied to arrive at a volume range. The volume range is prone to drift due to residual flow data included into the integration. Calculations within the software can also produce volume form flow and apply an adjustment to correct for drift.
  • Adjusted volume – returns a corrected for drift volume. This is accomplished by ensuring that any point with zero flow has a zero volume; in the data collected you may see “jumps” in the data as the correction is made. Ideal for showing ventilation details (inspiratory reserve, expiratory reserve etc).
  • Cyclic volume – gives a volume reading with a baseline of zero. Ideal for measurements of tidal volume.
  • Breathing rate – the data is analysed for peaks to give “breaths per minute”. You will need at least two inhalations to start showing this data and you will get data after you stop breathing due to the analysis taking place.
  • Differential pressure – this is the raw data; it shows the pressure changes with time.


The Spirometer is used to measure both the amount of air that moves in or out of the lungs and how quickly the air is expelled from the lungs. 

  • The amount of air that moves in or out of the lungs during any one breathing cycle is called the tidal volume. Tidal volume is typically 0.5 litres.
  • After normal inspiration it is possible to breathe in additional air – this is called the inspiratory reserve volume. 
  • Similarly, after normal expiration, it is possible to exhale additional air from the lungs – this is called the expiratory reserve volume.
  • Even if the expiratory reserve volume is fully expelled from the lungs, there is still a volume of air in the lungs, called the residual volume, which cannot be exhaled. The residual volume has a very low oxygen and high carbon dioxide concentration.
  • Upon inhalation fresh air mixes with stale air from the residual volume to create air in the alveoli that still has gas concentrations that facilitate the diffusion of oxygen into and carbon dioxide out of the capillaries. 
  • The respiration centre in the medulla ensures that gaseous exchange at the lung matches the requirements of the body. During times of increased demand, the tidal volume can be increased, using some of the reserve lung volumes to bring more fresh air into the body. In addition, the rate of breathing and the rate of air movement in and out of the lungs can be changed. 

Glossary of Abbreviations




Spirometric values


Forced Vital Capacity: the total volume of air that can be forcefully exhaled after maximal inspiration


Forced Expiratory Volume in one second: the volume of air that can be exhaled in 1 second after a maximal inhalation


Forced Expiratory Volume in 6 seconds


The Forced Expiratory Volume in one second as a percentage of the forced vital capacity


Maximal Voluntary Ventilation: the maximum volume of air that can be exhaled under forced exhalation


Peak Expiratory Flow or Peak Flow: the maximum flow achieved at the beginning of the FVC manoeuvre 

Lung volumes


Expiratory Reserve Volume: the maximum volume of air that can be exhaled after a normal end of expiration


Inspiratory Reserve Volume: the maximal volume of air that can be inhaled after a normal end of inspiration


Residual Volume: the volume of air remaining in the lung after a normal exhalation

Lung capacities


Tidal Volume: the volume of air that is inhaled or exhaled with each respiratory cycle whilst breathing without effort


Functional Residual Capacity: the volume remaining in the lung after a normal end expiration


Inspiratory Capacity: the maximal volume of air that can be inspired from a normal resting expiratory level. IC = TV + IRV


Total Lung Capacity: the volume of air in the lungs at maximal inflation


Vital Capacity: the largest volume measured on complete exhalation after full inspiration.