Critical Care Nursing Program August to November, 2015 Full-time. Lesson A6 Ventilation & Oxygenate II Mechanical Ventilation

Transcription

1 Critical Care Nursing Program August to November, 2015 Full-time Lesson A6 Ventilation & Oxygenate II Mechanical Ventilation

2 Lesson Six Ventilation and Oxygenation II Mechanical Ventilation Introduction Mechanical ventilation is often crucial to the effective management of clients in the acute care specialty setting. It is used to improve alveolar ventilation, to treat hypoxemia and tissue hypoxia, to decrease work of breathing, and to administer gas under pressure to prevent atelectasis. The ability of the mechanical ventilator to reach these goals and sustain life is only as good as the health care team using it. As an integral part of this team, the acute care specialty nurse must have a sound understanding of the ventilator s functions and capabilities. In collaboration with the respiratory therapist and physician, the acute care specialty nurse ensures that clients receive the ventilation therapy best suited to their needs. Nursing care of ventilated clients includes assessing the client s responses to mechanical ventilation, monitoring the settings of the machine, and troubleshooting when the ventilator s alarms indicate that an alteration in ventilation has occurred. Learning Outcomes On completion of this unit, the learner will be able to: Resources 1. Describe respiratory disorders that require mechanical ventilation. 2. Discriminate between invasive and noninvasive ventilation, types of ventilators, modes of ventilation, and adjuncts, settings and alarms used for positive pressure ventilation. 3. Identify the appropriate mode of ventilation for patient condition. 4. Relate ABG interpretation to mechanical ventilation. 5. Describe the weaning modes of mechanical ventilation. 6. Identify complications of mechanical ventilation. 7. Using a case study approach, apply the modes of ventilation for a client in respiratory distress. Urden, L. D., Stacy, K. M., & Lough, M. E. (2014). Critical care nursing: diagnosis and management (7th ed.). St. Louis: Mosby, Elsevier. pp August 2015 RN Professional Development Centre Page 2

3 Indications for Mechanical Ventilation Mechanical ventilation is a therapeutic intervention used to support ventilation - the movement of air in and out of the lungs. Although ventilators can improve alveolar ventilation, they do not have the capacity to perform external respiration, which is the diffusion of gases across the alveolar-capillary membrane. Mechanical ventilators are used to support the client s respiratory status until the precipitating etiology can be corrected. Many of the etiologies leading to respiratory failure, which require the use of mechanical ventilation, were presented in the Ventilation and Oxygenation lessons. There are two main types of respiratory failure. For ease of remembering content, the disorders are grouped into two main categories: those that lead to inadequate ventilation (alveolar ventilation) and those that impair oxygenation or gas exchange. These disorders can cause respiratory failure and lead to the need for mechanical ventilation. Your required reading has an excellent concept map on acute respiratory failure that guides our responses in treating respiratory failure. Please read the following: Urden p The following table can be used as guidelines for mechanical ventilation. The final decision will be based upon clinical evaluation of the patient. Tidal Volume (V T ) Minute Ventilation (V E ) Pulmonary Function tests: Respiratory Rate (f) Arterial Blood Gases: V T < 5 cc/kg V E > 10 L/min f > 35/min or < 10/min Inadequate Ventilation ph < 7.20 PaCO 2 > 55 mmhg Hypoxemia PaO 2 /F I O 2 ratio < 200 GCS <8 PaO 2 < mmhg Invasive and Non-Invasive Ventilation Invasive ventilation refers to mechanical ventilation that requires an artificial airway (endotracheal or tracheal tube) to deliver ventilation. The bulk of this lesson will focus on invasive ventilation. August 2015 RN Professional Development Centre Page 3

4 Non-invasive ventilation is used when patients require assistance with ventilation but does not require an artificial airway. The ventilation is delivered using specially designed non-invasive nasal masks, face masks or nose pieces. Delivery of respiratory support in this manner is called non-invasive positive pressure ventilation (NPPV) and will be briefly discussed later. Classification of Mechanical Ventilators Ventilators are mechanical devices that attempt to mimic or replace the normal mechanisms of breathing. There are three main types of ventilators: negative pressure, positive pressure and high-frequency. 1. Negative Pressure Ventilators There are two examples of negative pressure ventilators: the Iron Lung and the Cuirasse. Negative pressure ventilators were popular during the polio epidemic in the 1950 s and did not require patients to have an artificial airway. These are no longer used in acute care specialty units and therefore will not be described further. 2. Positive Pressure Ventilators The classification of mechanical ventilator most commonly used in the acute care specialty setting is the positive pressure ventilator. Positive pressure ventilators deliver gas under positive pressure during the inspiratory phase of ventilation. The gas is moved from an area of higher pressure in the ventilator to an area of lower pressure in the lungs. Positive pressure ventilation eliminates the negative pressure generated by the lungs (it initiates ventilation with positive pressure). The elimination of the normal negative pressure generated by the lungs and the continuous application of positive pressure to the airways can lead to many complications, which will be discussed later in this lesson. Positive pressure ventilators can provide artificial ventilation to a patient in many different ways. Modes or ways that a ventilator can be set to deliver ventilation are comprised of four factors. These factors which can be preset on the ventilator tell the machine when to stop inspiration and to allow expiration to occur. These factors are defined as: 1. Volume: The amount of air moved into the lungs. 2. Flow: The displacement or movement of a gas volume. 3. Pressure: Force needed to overcome the resistance to the flow of gas through the airways and to inflate the lungs. 4. Time: The interval over which the flow of gas moves in and out of the lungs. August 2015 RN Professional Development Centre Page 4

5 Note: Expiration occurs passively as with spontaneous ventilation. Positive pressure ventilators in an acute care specialty setting use either volume, pressure, or a combination of both to provide ventilation. Volume Ventilation Volume ventilation delivers a preset volume of gas to the lungs at which time the flow of gas stops and expiration occurs. The pressure and the inspiratory time vary from breath to breath. Even though the ventilator will deliver a preset tidal volume despite changes in the client s lung compliance or airway resistance, there is a safety mechanism which will stop gas flow when a maximum preset pressure limit is reached. At this time an alarm will sound. In this type of ventilation, tidal volume is stable for each breath delivered but pressure will vary. Pressure Ventilation In this type of ventilation, pressure is pre-set according to the patient s condition. The patient can take their own tidal volume but it will be based upon their resistance, compliance and pre-set pressure. This will be further explained when we discuss distinct modes of ventilation. Examples of positive pressure ventilators include: 1. Bennett Series (840/960) 2. Draeger (XL, V500) 3. Servo I Clinical Advantages and Disadvantages of Volume and Pressure Ventilation There are advantages and disadvantages to using volume and pressure when ventilating a patient. Volume ventilation results in a more stable minute ventilation (allowing clinicians to better control blood gas values) than pressure ventilation. Pressure ventilation allows for better patient ventilator synchrony. Although clinicians can only control either pressure or volume at one time, you should be aware that newer ventilators can switch between pressure and volume in an attempt to deliver guaranteed minute ventilation while maintaining patient ventilator synchrony (Kacmarek, Stoller & Heuer, 2013). This forms the basis for dual modes. August 2015 RN Professional Development Centre Page 5

6 3. High Frequency Ventilators This classification of ventilators delivers gas at a low pressure and high rate. High frequency ventilation lessens the risk of barotrauma and hemodynamic instability in patients with increased risk for volutrauma (e.g., bronchopleural fistulas, tracheoesophageal fistulas, ARDS, thoracic trauma). These ventilators are typically used when conventional ventilation is not effective and thus will only be briefly mentioned here. Note: Clients on mechanical ventilators should always have a manual resuscitation bag at the bedside. The nurse should not become so involved with the machine that the client is forgotten. When the ventilated client appears to be in respiratory distress and the nurse cannot immediately solve the problem, the client should be manually ventilated until the problem can be resolved. Manual resuscitators with a reservoir bag, such as the Laerdal resuscitator, when connected to oxygen are capable of delivering 100% F I O 2. The tidal volume delivered depends on the force used to squeeze the bag. When the bag is completely deflated, the delivered volume approximates 10-15mL/kg. The respiratory rate is determined by the number of times the bag is squeezed per minute. When the manual resuscitator is used, the nurse should synchronize the manually delivered breaths with the client s inspiratory effort. If the patient has no inspiratory effort the nurse should attempt to match the settings on the mechanical ventilator. The ease or resistance encountered when delivering the tidal volume roughly indicates lung compliance. If a client becomes hard to bag, it could indicate an increase in secretions, bronchospasms, or a pneumothorax. This is an advanced nursing skill that will be taught and practiced in your OSCE. Modes of Positive Pressure Ventilation The mode of ventilation refers to the way in which the machine ventilates the client. Remember that modes will be defined by the manner in which the ventilator cycles (volume, flow, pressure and time). Please be aware that terminology can vary with the brand of ventilator. This can become confusing! Let s try to break it down into simpler language. Ventilation modes can be divided into: Mandatory (the ventilator provides a breath for the patient) and Spontaneous (the ventilator assists the patient s breath) modes. Dual (ventilator switches between pressure and volume). An example is PRVC (Pressure Regulated Volume Control) mode. Dual modes are mentioned here as you may see them in clinical but you will not be tested on them in CCNP. August 2015 RN Professional Development Centre Page 6

7 1. Mandatory modes of ventilation (Volume and Pressure Modes) During volume controlled (VC) ventilation, the set tidal volume is supplied by the ventilator at a constant flow. The inspiratory pressure is variable and changes depending on the compliance and resistance in the lungs. The tidal volume (V T ) and the respiratory rate (RR) are programmed into the ventilator. This results in the minute ventilation (V E ). The velocity at which the tidal volume (V T ) is delivered is adjusted by changing the inspiratory flow. Volume controlled (VC) controlled modes include: 1. Assist Control (VC A/C) 2. Continuous Mandatory Ventilation (VC-CMV) 3. Synchronized Intermittent Mandatory Ventilation (VC-SIMV) During pressure controlled (PC) ventilation, two pressure levels are kept constant: PEEP (Positive End Expiratory Pressure) and the peak inspiratory pressure (Pinsp). The tidal volume (V T ) is variable. It will change depending on the pressure difference between PEEP and Pinsp, the lung s compliance and resistance, and the breathing effort of the patient. The respiratory rate (RR) is programmed into the ventilator. Pressure controlled modes include: 1. Assist Control (PC-A/C) 2. Continuous Mandatory Ventilation (PC-CMV) 3. Synchronized Intermittent Mandatory Ventilation (PC SIMV) General rule of thumb is that unless otherwise contraindicated by disease process, patients are initially placed on volume control ventilation. If peak airway pressures are too high, then the patient is switched to pressure control. 2. Spontaneous modes of ventilation (Spontaneous/Assisted modes) During the spontaneous ventilation modes, the patient initiates each breath. The pressure level (positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) at which spontaneous breathing takes place), can be adjusted. In all spontaneous ventilation modes, the spontaneous breaths are supported mechanically by using pressure support. Spontaneous modes include: 1. CPAP/PS (Pressure Support) As you progress through the explanations of the modes of ventilation in the following readings, pay particular attention to the most common modes of ventilation. These are the modes you will be responsible for understanding in CCNP: August 2015 RN Professional Development Centre Page 7

8 Volume Control Assist Control (VC -A/C) Volume Control Synchronous Intermittent Mandatory Ventilation (VC-SIMV) Pressure Support Ventilation (PSV) Pressure Control Assist Control Ventilation (PCV A/C) Please read the following: Urden et al p (Stop at complications). Also Tables 21-5 Modes of Mechanical Ventilation 21-6 Ventilator Settings on p Box 21-6, p 570 Whew! That was a lot of modes of ventilation and a great deal of terminology in a short period of time. You can see how it can get confusing! When in clinical, refer to your laminated card on modes of mechanical ventilation. Our respiratory therapy colleagues have been very gracious in sharing their resources. Haven t received your card yet? Check with your faculty advisor; we are here to assist you. Modern ventilators offer very complex modes than in the past; understanding how these modes work is therefore no trivial task! (Kacmarek, Stoller & Heuer, 2013). Manufacturers of ventilators throw together combinations of features that are difficult to comprehend and there is no standardized nomenclature. It can be baffling. If you are caring for a patient with a mode you are unfamiliar with, consult your respiratory therapy colleagues they are the experts! From your readings, it is important to determine which mode of ventilation is appropriate for varying patients, which parameters are set on the ventilator and which parameters are determined by the patient, and what are the advantages and disadvantages of each mode of ventilation. Also keep in mind how you calculate minute ventilation (f x Vt). Total minute ventilation will vary if you have a mode of ventilation where the patient can generate their own Vt and/or RR. Remember the inverse relationship between minute ventilation and carbon dioxide. The following instructional activity is designed to help you integrate the concepts presented on the various modes of ventilation August 2015 RN Professional Development Centre Page 8

9 LEARNING ACTIVITY 1 1. Mr. B s ventilator settings are VC-A/C with a rate of 12/min, V T 1000mL. The nurse notices that Mr. B triggers the ventilator at an additional rate of 3 breaths/min on his own. The nurse records these findings as follows: RR (f) = Pt rate / A/C (vent) rate = 3 min / 12 min V T = 1000 ml. a. What would the nurse record as Mr. B s minute ventilation? b. What minute ventilation is guaranteed? Because Mr. B developed a respiratory alkalosis on the VC-A/C mode, he is placed on VC-SIMV mode. The nurse records his ventilatory parameters as: SIMV rate = 5/min Client s spontaneous rate = 8/min SIMV V T = 700 ml Client s spontaneous V T = 300 ml c. Calculate Mr. B s minute ventilation. 2. What is the disadvantage of the VC- SIMV mode of ventilation? 3. How does PC A/C differ from pressure support? August 2015 RN Professional Development Centre Page 9

10 Advanced Ventilation/Oxygenation Current research has led clinicians to develop advanced methods of ventilation which are briefly explained in your readings. In clinical, you may see high frequency oscillation (HFO) ventilation. Despite the fact that it is advanced, the premise is the same. Finding a way to oxygenate and ventilate a patient still involves gas exchange in the alveoli and manipulating a patients mean airway (lung expansion) pressure. In patients with hypoxemic respiratory failure that is not corrected with conventional modes of ventilation, clinicians may opt to use ECMO (Extracorporeal Membrane Oxygenation) or in lay terms put the patient on a Heart and Lung machine to oxygenate the blood outside the lungs. In patients with hypercapneic respiratory failure that is not corrected with conventional modes of ventilation, clinicians may opt to use the Novalung ila (interventional lung assist) which facilitates CO 2 removal. HFO, ECMO and the Novalung ila are advanced types ventilation and you are not expected to apply these concepts during this course. Adjuncts to Mechanical Ventilation Adjustments can be made to the modes of ventilation in order to improve the client s oxygenation and/or ventilation. Adjuncts include positive end-expiratory pressure (PEEP), continuous positive airway pressure (CPAP), and pressure support ventilation (PSV). When CPAP and PSV are used in conjunction with other modes of ventilation, they are considered adjuncts and when used alone, they are considered modes. These will be further explained below. Positive End Expiratory Pressure As was previously discussed, when air is trapped in the alveoli it creates a positive pressure in the alveoli at the end of expiration. This is known as auto PEEP or intrinsic peep. However, positive end expiratory pressure (PEEP) can be artificially created by dialling the amount of PEEP desired into the ventilator - called extrinsic PEEP. During mechanical ventilation at the end of inspiration, an expiration valve opens and allows pressure in the alveoli to return to atmospheric pressure. With the application of PEEP, the ventilator s expiratory valve is adjusted in order to create a preset pressure greater than atmospheric pressure in the alveoli at the end of expiration. PEEP improves the client s oxygenation by increasing functional residual capacity (FRC). As well as further inflating previously inflated alveoli; gas volume is increased by recruitment of previously collapsed and partially opened alveoli. By recruiting alveoli and preventing atelectasis, PEEP improves lung compliance and gas exchange. August 2015 RN Professional Development Centre Page 10

11 The goal of PEEP is to maintain and improve oxygenation so the client s F I O 2 can be reduced. There are three clinically used settings for PEEP: 1. Minimal or physiologic - 3 to 5 cm to preserve the client s normal FRC. 2. Moderate - 5 to 15 cm is the most common range of therapeutic PEEP. 3. Maximum - greater than 15 cm which is only beneficial to a small range of clients requiring PEEP. PEEP is applied in increments of pressure until the optimum or best PEEP for the client is determined. Optimum or best PEEP is defined as the PEEP that maximizes oxygen delivery. It has also been defined as a PaO 2 of 60 mmhg mmhg on an F I O 2 < 0.4 while maintaining an adequate cardiac output. Increased amounts of positive pressure in the airways can decrease venous return to the heart and result in a decreased cardiac output. The client s lung compliance can be used to determine optimum PEEP. As PEEP is applied, compliance should improve. However, a point occurs when too much PEEP will cause a decrease in lung compliance. Optimum PEEP coincides with the point just before the client s compliance begins to decrease. Note: PEEP has a major effect on oxygenation and thus, when a client is receiving a PEEP of greater than 5 cm H 2 O, a PEEP valve should be added to the manual resuscitation bag or the use of a closed suctioning system should be considered. Also important to note that when you are weaning a patient, PEEP should be weaned after you have successfully decreased a patient s oxygen below 50%. Remember that PEEP allows alveoli to remain open for adequate gas exchange. Continuous Positive Airway Pressure Ventilation Continuous Positive Airway Pressure Ventilation (CPAP) is the establishment and maintenance of a preset airway pressure, greater than atmospheric pressure, throughout the respiratory cycle during spontaneous breathing. It uses the same principles as PEEP and is commonly delivered noninvasively by a special mask, by T- piece, or by the mechanical ventilator. For example, a client on SIMV mode of ventilation would have PEEP applied to the ventilator-assisted breaths and CPAP applied to the spontaneous breaths. Non-invasive Positive Pressure Ventilation The focus of this lesson certainly has been invasive mechanical ventilation. There will be many instances where intubation can be avoided or not an option clinically. This is well described in the following reading: August 2015 RN Professional Development Centre Page 11

12 Please read the following: Urden, p , Box 21-9 p. 574 Pressure Support Ventilation As you have read, pressure support can be a stand alone mode of ventilation or can in used in conjunction with other modes. Most commonly, it is used in combination with SIMV to support the patients own breaths. Monitoring Compliance and Airway Resistance Acute care specialty nurses commonly monitor the client s peak inspiratory pressure and the plateau pressure readings provided by the ventilator when using volume controlled ventilation. These pressure readings provide valuable information about the client s respiratory status. Peak Inspiratory Pressure Peak inspiratory pressure (PIP) is the pressure required to overcome airway resistance and lung compliance, while delivering a prescribed tidal volume. In the clinical setting, the PIP is measured on the ventilator by the airway pressure manometer previously described. The PIP is the pressure needed to deliver the tidal volume and is measured in cm H 2 O above atmospheric pressure. For example, if a client were receiving a tidal volume of 800 mls, a PIP of 24 cm H 2 0 may be required to deliver this volume. The client s PIP usually varies slightly from breath to breath but markedly will increase when the client s airway resistance increases or as lung compliance decreases. Plateau Pressure Plateau pressure is the pressure needed to inflate alveoli. It is the pressure measurement taken after a breath has been delivered to the client and before exhalation has begun. Plateau pressure is only directly measured when using volume controlled ventilation. August 2015 RN Professional Development Centre Page 12

13 Plateau pressure measures compliance only, and therefore differs from peak inspiratory pressure, which measures both compliance and airway resistance. With plateau pressure there is no flow of gases into the lungs as it is already there. Once the breath is delivered, airway resistance has been overcome, so to hold the breath only the compliance of the lung must be overcome. This would be similar to the pressure needed to keep a balloon inflated. Thus, plateau pressure is usually less than peak inspiratory pressure as the pressure needed to overcome compliance is less than that needed to overcome compliance and resistance. Complications of mechanical ventilation are reduced when plateau pressure is less then cmh2o. The following instructional activity will test your knowledge regarding adjuncts to mechanical ventilation and monitoring the client s compliance and airway resistance. LEARNING ACTIVITY 2 1. Fill in the blanks or circle the correct answer. (a) (b) (c) (d) (e) PEEP affects the alveoli by keeping them open at. PEEP improves gas exchange by increasing. The most common level of therapeutic of PEEP is. Optimum or best PEEP is obtained by achieving the (highest/lowest) pressure that will maintain a PaO 2 of (less than or equal to/greater than or equal to) 60 mmhg while using a F I O 2 less than or equal to (.40/. 60) and an acceptable cardiac. CPAP is a preset airway pressure that is applied to (inspiration/expiration/both inspiration and expiration). Ventilator Settings and Alarms The acute care specialty nurse s main role is to monitor the ventilator settings and alarms to ensure that the client s ventilatory needs are met. The following paragraphs include brief comments regarding the settings and alarms. Settings August 2015 RN Professional Development Centre Page 13

14 1. Mode: The nurse must always check the ventilator to ensure that it is correctly set for the mode (e.g., SIMV, A/C [CMV]), which has been ordered. Simply looking at the RT sheet or Nurses notes is not good enough. It is good practice to directly check the ventilator. 2. Tidal Volume: The nurse routinely measures the client s exhaled tidal volume on the ventilator. A spirometer is used to measure tidal volume when clients are intubated but not on a ventilator (i.e.: T-pieced). Tidal volume is generally measured every hour or as indicated. 3. Respiratory Rate: An accurate respiratory rate includes the preset ventilator breaths and the client triggered breaths. 4. Inspiratory: Expiratory (I: E) ratio: On some ventilators the inspiratory time is set in seconds. The normal inspiratory time is 0.5 to 1.5 seconds. Usually the inspiratory time is set so the I:E ratio is 1:2. In some instances (e.g., COPD), the I:E ratio is set at 1.3:1.5 to facilitate alveolar emptying on expiration. 5. Peak Inspiratory Pressure: A high-pressure limit is set cm H 2 O above the client s peak inspiratory pressure. Some ventilators will stop the inspiratory flow when this high-pressure limit is reached. This serves to detect complications associated with excessive airway pressure. There is also a low-pressure limit, which is set slightly below the client s peak inspiratory pressure. This can indicate improved lung mechanics, hypoventilation, or disconnected ventilator tubing. 6. PEEP: Minimum of of 5cmH2O but is adjusted to a patients condition and hemodynamic stability. 7. F 1 O 2 : Fraction of inspired oxygen. Alarms Ventilator alarms are well explained in Urden p Please review the chart Troubleshooting Ventilator Alarms. Remember patient safety first, when an alarm is ringing, assess and attend to your patient first, then decipher why the alarm rang. August 2015 RN Professional Development Centre Page 14

15 Complications of Mechanical Ventilation Mechanical ventilation is associated with many potential complications. These complications can be placed into three classifications. These include the demands of: (a) positive pressure ventilation, (b) artificial control of ventilation, and (c) an artificial airway. Please read the following: Urden et al p., , There are various interventions, which the nurse can utilize with clients who are anxious and fearful. However, when reassurance and explanations are not effective and the client continues to be inadequately ventilated, pharmacological intervention may be necessary. Morphine sulphate or Fentanyl is commonly given for a sedative effect and to promote relaxation. As well, tranquillizing agents such as Midazolam or anaesthetic agents such as Propofol may be administered to assist with ventilatory management. Occasionally, paralyzing agents such as Vecuronium bromide (Norcuron) are used with clients experiencing severe respiratory disorders. Note: When administering these paralyzing agents, the nurse must remember that they have no sedative effect and that they must be administered in combination with adequate sedation and analgesia. Ventilator-Associated Pneumonia (VAP) The Canadian Patient Safety Initiative, Safer Healthcare Now! has identified prevention of VAP as one of their campaign initiatives. Visit Pager.pdf for updates on initiatives to help improve the safety of our health care system, prevention of VAP being one of the six primary initiatives. The pillars of preventing VAP are: 1. HOB to 45 o when possible but greater than 30 o should be considered. 2. Daily sedation vacation involves an interruption of the patient s current sedation at an appropriate time to assess readiness to wean. At this time, a spontaneous breathing trial may be initiated to assess the patient s readiness to wean. 3. An EVAC tube to drain subglottic secretions. 4. Oral decontamination with Chlorohexidine mouth rinse 5. Initiation of safe enteric nutrition within 24-48hrs of ICU admission. August 2015 RN Professional Development Centre Page 15

16 Additional components of quality evidence based care of a patient on a ventilator include hand hygiene, early mobilization, Deep Vein Thrombosis (e.g., Heparin s/c) and stress ulcer prophylaxis (e.g., Zantac). LEARNING ACTIVITY 3 1. a) Describe the assessment findings that would be assessed during inspection, palpation, and auscultation of the respiratory system with a tension pneumothorax. b) Why does a decrease in cardiac output occur with a tension pneumothorax? c) What intervention is considered a life-saving manoeuvre for clients experiencing a pneumothorax when there is insufficient time to insert a chest tube? 2. List the interventions that could be performed to manage a low cardiac output secondary to the effect of positive pressure ventilation. 3. List the interventions that should be performed if the client is underventilated due to increased airway resistance. 4. List the interventions used when the mechanical ventilator is over ventilating a client. 5. List the interventions used for the person experiencing anxiety and fear related to mechanical ventilation. 6. List the reasons for the potential for infection when the client is mechanically ventilated. Relationship between ABG s and Modes of Ventilation Determining how your patient is tolerating a mode of ventilation is based upon several factors including clinical assessment, pulse oximetry, and ABG interpretation. Most patients who are mechanically ventilated have an arterial line to measure ABG s. Some patients may not have an arterial line and tolerance of ventilation is based upon clinical parameters and SPO2. When an ABG is drawn, it is important to interpret it in relation to the patient s current condition. If changes to the ventilator are made, it is appropriate to wait at least 20 minutes before you would draw an ABG. August 2015 RN Professional Development Centre Page 16

17 Weaning from the Mechanical Ventilator Weaning is a methodical process of decreasing ventilatory support until the client is totally independent of the mechanical ventilator. It can be a rapid process or a very slow process depending on the condition of the client. As you read, take notice of weaning techniques, patient monitoring and complications. Please read the following: Urden et al., p , 1138 While weaning, it is important to monitor trends. It may be normal initially for a slight variation in any of the monitored parameters but any great change should not continue throughout the weaning process. As with any criteria, your patient assessment and tolerance of weaning will give you the most insight into how well your patient is tolerating weaning. LEARNING ACTIVITY 4 1. Why is weaning best initiated in the morning? 2. Can weaning be initiated if the client is on PEEP? 3. List criteria, other than weaning parameters, which must be assessed in order to determine the client s readiness to wean. August 2015 RN Professional Development Centre Page 17

18 Conclusion Basic information has been provided in this unit to assist acute care specialty nurses with decision-making while working with clients with impaired ventilation or oxygenation placed on mechanical ventilators. This lesson described the more common modes and adjuncts used in the acute care specialty setting, however, new mechanical ventilatory approaches are being introduced every day and acute care specialty nurses must constantly update themselves on these new techniques in order to care effectively for their clients. The overall goal of mechanical ventilation is to treat the patients underlying condition and successfully extubate the patient. Acute care specialty nurses, skilled in caring for ventilated clients, are able to provide the client with reassurance and comfort while assessing and implementing measures to help the client tolerate the mechanical ventilator and to prevent complications. Nurses humanize the technical aspect of mechanical ventilation therapy and also provide the encouragement and support ventilated clients require when they are ready to wean. Knowledgeable acute care specialty nurses, working collaboratively with other members of the health care team, are essential to quality care of clients requiring ventilatory support. August 2015 RN Professional Development Centre Page 18

19 Answer Key Learning Activity 1 1. (a) V T x f = V E 1000 ml x 15/min = 15,000 ml/min (15 L/min) (b) V T x f = V E 1000 ml x 12/min = 12,000 ml/min (12 L/min). The controlled breaths. (c) VC-SIMV: V T x f = V E 700 ml x 5/min = 3500 ml/min (3.5 L/min) Clients: V T x f = V E 300 ml x 8/min = 2400 ml/min (2.4 L/min) Total V E = 3500 ml/min ml/min = 5900 ml/min (5.9 L/min) 2. The disadvantage of the VC-SIMV mode of ventilation is that it may increase work of breathing. 3. PC-A/C uses pressure as the controlled parameter and time as the end inspiration signal. Pressure support requires spontaneous client breathing and the client has primary control of the respiratory rate, inspiratory time, inspiratory flow rate, and tidal volumes. The spontaneous generated breaths are supported by a preselected level of inspiratory positive pressure making inspiration easier. Learning Activity 2 (a) End-expiration. (b) Functional residual capacity. (c) 5-15 cm H 2 O. (d) Lowest, greater than or equal to,.40, output. (e) Both inspiration and expiration. August 2015 RN Professional Development Centre Page 19

20 Answer Key Con t Learning Activity 3 1. (a) Inspection: Dyspnea. SOB. Tachypnea. Use of accessory muscles for breathing. Asymmetry of chest (Unilateral lung expansion). Cyanosis. Anxious and complaining of chest pain. Increase in peak and plateau pressures. ABGs indicate hypoxemia and hypercapnia. Palpation: Asymmetry of chest. Tracheal deviation to unaffected side. Subcutaneous emphysema. Auscultation: Diminished or absent breath sounds over affected side. (b) A rapid decrease in cardiac output occurs with a tension pneumothorax due to the increase in intrathoracic pressure compressing the vasculature and heart. (c) Needle thoracentesis is performed using a medium or large bore needle. The needle is inserted into the second or third intercostal space in the midclavicular line on the side where the tension pneumothorax is suspected. 2. Administer intravenous fluids or inotropic agents. Elevate lower extremities 20 to 30 degrees. Check for auto PEEP. Ventilate with settings which best optimize cardiac output (e.g., V T, f, PEEP, inspiratory time, peak flow time, mode). 3. Suction as necessary. Administer bronchodilators. 4. Treat cause (e.g., anxiety, pain, hypoxia, etc). Correct the ventilator settings (e.g., VT or f). Add deadspace tubing between the client and the exhalation port to increase the client s PaCO If the client is fighting the ventilator or out of phase with the ventilator, he/she will need to be manually ventilated. During this time the nurse coaches the client to slow his/her breathing and to aid with relaxation. The ventilator settings may need to be adjusted to optimally meet the client s needs. As well, anxiety and fear can be alleviated if the nurse: (a) establishes an effective method of communication with the client; (b) conveys a calm and reassuring approach; (c) uses clear explanations; (d) maintains a familiar environment; (e) identifies and eliminates factors which increase anxiety and fear; and (f) gives the client control over care. 6. Clients who are mechanically ventilated are at risk for infection due to the following: (a) the presence of an artificial airway bypasses the normal upper airway defence mechanisms; (b) insertion of the artificial airway can introduce contaminants into the lower airway; (c) contamination can occur due to poor aseptic technique during suctioning or use of contaminated equipment. Note: Water which collects in the ventilatory tubing should never be returned to the humidifier as it could contaminate the water in the humidifier; (d) clients who are ventilated are usually physiologically compromised, and e) poor oral hygiene. August 2015 RN Professional Development Centre Page 20

21 Answer Key Con t Learning Activity 4 1. Weaning should begin in the morning so the client is well rested. Weaning is tiring as it increases the work of breathing and exercises the respiratory muscles. 2. Yes, a client can be weaned when they are receiving low levels of PEEP. If the client is on a PEEP higher than 5 cm H 2 O, it indicates that the etiology causing the respiratory disorder has not resolved. Thus, the client continues to require ventilatory support. 3. Clients must be physiologically stable (e.g., hemodynamically stable); they must have normal electrolytes, hematocrit, hemoglobin, acid-base, and fluid balance. Their strength and nutritional status must be satisfactory. They must be psychologically ready to breathe. Ideally, clients should be oriented and able to follow commands. They should be free from pain, well rested, and not experiencing respiratory depression from medications. August 2015 RN Professional Development Centre Page 21

22 BIBLIOGRAPHY Byrum, D. (2009). Mechanical Ventilation. Cruise control for the lungs. Nursing made incredibly easy! 7(5), Kallus, C. (2009). Building a Solid Understanding of Mechanical Ventilation. Nursing, 39(6), Kacmarek, R.K, Stoller, J.K., & Heuer, A.J. (2013). Egan s fundamentals of respiratory care (10 th ed.). St. Louis, MO: Elsevier. Kovacs, G., & Law, J. (2008). Airway management in emergencies. New York: McGraw- Hill Co. McCorstin, P., Cottrell, D.B., Rose, M., & Dwyer, G. (2008). Management of the Mechanically Ventilated Patient in the Emergency Department. Journal of Emergency Nursing, 34(2), 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. August 2015 RN Professional Development Centre Page 22