RESPIRATION Dr Zainab H H Dept of Physiology
RESPIRATION Dr. Zainab H. H Dept. of Physiology Lec. 5, 6
Pulmonary Function Tests Assessed by spirometry. q Subject breathes into a closed system in which air is trapped within a bell floating in water. q The bell moves up when the subject exhales and down when the subject inhales. q q As the person breathes in & out through a tube connecting the mouth to the spirometer, the bell containing air moves up & down
Pulmonary Function Tests q q q The bell is attached by a pulley to a pen that writes on paper attached to a rotating drum A downward pen deflection represents expiration & an upward pen deflection represents inspiration The recording is known as spirogram
Spirometer
Pulmonary Function Tests q Normal range: q Male = 5. 7 liters q Female = 4. 2 liters 500 ml of air are inspired and expired q At end of quiet expiration, the lungs still contain 2, 200 ml of air q q Gas exchange continues during expiration Maintains constant gas content
Pulmonary Function Tests q q q The spirogram shows 4 lung volumes & 4 lung capacities Values given are for adult males (70 kg) Normal values of lung volume & capacities depend on: 1. Age 2. Sex 3. Posture 4. height
Lung Volumes 1. Tidal Volume (TV): volume of air inhaled or exhaled with each breath = 0. 5 L 2. Inspiratory Reserve Volume (IRV): maximum volume of air that can be inhaled after a normal tidal volume inhalation = 3 L
Lung Volumes 3. Expiratory Reserve Volume (ERV) - the maximum amount of gas that ca be expired during forced breathing in addition to tidal volume = 1. 1 L 4. Residual Volume (RV) - the volume of gas remaining in the lungs after a maximal expiration = 1. 2 L that keep the alveoli open.
Lung Capacities 1. Inspiratory Capacity (IC) - the maximum amount of gas that can be inspired after a normal tidal expiration IC = TV + IRV = 3. 5 L 2. Functional Residual Capacity (FRC) - the amount of gas remaining in the lungs after a normal tidal expiration. FRC = ERV + RV = 2. 3 L
Lung Capacities 3. Vital Capacity (VC) - the maximum amount of gas that can be expired after a maximum inspiration VC = IRV + TV + ERV (= IC + ERV) 4. Total Lung Capacity (TLC) - total amount of gas in the lungs after a maximum inspiration TLC = TV + IRV + ERV + RV (= IC + FRC) or (= VC + RV) = 5. 8 L
Note q q n Volumes and capacities cannot be measured directly with spirometer are: FRC RV TLC Functional residual capacity is determined by nitrogen wash-out method or helium dilution method and then residual volume and total lung capacity are calculated.
Maximal Voluntary Ventilation Also called maximal breathing Capacity q largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort q Equals to 125 – 170 L/min. q
Factors Affecting Lung Volumes and Vital Capacity 1. 2. 3. 4. Body build or physique Position of the body Strength of respiratory muscles Pulmonary compliance
Restrictive and Obstructive Disorders q Restrictive pulmonary/lung diseases q q Expansion of lungs restricted & compliance of lungs i. e. , q Fibrosis q Pulmonary edema Obstructive pulmonary diseases q Airflow limitation (resistance is high), i. e. , q Chronic obstructive pulmonary diseases (COPD) q Asthma
Forced Expiratory Volume in 1 st second (FEV 1) q FEV 1 (Forced expiratory volume in 1 st second): Volume of forced vital capacity (FVC) exhaled in the first second of expiration q Normal ratio of FEV 1/FVC ~ 0. 8 or 80% q In obstructive pulmonry diseases, ratio is 70%
Maximal inspiration Maximal expiration or normal
n n Which of the following is/are decreased in both restrictive and obstructive lung diseases: vital capacity, FEV 1/FVC?
In obstructive airways disease. q The increase in intrapleural pressure may act to compress airways proximal to the alveoli further obstruction with no increase in expiratory flow and air-trapping distally. q
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