Lung Volume (2) Flashcards
Tidal Volume (VT)
- Volume of air entering or leaving the nose/mouth PER BREATH
- Normal quiet breathing = 500mL/breath, but DRAMATICALLY INCREASE DURING EXCERCISE
Residual volume (RV)
- 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
Expiratory reserve volume (ERV)
- 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
Inspiratory Reserve volume (IRV)
- 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
Functional residual capacity (FRC)
- 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
Inspiratory capcity (IC
- 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
Total Lung capacity (TLC)
- Volume of air in the lungs after maximal inspiratory effort
- TLC consists of all four lung columes: RV, VT, IRV, and ERV
- normal = 6L
Vital capacity (VC)
- 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
What doesn’t the SPIROMETER Measure
RV, FRC, and TLC
What Spirometric values would you expect to see in Obstructive lung disease
ASTHMA
- FVC decreased
- FEV1 DECREASED more than FVC
- Ratio FEV1/FVC is decreased
What spirometric values would you expect to see in Restrictive lung disease
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
What does FEV1/FVC ratio reflect
- fraction of total FVC that can be expelled during the first second; REFLECTS THE RESISTANCE TO AIRFLOW
Define Anatomic dead space
- volume of the conducting airways
- does NOT include respiratory bronchioels and alveoli
- about 150mL
Define Physiologic dead space (Vd)
- 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
Describe the clinical implications of functional dead space
- 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
define minute ventilation
total rate of air movement into and out of lungs
Minute ventilation = Tidal volume (VT) x Respiration rate (RR)
Define alveolar ventilation
- rate at which new air reaches the gas-exchange areas of lungs Alveolar ventilation (Va) = RRx (VT - physiologic dead space (Vd))
Define Alveolar ventilation equation
- 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)
If CO2 production doubles during strenuous excercise, what is the effect on alveolar Pco2 and VA?
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
