Queen’s Lung Function: Assessment and Evaluation

00:51~06:01 The lung’s diffusion function is relatively difficult to measure

• It is influenced by surrounding ventilation, blood flow, and even red blood cells

• It has a multilayer structure, with many variations

• Examples: Changes in lung diffusion function caused by different diseases

• Examples: Diseases that affect ventilation and blood flow when diffusion function is impaired

09:49~11:44 Are there any obvious special manifestations in patients with poor lung gas exchange (diffusion)?

• No! Therefore, special experiments are needed to measure

• PaO2 / FiO2 Ratio (P/F ratio)

• A-a gradient

• DLCO

11:45~16:26 KJ: PaO2 / FiO2 Ratio (P/F ratio)

• Interpretation of independent variables

• Normal range: 300~500mmHg

• Interpretation of intermediate values (200~300mmHg)

• What does it mean if it is below 200mmHg?

• Disadvantages

21:41~33:18 Interpretation of A-a gradient

• Normal values of A-a gradient are related to age

• Two methods to estimate normal values

• What should be the normal value for the Queen of England?

• Key point: How to analyze changes in A-a gradient clinically?

• A simple trick to analyze A-a gradient: “Put yourself in their shoes, put their lungs in their shoes”

33:19~40:03 [Radiation] Inhaling high concentrations of oxygen can cause an increase in A-a gradient ~

• From a mathematical perspective: constants, dependent variables, independent variables

• In actual clinical practice, the constant surprisingly becomes the independent variable!

• In 1967, clinical evidence was found that inhaling oxygen leads to an increase in A-a gradient

• Direct reason: The increase in PaO2 does not keep up with the increases in PAO2 and FiO2

• Further explanation: A hypothetical explanation to ponder

• Two analyses: one positive and one negative

40:04~41:10 Break, take a minute to rest

41:11~43:51 Is it good to use a “non-returning” gas to measure diffusion?

• Several different gases, with varying diffusion rates

• The most suitable representative for diffusion capacity: non-returning + a slower diffusion rate

• Chosen gas: CO

43:52~46:42 How is DLCO measured?

46:43~47:56 [You may also be interested in…] Can the human body produce CO?!

47:57~57:18 The decrease in DLCO (“lower CO”) has stronger clinical significance

• Key point: Clinical significance of decreased DLCO

• Can normal DLCO be a disease state?

• What could cause increased DLCO?

• Hypothesize why DLCO decreases in chronic bronchitis and emphysema but increases in asthma?

• Trick for answering questions: D (decreased) L (lower) CO

57:19~62:08 Comparing P/F ratio, A-a gradient, DLCO

• Measurement methods

• Patient requirements

• Meaningful change directions

• Interfering factors for results: ventilation? blood flow? red blood cells?

• Learn to flexibly apply P/F ratio, A-a gradient, and DLCO

62:09~62:33 Conclusion