Ch 323: Mechanical Ventilatory Support

Question 1

What is the definition of hypoxemic respiratory failure?

Answer 1

Hypoxemic respiratory failure is present when arterial O₂ saturation (SaO₂) is < 90%, occurs despite an increased inspired O₂ fraction, and usually results from ventilation-perfusion mismatch or shunt.

(p. 1740)

Question 2

What is the definition of hypercarbic respiratory failure?

Answer 2

Hypercarbic respiratory failure is present when arterial carbon dioxide (PCO₂) is elevated, usually >50 mmHg, and results from conditions that decrease minute ventilation or increase physiologic dead space such that alveolar ventilation is inadequate to meet metabolic demands.

Question 3

Morphine can promote _________ release from tissue mast cells and may worsen bronchospasm in patients with asthma.

Answer 3

histamine

(p. 1741)

Question 4

Depolarizing agents such as succinylcholine should not be used in patients with…

Answer 4

…renal failure, tumor lysis syndrome, crush injuries, muscular dystrophy syndromes, and any condition associated with elevated K⁺ levels.

(p. 1741)

Question 5

What is the most widely used mode of ventilation?

Answer 5

assist-control ventilation (ACMV)

(p. 1741)

Question 6

What is the ventilatory rate determined by in ACMV mode?

Answer 6

the programmed backup rate or the patient’s intrinsic respiratory rate, whichever is higher

(p. 1741)

Question 7

Respiratory alkalemia can lead to…

Answer 7

…myoclonus or seizures.

(p. 1741)

Question 8

The concept of dynamic hyperinflation leading to increased intrathoracic pressures is called…

Answer 8

…auto PEEP.

(p. 1741)

Question 9

Auto PEEP may occur if the patient’s respiratory mechanics are such that…

Answer 9

…there is inadequate time for complete exhalation between inspiratory cycles.

(p. 1741)

Question 10

SIMV differs from ACMV in that only a…

Answer 10

…present number of breaths are ventilator-assisted.

(p. 1741)

Question 11

Explain how SIMV works.

Answer 11

Mandatory breaths are delivered in synchrony with the patient’s inspiratory efforts at a frequency determined by the operator. If the patient fails to initiate a breath, the ventilator delivers a fixed-tidal-volume breath and resets the internal timer for the next inspiratory cycle.

(p. 1741)

Question 12

What are the 4 core principles of protective ventilatory strategy?

Answer 12

(1) Set a target tidal volume close to 6 mL/kg of ideal body weight.
(2) Prevent plateau pressure (static pressure in the airway at the end of inspiration) exceeding 30 cm H2O.
(3) Use the lowest possible fraction of inspired oxygen (Fio2) to keep the Sao2 at ≥90%.
(4) Adjust the PEEP to maintain alveolar patency while preventing overdistention and closure/reopening.