Critical Care Nursing Program August to November, 2015 Full-time. Lesson A5 Ventilation & Oxygenation Failure Recognition & Response

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1 Critical Care Nursing Program August to November, 2015 Full-time Lesson A5 Ventilation & Oxygenation Failure Recognition & Response

2 Lesson Five Ventilation and Oxygenation I Failure- Recognition and Response Critical care nurses should be able to promote optimal oxygenation and ventilation in patients, identify individuals at risk for impaired oxygenation or ventilation, recognize when individuals have impaired oxygenation and ventilation and respond with appropriate interventions. Thus far, we have reviewed normal ventilation and oxygenation through the four phases and discussed disorders that would impair and potentially cause hypoxemia including primary and non-primary respiratory disorders. This lesson reviews recognition of respiratory failure and critical responses. Lesson Outcomes On completion of this unit the learner will be able to: 1. Describes causes and provide exemplars of ventilation and oxygenation failure. 2. Recognize clinical manifestations of failure to ventilate and failure to oxygenate. 3. Describe treatment strategies of the client experiencing respiratory failure. 4. Differentiate between low flow and high flow oxygen systems. 5. Describe pharmacology used in the treatment of respiratory failure. 6. Describe basic airway adjuncts. Resources Urden, L. D., Stacy, K. M., & Lough, M. E. (2014). Critical care nursing: diagnosis and management (7th ed.). St. Louis: Mosby, Elsevier. pp , , , Recognizing Ventilation and Oxygenation Failure Ventilation and oxygenation failure, or acute respiratory failure is a common reason for admission to a critical care unit. By analyzing the arterial blood gases, acute respiratory failure can be differentiated between a failure to ventilate (hypercapnic failure) or failure to oxygenate (hypoxemic) or a combination of both. Assessment findings between the two are subtle but well differentiated in your readings. Ventilation and oxygenation failure is caused by disorders such as alveolar hypoventilation, hypoxemia or decreased cardiac output. We have discussed numerous exemplars of these disorders. August 2015 RN Professional Development Centre Page 2

3 Responses Interventions for hypoxia are aimed at identifying and treating the underlying cause. Regardless of the cause, the oxygen supply to the tissues must be improved with the goal of alleviating the hypoxia. This usually requires the administration of oxygen and, pharmacological agents, and if the client is not breathing effectively, the use of airway adjuncts and subsequent mechanical ventilation. Please read the following: Urden et al., p Oxygen Therapy One technological intervention used to treat hypoxemia, to reduce the work of breathing, and to decrease myocardial work is oxygen therapy. Oxygen therapy can be delivered to the client who breathes spontaneously by a variety of devices. These devices have different features, such as the concentration of oxygen they are capable of delivering. When these devices fail to meet the client s oxygen requirements and the client can no longer adequately ventilate, intubation and mechanical ventilation therapy are required. Thus, in order to effectively manage the client who requires these technological interventions, the acute care specialty nurse must have a clear understanding as to how these interventions are correctly implemented. Administration of supplemental oxygen increases the alveolar oxygen pressure (PAO 2 ). This results in an increased pressure gradient across the alveolar-capillary membrane, diffusion increases, and the arterial oxygen pressure (PaO 2 ) rises. When the PaO 2 rises it removes the stimulus, which triggered the SNS to increase the client s tidal volume, rate of respirations, heart rate, and cardiac contractility, as well as the vasoconstriction to non-vital organs. The result is a reduction in the work of breathing and myocardial workload. It should be noted that hypotension could occur when the PaO 2 rises as the stimulus for vasoconstriction has also been removed. Although most nurses regularly implement oxygen therapy, there are a number of principles that are worth reviewing before discussing delivery methods. The key differences in delivery methodology and the hazards that are unique to the acute care specialty environment are then described in detail. The required reading and supplementary notes review these principles and highlight key differences. Oxygen therapy is usually administered to clients who are hypoxemic or who have tissue hypoxia. The amount of oxygen administered depends on the client s disorder and associated pathophysiology. The goal of therapy is to achieve a PaO 2 of mm Hg or oxygen saturation (SaO 2 ) of at least 90% without causing a rise in the client s PaCO 2. August 2015 RN Professional Development Centre Page 3

4 Please read the following: Urden et al., p Treat oxygen as a drug and ensure its safe usage. While it is necessary to obtain a medical order for oxygen therapy, there will be emergency circumstances where withholding oxygen while awaiting a medical order could seriously harm a client. Each hospital should have written protocols or policies that provide legal support for nurses to initiate oxygen in emergency situations. It is important to know your agency s policy. Oxygen Delivery Systems Before initiating oxygen therapy, each client should be individually assessed to determine the appropriate method of oxygen delivery. A past history of heart and lung dysfunction is an important element in this determination. Your reading makes the distinction between low flow, high flow and reservoir oxygen delivery systems but does not specifically discuss the hazards of low flow delivery systems. A few key points are provided here. Low Flow Systems Low flow oxygen systems depend upon the client inhaling adequate volumes of room air to mix with the oxygen from the system. This mixing of room air and O 2, in the natural reservoir formed by the oro- and nasopharynx, dilutes the oxygen to the prescribed oxygen percentage. If the client s respiratory rate or depth of inhalation decreases, the relative oxygen percentage will rise. Conversely, if the client s respiratory rate and/or depth increase significantly, there will be more room air drawn in relative to the O 2 flow from the system and the inspired oxygen percentage will be reduced below the prescribed level. The nurse must closely monitor the client s respiratory rate and depth (V T ). Thus, the main danger of a low flow oxygen delivery system is an inconsistent level of oxygen. This is a real concern for the client who has chronic obstructive lung disease (COPD) with CO 2 retention. In the client with a chronically high PaCO 2, the chemoreceptors (which normally react to high PaCO 2 levels) no longer function. As a result the client s only drive to breath comes from the chemoreceptors for hypoxemia. Falling asleep may cause the client s minute ventilation to drop. When receiving oxygen from a low flow system, the diminished room air dilution from the reduction in the client s minute ventilation will cause the inspired oxygen concentration to quickly rise. If it is high enough the client may well stop breathing because their hypoxic drive is eliminated due to the high concentration of oxygen. August 2015 RN Professional Development Centre Page 4

5 Most commonly used Low flow system used in the clinical area is the nasal cannula. Nasal cannula Figure reprinted with permission: Scanlan, C.L., Wilkins, R.L., & Stoller, J.K. Egan s fundamentals of respiratory care (7th ed.). Mosby 1999/Access Copyright. High Flow Systems The most reliable oxygen delivery system for critically ill clients is a high flow system. A high flow system produces a high velocity of oxygen flow through an orifice in the mask or humidifier. The high velocity flow creates a sub-atmospheric pressure, which pulls air in from the surrounding atmosphere. This results in precise dilution of the oxygen in the system and the delivery of predictable and consistent oxygen concentrations. Changing both the size of the orifice in the system and the flow rate allows for the delivery of different oxygen percentages. One of the most common high flow oxygen delivery systems used in the acute care specialty unit is the air-entrainment mask (also known as the Venturi mask). Air-entrainment mask Figure reprinted with permission: Scanlan, C.L., Wilkins, R.L., & Stoller, J.K. Egan s fundamentals of respiratory care (7th ed.). Mosby 1999/Access Copyright. August 2015 RN Professional Development Centre Page 5

6 Reservoir System These systems feature a device that allows oxygen to be gathered and stored between client breaths. When a client s inspiratory flow exceeds the oxygen flow, they can draw on this oxygen reserve. Masks are the most common reservoir systems used. There are three types of reservoir masks: simple mask, partial rebreather mask, and nonrebreather mask. Simple mask Partial rebreather mask Non-rebreather mask Above figures reprinted with permission: Scanlan, C.L., Wilkins, R.L., & Stoller, J.K. Egan s fundamentals of respiratory care (7th ed.). Mosby 1999/Access Copyright. High Flow Nasal Cannula High flow nasal cannula is used frequently in the pediatric population and is emerging rapidly in the adult population (Dysart, 2009; Frat et al., 2015). High Flow Nasal Cannula use high flow rates to precisely delivery warm, humidified oxygen using a blending system, mixing air and oxygen to achieve a desired Fraction of Inspired Oxygen (F i 02). Patients will receive the predetermined F i 02 even if they mouth breathe, unlike when using regular nasal cannula. High Flow nasal cannula (HFNC) are better tolerated by patients than other high flow oxygen deliver as it is more comfortable and allows patient to eat, talk to family, sleep better, etc. (Maggiore et al, 2014). There are a variety of products that can be used to delivery High Flow Nasal Cannula. The two you will likely see in your area are Vapotherm TM and Optiflow TM. Although the set up may differ slightly, the mechanism of action and benefits are consistent. The classic patient receiving HFNC in the adult ICU population is the patient in acute pulmonary edema. Placing the patient on high flow nasal cannula may afford clinicians time to optimize the patient s preload before they decompensate with a complete hypoxemic respiratory failure requiring mechanical ventilation. August 2015 RN Professional Development Centre Page 6

7 Benefits of High Flow Nasal Cannula Benefits from High Flow Therapy (Frat et al, 2015) include: 1. Wash out nasopharyngeal anatomical deadspace 2. Decrease in inspiratory resistance 3. May provide continuous positive airway pressure also knows as mild distention pressure (may vary and is not measureable) 4. Reduces or eliminates the metabolic cost of heating/humidifying inspired gases 5. Improves muco-ciliary clearance 6. Decreased mechanical ventilation time Deadspace Wash out During a normal respiratory cycle, O2 is inspired through nose and mouth, passes down the nasopharynx into the trachea, down the mainstem bronchus, down the right and left bronchi, into the bronchioles, to the alveoli of the lungs to participate in gas exchange. CO2 is then exhaled back the same route and exhaled through the nose or mouth. Prior to all the C02 being exhaled the next breath is taken. This means there is some C02 still in the nasopharygeal space. This C02 is then re-breathed. This could lead to elevated C02 levels which could cause respiratory acidosis. This may lead to increased work of breathing for the patient. The flow rates of HFNC, as high as 60L/min, continuous push lingering C02 from the nasopharynx out the mouth, essentially washing out that anatomical deadspace (Frat et al, 2015) This also allows for more concentrated 02 to be delivered directly to the alveoli to participate in gas exchange. Decrease in Inspiratory Resistance Many traditional oxygen delivery devices have a portion of air entrainment where room air mixes with inspired oxygen and can alter the Fi02 that is actually received by the patient. If the patient is not getting the required amount of oxygen, their work of breathing could increase. This in turn increases the inspiratory resistance and can contribute to respiratory decompensation. High Flow therapy provides enough flow to meet or exceed the patient s peak inspiratory demand. This helps reduce the work of breathing therefore reducing inspiratory resistance (Frat et al, 2015). The high flow rates also help deliver a more precise dose of 02 and prevent air dilution even if the patient is breathing orally. August 2015 RN Professional Development Centre Page 7

8 Continuous Positive Airway Pressure (Mild Distention Pressure) There is clinical evidence to show that high flow delivery can generate low levels of continuous positive airway pressure. In the neonatal population, HF nasal prongs were showed to provide up to 8cm H20 of PEEP (Dysart, 2009). The high flow causes distention in the lungs which improves the mechanics of ventilation by optimizing lung compliance and maintaining alveoli patency. This will all lead to improved gas exchange. The amount of positive airway pressure provided is variable and difficult to measure, but is dependent on: The flow setting (l/min) The patients anatomical dimensions (amount of dead space) The leak out around the prongs in the nose (prongs should occupy about 50% of the internal diameter of the nares) Decreased Metabolic Cost Nasal passages are meant to warm inspired air from ambient room temperature (approx 21 C) to body temperature (37 C). Warm arm holds more water vapor and therefore is more humid. Nasal passages also humidify inspired air to 100% relative humidity to allow the gas to hold as much water as possible. Conventional oxygen from the wall in the patient s room is cool (15 C) and dry. More energy is expended when the inhaled air is cooler and drier. Our bodies do not reserve this extra heat and therefore our mucosal tissues need to work harder to produce this heat for warming and water vaporization. High Flow Therapy completely warms and humidifies the inspired gas. The patient expends less energy to warm and humidity the gas. This is especially significant in the neonate population where energy expenditure is closely linked to weight gain of infants (Frat et al, 2015) Improves muco-ciliary clearance Optimal humidity helps prevent drying of airway and mucosal tissue damage, which helps maintain cilia function (Hasani et al., 2008). When cilia are functioning properly they help to clear secretions. This decreases the risk of respiratory infections or ventilator complications. Moist air and decreased secretions also helps promote patient comfort and therefore improves compliance with oxygen therapy. August 2015 RN Professional Development Centre Page 8

9 Decreased Mechanical Ventilation time As stated above, HFNC provides some continuous positive airway pressure (CPAP). CPAP is a form of Non Invasive Positive Pressure Ventilation (NIPPV). It means the patient can remain on HFNC for longer without the need for mechanical ventilation and can be extubated directly from a mechanical ventilator to HFNC therapy. This lessens the amount of time mechanical ventilation is required. The figure below outlines the conventional progression of O 2 requirements over time. Compare the time on ventilation in the following diagram with HFNC: August 2015 RN Professional Development Centre Page 9

10 As illustrated, HFNC offers benefits that could potentially decrease the time on a mechanical ventilator, which is known to improve patient outcomes. You will learn more about this in the lesson on mechanical ventilation. Contraindications for use of High Flow Nasal Cannula There are certain patient conditions that are not suited to HFNC. These include: Impending respiratory failure with hypercapnea Pnemothorax Basal skull fracture Post-op Tracheal Esophageal fistula Obstructive sleep apnea *** High Flow Nasal Cannula Precautions *** Patients tolerate high flow nasal cannula easier and appear comfortable. Patients receiving high flow nasal cannula therapy have significant oxygenation issues and can decompensate rapidly. It is therefore crucial for acute care nurses to monitor the patient closely, frequently assess, communicate effectively with other health care team members, and have an alternative oxygen source with appropriate equipment at the patient s beside for patient safety. A warning sign for family and health care team members at the bedside is often used. Inhaled medications require specialized devices with high flow patients cannot inhale from a conventional aerosolized nebulizers while receiving high flow nasal cannula. Other Oxygen Delivery Devices Oxygen delivery systems have been adapted to meet the needs of clients with either endotracheal or tracheostomy tubes. T-Piece Method The T-piece method is used with both endotracheal and tracheostomy tubes. The T- piece has a simple construction that consists of a T-shaped connector, which attaches to the endotracheal/tracheostomy tube. Tubing attached to the nebulizer and oxygen flow meter is connected to one side of the T-connector while the client exhales through a short tube on the other side. The tube attached to the exhalation port acts as an oxygen reservoir with the intention that if the client inhales deeply, the prescribed F I O 2 will not be diluted with room air. It has the added benefit of directing the exhaled humidified air away from the client. August 2015 RN Professional Development Centre Page 10

11 Tracheostomy Mask A client with a tracheostomy may have oxygen delivered either with a T-piece or a tracheostomy mask. This small mask is especially adapted to sit over the client s tracheostomy. It can be more comfortable for the client than a T-piece because it is not directly attached to the tracheostomy and therefore causes less irritation from movement of the tracheostomy tube. T-piece Tracheostomy mask Above figures reprinted with permission: Scanlan, C.L., Wilkins, R.L., & Stoller, J.K. Egan s fundamentals of respiratory care (7th ed.). Mosby 1999/Access Copyright. Humidification Many clients who require oxygen have humidifiers attached to their O 2 delivery system. Humidification prevents some of the common effects of breathing a dry gas, such as dryness and irritation of the mucous membranes of the respiratory tract, reduced mucociliary activity and loss of body water. A humidifier may also be used for clients who are hypothermic because the warm moist air helps to warm the individual. Other clients who require humidified gas are those whose upper airways have been bypassed by endotracheal intubation or tracheostomy and those on a mechanical ventilator. Humidity is also desirable when a client is receiving an O 2 concentration greater than 30%. Humidification can be used with low or high flow systems. Complications of Oxygen Therapy The administration of oxygen is not without risk. Oxygen is a drug. Complications of oxygen therapy are well described in your required readings. As acute care specialty nurses, we are obligated to carefully assess our client s oxygenation status and ensure the client receives the lowest FiO 2 to meet his/her needs. August 2015 RN Professional Development Centre Page 11

12 Hopefully this review has refreshed your knowledge of the risks and benefits of oxygen therapy. Complete the following instructional activity to test your understanding of the concepts related to oxygen therapy. LEARNING ACTIVITY 3 True or False (T or F) 1. The goal of O 2 therapy is to maintain the client s PaO 2 at 100 mm Hg. 2. The potential for high flow systems to cause O 2 toxicity is higher than for low flow systems. 3. A low flow system causes entrainment of air and leads to a stable O 2 percentage. 4. Humidifiers are desirable when clients are on high percentages of O 2 for prolonged time periods. 5. Clients with COPD are always prescribed high flow systems. 6. One of the complications of administering high O 2 concentrations is absorption atelectasis from nitrogen wash out in the alveoli. 7. A client receiving O 2 therapy at an FIO 2 of.30 is at a moderate risk for the development of O 2 toxicity. 8. Late signs and symptoms of O 2 toxicity are caused from alveolar damage Match the following statements with the appropriate system A. High Flow System B. Low Flow System 9. Reducing the rate and/or depth of ventilation increases the oxygen percentage. 10. When a client requires a consistent O 2 percentage, what type of system would be utilized? 11. The best oxygen system for a client with COPD who retains CO 2 is? 12. A simple facemask is? 13. A Venturi mask is? August 2015 RN Professional Development Centre Page 12

13 Respiratory Pharmacology Please read the following: Urden et al., p. 580 Table Many pharmacological agents are used in the care of critically ill patients with respiratory dysfunction. The purpose of this section is to provide a brief overview of the classes of drugs used to relieve airflow obstruction, reduce inflammation, improve pulmonary circulation and promote the removal of secretions. Drug classifications include: bronchodilators (sympathomimetics and xanthines), inhaled anticholinergic agents, corticosteroids, pulmonary vasodilators, mucolytics and expectorants. More information regarding these drug classes can be found in the resources listed in the bibliography. Please remember that this is a guide (no dosages are given) and further information should be obtained from your unit s resources (nursing drug reference or current CPS) prior to administration. Bronchodilators treat airway obstruction in conditions such as a) asthma (bronchial smooth muscle contraction. b) bronchitis (mucosal hypersecretion). c) mucosal edema or inflammation. August 2015 RN Professional Development Centre Page 13

14 Section A Lesson Three Bronchodilators Agent MECHANISM OF ACTION COMMENTS ADRENALIN (Epinephrine) (IV) Epinephrine (aerosol) Isuprel (Isoprotenerol) Ventolin (albuterol) Aerosol/puffers Theophylline Aminophylline (Xanthines) - Nonselective=Stimulates both alpha and beta receptors. - Alpha receptors cause vasoconstriction (skin, muscles, kidneys and intestines) - Beta-1 receptors in heart stimulated to cause increase in HR and force of contraction - Beta-2 receptors causes vasodilation of peripheral blood vessels - Mimics all actions of the sympathetic nervous system including relaxation of bronchial smooth muscles. - Vaponephrin (Racemic epinephrine) is ***currently N/A in Canada substituting with IV epinephrine diluted in NS administered by aerosol Beta-1 selective---causes increased HR and force of contraction along with bronchial dilation - First line therapy in anaphylaxis, VT/VF arrest - Acts synergistically with theophylline. - May cause BP elevation and cardiac dysrhythmias, anxiety, diaphoresis, and nausea. - Sputum becomes pinkish following aerosol. - Major use tracheobronchitis (extubation trachitis). - rarely used for improving respiratory function as replaced with more specific Beta-2 selective drugs - short half life (1-2 hours) Beta-2 selective - causes smooth muscle relaxation - least likely to cause side effects - tremors from skeletal muscle stimulation - tachycardia reflex from mild hypotension secondary to skeletal muscle relaxation - short half life (1-2 hours) - decrease in serum potassium - produce bronchodilation by inhibiting the action of the enzyme that breaks down cyclic AMP - contributes to an accumulation of cyclic AMP, which serves to maintain bronchial smooth muscle relaxation, increase pulmonary blood flow, and relax the respiratory tract - Note: Smokers have increased levels of a liver enzyme that enhances the metabolism of aminophylline. This means that smokers need higher doses to maintain therapeutic levels. Aminophylline should NEVER be given I.V. push as it can cause tachydysrhythmias, hypotension, seizures, headaches, dizziness, and/or cardiac arrest - requires monitoring of blood levels - side effects/toxicity problems (CNS excitation, confusion, irritability, nausea, hypergylcemia) Revised Aug 2015 RN Professional Development Centre Page 14

15 Section A Lesson Three Anticholinergics have been used as a first line therapy for management of stable COPD patients for the past 20 years (Restrepo, 2007). Anticholinergics Agent Mechanism of Action Comments Ipratropium Bromide (Atrovent) - competes with acetylcholine at muscarinic receptors and causes bronchial smooth muscle relaxation - has poor systemic absorption and therefore relatively few side effects - short half life (6-8 hours) Corticosteroids reduce inflammation thereby decreasing bronchial constriction and airway hyperirritability. Corticosteroids Agent Mechanism of Action Comments Flovent, Beclovent or Pulmicort puffer Stabilizes cell membranes which reduces inflammation, bronchial constriction, and airway hyperirritability. Solumedrol(METHYL- PREDNISOLONE) IV/po Lowers the stimulation threshold of the Beta-2 receptors which enhances responsiveness to the sympathomimetics. - decreases inflammation by suppressing migration of WBC s Inhaled corticosteroids are used as a preventative measure. Not given for acute asthma attacks. Clients may be predisposed to oropharyngeal candida infections. Oral hygiene is promoted post inhalation. Assess serum glucose and electrolyte levels. NA + and water retention is enhanced, glucose utilization reduced, and Na + and Ca ++ excretion increased. Ca ++ intake via the GI tract is also impaired - monitor for S&S of infection with immunosuppression Revised Aug 2015 RN Professional Development Centre Page 15

16 Section A Lesson Three Pulmonary Vasodilators are an important treatment for pulmonary arterial hypertension. Treatment should focus on relieving the underlying cause. If left untreated, pulmonary hypertension eventually leads to right ventricular failure and death (Siobal, 2007). The following table summarized some acute care agents. Pulmonary Vasodilators Agent Mechanism of Action Comments Oxygen - hypoxemia causes vasoconstriction in pulmonary circulation - increased survival noted in patients with PAH and COPD treated with long term O2 therapy Calcium channel blockers IV/po Nitrous Oxide Gas Sildenafil (Viagra) po - inhibit the calcium ion influx in smooth muscle cells and cause relaxation and smooth muscle dilation - vasodilator effect on smooth muscle endothelial cell - binds with hemoglobin to form methemoglobin - enhances effects of nitrous oxide by inhibiting cgmp causing smooth muscle relaxation - vasodilator effects can cause dose related hypotension, increased shunting and hypoxemia - only used in mechanically ventilated patients - frequent ABG s to monitor methemoglobin - not to be used with nitrates as fatal reactions reported Mucolytics and expectorants are agents meant to reduce the viscosity of secretions and promote a more effective cough. These agents are used in diseases such as bronchitis and cystic fibrosis. Examples can include hypertonic saline (aerosol), N-acetylcysteine (aerosol), and pulmozyme. There is little supportive data in the literature and further research is indicated. Research does not support saline instillations to facilitate suctioning in intubated patients. Artificial Airways Please read the following: Urden et al., p Revised Aug 2015 RN Professional Development Centre Page 16

17 Section A Lesson Three Artificial airways are commonly used in acute care specialty units to relieve upper airway obstruction and provide a route for oxygen delivery in the unconscious to semiconscious client. Oral and nasal airways are commonly used in the post-anesthesia care unit (PACU) and the emergency room. Endotracheal and tracheostomy tubes are also utilized in these areas but are more common in the intensive care units. It is imperative that you have a solid knowledge of how to effectively care for the client with an artificial airway, regardless of the type. Nasal or oropharyngeal artificial airways are commonly required in circumstances where there is a need for: Conclusion a) Airway patency, b) Bronchial hygiene, or c) Emergency ventilation. Well done! There was a great deal of information presented in this lesson. You now have formed the basis of caring for each ICU patient. Understanding normal ventilation and oxygenation concepts, recognizing impaired ventilation and oxygenation and responding is key to providing effective care for intensive care patients. In the next lesson, we will learn about caring for patients with progressing ventilation and oxygenation impairments requiring advanced airway adjuncts and mechanical ventilation. Answer Key Learning Activity True/ False 1. F 5. F 2. F 6. T 3. F 7. F 4. T 8. T Mix and Match 9. B 12. B 10. A 13. A 11. A Revised Aug 2015 RN Professional Development Centre Page 17

18 Section A Lesson Three BIBLIOGRAPHY Chu, E.K., & Drazen, J.M. (2005). Asthma: One hundred years of treatment and onward. American Journal of Respirology and Critical Care Medicine, 171(11), Dysart, K., Miller, T., Wolfson, M., & Shaffer, T.H. (2009) Research in high flow therapy: Mechanisms of action. Respiratory Medicine, 103(10): Frat J, Thille AW, Mercat A, et al. (2015). High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. New England Journal of Medicine, 372(23), Hasani, A., Chapman, T.H., McCool, D., Smith, R.E., Dilworth, J.P., & Agnew, J.E. (2008). Domiciliary humidification improves lung mucociliary clearance in patients with bronchiectasis. Chronic Respiratory Disease (5), Holt, T.B. (2007). Inhaled beta agonists. Respiratory Care., 52(7), Kovacs, G., & Law, J. (2008). Airway management in emergencies. New York: McGraw- Hill Co. Maggiore, S. M., Idone, F. A., Vaschetto, R., Festa, R., Cataldo, A., Antonicelli, F.,... Antonelli, M. (2014). Nasal high-flow versus venturi mask oxygen therapy after extubation: Effects on oxygenation, comfort, and clinical outcome. American Journal of Respiratory and Critical Care Medicine, 190(3), Phua, G., & MacIntyre, N.M. (2007). Inhaled corticosteroids in obstructive airway disease. Respiratory Care., 52(7), Restrepo, R. (2007). Use of inhaled anticholinergic agents in obstructive airway disease. Respiratory Care., 52(7), Rubin, B.K. (2007). Mucolytics, expectorants and mucokinetic medications. Respiratory Care., 52(7), Siobal, M.S. (2007). Pulmonary vasodilators. Respiratory Care., 52(7), Skidmore-Roth, L. (Consultant). (2003) Mosby s nursing drug reference. St. Louis: Mosby. Urden, L. D., Stacy, K. M., & Lough, M. E. (2014). Critical care nursing: diagnosis and management (7th ed.). St. Louis: Mosby, Elsevier. Wiegand, D. (Ed.). (2011). American association of critical care nurses: Procedure manual for critical care. St. Louis: Elsevier. Wilkins, R.L., Stoller, J.K., & Kacmarek, R.M. (2009). Egan s fundamentals of respiratory care (9th ed.). St. Louis, Missouri: Mosby. Revised Aug 2015 RN Professional Development Centre Page 18