Key Themes in Respiration - Dr Wai Ling Kok (2023-24).pptx

Key Themes in Respiration Dr Wai Ling Kok Case 1.13 Acknowledgement Dr Vehid Salih Learning Objectives Describe the structure & function of the respiratory system Describe the physiology of the respiratory system Describe gaseous exchange, transport and ventilation in respiration Recognise effects o...

Key Themes in Respiration Dr Wai Ling Kok Case 1.13 Acknowledgement Dr Vehid Salih Learning Objectives Describe the structure & function of the respiratory system Describe the physiology of the respiratory system Describe gaseous exchange, transport and ventilation in respiration Recognise effects of various clinical correlations/pathologies on respiratory function Structures of the respiratory systems Essentials of human anatomy and physiology, 2021 Functions of the respiratory system Smell perception Sound production Cellular respiration Gas exchange Temperature and humidity regulation Core concepts Respiration refers to the use of oxygen by an organism to make energy, with the production of carbon dioxide as a waste product The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide. Vital Signs Heart rate Oxygen saturation Respiratory rate Blood Pressure Temperature Level of consciousness How many of these can we record in the dental surgery? Respiratory Status in the Dental Surgery General appearance Skin colour Speech Respiratory rate Respiratory effort Respiratory volumes Pulse rate Fingers/finger clubbing Breathing How much? How often? Spirometry Key Definitions 1 – Pulmonary volumes Tidal volume The volume of air inspired or expired during a normal inspiration or expiration Inspiratory reserve volume The amount of air inspired forcefully after inspiration of normal tidal volume Expiratory reserve volume The amount of air forcefully expired after expiration of normal tidal volume Residual volume The volume of air remaining in respiratory passage and lungs after the most forceful expiration Key Definitions 2 – Pulmonary capacities Inspiratory capacity Tidal volume + inspiratory reserve volume Functional residual capacity Expiratory reserve volume + residual volume Vital capacity Tidal volume + inspiratory reserve volume + expiratory reserve volume Total lung capacity Tidal volume + inspiratory reserve volume + expiratory reserve volume + residual volume Pulmonary Volumes Inspiratory reserve volume Inspiratory capacity Tidal volume Expiratory reserve volume Residual volume Functional residual capacity Spirogram showing lung volumes and capacities in a healthy young adult male Vital capacity Total lung capacity Pulmonary Volumes FEV1/FVC A ratio that reflects the amount of air you can forcefully exhale from your lungs (as measured by Spirometry – used to ascertain lung function FEV1 = Forced Expiratory Volume in 1 s, OR the volume of breath exhaled with effort in 1 s FVC = Forced Vital Capacity, or the full amount of air that can be exhaled with effort in a complete breath Clinical correlation This helps identify the type of condition you have Restrictive lung diseases (e.g. pulmonary fibrosis) affect your ability to inhale (FEV1/FVC >= 70%) Obstructive conditions (e.g. asthma and COPD incl. emphysema and chronic bronchitis) affect your ability to exhale (FEV1/FVC < 70%) Alveolar Gas Exchange Alveolar Gas Exchange Gas exchange occurs at two sites in the body: in the lungs, where O2 is picked up and CO2 is released at the respiratory membrane, and at the tissues, where O2 is released and CO2 is picked up Laws ofLdiffusion applies!! External respiration (breathing) takes place in the lungs. During this process the O2 from the inhaled air is transferred to the blood and the CO2 diffuses from blood into the air Internal respiration refers to cellular processes that allow the transfer of O2 from red blood cells through the capillary wall into the tissues and thereby for use within the cell. Both processes depend on the partial pressures of O2 and CO2. Essentials of Human Anatomy and Physiology, 2021 Alveolar Gas Exchange Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. The consumption of O2 leads to major fluctuations in the partial pressure of O2, which drops from 100 mmHg in the arterial blood to 40 mmHg in venous blood. In contrast, the fluctuations of CO2 are much smaller, from 40 mmHg in arterial blood to 46 mmHg in venous blood. Alveolar Gas Exchange & Ventilation To increase pulmonary ventilation (e.g. during exercise) – increase tidal volume and respiratory rate because of the dead space it is more advantageous to increase the depth as opposed to the rate of breathing Alveolar dead space is defined as ventilated alveolar not adequately perfused with blood, significant in disease state e.g. COPD Both blood flow and ventilation vary from bottom to top of the lung Ventilation may not exactly match perfusion leading to variation in the effectiveness of gas exchange Gas transport - CO2 Transport Gas transport - O2 Transport Adult Haemoglobin (Hb) and O2 Transport pH, CO2, temp; shifts the curve to the left This reflects an increased affinity in the ability of Hb to take up oxygen and retain oxygen pH, CO2, temp; shifts the curve to the right This reflects a decreased affinity of Hb for O2, increased tendency to give up oxygen to the tissues 2,3 diphosphoglycerate The oxyhaemoglobin dissociation curve Contin Educ Anaesth Crit Care Pain, Volume 12, Issue 5, 2012 Similarly, an increase in erythrocyte DPG decreases Hb oxygen affinity and vice versa This relationship between pH and oxygen carrying capacity is termed the Bohr effect (reduction in oxygen affinity of Hb when pH is low and increase in affinity when pH is high) Fetal Haemoglobin (HbF) and O2 Transport Clinical correlations: Carboxyhaemoglobin (HbCO) Clinical correlations: Haemoglobinopathies Clinical correlations: Ageing Vital capacity and the amount of air moved in and out of the respiratory system per minute decreases The residual volume and dead space increase The ability to remove mucus from respiratory passageways decreases Gas exchange across respiratory membrane is reduced Abbreviations: DLCO, diffusing capacity of carbon monoxide; FEV1, forced expiratory volume in one second; FVC, forced vital capacity; TLC, total lung capacity; VO 2, oxygen consumption; VA, alveolar volume Clinical correlations: Hyperventilation Removal of CO2 in the lungs exceeds body’s production Maybe voluntary or involuntary [CO2] in the blood falls to give hypocapnia May lead to rise in blood pH (respiratory alkalosis) The amount of freely ionised calcium in the blood is pH dependent, as pH rises less is available The loss of respiratory drive and reduction in [Ca2+] leads to respiratory alkalosis https://patient.info/doctor/hyperventilation Clinical correlations: Drugs Depressants Inhalational anaesthetics Opiates Benzodiazepines Alcohol Naloxone Stimulants Doxapram Progesterone Aminophylline SDL - update