Oxygenation and Perfusion PDF

Oxygenation and Perfusion Oxygen is necessary for normal metabolism and carbon dioxide is a waste product of this metabolism. The primary function of the respiratory system is gas exchange which consists of obtaining O2 from the atmosphere and removing CO2 from the blood. Air is taken in through the...

Oxygenation and Perfusion Oxygen is necessary for normal metabolism and carbon dioxide is a waste product of this metabolism. The primary function of the respiratory system is gas exchange which consists of obtaining O2 from the atmosphere and removing CO2 from the blood. Air is taken in through the upper airways, through the lower airways into the small bronchioles and alveoli within the lung tissue where gas exchange occurs. In this way, the respiratory tract primarily has the conduction of air zone and the respiratory zone. The diaphragm and other respiratory muscles within the chest wall play significant roles in ensuring air conduction into the lungs. Fatigue of the respiratory muscles can affect respiratory efforts. Physiology of Oxygenation Oxygenation-the delivery of oxygen to the body’s tissues and cells depends upon the interplay of the pulmonary, hematologic and cardiovascular systems. Three steps in the process of oxygenation are ventilation, perfusion, and diffusion. Ventilation is the process of moving gases into and out of the lungs. Perfusion relates to the ability of the cardiovascular system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs. Diffusion is responsible for moving the respiratory gases from one area to another by concentration gradients. For the exchange of respiratory gases to occur, the organs, nerves, and muscles of respiration need to be intact; and the central nervous system needs to be able to regulate the respiratory cycle. The exchange of respiratory gases occurs between the environment and the blood. Gases move into and out of the lungs through pressure changes. Intrapleural pressure is negative, or less than atmospheric pressure. For air to flow into the lungs, intrapleural pressure becomes more negative, setting up a pressure gradient between the atmosphere and the alveoli. During ventilation (external), the airways of the lung transfer oxygen from the atmosphere to the alveoli, where the oxygen is exchanged for carbon dioxide. Through the alveolar capillary membrane, oxygen transfers to the blood. In oxygen transport and delivery, at the cellular level (internal or cellular respiration), in response to concentration gradient, oxygen diffuses from the blood to the tissues while C02 moves from the tissues to the blood and the blood is reoxygenated by the lungs. Thus, based on the pressure gradient, during internal or cellular respiration, oxygen concentration of tissue fluid is lower than that of the blood to enable diffusion of oxygen into the tissues and carbon dioxide into the blood. Hemoglobin, the oxygen carrying protein of the RBCs transports oxygen (approximately 97%) to the tissues. The hemoglobin molecule combines with oxygen to form oxyhemoglobin. The formation of oxyhemoglobin is easily reversible, allowing hemoglobin and oxygen to dissociate (deoxyhemoglobin), which frees oxygen to enter tissues. Reduced hemoglobin (deoxyhemoglobin) combines with carbon dioxide, and the venous blood transports the majority of carbon dioxide back to the lungs to be exhaled. Relaxation of the diaphragm and contraction of the internal intercostal muscles allow air to escape from the lungs. Hence increased carbon dioxide in the blood is the main trigger that keeps us breathing. Oxygen carried in a sample of blood can be measured as: Obizoba 2021 pg. 1 The oxygen dissolved in plasma expressed as the partial pressure of oxygen (Pa02). Normal Pa02 in arterial blood is 80-100 mm Hg The amount of oxygen bound to hemoglobin expressed as the percentage of oxygen that is saturated with oxygen (Sa02). Normal saturation is 95-100% Factors Influencing Oxygenation Any condition that affects respiratory muscles and cardiopulmonary functioning directly affects the body’s ability to meet oxygen demands. Since hemoglobin carries the majority of oxygen to tissues, anemia and inhalation of toxic substances decrease the oxygen-carrying capacity of blood by reducing the amount of available hemoglobin to transport oxygen. Anemia (e.g., a lower-than-normal hemoglobin level) is a result of decreased hemoglobin production, increased red blood cell destruction, and/or blood loss leading to fatigue. Any condition that reduces chest wall movement will result in decreased ventilation. If the diaphragm is unable to descend fully with breathing, the volume of inspired air decreases, delivering less oxygen to the alveoli and all tissues. With the decline of the concentration of inspired oxygen, the oxygen-carrying capacity of the blood decreases. Decreases in the fraction of inspired oxygen concentration (FiO2) are caused by upper or lower airway obstruction, which limits delivery of inspired oxygen to alveoli. When there is low oxygen, the body attempts to adapt to the increased carbon dioxide levels by increasing the rate and depth of respiration. The patient’s work of breathing increases, and the patient eventually displays signs and symptoms of hypoxemia. Patients with pulmonary diseases are at greater risk for hypoxemia. Oxygenation decreases as a direct consequence of chronic lung disease. Changes in the anteroposterior diameter of the chest wall (barrel chest) occur because of overuse of accessory muscles and air trapping as in emphysema. The diaphragm is flattened, and the lung fields are over distended, resulting in varying degrees of hypoxemia and/or hypercapnia. Administering Cardiopulmonary resuscitation (CAB) If a patient’s hypoxia is severe and prolonged, cardiac arrest results. A cardiac arrest is a sudden cessation of cardiac output and circulation. When this occurs, oxygen is not delivered to tissues, carbon dioxide is not transported from tissues, tissue metabolism becomes anaerobic, and metabolic and respiratory acidosis occurs. Permanent heart, brain, and other tissue damage occur within 4 to 6 minutes. Cardiopulmonary Resuscitation (CPR) is needed to restore circulation. Recall the chest compressions, airway opening, breathing, and defibrillation with automatic external defibrillator [AED] of CPR. Obizoba 2021 pg. 2 Alterations in Respiratory Functions Illnesses or conditions that affect ventilation or oxygen transport cause alterations in respiratory functioning. The goal of ventilation is to produce a normal arterial carbon dioxide tension (PaCO2) between 35 and 45 mm Hg and a normal arterial oxygen tension (PaO2) between 80- and 100-mm Hg. Hypoventilation and hyperventilation are often determined by arterial blood gas analysis. Hypoxemia refers to a decrease in the amount of arterial oxygen. Nurses monitor arterial oxygen saturation (SpO2) using a noninvasive oxygen saturation monitor pulse oximeter. Normally SpO2 is greater than or equal to 95%. Hypoventilation (decreased rate or depth of air movement into the lungs) occurs when alveolar ventilation is inadequate to meet the oxygen demand of the body or eliminate sufficient carbon dioxide. As alveolar ventilation decreases, the body retains carbon dioxide. Hyperventilation is ventilation in excess of that required to eliminate carbon dioxide produced by cellular metabolism. Signs and symptoms of hyperventilation include rapid respirations, sighing breaths, numbness and tingling of hands/feet, light-headedness, and loss of consciousness. Hypoxia is inadequate tissue oxygenation at the cellular level. Dyspnea is a clinical sign of hypoxia. It is the subjective sensation of difficult or uncomfortable breathing. Dyspnea is associated with exaggerated respiratory effort, use of the accessory muscles of respiration, nasal flaring, and marked increases in the rate and depth of respirations. The clinical signs and symptoms of hypoxia include apprehension, restlessness, inability to concentrate, decreased level of consciousness, dizziness, and behavioral changes. The patient with hypoxia is unable to lie flat and appears both fatigued and agitated. Vital sign changes include an increased pulse rate and rate and depth of respiration. Cyanosis, blue discoloration of the skin and mucous membranes caused by the presence of desaturated hemoglobin in capillaries, is a late sign of hypoxia. When a patient is in dyspnea, raising the head of the bed is a priority intervention that eases the shortness of breath. Airway Management Maintaining a patent airway is a nursing priority which involves mobilizing secretions, suctioning the airway, and managing artificial airways mechanical or assisted ventilation (endotracheal tubes-ET and tracheostomy tube-TT) to promote adequate gas exchange and lung expansion. Airway maintenance may require use of artificial airways and suctioning. An artificial airway is used for a patient with a decreased level of consciousness or an airway obstruction and aids in removal of tracheobronchial secretions. The presence of an artificial airway places a patient at high risk for infection and airway injury. Use clean technique for oral airways but use sterile technique in caring for and maintaining endotracheal and tracheal airways to prevent health care–associated infections (HAIs). Obizoba 2021 pg. 3 A physician or specially trained clinician inserts the ET tube. The tube is passed through the patient’s mouth, past the pharynx, and into the trachea. It is generally removed within 14 days; however, it is sometimes used for a longer period of time as needed. If a patient requires longterm assistance from an artificial airway, a tracheostomy is considered. A surgical incision is made into the trachea, and a short artificial airway (a tracheostomy tube) is inserted. Most tracheostomies have a small plastic inner tube that fits inside a larger one (the inner cannula). It’s advised that a smaller sized inner cannula be placed at the bedside to be handy when there is accidental ejection of the inner cannula. The most common complication of a tracheostomy tube is partial or total airway obstruction caused by buildup of respiratory secretions. If this occurs, the inner tube can be removed and cleaned or replaced with a temporary spare inner tube that should be kept at the patient’s bedside. Keep tracheal dilators at the bedside to have available for emergency tube replacement or reinsertion. Humidification from air humidifiers or humidified oxygen tracheostomy collars can help prevent drying of secretions that cause occlusion. Suctioning (orally, nasally, or endotracheally) is necessary when patients are unable to clear respiratory secretions from the airways by coughing or other less invasive procedures. Suctioning techniques include oropharyngeal and nasopharyngeal suctioning, orotracheal and nasotracheal suctioning, and suctioning of an artificial airway Oropharyngeal and nasopharyngeal Used when the patient can cough effectively but is not able to clear secretions. With the client in low Fowler or sitting position, clean technique with the Yankauer is used to manage oropharyngeal secretions. Orotracheal and nasotracheal Used when the patient is unable to manage secretions by coughing and does not have an artificial airway Tracheal Used with an artificial airway The two current methods of suctioning are the open and closed methods. Open suctioning involves using a new sterile catheter for each suction session. Wear sterile gloves and follow Standard Precautions during the suction procedure. Closed suctioning involves using a reusable sterile suction catheter that is encased in a plastic sheath to protect it between suction sessions. Closed suctioning is most often used on patients who require invasive mechanical ventilation to support their respiratory efforts because it permits continuous delivery of oxygen while suction is performed and reduces the risk of oxygen desaturation. Although sterile gloves are not used in this procedure, nonsterile gloves are recommended to prevent contact with splashes from body fluids. Prior to suctioning, hyperoxygenate the client using a bag-valve-mask (BVM) or specialized ventilator function with an FiO2 of 100%. The nurse would first suction a small amount of water Obizoba 2021 pg. 4 through the catheter to ensure that the catheter's suction is functioning properly. In tracheal suctioning, which is done as needed following assessment of the lung sounds, when the catheter is inserted to the necessary distance, use suction pressure between 100 and 120 mm Hg as you withdraw. Apply suction intermittently only while withdrawing the catheter. Rotating the catheter enhances removal of secretions that have adhered to the sides of the ET tube. The entire procedure from catheter passage to its removal is done quickly, lasting no longer than 10 to 15 seconds to avoid hypoxemia and the vagal response. Repeat suctioning if needed. Limit total suctioning time to 5 min, Mechanical Ventilation Mechanical ventilation is use of a machine to breathe for a patient who cannot breathe on his or her own. It can be invasive or noninvasive. Clinical indications for invasive mechanical ventilation include reversing hypoxia and acute respiratory acidosis, relieving respiratory distress, preventing or reversing atelectasis and respiratory muscle fatigue, allowing for sedation and/or other neuromuscular blockade, decreasing oxygen consumption, reducing intracranial pressure and stabilizing the chest wall. A mechanical ventilator pushes airflow into the patient's lungs to help them breathe. It can be used to either fully or partially replace spontaneous breathing depending on the need of the patient. Noninvasive positive-pressure ventilation (NPPV) is used to prevent using invasive artificial airways (ET tube or tracheostomy) in patients with acute respiratory failure, cardiogenic pulmonary edema, or exacerbation of COPD. It has also been used following extubating of an ET tube. Continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP) are the common NPPV in practice. They decrease Equipment includes a mask that fits over the nose or both nose and mouth and a CPAP or BiPAP machine that delivers air to the mask. The smallest mask with the proper fit is the most effective. Because straps hold the mask in place, it is important to assess for excess pressure on the patient’s face or nose that could cause skin breakdown or necrosis. The mask should have enough slack to allow one to two fingers between the straps and the face. CPAP which can also be used in home settings provides oxygenation but not ventilation and is limited by the patient’s ability to breathe making it not the best choice of NPPV. The most common and better mode of support used in the hospital settings is bilevel positive airway pressure (BiPAP) that in addition to meeting the CPAP capabilities also detects the patient’s inspiratory effort and delivers greater pressure during inspiration. Complications of noninvasive ventilation include facial and nasal injury and skin breakdown, dry mucous membranes and thick secretions, and aspiration of gastric contents if vomiting occurs during ventilation. Ensure facial skin integrity interventions to prevent skin breakdown. Perform good oral hygiene every few hours while a patient is on BiPAP to relieve dryness. Obizoba 2021 pg. 5 Chest Tube The loss of negative intrapleural pressure causes the lung to collapse. A catheter inserted through the thorax to remove air and fluids from the pleural space, to prevent air or fluid from reentering the pleural space, or to reestablish normal intrapleural and intrapulmonary pressures. Chest tubes are common after chest surgery and chest trauma and are used for treatment of pneumothorax or hemothorax to promote lung reexpansion. Chest tubes improve breathing patterns by removing accumulations of air and fluid from the pleural space, permitting the lungs to return to normal expansion. Oxygen Therapy Promotion of lung expansion, mobilization of secretions, and maintenance of a patent airway assist patients in meeting their oxygenation needs. The goal of oxygen therapy is to prevent or relieve hypoxia by delivering oxygen at concentrations greater than ambient air (21%). Supplemental oxygen therapy offers many benefits to patients with chronic cardiopulmonary diseases. Oxygen Delivery Methods Oxygen is supplied to a patient’s bedside either by oxygen tanks or through a permanent wallpiped system. In the hospital or home, oxygen tanks are delivered with the regulator in place. FiO2 is the fraction (0.21) or percentage (21%) of inspired oxygen. 21 is the percentage of oxygen in the atmosphere (room or ambient air). Patients with respiratory, hematology, or cardiovascular problems receive oxygen enriched or supplemental oxygen which raises their FiO2 above 21%. FiO2 can range from 21-100% with supplementation oxygen. For nasal cannula or simple face mask, each additional liter of oxygen increases FiO2 by 3-4%. Thus, 1L is 24%, 2L is 28%, 3L is 32% etc. The oxygen delivery methods include Nasal Cannula, Face Masks (simple, partial rebreather, nonrebreather, venturi, and trachcollar), face tent, invasive and noninvasive ventilation support. The Incentive Spirometer (IS) also promotes oxygenation. A nasal cannula (NC) is a tubing with two small prongs for insertion into the nares. It delivers an FiO2 of 24% to 44% at a flow rate of 1 to 4 L/min but can go up to 6 L/min but will cause nasal dryness. The two nasal prongs are slightly curved and inserted in a patient’s nostrils. Tubing is easily dislodged, and extended use can lead to skin breakdown and dry mucous membranes. NC is well-tolerated. The client is able to eat, talk, and ambulate with it. Nurse should ensure use of water-soluble gel to prevent dry nares. Provide humidification for flow rates of 4 L/min and greater. To maintain skin integrity, assess the patient's external ears, nares, and nasal mucosa for breakdown at least once per shift. Masks An oxygen mask is a plastic device that fits snugly over the mouth and nose and is secured in place with a strap. It delivers oxygen as the patient breathes through either the mouth or nose by way of a plastic tubing at the base of the mask that is attached to an oxygen source. Assess for proper placement of the Obizoba 2021 pg. 6 mask on the patient's face. Eating, drinking, and talking impairment is part of the disadvantages of all face masks. Simple facemask provides FiO2 of 35% to 50% at flow rates of 6 to 12 L/min. Flow rates less than 6 L/min can result in rebreathing of CO2. Monitor for skin breakdown. Make sure the client wears a nasal cannula during meals and replace the facemask after eating. Partial rebreather mask has a reservoir bag attached with no valve, which allows the client to rebreathe up to ⅓ of exhaled air together with room air. It also allows easier humidification of oxygen. It delivers an FiO2 of 60% to 75% at flow rates of 6 to 11 L/min. Nursing action involves keeping the reservoir bag from deflating by adjusting the oxygen flow rate to keep the reservoir bag ⅓ to ½ full on inspiration. Non-rebreather (NRB) mask delivers the highest O2 concentration possible (except for intubation). Delivers an FiO2 of 80% to 95% at flow rates of 10 to 15 L/min to keep the reservoir bag ⅔ full during inspiration and expiration. Assessing that the reservoir bag stays inflated ensures appropriate oxygen delivery? Venturi mask delivers higher oxygen concentrations. It delivers the most precise oxygen concentration with humidity added and is best for clients who have chronic lung disease. Delivery of FiO2 of 24% to 50% at flow rates of 4 to 12 L/min via different size adapters, which allows specific amounts of air to mix with oxygen. Tracheostomy collar: a small mask that covers the surgically created opening of the trachea It delivers an FiO2 of 24% to 100% at flow rates of at least 10 L/min. Provides high humidification with oxygen delivery. ***Patients with COPD who are breathing spontaneously should never receive high levels of oxygen therapy because this may result in a decreased stimulus to breathe. Do not administer oxygen at more than 2 L/min unless a health care provider’s order is obtained. Low oxygen blood level is a breathing trigger for COPD patients. Increased supplemental O2 removes a COPD patient's hypoxic respiratory drive causing hypoventilation with resultant hypercarbia, apnea, and ultimate respiratory failure Face tent fits loosely around the face and neck for high flow oxygen delivery. Home Oxygen Therapy Home oxygen therapy improves patients’ exercise tolerance and fatigue levels and, in some situations, assists in the management of dyspnea. Three types of oxygen delivery systems are used: compressed gas cylinders, liquid oxygen, and oxygen concentrators. Before placing a certain delivery system in a home, assess the advantages and disadvantages of each type, along with the patient’s needs and community resources. Promote oxygen safety by the following measures: Place an “Oxygen in Use” sign on the patient’s door and in the patient’s room. If using oxygen at home, place a sign on the door of the house. No smoking should be allowed on the premises. Obizoba 2021 pg. 7 Keep oxygen delivery systems at least 10 feet (about 3 meters) away from anything that could generate a spark. Determine that all electrical equipment in the room is functioning correctly and properly grounded. An electrical spark in the presence of oxygen can result in a serious fire. When using oxygen cylinders, secure them so they do not fall over. Store them upright and either chained or secured in appropriate holders. Check the oxygen level of portable tanks before transporting a patient to ensure that there is enough oxygen in the tank. Ensure that patients have adequate oxygen tubing to safely move around their home environment. Tubing up to 98 feet (30 m) will deliver the prescribed oxygen flow rate. Cardiopulmonary rehabilitation Cardiopulmonary rehabilitation helps patients achieve and maintain an optimal level of health through controlled physical exercise, nutrition counseling, relaxation and stress-management techniques, and prescribed medications and oxygen. As physical reconditioning occurs, a patient’s complaints of dyspnea, chest pain, fatigue, and activity intolerance decrease. In addition, the patient’s anxiety, depression, or somatic concerns often decrease. Respiratory muscle training improves muscle strength and endurance, resulting in improved activity tolerance. Respiratory muscle training prevents respiratory failure in patients with COPD. One method for respiratory muscle training is the incentive spirometer resistive breathing device (ISRBD). Incentive spirometry encourages voluntary deep breathing by providing visual feedback to patients about inspiratory volume. It promotes deep breathing and prevents or treats atelectasis in the postoperative patient. There is solid evidence to support the use of lung expansion with incentive spirometry in preventing postoperative pulmonary complications following surgery. For better result, patient should sit up, keep close tight seal between the lips and the mouthpiece and take slow deep breathes. Breathing exercises include techniques to improve ventilation and oxygenation. The three basic techniques are deep-breathing and coughing exercises, pursed-lip breathing, and diaphragmatic breathing. Deep-breathing and coughing exercises are routine interventions used by postoperative patients. Pursed-lip breathing involves deep inspiration and prolonged expiration through pursed lips to prevent alveolar collapse. While sitting up, instruct the patient to take a deep breath and exhale slowly through pursed lips as if blowing through a straw. Have him or her blow through a straw into a glass of water to learn the technique. Diaphragmatic breathing is a deep breathing exercise that fully engages the diaphragm and increases the efficiency of the lungs. It involves fully engaging the stomach, abdominal muscles, and diaphragm when breathing. The exercise improves efficiency of breathing by decreasing air trapping and reducing the work of breathing. Obizoba 2021 pg. 8 Diagnostic Tests Tests used for cardiopulmonary functioning are blood specimens (ABGs), X-rays of the organs, and TB skin testing. After any procedure, monitor the patient for signs of changes in cardiopulmonary functioning, such as sudden shortness of breath, pain, oxygen desaturation, and anxiety. Sputum specimen collection is used to identify acid-fast bacilli (AFB) to diagnose tuberculosis (requires three consecutive morning samples). NURSING ACTIONS Offer mouth care and rinse with water not mouth wash prior to obtaining the sample. Obtain specimens early in the morning. Wait 1 to 2 hours after the client eats to obtain a specimen to decrease the likelihood of emesis or aspiration. Use a sterile container for routine cultures and AFB testing. Respiratory Function Nursing Diagnoses Nursing Diagnoses Ineffective airway clearance Ineffective breathing patterns Impaired gas exchange Decreased cardiac output Ineffective tissue perfusion Other associated Nursing Diagnoses Deficient knowledge Activity intolerance Disturbed sleep pattern-due to dyspnea during sleep and sleep apnea Imbalanced nutrition due to cardiac and pulmonary diseases Acute pain due to ischemia Anxiety ***Summary notes contents adapted from course textbook, ATI, other books, and online literature*** Obizoba 2021 pg. 9