Basic Pulmonary Physiology Flashcards Preview

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Flashcards in Basic Pulmonary Physiology Deck (29):
1

Muscles of inspiration

-diaphragm (normal inspiration)
-strap muscles: all scalenes (normal) and SCM (deep inspiration)
-external intercostals
-large back muscles, paravertebral muscles, shoulder girdle, and pec muscles (maximal effort)
*inspiration is an active process

2

Muscles of expiration

-internal intercostals
-abdominal muscles
*expiration is a passive process

3

Three "segments" of airways

1. conducting airways: large cartilaginous airways and non-cartilaginous airways including "terminal" bronchioles
2. Respiratory airways: respiratory bronchioles which have partial gas exchange
3. Alveoli: clusters, primary site of gas exchange

4

Major contributor of airway resistance

Conducting airways
-90% of resistance

5

Reynold's number

(density x velocity x diameter)/(viscosity)

*a number greater than 2,000 means turbulent flow

6

Poiseuille's Law

Describes laminar flow through a tube

Q = (πPr^4)/(8nl)

Q is flow rate, n is viscosity, l is length

So...

P = (8Qnl)/(πr^4)

*eg. airway resistance (P) will increase with decreasing radius, increasing length of airways, and increased viscosity

7

LaPlace's Law

Describes pressure within the alveoli

Pressure = (2 x wall tension x wall thickness) / (radius)

8

Pleural pressure is most negative at which lung volume

Total Lung Capacity

9

Alveolar Gas Equation

PAO2 = FIO2 (PATM – PH2O )– PaCO2 / RQ

10

How is CO2 formed?

Carbonic anydrase

H+ + HCO3- H2CO3 H20 + CO2

*BBB is permeable to CO2, but impermeable to H+ and HCO3-

11

Respiratory Quotient

RQ = (VCO2) / (VO2)

*normal VCO2 is 200 ml/min, normal VO2 is 250 ml/min, thus normal RQ is 0.8

12

Changes in CO2 responsiveness curves

Right shift: describes ventilation depressants (sedative doses of opioids, barbiturates, and benzodiazepines)

Right shift AND slope reduction: very high dose opioids and volatile anesthetics at 1 MAC

13

Pathologies that increase dead space

-decreased CO
-PE
-COPD
-ARDS

14

How much does dead space increase with mechanical ventilation compared to spontaneous ventilation?

50%

*normally, 2/3 of TV contributes to ventilation and 1/3 to dead space

15

Three venous systems that contribute to anatomic shunt

-Thebesian veins
-Bronchiolar veins
-Pleural veins

16

Normal A-a gradient on room air?

Normal A-a gradient on 100% FiO2?

Room air:

17

Normal P/F ratio (paO2/FiO2)

>300

18

Ventilation-Perfusion Index (VQI)

VQI = (1-SaO2)/(1-SmvO2)

*essentially shunt fraction
normal VQI = (1-0.99)/(1-0.75) = 0.01/0.25 = 4%

19

Shunt fraction at which increasing FiO2 increases pO2 very little

>30%

*at 40%, almost no effect on pO2 with increased FiO2

20

How do changes in FRC impact shunt?

-Decreases in FRC increases shunt (increase venous admixture)
-Increases in FRC decreases shunt (increase V/Q ratio)

21

FEF 25%-75%

-effort independent
-early indicator of obstructive disease
-indicative of medium-sized airway disease
-fairly variable within an individual
-sensitive, not specific

22

Smoking Cessation Effects

- 2 to 4 weeks for ciliary function to return to normal
- increased sputum production immediately following cessation of smoking
- reduced carboxyhemoglobin levels within one day
- full benefit of smoking cessation is realized 8 weeks preop

23

Typical EKG findings in COPD

Right heart strain
-poor R-wave progression
-enlarged P-waves (P pulmonale)
-R waves greater than S saves in V1
-RBBB
-RAD
-low voltage (hyperinflation)

*increased incidence of MAT (multifocal atrial tachycardia)

24

Effects of abdominal surgery on pulmonary system

-decreases FRC-->decreasing lung compliance-->increasing shunt and hypoxia
-FRC decreases due to a 25% loss in ERV (but RV actually increases 10%)
-TV and TLV each decrease 20%

*effects worst 24 hours post-op and return to normal in 2 weeks

25

Anatomic estimate for level of carina

sternal angle

26

Static compliance

Volume/Pressure

TV / (plateau pressure - PEEP)

27

Dynamic compliance

Volume/Pressure

TV / (peak pressure - PEEP)

28

Resistance flow

Peak pressure - plateau pressure

29

Peak pressure vs plateau pressure

Peak pressure measures airway compliance (pressure)

Plateau pressure measures alveolar pressure (respiratory system compliance)