How Do Ventilators Affect V/Q
_____________-_____________ ______________ in ventilated patients occurs when there is an imbalance between the amount of air reaching the alveoli and the blood flow through the lung capillaries.
What is Ventilation-perfusion (V/Q) mismatch
This ventilation mode allows patients to breathe spontaneously between machine-delivered breaths, supporting a gradual transition from full support to spontaneous breathing.
What is synchronised intermittent mandatory ventilation (SIMV)?
This is a routine context for using mechanical ventilation in major cardiac or upper abdominal surgery, often referred to by the ICU mnemonic "warm, wean, and wake."
What is post-operative care following routine anaesthesia for major surgery?
This type of pressure drives air into the lungs during normal, spontaneous breathing.
What is negative pressure?
Category: V/Q Matching in Trauma
Because Jacob has right lung contusions and collapse, this basic ventilator setting is often increased to help oxygen reach the blood despite poor ventilation in injured regions.
What is FiO₂ (fraction of inspired oxygen)?
Ventilator settings must be regularly adjusted to match these two key patient-specific parameters for optimal outcome.
What are gas exchange results and lung mechanics?
This ventilator mode is often initially chosen for patients who are heavily sedated and unable to breathe spontaneously following major trauma.
What is controlled mandatory ventilation (CMV)?
Profound inability to maintain alertness or rationality due to toxic, metabolic, or hypoxic causes often leads to ventilatory support for airway protection. What is the clinical term for this altered mental state?
What is confusion (with need for airway protection)?
In contrast to normal breathing, mechanical ventilators use this type of pressure to deliver breaths.
What is positive pressure?
Category: Modes and Types
For an intubated trauma patient like Jacob who is sedated in the ICU, this basic ventilator mode is usually started, delivering all breaths for the patient.
What is controlled mandatory ventilation (CMV)?
When lung regions are perfused but not ventilated due to alveolar collapse or edema, this specific form of V/Q mismatch occurs, resulting in impaired oxygen exchange despite blood flow.
What is a shunt?
These two main variables are typically controlled by ventilator modes when delivering breaths, each associated with different benefits and risks.
What are pressure and volume?
A persistently elevated respiratory rate above this value in adults, especially with increased work of breathing or exhaustion, is a common threshold prompting consideration for mechanical ventilation.
What is a respiratory rate over 30 breaths per minute?
During positive pressure ventilation, this can increase within the thorax, potentially reducing venous return and cardiac output effects, that are much less common during normal breathing.
What is intrathoracic pressure?
Category: Normal vs. Ventilator Breathing
Compared to normal negative-pressure breathing, ventilator breaths given to Jacob after trauma generate this type of force, which increases mean intrathoracic pressure and can affect blood return to the heart.
What is positive pressure?
This change in the pattern of airflow during positive pressure ventilation explains why ventilated air preferentially enters the most compliant regions of the lung, often resulting in a V/Q mismatch compared to normal spontaneous breathing.
What is the path of least resistance for air during positive pressure ventilation, leading to upper lobe ventilation and altered V/Q matching?
This ventilator mode delivers each breath to a preset pressure, which minimises the risk of barotrauma compared to the alternative, but may result in hypoventilation if lung compliance decreases during mechanical ventilation.
What is pressure control ventilation?
When this arterial blood gas value falls below 7.2 in the presence of elevated carbon dioxide, it becomes a classic indication for starting mechanical ventilation in the ICU.
What is a pH less than 7.2 with a raised CO₂?
_________ _________ & __________ can vary based on activity level, with their usual resting rates around 12 breaths/min and a typical TV of 500 mL.
What is breathing rate & volume?
Or respiration rate
Category: Indications
Jacob meets this classic criterion for invasive mechanical ventilation because of hypoxemia, chest trauma, and ongoing surgeries after his accident
What is respiratory failure with risk of airway compromise or inability to maintain adequate ventilation?
This physiological complication can arise when positive pressure ventilation preferentially delivers air to already well-ventilated, compliant regions of the lung.
What is the development of increased physiological dead space due to ventilation-perfusion mismatch during mechanical ventilation?
or
increasing dead space ventilation and exacerbating V/Q mismatch in patients with regional lung pathology.
This ventilator mode delivers a fixed tidal volume with every breath, ensuring consistent minute ventilation but increasing the risk of high airway pressures, and potential barotrauma- if the patient's lung compliance declines.
What is volume control ventilation?
Patients may require mechanical ventilation even without primary respiratory failure if these types of shock causes exhaustion and multi-organ compromise.(3)
What is cardiac, septic, or hypovolemic shock leading to exhaustion or organ dysfunction requiring mechanical ventilation?
Mechanical ventilation may impair this process by bypassing the normal routes of airway humidification and filtration, potentially increasing the risk of infection or airway injury.
What is the natural upper airway defense system?
Category: Advanced V/Q and Patient Matching
In Jacob’s case, if positive pressure ventilation preferentially ventilates his healthier lung regions while contused, collapsed areas remain underinflated but still receive blood flow, this dangerous physiologic mismatch can occur and cause persistent hypoxemia.
What is ventilation-perfusion (V/Q) mismatch due to shunt physiology?