Lung volume and lung capacity By DR AGBARAOLORUNPO F Lung volume and lung capacity By DR AGBARAOLORUNPO F.M Department of Physiology College of Medicine University of Lagos

Respiratory rate in adult is 12 times/minute movement of 6litre of air in and out of the lungs in a minute minute ventilation or pulmonary ventilation=Tidal volume X RR Alveolar ventilation=tidal volume-dead space X RR (500-150X 12=4200ml/min) Movement of 500ml of air in and out of the lung per breath(Tidal Volume,VT)

Spirometer-for measuring volume of air exchanged during breathing and rate of ventilation The record is called spirogram/spirometry Inspiration is recorded as upward deflection ,while expiration is recorded as downward deflection

Spirometry measuring of breath) is the most common of the pulmonary function tests (PFTs). It measures volume and/or speed (flow) of air inhaled and exhaled in the lung. to diagnose asthma, pulmonary fibrosis, cystic fibrosis, and COPD.

Procedure Generally, the patient is asked to take quiet breathing, followed by deepest breath they can, and then exhale into the sensor as hard as possible, for at least 6 seconds. 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

LUNG VOLUME TIDAL VOLUME: The volume of air entering or leaving the lungs during normal quiet breathing=500ml Inspiratory reserve volume: Extra volume of air that can be maximally inspired above tidal volume(3L) Expiratory Reserve Volume: Extra Volume of air that can be maximally expired above tidal volume(1L) Residual Volume: volume of air in the lung after maximal expiration/exhalation(1200ml)

LUNG CAPACITY Inspiratory Capacity: IC=IRV+TV Vital Capacity: Maximum volume of air that can be moved out during a single breathe following a maximal inspiration: The subject first inspires maximally,then expires maximally (VC=IRV+TV+ ERV). Use to ascertain the functional capacity of the lungs. average=4500ml. it represent the maximum volume change possible within the lungs. Functional Residual Capacity: Volume of air in the lungs at the end of a normal passive expiration (FRC=ERV+RV),2200ml. Total lung capacity(TLC): The maximum volume of air that the lungs can hold(TLC=VC+RV)=average value=5700ml

IRV 3.3 1.9 TV 0.5** ERV 1.0* 0.7 RV 1.2* 1.1 TOTAL LUNG CAPACITY 6.0** 4.2** Respiratoy minute volume (6L/min) Alveolar ventilation (rest):4.2L/min**

Forced vital capacity (FVC) Forced vital capacity (FVC) is the volume of air that can forcibly be blown out after full inspiration, FVC is the most basic maneuver in spirometry tests. Forced expiratory volume in 1 second (FEV1) FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Average values for FEV1 in healthy people depend mainly on sex and age, Values between 80% and 120% of the average value are considered normal. Predicted normal values for FEV1 depend on age, sex, height, mass and ethnicity

FEV1/FVC ratio (FEV1%) FEV1/FVC (FEV1%) is the ratio of FEV1 to FVC. In healthy adults this should be approximately 70–85% (declining with age). In obstructive diseases (asthma, COPD, chronic bronchitis, emphysema) FEV1 is diminished because of increased airway resistance to expiratory flow;

Force expiratory volume in one second(FEV1): Volume of air that can be expelled from lungs in 1 second with maximal effort following a maximal inhalation. FEV1 is about 80% of the air that can be forcefully expired from maximally inflated lungs within 1 second(80% of VC forcefully expires in one second ) FEV1 can be greatly reduced in asthma and emphysema

Spirometry can be used to diagnosed both obstructive and restrictive lung disease Obstructive disease Patient experiences difficulty emptying lungs than filling them FRC and RV are elevated as a result of the additional air trapped in the lungs following expiration FEV1 reduced, due to the reduction in air flow rate by the airway obstruction

FEV1/FVC ratio is reduced below 80%

Spirogram in restrictive lung diseases Lungs are less compliant in restrictive lung diseases ( expand less) TLC,IC and FVC are reduced FEV1/VC ratio(the percentage of the VC that can be exhaled within 1 second is the normal 80%) is normal or higher because air can flow freely in the airway. RV is normal in restrictive lung diseases