Mechanical Ventilation Prepared by : Bayan Kaddourah RN,MHM. GICU Clinical Instructor 1
Definition Is a supportive therapy to facilitate gas exchange. Most ventilatory support requires an artificial airway. Ventilators deliver gas to the lungs using positive pressure at a certain rate. The amount of gas delivered d can be limitedit by time, pressure or volume. The duration can be cycled by time, pressure or flow. 2
Goal To maintain an alveolar ventilation appropriate p for the pt s metabolic needs. Correct hypoxemia and maximize O2 transport. Prevent or treat atelectasis. Reduce the work of breathing in critically i ill patients. 3
Indications i Respiratory Failure Apnea / Respiratory Arrest inadequate ventilation (acute vs. chronic) inadequate oxygenation Worsening of an ABG s ; pao2 < 60, PACO2 > 50 and PH < 7.25 4
Indications i Cardiac Insufficiency eliminate work of breathing reduce oxygen consumption Neurologic dysfunction central hypoventilation/ frequent apnea patient comatose, GCS < 8 inability to protect airway 5
Non invasive methods of ventilation Donot require an artificial airway ( ETT or tracheostomy). Types: 1. Negative pressure ventilation:( iron lung or chest cuirass) Is used for patients with respiratory failure who require assisted ventilation for short periods. It encloses the thorax of the patients, and creates a cylindrical increase and decrease in the pressure around the chest wall and causes 6 brief changes in the intrathoracic pressure.
Iron Lung 7
Non invasive methods of ventilation Candidates of negative pressure ventilation: - central sleep apnea. - neuromuscular disorders who requires ventilatory support at night. 8
Noninvasive positive pressure ventilation Used to manage chronic respiratory failure or acute respiratory insufficiency, expected to resolve quickly. Post extubation hypercapnia or pulmonary edema. those who refuses intubation. Such as : CPAP and BIPAP. 9
Invasive methods of ventilation. ( positive pressure ventilation) It requires an artificial airway. Used to force air into the lungs. It has 2 categories; - volume targeted ventilation. - Pressure targeted ventilation. - ventilators with flexible capacities ( alters mode of delivery according to pt. respiratory parameters) 10
A- volume targeted modes. 1. Controlled ventilation: Delivers preset tidal volume( VT) at a preset respiratory rate. It ventilates regardless of inspiratory effort. Locks out pt. effort tto breathe. Used for pt s with no inspiratory efforts, such as pt s with cervical spine injuries, paralyzed and so on. Rarely used due to the presence of A/C mode 11
CMV 12
2-Assist control (A/C) It delivers a preset VT whenever the pt. exerts a negative inspiratory effort. A preset RR regardless of spontaneous effort. Decreases WOB. Useful in pt s who are unable to sustain a normal VT. Preserve pulmonary muscle tone and reduces ventilator dyssynchrony ( fighting). 13
Complications ( A/C) Respiratory alkalosis, especially if pt s spontaneous respiratory rate is too high. It is treated by adjusting the tidal volume, or sedate the patient, or change to SIMV. 14
A/CV 15
3-Synchronized Intermittent Mandatory ventilation (SIMV) Delivers preset VT at a preset RR. It permits the pt. to breathe spontaneously at his or her own RR and depth between the ventilator breaths. The preset breaths are synchronized with the patient spontaneous efforts. Helps to prevent respiratory muscles weakness and hyperventilation that occur with A/C. Ordered as a method for weaning. N.B: if spontaneous respiration increases leads to muscle fatigue. 16
SIMV 17
B- Pressure Targeted modes of mechanical ventilation It provides ventilation based on preset inspiratory pressure levels. Tidal volume is controlled by preset inspiratory pressure. Once a breath is triggered, a rapid inspiratory flow of gas occurs until the set pressure is reached. The received VT is determined by the pt. lung compliance 18
1- Pressure support ventilation (PSV) A preset level of positive pressure is applied for the duration of a spontaneous breath. It augments spontaneous VT and decreases the WOB during spontaneous breathing. It increases pt comfort. It facilitate weaning. Used to enhance other modes or as a stand alone mode. Typically used in the SIMV mode to promote weaning. 19
Airway pressure Release ventilation Is a new mode of ventilation that provides two levels of CPAP during the inspiratory and expiratory phases of breathing. Requires spontaneous respiration. Inverse I:E ratio. Provides adequate oxygenation while lowering peak inspiratory airway pressure. Using High Peep (20-30 cm H2o) and low peep ( 0-5 cmh2o),t high up to 6 sec and T low up to 0.5 sec. Indicated for pt s with decreased lung compliance (ARDS),ALI. Helps in decreasing the use of INOTROPES. No clinical evidence. Not to be used for deep coma or paralyzed patients. 20
Settings for mechanical ventilation 1- Positive End Expiratory Pressure : Added to mechanically assisted breaths. Higher than atmospheric pressure keeps the patient s airway open at the end of expiration. Increases functional residual capacity. Increases oxygenation by preventing collapse of small airways and maximizing number of alveoli available for gas exchange. NL physiological peep is 3-5 cm H2O. It is ordered to decrease FiO2. 21
PEEP (con t) Complications of PEEP: Decrease in cardiac output due to decrease in venous return. Volutrauma. Increase ICP due to impairment of venous return from the head. Reduced renal function due to decrease in renal blood flow. NB:Auto N.B: PEEP : when residual pressure in the alveoli at the end of exhalation cannot escape the lung. It occurs mostly when the ventilator delivers a prolonged inspiration as inverse -ratio ventilation. 22
2- Tidal volume Is the amount of air delivered with each preset breath. Recent amount for calculating VT is 4-8 ml/kg, thus providing adequate ventilation while reducing complications. When lower VT levels are administered, pt s Co2 levels may rise leading to Permissive hypercapnia That hypercapnia reduces peak air pressure and may reduce volutrauma. It is C.I in patients with head injuires because it ȋ ICP. 23
3- Respiratory Rate Is the frequency of breaths (f) set to be delivered by the ventilator to the patient. RR x VT = minute ventilation. minute ventilation is to be set according to the body surface area : 4 x BSA in men and 3.5 x BSA in females. 24
4- Fraction of inspired oxygen(fio2) is the fraction or percentage of inspired oxygen delivered to the pt. by the ventilator. FiO2 may be set from 21 % - 100%. It is adjusted based on ABG s value, pulse oxymeter reading and clinical manifestations. 25
5- Peak Inspiratory Pressure (PIP) Is the maximal pressuring that occurs during ventilation and is usually measured at the end of expiration. It is necessary to ventilate the patient, it overcome increases in airway resistance (secretions, biting tube), and decrease lung compliance (ARDS). 26
6- Sensitivity Determines the amount of patient effort needed to initiate an assisted breath. It is normally set at -1 cm H2O. If the sensitivity is too low, So pt. must generate more work to trigger gas flow. If it is set too high h,so pt- ventilator dyschrony may occur. 27
7- Inspiratory to- Expiratory Ratio In spontaneous ventilation, inspiration is shorter than expiration. For mechanically ventilated patients I:E ratio is usually set at 1:2. 28
8- Sigh Is a mechanically set breath with greater volume than the preset VT. It is usually 1.5 2.0 x VT. It s rationale is to prevent atelectasis. It is not used if higher VT settings are ordered. d 29
9- Humidification and thermoregulation It is essential to maintain the inspired gas at 37c and 100 % relative humidity. Two mechanisms of humidification are available: 1. The dry inspired gas pass through water based humidification system. 2. Attach a heat moisture exchanger, that acts as an artificial nose. 30
Alarm Systems The nurse must be familiar with the alarm functions of each ventilator. can be categorized according to volume, pressure, high and low. 1. Low pressure alarm = pt is disconnected from the ventilator. 2. High pressure alarm = rising pressures. 3. Low volume alarms = warns of leaks. 4. Electrical failure alarm. 5. Apnea alarm = ventilator does not detect spontaneous respiration. it alarms if the pt is ventilated at a very low rate N.B: Alarms must never be ignored or disarmed. 31
complications 1. Aspiration. 2. Ventilator malfunction. 3. Barotrauma. 4. Decreased C.O. 5. Water imbalance. 6. Immobility. 7. G.I problems. 8. Muscle weakness. 9. Infection. 32
Complication( con t) 10. Tracheal damage. 11. Damage to oral or nasal mucosa. 12. Respiratory alkalosis or acidosis. 13. Dependence. 14. Psychosocial problems. 33
Care of Patient on Mechanical Ventilation 1. Assess oxygenation status by doing the followings: Auscultate breath sounds. Note rate and depth of respirations. Assess L.O.C. Note any cardiac dysrhythmias and symmetrical chest movement. 2. Continously monitor oxygen saturation ti with pulse oximeter. 3. Check ventilator settings. 34
4. Check ventilator alarms for correct function. 5. Auscultate breath sounds every 2 hours. 6. Suction patient tas needed. d 7. Assess lips and tongue for pressure ulcer. 8. Rotate tube placement from side to side of the mouth. 9. Monitor fluid status on hourly basis. 10. Check ventilator tubing for obstruction 11. Never to ignore any ventilator alarms. 35