EHR519 2024-30 Week 11a Intro to the Pulmonary System PDF

Warning This material has been produced and communicated to you by or on behalf of Charles Sturt University in accordance with section 113P of the copyright act (Act). The material in this communication may by subject to copyright under the act. Any further reproduction or c...

Warning This material has been produced and communicated to you by or on behalf of Charles Sturt University in accordance with section 113P of the copyright act (Act). The material in this communication may by subject to copyright under the act. Any further reproduction or communication of this material by you may be the subject of copyright protection under this act. Do not remove this notice 1 Introduction to the pulmonary system, common diagnostic procedures and nutritional considerations Week 11 Week 11 Overview 1. Pulmonary System Refresher 2. Prevalence 3. Diagnostic Procedures 4. Nutritional Guidelines Learning Outcomes be able to explain the pathophysiology of pulmonary conditions as it relates to exercise physiology; be able to outline the risk factors, complications and co-morbidities that must be accounted for when applying exercise interventions to individuals with pulmonary conditions; be able to explain the diagnostic techniques and treatment procedures used in the treatment of pulmonary conditions; be able to demonstrate the ability to conduct exercise/fitness/functional tests on individuals with pulmonary conditions; be able to prescribe exercise as a therapeutic modality for individuals with pulmonary conditions. Pulmonary System Respiration Pulmonary respiration Ventilation Exchange of O2 and CO2 in the lungs Cellular respiration O2 utilization and CO2 production by the tissues Purposes of the respiratory system during exercise Gas exchange between the environment and the body Regulation of acid-base balance during exercise Conducting zone Conducts air to respiratory zone Humidifies, warms, and filters air Components: Trachea Bronchial tree Respiratory zone Bronchioles Exchange of gases between air and blood Components: Respiratory bronchioles Alveolar sacs Surfactant prevents alveolar collapse EQUAL LOW HIGH Muscles associated with respiration Pulmonary Ventilation Respiratory airflow is governed by the same principles as blood flow Flow, pressure, and resistance The flow of a fluid is directly proportional to the pressure difference between two points The flow of a fluid is inversely proportional to the resistance Atmospheric pressure drives respiration 760 mm Hg at sea level, or 1 atmosphere (1 atm) – Lower at higher elevations  Boyle’s Law At a given temperature, the pressure of a given quantity of gas is inversely proportional to its volume If the lungs contain a quantity of a gas and the lung volume increases, their internal pressure (intrapulmonary pressure) falls – If the pressure falls below atmospheric pressure, the air moves into the lungs If the lung volume decreases, intrapulmonary pressure rises – If the pressure rises above atmospheric pressure, the air moves out of the lungs  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. No airflow Atmospheric pressure 760 mm Hg The two pleural layers, Pleural cavity Diaphragm Intrapulmonary pressure 760 mm Hg Intrapleural pressure 756 mm Hg their cohesive attraction to each other, and their connections to the lungs and their lining of the rib Ribs swing upward like bucket handles 1 At rest, atmospheric and intrapulmonary pressures cage bring about during inspiration. are equal, and there is no airflow. Ribs swing downward like bucket handles inspiration during expiration. 2 Inspiration 4 Pause Airflow Airflow Charles’s law—the given Intrapleural quantity of a gas is directly Intrapleural pressure –6 mm Hg pressure –4 mm Hg Intrapulmonary proportional to its absolute Intrapulmonary pressure –3 mm Hg pressure +3 mm Hg temperature On a cool day, 16°C air will Diaphragm flattens 3 Expiration Diaphragm rises increase its temperature by 21°C during inspiration Rib Inhaled air is warmed to Rib Rib 37°C by the time it reaches Rib Sternum Sternum Sternum Sternum the alveoli Ribs elevated, thoracic Sternum swings up, Ribs depressed, thoracic Sternum swings down, cavity expands laterally thoracic cavity expands cavity narrows thoracic cavity contracts anteriorly posteriorly 2 In inspiration, the thoracic cavity expands laterally,vertically 3 In expiration, the thoracic cavity contracts in all three directions; and anteriorly; intrapulmonary pressure drops 3 mm Hg below intrapulmonary pressure rises 3 mm Hg above atmospheric atmospheric pressure, and air flows into the lungs. pressure, and air flows out of the lungs.  Resistance to Airflow Like pressure, resistance is a determinant of airflow ↑ resistance = ↓ airflow 3 factors: Diameter of bronchioles Bronchodilation – increase in diameter (Epinephrine) Brochoconstriction – reduction in diameter (Histamine, Ach, cold air, irritants) Pulmonary compliance Ease with which lungs expand or change volume relative to a given pressure change Degenerative lung diseases Surface tension of the alveoli and distal Thin film of water in alveoli → draws walls of alveoli inward toward lumen Surfactant – agent that disrupts hydrogen bonds of water and reduces surface tension  Alveolar Ventilation Only air that enters the alveoli is available for gas exchange About 150 mL fills the conducting division of the airway Anatomical dead space Conducting division of airway where there is no gas exchange Can be altered somewhat by sympathetic and parasympathetic stimulation NB: In some restrictive pulmonary conditions, alveoli may be unable to exchange gases because they lack blood flow or the respiratory membrane has been thickened by edema or fibrosis  Physiological (total) dead space Sum of anatomic dead space and any pathological alveolar dead space A person inhales 500 mL of air, and 150 mL stays in anatomical dead space, then 350 mL reaches alveoli Alveolar ventilation rate (AVR) Air that ventilates alveoli (350 mL) X respiratory rate (12 bpm) = 4,200 mL/min. Of all the measurements, this one is most directly relevant to the body’s ability to get oxygen to the tissues and dispose of carbon dioxide Residual volume 1,300 mL that cannot be exhaled with maximum effort Neural Control of Breathing  Exact mechanism for setting the rhythm of respiration remains unknown  Breathing depends on repetitive stimuli of skeletal muscles from brain  Ceases if nerve connections to thoracic muscles are severed  Controlled by 2 regions of the brain  Cerebral and conscious  Automatic and unconscious (medulla oblongata and pons)  Voluntary Control Voluntary control over breathing originates in the motor cortex of frontal lobe of the cerebrum Sends impulses down corticospinal tracts to respiratory neurons in spinal cord, bypassing brainstem Limits to voluntary control Breaking point: when CO2 levels rise to a point when automatic controls override one’s will  Involuntary Control  Respiratory nuclei in medulla  Ventral respiratory group (VRG)  Primary generator of the respiratory rhythm  Inspiratory neurons in quiet breathing fire  Expiratory neurons in quiet breathing fire - allowing inspiratory muscles to relax  Produces a respiratory rhythm (12 breaths/min)  Dorsal respiratory group (DRG)  Modifies the rate and depth of breathing  Receives influences from external sources  Pons  Pontine respiratory group (PRG)  Modifies rhythm of the VRG  Adapts breathing to special circumstances such as sleep, exercise, vocalization, and emotional responses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Key Inputs to respiratory centers of medulla Outputs to spinal centers and respiratory muscles Output from hypothalamus, limbic system, and higher brain centers Pons Pontine respiratory group (PRG) Dorsal respiratory Central chemoreceptors group (DRG) Glossopharyngeal n. Ventral respiratory Vagus n. group (VRG) Medulla oblongata Intercostal nn. Spinal integrating centers Phrenic n. Diaphragm and intercostal muscles Accessory muscles of respiration  Input to the Respiratory Centres  Variations in respiratory rhythm are possible because the respiratory centres of the medulla and pons receive input from several other levels of the nervous system  Hyperventilation—breathing is so rapid that it expels CO2 from the body faster than it is produced  Blood CO2 levels drop → pH rises →cerebral arteries constrict  Reduces cerebral perfusion → dizziness or fainting  Can be brought under control by having the person rebreathe the expired CO2 from a paper bag  Sensory Receptors Central chemoreceptors—brainstem neurons that respond to changes in pH of cerebrospinal fluid pH of cerebrospinal fluid reflects the CO2 level in the blood Peripheral chemoreceptors—located in the carotid and aortic bodies of the large arteries above the heart Respond to the O2 and CO2 content and the pH of blood Stretch receptors—found in the smooth muscles of bronchi and bronchioles, and in the visceral pleura Irritant receptors—nerve endings amid the epithelial cells of the airway Sends signals to respiratory and bronchial muscles causing protective reflexes such as bronchial constriction, shallow breathing, breath holding or coughing  Alveolar Gas Exchange  The back-and-forth traffic of O2 and CO2 across the respiratory membrane  Air in the alveolus is in contact with a film of water covering the alveolar epithelium  For oxygen to get into the blood it must dissolve in this water Pass through the respiratory membrane separating the air from the bloodstream Diffuse out of the water film into the alveolar air Alveolar Gas Exchange Gases diffuse down their own concentration gradient until the partial pressure of each gas in the air is equal to its partial pressure in water Henry’s law: at the air–water interface, for a given temperature, the amount of gas that dissolves in the water is determined by its solubility in water and its partial pressure in air The greater the PO2 in the alveolar air, the more O2 the blood picks up Since blood arriving at an alveolus has a higher PCO2 than air, it releases CO2 into the air Several variables affect the efficiency of alveolar exchange and under abnormal conditions, some of these can prevent complete loading and unloading of gases Pressure Gradients of the Gases PO2 = 104 mm Hg in alveolar air versus 40 mm Hg in blood PCO2 = 46 mm Hg in blood arriving versus 40 mm Hg in alveolar air Solubility of the Gases CO2 is 20 times as soluble as O2 – Equal amounts of O2 and CO2 are exchanged across the respiratory membrane because CO2 is much more soluble and diffuses more rapidly O2 is twice as soluble as N2 Membrane Thickness 0.5 m thick Membrane Area 100 mL blood in alveolar capillaries, spread thinly over 70 m2 Ventilation-perfusion Coupling The ability to match ventilation and perfusion to each other  Gas Transport The process of carrying gases from the alveoli to the systemic tissues and vice versa Oxygen transport 98.5% bound to hemoglobin 1.5% dissolved in plasma Carbon dioxide transport 90% carbonic acid/ bicarbonate + H+ 5% bound to amino group 5% dissolved in plasma Relative amounts of CO2 exchanged between the blood and alveolar differ: 70% coming from carbonic acid 23% from carbamino compounds 7% from the dissolved gas I.E. blood gives up the dissolved CO2 gas and CO2 from the carbamino compounds more easily than it gives up the CO2 in bicarbonate  Systematic Gas Exchange The unloading of O2 and loading of CO2 at the systemic capillaries CO2 loading CO2 diffuses into the blood Carbonic anhydrase in RBC catalyzes CO2 + H2O → H2CO3 → HCO3− + H+ Chloride shift – Keeps reaction proceeding, exchanges HCO3− for Cl− – H+ binds to hemoglobin Oxygen unloading H+ binding to HbO2 reduces its affinity for O2 – Tends to make hemoglobin release oxygen Venous reserve: oxygen remaining in the blood after it passes through the capillary beds  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiring tissue Capillary blood 7% CO2 Dissolved CO2 gas CO2 + plasma protein Carbamino compounds 23% CO2 CO2 + Hb HbCO2 Chloride shift Cl– 70% CAH CO2 CO2 + H2O H2CO3 HCO3– + H+ 98.5% O2 O2 + HHb HbO2+ H+ 1.5% Dissolved O2 gas Key O2 Hb Hemoglobin HbCO2 Carbaminohemoglobin HbO2 Oxyhemoglobin HHb Deoxyhemoglobin CAH Carbonic anhydrase  Alveolar Gas Exchange Reactions that occur in the lungs are reverse of systemic gas exchange CO2 unloading As Hb loads O2 its affinity for H+ decreases, H+ dissociates from Hb and binds with HCO3− CO2 + H2O  H2CO3  HCO3− + H+ Reverse chloride shift – HCO3− diffuses back into RBC in exchange for Cl−, free CO2 generated diffuses into alveolus to be exhaled  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolar air Respiratory membrane Capillary blood 7% CO2 Dissolved CO2 gas CO2 + plasma protein Carbamino compounds 23% Chloride shift CO2 CO2 + Hb HbCO2 Cl- 70% CAH CO2 CO2 + H2O H2 CO3 HCO3- + H+ 98.5% O2 O2 + HHb HbO2 + H+ 1.5% O2 Dissolved O2 gas Key Hb Hemoglobin HbCO2 Carbaminohemoglobin HbO2 Oxyhemoglobin HHb Deoxyhemoglobin CAH Carbonic anhydrase  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Adjustments in Gas Exchange 100 90 10ºC 20ºC 38ºC Percentage saturation of hemoglobin 80 43ºC Hemoglobin unloads O2 to match metabolic needs 70 of different states of activity of the tissues 60 50 Normal body temperature 40 Factors that adjust the rate of oxygen unloading 30 20 Ambient PO2 10 – Active tissue has  PO2; O2 is released from Hb 0 0 20 40 60 80 100 120 PO2 (mm Hg) Temperature – Active tissue has  temp; promotes O2 unloading Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 Percentage saturation of hemoglobin 90 pH 7.60 Bohr effect 80 pH 7.40 70 (normal blood pH) – Active tissue has  CO2, which lowers pH of blood; 60 promoting O2 unloading pH 7.20 50 40 Bisphosphoglycerate (BPG) 30 – RBCs produce BPG which binds to Hb; O2 is unloaded 20 – Haldane effect—rate of CO2 loading is also adjusted to 10 varying needs of the tissues, low level of oxyhemoglobin 0 enables the blood to transport more CO2 0 20 40 60 80 100 120 PO2 (mm Hg) Blood Gases and Respiratory Rhythm Rate and depth of breathing adjust to maintain levels of: pH 7.35 to 7.45 PCO2 40 mm Hg PO2 95 mm Hg Brainstem respiratory centres receive input from chemoreceptors that monitor the composition of blood and CSF Most potent stimulus for breathing is pH, followed by CO2, and least significant is O2  End part 1: The pulmonary system and gas exchange (revision) 37