Mechvent Flashcards by JA S

What are the principal indications for mechanical ventilation in critically ill patients?

Inadequate respiratory effort due to:
* Sustained increase in respiratory and metabolic demand
* Pneumonia
* Asthma
* Lung injury
* Sepsis
* Metabolic acidosis
* Neuromuscular failure
* Acute or chronic paresis
* Fatigue
* To recruit lung units
* Improve oxygenation

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What is a key indication for using mechanical ventilation during general anesthesia?

Respiration is inhibited or blocked by deep sedation, opioids, or neuromuscular blockade

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What is the role of mechanical ventilation in airway protection?

Protects the airway when patency is diminished due to obstruction from edema or tumor, and when at risk from aspiration of gastric contents or hemorrhage

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What are the main components of a mechanical ventilator?

Includes:
* Gas delivery system
* Breath controller
* Mode controller
* Demand sensor

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What are the three elements involved in the delivery of tidal volume (VT) by a ventilator?

Breath triggering
Gas flow control (pressure or volume targeted)
Cycling off to permit exhalation

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What is the function of effort sensors in mechanical ventilation?

Detect changes in pressure or flow to govern initiation or termination of inspiration

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What does the term ‘positive end-expiratory pressure’ (PEEP) refer to?

A pressure maintained in the airway during expiration to recruit atelectatic lung units and prevent collapse

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What is volume control ventilation?

A mode where the tidal volume is the defined variable, delivering constant flow until the desired volume is achieved

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What are the advantages of volume control ventilation?

Guarantees tidal volumes
More stable minute volume
Appropriate for tight control of PaCO2
Reliable over changing pulmonary characteristics

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What are the disadvantages of volume control ventilation?

Lower mean airway pressure
Poor recruitment in units with poor compliance
Unstable mean airway pressure in the presence of leaks
Potential for patient-ventilator dyssynchrony

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What is pressure control ventilation?

A mode where inspiratory pressure is the control variable maintained during inspiration

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What are the advantages of pressure control ventilation?

Increased mean airway pressure
Improved oxygenation
Better alveolar recruitment
Protection against barotrauma
Improved patient comfort

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What are the disadvantages of pressure control ventilation?

Tidal volume is dependent on respiratory compliance
Difficult to achieve tight control of PaCO2
Risk of volutrauma
High initial inspiratory flow may breach pressure limits

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What is pressure support ventilation?

A mode where the patient initiates the breath, and the ventilator provides support until flow decreases to a set threshold

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What is continuous mandatory ventilation (CMV)?

A mode where the ventilator provides all the work of breathing without patient input

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What is assist control (AC) ventilation?

A mode where the patient can trigger breaths, but the ventilator completes each initiated breath

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What is intermittent mandatory ventilation (IMV)?

A mode that provides mandatory breaths while allowing the patient to breathe spontaneously without assistance

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What does synchronized intermittent mandatory ventilation (SIMV) involve?

A mode that synchronizes mandatory breaths with the patient’s spontaneous efforts

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What is noninvasive ventilation (NIV)?

Mechanical support delivered through interfaces without endotracheal intubation

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What are the contraindications for noninvasive ventilation?

Cardiopulmonary arrest
Inability to protect the upper airway
Poor neurological status
Shock requiring escalating vasopressors
Upper gastrointestinal bleed
Facial injuries

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What are common complications of noninvasive ventilation?

Gastric distension
Facial skin breakdown
Nasal/oral mucosal damage
Eye irritation and trauma

What is high-frequency ventilation (HFV)?

A mode that applies continuous distending pressure and superimposes small tidal volumes at rapid rates

What is the main type of high-frequency ventilation used?

High-frequency oscillatory ventilation (HFOV)

What is High-Frequency Ventilation (HFV)?

Applies continuous distending pressure to maintain lung expansion, and superimposes small VTs at a rapid rate

The main type of HFV used is high-frequency oscillatory ventilation (HFOV)

What are the frequency ranges for oscillating air movements in HFOV?

600–900 breaths per minute (10–15 Hz)

What are the two major concepts that differentiate HFOV from conventional ventilation?

* CO2 is cleared despite using a VT that is less than physiological dead-space * CO2 removal is increased by decreasing the frequency

What is the major use for HFOV?

Lung recruitment

What is Neurally Adjusted Ventilator Assistance (NAVA)?

Senses the electric activity of the diaphragm (EAdi) and uses a catheter embedded in a gastric tube

What triggers a mechanical breath in NAVA?

When electrical activity is greater than a set threshold (0.5 μV)

How does positive ventilator pressure affect hemodynamics?

* Increases alveolar pressure and lung volume * Compresses the heart and great veins in the thorax * Decreases venous return and preload

What can result from lower preload in patients undergoing mechanical ventilation?

Lower stroke volume leading to lower cardiac output and hypotension

What management strategy may mitigate the effects of reduced preload?

Optimization of intravascular volume

What is the most common indication for mechanical ventilation in children with normal lungs?

General anesthesia

What are the complications associated with mechanical ventilation?

* Atelectasis of dependent lung * Ventilator-associated pneumonia

What is Acute Respiratory Distress Syndrome (ARDS)?

An acute pathological condition characterized by inflamed, atelectatic lungs resulting from underlying conditions like sepsis

What is the mainstay approach in managing ARDS during mechanical ventilation?

Avoidance of high VT and keeping the lung open by recruitment maneuvers

What is the primary goal of mechanical ventilation in status asthmaticus?

Reduction in work of breathing (WOB)

What is the management for bronchiolitis in mechanically ventilated patients?

Balancing PEEP to reduce hyperinflation and open areas of atelectasis

What are the indications for mechanical ventilation in neonates?

* Resuscitation at birth * Respiratory distress syndrome (RDS) * Persistent pulmonary hypertension (PPHN)

What is the goal of mechanical ventilation in neonates?

Provide O2, recruit lung if recruitable, assist in clearing CO2, alleviate pulmonary hypertension

What management strategy is used for patients with elevated pulmonary blood flow in congenital heart disease?

* Lower FiO2 * Adequate PEEP

What is the key monitoring focus for the ventilated child?

* Comfortable ventilation * Oxygenation * Work of breathing (WOB)

What can cause deterioration in WOB during mechanical ventilation?

* Poor mask fit * Obstructed or dislodged ET * Ventilator equipment failure

How is gas humidification achieved in mechanical ventilation?

By using a chamber containing water at 2–3°C above body temperature

What is the preferred fluid management strategy for mechanically ventilated patients?

Fluid restriction

What is weaning in the context of mechanical ventilation?

The process of transferring all work of breathing from the ventilator to the patient

What are the major concerns in preparing for extubation?

* Adequacy of respiratory drive * Muscle strength for coughing * Ventilation airway integrity * Oxygenation * Adequacy of analgesia

What is Ventilator-Associated Lung Injury (VALI)?

Direct injury to the lungs from positive pressure ventilation, primarily resulting from high VTs

What complication can occur due to excessive recruitment maneuvers during mechanical ventilation?

Pressure-induced damage (barotrauma)

What is subglottic stenosis and what increases its incidence?

Occurs in 1%–2% of intubated children; incidence increases with length of intubation, traumatic intubation, and preexisting airway inflammation