cvpr first Respiratory physiology Flashcards
Lung volumes vs capacities
A capacity is a sum of ≥ 2 physiologic volumes
What is inspiratory reserve volume
Air that can still be breathed in after normal inspiration
What is tidal volume?
Air that moves into lung with each quiet inspiration
Average tidal volume
≈ 500 mL
What is expiratory reserve volume
Air that can still be breathed out after normal expiration
What is residual volume
Air in lung at the end of maximal expiration RV and any lung capacity that includes RV cannot be measured by spirometry
What is inspiratory capacity
IRV + TV Air that can be breathed in after normal exhalation
What is functional residual capacity
Volume of gas in lungs after normal expiration
What is vital capacity
TV + IRV + ERV Maximum volume of gas that can be expired after a maximal inpiration
What is total lung capacity?
IRV + TV + ERV + RV Volume of gas present in lungs after maximal inspiration
Lung capacities figure
646
Equation to determination of physiologic dead space
VD = VT x (PaCO2 - PECO2) / (PaCO2)
What is VD?
Physiologic dead space = anatomic dead space (dead space of conducting airways) + alveolar dead space (unventilated or unperfused dead space)
VT =
tidal volume
PaCO2 =
arterial PCO2
PECO2
Expired PCO2
Mnemonic of determining physiologic dead space
Taco, Paco, Peco, Paco Refers to the order of the variables in the equation
Physiologic dead space
approximately equivalent to anatomic dead space in normal lungs May be greater than anatomic dead space in lung diseases with V/Q effects
Describe minute ventilation
Total volume of gas entering lungs per minute VE = VT x RR
Describe alveolar ventilation
Volume of gas that reaches alveoli each minute VA = (VT-VD) x RR
Normal respiratory volumes
RR: 12-20 breaths/min VT = 500 mL/breath VD = 150 mL/breath
Describe elastic recoil
Tendency for lungs to collapse inward and chest wall to spring outward
Describe lung and chestwall forces at FRC
Inward pull of lung is balanced by outward pull of chest wall and atmospheric system pressure
Describe airway and alveolar forces at FRC
Airway and alveolar pressures equal atmospheric pressure (called zero) and intrapleural pressure is negative (prevents atelectasis) The inward pull of the lung is balanced by the outward pull of the chest wall System pressure is atmmospheric PVR is at a minimum
