Mechanical Ventilation PDF

Mechanical Ventilation Pedrosa A. Bautista RN, MAN Alexis Luigi Lorenzo C. Cresencia, RN, MD Objectives: At the end of the session, the students should be able to:  Know the purpose and indication of mechanical ventilation  Differentiate the types of mechanical ventilation  Know th...

Mechanical Ventilation Pedrosa A. Bautista RN, MAN Alexis Luigi Lorenzo C. Cresencia, RN, MD Objectives: At the end of the session, the students should be able to:  Know the purpose and indication of mechanical ventilation  Differentiate the types of mechanical ventilation  Know the different parameters of a mechanical ventilator  Demonstrate proper nursing care of patients on ventilatory support  Mechanical Ventilation Lung ventilation via artificial means (usually by a ventilator) Mechanical Ventilator Positive or negative-pressure breathing device that can maintain ventilation & O2 delivery for a prolonged period Purposes: Maintain/Improve ventilation & tissue oxygenation Decrease work of breathing & improve patient’s comfort  Indications 1.Acute Respiratory Failure due to: i. Mechanical Failure (Neuromuscular diseases e.g. MG, GBS, Poliomyelitis) ii. Musculoskeletal Abnormalities (Chest wall trauma) iii. Infectious Diseases (Pneumonia, TB, COVID19 Infection) 2.Gas Exchange Abnormalities i. Obstructive Lung Disease (Asthma, Chronic Bronchitis, Emphysema) ii. Pulmonary Edema, Atelectasis, Pulmonary Fibrosis iii. General Anesthesia (until recovery from Anesthetic effect) iv. Post-Cardiac Arrest  Indications Clinical Manifestations Apnea / Bradypnea Respiratory distress with confusion Increased work of breathing NOT relieved by other interventions Confusion with need for airway protection Circulatory Shock Controlled hyperventilation Criteria for Ventilatory Support Normal Ventilation Parameters range indicated :A- Pulmonary function studies 10-20 35 > Respiratory rate (breaths/min). 5-15 5< Tidal volume (ml/kg body wt) 65-75 10 < Vital capacity (ml/kg body wt) 75-100 25< Maximum Inspiratory 50-60 10 < Force (cm HO2) FEV1 (mL/kg) 7.35-7.45 7.32 < B- Arterial blood Gases 75-100 55 < pH 35-45 50 > PaO2 (mmHg) PaCO2 (mmHg) Types of Mechanical Ventilators Negative-Pressure Positive-Pressure Ventilators Ventilators  “Iron Lungs”  Delivers gas to the patient  The patient is encased in an under positive-pressure, during iron cylinder that generates a the inspiratory phase negative pressure  ET intubation/Tracheostomy  Older mode of ventilatory usually necessary support  Ventilator Mode Refers to how breaths are delivered to the patient How much the patient will participate in his own ventilatory pattern Each mode is different in determining how much work of breathing the patient must do 2 Modes: Volume Modes Assist—Control (A/C) Synchronized Intermittent Mandatory Ventilation (SIMV) Pressure Modes Pressure-Controlled Ventilation (PCV) Pressure-Support Ventilation (PSV) Continuous Positive Airway Pressure Positive End Expiratory Pressure Non-invasive Bilevel Positive Airway Pressure Ventilation (BiPAP)  Assist-Control (A/C) Mode The ventilator provides the patient with a pre-set tidal volume at a pre-set rate. The patient may initiate a breath on his own, but the ventilator assists by delivering a specified tidal volume to the patient. Client can initiate breaths that are delivered at the preset tidal volume. Client can breathe at a higher rate than the preset number of breaths/minute The total respiratory rate is determined by the number of spontaneous inspiration initiated by the patient plus the number of breaths set on the ventilator.  Assist-Control (A/C) Mode In A/C mode, a mandatory (or “control”) rate is selected. If the patient wishes to breathe faster, he or she can trigger the ventilator and receive a full-volume breath. Often used as initial mode of ventilation When the patient is too weak to perform the work of breathing (e.g., when emerging from anesthesia). Disadvantages: Hyperventilation  Control Mode (CM)/Continuous Mandatory Ventilation (CMV) Ventilation is completely provided by the mechanical ventilator with a preset tidal volume, respiratory rate and oxygen concentration Ventilator totally controls the patient’s ventilation i.e. the ventilator initiates and controls both the volume delivered and the frequency of breath. Client does not breathe spontaneously. Client cannot initiate a breath  Synchronized Intermittent Mandatory Ventilation (SIMV) The ventilator provides the patient with a pre-set number of breaths/minute at a specified tidal volume and FiO2. In between the ventilator-delivered breaths, the patient can breathe spontaneously at his own tidal volume and rate with no assistance from the ventilator. However, unlike the A/C mode, any breaths taken above the set rate are spontaneous breaths taken through the ventilator circuit. The tidal volume of these breaths can vary drastically from the tidal volume set on the ventilator, because the tidal volume is determined by the patient’s spontaneous effort. Synchronized Intermittent Mandatory Ventilation (SIMV) Adding pressure support during spontaneous breaths can minimize the risk of increased work of breathing. Ventilators breaths are synchronized with the patient’s spontaneous breath Used to wean the patient from the mechanical ventilator. Weaning is accomplished by gradually lowering the set rate and allowing the patient to assume more work Pressure-Controlled Ventilation (PCV) The PCV mode is used If compliance is decreased and the risk of barotrauma is high. It is used when the patient has persistent oxygenation problems despite a high FiO2 and high levels of PEEP. The inspiratory pressure level, respiratory rate, and inspiratory– expiratory (I:E) ratio must be selected. In pressure-controlled ventilation the breathing gas flows under constant pressure into the lungs during the selected inspiratory time. The flow is highest at the beginning of inspiration( i.e when the volume is lowest in the lungs). As the pressure is constant, the flow is initially high and then decreases with increasing filling of the lungs. Like volume-controlled ventilation, PCV is time controlled. Pressure-Support Ventilation (PSV) The patient breathes spontaneously while the ventilator applies a pre-determined amount of positive pressure to the airways upon inspiration. Pressure support ventilation augments patient’s spontaneous breaths with positive pressure boost during inspiration i.e. assisting each spontaneous inspiration. Helps to overcome airway resistance and reducing the work of breathing. Indicated for patients with small spontaneous tidal volume and difficult to wean patients. Patient must initiate all pressure support breaths. Pressure-Support Ventilation (PSV) Pressure support ventilation may be combined with other modes such as SIMV or used alone for a spontaneously breathing patient. The patient’s effort determines the rate, inspiratory flow, and tidal volume. In PSV mode, the inspired tidal volume and respiratory rate must be monitored closely to detect changes in lung compliance. It is a mode used primarily for weaning from mechanical ventilation.  Continuous Positive Airway Pressure (CPAP) Constant positive airway pressure during spontaneous breathing CPAP allows the nurse to observe the ability of the patient to breathe spontaneously while still on the ventilator. CPAP can be used for intubated and non-intubated patients. It may be used as a weaning mode and for nocturnal ventilation (nasal or mask CPAP) Positive End Expiratory Pressure (PEEP) Positive pressure applied at the end of expiration during mandatory / ventilator breath positive end-expiratory pressure with positive-pressure (machine) breaths  Uses of CPAP & PEEP Prevent atelectasis or collapse of alveoli Treat atelectasis or collapse of alveoli Improve gas exchange & oxygenation Treat hypoxemia refractory to oxygen therapy (prevent oxygen toxicity) Treat pulmonary edema (the pressure helps in the expulsion of fluids from the alveoli)  Non-invasive Bilateral Positive Airway Pressure Ventilation (BiPAP) BiPAP is a noninvasive form of mechanical ventilation provided by means of a nasal mask or nasal prongs, or a full-face mask. The system allows the clinician to select two levels of positive-pressure support: An inspiratory pressure support level (referred to as IPAP) An expiratory pressure called EPAP (PEEP/CPAP level). Lungs  Common Ventilator Settings Parameters/Controls Fraction of inspired oxygen (FIO2) Tidal Volume (VT) Peak Flow/ Flow Rate Respiratory Rate/ Breath Rate / Frequency ( F) Minute Volume (VE) I:E Ratio (Inspiration to Expiration Ratio) Sigh Fraction of Inspired Oxygen (FiO2) The percent of oxygen concentration that the patient is receiving from the ventilator. (Between 21% & 100%) Room air has 21% oxygen content Initially a patient is placed on a high level of FIO2 (60% or higher). Subsequent changes in FIO2 are based on ABGs and the SaO2. In adult patients the initial FiO2 may be set at 100% until arterial blood gases can document adequate oxygenation. An FiO2 of 100% for an extended period can be dangerous (oxygen toxicity) but it can protect against hypoxemia For infants, and especially in premature infants, high levels of FiO2 (>60%) should be avoided. Usually, the FIO2 is adjusted to maintain an SaO2 of greater than 90% (roughly equivalent to a PaO2 >60 mm Hg)  Oxygen Toxicity a concern when an FIO2 of greater than 60% is required for more than 25 hours Signs and symptoms of oxygen toxicity : 1- Flushed face 2- Dry cough 3- Dyspnea 4- Chest pain 5- Tightness of chest 6- Sore throat  Tidal Volume (VT) The volume of air delivered to a patient during a ventilator breath. The amount of air inspired and expired with each breath. Usual volume selected is between 5 to 15 ml/ kg body weight) In the volume ventilator, Tidal volumes of 10 to 15 mL/kg of body weight were traditionally used. the large tidal volumes may lead to (volutrauma) aggravate the damage inflicted on the lungs For this reason, lower tidal volume targets (6 to 8 mL/kg) are now recommended.  Peak Flow / Flow Rate The speed of delivering air per unit of time and is expressed in liters per minute. The higher the flow rate, the faster peak airway pressure is reached and the shorter the inspiration; The lower the flow rate, the longer the inspiration. Respiratory Rate/ Breath Rate/ Frequency (F) The number of breaths the ventilator will deliver/minute (10-16 b/m). Total respiratory rate equals patient rate plus ventilator rate. The nurse double-checks the functioning of the ventilator by observing the patient’s respiratory rate. For adult patients and older children: With COPD A reduced tidal volume A reduced respiratory rate For infants and younger children: A small tidal volume Higher respiratory rate  Minute Volume (VE) The volume of expired air in one minute. Respiratory rate times tidal volume equals minute ventilation VE = (VT x F) In special cases, hypoventilation or hyperventilation is desired In a patient with COPD Baseline ABGs reflect an elevated PaCO2 should not hyperventilated. Instead, the goal should be restoration of the baseline PaCO2. These patients usually have a large carbonic acid load and lowering their carbon dioxide levels rapidly may result in seizures. In a patient with head injury Respiratory alkalosis may be required to promote cerebral vasoconstriction, with a resultant decrease in ICP. In this case, the tidal volume and respiratory rate are increased (hyperventilation) to achieve the desired alkalotic pH by manipulating the PaCO2. I:E Ratio (Inspiration to Expiration Ratio) The ratio of inspiratory time to expiratory time during a breath (Usually = 1:2) Sigh A deep breath. A breath that has a greater volume than the tidal volume. It provides hyperinflation and prevents atelectasis. Sigh volume: Usual volume is 1.5 –2 times tidal volume. Sigh rate/ frequency: Usual rate is 4 to 8 times an hour.  Peak Airway Pressure In adults if the peak airway pressure is persistently above 45 cmH2O, the risk of barotrauma is increased, and efforts should be made to try to reduce the peak airway pressure. In infants and children, it is unclear what level of peak pressure may cause damage. In general, keeping peak pressures below 30 is desirable. Pressure Limit On volume-cycled ventilators, the pressure limit dial limits the highest pressure allowed in the ventilator circuit. Once the high-pressure limit is reached, inspiration is terminated. Therefore, if the pressure limit is being constantly reached, the designated tidal volume is not being delivered to the patient. Sensitivity (Trigger Sensitivity) The sensitivity function controls the amount of patient effort needed to initiate an inspiration Increasing the sensitivity (requiring less negative force) decreases the amount of work the patient must do to initiate a ventilator breath. Decreasing the sensitivity increases the amount of negative pressure that the patient needs to initiate inspiration and increases the work of breathing. The most common setting for pressure sensitivity are -1 to -2 cm H2O The more negative the number the harder it is to breath.  Ventilator Alarms Mechanical ventilators comprise audible and visual alarm systems, which act as immediate warning signals to altered ventilation. Alarm systems can be categorized according to volume and pressure (high and low). High-pressure alarms warn of rising pressures. Low-pressure alarms warn of disconnection of the patient from the ventilator or circuit leaks. Complications of Mechanical Ventilation I- Airway Complications II- Mechanical complications III- Physiological Complications IV- Artificial Airway Complications  Airway Complications 1- Aspiration 2- Decreased clearance of secretions 3- Nosocomial or ventilator-acquired pneumonia Mechanical Complications 1- Hypoventilation with atelectasis with respiratory acidosis or 4- Alarm “turned off” hypoxemia. 5- Failure of alarms or 2- Hyperventilation with hypocapnia and respiratory alkalosis ventilator 3- Barotrauma 6- Inadequate a- Closed pneumothorax nebulization or b- Tension pneumothorax humidification c- Pneumomediastinum 7- Overheated inspired d- Subcutaneous emphysema air, resulting in III- Physiological IV- Artificial Airway Complications Complications 1- Fluid overload with A- humidified air and sodium Complications related to Endotracheal Tube: chloride (NaCl) retention 1- Tube kinked or plugged 2- Depressed cardiac 2- Rupture of piriform sinus function and hypotension 3- Tracheal stenosis or 3- Stress ulcers tracheomalacia 4- Paralytic ileus 4- Mainstem intubation with contralateral (located on or 5- Gastric distension affecting the opposite side of the 6- Starvation lung) lung atelectasis 7- Dyssynchronous 5- Cuff failure breathing pattern 6- Sinusitis 7- Otitis media  IV – Artificial Airway Complications B- Complications related to Tracheostomy tube:- 1- Acute hemorrhage at the site 2- Air embolism 3- Aspiration 4- Tracheal stenosis 5- Erosion into the innominate artery with exsanguination 6- Failure of the tracheostomy cuff 7- Laryngeal nerve damage 8- Obstruction of tracheostomy tube 9- Pneumothorax 10- Subcutaneous and mediastinal emphysema 11- Swallowing dysfunction 12- Tracheoesophageal fistula 13- Infection 14- Accidental decannulation with loss of airway  Nursing Care of Patients on Mechanical Ventilation Assessment: 1- Assess the patient 2- Assess the artificial airway (tracheostomy or endotracheal tube) 3- Assess the ventilator Nursing Interventions 1-Maintain airway patency & 8 - Maintain safety oxygenation 9 - Provide psychological support 2- Promote comfort 10 - Facilitate communication 3- Maintain fluid & electrolytes 11- Provide psychological support & balance information to family 4- Maintain nutritional state 12- Responding to ventilator alarms /Troubleshooting ventilator alarms 5- Maintain urinary & bowel elimination 13- Prevent nosocomial infection 6- Maintain eye , mouth and 14- Documentation  Responding to Alarms If an alarm sounds, respond immediately because the problem could be serious. Assess the patient first, while you silence the alarm. If you can not quickly identify the problem, take the patient off the ventilator and ventilate him with a resuscitation bag connected to oxygen source until the physician arrives. A nurse or respiratory therapist must respond to every ventilator alarm. Alarms must never be ignored or disarmed. Ventilator malfunction is a potentially serious problem. Nursing or respiratory therapists perform ventilator checks every 2 to 4 hours, and recurrent alarms may alert the clinician to the possibility of an equipment-related issue. When device malfunction is suspected, a second person manually ventilates the patient while the nurse or therapist looks for the cause. If a problem cannot be promptly corrected by ventilator adjustment, a different machine is procured so the ventilator in question can be taken out of service for analysis and repair by technical staff.  Causes of Ventilator Alarms High pressure alarm Increased secretions Kinked ventilator tubing or endotracheal tube (ETT) Patient biting the ETT Water in the ventilator tubing. ETT advanced into right mainstem bronchus. Low pressure alarm Disconnected tubing A cuff leak A hole in the tubing (ETT or ventilator tubing) A leak in the humidifier Oxygen alarm The oxygen supply is insufficient or is not properly connected.  Causes of Ventilator Alarms High respiratory rate alarm Episodes of tachypnea, Anxiety, Pain, Hypoxia, Fever. Apnea alarm During weaning, indicates that the patient has a slow Respiratory rate and a period of apnea. Temperature alarm Overheating due to too low or no gas flow. Improper water levels  Methods of Weaning 1- T-Piece trial It consists of removing the patient from the ventilator and having him / her breathe spontaneously on a T-tube connected to oxygen source. During T-piece weaning, periods of ventilator support are alternated with spontaneous breathing. The goal is to progressively increase the time spent off the ventilator. 2- Synchronized Intermittent Mandatory Ventilation ( SIMV) Weaning SIMV is the most common method of weaning. It consists of gradually decreasing the number of breaths delivered by the ventilator to allow the patient to increase number of spontaneous breaths T-Piece Trial  Methods of Weaning 3- Continuous Positive Airway Pressure ( CPAP) Weaning When placed on CPAP, the patient does all the work of breathing without the aid of a back up rate or tidal volume. No mandatory (ventilator-initiated) breaths are delivered in this mode i.e., all ventilation is spontaneously initiated by the patient. Weaning by gradual decrease in pressure value 4- Pressure Support Ventilation (PSV) Weaning The patient must initiate all pressure support breaths. During weaning using the PSV mode the level of pressure support is gradually decreased based on the patient maintaining an adequate tidal volume (8 to 12 mL/kg) and a respiratory rate of less than 25 breaths/minute. PSV weaning is indicated for :- - Difficult to wean patients - Small spontaneous tidal volume.  Weaning Readiness Criteria Awake and alert Hemodynamically stable, adequately resuscitated, and not requiring vasoactive support Arterial blood gases (ABGs) normalized or at patient’s baseline - PaCO2 acceptable - PH of 7.35 – 7.45 - PaO2 > 60 mm Hg - SaO2 >92% - FIO2 ≤40% Positive end-expiratory pressure (PEEP) ≤5 cm H2O F < 25 / minute Vt 5 ml / kg VE 5- 10 L/m (f x Vt) VC > 10- 15 ml / kg  Weaning Readiness Criteria Chest x-ray reviewed for correctable factors; treated as indicated, Major electrolytes within normal range, Hematocrit >25%, Core temperature >36°C and 20 beats /min. or heart rate > 110b/m, Sustained heart rate >20% higher or lower than baseline Increase or decrease in blood pressure of > 20 mm Hg Systolic blood pressure >180 mm Hg or 10 above baseline or > 30 Sustained respiratory rate greater than 35 breaths/minute Tidal volume ≤5 mL/kg, Sustained minute ventilation