Pulmonary Physiology

Question 1

Muscles contract and the volume of the thorax increases
Intrapleural pressure becomes more negative
Alveolar pressure decreases
Pressure gradient causes air to flow into the lung

Answer 1

Inspiration

Question 2

Alveolar pressure becomes greater than atmospheric pressure
Elastic forces of the lung compress gas
Air flows out

Answer 2

Expiration

Question 3

the total volume expired from maximum inspiration to maximum expiration

reduced in obstructive and restrictive disease

Answer 3

Forced Vital Capacity (FVC)

Question 4

the maximum volume that can be expired in 1 second (not measured directly from flow volume loop)

reduced in restrictive disease
greatly reduced in obstructive disease

Answer 4

Forced Expiratory Volume in 1 second (FEV1)

Question 5

the ratio of FEV1 to FVC expressed as a percentage

reduced in obstructive disease
no change in restrictive disease

Answer 5

FEV1/FVC

Question 6

forced expiratory flow over the middle half of FVC

Thought to be influence more by diseases affecting the smaller airways

reduced in obstructive disease, no change in restrictive disease

Answer 6

Maximum mid-expiratory flow rate (MMEFR)

Forced Expiratory Flow 25-75 (FEF25-75)

Question 7

highest expiratory flow achieved (only measured directly from flow/volume loop)

Answer 7

Peak expiratory flow rate (PEFR)

FEF max

Question 8

vital capacity + residual volume

no change or increase in obstructive disease
decrease in restrictive disease

Answer 8

total lung capcity

Question 9

inspiratory reserve volume + tidal volume + expiratory reserve volume

Answer 9

vital capacity

Question 10

expiratory reserve volume + residual volume

Answer 10

functional residual capcity

Question 11

tidal volume + inspiratory reserve volume

Answer 11

inspiratory capacity

Question 12

Helium (inert) of a known concentration is added to a spirometer, the patient breathes until the He is dispersed throughout the air in the lungs and spirometer (equilibration)

Nitrogen washout: 100% O2 is added to a spirometer, the patient breathes until the nitrogen found in the RV is washed into the spirometer

C1 x V1 = C2 x (V1 + V2)
C1 = concentration of He in the spirometer at the start
V1 = volume of the spirometer
C2 = concentration of He in the spirometer after equilibration
V2 = FRC

Answer 12

Gas dilution method of measuring FRC

Question 13

Patient lays in an airtight box and tries to inhale against a closed mouthpiece, this results in the expansion of the lungs, lung volume increases and the box pressure rises because gas volume decreases

P1V1 = P2 (V1-deltaV), solve for deltaV
P1 = pressure in the box before inhalation
P2 = pressure in the box after inhalation
V1 = volume in the box before inhalation
deltaV = change in the volume of the box with inhalation 

P3V2 = P4(V2 + deltaV), solve for V2
P3 = mouth pressure before inhalation
P4 = mouth pressure after inhalation
deltaV = change in the volume of the box with inhalation
V2 = FRC

Answer 13

Body plethysmography to measure FRC

Question 14

change in volume divided by the change in pressure

Answer 14

compliance

Question 15

measure of diffusion across the membrane

reduced by increased thickness and surface area, disease at the alveolar capillary membrane, V/Q mismatch, anemia, poor perfusion of the membrane and very low lung volumes

Answer 15

Diffusing capacity of the lung for carbon monoxide (DLCO)

Question 16

PAO2 = FiO2 x (Patm - Pwater) - PaCO2/0.8

FiO2 = 0.21
Patm at sea level = 760 mmHg
P water = 47 mmHg
normal PaCO2 = 40 mmHg

Answer 16

Alveolar Gas Equation

Question 17

DLO2 = rate of O2 uptake/(PAO2 - PaO2)

Answer 17

Diffusion across the alveolar membrane

Question 18

Aa = PAO2 - PaO2
abnormal if > 30 mmHg
normal value = 10 mmHg

Answer 18

A-a gradient

Question 19

AV = RR x (TV - dead space)

Answer 19

Alveolar ventilation

Question 20

most superior portion of the lung
V/Q >> 1
PA>Pa>Pv
no flow
does not normally exist

Answer 20

Zone 1

Question 21

middle portion of the lung
V/Q > 1
Pa>PA>Pv
flow is proportional to Pa-PA

Answer 21

Zone 2

Question 22

inferior portion of the lung
V/Q = 1
Pa>Pv>PA
flow is proportional to Pa-Pv

Answer 22

Zone 3

Question 23

O2 delivery = CO x arterial O2 content

Answer 23

oxygen delivery

Question 24

CaO2 = 1.39(Hb)(SO2) + 0.003(PO2)

oxygen bound to hemoglobin + oxygen dissolved in plasma

Answer 24

arterial O2 content

Question 25

medullary respiratory center

Innervates inspiratory and expiratory muscles
Abdominal muscles, internal intercostal muscles, accessory muscles of inspiration

Involved in regulation of inspiratory force and voluntary expiration (active on forced expiration)
Active during heavy exercise and stress, no output during passive breathing

Nucleus ambiguous: inspiratory, upper airways

Nucleus retroambigualis
Rostral part: inspiratory, diaphragm and external intercostal muscles
Caudal part: expiratory, abdominal and internal intercostal muscles

Botzinger’s complex: expiratory, inhibits inspiratory neurons

Answer 25

Ventral respiratory group

Question 26

medullary respiratory center

within the nucleus tractus solitarius

Active with each breath
Referred to as the pacesetting center or the inspiratory center
Output signals 12-15/minute; output for 1-2 seconds, pause for 2-3 seconds to allow expiration
Output signals diaphragm and external intercostal muscles

Answer 26

Dorsal Respiratory Group

Question 27

pontine area that sends input to medulla

regulates rate and depth of respiration by cyclical inhibition of inspiration
Receives input from the cerebral cortex
Coordinates speed of inhalation and expiration
Sends inhibitory signals to the DRG
Involved in fine tuning of respiration rate

Answer 27

Pneumotactic center

Question 28

pontine area that sends input to medulla

stimulates inspiration and is antagonized by the pneumotactic center
Promotes inspiration and controls depth of breathing
Signals to the DRG
Sends stimulatory impulses to the inspiratory area, inhibited by stretch receptors

Answer 28

Apneustic center

Question 29

located at the ventrolateral surface of the medulla and respond indirectly to changes in PaCO2 allowing acute regulation of PaCO2

The most powerful stimulus known to influence the respiratory components of the medulla (DRG, VRG) is H+ in the CSF, an indirect measure of PaCO2

BBB is impermeable to HCO3- and H+ but CO2 diffuses readily into the CSF
Increased PaCO2 –> decrease CSF pH –> detection by central chemoreceptors –> increased RR
Decreased PaCO2 –> increased CSF pH –> detection by central chemoreceptors –> decreased ventilation

Answer 29

Central chemoreceptors

Question 30

located in the carotid bodies and convey information to the respiratory center thereby affecting ventilation

Respond directly to changes in PaO2, PaCO2, and pH

Decreased PaO2, increased PaCO2, decreased pH –> increased ventilation

Changes in ventilation due to changes in PaO2 are small when PaO2 is above 60mmHg, very responsive if PaO2 falls below 60 mmHg

Once PaO2 falls below 30 mmHg, receptors become less effective

respond directly to PaCO2 but less responsive to changes

Affected by changes of H+ concentration in arterial blood independent of PaCO2 - Lactic acid, ketones

respond to hypoperfusion, nicotine, increased temperature, PaCO2

sensitive to PaO2 not total O2 content - PaO2 might be normal, represents the O2 free in the blood, but the O2 content might be low when hemoglobin is absent or nonfunctional as in chronic anemia, carbon monoxide poisoning, methemoglobinemia

activation –> increased ventilation, peripheral vasoconstriction, increased pulmonary vascular resistance, systemic arterial hypertension, tachycardia, increase in left ventricular performance

Answer 30

Peripheral chemoreceptors

Question 31

respond to inflation of the lung and result in termination of inspiration

Afferent signals from receptors in airway smooth muscle (bronchi/bronchioles) and visceral pleura are transmitted through the vagus to the medulla where they inhibit the apneustic center terminating inspiration
Hering-Breuer reflex
More active in newborns than adults

Answer 31

pulmonary mechanoreceptors

Question 32

in the large airways, respond to noxious gases and particular matter
Activation results in afferent signals to the CNS through the vagus causing reflexive bronchoconstriction and coughing

Answer 32

irritant receptors

Question 33

in the alveoli, stimulated by hyperinflation of the lungs and various chemical stimuli and signaling results in reflexive, rapid, shallow breathing.

Small C fibers located in the small conducting airways, blood vessels, and interstitial tissue between the capillaries and the alveolar walls

Respond to alveolar inflammation, pulmonary capillary congestion/edema, serotonin/bradykinin, pulmonary emboli

Answer 33

Juxtacapillary receptors

Question 34

stimulated during movement of joints and muscles, producing an increased respiratory rate.

Proprioreceptors play an important role in initiating and maintaining increased ventilation during exercise

Sudden pain causes apnea, prolonged pain causes hyperventilation

Answer 34

joint and muscle mechanoreceptors

Question 35

deoxygenation of the blood increases the ability of Hb to carry CO2

O2 shifts the CO2 dissociation curve to the right

low PaO2 in tissues faciliates CO2 loading, high PaO2 in the lungs facilitates CO2 unloading

Answer 35

The Haldane Effect

Question 36

oxygen consumption (VO2) / oxygen delivery (DO2)

at rest = 20%, may increase to 80% with exertion

Answer 36

extraction ratio

Question 37

oxygen bound to Hb + oxygen dissolved in plasma

CaO2 = 1.39(Hb)(SaO2) + 0.003(PaO2)

Answer 37

arterial O2 content