Ch.1

Question 1

Define ventilation?

Answer 1

the movement of air in and out of the lungs.

Question 2

Define external respiration?

Answer 2

involves the diffusion of oxygen and carbon dioxide between the alveoli and the pulmonary capillaries.

Question 3

Define internal respiration?

Answer 3

occurs at the cellular level and involves the exchange of oxygen and carbon dioxide between the systemic capillaries and the cells of the body.

Question 4

Define transairway pressure?

Answer 4

(PTA) is the pressure difference between the airway opening and the alveolus: PTA = Pawo − Palv.

Question 5

Define transthoracic pressure?

Answer 5

(PW or PTT) is the pressure difference between the alveolar space or lung and the body’s surface (Pbs): PW (or PTT) = Palv − Pbs.

Question 6

Define transpulmonary pressure?

Answer 6

A.k.a transalveolar pressure (PL or PTP) is the pressure difference between the alveolar space and the pleural space
(Ppl): PL (or PTP) = Palv − Ppl.

Question 7

Define transrespiratory pressure?

Answer 7

is the pressure difference between the
airway opening and the body surface: PTR = Pawo − Pbs.

Question 8

Define compliance?

Answer 8

as the relative ease with which the structure distends. The inverse of elastance.

Question 9

Define elastance?

Answer 9

the tendency of a structure to return to its original form after being stretched or acted on by an outside force.

Question 10

Define resistance?

Answer 10

a measurement of the frictional forces that must be overcome during breathing.

Question 11

What is the value for intaalveolar pressure throughout inspiration and expiration during quiet normal breathing?

Answer 11

0 to -5 mc H2O

Question 12

What is the formula for compliance and resistance?

Answer 12

C = ΔV/ΔP (compliance)
Raw = PTA/flow (resistance)

Question 13

Explain how changes in lung compliance affect the peak pressure measured during inspiration with a mechanical ventilator.

Answer 13

compliance measurements are made during static or no-flow conditions (e.g., this is the airway pressure measured at end inspiration; it is designated as the plateau pressure). Thus these compliance measurements are referred to as static compliance or static effective compliance.

Question 14

Describe the changes in airway conditions that can lead too increased resistance?

Answer 14

• Artificial airway
• Any pathological condition

Question 15

Give the percentage of passive filling (or emptying) for one, two, three, and five time constants?

Answer 15

One time constant =63%
Two time constants=86%
Three time constants=95%
Four time constants = 98%
Anything’s after 5 is 100%

Question 16

Briefly discuss the principle of operation of negative pressure?

Answer 16

With this device, the patient’s head and neck are exposed to ambient pressure while the thorax and the rest of the body are enclosed in an airtight container that is subjected to negative pressure (i.e., pressure less than atmospheric pressure).

Question 17

Define baseline pressure and positive end-expiratory pressure?

Answer 17

Airway pressures are measured relative to a baseline value.

Sometimes the baseline pressure is higher than zero, such as when the ventilator operator selects a higher pressure to be present at the end of exhalation.

Question 18

Describe the measurement of plateau pressure.

Answer 18

At the point of breath holding, the pressures inside the alveoli and mouth are equal (no gas flow). However, the relaxation of the respiratory muscles and the elastic recoil of the lung tissues are exerting force on the inflated lungs. This creates a positive pressure, which can be read on the manometer as a positive pressure. Because it occurs during a breath hold or pause, the manometer reading remains stable and “plateaus” at a certain value.

Question 19

Briefly discuss the principle of operation of positive pressure?

Answer 19

occurs when a mechanical ventilator is used to deliver air into the patient’s lungs by way of an endotracheal tube or positive pressure mask.

Question 20

Briefly discuss the principle of operation of high frequency ventilation?

Answer 20

HFPPV can be accomplished with a conventional positive pressure ventilator set at high rates and lower than normal tidal volumes. HFJV involves delivering pressurized jets of gas into the lungs at very high frequencies. HFOV ventilators use either a small piston or a device similar to a stereo speaker to deliver gas in a “to-and-fro” motion, pushing gas in during inspiration and drawing gas out during exhalation.

Question 21

Define peak inspiratory pressure and plateau pressure?

Answer 21

This is the highest pressure
recorded at the end of inspiration.

The plateau pressure is measured after a breath has been delivered to the patient and before exhalation begins.