Question 1

On which of the following conditions is oxygen therapy effective?
I.Anatomical shunting
II.V/Q mismatch
III.Diffusion defects
IV.Hypoventilation

Accepted Answer

Oxygen therapy is effective in VA/VC mismatch, but not if a large amount of absolute shunting is present. Oxygen therapy is also effective in diffusion defects and hypoventilation.

Question 2

How should patients with unilateral lung disease be positioned to optimize oxygenation?

Accepted Answer

Patients with unilateral lung disease (e.g., one lung with pneumonia) should be positioned in bed with the healthy lung down. Gravity causes blood to flow preferentially to the healthy lung, improving the VA/VC and the PaO₂.

Question 3

In which of the following types of patients is plateau pressure not a reliable surrogate for assessing alveolar overdistension ?

Accepted Answer

Plateau pressure measurement is a reliable surrogate for assessing overdistension of the lung in all patients except those with restricted chest wall and diaphragmatic movement.

Question 4

When should CPAP or PEEP be considered?

Accepted Answer

In general, if a PaO₂ of at least 60 mm Hg with an FIO₂ of 0.5 or less cannot be achieved, PEEP or CPAP should be considered.

Question 5

What is the best correlate of alveolar pressure in mechanically ventilated patients?

Accepted Answer

In mechanically ventilated patients, the correlate of alveolar pressure is plateau pressure, measured at the endotracheal tube at end-inspiration under zero airflow conditions (see Chapter 3).

Question 6

What is the most common target level of hemoglobin saturation when oxygen is administered?

Accepted Answer

The goal of oxygen therapy is to achieve a hemoglobin saturation of at least 90% PaO₂ of at least 60 mm Hg) at an FIO₂ of 0.50 or less.

Question 7

What is the most commonly recommended position for a patient in the immediate post-surgical period to improve the PaO₂?

Accepted Answer

The sitting or standing position usually improves the PaO₂ over the supine position in obese patients and those with obstructive lung disease. An upright position allows gravity to pull down on the diaphragm, expanding the lungs and increasing the functional residual capacity (FRC). For this reason it is common practice to get patients out of bed, even on the same day of a major surgery, so that they can stand or walk; this improves overall ventilation and oxygenation because it improves lung mechanics.

Question 8

Which of the following substances are examples of inflammatory mediators?
I.Cytokines
II.Endotoxins
III.Prostaglandins
IV.Oxygen radicals

Accepted Answer

Examples of inflammatory mediators are prostaglandins, endotoxins, and cytokines.

Question 9

Which of the following are characteristics of ALI? I.PaO₂/FIO₂ < 200 mm Hg II.Alveolar-capillary membrane injury III.Widespread atelectasis IV.Low compliance

Accepted Answer

Acute lung injury (ALI) is characterized by alveolar inflammation, alveolar-capillary membrane injury, high-permeability pulmonary edema, widespread atelectasis, and low lung compliance; the end result is severe shunting and refractory hypoxemia. Acute respiratory distress syndrome (ARDS) is the most severe form of ALI. According to the American-European Consensus Conference on ARDS, the PaO₂/FIO₂ in ALI, regardless of applied positive end-expiratory pressure, is 300 mm Hg or less, whereas it is 200 mm Hg or less in ARDS.

Question 10

What is the generally accepted plateau pressure below which lung injury is minimized?

Accepted Answer

It is generally accepted that the incidence of stretch-related lung injury is minimized if inspiratory plateau pressure is 30 cm H₂O or less.

Question 11

Which of the following statements are true of ROP? I.A higher than normal PaO₂ may cause ROP. II.The PaO₂ is the critical factor in ROP, not the FIO₂ per se. III.ROP may cause permanent blindness. IV.The FIO₂ is the critical factor in ROP, not the PaO₂ per se.

Accepted Answer

High arterial PO₂, especially in the premature infant, is dangerous. A higher than normal PaO₂ may cause retinopathy of prematurity (ROP), in which the retinal arteries of the infant's eyes constrict, possibly causing permanent blindness. The PaO₂ is the critical factor in ROP, not the FIO₂ per se. In other words, PaO₂ may be at dangerous levels at FIO₂ well below 0.50; likewise, PaO₂ may be in a safe range at FIO₂ greater than 0.50.

Question 12

What is the minimum level of FIO₂ that, when used for a prolonged period of time, has been associated with damage to alveolar cells?

Accepted Answer

FIO₂ above 0.50 over a prolonged period of time may produce toxic damage to alveolar cells, known as pulmonary oxygen toxicity.

Question 13

What type of oxygen device should be recommended for a patient with hypercapnic COPD?

Accepted Answer

Oxygen should be administered to patients with hypercapnic chronic obstructive pulmonary disease (COPD) via devices that can produce relatively low, fixed inspired oxygen concentrations not influenced by the patient's ventilatory pattern.

Question 14

Which of the following levels of FIO₂ has been considered safe for preventing significant lung impairment?

Accepted Answer

Individual susceptibility to oxygen toxicity varies considerably; in general, an FIO₂ of 0.50 or less for 2 to 7 days does not produce significant lung impairment.

Question 15

Which of the following is an absolute contraindication for CPAP?

Accepted Answer

CPAP does not mechanically ventilate the lungs; therefore, it is contraindicated in patients who cannot sustain adequate spontaneous ventilation.

Question 16

Which of the following are considered mechanisms of ventilator-induced lung injury?
I.Barotrauma
II.Volutrauma
III.Biotrauma
IV.Atelectrauma

Accepted Answer

Mechanisms of ventilator-induced lung injury fall into three general categories: mechanical stretch injury from hyperinflation (barotrauma/volutrauma); the repetitive collapse and reinflation of alveoli (atelectrauma); and the toxic effects of inflammatory mediators on pulmonary tissues (biotrauma).

Question 17

Which of the following are considered poor candidates for PEEP and CPAP?
I.Unilateral or localized lung disease
II.Normally compliant lungs
III.Highly compliant lungs
IV.Bilateral lung disease

Accepted Answer

Poor candidates for PEEP and CPAP are people with unilateral or localized lung disease (involving only one lung or one lobe) and those with normally or highly compliant lungs.

Question 18

What is the level of PaO₂ set as a goal for oxygen therapy in the healthy adult?

Accepted Answer

In general, oxygen therapy is used to maintain a PaO₂ of at least 60 mm Hg (SaO₂ of at least 90%).

Question 19

What is the major difference between CPAP and PEEP?

Accepted Answer

The major difference between continuous positive airway pressure (CPAP) and positive end-expiratory pressure (PEEP) is that airway pressure does not rise during inspiration with CPAP as it does with PEEP.

Question 20

Which of the following parameters should be periodically evaluated in patients with COPD who are receiving oxygen therapy?

Accepted Answer

A periodic arterial PCO₂ analysis is important in monitoring oxygen-induced hypercapnia.

Quiz 14: Physiological Basis for Oxygenation and Lung Protection Strategies

On which of the following conditions is oxygen therapy effective? I.Anatomical shunting II.V/Q mismatch III.Diffusion defects IV.Hypoventilation

How should patients with unilateral lung disease be positioned to optimize oxygenation?

In which of the following types of patients is plateau pressure not a reliable surrogate for assessing alveolar overdistension ?

When should CPAP or PEEP be considered?

What is the best correlate of alveolar pressure in mechanically ventilated patients?

What is the most common target level of hemoglobin saturation when oxygen is administered?

What is the most commonly recommended position for a patient in the immediate post-surgical period to improve the PaO2?

Which of the following substances are examples of inflammatory mediators? I.Cytokines II.Endotoxins III.Prostaglandins IV.Oxygen radicals

Which of the following are characteristics of ALI? I.PaO2/FIO2 < 200 mm Hg II.Alveolar-capillary membrane injury III.Widespread atelectasis IV.Low compliance

What is the generally accepted plateau pressure below which lung injury is minimized?

Which of the following statements are true of ROP? I.A higher than normal PaO2 may cause ROP. II.The PaO2 is the critical factor in ROP, not the FIO2 per se. III.ROP may cause permanent blindness. IV.The FIO2 is the critical factor in ROP, not the PaO2 per se.

What is the minimum level of FIO2 that, when used for a prolonged period of time, has been associated with damage to alveolar cells?