RT15A Initiating and Adjusting Invasive Ventilatory
Support Egan's questions with complete solutions
Mechanical ventilation uses sophisticated life-support technology to correct answer: maintain adequate tissue oxygenation and remove carbon dioxide (CO2).
At its most basic level, mechanical ventilation correct answer: supports or replaces the normal ventilatory pump, moving air into and out of the lungs
The primary function of a mechanical ventilator is correct answer: to ventilate
The main indication for mechanical ventilation is correct answer: inadequate or absent spontaneous breathing.
The goals of mechanical ventilatory support are correct answer: to maintain adequate alveolar ventilation and oxygen (O2) delivery, restore acid-base balance, and reduce the work of breathing (WOB) with minimum harmful side effects and complications.
secondary to hypoxemia and an increased WOB, Mechanical ventilation may also correct answer: reduce increased myocardial work
Other physiologic objectives of mechanical ventilatory support include correct answer: increasing or maintaining lung volume with positive end-expiratory pressure (PEEP) for promotion, improvement, or maintenance of lung recruitment. 1
Lung protective ventilatory strategies entail an approach to mechanical ventilation that includes correct answer: the use of small tidal volume (VT), low plateau pressures and driving pressures, appropriate fractional inspired oxygen (FiO2), and appropriate levels of PEEP. (ARDS/COVID)
lung protective strategies are helpful for correct answer: ARDS but should be applied to all patients requiring ventilatory support for acute respiratory failure
Ventilator-induced lung injury is primarily caused by correct answer: an elevated transpulmonary pressure during positive pressure ventilation
transpulmonary pressure correct answer: is the difference between alveolar pressure and pleural pressure.
A safe transpulmonary pressure during mechanical ventilation is not firmly established, but most clinicians would agree that correct answer: the lower the transpulmonary pressure, the less likely
the development of ventilator-induced lung injury.
At the bedside we measure plateau pressure and driving pressure (plateau pressure − PEEP) variables to assess correct answer: the safety of our ventilator settings. the maximum plateau pressure without increasing the risk of significant lung injury correct answer: 27 cm H2O
most recommend that plateau pressure should be maintained correct answer: ≤28 cm H2O
a driving pressure greater than 15 cm H2O, correct answer: increasing the risk of mortality during ventilatory support
High transpulmonary pressures are associated with correct answer: alveolar overdistention and lung injury. 3
Components of a Lung Protective Approach to Ventilatory Support correct answer: • VT 4-8 mL/kg PBW greater Pplat lower VT
• Plateau Pressure <28 cm H2O
• Driving pressure <15 cm H2O
• PEEP appropriate for the patient presentation
• Avoid asynchrony
• Avoid autoPEEP and air trapping
• Appropriate FiO2 maintain PaO2 55-80 and SpO2 88%-95%
Plateau pressure (Pplat) correct answer: the end inspiratory equilibration pressure, measures the mean peak alveolar pressure and is the best bedside clinical reflection of transpulmonary pressure; pressure in the patient's airway during mechanical ventilation resulting from the application of an end-inspiratory hold. This is equal to the average peak alveolar pressure.
Although Pplat is not an accurate measurement of transpulmonary pressure, correct answer: the transpulmonary pressure during controlled ventilation never exceeds the Pplat.
a Pplat greater than 28 cm H2O may need to be applied in patients with correct answer: a morbid obesity requiring high PEEP (>20 cm H2O) levels and in patients with decreased thoracic compliance without resulting in overdistention; 6 this is because a decrease in chest-wall
compliance (massive fluid resuscitation, abdominal distention, elevated bladder pressure) increases the pleural pressure, decreasing the transpulmonary pressure.
The higher the Pplat, correct answer: the smaller the VT should be
Generally, a VT greater than 10 mL/kg IBW correct answer: is never indicated in critically ill patients.
Lung injury can also be caused by correct answer: repetitive opening and closing of unstable lung units.
The application of an appropriate level of PEEP ensures correct answer: unstable lung units are maintained in the open position, reducing the likelihood of additional lung injury.
driving pressures greater than 15 cm H2O correct answer: increase mortality. Hazards of mechanical ventilation correct answer: include decreased venous return and cardiac output, patient-ventilator asynchrony, and ventilatory muscle dysfunction owing to inappropriate ventilator settings, ventilator-associated pneumonia, and ventilator-induced lung injury
Typical progression of acute respiratory failure. Initially, there is a decline in arterial O2 tension and saturation. correct answer: When PaO2 decreases to approximately 60 mm Hg (A), the patient begins to breathe more, PaCO2 decreases, and pH increases. Early in the progression, arterial blood gas results show acute alveolar hyperventilation (uncompensated respiratory alkalosis) secondary to hypoxemia. As the patient's condition worsens, increases in ventilatory workload typically lead to the adoption of a rapid, shallow breathing pattern; although minute ventilation may remain high, effective ventilation decreases, PaCO2 begins to increase, and pH begins to decrease (B). At point C, arterial blood gas results may show normal PaCO2 and pH with moderate to severe hypoxemia. If mechanical ventilation is not initiated, the patient's condition may progress to acute ventilatory failure, severe hypoxemia, and corresponding severe respiratory acidosis (D).
Most Common Causes of Acute Respiratory Failure Requiring Mechanical Ventilation in the United States and Canada correct answer: Postoperative respiratory failure, sepsis, heart failure, pneumonia, trauma, ARDS, aspiration
Physiologic Goals of Ventilatory Support correct answer: • Support or manipulate gas exchange.
• Maintain alveolar ventilation (PaCO2 and pH).
• Maintain arterial oxygenation (PaO2, SaO2, SpO2, CaO2, and DO2).
• Increase end-expiratory lung volume, functional residual capacity (FRC).
• Reduce or manipulate work of breathing.
• Minimize cardiovascular impairment.
• Ensure patient-ventilatory synchrony.
• Avoid ventilator-induced lung injury.
Specific Clinical Objectives of Ventilatory Support correct answer: • To reverse hypoxemia.
• To reverse acute respiratory acidosis.
• To prevent or reverse atelectasis.
• To reverse ventilatory muscle dysfunction.
• To decrease systemic or myocardial O2 consumption.
• To maintain or improve cardiac output.
• To reduce intracranial pressure.
• To stabilize the chest.
A lung protective ventilatory strategy correct answer: is an approach to mechanical ventilation that includes the use of small tidal volume (VT), low plateau pressures and driving pressures, appropriate FiO2 and appropriate levels of PEEP.
The goals of mechanical ventilation are achieved by correct answer: choosing an appropriate mode of ventilation, PEEP level, FiO2, VT or pressure level, rate, peak flow and flow waveform,
and inspiratory time, Appropriate trigger sensitivity, pressure limit, alarms, backup ventilation, and humidification must be selected. After initial ventilator setup, adjustments must be made based on the patient's response and the patient-specific clinical objectives of ventilatory support. choose the mode of ventilation, and initial ventilator settings (e.g., rate, VT or pressure level, FiO2, PEEP), choose appropriate alarm and apnea settings
examples of modes of ventilation correct answer: (e.g., volume assist/control [VA/C], pressure assist/control [PA/C], pressure support ventilation [PSV], pressure-regulated volume control [PRVC] , volume support , adaptive support ventilation, proportional assist ventilation [PAV] , or neurally adjusted ventilatory assist [NAVA] )
Initial Ventilator Setup: key decisions correct answer: • Noninvasive versus invasive ventilation.
• Type and method of establishment of an airway.
• Partial versus full ventilatory support.
• Choice of ventilator.
• Mode of ventilation.
• Assist/control ventilation (volume vs. pressure) vs. pressure support.
• Other newer modes and adjuncts to ventilation.
Initial Ventilator Setup: key ventilatory values correct answer: • Trigger method (pressure or flow trigger) and sensitivity.
• VT (volume ventilation) or pressure level (pressure support and PA/C).
• Rate
• Inspiratory flow, inspiratory time, expiratory time, or I:E ratio.
• Inspiratory flow waveform.
• FiO2
• PEEP
initial ventilator set up: choose appropriate alarm and backup values correct answer: • Low-
pressure, low PEEP alarms.
• High-pressure limit and alarm.
• Volume alarms (low VT/high VT, high and low minute ventilation).
• High rate and low rate alarms.
• Apnea alarm and apnea ventilation values.
• High/low O2 alarm.
• High/low temperature alarm.
• I:E ratio limit and alarm.
Initial setup of ventilation parameters should include correct answer: a limitation of tidal volume
(4-8 mL/kg predicted body weight [PBW]), plateau (<28 cm H2O), and driving (<15 cm H2O) pressure in ALL patients acutely requiring mechanical ventilation.
Volume-targeted ventilation mode essentially includes correct answer: VA/C and synchronized intermittent mandatory ventilation (SIMV).
Pressure ventilation mode includes correct answer: PA/C, SIMV, PRVC, volume support, and airway pressure release ventilation (APRV)
