Introduction to Breathing PDF

Introduction to breathing What is respiration? Respiration, as the term is generally used, includes two processes: External respiration the absorption of O2 and removal of CO2 from the body as a whole...

Introduction to breathing What is respiration? Respiration, as the term is generally used, includes two processes: External respiration the absorption of O2 and removal of CO2 from the body as a whole Internal respiration the utilization of O2 and production of CO2 by cells and the gaseous exchanges between the cells and their fluid medium. Means many things to many people The utilisation of oxygen by cells to make energy The act of breathing Brain: How is breathing controlled The respiratory centres in the brain stem are also affected by Chemoreceptors Introduction to breathing 1  Voluntary actions: breathing faster etc. Respiratory pace-maker is there as a fail-safe If you try to hold your breath, you will pass out and your respiratory pacemaker will take over the control of breathing Spontaneous respiration is controlled by the medulla: respiratory pacemaker Chemoreceptors and Breathing control In terms of the control of breathing, the main thing that directs this is the level of CO2 and pH, which affects the central and peripheral chemoreceptors. It is more sensitive to these than the levels of oxygen in the blood Increased CO2 and increased acidity results in greater breathing rate to remove this excess CO2 and restore the optimum level Introduction to breathing 2  Ventilation / Perfusion To enable pulmonary gas exchange, we need adequate ventilation and perfusion Main gas exchange is diffusion of gases across the alveolar membrane Introduction to breathing 3  Haemoglobin A tetramer: 2 alpha and 2 beta subunits Each subunit has a haem group A porphyrin with a central Ferrous atom: binds O2 Combines loosely with oxygen Combination alters its shape and charge The oxygen haemoglobin dissociation curve Carriage and disposal of CO2 Introduction to breathing 4  Summary Breathing occurs to allow adequate oxygenation of tissues The control is both voluntary and involuntary Oxygen is carried in the blood bound to haemoglobin CO2 is mostly dissolved in the blood Hb is designed to pick up O2 in the lungs and drop off at tissues Why do we need oxygen? Essential for aerobic respiration Glycolysis ATP = energy Introduction to breathing 5  Adequate oxygenation requires A supply of oxygen Lung that works Heart that works Haemoglobin to carry it Increases in altitude lead to decreases in available oxygen Introduction to breathing 6  How do we quantify oxygen carriage? Haemoglobin saturation Because it’s very easy to do! Assuming Hb is normal, it’s an accurate reflection of oxygen content Arterial blood gases More complicated and invasive PaO2 reflects haemoglobin saturation but is a measure of the partial pressure of O2 in the blood How to measure haemoglobin saturation? Oxygenated haemoglobin is RED Deoxygenated haemoglobin is BLE Using absorption spectroscopy, it is possibly to estimate the degree of saturation of haemoglobin SpO2, pulse oximetry Introduction to breathing 7  What does a blood gas measure? PaO2 PaCO2 pH Bicarbonate Some analysers may also measure electrolytes and Hb Other forms of haemoglobin Carboxyhaemoglobin PA = partial pressure in alveolus Pa = partial pressure in arterial circulation Introduction to breathing 8  Summary Oxygen is essential for normal metabolic processes The level of oxygen delivered to blood is dependent on the level of oxygen in the environment Most O2 in the blood is bound to Hb We can measure this invasively or non-invasively CO2 requires an invasive approach while oxygen can be either Things that can go wrong with respiration: Not enough oxygen in the lungs High altitude Low oxygen environment eg industrial accident Diseases that obstruct flow of air (and oxygen) to the alveolus Introduction to breathing 9  Not enough oxygen getting into the blood Not enough blood into the lungs Reduced capacity in the blood to carry oxygen Cystic fibrosis results in a reduced breathing rate due to mucus build up in airways less oxygen available at alveolar capillary COPD Increased mucous production Destruction of alveoli and connective tissue leading to collapse of conducting airways Narrowed passages of air Introduction to breathing 10  Diseases causing defects in gas exchange Not enough gas getting across alveoli Something in the way of gas exchange eg acute inflammation/pus/water Chronic alveolar thickening eg pulmonary fibrosis Pneumonia Causes inflammation and damage in the small airways and alveoli Not enough oxygen gets into blood Causes ventilation to perfusion (V/Q) mismatch Introduction to breathing 11  Treat by increasing oxygen provision to the alveoli Introduction to breathing 12  Pulmonary Embolism is caused by not enough blood passing through CT scans Treatment of low oxygen Treat the underlying cause Introduction to breathing 13  antibiotics for bacterial pneumonia bronchodilators for asthma/COPD Diuretics for pulmonary oedema Anti-coagulation for pulmonary embolism Give oxygen therapy Oxygen Therapy: Masks Variable performance Cheap and cheerful Exact inspired O2 concentration not known Fixed function Constant, known inspired concentration Reservoir mask High inspired concentration of O2 Invasive Ventilation is required for severe respiratory failure not responding to oxygen therapy Not a suitable treatment for all patients Provided in intensive therapy units Summary Low oxygen levels are a feature of many respiratory problems, particularly in the acute setting Treatment depends on the disease In acute settings with low oxygen giving supplemental oxygen is an excellent treatment Introduction to breathing 14