2023 Prac 14 Lung Volume (PDF)

Practical 14: Lung Volumes (Spirometry) Learning outcomes - Determine lung volumes and capacities and effect of age and exercise. - Discuss the impact of diseases such as asthma and HIV/AIDS Organisation of the Respiratory system 26-2 The process of...

Practical 14: Lung Volumes (Spirometry) Learning outcomes - Determine lung volumes and capacities and effect of age and exercise. - Discuss the impact of diseases such as asthma and HIV/AIDS Organisation of the Respiratory system 26-2 The process of respiration involves 3 integrated steps: 1. Pulmonary ventilation (breathing) – physical movement of air into and out of the lungs – requires pressure gradients to exist between the outside of the body and the alveoli 2. Gas exchange – involves gas diffusion, i) External respiration: between the air in lungs and blood in alveoli and ii) Internal respiration: between blood & other tissues 3. Gas transport – transport of O2 & CO2 in the blood between the alveolar capillaries and the capillary beds in other tissues 26-3  Respiratory volumes and capacities During a single quiet respiratory cycle (breath in and out) only a small portion of air is exchanged in the lungs. Air moves through the respiratory system from area of higher pressure to area of lower pressure Lung volumes The maximum volume to which a lung can be expanded are divided into 4 non- overlapping volumes: a) Tidal volume (TV) – volume of air inspired or expired with each breath during normal quiet breathing (± 500 ml) b) Inspiratory reserve volume (IRV) – the extra volume of air that can be inhaled by a maximum inspiratory effort over and above the normal tidal volume (± 3000 ml) 26-4  Respiratory volumes and capacities Lung volumes c) Expiratory reserve volume (ERV) – the extra volume of air that can be exhaled by a maximum forceful expiration over and above the normal tidal volume (± 1000 ml) d) Residual volume (RV) – volume of air that remains in the lungs after the most forceful expiration (± 1200 ml) – minimal volume = a component of residual volume & amount of air that would remain in lungs if allowed to collapse 26-5  MALE FEMALE IRV 3300 1900 Inspiratory Vital Capacity VT 500 500 Capacity ERV 1000 700 Functional Residual volume 1200 1100 Residual Capacity 26-6 Total lung capacity 6000ml 4200ml  Respiratory volumes and capacities Lung capacities these capacities are a combination of two or more lung volumes a) Inspiratory capacity (IC) – maximum volume of air that can be inspired after normal tidal expiration –  IC = TV + IRV = 3500 ml b) Expiratory capacity (EC) – maximum volume of air that can be expired after normal tidal inspiration –  EC = TV + ERV = 1500 ml 26-7  Respiratory volumes and capacities Lung capacities d) Vital capacity (VC) – maximum volume of air that a person can expel after the deepest possible inspiration –  VC = TV + IRV + ERV = 4500 ml – depends on various factors: size of thoracic cavity age strength of respiratory muscles gravity pregnancy pulmonary diseases e) Total lung capacity (TLC) – volume of air present in the lungs after maximal inspiration –  TLC = VC + RV = 5700 ml 26-8 Spirometer: - measures the rate at which the lung changes vol. during forced breathing maneuvres. - Pulmonary functional test are designed to - identify and quantify functional abnormalities of the respiratory system - diagnose several lung disease. - Monitor medical treatment - Most informative tests is measuring the forced expiratory volume and forced vital capacity. - Results obtained from test can help classify lung disease as obstructive or restrictive. Respiratory diseases BRONCHITIS Chronic obstructive pulmonary diseases: difficulty is expelling all the air of the lungs. Eg asthma, bronchitis, emphysema, influenza (flu) Restrictive Lung diseases: reduced total lung capacity leads to difficulty in maximal inhalation of air in lungs. Eg Neuromuscular diseases, ALS stb.msn.com (amyotropic lateral sclerosis), obesity, HIV and its related lung infections. TUBERCULOSIS (TB) HIV patients possibility of a decrease immune system which allows common lung infections to become lethal. Pneumonia and Tuberculosis can lead to a decrease in lung capacity due to damage of lung tissue. www.scielo.org.ve