Title 17. PULMONARY FUNCTION TESTS.pdf ✅

PHARMD GURU Page 1 ANATOMY AND PHYSIOLOGY OF LUNGS:  Left and right lungs are in the pleural cavity of the thorax.  Right lung has three lobes, but the left has only two lobes; space is thus provided for the heart.  Lungs are connected to pharynx by trachea.  Trachea splits into left and right main stem bronchi that deliver inspired air to respective lungs. PULMONARY FUNCTION TESTS: Pulmonary function tests are a group of procedures that measure the function of the lungs, revealing problems in the way a patient breathes. The tests can determine the cause of shortness of breath and may help confirm lung diseases, such as asthma, bronchitis or emphysema. The tests also are performed before any major lung surgery to make sure the person won't be disabled by having a reduced lung capacity. CONTRAINDICATIONS: 1) Recent eye surgery. 2) Thoracic , abdominal and cerebral aneurysms. 3) Active haemoptysis. 4) Pneumothorax. 5) Unstable angina/ recent MI within 1 month. RESPIRATORY FUNCTIONS ARE ASSESSED BY: 1) lung volume tests 2) Lung flow tests. 1) LUNG VOLUME TESTS:  Expiratory reserve volume (ERV)  Slow vital capacity (SVC)  Residual volume (RV)  Functional residual capacity (FRC) PULMONARY FUNCTION TESTS
PHARMD GURU Page 2  Inspiratory capacity (IC)  Inspiratory reserve volume (IRV)  Tidal volume (TV)  Total lung capacity (TLC). 2) LUNG FLOW TESTS: 1) Forced expiratory volume (FEV) 2) Peak expiratory flow rate (PEFR) 3) FORCED EXPIRATORY FLOW (FEF): These can be measured by spirometry LUNG VOLUME TESTS: Lung volume tests indicate the amount of gas contained in the lungs at various stages of inflation. 1) TIDAL VOLUME:  Amount of air inhaled or exhaled at rest.  Reference range: 500 to 750 ml.  It is infrequently used as a measure of respiratory disease. 2) INSPIRATORY CAPACITY (IC):  The volume measured from the point of the TV where inhalation normally begins to maximal inspiration is known as IC.  Reference range: 500 ml + 3.1 L = 3.6 L.
PHARMD GURU Page 3 3) INSPIRATORY RESERVE VOLUME:  Amount of air that is inhaled with maximal inhalation after the normal inhalation. (OR)  The volume measured from the “top” of the TV, (i.e. the initial point of normal exhalation) to maximal inspiration is known as the IRV.  Reference range: 3.1 L. 4) EXPIRATORY RESERVE VOLUME:  Amount of air that is exhaled with maximal expiration after the normal exhalation. (OR)  During exhalation, the volume from the “bottom” of the TV (i.e, Initial point of normal inhalation) to maximal expiration is referred to as ERV.  Reference range: 1. 2 L. 5) SLOW VITAL CAPACITY:  When the full inhalation-exhalation procedures is repeated slowly – instead of forcefully and rapidly – it is known as SVC.  This value is the maximum amount of air exhaled after a full and complete inhalation.  In patients with normal airway function, SVC and FVC are usually similar (hence shown as Vital Capacity).  In patients with diseases, such as COPD during the initial stages of disease, the FVC decreases before the SVC (because inter luminal thoracic pressures are not elevated during the forced manoeuvre). 6) RESIDUAL VOLUME:  Amount of air that is left in the lungs after full exhalation.  Reference range: 1. 2 litre.  RV is immeasurable by spirometry but measurable by body plethysmography.  Without RV lungs would collapse like deflated balloons.  In asthma, RV increases due to obstruction. 7) FUNCTIONAL RESIDUAL CAPACITY:  It is the volume of the gas remaining in the lungs at the end of the TV.  It is the sum of the ERV and RV [2.4L]