RCP 110LOWER AIRWAY REVISED.docx

**Tracheal Bronchial Tree 🌳** **Overview** The tracheal bronchial tree is a series of branching airways commonly referred to as **generations**. The airways become progressively smaller, shorter, and more numerous as you move down the lungs. **Cartilaginous and Non-Cartilaginous Airways** There...

**Tracheal Bronchial Tree 🌳** **Overview** The tracheal bronchial tree is a series of branching airways commonly referred to as **generations**. The airways become progressively smaller, shorter, and more numerous as you move down the lungs. **Cartilaginous and Non-Cartilaginous Airways** There are two major forms of airways: - **Cartilaginous airways**: serve only as conductors, conducting air between the external environment and the sites of gas exchange. (Generations 0-9) - **Non-Cartilaginous airways**: serve as both conductors and sites of gas exchange. (Generations 10-19, 20-28) **Tracheal Bronchial Tree Layers** The tracheal bronchial tree has three layers: - **Epithelial lining**: composed of pseudostratified ciliated columnar epithelium, with mucus glands and a lubricant layer. - **Lamina propria**: a layer of connective tissue with immunologic response. - **Cartilaginous layer**: provides structural support. **Epithelial Lining** - **Pseudostratified ciliated columnar epithelium**: extends from the top of the trachea to the respiratory bronchioles. - **Mucus layer (mucus blanket)**: responsible for grabbing pathogens or antigens and removing them from the lungs. Composed of: - 95% water - 5% glycoproteins, carbohydrates, lipids, DNA, and other cellular debris - Produced by goblet cells and submucosal glands - **Gel layer**: a viscous layer that lies closer to the lumenal surface. - **Sol layer**: a thinner layer that lies adjacent to the epithelial lining. **Mucociliary Transport Mechanism (Mucociliary Escalator)** - **Definition**: the process by which cilia propel mucus and foreign particles out of the lungs. *\"The mucociliary escalator is like an escalator that takes you up to the next floor. It helps move mucus and secretions upward and outward towards the main stem bronchi, where they can be coughed out.\"* - **How it works**: - Cilia move mucus and secretions upward towards the main stem bronchi. - At the main stem bronchi, the mucus is coughed out. - The mucociliary escalator helps remove foreign particles and pathogens from the lungs. **Key Terms** **Term** **Definition** -------------------------- --------------------------------------------------------------------------------- Cartilaginous airway An airway that serves only as a conductor. Non-Cartilaginous airway An airway that serves as both a conductor and a site of gas exchange. Respiratory zone The region of the tracheal bronchial tree where gas exchange occurs. Mucociliary escalator The process by which cilia propel mucus and foreign particles out of the lungs. Gel layer A viscous layer of mucus that lies closer to the lumenal surface. Sol layer A thinner layer of mucus that lies adjacent to the epithelial lining. The mucociliary escalator is a transport mechanism within the lungs responsible for cleansing the airway. However, there are factors that can slow it down. **Factors Affecting Mucociliary Escalator Function** - **Cigarette smoke**: paralyzes the cilia, reducing their movement and effectiveness - **Dehydration**: reduces the function of cilia, leading to a vicious circle of illness - **Positive pressure ventilation**: can damage cilia, especially at higher pressures - **Endotracheal suctioning**: can cause cilia damage - **High FiO2**: high levels of oxygen can paralyze cilia, making them less effective **FiO2: Fraction of Inspired Oxygen 💧** *FiO2 stands for fraction of inspired oxygen, which is the fraction of oxygen in any volume of gas being measured.* - Atmospheric air has a FiO2 of 21% - Patients on room air receive 21% oxygen, which is sufficient for healthy individuals - Patients with lung disease or illness may require higher FiO2 levels to meet their oxygen needs **Hypoxia and Hypoxemia ⚠️** - **Hypoxia**: lack of oxygen in the tissues, affecting all organs - **Hypoxemia**: lack of oxygen in the blood, leading to tissue death **Other Factors Affecting Airway Clearance** - **Atmospheric pollutants**: can affect the mucociliary escalator, particularly in individuals working in certain environments - **General anesthetics**: can paralyze cilia, making it harder to cough up secretions - **Parasympatolytics**: drugs that block the effects of the parasympathetic nervous system, which can affect airway clearance **Clinical Connection: Patients with Excessive Secretions 👨‍⚕️** Two pathophysiologies commonly cause excessive bronchial secretions: - **Cystic fibrosis** - **Chronic bronchitis (COPD)** **Effects of Excessive Secretions** - Thick, immobile secretions result in: - Partial airway obstruction and air trapping - Airway hyperinflation - Complete airway obstruction and airway collapse **Air Trapping and Hyperinflation 🌈** - Air trapping: air gets in, but only a small portion comes out, due to excessive secretions blocking the airway - Hyperinflation: the thoracic cavity becomes over-inflated, leading to a barrel chest appearance **Key Terms** **Term** **Definition** ----------------------- ------------------------------------------------------------------------------------------------------- Air trapping Air gets in, but only a small portion comes out, due to excessive secretions blocking the airway Hyperinflation The thoracic cavity becomes over-inflated, leading to a barrel chest appearance FiO2 Fraction of inspired oxygen Hypoxia Lack of oxygen in the tissues, affecting all organs Hypoxemia Lack of oxygen in the blood, leading to tissue death Mucociliary escalator A transport mechanism within the lungs responsible for cleansing the airway Parasympatolytics Drugs that block the effects of the parasympathetic nervous system, which can affect airway clearance **Airway Obstruction** Airway floss is like a balloon that can pop when it gets overly inflated, leading to **atelectasis**, or airway collapse. **Asthma Attack** During an asthma attack, it\'s not secretions that cause the issue, but rather **smooth muscle constriction**. The airways constrict, making it difficult for air to escape. We can treat this with **bronchodilators**, such as albuterol, which open up the airways. **Modalities of Care** There are several modalities of care to help treat excessive airway secretions, including: - Postural drainage - Chest PT (chest percussion) - Flutter or Acapella - Cough breathing exercises - Suctioning These modalities will be covered in more detail in RCP 120. **Airway Compliance** **Compliance** refers to how well the lungs can receive a volume of gas. Think of it like a rubber band: *\"Compliance is how well the lungs accept gas.\"* When a rubber band is new, it\'s stiff and has high elasticity. As you use it, it stretches out and becomes more pliable. But eventually, it breaks. Similarly, our lungs have a certain level of compliance, and if we stretch them too much, they can break (or in this case, become damaged). **The Respiratory System** The respiratory system has two main issues: - **Airway persistence**: the airway\'s ability to maintain patency - **Compliance issues**: the lung\'s ability to receive gas **The Epithelial Lining** The epithelial lining is the innermost layer of the airway. It\'s where we find the **lamina propria**, which contains loose fibrous tissue, tiny blood vessels, lymphatic vessels, and the vagus nerve. **The Subepithelial Layer** The subepithelial layer contains two sets of smooth muscle fibers that wrap around the tracheobronchial tree and extend to the alveolar ducts. It\'s surrounded by a thin connective tissue layer called the **parabronchial sheath**. **Immune Response** In the lamina propria, we find mast cells that play an important role in the immunological mechanism. When activated, they release substances that can alter the diameter of the bronchial airway. This can lead to **bronchospasm**, which causes wheezing. **Substance Released** **Effect** ------------------------ ----------------------------------------------- Histamines Increase mucus production, cause bronchospasm Leukotrienes Increase mucus production, cause bronchospasm Heparin Increase mucus production **Asthma** In asthma, the body overreacts to an **antigen** (or allergen), releasing IgE antibodies that bind to mast cells. This causes the release of chemical mediators, leading to: - Bronchospasm - Mucus plugging - Air trapping - Lung hyperinflation **The Cartilaginous Layer** The cartilaginous layer is the outermost layer of the airway, decreasing in size as the airways extend to the lungs. It serves to conduct air from the atmosphere to the sites of gas exchange. **Airway Anatomy** **Section** **Description** ---------------------- ------------------------------------------------------- Trachea Conducts air from atmosphere to sites of gas exchange Mainstem Bronchi Bifurcates into left and right bronchi Lobar Bronchi Branch into segmental bronchi Segmental Bronchi Branch into subsegmental bronchi Subsegmental Bronchi Conduct air to sites of gas exchange The airway can be broken down into 5 sections: The trachea, or **windpipe**, is anterior to the esophagus and attached to the cricoid cartilage at C6. It bifurcates into left and right mainstem bronchi at T5.\#\# Trachea Anatomy and Intubation 🌿 **Length and Diameter of the Trachea** The trachea is approximately 11-13 cm long in men and 11 cm long in women. The diameter of the trachea ranges from 1.5 to 2.5 cm, with men typically having a larger diameter than women. **Why is this important?** - Understanding the length and diameter of the trachea is crucial for intubation and establishing an airway. - Knowing the patient\'s size and airway requirements helps determine the correct size of the tracheal tube. **C-Shaped Cartilages** The trachea is supported and protected by C-shaped cartilages. *\"The C-shaped cartilages do not completely surround the trachea to allow for the esophagus to have its elasticity, enabling us to eat and swallow.\"* **Why are the cartilages C-shaped?** - To make room for the esophagus - To allow for the esophagus to remain pliable and functional **Importance of the Carina** The carina is a landmark for intubation and confirming placement of airways. **Key point:** - When orally intubating, the end of the endotracheal tube should be 2-5 cm above the carina to ensure adequate ventilation. **Chest X-Rays** Chest X-rays help diagnose respiratory issues and confirm the placement of endotracheal tubes. **Key points:** - Black areas on a chest X-ray represent air - White areas represent tissue, fluid, or other substances that shouldn\'t be there - Clavicles are easily identifiable landmarks on a chest X-ray - The trachea bifurcates into the right and left mainstem bronchi around T5 **Case Study: Migrated Endotracheal Tube** A chest X-ray shows a patient with an endotracheal tube that has migrated into the right mainstem bronchus, causing the left lung to collapse. **Key points:** **Observation** **Conclusion** -------------------------------------------------- ---------------------------------------------------------------------- White area in the left lung The left lung is collapsed Endotracheal tube in the right mainstem bronchus The tube has migrated too far and is only ventilating the right lung Hyperflated right lung The right lung is being over-ventilated **Solution:** - Pull the endotracheal tube back to 2-5 cm above the carina to restore ventilation to both lungs.\#\# Anatomy of the Airway 🌲 **Importance of Landmarks** - Knowing the anatomy of the airway is crucial for intubations and patient care. - This information is not just important for a test, but also for real-life scenarios as a medical professional. **Retaining Information** - Flashcards and Quizlets can be helpful in retaining information. - Make sure to review and practice regularly to keep the information fresh in your mind. **Trachea and Bronchi 🔍** - The trachea bifurcates into the right and left mainstem bronchi. - Right mainstem bronchus: - Falls at a 25-degree angle - Wider than the left - More vertical than the left - Shorter than the left - Left mainstem bronchus: - Falls at a 40-60 degree angle - More horizontal than the right - Longer than the right **Generations of Bronchi** **Generation** **Description** ---------------- -------------------------------------------------------------------------------- 1st Right and left mainstem bronchi 2nd Right divides into upper, middle, and lower; Left divides into upper and lower 3rd Segmental bronchi (10 in the right lung, 8 in the left lung) **Segment** **Name** **Location** ------------- ----------------- --------------------------- 1 Apical Upper lobe, apex (point) 2 Posterior Upper lobe, back 3 Anterior Upper lobe, front 4 Lateral Middle lobe, outside 5 Medial Middle lobe, middle 6 Superior Lower lobe, upper 7 Medial Basal Lower lobe, middle, base 8 Anterior Basal Lower lobe, front, base 9 Posterior Basal Lower lobe, back, base 10 Lateral Basal Lower lobe, outside, base **Segmental Bronchi** - Each segmental bronchus is named according to its location within a particular lung lobe. - There are 10 segmental bronchi in the right lung and 8 in the left lung. **Right Lung Segmental Bronchi** **Importance of Understanding Segmental Bronchi** - Understanding segmental bronchi is crucial for postural drainage and chest PT. - Knowing the location of mucus or pneumonia in a patient\'s lung can help position them to drain secretions. **Higher Generations** - 4th through 9th generation bronchi range in diameter from 1-4 millimeters. - These bronchi have a lot of nerves, lymphatic vessels, and bronchial arteries surrounding them. - The connective tissue sheath disappears after the subsegmental ranges. **Definitions** *Apex: the top or point of something (e.g., the apex of the heart is the bottom pointy part) Posterior: towards the back Anterior: towards the front Lateral: towards the outside Medial: towards the middle Superior: higher or above\#\# Terminal Bronchioles 🌿* Bronchioles with a diameter of less than 1 millimeter, characterized by: - No connective tissue sheets - Surrounded by smooth muscle fibers - Low rigidity, meaning they are flexible and open (high patency) **Asthma and Bronchioles** In asthma, the smooth muscle in the bronchioles constricts, increasing airway resistance and decreasing the ability to ventilate. This is why asthma patients often experience spasms in the airways. **Non-Cartilaginous Terminal Bronchioles 🌿** - Average diameter of 0.5 mm - No connective tissue sheets - No mucus glands - No cilia - Presence of: - Canal of Lamberts: small channels between the terminal bronchioles and alveoli - Clara cells: cells that take thick protoplasmic extensions and play a role in detoxing gas that enters the alveoli **Canal of Lamberts** *A compensatory mechanism created by the body in response to diseases such as COPD, cystic fibrosis, or bronchiectasis. The canal of Lamberts are thought to be a way for the body to create its own pathway for oxygenation and ventilation.* **Clara Cells** *Clara cells play a crucial role in detoxing gas that enters the alveoli, acting as a filter to keep toxins out.* **Bronchial Cross-Sectional Area 📏** The total cross-sectional area of the tracheobronchial tree increases from the trachea to the terminal bronchioles. - Structures distal to the terminal bronchioles (farther away from the trachea) have a larger surface area - The respiratory zone, comprising alveolar ducts, sacs, and alveoli, has the largest surface area *If all the alveoli in the human lungs were laid out flat, they would cover an area the size of a tennis court.* **Bronchial Blood Supply 💉** The bronchial arteries nourish the lungs, providing oxygen to the tracheobronchial tree, lymph nodes, pulmonary nerves, and portions of the esophagus and pleura. **Bronchial Arterial Blood Flow** **Description** ----------------------------------- -------------------------------------------------------------- 1% of cardiac output Blood flow that nourishes the lungs Arises from the aorta Oxygenated blood from the heart Follows the tracheobronchial tree Feeds oxygen to the lungs as far as the terminal bronchioles **Bronchiolovenous Blood** - Low in oxygen, high in CO2 - Mixes with blood that has passed through the alveolar-capillary membrane - Returns to the heart to be reoxygenated **Functional Units of the Lungs 🌈** *A group of structures that work together to perform a specific function.* The functional unit of the lungs is the respiratory zone, where gas exchange occurs. **Functional Unit** **Description** --------------------- ------------------------------------------------------------------------- Respiratory Zone Where gas exchange occurs, comprising alveolar ducts, sacs, and alveoli **Functional Units of the Respiratory System** The functional units of the respiratory system are located in the **long parenchyma**, which includes: - **Respiratory bronchioles** - **Alveolar ducts** - **Alveolar clusters** **Alveoli** The alveoli are small sacs where gas exchange takes place. They are made up of three types of cells: **Cell Type** **Description** **Function** --------------- ------------------------ ------------------------------------------------------------------------- **Type 1** Broad, thin cells Make up 95% of alveolar surface; cannot reproduce **Type 2** 5% of alveolar surface Produce **pulmonary surfactant**; can reproduce itself and type 1 cells **Type 3** Play a major role in removal of bacteria and foreign pathogens **Pulmonary Surfactant** *Pulmonary surfactant is a lubricant that helps to offset the tension in the alveoli, preventing them from collapsing.* Pulmonary surfactant is produced by **Type 2 cells** and is essential for babies to take their first breath after birth. Without it, the alveoli would collapse, making it difficult to breathe. **Pores of Kohn** The **pores of Kohn** are small holes in the walls of the **intraalveolar septa**, allowing gas to move from one alveolus to the next. They form due to: - Peeling away of epithelial cells (**desquamation**) - Normal degeneration of cells with age - Movement of macrophages leaving holes in the alveolar walls **Alveolar Structure** The alveolar structure consists of: - **Respiratory bronchiole**: breaks off into the **alveolar duct** - **Alveolar duct**: leads to the **alveolar sac**, which is made up of many **alveoli** There are approximately 150,000,000 alveoli in each lung, and they continue to develop until toddler age. **Interstitium** The **interstitium** is the space surrounding the alveoli, supported and shaped by the interstitial layer. It has two major components: - **Loose space**: has water content, which can increase by up to 30% before a significant pressure change develops - **Tight space**: area between the alveolar epithelium and endothelium, significant for pulmonary capillaries Collagen fibers in the interstitium help to limit alveolar distensibility, preventing them from becoming overly inflated.