RCP 110 Ventilation Half Chapter 2 notes.docx

**Ventilation 🌬️** **Definition** *The process that moves gases between the external environment and the vascular line.* **Overview** - Ventilation is the process of moving gases from the ambient environment to the vascular line, passing through the conducting airways and into the alve...

**Ventilation 🌬️** **Definition** *The process that moves gases between the external environment and the vascular line.* **Overview** - Ventilation is the process of moving gases from the ambient environment to the vascular line, passing through the conducting airways and into the alveoli where gas exchange happens. - As Respiratory Therapists, we must understand: - Mechanisms of ventilation - Elastic properties of the lungs and chest wall - Dynamic characteristics of the lungs - Characteristics of normal and abnormal ventilatory patterns **Mechanisms of Ventilation** - **Atmospheric Pressure (Barometric Pressure)**: the force exerted by air or any gas that surrounds the body - Measured using a mercury barometer - Typically 760 mmHg at sea level in Louisville, KY - Varies by 5 mmHg depending on weather conditions - Effects of Altitude on Atmospheric Pressure: - Decreases with increasing altitude - Example: 7,000 feet above sea level, atmospheric pressure is lower **Real-Life Example: Altitude Sickness** - Kara and Nate, YouTubers, rode bicycles across Colorado at high altitude - Nate\'s brother, from Nashville (sea level), joined them without acclimating to the higher altitude - He got very sick due to exertion and lack of acclimation **Understanding Altitude Sickness** - **Fraction of Inspired Oxygen (FiO2)**: the percentage of oxygen in the air we breathe (21% at sea level) - Oxygen percentage remains constant at 21% regardless of altitude - The problem is not a lack of oxygen, but rather a decrease in barometric pressure at higher altitudes **Note:** This study guide will continue with further discussions on the mechanisms of ventilation, elastic properties of the lungs and chest wall, and more.\#\# Barometric Pressure and Altitude 🏔️ **Effects of Altitude on Barometric Pressure** - At higher altitudes, barometric pressure decreases. - At lower altitudes, barometric pressure increases. **Altitude** **Barometric Pressure** -------------------- ------------------------- Sea Level (Mobile) 760 Mount Everest 250 Dead Sea 1000-1050 **Effects of Altitude on Air Molecules** - At higher altitudes, there are fewer air molecules available. - At lower altitudes, there are more air molecules available. - The percentage of air molecules remains the same (21%). **Breathing at Different Altitudes** - At higher altitudes, it is harder to breathe due to fewer air molecules. - At lower altitudes, it is easier to breathe due to more air molecules. **Respiratory Therapists and Altitude 🔬** - Respiratory therapists need to consider altitude when operating ventilators. - In-flight ventilator operations require knowledge of altitude changes. **Primary Principle of Ventilation 💡** - Ventilation operates on the principle of **pressure gradient**. - **Pressure gradient** refers to a change in pressure. *\"Gas always moves down its pressure gradient, meaning it travels from an area of high pressure to an area of low pressure.\"* **Mechanisms of Pulmonary Ventilation** - **Intrapleural pressure** is the pressure inside the thoracic cavity or pleural cavity. - Intrapleural pressures drive ventilation. **Inspiration and Expiration ⚖️** **Inspiration** - Begins when atmospheric pressure is higher than intrapleural pressure. - Diaphragm drops, increasing intrathoracic space and decreasing intrapleural pressure. - Gas flows into the lungs due to the pressure gradient. **Expiration** - Occurs when intrapleural pressure is higher than atmospheric pressure. - Diaphragm raises, decreasing intrathoracic space and increasing intrapleural pressure. - Gas flows out of the lungs due to the pressure gradient. **Diaphragm and Breathing 💪** - The diaphragm is a muscle that contracts and relaxes to facilitate breathing. - The diaphragm\'s movement changes intrathoracic pressure, driving inspiration and expiration. **Boyle\'s Law ⚖️** - **Volume of gas varies inversely proportional to its pressure at a constant temperature.** - Two key points: - Gas always flows from an area of high pressure to low pressure. - There is no gas movement when the pressure gradient is 0.\#\# 🌡️ Pressure and Volume Relationship **Inverse Proportionality** As pressure goes up, volume goes down, and vice versa. This can be illustrated using a syringe: - Pushing the plunger in increases pressure and decreases volume - Pulling the plunger back decreases pressure and increases volume **Equilibrium** At the end of expiration, there is no gas movement when the pressure gradient is 0. This is because the lungs are at equilibrium, with no net movement of gas. **👅 Thoracic Cavity and Diaphragm** **Diaphragm Contraction and Relaxation** The thoracic cavity increases in size as a result of the downward contraction of the diaphragm. This leads to: - Decreased pressure inside the lungs - Air flowing in When the diaphragm relaxes and the thoracic cavity decreases in size: - Pressure inside the lungs increases - Air flows out **Pictures and Diagrams** The pictures and diagrams represent the diaphragm and its effect on intrapleural pressure. When the diaphragm drops: - Intrapleural pressure decreases - Air flows in When the diaphragm raises: - Intrapleural pressure increases - Air flows out **👶 Clinical Application: Breathing and Respiratory Stress** **Accessory Muscles and Retractions** Accessory muscles are used when breathing is difficult, such as in respiratory distress syndrome. Retractions are inward movements of the tissue, often seen in newborns with stiff lungs. *\"Anytime we see accessory muscle use or retractions, it means one very important thing: the patient is having to work hard to breathe.\"* **Work of Breathing** When the work of breathing increases, the patient may use accessory muscles, leading to fatigue. The respiratory therapist must be aware of any respiratory disorder that increases the work of breathing. **CO2-driven Breathing** We are all driven by our CO2 levels. If CO2 levels get too high, it forces us to breathe faster and harder. **🚨 Warning Signs: Intercostal Retractions** Intercostal retractions are a warning sign of severe respiratory stress, especially in newborns with stiff lungs. They are often hard to see in obese patients due to extra tissue covering the chest. **When to Observe Retractions** Retractions are observed during inspiration, when the patient is trying to take in a breath. **📊 Pressure Concepts** **Driving Pressure** Driving pressure is the pressure difference between two points in a tube or vessel. It is the amount of force moving gas or fluid through the tube or vessel. **Point** **Pressure** ----------- -------------- A 20 B 5 Driving pressure = 20 - 5 = 15 **Trans Airways Pressure and Transthoracic Pressure** Trans airway pressure (or trans respiratory pressure) is the pressure difference between the airway opening and the alveoli. Transthoracic pressure is the pressure difference between the alveolar space and the body\'s surface. It is responsible for expanding the lungs and chest wall in tandem. **Term** **Definition** ------------------------ ---------------------------------------------------------------- Trans airway pressure Pressure difference between airway opening and alveoli Transthoracic pressure Pressure difference between alveolar space and body\'s surface The term **body surface** refers to the little skin. **Respiratory Pressures** There are three important respiratory pressures to know: - **Transpulmonary Pressure**: the pressure difference between the alveolar space and the pleural cavity. *\"The difference between those two.\"* - **Transmural Pressure**: the pressure difference that occurs across the airway wall. - **TransThoracic Pressure**: the pressure difference between the inside of the thoracic cage and the outside of the thoracic cage. **Clinical Application: Flail Chest 🏥** A patient presents with a serious chest injury, including broken ribs, and is unable to breathe properly. The respiratory therapist must be aware of how the negative intrapleural pressure, transpulmonary pressure, and transthoracic pressure affect the patient\'s ability to breathe when the chest wall is unstable. **Flail Chest Definition** *A condition where the broken ribs move inward during inhalation and outward during exhalation, instead of expanding outward during inhalation and inward during exhalation.* **Characteristics of Flail Chest** - Chest wall moves inward during inhalation and outward during exhalation - Breathing is paradoxical (out of sync) - Can also be called **seesaw breathing**, as one side of the chest does the opposite of what the other side does **Treatment of Flail Chest** - Patient must be placed on **positive pressure ventilation** to correct the problem - Positive pressure ventilation eliminates the negative intrapleural pressure changes during each inspiration, stopping the adverse effects of the transpulmonary and transthoracic pressure gradients during inspiration **Complications of Flail Chest** - **Pneumothorax**: air in the pleural cavity - **Subcutaneous Emphysema**: presence of air in the subcutaneous tissue **Subcutaneous Emphysema** *\"Feels like bubble wrap\" - air absorbed into the skin, often benign and unnoticed until detected by a stethoscope.* **Term** **Definition** ------------------------ --------------------------------------------------------------------------- Pneumothorax Air in the pleural cavity Subcutaneous Emphysema Presence of air in the subcutaneous tissue Flail Chest Broken ribs moving inward during inhalation and outward during exhalation Seesaw Breathing One side of the chest doing the opposite of what the other side is doing Paradoxical Breathing Breathing that is out of sync Subcutaneous emphysema is a benign condition where air escapes into the interstitial spaces of the skin. It can cause a \"pop, crackle\" sound in the ears and can be felt by rubbing fingers over the affected area. In severe cases, a chest tube may be required, but it does not cause stress or pain. **Elastic Properties of the Lungs and Chest Wall 💪** Both the lungs and chest wall have elastic properties that work together in harmony. The chest wall has a natural tendency to expand, while the lungs have a natural tendency to shrink. **Lung Compliance** Lung compliance is the change in lung volume per unit pressure change. In simpler terms, it is how readily the elastic force of the lungs accepts a volume of gas. *\"Lung compliance is how readily the elastic force of the lungs will accept a volume of gas.\"* High compliance means the lungs are more pliable and have lower elastic recoil. This is similar to a balloon that has been blown up many times - it is very stretchy and easily accepts gas. Low compliance means the lungs are stiff and have high elastic recoil. This is similar to a new balloon that is hard to blow up and has a lot of elasticity. **Compliance** **Description** ---------------- ------------------------------------------------------------- High Lungs are pliable, low elastic recoil Low Lungs have high elastic recoil, are stiff and non-compliant **Diseases Associated with High and Low Compliance** **High Compliance** - COPD (Chronic Obstructive Pulmonary Disease), specifically emphysema - Air trapping leads to stretched out lungs, which can cause barrel chesting **Low Compliance** - Asthma - COVID - ARDS - Pneumonia - Fibrosis (e.g. black lung, mesothelioma, sarcoidosis) - Atelectasis (collapsed areas of lung) **Key Concepts** - **Compliance** and **elasticity** are opposite concepts. If compliance is high, elasticity is low, and if compliance is low, elasticity is high. - High compliance means lungs are stretchy and have low elastic recoil, while low compliance means lungs are stiff and have high elastic recoil.\#\# 😊 Compliancy in Lungs **Static Compliance** - static: lungs are still, not in movement - measured using equations ***Definition:** The amount of pressure applied to small airways and alveoli, measured by doing an inspiratory hold or pause.* **Dynamic Compliance** - dynamic: lungs in movement, moving in and out - measured using equations ***Definition:** The change in lung volume per unit change in pressure during inhalation.* **Key Terms** **Term** **Definition** --------------------------------------------- ----------------------------------------------------------------------------------------------- **Tidal Volume (Vt)** Amount of gas in one breath **Plateau Pressure** Pressure applied to small airways and alveoli, measured by doing an inspiratory hold or pause **PEEP (Positive End-Expiratory Pressure)** Pressure in the lungs that exists at the end of expiration **Peak Inspiratory Pressure (PIP)** Highest level of pressure during inhalation **Calculating Compliance** - **Static Compliance:** VT / (Plateau - PEEP) - **Dynamic Compliance:** VT / (PIP - PEEP) **Important Note** *The higher the volume and the higher the amount of pressure that we force into a patient\'s lungs, the lower their compliance will be.* **Low Tidal Volume Ventilation Strategy** - Use low tidal volumes (e.g. 250-300) and high rates to protect patients with compliance issues. - This strategy helps to minimize further damage to the lungs.\#\# Ventilation Mechanics 🌡️ **Compliance and Volume Pressure Curve** - **Compliance**: the ability of the lungs to expand and accept air - **Volume Pressure Curve**: a graph that shows the relationship between the pressure applied to the lungs and the resulting volume of air in the lungs Normal lungs: - Normal amounts of pressure → normal volume change - Typically, around 4-5 liters of volume change High compliant lungs (e.g. emphysema, COPD): - Increasing pressure → rapid increase in volume - Volume change: almost 6 liters Low compliant lungs (e.g. pneumonia, COVID-19): - Increasing pressure → decreased volume change - Volume change: significantly decreased (e.g. half of normal) **Effects of Low Compliance on Ventilation** - Low oxygen levels - Decreased chest rise - Decreased aeration on chest x-ray (more white, less black) **Functional Residual Capacity (FRC)** *\"when the lung and chest wall recoil to a resting volume\"* Any disruption to the normal lung-chest wall relationship can affect compliance. **Causes of Decreased Compliance** - Pneumonia - Atelectasis - ARDs - Pulmonary fibrosis - Anything that decreases compliance and increases elasticity (stiffness) of the lungs **Hooke\'s Law** *\"the strain of an elastic object is proportional to the stress\"* Example: stretching an elastic band with weights - Adding weights → stretching the band - Increasing weight → more stretching, but eventually breaks **Applying Positive Pressure Ventilation** - Be careful not to cause irreversible damage to patient\'s lungs, especially in smaller populations (preemies, newborns, infants) - Monitor pressure and volume closely, especially when using ventilators - Breathing treatments typically use 6-8 liters of gas, which only affects nebulization, not lung volume **Respiratory Ventilation Mistakes** - Forcing too much gas into patient\'s lungs can cause damage or death - Make sure to advocate for patients and question physician orders if necessary - Two protections: physician\'s orders and respiratory therapist\'s expertise\#\# Hazards of Positive Pressure 🚨 The hazards of positive pressure can be seen in the illustration of a right-sided tension pneumothorax. **Clinical Signs and Symptoms** - **Tachycardia** (increased heart rate) - **Diminished or absent breath sounds** on the affected side - **Apnea** - **Tracheal shift** away from the affected side - Decreased cardiac output and blood pressure **Surface Tension 🌊** Surface tension is a force that causes the molecules on the surface of a liquid to be pushed together, forming a layer. *\"Surface tension is the force that causes the molecules on the surface of a liquid to be pushed together to form a layer.\"* **Laplace\'s Law 📏** There are two main facts about Laplace\'s law to take away: - **Higher surface tension** requires higher pressure to inflate - **Smaller radius** increases pressure, while **larger radius** decreases pressure This can be seen in the thoracic cage, where an increase in size (radius) results in a decrease in pressure. **Surfactant 💧** Surfactant is a lubricant that helps to reduce surface tension. *\"Surfactant is like a lubricant. It\'s the layer of the liquid surface layer that helps to keep it open.\"* The more surfactant, the less tension. This reduces the amount of pressure required to open the alveoli. **Importance of Surfactant** Surfactant helps to: - Prevent gas from displacing in other parts of the lungs - Prevent collapse of airways - Make breathing easier and ventilation possible with smaller amounts of pressure **Pulmonary Surfactant 👍** Pulmonary surfactant is produced and stored in **alveolar type 2 cells**. **Composition** **Percentage** ----------------- ---------------- Phospholipids 90% Protein 10% The sole responsibility of pulmonary surfactant is to **lower alveolar surface tension**, making it easier to inflate the lungs.\#\# Surfactant and Its Importance in the Lungs 🌟 Surfactant is a chemical that lowers surface tension in the alveoli, increasing compliance and reducing the work of breathing. It is found in the pulmonary surface and plays a critical role in lung function. **Physiological Advantages** - **Surface Tension Reduction**: Surfactant lowers surface tension in the alveoli, increasing compliance and reducing the work of breathing. **Cause** **Description** ----------------------------------- --------------------------------------------------------------------------------------------------- **Birth Prematurity** Babies born prematurely may not have fully developed surfactant, leading to respiratory distress. **Acidosis** High levels of carbon dioxide in the blood can lead to a decrease in surfactant. **Hypoxia** Low oxygen levels in the tissues can cause a decrease in surfactant. **Atelectasis** Collapse of the alveoli can lead to a decrease in surfactant. **Pulmonary Vascular Congestion** Congestion in the blood vessels of the lungs can lead to a decrease in surfactant. - **Adulal Stability**: Surfactant helps to prevent smaller alveoli from collapsing and emptying into larger ones. - **Alveoli Dryness**: Surfactant helps to keep the alveoli dry, which is important for proper gas exchange. **Decreased Surfactant: Causes and Consequences** A decrease in surfactant can lead to: - **Pulmonary Edema**: Fluid is sucked into the alveoli from the capillaries, leading to difficulty breathing. - **Difficult Breathing**: Decreased surfactant makes it harder for the lungs to expand, leading to difficulty breathing. **Surfactant Deficiency Causes** **Other Related Concepts** - **Dipalmitoyl phosphatidylcholine (DPPC)**: A tension-lowering chemical found in surfactants. - **Lasix**: A medication used to treat pulmonary edema by increasing urine production. - **ARDS (acute respiratory distress syndrome)**: A condition characterized by inflammation and injury to the lungs, leading to respiratory failure. - **RDS (respiratory distress syndrome)**: A condition seen in premature infants, characterized by respiratory distress and lack of surfactant. - **Pulmonary Embolism**: A blood clot in the lungs. - **Pneumonia**: An infection of the lungs. - **Pulmonary Lavage**: A medical procedure in which saline is used to lavage the lungs, which can wash away surfactant.\#\# Respiratory Distress 😷 **Drowning** Drowning is a condition where a person inhales water into their lungs, leading to a decrease in surfactant levels. This can cause: - Decreased compliancy (ability of the lungs to expand) - Massive amounts of infection In cases of drowning, it is essential to consider what the victim has inhaled into their lungs, as this can lead to anoxic brain injury (lack of oxygen in the brain). **Anoxic Brain Injury** *An anoxic brain injury occurs when the brain does not receive sufficient oxygen, leading to tissue damage and potentially death.* **Extracorporeal Oxygenation (ECMO) 💻** ECMO is a medical procedure that: - Removes blood from the body - Oxygenates it - Returns it to the body This process eliminates the need for the lungs to oxygenate the blood. ECMO is used in cases where the patient\'s heart or lungs are not functioning properly, such as: - Heart bypass or lung bypass patients - COVID-19 patients with severe ARDS (Acute Respiratory Distress Syndrome) - Babies with congenital heart defects **Effects of ECMO on Pulmonary Surfactant** **Condition** **Effect on Pulmonary Surfactant** --------------- ------------------------------------ ECMO Decreased pulmonary surfactant **Clinical Connection: Baby with Respiratory Distress 👶** A baby born at 26 weeks was given surfactant through a bowtie valve to treat respiratory distress. The results: - Before surfactant: white, fluid-filled lungs - 3 hours after surfactant: significantly improved lung function **Surfactant Dosage** - Maximum of 3 doses of surfactant can be given - Evidence suggests that if surfactant is not effective after 3 doses, it is unlikely to work - Dosages can be given consecutively, usually with a wait time of hours or days between doses.