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CP Fall19 Final > Pulmonary Equations > Flashcards

Pulmonary Equations Flashcards

1
Q

Boyles Law

A

P1V1 = P2V2 (pressure gradient that drives gas flow)

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2
Q

Charles Law

A

V1/V2 = T1/T2

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3
Q

Dalton’s Law

A

P total = P gas (x)

DSA:

Px = (Pb - Pw) x F

Pb: barometric pressure
Pw: water vapor pressure (74mmHg)

F values: O2 = 21% ; N2 = 79%

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4
Q

Henry’s Law

A

Cx = kPx ; Pgas (in fluid) = [gas] / solubility

C: content of dissolved gas proportion to partial pressure
k: solubility constant
P: partial pressure

Example: If arterial blood PCO2 = 40mmHg + k (solubility constant) = .06mL CO2/dL blood/mmHg

C CO2 = .06 x 40 = 2.4mL/dL

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5
Q

Transpulmonary pressure (PL)

A

PL = PA - PPL

PA: intrapulmonary pressure
PL: intra pleural pressure

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6
Q

Across chest wall (PW)

A

PW = PPL - PBS

PPL: intra pleural pressure
PBS: pressure at body surface

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7
Q

Pressure across respiratory system (PRS)

A

PRS = PA - PBS

PA: intrapulmonary pressure
PBS: pressure at body surface

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8
Q

Transairway pressure (PTA)

A

PTA = PAW - PPL

PAW: air way pressure
PPL: intra pleural pressure

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9
Q

Transpulmonary pressure

Pneumothorax Example

A

PL = PA - PPL

PA: intrapulmonary pressure
PPL: intra pleural pressure

2 ways to to re-inflate lung clinically:

PPL = 0 ; PA = +5 ; PL = +5 - 0 = +5 (add + pressure in air way)

PPL = -5 ; PA = 0 ; PL = 0 - (-5) = +5 (recreate (-) intrapleural pressure)

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10
Q

End of Exhalation

Transpulmonary pressure

A

PA - PPL = 0 - (-5) = +5 cm H2O

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11
Q

During Inspiration

Transpulmonary pressure

A

PA - PPL = -2 - (-8) = +6 cm H2O

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12
Q

Lung Volumes during inspiration/expiration

A

End of inhalation: Lung volume = FRC + Vt

Start of Exhalation: Lung volume = FRC

FRC: functional residual capacity

Vt: tidal volume

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13
Q

Vital Capacity (VC)

A

VC = IRV + Vt + ERV ; VC = IC + ERV

IRV: inspiratory reserve volume (normal: 3000mL)
Vt: tidal volume (normal: 500mL)
ERV: expiratory reserve volume (normal: 1000mL)
IC: inspiratory capacity

Example: VC = 3000 + 500 + 1000 = 4500mL (normal)

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14
Q

Total lung capacity (TLC)

A

TLC = VC + RV ; TLC = IC + FRC ; TLC = Vt + ERV + IRV + RV

VC: vital capacity (normal: 4500mL)
RV: residual volume (normal: 1200mL)
IC: inspiratory capacity (normal: 3500mL)
FRC: functional residual capacity (normal: 2200mL)

Example: TLC = 4500 + 1200 = 5700mL (normal)

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15
Q

Functional residual capacity (FRC)

A

FRC = ERV + RV

ERV: expiratory residual volume (normal: 1000mL)
RV: residual volume (normal: 1200mL)

Example: FRC = 1000 + 1200 = 2200mL (normal)

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16
Q

RV/TLC’s

A

Normal < .25

Emphysema (increased RV)

Fibrosis (decreased TLC)

Pathology > .25

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17
Q

Compliance

A

C = ∆V / ∆P (units: mL/ cm H2O)

reflection of distensibility, measure of elastic properties of lung (higher compliance = easier to stretch)

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18
Q

Recoil

A

R= 1/C

tendency of an object to oppose stretch (lung)

High compliance = less recoil; low compliance = more recoil

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19
Q

La Place’s Law

A

P = 2T / r

P: net pressure in gas filled sphere

T: surrounding surface tension

r: radius of sphere

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20
Q

Respiratory system compliance (Crs)

A

Crs = 1/Cl + 1/Ccw

Cl: compliance of lung

Ccw: compliance of chest wall

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21
Q

Airflow through tube due to a pressure difference between 2 ends of tube

A

AF = ∆P / R

AF: airflow
R: resistance to AF
∆P: difference between barometric pressure (Pb) at open mouth and pressure at alveolus (PA): ∆P= Pb - PA

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22
Q

Resistance (laminar)

A

R = ∆P / flow (units: cm H2O/L/sec)

R = 8 L n / π r^4

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23
Q

Laminar flow / Turbulent flow

A

Re (Reynolds # < 1000) = laminar ; P = flow rate x R

Re (Reynolds #> 2000) = turbulent ; P ∝ (flow rate)^2

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24
Q

Reynolds number

A

Re = 2rvd / n

r: radius
n: viscosity
v: velocity
d: diameter

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25
Q

Airway Resistance

A

In parallel…

1/R total = 1/R1 + 1/R2 + 1/R3…

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26
Q

Work of breathing (W)

A

W = P x ΔV

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27
Q

Metabolic Acidosis

A

Primary disorder: increased production of H+ by tissues

Compensatory response: hyperventilation expires CO2

[H+] increased; pH decreased
pCO2 decreased; HCO3- decreased

28
Q

Metabolic Alkalosis

A

Causes: prolonged vomiting, potassium deficiency

Primary disorder: excessive loss of H+ and ovum depletion

[H+] decreased; pH increased
pCO2 increased; HCO3- increased

29
Q

Respiratory Acidosis

A

Causes: choking, bronco-pneumonia, acute exacerbation of asthma, chronic obstructive airways disease

Primary disorder: insufficient expiration of CO2 from lungs

[H+] increased; pH decreased
pCO2 increased; HCO3- increased

30
Q

Respiratory Alkalosis

A

Causes: hysterical over breathing, mechanical over ventilation, hypoxia

Primary disorder: excessive expiration of CO2 by hyperventilation

[H+] decreased; pH increased
pCO2 decreased; HCO3- decreased

31
Q

Alveolar Gas Equation

A

PAO2 = PIO2 - PaCO2 / R

R= .8

32
Q

Normal Lung Volume Values

A

Vt (Tidal volume) = 500mL
IRV (inspiratory reserve volume) = 3000mL
ERV (expiratory reserve volume = 1000mL
RV (residual volume) = 1200mL

33
Q

Inspiratory capacity (IC)

A

IC = Vt + IRV

IC = 500mL + 3000mL = 3500 mL (normal value)

34
Q

Clinical Spirometry

A

simple lung function test (Forced vital capacity)

most informative; measured directly from spirogram

FVC: total air exhaled during forced exhalation;

TLC spirometry test: patient forcibly exhales from TLC level

Does not measure RV (RV + TLC) ; FEV1 / FVC = 80% (normal); obstruction of airway = 47%

FEV1: forced expiratory volume in 1 second

35
Q

Alveolar pressure (PA)

A

PA = P tp + P pl

P tp: transpulmonary pressure
P pl: pleural pressure

36
Q

Force expiratory volume (FEF) OR mid-maximal expiratory flow (MMEF)

A

25-75% of vital capacity (VC)

37
Q

FVC maneuver (healthy person vs. person w/ asthma)

A

Healthy person:
FEV1 = 3.41 ; FVC = 3.81 ; 3.41/3.81 = .86

Person w/ asthma:
FEV1 = 2.1 ; FVC = 3.7 ; 2.1/3.7 = .57

38
Q

Interpreting FVC maneuver

A

RD: restrictive disease (fibrosis) ; OD: obstructive disease (COPD)

RD: VC decreased; TLC decreased; RV decreased; FEV1/FVC normal or increased; FEF normal

OD: VC normal or decreased; TLC normal or increased; RV increased; FEV1/FVC decreased; FEF decreased

39
Q

Inert gas dilution and nitrogen washout technique

A

measures FRC

V1C1 = (V1 + Vfrc) x C2

40
Q

Plethysmography

A

measures lung volumes and FRC ; based on Boyle’s law

41
Q

Diffusion capacity test (DLCO)

A

measure CO diffusion capacity; decreased w/ thickening of barrier interstitial or alveolar edema (fibrosis) ; decreases surface area for gas exchange (emphysema, tumor) ; decreased uptake by RBCs (anemia) ; V/Q mismatch

42
Q

Lung Capacity test (Plethysmography & Helium dilution methods and nitrogen washout)

A

measures amount of air that you breathe in and out (Vt) and max amount of air you can breath in and out (VC)

43
Q

Flow meter

A

measures airway resistance (Raw) and lung compliance (CL); uses esophageal balloon (Ppl)

Normal Raw: 1-3cm H2O/Lsec

Healthy normal tidal breathing:
C = ΔV/ Ppl

CL (static) about equal to CL (dynamic) = .150 - .250 L/cm H2O

44
Q

Pulmonary Vascular resistance (PVR)

A

R = ΔP / F

45
Q

Ventilation perfusion ratio (V/Q) / Healthy Lung parameters

A

Normal healthy lung:

V/Q: .8
PaO2 = 100mmHg
PaCO2 = 40mmHg
Arterial pH = 7.4

46
Q

Hypoxemia PaO2 / Hypoventilation PaCO2

A

PaO2 < 80mmHg

PaCO2 > 45mmHg

47
Q

Anatomical Shunt (R to L)

A

PAO2 - PaO2 = AaDO2 = 15mmHg

AaDO2: alveolar-arterial oxygen gradient

48
Q

Henderson Hasselbach equation

A

-pH = pK + log [HCO3-] / (.03 x PCO2)

49
Q

Fick’s Law

A

D = ΔP x area / thickness

50
Q

O2 dissolved in blood plasma

A

VO2 = 5000ml/min x .3mL O2/100mL = 15mLO2/min

Avg. 70kg human consumes 250mLO2/min at rest

51
Q

Hemoglobin O2 capacity

A

in RBC about 15g/100mL blood, 1.35mL O2/g Hb

Max O2 bound to Hb = Hb O2 capacity x Hb content

1.35mLO2/gHb x 15gHb/dL blood = ~20.3 mLO2/dL blood

52
Q

Hemoglobin saturation

A

%SO2 = (O2 bound to Hb / Hb O2 capacity) x100

%SO2 = 0% PO2 = 0mmHg

%SO2 = 25% PO2 = 15mmHg

%SO2 = 50% PO2 = 25 mmHg

%SO2 = 75% PO2 = 40mmHg

%SO2 = 100% PO2 = 100mmHg

%SO2 = 100% PO2 = 500mmHg (hyperoxia)

53
Q

Blood Flow

A

BF = HR x SV

54
Q

Positive allosteric effectors of HB (P50 reduced; left shift)

A 
↑ pH
↓ PCO2
↓ 2,3 BPG
↓ Temperature
↑ HbF
↑ CO
↑ MetHb
55
Q

Negative allosteric effectors of HB (P50 increased; right shift)

A 
↓ pH
↑ PCO2
↑ 2,3 BPG
↑ Temperature 
↑ Altitude
56
Q

Bohr effect (right shift)

A

At lung alveoli, O2 binding releases H+ due to high pO2, O2 binding to Hb releases H+

At tissue capillary beds, increased [H+], decreased pH, oxyHb acquires H+ which enhances release of O2 for aerobic metabolism

57
Q

CO2 transportation

A

gaseous and dissolved CO2 in plasma

Carbamino compounds: Hb-NH-COO- + CO2

Bicarbonate (HCO3-)
CO2 + H2O → H2CO3 → H+ + HCO3-

58
Q

Haldane effect

A

when O2 binds Hb, CO2 released

w/o Haldane CO2Δ = 52-50 = 2 volume %

w/ Haldane CO2Δ = 52-48 = 4 volume %

↑ %SO2 = right shift

↓ %SO2 = left shift

59
Q

Partial pressure of lung gases at 37°C (body temp)

A

100°C Wvp = 760mmHg
0°C = 5mmHg
PH2O = 47mmHg

air-lungs interface:
PTotal = 760 - 47 =713mmHg (reduces partial pressure of all gases at lung surface)

PN2 = 713 x .79 = 563.3
PO2 = 713 x .21 = 149.7
PCO2 = 713 x .0004 = .28
60
Q

Minute ventilation (Ve)

A

Ve = Vt x f

Vt: tidal volume (500mL/breath)
f: flow rate (15 breaths/min*)

500 x 15 = 7500 ml/min*

*for avg. 70kg male

61
Q

Alveolar Ventilation (Va)

A

Va = Vt - Vd x f

Vd: anatomic dead space (150mL for 150lb male)
Vt: 500mL
f: 15 breaths/min

Va = (500 - 150) x 15 = 5250 mL/min exchanged in alveoli

62
Q

Alveolar Ventilation (after surgery)

A

Vt: 200mL/breath
Vd: anatomic dead space (150mL for 150lb male)
f: 40 breaths/min
Ve: 8000mL/min

Va = (200 - 150) x 40 = 2000 mL/min

Normal: 5250mL/min

63
Q

Determinants of alveolar PA O2

A

PAO2 = 102 mmHg (normal steady state)

PAO2 = [O2] entering - [O2] leaving

O2 entering determined by: PIO2 and Va

PAO2 directly proportional to PIO2 and Va

64
Q

Alveolar gas equation (PO2)

A

PAO2 = PIO2 - (PACO2 / R)

R = respiratory gas quotient (VCO2/VO2)
If fuel is: 
Carbohydrate, R = 1
Fat, R = .7
Normal, R = .8
65
Q

Alveolar gas equation (PCO2)

A

PACO2 = VCO2 / Va

Normal: 40mmHg

PACO2 = [CO2] entering - [CO2] leaving

PACO2 inversely proportional to Va

66
Q

O2 content

A

(Hb g/dL x 1.34) x SaO2 +. (PaO2 x .003)

CP Fall19 Final (2 decks)

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