Lung Volume (2)

Question 1

Tidal Volume (VT)

Answer 1

• Volume of air entering or leaving the nose/mouth PER BREATH
• Normal quiet breathing = 500mL/breath, but DRAMATICALLY INCREASE DURING EXCERCISE

Question 2

Residual volume (RV)

Answer 2

• Volume of gas LEFT in the lungs after a maximal forced expiration
• PREVENTS LUNGS FROM COLLAPSING at very low lung volumes
• *NOT MEASURED BY SPIROMETRY**
• Healthy = 1.5L
• HIGHER in a disease state such as EMPHYSEMA, in which inward alveolar elastic recoil is diminished

Question 3

Expiratory reserve volume (ERV)

Answer 3

• volume of gas that is expelled from lungs during MAXIMAL forced expiration that STARTS at the end of normal tidal expiration
• difference between Function residual capacity and the RV
• Healthy = 1.5L

Question 4

Inspiratory Reserve volume (IRV)

Answer 4

• volume of gas that is INHALED into the lungs during MAXIMAL forced inspiration STARTS at end of normal tidal inspiration
• FRC plus the VT
• Healthy = 2.5L

Question 5

Functional residual capacity (FRC)

Answer 5

• volume of gas remaining in lungs at end of normal tidal expiration
• balance point between inward elastic recoil of lungs and outward elastic recoil of chest wall
• RV plus ERV
• Normal = 3L

Question 6

Inspiratory capcity (IC

Answer 6

• Volume of air that is inhaled INTO lungs during MAXIMAL inspiratory effort that BEGINS at end of normal tidal expiration
• IC = VT plus IRV
• Noraml = 3L

Question 7

Total Lung capacity (TLC)

Answer 7

• Volume of air in the lungs after maximal inspiratory effort
• TLC consists of all four lung columes: RV, VT, IRV, and ERV
• normal = 6L

Question 8

Vital capacity (VC)

Answer 8

• Volume of air expelled from the lungs during maximal forced expiration starting after maximal forced inspiration
• VC = TLC - RV = VT + IRV + ERV
• normal = 4.5L

Question 9

What doesn’t the SPIROMETER Measure

Answer 9

RV, FRC, and TLC

Question 10

What Spirometric values would you expect to see in Obstructive lung disease

Answer 10

ASTHMA

• FVC decreased
• FEV1 DECREASED more than FVC
• Ratio FEV1/FVC is decreased

Question 11

What spirometric values would you expect to see in Restrictive lung disease

Answer 11

ALVEOLAR FIBROSIS = decreased lung compliance leading to compressed lung volumes

• FVC and FEV1 are decreased
• FEV1 is decerased LESS than FVC
• Ratio FEV1/FVC INCREASED

Question 12

What does FEV1/FVC ratio reflect

Answer 12

• fraction of total FVC that can be expelled during the first second; REFLECTS THE RESISTANCE TO AIRFLOW

Question 13

Define Anatomic dead space

Answer 13

• volume of the conducting airways
• does NOT include respiratory bronchioels and alveoli
• about 150mL

Question 14

Define Physiologic dead space (Vd)

Answer 14

• total volume of lungs taht DOES NOT participate in gas exchange
• INCLUDES anatomic dead space plus functional dead space in alveoli
  Vd = Anatomic DS + Functional DS

Question 15

Describe the clinical implications of functional dead space

Answer 15

• alveoli that DOES NOT participate in gas exchange due to ventilation/perfusion defect in which ventilated alveoli are NOT perfused by pulmonary capillary blood
• normal = about 150mL
• physiologic dead space increases due to ventilation/perfusion defect

Question 16

define minute ventilation

Answer 16

total rate of air movement into and out of lungs

Minute ventilation = Tidal volume (VT) x Respiration rate (RR)

Question 17

Define alveolar ventilation

Answer 17

- rate at which new air reaches the gas-exchange areas of lungs
Alveolar ventilation (Va) = RRx (VT - physiologic dead space (Vd))

Question 18

Define Alveolar ventilation equation

Answer 18

• INVERSE RELATIONSHIP BETWEEN ALVEOLAR VENTILATION AND ALVEOLAR Pco2
• If CO2 production is constant that alveolar Pco2 is determined by alveolar ventilation (VA)
  VA = (Rate of CO2)/(alveolar Pco2)

Question 19

If CO2 production doubles during strenuous excercise, what is the effect on alveolar Pco2 and VA?

Answer 19

The hyperbolic relationship between Alveolar Pco2 and VA shifts to the RIGHT
- the only way to maintain Alveolar Pco2 at its normal value, the VA will have to double also