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Respiratory Physiology RESPIRATORY PHYSIOLOGY Trym Reiberg • Ida Sletteng Karlsen • Alexandra Kathryn Vedeler First Edition 27 March 2019 Copyright StudyAid 2019 Authors Ida Sletteng Karlsen Trym Reiberg Alexandra Kathryn Vedeler Illustrators Ida Sletteng Karlsen Trym Reiberg Alexandra Kathryn Vedeler Nora Charlotte Sønstebø Booklet Disclaimer All rights reserved. No part of this book may be reproduced in any form on by an electronic or mechanical means, without permission from StudyAid. Although the authors have made every effort to ensure the information in the booklet was correct at date of publishing, the authors do not assume and hereby disclaim any liability to any part for any information that is omitted or possible errors. The material is taken from a variety of academic sources as well as physiology lecturers, but are further incorporated and summarized in an original manner. It is important to note, the material has not been approved by professors of physiology. All illustrations in the booklet are original. This booklet is made especially for students at the Jagiellonian University in Krakow by tutors in the StudyAid group (students at JU). It is available as a PDF and is available for printing. If you have any questions concerning copyrights of the booklet please contact [email protected]. About StudyAid StudyAid is a student organization at the Jagiellonian University in Krakow. Throughout the academic year we host seminars in the major theoretical subjects: anatomy, physiology, biochemistry, immunology, pathophysiology, supplementing the lectures provided by the university. We are a group of 25 tutors, who are students at JU, each with their own field of specialty. To make our seminars as useful and relevant as possible, we teach in an interactive manner often using drawings and diagrams to help students remember the concepts. In addition to most seminars we create booklets, on which the seminars are based to aid the students in following the presentations. If you have any questions, do not hesitate to contact StudyAid at www.studyaid.no, we are always happy to answer any questions you may have academically related or not. 2 TABLE OF CONTENTS SECTION 1 – MECHANICS OF VENTILATION 1.0 – Lung Volumes and Capacities…………………………………………………………………………………………………….4 1.1 – Ventilation…………………………………………………………………………………..……………………………………………..6 1.2 – Mechanics of Ventilation…………………………………………………………………………………..………………………9 1.3 – Test yourself…………………………………………………………………………………..……………………………………….15 SECTION 2 – RESPIRATION . 2.0 – Overview…………………………………………………………………………………………………………………………………17 2.1 – External Respiration…..……………………..………………………………………………………………………………………… ….18 2.2 – Internal Respiration - Oxygen………………….…………………………………………………………………………………….22 2.3 – Internal Respiration – Carbon Dioxide.…………………………………………………………………………………….27 2.4 – Test Yourself…………………………………………………………………………………..……………………………………….29 SECTION 3 – CONTROL OF BREATHING 3.0 – Involuntary Breathing………………………………………………………………………………………………………………32 3.1 – Chemoreceptors………………………………………………………………………………………………………………………36 3.2 – Other Receptors…………………………………………………………………………………………………………………………..39 3.3 – Voluntary Breathing…………………………………………………………………………………………………………………40 3.4 – Test Yourself…………………………………………………………………………………………………………………………….41 SECTION 4 – INTEGRATIVE FUNCTIONS 4.0 – Exercise……………………………………………………………………………………………………………………………………43 4.1 – High Altitude…………………………………………………………………………………………………………………………….46 4.2 – Test Yourself.………………………………………………………………………………………………………………………….....48 3 Section 1 – Mechanics of Ventilation 1.0 – Lung Volumes and Capacities 1.1 – Ventilation 1.2 – Mechanics of Ventilation 1.3 – Test Yourself 1.0 – Lung Volumes and CaPacities I. Lung volumes - Measured by spirometry (exception: RV) - 4 types - Tidal volume (VT), inspiratory reserve volume (IRV), expiratory reserve volume (ERV) and residual volume (RV) II. Lung caPacities - Calculated from the lung volumes (> 2 lung volumes) - 4 types - Inspiratory capacity (IC), vital capacity (VC), functional residual capacity (FRC) and total lung capacity (TLC) 4 III. Summary Term Definition Value Tidal volume (VT) Amount of air inspired or 0,5 L expired during quiet ventilation InsPiratory reserve volume The maximal amount of air 3 L (IRV) that can be inspired with effort at the end of a normal inspiration ExPiratory reserve volume The maximal amount of air 1,2 L (ERV) that can be expired with effort at the end of a normal expiration InsPiratory caPacity (IC) Maximal inhalation after 3,5 L normal expiration Vital caPacity (VC)1 Maximal expiration after 4,7 L maximal inspiration Residual volume (RV)2 Volume remaining in the lungs 1,2 L after maximal expiration Functional residual caPacity Volume remaining in the lungs 2,4 L (FRC)3 after normal expiration 1 Vital capacity (VC) and forced vital capacity (FVC) have the same value, but the process of measurement is different. When measuring VC, the patient takes a full inspiration and blows out the air in a slow maneuver. When measuring FVC, the patient takes a full inspiration and blows out the air in a forceful maneuver. 2 If we did not have any residual volume, the lungs would collapse. 3 Equilibrium volume of the lung. 5 1.1 – Ventilation 1.1.1 – Definition - Refers to the movement of air between the atmosphere and the lungs through the process of inspiration and expiration - It must be distinguished from respiration Ventilation ResPiration Mechanical Ventilation + diffusion + perfusion 1.1.2 – Structure of the ResPiratory System I. Conducting zone - Composed of the airways (trachea, bronchus, bronchioles and terminal bronchioles) - Does not participate in gas exchange II. ResPiratory zone - Composed of the lungs (respiratory bronchioles, alveolar ducts and alveolar sacs) - Participates in gas exchange 6 1.1.3 – Minute Ventilation (VM) I. Definition - Refers to the total volume of gas that enters the respiratory system per minute II. Equation III. Calculation 1.1.4 - Alveolar Ventilation (VA) I. Definition - Refers to the volume of gas that reaches the alveoli per minute II. Equation 7 III. Calculation 1.1.5 – Dead Space I. Definition - Refers to the volume of gas that does not participate in gas exchange - It may be considered as “wasted ventilation” - Divided into physiological- and pathological dead space II. Physiological dead sPace - Composed of anatomical- and alveolar dead space - Anatomical dead sPace: Volume of gas within the conducting zone - Alveolar dead sPace: Volume of gas within unperfused alveoli - The ratio of the physiological dead space to the tidal volume is ≈1/3 III. Pathological dead sPace - Chronic obstructive pulmonary disease (COPD) - Pulmonary embolism (PE) 8 1.2 – Mechanics of Ventilation 1.2.1 – Overview 1.2.2 – InsPiration I. Muscles Quiet insPiration Forced insPiration DiaPhragm - Major muscle Sternocleidomastoid - Contraction of the - Contraction of the sternocleidomastoid à diaphragm à downward elevation of the sternum displacement - Increases the - Increases the vertical anteroposterior diameter diameter of the thoracic of the thoracic cavity cavity External intercostal - Minor muscle Scalene muscles - Contraction of the muscles - Contraction of the scalene muscles à external intercostal elevation of the upper muscles à ribs are lifted ribs up and out - Increases the - Increases the anteroposterior diameter anteroposterior - and of the thoracic cavity horizontal diameter of the thoracic cavity Note: Inspiration is an active process (regardless of whether it is quiet or forced) 9 1 cm H2O = 0.74 mmHg II. Forces 1. IntraPleural Pressure - Represents the pressure in the pleural cavity - Subatmospheric (negative) - Expanding force 10 III. Clinical correlation CLINICAL CORRELATION Pneumothorax - When a sharp object penetrates the chest wall and punctures the intrapleural space – a connection is created between the atmosphere and the pleural space - Air flows into the pleural cavity along the pressure gradient until the intrapleural pressure equals the atmospheric pressure - There are two important clinical consequences of a pneumothorax; 1. CollaPsed lung 2. ExPansion of the chest wall 1.2.3 – ExPiration I. Muscles Quiet expiration Forced exPiration Abdominal muscles - Major muscle - Contraction of the abdominal muscles à upward displacement of the diaphragm - Decreases the vertical diameter of the thoracic cavity Internal intercostal - Minor muscle muscles - Contraction of the internal intercostal muscles à ribs are pulled down and in - Decreases the anteroposterior- and horizontal diameter of the thoracic cavity Note: Quiet expiration is a passive process, while forced expiration is an active process 11 II. Forces 1. Elastic recoil of the lung - Represents the tension in the wall of the lung - It is determined by LaPlace law and the inherent elasticity of the lung - Collapsing force 12 III. Clinical correlation CLINICAL CORRELATION ResPiratory distress syndrome (RDS) - Surfactant is synthesized by type II pneumocytes - The most important constituent of surfactant is dipalmitoylphosphatidylcholine (DPPC) - The production of surfactant occurs between 24th and 34th week of gestation - Infants born before 24th week of gestation à never have surfactant th th - Infants born between 24 and 34 week of gestation à uncertain surfactant status - Lack of surfactant produces the following consequences; 1. Increased surface tension - Collapse of alveoli 2. UnoPPosed LaPlace Law - Collapse of small alveoli 1.2.4 – Ventilatory Cycle 13 1.2.5 – Clinical Correlations Restrictive lung disease Obstructive
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