Lung volumes, loops, V and Q

Question 1

FEV1

IRV

ERV

RV

Vt

Answer 1

FEV1 - forced expiatory vol in 1 second

IRV - inspiratory reserve vol.

ERV - expiratory reserve vol

RV - residual vol

Vt - tidal vol

Question 2

FVC

IC

FRC

VC

Pst

Answer 2

FVC - forced vital capacity

IC - inspiratory capacity

FRC - functional residual capacity

VC - vital capacity

Pst - Static pressure of lung

Question 3

Normal lung volume diagram

Answer 3

Question 4

Normal and abnormal FEV1/FVC

Answer 4

N: .8 or 100% predicted Abnormal: .75 in young, .7 in old, or <88%

Question 5

Definition of obstruction

Answer 5

FEV1/FVC <.70 in old. Can become hyper inflated because hard to get air out. TLC higher, Residual vol higher, longer to empty

Question 6

Definition of Restriction

Answer 6

Decreased TLC (tot. lung cap.) A decreased vital capacity or FVC does not always indicate restriction

Question 7

FRC details

Answer 7

functional residual capacity. Determined by the balance of lung elastic recoil and chest wall recoil

Question 8

Normal flow volume loop

Answer 8

voila

Question 9

Breakdown of flow volume loop

Answer 9

pic

Question 10

Flow volume loops for restrictive and obstructive

Answer 10

Obstructive = large vol, bowed look on expiration Restriction = steep expiration, narrow base

Question 11

What affects flow most at low volumes?

Answer 11

Just airway resistance. Pt effort less important.

Question 12

V and Q

Answer 12

Ventilation (the rate at which gas enters or leaves the lung)

Perfusion (the process of delivery of blood to a capillary bed)

Question 13

V/Q ratio

Answer 13

a measurement used to assess the efficiency and adequacy of the matching of these two variables in the lung

Question 14

change in alveoli diameter and ventilation from top to bottom of lung

Answer 14

Top ones more distended at baseline (gravity) than bottom. So the bottom ones can expand more than the top, so more ventilation happens in the base of lung than apex.

Question 15

How does perfusion change from top to bottom of lung?

Answer 15

not uniform. more pulm. aa. and vv. pressure at bottom than top. Veins lower pressure than aa.

Question 16

3 pressures to consider in lung vessels

Answer 16

P1 is the inflowing pressure, P2 is the pressure which must be reached by P1 before fluid will flow through the tube (ie so vessels don’t collapse), and P3 is the pressure downstream from the tube (veins).

Always ∆P = P1 - P2 or P3 (whichever is greater)

Question 17

Going top to bottom, how does ventilation and perfusion change?

Answer 17

ventilation increases, and perfusion increases but at different rates

High V/Q ratio at top.

Low V/Q at bottom.

Question 18

Anatomic and physiologic shunts

Answer 18

An anatomic shunt occurs when venous blood flows back to the circulation downstream from the lung – ie; the bronchial circulation

An intrapulmonary shunt occurs when venous blood flows through:

1. Unventilated lung
2. Heart defects
3. Shunt channels in lung

Question 19

What are interpulmonary shunts? What purpose do they serve?

Answer 19

Small vessels that allow R-L shunts around alveoli. Heavy exercise increases pulm. a. pressure, intrapulmonary shunts relieve it w/o causing pulm. edema.

Question 20

What is Dead space? What is it good for?

Answer 20

V/Q = infinite. ie. air in trachea (no exchange) or in poorly/non-perfused alveoli.

Benefits:

CO2 retained (buffer possible)

air reaches body temp

humidified (better for mucous)

Question 21

Define and give values for

mPAP

PCWP

PVR

Answer 21

mPAP = mean pulm. a. pressure, 14 +/- 3.5 mmHg

PCWP = pulm capillary wedge pressure, 2-15 mmHg

PVR = pulm. vascular resistance = (mPAP – PCWP) / CO

Question 22

What is hypoxic vasoconstriction? Purpose?

Answer 22

Vessels constrict when exposed to low O2 or high CO2 to shift flow away from these areas to better ventilated

Question 23

What is the relationship b/w dead space, shunt and V/Q mismatch?

Answer 23

Continuum: Shunt → V/Q mismatch → dead space