Barron's CCRN: Pulmonary Exam 2025
Questions and Answers
Ventilation - ANSWER-Movement of air in from the atmosphere and out from
the body to maintain appropriate concentration of O2 and CO2
Primary control= brain stem (central control)
--Senses blood pH; decrease in pH -> ventilation is stimulated
--Decrease in pH= *acidosis*, results in increase rate and/or depth of breathing
Secondary control= peripheral control (PaO2 "sensors" in aortic arch)
--Senses PaO2 in blood; decrease PaO2= ventilation stimulated
--Chronic PaO2 retainers rely on *hypoxemia* for ventilator drive (if PaO2 is
corrected to normal, may result in decreased drive to breathe)
What is the clinical indicator of ventilation? How do you know the patient is
ventilating normally? - ANSWER-*PaCO2* (NOT the PaO2)
Minute ventilation - ANSWER-*tidal volume Vt x respiratory rate RR*
Normal *~4L/min*
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
,Increase in minute ventilation= increase *work of breathing*
Primary muscle of ventilation - ANSWER-Diaphragm
--Anything that affects "health" of the diaphragm (deconditioning, hypoxemia,
acidosis, hypophosphatemia) will adversely affect ventilation
What is the position for optimal ventilation? - ANSWER-Upright sitting position
*Supine is NOT good for ventilation*
*Dead space ventilation* - ANSWER-*Volume of air that does NOT participate in
gas exchange*
--Normal to have some amount of this
--Anatomic dead space= ~2mL/kg of Vt (*no gas exchange from level of nose
down to alveoli*)
Alveolar dead space - ANSWER-alveoli that cease to act in gas exchange due to
collapse or obstruction
*Pathologic*- non-perfused alveoli, PE
Physiologic dead space - ANSWER-Anatomic dead space + alveolar dead space
Pulmonary embolus - ANSWER-Blockage of the pulmonary artery or one of its
branches due to a translocated clot
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
,*Results in increased alveolar dead space*
--A clot in the pulmonary circulation= no blood flow past alveoli in that area of
the pulmonary circulation
Main function of the pulmonary system - ANSWER-Gas exchange
--For gas exchange to occur normally, there needs to be *ventilation* and
*perfusion*
Pulmonary perfusion - ANSWER-Movement of blood through pulmonary
capillaries
--*Any decrease in blood flow past alveoli* (PE, low cardiac output) *will affect
ventilation/perfusion ratio and gas exchange*
Normal ventilation/perfusion ratio - ANSWER-4L ventilation/min (V)
--------------------------
5L perfusion/min (Q)
Ideal lung unit= *0.8 ratio*
Effect of gravity on pulmonary perfusion - ANSWER-In *upright* position: most
pulmonary blood is in the lower lung lobes
*Supine*: most pulmonary blood is posterior
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 3
, Rarely are ALL lung units perfused (eg vigorous exercise)
Clinical indications of gravity on pulmonary perfusion - ANSWER-*WANT
GOOD LUNG DOWN*
--Ex] Large right lung pneumonia- if patient is turned to the right (bad lung down),
more blood goes to the right and patient becomes hypoxemic (do not turn this
patient to the right)
V/Q mismatch - ANSWER-Problem with ventilation or perfusion
--patient will be hypoxemic on room air
--Treatment= supplemental O2 until the etiology can be determined and addressed
Shunt - ANSWER-An extreme V/Q mismatch; even 100% supplemental FiO2
will NOT correct the hypoxemia
Movement of blood from the right side of the heart to the left side of the heart
*without getting oxygenated* (venous blood to the arterial side)
*ARDS*
Treatment of a shunt - ANSWER-Give O2 (usually 100%)- does not completely
fix the problem though!
*PEEP*: increases alveolar recruitment, prevents alveolar collapse
Normal physiologic shunt - ANSWER-*Thebesian veins* of the heart empty into
the left atrium
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 4
Questions and Answers
Ventilation - ANSWER-Movement of air in from the atmosphere and out from
the body to maintain appropriate concentration of O2 and CO2
Primary control= brain stem (central control)
--Senses blood pH; decrease in pH -> ventilation is stimulated
--Decrease in pH= *acidosis*, results in increase rate and/or depth of breathing
Secondary control= peripheral control (PaO2 "sensors" in aortic arch)
--Senses PaO2 in blood; decrease PaO2= ventilation stimulated
--Chronic PaO2 retainers rely on *hypoxemia* for ventilator drive (if PaO2 is
corrected to normal, may result in decreased drive to breathe)
What is the clinical indicator of ventilation? How do you know the patient is
ventilating normally? - ANSWER-*PaCO2* (NOT the PaO2)
Minute ventilation - ANSWER-*tidal volume Vt x respiratory rate RR*
Normal *~4L/min*
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
,Increase in minute ventilation= increase *work of breathing*
Primary muscle of ventilation - ANSWER-Diaphragm
--Anything that affects "health" of the diaphragm (deconditioning, hypoxemia,
acidosis, hypophosphatemia) will adversely affect ventilation
What is the position for optimal ventilation? - ANSWER-Upright sitting position
*Supine is NOT good for ventilation*
*Dead space ventilation* - ANSWER-*Volume of air that does NOT participate in
gas exchange*
--Normal to have some amount of this
--Anatomic dead space= ~2mL/kg of Vt (*no gas exchange from level of nose
down to alveoli*)
Alveolar dead space - ANSWER-alveoli that cease to act in gas exchange due to
collapse or obstruction
*Pathologic*- non-perfused alveoli, PE
Physiologic dead space - ANSWER-Anatomic dead space + alveolar dead space
Pulmonary embolus - ANSWER-Blockage of the pulmonary artery or one of its
branches due to a translocated clot
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
,*Results in increased alveolar dead space*
--A clot in the pulmonary circulation= no blood flow past alveoli in that area of
the pulmonary circulation
Main function of the pulmonary system - ANSWER-Gas exchange
--For gas exchange to occur normally, there needs to be *ventilation* and
*perfusion*
Pulmonary perfusion - ANSWER-Movement of blood through pulmonary
capillaries
--*Any decrease in blood flow past alveoli* (PE, low cardiac output) *will affect
ventilation/perfusion ratio and gas exchange*
Normal ventilation/perfusion ratio - ANSWER-4L ventilation/min (V)
--------------------------
5L perfusion/min (Q)
Ideal lung unit= *0.8 ratio*
Effect of gravity on pulmonary perfusion - ANSWER-In *upright* position: most
pulmonary blood is in the lower lung lobes
*Supine*: most pulmonary blood is posterior
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 3
, Rarely are ALL lung units perfused (eg vigorous exercise)
Clinical indications of gravity on pulmonary perfusion - ANSWER-*WANT
GOOD LUNG DOWN*
--Ex] Large right lung pneumonia- if patient is turned to the right (bad lung down),
more blood goes to the right and patient becomes hypoxemic (do not turn this
patient to the right)
V/Q mismatch - ANSWER-Problem with ventilation or perfusion
--patient will be hypoxemic on room air
--Treatment= supplemental O2 until the etiology can be determined and addressed
Shunt - ANSWER-An extreme V/Q mismatch; even 100% supplemental FiO2
will NOT correct the hypoxemia
Movement of blood from the right side of the heart to the left side of the heart
*without getting oxygenated* (venous blood to the arterial side)
*ARDS*
Treatment of a shunt - ANSWER-Give O2 (usually 100%)- does not completely
fix the problem though!
*PEEP*: increases alveolar recruitment, prevents alveolar collapse
Normal physiologic shunt - ANSWER-*Thebesian veins* of the heart empty into
the left atrium
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 4
