Respiratory Physiology Equations

Front 1

Fick's Law of Diffusion

Back 1

volume of gas moved by diffusion =
proportional to area of membrane
inversely proportional to thickness of membrane

Front 2

transpulmonary pressure (Ptp) =

Back 2

PA - Ppl
alveoli pressure minus intrapleural pressure

Front 3

Airway resistance =

Back 3

(Patm -Palv)/flow rate

Front 4

resistance in a tube =

Back 4

R = (8 n l) / (pi r^4)

Front 5

Boyles Law

Back 5

PV = nRT

as volume increases, pressure must decrease

Front 6

as long volume decreases, resistance...

Back 6

increases, think of smaller endotracheal tubes

Front 7

Inspiratory Capacity

Back 7

IC = VT + IRV

tidal volume plus inspiratory reserve volume
(maximum lung inspiration)

Front 8

FRC (functional residual capacity)

Back 8

FRC = RV + ERV

residual volume (volume that always stays) plus expiratory reserve volume ( air that can still be pushed out with force)

FRC is air remaining in lungs after normal passive expiration

Front 9

Vital Capacity

Back 9

VC = IRV + VT + ERV

reserve volumes plus tidal volume
amt of air that can be expelled from lungs following forceful inspiration and expiration

Front 10

Total Lung Capacity

Back 10

TLC = VC + RV

vital capacity plus residual volume
maximum volume of air that lungs can hold

Front 11

closing volume

Back 11

must be less than FRC or lungs will collapse

Front 12

minute respiratory volume

Back 12

Vmin = VT + respiratory rate (f)

minute volume = ventilation

Front 13

anatomic dead space

Back 13

ventilated (globally) but no gas exchange occurs
a collapsed alveolus is not a part of dead space b/c not being ventilated anymore

Front 14

alveolar dead space

Back 14

still ventiated normally but no vasculature perfusion

V/Q > 1

Front 15

physiologic dead space (Vd)

Back 15

anatomic plus alveolar dead space

Front 16

Bohr equation (Vd)/(VT)

Back 16

physiological dead space / tidal volume

how much tidal volume is going to fill up dead space
Vd/VT = (PaCO2 - PeCO2)/PaCO2
have to determine CO2 elimination by capnometer and PaCo2 by blood gas analysis

*value can never be zero, will always have dead space

Front 17

Rate of alveolar ventilation (VsubA)

what amt of minute volume is actually getting to alveoli

Back 17

V subA = frequency (f) x (VT - Vd)

have to subtract physiological dead space

to increase V subA you either have to breath deeper (VT) or breath faster (f)

Front 18

Vascular resistance =

Back 18

vascular resistance = (input pressure - output pressure)/blood flow

input pressure = pulmonary artery
output pressure = Left atrium

Front 19

Zone 3 dynamics

Back 19

Ppa > Ppv > P subA

distension of capillaries within the alveolar spaces, increased perfusion

Front 20

ZOne 2 dynamics

Back 20

Ppa > P subA > Ppv

positive pressure ventilation can push down vasculature, P subA can become greater than MAP, perfusion not as good

Front 21

Zone 1 dynamics

Back 21

P subA > Ppa > Ppv

collapse of vasculature, no blood flow

Front 22

ZONE dynamics at rest in healthy individual

Back 22

lungs mostly in zone 3, very small amt. near hilus in zone 2

Front 23

ZONE dynamics during exercise

Back 23

MAP increases the pressures in the vasculature, so that more of the lung is in zone 3 (instead of 2)

Ppa > P subA

Front 24

V/Q ratio for alveolar edema

Back 24

V/Q < 1

fluid accumulation in alveoli themselves, creates physiologic R to L shunt, perfusion occurring at same rate but no ventilation

Front 25

V/Q > 1

Back 25

alveolar dead space

ventilation exceeds perfusion

Front 26

V/Q < 1

Back 26

physiologic R to L shunt

Front 27

Henry's Law

Back 27

concentration of a gas in solution is proportional to its partial pressure

gas pressures are essentially due to the number of molcules present
P=nC derived from Boyle's Law

Front 28

Alveolar Gas Equation (relates the decrease in alveolar oxygen to the increase in alveolar carbon dioxide during hypoventilation)

Back 28

PalvO2 = PiO2 - (PalvCO2/R)

PalvCO2 should be equal with PaCO2 in arterial blood
PiO2 is partial pressure of inspired oxygen ( 21% x barometric pressure - water vapor pressure (47 mmHg))
R is respiratory quotient = 0.8

hypoventilation, inadequate removal of CO2 lowers alveolar partial pressure of oxygen

Front 29

95-100% saturation of Hemoglobin in mammals

Back 29

PaO2 is 100 mmHg in arterial blood

Front 30

75% saturation of hemoglobin in mammals

Back 30

PaO2 is 40 mmHg in arterial blood

Front 31

50% saturation of hemoglobin in mammals

Back 31

PaO2 is 28 mmHg in arterial blood

Front 32

Lower pH does what to hemoglobin

Back 32

decreased affinity for O2, less saturation, right shift

Front 33

lower pH does what to hemoglobin

Back 33

increased affinity for O2, greater saturation, left shift

Front 34

Total O2 content of blood (sum of Hb-O2 and dis-O2)

Back 34

Hb-O2 = (Hb concentration) x 1.34 x %saturation
dis-O2 = PaO2 x 0.003

Total = Hb-O2 plus dis-O2 = (mL O2/ dL)

Front 35

carbon dioxide to bicarbonate molecular equation

Back 35

CO2 + H2O <--> H2CO3 <--> H+ + HCO3-

Front 36

Oxygen Delivery

Back 36

total O2 content x CO
mL O2/dL dL/min = mL O2/min

Front 37

average Aleveolar pO2

Back 37

104 mmHG

Front 38

average pO2 at arterial end of pulmonary capillary

Back 38

40 mmHg

Front 39

Hering Breuer Inflation Reflex

Back 39

increase lung volume -> stretch receptors fire -> decrease respiratory frequency by increasing the expiratory time

Front 40

Parts of Central Controller in CNS

Back 40

1. Cerebrum - voluntary
2. Brainstem- neurons in pons and medulla
3. spinal cord
4. limbic system and hypothalamus

Front 41

Parts of the Respiratory COntrol System

Back 41

Sensors (stretch, chemo)
Central Controller
Effectors (muscles of respiration, diaphragm)

Front 42

medullary respiratory center

Back 42

basic rythym
has 2 groups-- dorsal (inspiration)
ventral (expiration, extreme exercise makes it active)

Front 43

apneustic center

Back 43

sustains inspiration by prolonging inspiratory ramp signal

Front 44

pneumotaxic center

Back 44

switches off inspiration so as to stimulate expiration

Front 45

What molecule diffuses across the blood brain barrier?

Back 45

CO2

Front 46

WHat are PCR's?

Back 46

Peripheral Chemoreceptors located at carotid and aoritc arch

Front 47

what makes up the conducting airways?

Back 47

trachea, bronchi, up to terminal bronchioles

Front 48

what makes up respiratory zone?

Back 48

respiratory bronchioles, alveolar ducts and alveoli

Front 49

what areas are most affected by asthma, bronchitis?

Back 49

areas of large amounts of smooth muscle-- smaller bronchioles have the largest amt of smooth muscle

Front 50

if CO2 is decreasing in the face of constant metabolism then what is occurring?

Back 50

hyperventilation -> PCO2 is less than 35 mmHg

Front 51

large and medium sized particles are removed how?

Back 51

mucociliary escalator

Front 52

small sized particles are removed how?

Back 52

macrophages in alveoli

Front 53

mucociliary escalator exists all the way to where?

Back 53

nasal passages to terminal bronchioles

Front 54

in disease, where is the greatest resistance to flow?

Back 54

small bronchioles- they are easily occluded and lots of smooth muscle

Front 55

in health, where is greatest resistance to flow?

Back 55

medium sized brochioles, b/c the small bronchioles out-number them in cross-sectional area

Front 56

wheeze

Back 56

small airway obstruction or collapse, sides are vibrating, continuous sound on expiration

Front 57

crackles

Back 57

discontinuous, heard on inspiration and expiration, bubbling through mucous plugged airways

Front 58

coughing

Back 58

stimulated by subepithelial irritant receptors, close epiglottis momentarily and then forcefully exhale air causing extreme pressure, air explodes through non-cartilaginous parts of trachea b/c of partial collapse there

Front 59

sneeze

Back 59

irritation to nasal passageways, similar to cough reflex

Front 60

panting

Back 60

functions in temperature regulation, respiratory center is responding to core body temp., heat dissipated by increasing anatomical dead space ventilation, evaporation of water

Front 61

pleonastic

Back 61

using more words than necessary

Front 62

quiet breathing

Back 62

primary function of diaphragmatic movement

Front 63

during inspiration...

Back 63

the diaphragm contracts, lungs expand caudally

Front 64

during expiration...

Back 64

diaphragm relaxes, elastic recoil of lungs

Front 65

heavy breathing involves what muscles?

Back 65

muscles of inspiration: external intercostals, serratus dorsalis cranialis, dorsal scalenus --> need to lift and expand rib cage

muscles of expiration: rectus abdominus, internal intercostals

Front 66

transpulmonary pressure

Back 66

Ptp = PA - Ppl

lung inflation is maintained by the transpulmonary pressure