RESPIRATION Dr. Zainab H.H Dept. of Physiology Lec.5,6

Pulmonary Function Tests  Assessed by spirometry.  Subject breathes into a closed system in which air is trapped within a bell floating in water.  The bell moves up when the subject exhales and down when the subject inhales.  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  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  Normal range:  Male = 5.7 liters  Female = 4.2 liters  500 ml of air are inspired and expired  At end of quiet expiration, the lungs still contain 2,200 ml of air  Gas exchange continues during expiration Maintains constant gas content

Pulmonary Function Tests  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 = 3L

3. Expiratory Reserve Volume (ERV) - the maximum amount of gas that ca be expired during forced breathing in addition to tidal volume = 1.1L 4. Residual Volume (RV) - the volume of gas remaining in the lungs after a maximal expiration = 1.2L that keep the alveoli open. Lung Volumes

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 = 2.3L

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) = 5.8L Lung Capacities

Note  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  largest volume of gas that can be moved into and out of the lungs in 1 minute by voluntary effort  Equals to 125 – 170 L/min.

Factors Affecting Lung Volumes and Vital Capacity 1. Body build or physique 2. Position of the body 3. Strength of respiratory muscles 4. Pulmonary compliance

Restrictive and Obstructive Disorders  Restrictive pulmonary/lung diseases  Expansion of lungs restricted & compliance of lungs  i.e.,  Fibrosis  Pulmonary edema  Obstructive pulmonary diseases  Airflow limitation (resistance is high), i.e.,  Chronic obstructive pulmonary diseases (COPD)  Asthma

 FEV 1 (Forced expiratory volume in 1 st second): Volume of forced vital capacity (FVC) exhaled in the first second of expiration  Normal ratio of FEV 1 /FVC ~ 0.8 or 80%  In obstructive pulmonry diseases, ratio is  70% Forced Expiratory Volume in 1 st second (FEV 1 )

Maximal inspiration Maximal expiration or normal

Which of the following is/are decreased in both restrictive and obstructive lung diseases: vital capacity, FEV1, FEV1/FVC?

 In obstructive airways disease.  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.