Chapter 3; How a Breath Is Delivered

Chapter 3; How a Breath Is Delivered

 

Complete Chapter Questions With Answers

 

Sample Questions Are Posted Below

 

MULTIPLE CHOICE

 

1. The equation of motion describes the relationships between which of the following?

a.	Pressure and flow during a mechanical breath
b.	Pressure and volume during a spontaneous breath
c.	Flow and volume during a mechanical or spontaneous breath
d.	Flow, volume, and pressure during a spontaneous or mechanical breath

 

 

ANS:   D

The mathematical model that relates pressure, volume, and flow during ventilation is known as the equation of motion for the respiratory system. This means that: Muscle pressure + Ventilator pressure = (Elastance x Volume) + (Resistance x Flow)

 

DIF:    1                      REF:    pg. 30

 

2. The equation of motion is represented by which of the following?

a.	PTA = PA x Raw
b.	PTR = Paw + PA
c.	Pvent + Pmus = Raw + PTA
d.	Pvent + Pmus = Raw x

 

 

ANS:   B

The transrespiratory pressure (P_TR) is the pressure generated by either the patient contracting the respiratory muscles or by the ventilator pushing the volume into the patient. This pressure is opposed by the elastic recoil pressure (P_E) and the flow resistance pressure (P_R). The transairway pressure (PTA) is the pressure gradient between the airway opening and the alveolus. This produces airway movement in the conductive airways. It represents only part of the equation of motion, the pressure needed to overcome the airway resistance. The equation of motion may be represented, on one side, by P_vent + muscle pressure (P_mus)_. However, this is equal to the elastic recoil pressure (V/C) plus the flow resistance pressure (R_aw x ) or P_vent + P_mus = V/C + (R_aw x ).

 

DIF:    1                      REF:    pg. 30

 

3. How many variables can a ventilator control at one time?

a.	One
b.	Two
c.	Three
d.	Four

 

 

ANS:   A

As the equation of motion shows, the ventilator can control four variables: pressure, volume, flow, and time. It is important to recognize that the ventilator can control only one variable at a time.

 

DIF:    1                      REF:    pg. 30

 

4. Calculate the transrespiratory pressure given the following information: volume 0.6 L; compliance 1 L/cm H₂O; airway resistance 3 cm H₂O/L/sec; flow 1 L/sec.

a.	0.9 cm H2O
b.	1.8 cm H2O
c.	3.6 cm H2O
d.	4.6 cm H2O

 

 

ANS:   C

Transrespiratory pressure (P_TR) = P_vent + P_mus = V/C + ( R_aw x ).

 

DIF:    2                      REF:    pg. 30

 

5. An increase in airway resistance during volume-controlled ventilation will have which of the following effects?

a.	Volume increase
b.	Flow decrease
c.	Pressure increase
d.	Rate decrease

 

 

ANS:   C

When a ventilator is volume-controlled the ventilator will maintain the volume, which will remain unchanged, along with the flow, but the pressure will vary with changes in lung characteristics. An increase in airway pressure will require more pressure to deliver the set volume. The set rate is independent of the changes in pressure.

 

DIF:    2                      REF:    pg. 32