Resp - Physio (Lung volume, Ventilation, & Lung and chest wall) Flashcards
Sections include: -Lung volumes -Determination of physiologic dead space -Ventilation -Lung and chest wall
What defines inspiratory reserve volume (IRV)?
Air that can still be breathed in after normal inspiration
What defines tidal volume (TV)? What is its typical value?
Air that moves into lung with each quiet inspiration, typically 500 mL
What defines expiratory reserve volume (ERV)?
Air that can still be breathed out after normal expiration
What defines residual volume (RV)? What is its clinical limitation?
Air in lung after maximal expiration; cannot be measured on spirometry
What lung volumes equal the inspiratory capacity (IC)?
IC = IRV + TV
What lung volumes equal the functional residual capacity (FRC)?
FRC = RV + ERV (volume in lungs after normal expiration)
What lung volumes equal the vital capacity (VC)? What defines the VC?
VC = TV + IRV + ERV; Maximum volume of gas that can be expired after a maximal inspiration
What lung volumes equal the total lung capacity (TLC)? What defines TLC?
TLC = IRV + TV + ERV + RV; Volume of gas present in lungs after a maximal inspiration
What is the equation for the physiologic dead space?
Vd = Vt x (PaCO2 - PeCO2)/PaCO2; Vd = physiologic dead space, Vt = tidal volume, PaCO2 = arterial PCO2, PeCO2 = expired air PCO2; Think: “Taco, PAco, PEco, PAco (refers to order of variables in equation)”
What does physiologic dead space include? What is another way to define this?
Anatomic dead space of conducting airways plus functional dead space in alveoli; Volume of inspired air that does not take part in gas exchange
What is the largest contributor of functional dead space?
Apex of healthy lung is largest contributor of functional dead space
What are the 2 types of ventilation?
(1) Minute ventilation (Ve) (2) Alveolar ventilation (Va)
What defines minute ventilation? What is its equation?
Total volume of gas entering the lungs per minute; Ve = Vt x respiratory rate (RR)
What defines alveolar ventilation? What is its equation?
Volume of gas per unit time that reaches the alveoli; Va = (Vt - Vd) x RR
What is the natural tendency of lungs versus chest wall?
Tendency for lungs to collapse inward and chest wall to spring outward
At what point does inward pull of lung balance the outward pull of chest wall? What is also the system pressure at this point?
At FRC, inward pull of lung is balanced by outward pull of chest, and system pressure is atmospheric
What determines the combined volume of the chest wall and lungs?
Elastic properties of both chest wall and lungs determine their combined volume
Describe the following measures at FRC: (1) airway pressure (2) alveolar pressure (3) intrapleural pressure (4) PVR?
At FRC, (1) airway and (2) alveolar pressures are 0, and (3) intrapleural pressure is negative (prevents pneumothorax). (4) PVR is at minimum.
What defines compliance?
Compliance - change in lung volume for a given change in pressure
What are 3 examples of conditions in which lung compliance is decreased?
Decreased in pulmonary fibrosis, pneumonia, and pulmonary edema
What are 2 examples of conditions in which lung compliance is increased?
Increased in emphysema and normal aging
Draw of graph of transorgan static pressure in cmH2O (x) and volume in L (y), graphing (1) chest wall (2) lung-chest wall system (3) lung.
See p. 597 in First Aid 2014 for graph at top right
