BMS 100 Clinical Physiology IV Fall 2022 PDF

Clinical Physiology IV Fundamental Physiologic Basis of the Lung Exam Dr. Hobson BMS 100 Week 4 The Lung Exam Lung Anatomy Respiratory Structures Trachea, Lobes, Bronchi, Bronchioles & Alveoli Muscles Of Respiration Basic Respiratory Physiology Mechanisms Of Ventilation Regions of Ventilation R...

Clinical Physiology IV Fundamental Physiologic Basis of the Lung Exam Dr. Hobson BMS 100 Week 4 The Lung Exam Lung Anatomy Respiratory Structures Trachea, Lobes, Bronchi, Bronchioles & Alveoli Muscles Of Respiration Basic Respiratory Physiology Mechanisms Of Ventilation Regions of Ventilation Regions of Respiration (diffusion) The Respiratory Physical Exam Surface Anatomy Auscultation And Abnormalities Percussion And Abnormalities Structures of the Respiratory System • Nasal cavity and nasopharynx • Nasopharynx = the “back of the nose and throat” that leads to the larynx • Larynx • Cartilaginous structure that contains the vocal folds • Trachea • Midline, non-paired conducting airway • Bronchi • Branching airways that contain variable amounts of cartilage Gross Anatomy Of The Lungs Structures of the Respiratory System • Bronchioles • Branching airways that lack cartilage but are surrounded by smooth muscle • Alveoli • Delicate, balloon-like structures that are the main sites of gas exchange • Site of pulmonary microvasculature Ventilation vs. Diffusion Ventilation - conducting zone: • • • Movement of gas is driven by pressure gradients • Diffusion is not the major driving force Skeletal muscles change the volume of the thoracic cavity → pressure changes → air movement through conducting airways Conducting Airways: • Nasopharynx → terminal bronchiole • Volume – 150 mL Ventilation vs. Diffusion Diffusion – the respiratory or “exchange” zone: • Movement of gas is driven by concentration gradients • Pressure changes “mix” the air, but distances are small enough that diffusion is effective in gas movement • Many small structures of the lung that occupy the majority of the lung volume • Respiratory bronchiole → alveoli • Volume after a quiet inspiration = 3 L • Closely associated with pulmonary microvasculature The Basics of the Ventilatory Apparatus Ventilatory apparatus: • Lungs • Conducting and exchanging airways • Pleural space • Chest wall • Muscles • Chest wall muscles – intercostals, scalenes, SCM • Diaphragm How does it work? • The muscles change the volume of the chest wall/thoracic space • Volume changes → pressure changes in the lung Basic Ventilatory Mechanics Inspiration • The external intercostals and diaphragm contract ▪ Ext. intercostals – ribs move up and out ▪ Diaphragm – descends with contraction • The volume of the thoracic cavity increases → a decrease in the intrathoracic pressure • Drop in intrathoracic pressure → drop in pressure of the airspaces of the lungs → movement of air from atmosphere into lungs Basic Ventilatory Mechanics Expiration • The diaphragm and external intercostals relax ▪ Ext. intercostals – relax, and ribs move down and in ▪ Diaphragm – rises on relaxation • The volume of the thoracic cavity decreases → an increase in the intrathoracic pressure • Increase in intrathoracic pressure → airspaces of the lungs increase pressure → movement of air from lungs back to the atmosphere The Pleura • How do the chest wall/diaphragm “connect” to the delicate lungs? ▪ Note the pleural cavity – movements of the chest wall and diaphragm are “tied” to it The Pleura • The pleural cavity ▪ Contains an amazingly small amount of fluid (10 – 20 mL) ▪ The fluid “connects” the chest wall to the delicate alveoli ▪ Movements of the thoracic cage and diaphragm → changes in the pleural cavity pressure → changes in the alveolar pressure Surface Anatomy Of The Lungs Surface Anatomy Of The Lungs • Fissure dividing the superior lobe from the middle lobe, anteriorly: • 4th rib – 4th intercostal space • Red indicates “inflated” lung after inspiration, blue indicates after expiration • Bifurcation of the trachea is located under the sternum close to the joint of the 3rd rib Surface Anatomy of the Lungs Surface Anatomy of the Lungs • The vast majority of the lung tissue deep to the posterior thorax is the inferior lobe • The inferior lobe airspaces descend from the 10th rib posteriorly to the 12th on deep inspiration Brief look at the nasal cavity, nasopharynx, larynx Roles: • Warming and moistening of air • Nasal cavity • Phonation (speaking) and protection of the airways from food/liquids • Larynx • More as you learn about the head & neck exam Brief look at the nasal cavity, nasopharynx, larynx A model of the lung • This model represents the major structures of the respiratory system: • Conducting airways • Gas exchange airways • Microvasculature • Diaphragm and chest wall/thoracic cavity • Intrapleural space Consequence of Pulmonary Disease – Pleural Effusion Fluid in the pleural space = pleural effusion – here it’s unilateral • Often makes it difficult for the airspaces to expand • Makes it difficult to hear breath sounds, lungs are dull to percussion • The fluid is “in the way” of auscultation and the echo from percussion • Causes: • Cancer, infection (i.e. pneumonia), trauma Consequence of Pulmonary Disease – Pleural Effusion Fluid in the pleural space = pleural effusion – here it’s bilateral • Again, difficult for the airspaces to expand • Makes it difficult to hear breath sounds, lungs are dull to percussion • The fluid is “in the way” of auscultation and the echo from percussion • Causes: • Congestion due to heart failure • Bilateral infection, inflammation Consequence of Pulmonary Disease – Consolidation “Gunk” in the airways and alveoli → consolidation • Fluid in the airspaces transmits sound better than air • You can hear the patient speak more clearly while auscultating the lungs (bronchophony) • Dull to percussion • Decreased breath sounds and/or crackles • Coarse crackles = pathological fluid in large airways • Fine crackles → smaller airways (usually) Consequence of Pulmonary Disease – Consolidation “Gunk” in the larger airways and alveoli → consolidation • Most causes of consolidation are infectious • Major ones are pneumonia and chronic obstructive pulmonary disease • However, sometimes when an airway is obstructed by a tumour, other growth, or foreign body then “gunk” collects and can’t be cleared • Collapse of that region of lung or pneumonia often develop Consequence of Pulmonary Disease – Consolidation In this example, coarse crackles, bronchophony, decreased breath sounds, and dullness to percussion would be found more superior in the lung Consequences of Pulmonary Disease – Fluid in Small Airways • When fluid or secretions are found mostly in small airways, you get “fine crackles” ▪ Rub your hairs together close to your ears – sounds like that ▪ Common with pulmonary edema due to infection or congestive heart failure • Fine crackles can also occur when small airways “snap” open during some types of COPD Consequences of Pulmonary Disease – Wheeze • When a small airway is narrowed or constricted, you hear a high-pitched, musical sound on expiration • Known as a wheeze • Wheezes are common in obstructive disease: ▪ Asthma ▪ COPD ▪ Pulmonary edema when fluid collects in the respiratory and terminal bronchioles Consequences of Pulmonary Disease – Stridor • When a large airway is narrowed or constricted, you hear a louder, harsher sound on inspiration and sometimes on expiration • Known as stridor • Stridor occurs when the upper airways (trachea and above) are obstructed due to infection, trauma, or a foreign body getting “stuck” (aspiration)