8 Pathophysiology Advance Preparation Student Readiness

8 Pathophysiology Advance Preparation Student Readiness
Assign the associated section of MyBRADYLab and review student scores. Review the chapter material in the Instructor Resources, which includes Student Handouts, PowerPoint slides, and the MyTest Program. This chapter focuses on disturbances that interrupt the continuous delivery of oxygen and nutrients necessary for cell metabolism and the removal of wastes produced from cell metabolism. Prepare Consider asking a respiratory therapist to guest speak on this topic. Bring a box of drinking straws to class to demonstrate the concept of dead air space. Plan 165 to 180 minutes for this class as follows: Cellular Metabolism: 45 minutes Describes the process by which cells produce energy, the role of oxygen in the process, and the consequences to cellular metabolism of hypoxia Components Necessary for Adequate Perfusion: 120 minutes Explains how the respiratory and circulatory systems work together to maintain a constant supply of oxygen and glucose to the body's cells Discusses mechanisms by which perfusion can be impaired The total teaching time recommended is only a guideline. Take into consideration factors such as the pace at which students learn, the size of the class, breaks, and classroom activities. The actual time devoted to teaching objectives is the responsibility of the instructor.

Learning Readiness EMS Education Standards, text p. 164
Explain to students what the National EMS Education Standards are. The National EMS Education Standards communicate the expectations of entry-level EMS providers. As EMTs, students will be expected to be competent in these areas. Acknowledge that the Standards are broad, general statements. Although this lesson addresses the listed competencies, the competencies are often complex and require completion of more than one lesson to accomplish.

Learning Readiness Objectives
Please refer to page 164 of your text to view the objectives for this chapter. Objectives are more specific statements of what students should be able to do after completing all reading and activities related to a specific chapter. Remind students they are responsible for the learning objectives and key terms for this chapter.

Learning Readiness Key Terms
Please refer to pages 164 and 165 of your text to view the key terms for this chapter. Assess and reinforce the objectives and key terms using quizzes, handouts from the electronic instructor resources, and workbook pages.

Setting the Stage Overview of Lesson Topics Cellular Metabolism
Components Necessary for Adequate Perfusion

Case Study Introduction
EMTs Patty Mirabal and Gus Oakes are on the scene of a 52-year-old man who is complaining of difficulty breathing. The patient is breathing shallowly and rapidly. He gasps, "Need … help … can't … breathe." Case Study Present the Case Study Introduction provided in the PowerPoint slide set. Lead a discussion using the case study questions provided on the subsequent slide(s). The Case Study with discussion questions continues throughout the PowerPoint presentation. Refer to the Case Study Guide in the Instructor Resources for more information. Case Study Discussion Use the case study content and questions to foreshadow the upcoming lesson content

Case Study What purposes does breathing serve?
In what ways does a problem with breathing affect the body?

Introduction Oxygen and glucose are necessary for normal cell function. Illnesses and injuries can disturb the delivery of oxygen and glucose and removal of waste by-products. A fundamental purpose of emergency care is maintaining adequate delivery of oxygen and glucose. Introduction During this lesson, students will learn about processes that occur in the human body.

Cellular Metabolism Cellular metabolism is the process in which the body breaks down molecules of glucose to produce energy. Aerobic metabolism takes place when oxygen is available. When there is a lack of oxygen, the body uses a less effective process called anaerobic metabolism. continued on next slide

Cellular Metabolism Aerobic metabolism
The initial steps of cellular metabolism do not require oxygen, but produce only small amounts of energy. Oxygen is required to complete the process of extracting energy from glucose and removing the wastes produced by the process. continued on next slide

continued on next slide
Aerobic metabolism. Glucose broken down in the presence of oxygen produces a large amount of energy (ATP). continued on next slide

The initial steps of cell metabolism take place in the cytosol and are called glycolysis. Glycolysis produces a small amount of ATP. When oxygen is present, the process continues in the mitochondria, where larger amounts of ATP needed for cell function are produced. Points to Emphasize Cells must engage in metabolism to produce the energy needed by the cell to carry out its functions. When there is an adequate amount of oxygen available to the cell, it produces a greater amount of energy, and the body is able to convert waste products to forms that the body can then eliminate. Discussion Question Why do all cells of the body need oxygen? continued on next slide

Cellular Metabolism By-products of aerobic metabolism include heat, carbon dioxide, and water. Increased metabolism results in increased respiratory rate to eliminate the increased carbon dioxide. Heat and water can be used or eliminated by the body. continued on next slide

An important cell function that requires ATP is the sodium/potassium pump. continued on next slide

The sodium/potassium pump. Energy (ATP) is required to pump sodium molecules out of the cell against the concentration gradient. Potassium then moves with the gradient to flow into the cell. Sodium and potassium are exchanged in a continuous cycle that is necessary for proper cell function. The cycle continues as long as the cells produce energy through aerobic etabolism. When insufficient energy is produced, through anaerobic metabolism, the sodium/potassium pump will fail and cells will die. continued on next slide

Cellular Metabolism Sodium (Na+) is primarily found outside the cell.
Potassium (K+) is found primarily inside the cell. Without a functioning sodium/potassium pump, sodium that finds its way into the cell cannot exit and accumulates inside the cell. continued on next slide

Cellular Metabolism When the concentration of sodium in the cell is too high, potassium cannot enter and the cell cannot function. Excess sodium in the cell allows excess water to enter the cell. Excess water can cause the cell to swell, rupture, and die. continued on next slide

Cellular Metabolism In anaerobic metabolism, the combination of inadequate energy production and accumulating lactic acid result in failure of cell processes. continued on next slide

Anaerobic metabolism. Glucose broken down without the presence of oxygen produces pyruvic acid that converts to lactic acid and only a small amount of energy (ATP). continued on next slide

Cellular Metabolism Anaerobic metabolism
The first stage of cell metabolism is anaerobic. The waste product produced is pyruvic acid. Without oxygen, pyruvic acid is converted to lactic acid. Accumulation of lactic acid is harmful to body functions. Points to Emphasize Without adequate oxygen, much less energy is produced and waste products accumulate. The by-product of anaerobic metabolism is lactic acid. When lactic acid accumulates it disrupts the functions of the cell, leading to cell damage or death. The sodium-potassium pump of cells requires energy to keep the right amount of potassium inside the cell, and the right amount of sodium outside the cell. When too much sodium enters the cell, water follows the sodium through the cell membrane and causes the cell to swell, rupture, and die. Critical Thinking Discussion What are some reasons that cells might not receive the glucose they need for metabolism? Discussion Questions What are the consequences of inadequate oxygenation of the body's tissues? What causes cells to swell and burst if hypoxia continues? continued on next slide

Cellular Metabolism Anaerobic metabolism
In the presence of extensive anaerobic metabolism, cells die, which can lead to organ failure and death.

Adequate Perfusion Perfusion is the delivery of oxygen, glucose, and other substances to the cells and the elimination of waste products from the cells. continued on next slide

Adequate Perfusion Perfusion requires functioning nutrient/oxygen delivery and waste removal systems. continued on next slide

Adequate Perfusion 11 components of these systems are:
Composition of ambient air Patent airway Mechanics of ventilation Regulation of ventilation Ventilation/perfusion ratio Transport of oxygen and carbon dioxide by the blood continued on next slide

Adequate Perfusion 11 components of these systems are: Blood volume
Pump function of the myocardium Systemic vascular resistance Microcirculation Blood pressure Points to Emphasize Perfusion is the delivery of oxygen, glucose, and other substances to the cells and the elimination of waste products from the cells. Adequate perfusion requires oxygen from the atmosphere, an open airway, movement of air into and out of the lungs, adequate circulation to the lungs, transport of gases in the blood, and adequate circulation to the cellular level. Any condition that interferes with any of the components needed for adequate perfusion can result in anaerobic metabolism. The decreased energy available and the accumulation of lactic acid in the absence of oxygen will lead to cell death, organ death, and death of the patient if adequate perfusion is not quickly restored. A decrease in the amount of oxygen available in the patient's environment results in hypoxia. Providing supplemental oxygen can increase the amount of oxygen reaching the cells. Critical Thinking Discussion What are some reasons that cells might not receive an adequate amount of oxygen? continued on next slide

Adequate Perfusion Any alteration in the components may lead to poor cellular perfusion. Inadequate perfusion can shift cells from aerobic to anaerobic metabolism. In anaerobic metabolism, production of energy is reduced and harmful by-products accumulate. Emergency care focuses on restoring and maintaining the components.

Case Study Gus quickly moves next to the patient to better assess his condition, while Patty unzips the airway kit and begins to select equipment to begin patient care. continued on next slide

Case Study What, specifically, will Gus be assessing to determine the patient's condition? How will Patty know what equipment and treatment the patient needs? What is happening to the patient at the cellular level? What will happen if the EMTs do not intervene quickly?

Composition of Ambient Air
The concentration of oxygen in the ambient air determines the amount of oxygen that ends up in the alveoli for gas exchange. Ambient air contains approximately 79% nitrogen, 21% oxygen, and trace amounts of argon and carbon dioxide. continued on next slide

Table 8-1 Partial Pressure of Gases in Ambient Atmosphere at Sea Level
continued on next slide

FiO2 is the fraction of inspired oxygen. A patient breathing air that contains 21 percent oxygen has an FiO2 of 0.21. One way to improve cellular oxygenation to increase the patient's FiO2 by administering supplemental oxygen. continued on next slide

Some toxic gases displace the amount of oxygen in the air, which suffocates the patient. Carbon monoxide disrupts the ability of the blood to carry oxygen to the cells. Cyanide interferes with oxygen use by the cell. Each of these situations leads to hypoxia.

Patent Airway A patent airway is open and not obstructed by any substance. Establishing an open airway is one of the first steps in emergency care. Failure to establish or maintain a patent airway leads to cellular hypoxia and patient death. continued on next slide

Airway obstruction can occur at several levels of the upper and lower airway, including the nasopharynx, oropharynx, posterior pharynx, epiglottis, larynx, trachea, and bronchi.

Patent Airway Airway obstruction can occur at several levels and has many causes. Obstruction of nasopharynx, oropharynx, or pharynx Swelling of epiglottis Laryngeal spasm or edema Obstruction of trachea or bronchi

Mechanics of Ventilation
An intact thoracic cavity is integral to normal ventilation. Thoracic cavity boundaries Mediastinum Parietal and visceral pleura continued on next slide

Boyle's law The volume of a gas is inversely proportional to the pressure. Increasing and decreasing the volume of the thoracic cavity changes the pressure of air inside it. continued on next slide

Boyle's law Contracting the diaphragm and intercostal muscles increases the thoracic volume, creating negative pressure. The negative pressure causes the pleura and lungs within the thorax to expand, creating negative pressure within the lungs. Points to Emphasize The thoracic cavity must be intact to produce the changes in pressure needed for air to move in and out of the lungs. Air moves from areas of higher pressure to areas of lower pressure. As the size of the thorax increases, the pressure within it decreases, causing air to flow into the lungs. When the thorax relaxes and decreases in volume, the pressure within it becomes higher and air flows out of the lungs. An increase in airway resistance or decrease in lung compliance can interfere with ventilation. Minute volume (ventilation) is the respiratory rate multiplied by the volume of air moved in and out of the lungs with each breath. An average tidal volume 0f 500 mL and a respiratory rate of 12 per minute produces a minute volume of 6 L/minute. Any change in tidal volume or respiratory rate will change the minute volume. We refer to the volume of the airway above the alveoli as dead air space. With a tidal volume of 500 mL, only about 350 mL are available to the alveoli. continued on next slide

Boyle's law The pressure of atmospheric air is 760 mmHg at sea level. Just prior to inhalation, the pressure within the chest is 758 mmHg. Air flows from the higher pressure of the atmosphere toward the lower pressure of the lungs. Discussion Questions How do patients compensate for a condition that decreases tidal volume? If a patient's tidal volume is 300 mL and his respiratory rate is 20, what is the alveolar ventilation? Is this adequate or not? Critical Thinking Discussion Will applying oxygen by nonrebreather mask improve tidal volume? Why or why not? continued on next slide

Boyle's law On exhalation, the diaphragm and intercostal muscles relax. The volume of the thorax and lungs decreases. Pressure inside the chest rises to 761 mmHg. Air flows from the higher pressure in the lungs to the lower pressure of the atmosphere. Teaching Tips Give several examples of how changing the tidal volume and respiratory rate change the minute volume. Knowledge Application Given several scenarios including a patient's respiratory rate and tidal volume, determine if the patient's alveolar ventilation is likely to be adequate or inadequate. Ask students to breathe normally through a drinking straw to demonstrate the effect of dead air space on alveolar ventilation. continued on next slide

Click on the event that occurs just prior to the movement of air into the lungs on inhalation.
A. The diaphragm relaxes. B. The size of the chest cavity decreases. C. Pressure within the chest decreases. D. The intercostal muscles relax. continued on next slide

Accessory muscles Used when extra effort is needed for inhalation or exhalation Increases energy use If energy production fails from insufficient oxygen, the muscles of respiration fail. continued on next slide

Table 8-2 Accessory Muscles

Compliance and airway resistance High resistance and low compliance increase the effort needed to breathe and lead to hypoxia. continued on next slide

Compliance and airway resistance Compliance is the ease with which the lungs or chest wall expand. Pneumonia, pulmonary edema, and some chest injuries can decrease compliance. continued on next slide

Compliance and airway resistance Resistance is the ease of airflow into and out of the airway structures. Edema of the airway and constriction of the bronchioles can lead to increased airway resistance. continued on next slide

Pleural space Negative pressure is maintained in the pleural space. An injury to the chest wall or lung that opens the space can draw air, by way of negative pressure, into the space. The lung may collapse from the air accumulation. continued on next slide

Minute ventilation, or minute volume, is the amount of air moved in and out of the lungs in one minute. Minute volume = tidal volume × frequency of ventilation continued on next slide

Average minute volume is: 500 mL × 12/minute = 6,000 mL (6 L) continued on next slide

A decrease in tidal volume decreases the minute volume. A decrease in respiratory rate decreases the minute volume. A decrease in minute volume reduces the air available for gas exchange in the alveoli. continued on next slide

A decrease in minute ventilation can lead to cellular hypoxia. To ensure adequate ventilation, both the tidal volume and respiratory rate must be adequate. continued on next slide

An increase in ventilatory rate can compensate for reduced tidal volume in maintaining minute volume, to a point. With low tidal volume, the volume of air may not be sufficient to reach the alveoli for gas exchange. continued on next slide

Alveolar ventilation is the amount of air moved in and out of the alveoli in one minute. Air that does not reach the alveoli, remaining in the trachea and bronchi, is called dead space air. 150 mL of a 500 mL tidal volume remains in the dead air space; 350 mL reaches the alveoli. continued on next slide

Alveolar ventilation = (tidal volume – dead air space) × frequency of ventilation/minute continued on next slide

Dead air spaces fill first with ventilation. If tidal volume decreases, alveolar volume decreases. An increase in ventilation rate does not mean more air volume is reaching the alveoli. continued on next slide

Providing oxygen alone to a patient with poor tidal volume does not correct hypoxia. The patient needs assisted ventilation to increase tidal volume. continued on next slide

Hypoxia can occur from: A low tidal volume A slow ventilatory rate A fast ventilatory rate continued on next slide

When the ventilatory rate is too fast There is inadequate time between breaths to fill the lungs. A very fast rate requires a large amount of energy that may not be able to be sustained, setting up the patient for respiratory failure. continued on next slide

When the ventilatory rate is too fast Ventilatory rates of 40/minute or greater in the adult patient and greater than 60/minute in the pediatric patient are too fast to be sustainable or to allow adequate time for a normal tidal volume.

Regulation of Ventilation
Breathing is an involuntary process controlled by the autonomic nervous system. Receptors measure oxygen (O2), carbon dioxide (CO2), and hydrogen ions (pH). Receptors send signals to the brain to adjust the rate and depth of respiration. continued on next slide

Respiration is controlled by the autonomic nervous system. Receptors within the body measure oxygen, carbon dioxide, and hydrogen ions and send signals to the brain to adjust the rate and depth of respiration. continued on next slide

Chemoreceptors are specialized receptors that monitor the pH, CO2, and O2 levels in arterial blood. There are central chemoreceptors and peripheral chemoreceptors. Points to Emphasize Chemoreceptors detect pH and the levels of oxygen and carbon dioxide in the blood and cerebral spinal fluid and stimulate the respiratory center to adjust ventilation to maintain normal levels. There is a direct relationship between the level of carbon dioxide in the blood and the amount of acids present as measured by pH. The primary stimulus to breathe is an increased level of carbion dioxide in the blood. Three groups of neurons in the brainstem (dorsal respiratory group, ventral respiratory group, and the pontine respiratory (pneumotaxic) center) control the depth and pattern of respiration. Discussion Question How can an injury to the brain interfere with perfusion? continued on next slide

Central chemoreceptors are located near the respiratory center in the medulla. Sensitive to CO2 and changes in the pH of the cerebrospinal fluid (CSF) The pH in CSF reflects the CO2 level of arterial blood. The more CO2 in the blood, the greater the amount of acid continued on next slide

Small changes in pH stimulate a response in the rate and depth of breathing. Faster, deeper breathing eliminates more CO2. Slower, shallower breathing eliminates less CO2. continued on next slide

Peripheral chemoreceptors are located in the aortic arch and the carotid bodies. As O2 in the blood decreases, peripheral chemoreceptors signal the respiratory center in the brainstem to increase the rate and depth of respiration. continued on next slide

A significant decrease in the arterial oxygen content causes an increase in the rate and depth of respiration. continued on next slide

Normally, rate and depth of breathing are regulated by the amount of CO2 in the blood. continued on next slide

COPD patients have a tendency to retain CO2 They become insensitive to small changes in CO2. Their respirations are controlled by decreased oxygen levels; this is called the hypoxic drive. continued on next slide

Three types of receptors within the lungs provide impulses to regulate respiration. Irritant receptors Stretch receptors J-receptors continued on next slide

Irritant receptors Found in the airways Sensitive to irritating gases, aerosols, and particles Simulate coughing, bronchoconstriction, and increased ventilatory rate continued on next slide

Stretch receptors Found in the smooth muscle of the airways Protect against over inflation of the lungs continued on next slide

Stretch receptors Measure the size and volume of the lungs Stimulate a decrease in the rate and volume of ventilation when stretched by high tidal volumes continued on next slide

J-receptors Found in the capillaries surrounding the alveoli Sensitive to increases in capillary When activated, they stimulate rapid, shallow ventilation continued on next slide

Respiratory control centers in the brainstem Dorsal respiratory group (DRG) Ventral respiratory group (VRG) Pontine respiratory center (pneumotaxic center) continued on next slide

Ventral respiratory group Located in medulla oblongata Receives sensory input and sends it to the spinal cord to stimulate the diaphragm and intercostal muscles Contains inspiratory and expiratory neurons Controls basic pattern of breathing continued on next slide

Dorsal respiratory group Located in medulla oblongata Receives sensory input and communicates it to the VRG for further input on rate and depth of breathing continued on next slide

Pontine respiratory center Sends inhibitory impulses to the inspiratory neurons of the VRG to turn off the inhalation Promotes a smooth transition between inhalation and exhalation continued on next slide

Illness or injury can disrupt the respiratory centers in the brainstem. Pattern and depth of ventilation can be affected. Gas exchange may be inadequate; cellular hypoxia may result.

Case Study The patient is working hard to breathe, and has pale, moist skin. He is using accessory muscles to breathe, but seems to be moving very little air. The patient seems on the verge of complete exhaustion, and appears sleepy. Patty selects a bag-mask device to assist the patient's ventilations, and connects it to supplemental oxygen. continued on next slide

Case Study What medical problems could lead a patient to have such severe difficulty breathing?

Ventilation/Perfusion (V/Q) Ratio
V/Q ratio is the relationship between alveolar ventilation and perfusion of the alveolar capillaries. The relationship influences gas exchange. Can be used to explain causes of hypoxemia continued on next slide

Overview of ventilation and perfusion.

Ventilation/Perfusion Ratio
In an ideal state the amount of ventilation is equally matched to the amount of perfusion. Physiologically, based on gravity and the nature and distribution of alveoli in the lungs, a perfect match does not occur. Overall, perfusion exceeds ventilation, but the situation is highly functional. continued on next slide

When ventilation is better than perfusion, there is wasted ventilation. When perfusion is better than ventilation, there is wasted perfusion. continued on next slide

Pressure imbalance If the air pressure in an alveolus exceeds the blood pressure in the capillary bed, blood flow through the capillary stops. Occurs normally in the apex of the lungs Occurs when the systemic blood pressure decreases continued on next slide

Possible causes of ventilation disturbances.

Ventilatory disturbances A condition that decreases the amount of air reaching the alveoli, such as asthma, results in wasted perfusion. Hypoxemia and hypoxia result. Treatment is aimed at increasing lung ventilation. Points to Emphasize Ventilation/perfusion ratio is the match between the amount of air entering the alveoli and amount of blood circulating to the alveoli for gas exchange. A ventilation/perfusion mismatch leads to decreased gas exchange between the alveoli and alveolar capillaries. Respiratory gases move from areas of high concentration to areas of low concentration. Discussion Question What is the concept of the ventilation/perfusion ratio? Critical Thinking Discussion A patient takes a drug that prevents the heart rate from increasing. What are the consequences if the patient loses a large quantity of blood? continued on next slide

Perfusion disturbances Ventilation is normal, or even increased, but blood flow through the lungs is decreased. There is wasted ventilation, leading to hypoxemia and hypoxia. Administering oxygen may help, but the perfusion disturbance must be corrected. continued on next slide

Various conditions lead to V/Q mismatch and resultant hypoxia. Treatment is aimed at improving ventilation, oxygenation, and perfusion to the lungs.

Gas Transport Oxygen must be continuously delivered by the blood to the cells for normal cellular metabolism. Carbon dioxide must be carried back to the lungs to be blown off in exhalation. A disturbance in the transport system may lead to cellular hypoxia and hypercarbia. continued on next slide

Gas Transport Gases move from areas of higher concentration to areas of lower concentration. continued on next slide

Gas Transport Oxygen Transport
1,000 mL of O2 are delivered to the cells every minute. O2 is transported in the blood in two ways. 1.5 to 3% is dissolved in plasma. 97 to 98.5% is attached to hemoglobin molecules. continued on next slide

Oxygen is transported in the blood two ways: attached to hemoglobin and dissolved in plasma. Carbon dioxide is transported in the blood three ways: as bicarbonate, attached to hemoglobin, and dissolved in plasma. continued on next slide

Gas Transport Hemoglobin is a protein molecule that contains iron.
There are four iron sites per hemoglobin molecule for oxygen to bind to. Each molecule can carry up to four oxygen molecules. continued on next slide

Gas Transport If one oxygen molecule is attached to the hemoglobin molecule, it is 25% saturated; if four molecules are attached, it is 100% saturated. Attachment of one oxygen molecule to hemoglobin increases the affinity for the other sites to also bind with oxygen. Critical Thinking Discussion A blood clot obstructs blood flow through the pulmonary artery. Explain how this affects perfusion. Class Activity Perfusion biographies Assign students to play the role of various components of perfusion (red blood cells, right ventricle, and so on). Encourage students to select a name for their component, such as Larry the Left Ventricle. Students will spend five to ten minutes writing the biography of their component and will then present it to the class. continued on next slide

Gas Transport Hemoglobin to which oxygen is bound is called oxyhemoglobin. Hemoglobin with no oxygen attached is called deoxyhemoglobin. continued on next slide

Gas Transport Without hemoglobin, the blood cannot carry enough oxygen to sustain life. Loss of hemoglobin, such as through bleeding, can lead to cellular hypoxia, even though an adequate amount of oxygen is available in the alveoli. continued on next slide

Gas Transport Carbon dioxide is transported in the blood in three ways. 7% is dissolved in plasma. 23% is attached to hemoglobin in RBCs. 70% as bicarbonate. continued on next slide

Gas Transport The largest amount of CO2 diffuses from the cell, into the blood, and then into RBCs. In the RBC, CO2 combines with water to form carbonic acid, which then dissociates into hydrogen and bicarbonate. continued on next slide

Gas Transport Bicarbonate exits the RBC and is transported in plasma.
When blood reaches the lungs, bicarbonate diffuses back into RBCs, where it combines with hydrogen and then dissociates into water and CO2. CO2 diffuses from the blood into the alveoli and is released through exhalation. continued on next slide

Gas Transport Alveolar/capillary gas exchange
After inhalation, the alveolar air is high in O2 and low in CO2. Venous blood in the capillaries surrounding the alveoli is low in O2 and high in CO2. continued on next slide

Gas Transport Gas molecules move from areas of high concentration to areas of low concentration. O2 moves into the capillaries where the oxygen content is very low. Simultaneously, CO2 moves in the opposite direction. continued on next slide

Gas Transport Blood ejected from the left ventricle into the arteries is high in O2 and low in CO2. This blood travels into the capillaries in the tissues to reach the cells. continued on next slide

Gas Transport As a result of metabolism, cells are higher in CO2 and lower in O2. O2 leaves the blood and enters the cells; CO2 leaves the cells and enters the blood. continued on next slide

Click on the mechanism by which most of the oxygen in blood is transported.
A. Bound to hemoglobin B. In the form of bicarbonate C. Dissolved in plasma D. Carried by white blood cells

Blood Volume A determinant of blood pressure and perfusion is blood volume. Adults have 70 mL of blood/kg of body weight. A 70-kg adult has 4,900 mL (4.9 L) of blood. continued on next slide

Blood Volume Blood composition 45% formed elements 55% plasma
42% to 48% red blood cells White blood cells Platelets 55% plasma 91% water Plasma proteins Albumin, clotting factors, antibodies continued on next slide

Table 8-3 Distribution of Blood in the Cardiovascular System
Points to Emphasize Blood pressure must be adequate to deliver blood to the capillaries, where gases are exchanged between the blood and the cells. The movement of fluid between the capillaries and the interstitial spaces is affected by hydrostatic pressure and plasma oncotic pressure. Cardiac output depends on the amount of blood pumped from the left ventricle with each contraction and the number of times the ventricle contracts each minute. Hormones and the nervous system influence heart rate. Preload is the amount of blood in the left ventricle at the end of diastole. Afterload is the resistance to the aorta that the left ventricle must overcome to move blood forward. Baroreceptors are sensitive to the amount of stretch placed on them by the pressure of blood moving through the aorta and carotid sinuses. Blood pressure is determined by cardiac output and systemic vascular resistance. continued on next slide

Blood Volume Hydrostatic pressure is the force inside the vessel or capillary bed generated by the contraction of the heart and the blood pressure. Hydrostatic pressure exerts a "push" inside the vessel or capillary. High hydrostatic pressure promotes edema. continued on next slide

Hydrostatic pressure pushes water out of the capillary. Plasma oncotic pressure pulls water into the capillary. continued on next slide

Blood Volume In left heart failure, the ventricle does not empty completely, so it cannot receive the full amount of blood returning from the lungs. Blood backs up into the pulmonary circulation, resulting in increased hydrostatic pressure. continued on next slide

Blood Volume Fluid is forced out of the pulmonary capillaries, where it surrounds the alveoli and reduces gas exchange. continued on next slide

Blood Volume Plasma oncotic pressure keeps fluid inside the vessels to oppose hydrostatic pressure. The large plasma proteins have the effect of "pulling" water into the capillaries. continued on next slide

Blood Volume Hydrostatic and oncotic pressures must be balanced.
High hydrostatic pressure pushes fluid out of capillaries and promotes edema. Low hydrostatic pressure pushes less fluid out of the vessel. continued on next slide

Blood Volume Hydrostatic and oncotic pressures must be balanced.
High oncotic pressure draws excessive amounts of fluid into the capillary and promotes blood volume overload. Low oncotic pressure does not exert enough pull to counteract the push of hydrostatic pressure, promoting loss of vascular volume and edema.

Myocardial Function The myocardium must be an effective pump to maintain perfusion. Cardiac output (CO) is the amount of blood ejected from the heart in one minute. CO = heart rate × stroke volume continued on next slide

Myocardial Function Several factors affect the heart rate.
Sympathetic and parasympathetic nervous systems affect heart rate through the cardiovascular control system in the brain stem. The cardiovascular control center is composed of the cardioexcitatory center and the cardioinhibitory center. continued on next slide

Myocardial Function An increase sympathetic stimulation increases the heart rate. A decrease in sympathetic stimulation decreases the heart rate. An increase in parasympathetic stimulation decreases the heart rate. A decrease in parasympathetic stimulation increases the heart rate. Discussion Question What is meant by cardiac output? Teaching Tips Explain the similarities in the concepts of minute ventilation and cardiac output. Critical Thinking Discussion You've just been scared by a near collision as you are driving to class. Explain how your perfusion will be affected. continued on next slide

Myocardial Function Stroke volume is the amount of blood ejected from the heart with each contraction. Stroke volume is determined by preload, myocardial contractility, and afterload. Discussion Questions What are the effects of the sympathetic and parasympathetic nervous systems on cardiac output? How do changes in preload and afterload affect cardiac output? Knowledge Application Given several scenarios including a patient's stroke volume and heart rate, calculate the cardiac output. continued on next slide

Myocardial Function Preload
Preload pressure is created by the blood volume in the left ventricle at the end of diastole. The available venous volume plays a major role in determining preload. An increase in preload increases stroke volume, which increases the cardiac output. continued on next slide

Myocardial Function Frank-Starling law of the heart
As blood fills the left ventricle, it stretches the muscle fibers. The stretch of the muscle fiber determines the force available to eject the blood from the ventricle. There is a limit to the Frank-Starling law. continued on next slide

Myocardial Function Damage to the heart from heart failure or myocardial infarction can decrease the myocardial contractility, thereby decreasing stroke volume and cardiac output. continued on next slide

Myocardial Function Afterload is the resistance in the aorta that must be overcome by contraction of the left ventricle to eject the blood. High diastolic blood pressure creates high afterload, which increases myocardial workload. Over time, high afterload can lead to left ventricular failure. continued on next slide

Myocardial Function Factors that decrease cardiac output
Decreased heart rate Decreased blood volume Decreased myocardial contractility Parasympathetic nervous stimulation Beta1 blockade (beta blockers) Higher diastolic BP over time continued on next slide

Myocardial Function Factors that increase cardiac output
Increased heart rate (to a point) Increased blood volume Increased myocardial contractility Sympathetic nervous system stimulation Beta1 stimulation from epinephrine Lower diastolic BP

Systemic Vascular Resistance
SVR is the resistance to blood flow through a vessel. Vasoconstriction increases SVR, increased SVR increases BP. Vasodilation decreases SVR, decreased SVR decreases BP. continued on next slide

Sympathetic stimulation increases the SVR and BP. Epinephrine and norepinephrine stimulate alpha1 receptors, which cause vasoconstriction and increased SVR. Parasympathetic stimulation decreases SVR and BP. Knowledge Application Given several blood pressure values, determine the pulse pressure. Discussion Question What is the significance of a narrow pulse pressure? continued on next slide

If the volume of blood decreases, decreasing the vessel size to increase SVR can help maintain BP. Decreasing vessel size through vasoconstriction decreases cellular perfusion and increases anaerobic metabolism. Patients with anaerobic metabolism may have a poor general appearance. continued on next slide

SVR and pulse pressure Pulse pressure is the difference between the systolic and the diastolic BP readings. Systolic BP is an indicator of cardiac output. continued on next slide

SVR and pulse pressure Diastolic BP indicates systemic vascular resistance. Decreasing systolic BP indicates falling cardiac output. continued on next slide

SVR and pulse pressure A narrow pulse pressure is less than 25% of the systolic BP. With a BP of 132/74 mmHg, the pulse pressure is 58 mmHg (132 – 74 = 58). A narrow pulse pressure for that patient is 33 mmHg (132 × 25% = 33 mmHg). continued on next slide

SVR and pulse pressure In a patient with blood or fluid loss, narrow pulse pressure is a significant sign. Blood loss lowers venous volume, which lowers preload, which lowers stroke volume, which lowers cardiac output Systolic BP decreases from the drop in cardiac output. continued on next slide

SVR and pulse pressure In a patient with blood or fluid loss, narrow pulse pressure is a significant sign. Increased SVR increases diastolic BP. The result is a narrow pulse pressure.

Microcirculation Microcirculation is the flow of blood through the arterioles, capillaries, and venules. continued on next slide

Microcirculation is the flow of blood through the smallest blood vessels: arterioles, capillaries, and venules. Precapillary sphincters control the flow of blood through the capillaries. continued on next slide

Microcirculation Precapillary sphincters control the movement of blood through the capillaries. If the precapillary sphincter is relaxed, blood moves through the capillary. If the precapillary sphincter is contracted, the blood is shunted away from the true capillary. continued on next slide

Microcirculation Precapillary sphincters help to maintain arterial pressure. Three regulatory influences control blood flow through the capillaries. Local factors Neural factors Hormonal factors continued on next slide

Microcirculation Local factors Temperature Hypoxia Acidosis Histamine

Microcirculation Neural factors
Sympathetic nervous system causes vasoconstriction Parasympathetic nervous system causes vasodilation continued on next slide

Microcirculation Hormonal factors
Epinephrine stimulates alpha1 receptors, which cause precapillary sphincters to constrict.

Blood Pressure Blood pressure (BP) = cardiac output (CO) × systemic vascular resistance (SVR) Increased CO increases BP. Decreased CO decreases BP. Increased HR increases CO and BP. Decreased HR decreases CO and BP. continued on next slide

Blood Pressure Blood pressure (BP) = cardiac output (CO) × systemic vascular resistance (SVR) Increased SV increases CO and BP. Decreased SV decreases CO and BP. Increased SVR increases BP. Decreased SVR decreases BP. Critical Thinking Discussion How do the nervous, respiratory, and circulatory systems all have to work together to maintain adequate perfusion? continued on next slide

Blood Pressure The general effect of blood pressure on perfusion is:
Increased BP increases cellular perfusion Decreased BP decreases cellular perfusion continued on next slide

Blood Pressure BP is monitored and regulated by baroreceptors and chemoreceptors. Baroreceptors located in the aortic arch and carotid sinuses detect changes in blood pressure. Signals are sent to the vasomotor and cardioregulatory centers in the brainstem. continued on next slide

Blood Pressure An increase in BP results in signals to decrease the heart rate and dilate blood vessels. A decrease in BP results in signals to increase the heart rate and constrict blood vessels. continued on next slide

Blood Pressure Chemoreceptors
A decrease in blood oxygen level stimulates the sympathetic nervous system. Heart rate increases and blood vessels constrict. Hypoxia can present with pale, cool skin, and increased heart rate.

Review of Aerobic Metabolism Components
Oxygen content in ambient air Patency of the airway Minute ventilation Ventilatory rate Tidal volume Alveolar ventilation continued on next slide

Perfusion in the pulmonary capillaries Venous volume Right ventricular pump function Gas exchange between the capillaries and the alveoli continued on next slide

Content of blood Red blood cells Hemoglobin Plasma continued on next slide

Cardiac output Heart rate Preload Stroke volume Myocardial contractility Afterload continued on next slide

Systemic vascular resistance Sympathetic nervous system stimulation Parasympathetic nervous system stimulation Gas exchange between the capillaries and the cells

Case Study Conclusion The patient has a history of chronic obstructive lung disease and heart failure. He has been increasingly short of breath for two days, with a sudden worsening today. With the assistance of an engine crew, Patty and Gus continue assisting the patient's ventilations and providing supplemental oxygen. continued on next slide

Case Study Conclusion The crew recognizes the seriousness of the patient's condition and is prepared to take further measures, if needed, to maintain the patient's airway. Gus calls in a report to the receiving hospital. When they arrive at the ED, a physician, nurse, and respiratory therapist are waiting to continue the patient's care. Follow-Up Answer student questions. Case Study Follow-Up Review the case study from the beginning of the chapter. Remind students of some of the answers that were given to the discussion questions. Ask students if they would respond the same way after discussing the chapter material. Follow up with questions to determine why students would or would not change their answers. Follow-Up Assignments Review Chapter 8 Summary. Complete Chapter 8 In Review questions. Complete Chapter 8 Critical Thinking. Assessments Handouts Chapter 8 quiz

Lesson Summary Cells require oxygen and glucose to produce energy and perform work. Without adequate ventilation and perfusion, cells engage in anaerobic metabolism, which produces less energy and more waste. A fundamental purpose of emergency care is to restore and maintain cell perfusion. Class Activity As an alternative to assigning the follow-up exercises in the lesson plan as homework, assign each question to a small group of students for in-class discussion. Teaching Tips Answers to In Review questions are in the appendix of the text. Advise students to review the questions again as they study the chapter.

8 Pathophysiology Advance Preparation Student Readiness

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8 Pathophysiology Advance Preparation Student Readiness

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