Physiology Lab Spirometry

Objectives: Explain the main concepts of lung volumes and capacities. Describe the Spirometer and explain its importance. Observe experimentally the Spirometry. Measure the FEV1/FVC & its interpretation.

Lung volumes and capacities Measurement of lung volumes provides a tool for understanding normal function of the lungs as well as disease states.

Tidal Volume: volume of air inspired & expired with each normal breath Tidal Volume: volume of air inspired & expired with each normal breath. Normal TV is approximately 500 ml (Ganng)The amount of air that moves into the lungs with each inspiration (or the amount that moves out with each expiration) is called the tidal volume. The air inspired with a maximal inspiratory effort in excess of the tidal volume is the inspiratory reserve volume. The volume expelled by an active expiratory effort after passive expiration is the expiratory reserve volume, and the air left in the lungs after a maximal expiratory effort is the residual volume. Normal values for these lung volumes, and names applied to combinations of them, are shown in .The space in the conducting zone of the airways occupied by gas that does not exchange with blood in the pulmonary vessels is the respiratory dead space. The vital capacity, the largest amount of air that can be expired after a maximal inspiratory effort, is frequently measured clinically as an index of pulmonary function. It gives useful information about the strength of the respiratory muscles and other aspects of pulmonary function. The fraction of the vital capacity expired during the first second of a forced expiration (FEV1, timed vital capacity, gives additional information; the vital capacity may be normal but the FEV1 reduced in diseases such as asthma, in which airway resistance is increased because of bronchial constriction. The amount of air inspired per minute (pulmonary ventilation, respiratory minute volume) is normally about 6 L (500 mL/breath × 12 breaths/min). The maximal voluntary ventilation (MVV), or, as it was formerly called, the maximal breathing capacity, is the largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort. The normal MVV is 125-170 L/min.

Vital Capacity: Is IRV+TV+ ERV. Normal VC is approximately 4600 ml Vital Capacity: Is IRV+TV+ ERV. Normal VC is approximately 4600 ml .Is the volume of air that can be expired forcefully after taking maximum inspiration.

What is Spirometry? Spirometry: Is the most common of the Pulmonary Function Tests (PFTs) Is a method of assessing lung function by measuring the volume(amount)& flow(speed) of air the patient can expel from the lungs after a maximal inspiration

Why Perform Spirometry? Measure airflow obstruction to help make a definitive diagnosis . Distinguish between Obstructive and Restrictive diseases of the lungs.

Spirometers

Standard Spirometric Indices The Spirometer calculates different ventilation parameters: FVC - Forced vital capacity: The total volume of air that can be forcibly exhaled in one breath after taking maximum inspiration FEV1 - Forced expiratory volume in one second: The volume of air that can be expired in the first second during forceful expiration

Predicted Normal Values Affected by: Age Height Weight Sex Ethnic Origin

FEV1 curve Normally the whole FVC is expelled in four seconds Forced expiratory volume (FEV1): the volume of air expelled in the first second of a forced Exhalation. In normal subjects 75-80% of the FVC can be expelled in the first second. FEV1/FVC : the normal value is 75-80%. Anything below this is considered abnormal.

Flow- volume loop Spirometry is a valuable tool for analyzing the flow rate of air passing into and out of the lungs. Flow volume loops provide a graphical illustration of a patient's spirometric efforts.

Spirogram Patterns Normal Obstructive Restrictive

obstructive and restrictive diseases Lung disease is often divided into two broad categories: obstructive disease and restrictive disease. Examples of obstructive disease are Emphysema, Chronic Bronchitis, and bronchial Asthma. Examples of restrictive disease are abnormalities of the spine and chest and diseases within the lungs that make them less elastic (“stiffer”), such as pulmonary fibrosis.

Criteria for Normal FVC: more than 80% of predicted value FEV1: more than 80% of predicted value FEV1% : 70 to 80%

Normal Trace Showing FEV1 and FVC 5 4 FVC = 5L FEV1 = 4L FEV1% = 80% Volume, liters 3 2 1 1 1 2 3 4 5 6 Time, seconds

Spirometry: Obstructive Disease Volume, liters Time, seconds 5 4 3 2 1 6 FEV1 = 1.8L FVC = 3.2L FEV1/FVC = 0.56 Normal Obstructive Reduced peak flow Slow rise, reduced volume expired; prolonged time to full expiration Diagnosis of COPD is confirmed by FEV1% less than 70%

Spirometry: Restrictive Disease Volume, liters Time, seconds 1 2 3 4 5 6 Normal Restrictive FEV1 = 1.9L FVC = 2.0L FEV1/FVC = 0.95 Normal shape, reduced volume Fast rise to plateau at reduced maximum volume Diagnosis of Restrictive Lung Disease – FVC decreased, FEV1 decreased but FEV1 % normal or above normal

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