Introduction
Spirometry is a key tool in the diagnosis and monitoring of respiratory disease. The following document produced by the ARTP may be implemented within any practice where applicable. It outlines safe practice in the performance of quality assured spirometry.
Scope and Aims
This document covers a standard procedure which can be utilised in any healthcare setting where spirometry is performed. It is intended as a basic guideline that can be adapted alongside local protocols.
These test procedures are taken from the recommendations of the ARTP (Association for Respiratory Technology and Physiology) publication ‘ARTP statement on pulmonary function testing 2020’. Updates to this document are unlikely to alter the test procedures significantly, but where an update occurs, readers should refer to these.
Background
Spirometry is a useful test to aid in the diagnosis of lung disease, and determine the degree of any impairment of lung volumes and flows. It provides several different values that indicate dynamic lung volumes. Spirometry should not be used in isolation when making diagnoses and clinical decisions, and should always be used alongside other investigations and clinical judgement.
The vital capacity (VC) is the maximal volume of air that can either be exhaled from the point of full inspiration or inspired from the point of full expiration. This can be measured as a relaxed/slow manoeuvre (SVC) or a maximal forced manoeuvre (FVC). The forced expiratory volume within the first second (FEV1) is measured during the measurement of FVC to determine the presence of airway disease when expressed as a fraction of either the FVC (FEV1/FVC) or SVC (FEV1/SVC). The greatest value of FVC or SVC should be used, thus the lowest ratio should be used to indicate the degree of obstruction.
The measurement of maximal flow is known as the peak expiratory flow (PEF), which is measured during the first few milliseconds of a forced expiratory manoeuvre. It can be a useful indicator of lung compliance or limitation due to increased airway resistance.