CHAPTER 15 | Respiratory Functions in Anesthesia

Question 1

The pressure measured after inflation
with a certain volume is termed

Answer 1

Plateau pressure

Question 2

This represents the change in volume of the lung above FRC and is a surrogate for global lung strain, a marker of ventilator-induced injury and a predictor of mortality in acute respiratory distress syndrome (ARDS).

Answer 2

Driving pressure

Question 3

True or False

Lower driving pressures during anesthesia appear to correlate with lower odds of postoperative pulmonary complications.

Answer 3

TRUE

It is critical to note that any adjustment of tidal volume needs to be done with
an understanding of FRC. When driving pressure and strain are already low, further reduction in tidal volumes to meet arbitrary weight-based guidelines may be unnecessary and can result in both atelectasis and ventilator dyssynchrony in nonparalyzed individuals.

Question 4

True or False

Lowering Vt (to 6 cc/kg or less) may increase mortality when respiratory system compliance is high, as seen in patients with acute respiratory distress syndrome

Answer 4

TRUE

Question 5

True or False

A key goal of mechanical ventilation is to both REDUCE work of breathing and MINIMIZE the mechanical power applied to the lung

Answer 5

TRUE

Question 6

This is the change in volume per unit change in the pressure difference across the elastic body

Answer 6

COMPLIANCE

Question 7

This is the difference between pressure in the alveolus (Palv) and pressure in the pleural space:

Answer 7

Transmural or Transpulmonary Pressure

Question 8

TRUE or FALSE

Compliance is lower in certain clinical
scenarios that increase the weight in the abdomen and the force applied
across the diaphragm and chest wall (e.g., Trendelenburg position, obesity, or when inappropriate low tidal ventilation is applied)

Answer 8

TRUE

Question 9

Effect of OBESITY on lung compliance:

Answer 9

Obesity shifts the pressure–volume curve of the chest wall to RIGHT without a change of shape. Lung compliance is therefore more negatively affected.

Question 10

Effect of Pneumoperitoneum on lung compliance:

Answer 10

In pneumoperitoneum, the thoracic cavity changes shape, resulting in reduced chest wall compliance with relative preservation
of lung compliance. A higher proportion of applied airway pressure then goes into moving the chest wall rather than lungs.

Question 11

This occurs when the rate of gas flow out of alveoli into blood exceeds the rate of gas flow into alveoli (as distal airways close):

Answer 11

RESORPTION

Resorption atelectasis may occur even in the absence of distal airway occlusion with
(1) alveoli that have low ventilation/perfusion (V/Q) ratios and
(2) when the rate of gas leaving the alveoli is increased such as when high concentrations of inspired oxygen are used or mixed venous oxygen content is low.

Question 12

The cricoid membrane tethers the trachea to the cricoid cartilage at the level of the cervical vertebrae?

Answer 12

C6
sixth cervical vertebral body

Question 13

Following tracheal intubation, the distal end of the endotracheal tube moves an average of ___ with flexion (toward the carina):

Answer 13

3.8 cm with flexion (toward the carina) and extension (away from the carina) of the neck

Question 14

True about the Anatomy of the lower airway EXCEPT:

A. The trachea is a fibromuscular tube 10 to 12 cm long in infants with an outer diameter of approximately 10 mm

B. The trachea enters the superior mediastinum and bifurcates at the sternal angle

C. The adult carina can move superiorly as much as 5 cm from its normal resting position

D. In the adult, the right bronchus leaves the trachea at approximately 25 degrees
from the vertical tracheal axis, whereas the angle of the left bronchus is about 45 degrees.

Answer 14

**A. A. The trachea is a fibromuscular tube 10 to 12 cm long in infants with an outer diameter of approximately 10 mm

Option A is false because the infants trachea is incorrect in this statement.

• The trachea is a fibromuscular tube 10 to 12 cm long in adults with an outer diameter of approximately 20 mm. Structural support is provided by U-shaped structures composed of hyaline cartilage, with the opening of the U facing posteriorly

Question 15

The adult carina can move superiorly as much as how much?

Answer 15

5 cm

Question 16

Changes in the aging lung result in decreased lung recoil (elastance) creating?

Answer 16

INCREASED residual volume and FRC

Question 17

What happens to compliance and FRC in OBSTRUCTIVE LUNG DISEASE

Answer 17

ELEVATED or INCREASED

The black vertical line at zero defines functional residual capacity (FRC), regardless of the position of the curve on the graph. Mild restrictive lung disease, indicated by the green line, shifts the curve to the right with little change in slope.

However, with restrictive disease, the patient breathes on a lower FRC, at a point on the curve where the slope is less. Severe restrictive pulmonary disease
profoundly depresses the FRC and diminishes the slope of the entire curve (red line).

Obstructive disease (orange line) elevates both FRC and compliance.

Question 18

What happens to compliance and FRC in RESTRICTIVE LUNG DISEASE

Answer 18

Mild restrictive lung disease, indicated by the green line, shifts the curve to the right with little change in slope.

However, with restrictive disease, the patient breathes on a lower FRC, at a point on the curve where the slope is less. Severe restrictive pulmonary disease
profoundly depresses the FRC and diminishes the slope of the entire curve (red line).

Question 19

refers to the cessation of ventilatory effort with lungs filled at TLC

Answer 19

Apneusis

Question 20

This is the inflow and outflow of gas transport in the alveolar space

Answer 20

Ventilation

Question 21

This is the inflow and outflow of gas transport in the capillary

Answer 21

Perfusion

Question 22

TRUE or FALSE

The normal V/Q ratio is 0.8 where normal ventilation in the alveoli is 4 L/min and normal cardiac output is 5 L/min

Answer 22

TRUE

Question 23

This refers to the alveoli that receive more perfusion than ventilation and have V/Q ratios that approach zero.

Answer 23

SHUNT

In shunt, venous blood either does not

Question 24

TRUE of Gas exchange except:

A. The dependent lung receives greater proportions of ventilation and perfusion than nondependent areas of the lung

B. Alveoli that receive more ventilation than perfusion and have V/Q ratios that approach infinity are termed dead space

C. The pleural pressure is higher (and transpulmonary pressure lower) in dependent areas of the lung, hence, Inspiration therefore starts at more favorable compliance for inflation

D. During anesthesia, hypoxemia primarily occurs due to shunt from atelectasis

E. HPV is potentiated by inhalational anesthetics and high concentrations of inspired oxygen

Answer 24

E. HPV is potentiated by inhalational anesthetics and high concentrations of inspired oxygen

This is a false statement. HPV is INHIBITED by Inhalational agents and high concentration of inspired O2

• All the other statements are correct.