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Pulm > Equations > Flashcards

Equations Flashcards

1
Q

Flow (F or Q)

A

deltaP / R
P= pressure difference between atm and alv
R= resistance

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2
Q

minute ventilation (Vmv)

A

Vi x f
Vi= tidal volume
f= respiratory rate

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3
Q

alveolar ventilation (Valv)

A

(VT - VD) x respiratory rate
VT= tidal volume
VD= dead space
slow, deep breaths increase alveolar ventilation

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4
Q

Pressure (P)

A

F/A
F= force
A= area

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5
Q

ideal gas law

A 
PV= nRT
P= pressure
V= volume
n= moles
R= gas constant
T= temperature
gas phase: BTPS
liquid (blood): STPD
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6
Q

Boyle’s Law

A

P1V1 = P2V2

at constant T and constant number of molecules

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7
Q

Trans-respiratory system pressure (Prs)

A

Palv - Patm
determines air movement in/ out of lungs
Palv= alveolar pressure
Patm= atmospheric pressure

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8
Q

transpulmonary or transmural pressure (Ptp)

A 
Palv - Pip
Palv= alveolar pressure
Pip= intrapleural pressure
determines inflation of lung
positive: lung inflated
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9
Q

Compliance (C)

A

deltaV/ deltaP
V= lung volume
P= Palv

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10
Q

Laplace’s Law

A 
P= 2T/r
T= tension; r= radius, P=pressure
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11
Q

Resistance (R)

A 
(8nl)/ (πr^4)
n= viscosity
l= length
r= radius
medium bronchioles: highest resistance (small ones are in parallel
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12
Q

Partial pressure of oxygen (Po2)

A

Patm x FIO2

Fo2= oxygen percentage= 0.21

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13
Q

Partial pressure of oxygen inspired (PIO2)

A

(Patm- partial pressure of water vapor) x FIO2
partial pressure of water vapor= 47 mmHg
Fo2= 0.21

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14
Q

Concentration of gas (Cx)

A 
alpha(Px)
alpha= solubility of gas in solution
Px= partial pressure
(this is for dissolved gas only; NOT bound gas)
CO2 greater solubility than O2
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15
Q

Fick’s Law of Diffusion

A 
rate of DIFFUSION
gas flow (vol/time) = (A x D x (deltaP)) / z
A= area
z= thickness
D= diffusion constant
P= partial pressure of gas
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16
Q

Alveolar PCO2 (PACO2)

A

k (VCO2/Valv)
k= constant (863)
Valv= alveolar ventilation
VCO2= rate of CO2 production
at sea level: 100 mmHg is normal
determined by CO2 production: no CO2 in inspired gas
if CO2 production is constant, then PACO2 determined by alveolar ventilation

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17
Q

Alveolar PO2 (PAO2)

A

PIO2- (PaCO2/R)
PIO2= inspired O2
PaCO2= arterial PCO2
R= CO2 production/ O2 consumption

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18
Q

A-a gradient

A 
PAO2- PaO2
PAO2= alveolar
PaO2= arterial
increased: indicates lung disease
normal: excludes structural lung disease
normal: (age + 4) / 4
19
Q

Physiologic dead space (VD)

A 
VT x (PaCO2 - PEco2) / Paco2
VT= tidal volume
PaCO2= arterial PCO2
PECO2= PCO2 of mixed expired air
estimate: using weight in pounds
20
Q

O2 content of blood

A

(O2 binding capacity x % saturation) + dissolved O2 in plasma
NOT affected by hemoglobin

21
Q

What does a right shift of the hemoglobin saturation curve indicate?
What factors affect it?

A

decreased affinity for O2: want in tissues

  1. increased PCO2
  2. decreased pH
  3. increased T
  4. increase 2.3-DPG
22
Q

What does a left shift of the hemoglobin saturation curve indicate?
What factors affect it?

A

increased affinity for O2: want in pulmonary circulation

  1. decreased PCO2
  2. increased pH
  3. decreased T (hypothermia)
  4. Fetal Hb
  5. decreased 2,3-DPG
23
Q

2, 3 diphosphoglycerate

A

binds strongly to deoxygenated Hb, lowering its affinity for O2
increased in hypoxia

24
Q

Factors that affect O2 content of blood

A
  1. CO poisoning
  2. anemia
  3. hypoxemia
  4. cyanide poisoning
25
Q

What causes respiratory acidosis?

A

hypoventilation

ex: inhibition of respiratory center, paralysis of respiratory muscles, obstruction, poor gas exchange

26
Q

What causes respiratory alkalosis?

A

hyperventilation

ex: stimulation of respiratory center, hypoxemia, mechanical ventilation

27
Q

dorsal respiratory group (DRG)

A

provides rhythmic drive to ventral medullary group

causes inspiration

28
Q

ventral respiratory group (VRG)

A

causes expiration in exercise (normally passive)

29
Q

water vapor pressure (P(H20))

A

47 mmHg

30
Q

fraction concentration of O2 (FIO2)

A

0.21

31
Q

fraction concentration of N2 (FIN2)

A

0.78

32
Q

tissue O2 consumption

A

250 ml/min

33
Q

CaO2 (O2 content)

A 
(K x Hb x SaO2) + O2 dissolved in plasma
Hb= hemoglobin
SaO2: O2 saturation of Hb
K= 1.39
O2 dissolved in plasma= negligible and ignored= 0.003 x PaO2
normal= 20 ml/dl
34
Q

respiratory quotient (R)

A 
VCO2/VO2
VCO2= CO2 produced
VO2= oxygen consumed
normal: 0.8
depends on what we eat
normal: 0.8
on 100% O2= 1
carbs= 1
fat= 0.7
protein: 0.8
35
Q

Delivery of O2 to tissues (DO2)

A

CO x CaO2 x 10
CO = cardiac output
CaO2= O2 content
10= because CaO2 is ml/dl and DO2 is in ml/min
Can: convert CO to mL (multiply by 1000), convert CaO2 to just ml (multiply by 0.001/0.1)

36
Q

cardiac output (CO)

A

HR x SV
HR= heart rate
SV= stroke volume
normal= 5L

37
Q

diffusion coefficient (D)

A

(constant x alpha) / (square root MW)
alpha= solubility
CO2 diffuses 20x faster than O2 because it is more soluble

38
Q

pulmonary vascular resistance (PVR)

A

(Ppa- PLa)/ CO
Ppa= pulmonary artery pressure
PLa= left atrial pressure (pulmonary wedge pressure)
CO= cardiac output

39
Q

pulmonary HTN

A

greater than 25 mmHg at rest

40
Q

When do pulmonary vessels constrict?

A

low O2: depol of pulmonary vascular sm. muscle cells open voltage gated Ca channels, lead to Ca entry and cell contraction
opposite of systemic

41
Q

VA/Q

A

ventilation / perfusion

42
Q

anatomic dead space (VDanat)

A

air that remains in the conducting airways at end inspiration
increases with increasing lung volume

43
Q

alveolar dead space (VDalv)

A

alveoli ventilated but not perfused
decreases with exercise
increase is ALWAYS pathologic

Pulm (11 decks)

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