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Guyton Respiratory

Terms in this set (86)

Which muscles are used for quiet breathing?
diaphragm only
Which muscles does student use (contract) during expiration during exercise?
internal intercostals and abdominal recti - pull the rib cage down during expiration
Pleural pressure is -5 cm H2O during resting immediately before inspiration (i.e. FRC). What is pleural pressure during inspiration?
-7 cm H2O. Volume of chest cavity increases and pleural pressure becomes more negative. The pleural pressure returns to resting as the diaphragm relaxes and lung volume returns to FRC. Therefore, intrapleural pressure is always subatmospheric during quiet breathing.
Alveolar pressure is ~1 cm H2O during expiration. What is alveolar pressure during inspiration?
-1 cm H2O. Expansion of the chest cavity during inspiration causes the alveolar pressure to become subatmospheric, this creates +1 cm H2O pressure gradient for air to move into the lungs.
Man inspires 1000 mL from spirometer. IP pressure was -4 cm H2) before inspiration and -12 cm H2O at the end of expiration. What is compliance of the lungs?
125 ml/cm H20.
1000 ml/8 cm H2O = 125 (compliance = change in volume/change in pressure)
A liquid ventilated lung compared to a gas-ventilated lung
is more compliant.
There is lack of elastic forces due to surface tension, therefore compliance is decreased.
22 yoF has pulmonary compliance of 0.2 L/cm H2O and pleural pressure of -4 cm H2O. What is the pleural pressure when the woman inhales 1 L of air?
-9 cm H2O.
1 L increase in volume with cause 5 cm H2O decrease in pleural pressure (1 L/0.2 L = 5). So pressure is reduced by 5 cm H2O (-4 - 5 = -9 cm H2O).
Preterm infant has surfactant deficiency. What set of changes are present in the preterm infant compared to normal infant? (alveolar surface tension and pulmonary compliance)
alveolar surface tension is INCREASED.
pulmonary compliance is DECREASE.
surfactant reduces surface tension of water lining the alveoli, therefore surfactant reduces the work of breathing (less transpulmonary pressure is required to inhale). Bc compliance = change in lung volume for given change in transpulmonary pressure, pulmonary compliance is decreased in absence of surfactant.
Pt has dead space 150 ml, functional residual capacity 3 L, tidal volume 650 mL, expiratory reserve volume 1.5 L, total lung capacity 8 L, respiratory rate 15 breaths/min. What is residual volume?
1500 ml.
Residual volume = FRC - ERV = 3L - 1.5L = 1.5 L
What is expiratory reserve volume?
maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration. Equal to difference between FRC and RV.
What is functional residual capacity?
Equals the expiratory reserve volume plus the residual volume. Amount of air that remains in the lungs at the end of a normal expiration. Considered to be the resting volume of the lungs bc none of the resp muscles are contracted.
Which lung volumes CAN'T be measured using direct spirometry without additional methods?
total lung capacity, functional residual capacity, residual volume.
Which lung volumes CAN be measured using direct spirometry without additional methods?
vital capacity, inspiratory capacity, tidal volume, expiratory capacity, expiratory reserve volume inspiratory reserve volume
Pt has dead space of 150 ml, functional residual capacity 3L, tidal volume 650 ml, expiratory reserve volume 1.5 L, total lung capacity of 8 L, respiratory rate 15 breaths/min. What is the alveolar ventilation?
7.5 L/min.
Alveolar ventilation = frequency x (Vt - Vd) = 15 b/min x (650-150) = 7.5 L/min
At the end of inhalation, with an open glottis, the pleural pressure is
less than alveolar pressure.
pleural pressure during inhalation is ALWAYS less than alveolar or atmospheric.
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