Mechanical Ventilation Flashcards
What is an example of negative pressure ventilation?
Iron Lung
What are some examples of positive pressure ventilation?
Machine ventilator
CPAP
Bagger
Another person
Pressure created outside of the lung for inhalation
Why might mechanical ventilation be required?
- Control a patient’s respirations during surgery
- to oxygenate the blood when the patient’s mechanical ventilation efforts are inadequate
- rest the respiratory muscles
What are some indications for endotracheal intubation and mechanical ventilation?
- Continuous decrease in oxygenation (PaO2)
- Increase in arterial carbon dioxide levels (PaCo2)
- Persistent acidosis
- Conditions such as thoracic or abdominal surgery, drug overdose, neromuscular disorders, inhalation injury, COPD, multiple trauma, shock, multisystem failure, and coma may all lead to resp failure
What are clinical manifestations that indicate mechanical ventilation?
- apnea or bradypnea
- respiratory distress with confusion
- Increased work of breathing not relieved by other interventions
- Confusion with need for airway protection
- Circulatory shock
- Controlled hyperventilation (e.g., patient with a severe head injury)
What are three types of positive-pressure ventilators?
- Volume-cycled
- pressure-cycled
- high-frequency oscillatory support
What are key steps to respiratory assessment?
- History
- Inspection
- Auscultation
- Palpation
- SpO2 monitoring
- ABG (basic)
What is ventilation?
Movement of air in and out of airways
What are examples of invasive airways?
- Oral
- Nasal
- Tracheal
What are examples of non-invasive airways?
- OPA (oropharyngeal airway)
- NAP (nasopharyngeal airway)
What are the characteristics of a volume-cycled ventilator?
- Deliver a pre-set volume of air with each inspiration
- Exhalation occurs passively
- Volume of air is relatively constant, ensuring consistent, adequate breaths despite varying airway pressures
What is a disadvantage of a volume-cycled ventilator?
Patient may experience barotrauma because the pressure required to deliver the breaths may be excessive
What is barotrauma?
Trauma that causes damage to the alveolar capillary membrane and air to leak into the surrounding tissues.
How does a pressure-cycled ventilator work?
When a pressure-cycled ventilator cycles on, it delivers a flow of air (inspiration) until it reaches a pre-set pressure, and the cycles off, and expiration occurs passively.
What is a major limitation of pressure-cycled ventilators?
The volume of air or oxygen can vary as the patient’s airway resistance or compliance changes. As a result, the tidal volume delivered may beinconsistent, possible compromising ventilation.
How is acute respiratory failure (ARF) clinically defined?
PaCO2 greater than 50 mmHg
pH less than 7.30
and/or
PaO2 less than 60 mmHg
What is the most common indication for ventilator support?
Acute ventilatory failure. Inability of the lungs to maintain adequate alveolar ventilation. Diagnosed on the basis of the acid-base balance it creates: acute respiratory acidosis.
What is shunting?
Refers to the state in which pulmonary capillary perfusion is normal but alveolar ventilation is lacking. Pulmonery capillary blood can’t pick up oxygen from the nonfunctioning alveolar unit; if there are too many non-functioning units, there can be a decrease in SaO2, causing hypoxemia.
What are some common tests to assess pulmonary function?
vital capacity, negative inspiratory force, and respiration rate.
What respiratory rate significantly increases the work of breathing, leading to respiratory muscle fatigue?
35 breaths per minute
What is the purpose of the cuff at the distal end of the endotracheal tube?
When inflated, the tube seals the space between the tube and the trachea so air is directed through the tube into the lower airway, ensuring a predictable volume or pressure
What does the diameter of the ET tube reflect?
the diameter of the inside lumen
Which artificial airway is more commonly used on a patient who requires prolonged intubation because of failure to wean from the ventilator?
tracheostomy
What is tidal volume?
Amount of air that moves in and out of the lungs in one normal breath.
What is the range for normal tidal volume?
500 - 800 mL in an adult
When is there an increased risk for lung injury during mechanical ventilation?
When tidal volume is high or peak alveolar pressure increases
What is volutrauma?
Overstretching of the alveolar cells triggers release of inflammatory mediators and stimulation of the inflammatory response. Volutrauma increases the permeability of the lung’s microvasculature, which may result in pulmonary edema.
What is FiO2 (fraction of inspired oxygen)?
The % (or decimal) of O2 delivered to the patient. A mechanical ventimator is able to deliver a wide range of oxygen, from 0.21 - 1 (21% - at sea level room air is 21% - to 100%)
What is minute ventilation?
Amount of air that moves in and out of the lungs in 1 minute.
How is minute ventilation measured?
Tidal volume x respiratory rate
What is positive end expiratory pressure?
Set to provide pressure @ the end of expiration, to prevent alveolar collapse and improves patient PaO2 without increasing FiO2
What is peak airway pressure? (aka peak inspiratory pressure)
The highest level of pressure applied to the lungs during inspiration - measured with all modes of ventilation
What are some options for non-invasive intermittent positive pressure ventilation (NIPPV)?
oronasal mask, nasal mask, nasal pillows, full-face masks, helmets, and large cannula-type devices
What are features and uses of a CPAP?
- Mode of mechanical assistance that provides a continuous level of positive airway pressure for a spontaneously breathing person
- Does not provide assisted ventilation on inspiration
- improves oxygenation by opening alveoli and is used in pressures ranging from 5 to 20 cm H2O
- Delivered by a special flow generator
- Most commonly used to treat obstructive sleep apnea
What kind of alarms may sound when using mechanical ventilation?
- Pressure (high/low)
- Volume (high/low)
- Frequency (high/low)
- Apnea
- MV (minute ventilation)
Which mode is more of a weaning mode?
pressure support
Which types of support are used more with decreased levels of consciousness?
volume control and pressure control
When an alarm goes off, what is important to check first?
Always check the patient before the ventilator
What assessment and interventions are in place for a patient on mechanical ventilation?
Clinical
* Vital signs
* ABGs - ventilator changes based on findings
* Work of breathing
* Full respiratory assessment
Mode: settings, measurement
Interventions
* Suctioning
* Mouth care
* Medications (sedation/comfort/anxiety/paralytics)
* Communication
* PT
* Mobilization (positioning)
* Nutrition (for healing)
What are cardiovascular complications of mechanical ventilation?
Positive pressure ventilation reduces CO by decreasing venous return in three major ways
1) external pressure on the inferior vena cava decreases blood flow into the right atrium
2) Right ventricular afterload increases due to increased lung volume
3)The pressure being exerted on the alveoli increases pulmonary vascular resistance and right ventricular afterload
Decreased CO results in hypotension
Includes lung and thoracic compliance ,airway resistance, and patients’ volemic state.
What cardiovascular assessment alterations should accompany a patient on mechanical ventilation?
Continuous monitoring of V/S – as per policy
Decreased BP (in presence of hypovolemia and heart failure)
Compensation: Normal BP, increased HR and increased SVR
Monitoring I&O to ensure adequate hydration
Minute ventilation and tidal volume
Monitor lytes and acid base balance (to assess for dysrhythmias)
What neurovascular complications can be seen in a patient on mechanical ventilation?
- change in neurovascular status: increased ICP and decreased cerebral perfusion pressure (CPP = MAP - ICP)
- If CPP drops too low, cerebral hypoxia can result
What pulmonary complications can be seen in a patient on mechanical ventilation?
- Altered ventilation and perfusion
- Barotrauma and volutrauma - can manifest itself as pneumothorax, subcutaneous emphysema, pneumomediastinum
- Oxygen toxicity - damages endothelial lining of the lungs, decreases alveolar macrphage activity, decreases mucus and surfactant production
- Ventilator-associated pneumonia (common when ventilated for more than 48 hours
What are renal complications associated with patients on mechanical ventilation?
- decreased urinary output
- Factors contribute to decreased renal function: redistribution of renal blood flow
- Hormonal alterations (May stimulate the release of ADH, renin, aldosterone, atrial natriuretic factor and catecholamines, which may affect renal blood flow and renal function)
What gastrointestinal complications are associated with patients on mechanical ventilation?
- TPN - risk of malnutrition
- Constipation risk - laxatives and rectal tube
- Decreased peristalsis - loss of GI function
- Hepatic dysfunction due to increased pressure on liver
- Stress induced ulcers major risk factor with mechanical ventilation >48h, gastric hyperacidity - GI bleeding
- Results from episode of tissue hypoxia with resp failure
- Exhibited through black tarry stools
- If ulcer in stomach NG aspirate my appear bright red
- Decreased hematocrit from bleeding
- Acalculous cholecystitis
- GI hypomotility
What psychological complications are associated with patients on mechanical ventilation?
Anxiety and pain
Sleep pattern disturbance
Depression/Delirium/Delusion
Loneliness
Frustration (inability to vocalize)
Communication - inability to vocalise
Confusion
Impaired social support
Disturbed body image
Amnesia
Memory loss
Anger
Despair
What are some artificial airway complications?
Airway trauma
Local tissue ischemia
Bypassing normal upper airway defenses that warm and humidify the air
Nasal or oral damage
Cuff trauma
Tracheostomy
* tracheomalcia (weakening or erosion of the tracheal cartilage)
* tracheal stoma erosion
* accidental decannulation
What is involved in rapid-weaning from a mechanical ventilator?
Rapid weaning (short term)
Patient placed on spontaneous breathing mode (C P A P, P S V, or T-piece) and provided with humidified oxygen
What are some considerations in the weaning process?
- Order
- Patient participation/readiness (LOC, sedation, strength)
- RRT
- Previous experience/attempts
What are the characteristics of synchronous intermittent madatory ventilation (SIMV)
- Patient spontaneously breathes through the ventilator circuit, maintaining much of the work of breathing
- Interspersed at regular intervals, the ventilator provides a preset ventilator breath
Why might a low exhaled volume alarm go off?
- decreased or low tidal volume (air that moves in and out in one breath)
- Might be a leak in the cuff
