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Physiology Conference
Leejoe Pallickal2/1/2013
ERV
RV
FRC
TV
IRV
IC VC
TLC
ERV Decreases RV
FRC Decreases
TV
IRV
ICIncreases
VC
TLCNormal
Obese
ERV Decreases RV
FRC Decreases
TV
IRV
ICIncreases
VC
TLCNormal
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ERV
RV
FRC
TV
IRV
IC VC
TLC
Closing Volume
FRC
DLVA
kCO =
DLVAkCO = slope (rate of uptake) =
DLVAkCO = slope (rate of uptake) =
The VA doesn’t correct the DL/VA it is derived from it! (based on the rate of uptake and the total uptake)
DLVAkCO = slope (rate of uptake) =
The VA doesn’t correct the DL/VA it is derived from it! (based on the rate of uptake and the total uptake)
VA = DLkCO (slope)
DLVAkCO = slope (rate of uptake) =
The VA doesn’t correct the DL/VA it is derived from it! (based on the rate of uptake and the total uptake)
VA = DLkCO (slope)
So what other factors affect kCO (DL/VA) besides VA?
1/DL = 1/DM + 1/θxVC
1/DL = 1/DM + 1/θ.VC
kCO =DLVA
Roughton and Forster equation:
DM = Alveolar membrane diffusing capacitya. Surface Areab. Membrane thicknessc. Pressure gradient PA-Ppl
θ= RBC membrane diffusing capacity (constant)
VC = capillary blood volume a. amount of hemoglobinb. Cardiac output through capillaries
1/kCO = VA/DM + VA/θxVC
J.M.B. Hughes 2003 Resp Physiology & Neurobiology -DLCOJ.M.B Hughes 2012 Am J Respir Crit Care Med -kCO
• 1. What patients have markedly elevated kCO (DL\VA) >120%?
J.M.B. Hughes 2003 Resp Physiology & Neurobiology -DLCOJ.M.B Hughes 2012 Am J Respir Crit Care Med -kCO
• 1. What patients have markedly elevated kCO (DL\VA) >120%?
Those where VC increases greater than VA decreases…
Pneumonectomy, Obesity, Neuromuscular
1 _ kCO
= VA_ DM
VA_θxVC
+
Why does VC increase?Because hemoglobin and cardiac output through the lungs stay the same despite decreased volumes. The same as why kCO (DL/VA) improves with exercise.
Diseases that ↑ θVc and thus ↑ DLco
• Reduced θVc• ‐ anemia• ‐ pulmonary emboli• • Reduced DM• ‐ Emphysema• ‐ Interstitial lung diseases (e.g.
IPF, sarcoidosis)• ‐ pulmonary edema• ‐ pulmonary vasculitis• ‐ pulmonary hypertension• ‐ lung resection
– Polycythemia– Left‐to‐right shunt– Pulmonary hemorrhage (not strictly an increase inθVc, but effectively an increase in lung Hb)– Asthma
