Mechanical
ventilation:
Ventilation:Physiologic
al And Clinical
th
Applications 8 Edition
By J.M. Cairo, PhD,
RRT, FAARC
, Pilbeam's Mechanical Ventilation: Physiological and Clinical
Applications, 8th Edition
J.M. Cairo, PhD, RRT, FAARC
Elsevier, 2024
Chapter 1: Basic Terms and Concepts of Mechanical
Ventilation
PART A: MULTIPLE CHOICE QUESTIONS (35 Questions)
1. A patient has a tidal volume (VT) of 500 mL, a respiratory rate (f) of 14 breaths/min,
and an anatomic dead space (VD) of 150 mL. What is this patient's alveolar minute
ventilation?
A) 7.0 L/min
B) 4.9 L/min
C) 2.1 L/min
D) 5.6 L/min
Answer: B
Rationale: Alveolar minute ventilation (VA) is calculated by subtracting the dead space
volume from the tidal volume and multiplying by the respiratory rate. VA = (VT - VD) x f
= (500 mL - 150 mL) x 14 = 350 mL x 14 = 4,900 mL, or 4.9 L/min. This measurement
represents the volume of fresh gas reaching the alveoli each minute for gas exchange.
The minute ventilation (VE) would be 7.0 L/min, which includes both alveolar ventilation
and dead space ventilation .
, Difficulty: Hard
Learning Objective: 1.1
2. Which of the following terms refers to the volume of gas that remains in the lungs
after a normal exhalation?
A) Residual volume (RV)
B) Functional residual capacity (FRC)
C) Expiratory reserve volume (ERV)
D) Tidal volume (VT)
Answer: B
Rationale: Functional residual capacity (FRC) is the volume of gas remaining in the
lungs at the end of a normal, passive exhalation. It is the sum of the expiratory reserve
volume (ERV) and the residual volume (RV). FRC is a crucial physiological parameter as it
represents the lung volume from which normal breathing occurs and helps to prevent
atelectasis by maintaining alveolar patency. The residual volume is the gas remaining
after a maximal exhalation .
Difficulty: Easy
Learning Objective: 1.1
3. A patient receiving mechanical ventilation has a peak inspiratory pressure (PIP) of 30
cm H₂O and a plateau pressure (Pplat) of 18 cm H₂O. What is this patient's airway
resistance?
A) 12 cm H₂O
B) 5 cm H₂O
C) 1.67 cm H₂O/L/sec
D) This cannot be determined from the given information
Answer: D
Rationale: Airway resistance cannot be calculated from just pressure readings. To
compute resistance, you need both the driving pressure (the difference between peak
pressure and plateau pressure) and the flow rate. Resistance = (PIP - Pplat) / Flow.
, Without knowing the flow rate, a resistance value in cm H₂O/L/sec cannot be
determined. However, the pressure difference (PIP - Pplat) represents the resistive
pressure component. A PIP of 30 cm H₂O and Pplat of 18 cm H₂O indicates a resistive
pressure component of 12 cm H₂O .
Difficulty: Hard
Learning Objective: 1.2
4. A patient is receiving mechanical ventilation with a tidal volume of 450 mL. What is
this patient's dead space-to-tidal volume ratio (VD/VT) if the measured dead space is
150 mL?
A) 0.33
B) 0.25
C) 0.67
D) 3.0
Answer: A
Rationale: The dead space-to-tidal volume ratio (VD/VT) is calculated by dividing the
dead space volume by the tidal volume. VD/VT = 150 mL / 450 mL = 0.33. This ratio is
clinically important as it represents the fraction of each tidal breath that does not
participate in gas exchange. A VD/VT ratio of 0.33 means that 33% of each breath is
wasted in dead space. Normal VD/VT is typically around 0.2-0.3. Elevated ratios indicate
inefficient ventilation .
Difficulty: Medium
Learning Objective: 1.1
5. A patient's lungs are described as having increased compliance. This indicates that
the lungs are:
A) Stiffer than normal and require more pressure to inflate
B) More distensible than normal and require less pressure to inflate
C) Normal
D) Hyperinflated