SPIROMETRY

SPIROMETRY

• “Pulmonary ventilation is studied by recording the volume movement of air into & out of the lungs”.

Spirometer

• Device where one breathes into & out of it.

• Volume of air breathed in or out are measured

PARAMETERS 

Spirometry can measure:- 

• Tidal volume (TV)

• Inspiratory reserve volume (IRV)

• Expiratory reserve volume (ERV)

• Vital capacity (VC)

• Forced vital capacity (FVC/FEV1)

Spirometry cannot measure- 

• Residual volume (RV)

• Functional residual capacity (FRC)

• Total lung capacity (TLC)

PULMONARY FUNCTION TEST	NORMAL VALUE (95 PERCENT CONFIDENCE INTERVAL)
FEV1	80% to 120%
FVC	80% to 120%
Absolute FEV1 /FVC ratio	Within 5% of the predicted ratio
TLC	80% to 120%
FRC	75% to 120%
RV	75% to 120%
DLCO	> 60% to < 120%

DLCO = diffusing capacity of lung for carbon monoxide.

INDICATIONS:

• Diagnose or manage asthma

• Detect respiratory disease in patients presenting with symptoms of breathlessness, and to distinguish respiratory from cardiac disease as the cause

• Measure bronchial responsiveness in patients suspected of having asthma

• Diagnose and differentiate between obstructive lung disease and restrictive lung disease

• Follow the natural history of disease in respiratory conditions

• Assess of impairment from occupational asthma

• Identify those at risk from pulmonary barotrauma while scuba diving

• Conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery

• Measure response to treatment of conditions which spirometry detects

• Diagnose the vocal cord dysfunction.

CONTRAINDICATIONS:

• Forced expiratory maneuvers may aggravate some medical conditions. 

Hence, contra-indicated in

• Hemoptysis of unknown origin

• Pneumothorax

• Unstable cardiovascular status (angina, recent myocardial infarction, etc.)

• Thoracic, abdominal, or cerebral aneurysms

• Cataracts or recent eye surgery

• Recent thoracic or abdominal surgery

• Nausea, vomiting, or acute illness

• Recent or current viral infection

• Undiagnosed hypertension

PROCEDURE:

• Basic forced volume vital capacity (FVC) test varies slightly depending on the equipment used.

• Generally, the patient is asked to take the deepest breath they can and then exhale into the sensor as hard as possible, for as long as possible, preferably at least 6 seconds. 

• It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction. 

• Sometimes, the test will be preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the rapid breath in (forced inspiratory part) will come before the forced exhalation.

• During the test, soft nose clips may be used to prevent air escaping through the nose. Filter mouthpieces may be used to prevent the spread of microorganisms.

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