BMS 100 Clinical Physiology IV Fall 2022 PDF

Clinical Physiology IV Fundamental Physiologic Basis of the Lung Exam Dr. Hobson BMS 100 Week 4 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 voca...

Clinical Physiology IV Fundamental Physiologic Basis of the Lung Exam Dr. Hobson BMS 100 Week 4 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 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 • 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)