PHYS: Ventilation and Lung Volumes Flashcards
What is the term for the volume of air moving into or out of the lungs in a given time?
ventilation
What is the equation for flow?
Flow= Change in Pressure/Resistance to Flow
What values cannot be measured by spirometry?
- Residual Volume
- Functional residual capacity
- Total Lung Capacity
What is TLC?
Total Lung Capacity = VC + RV
around 6 to 7 L
What is TV?
Tidal Volume= volume of a normal breath
around 500 mL
What is FRC?
Functional Residual Capacity= ERV + RV
(volume of air int he lungs after a normal expiration)
around 2.5 L
What are 2 ways to measure FRC?
Helium Dilution Body Plethysmograph (Boyle's Law Box)
What is FVC?
Forced Vital Capacity= TV + IRV + ERV
(volume of air exhaled during a forceful expiration)
around 5 L
What is IRV?
Inspiratory Reserve Volume is the additional amount that can enter during forced inspiration
around 3L
What is ERV?
Expiratory Reserve Volume is the difference between tidal end volume and forceful expiration end volume
around 1L
What is FEV1?
Forced expiratory volume in 1 second
What is a normal value for FEV1?
80% of the FVC
How can you use the FEV1/FVC ratio clinically?
To distinguish whether your patient has an obstructive or restrictive lung disease
What is the FEV1/FVC ratio for an obstructive lung disease?
Less than .7
both numbers are lowered, because it is difficult to expire through a narrowed airway, but FEV1 is lowered more!
What is the FEV1/FVC ratio for an restrictive lung disease?
.8 or higher
FVC is reduced due to reduced expansion causing problems getting air into the lungs
List 3 examples of an obstructive lung disease.
Asthma
Emphysema
Chronic Bronchitis
List 2 examples of a restrictive lung disease.
Obestiy
Pulmonary Fibrosis
What is the volume of the conducting airways not available for gas exchange? What is this called?
Anatomic dead space ~ 150 mL
What is the volume of alveolar space not available for gas exchange due to limitations in blood supply (e.g. embolis)?
Alveolar dead space= volume of non-perfused alveoli
What is the sum of anatomic dead space and alveolar dead space?
physiologic dead space
What is the equation for minute ventilation?
Vmv= TV X f
minute ventilation = tidal volume X respiratory rate
What is the difference between minute ventilation and alveolar ventilation?
Minute ventilation does not account for the fact that no gas exchange occurs in the dead space
What is the equation for alveolar ventilation?
Valv= (TV - Dead Space) X f
Why is their a greater ratio of exercise/rest for alveolar ventilation versus minute ventilation?
Dead space ventilation decreases as a percentage of minute volume
Which is more effective for alveolar ventilation: increasing depth of breath or increasing breathing rate?
Increasing the depth of breathing!
What is atmospheric pressure in mmHg?
760
What is the driving force for flow into and out of the lungs?
the pressure difference from the alveoli to the mouth
What is transpulmonary (transmural) pressure?
the difference between the alveolar pressure and the intrapleural pressure (outside the lungs)
How do we estimate the intrapleural pressure?
Inserting a balloon catheter into the esophagus for an estimate
List the muscles that aid in inspiration.
Diaphragm External intercostals accessory muscles (scalene, SCM)
List the muscles involved in expiration.
None normally (passive), but during exercise: Internal intercostals Abdominal muscles
When is the alveolar pressure most negative in the breathing cycle?
Mid-inspiration
When is the intrapleural pressure most negative in the breathing cycle?
End of inspiration
When is the alveolar pressure most positive in the breathing cycle?
Mid-expiration
When is the intrapleural pressure most positive in the breathing cycle?
End of expiration
How do you treat a pneumothorax?
intrapleural pressure equalizes with atmosphere, so you place a chest tube, hook it up to suction, and create a negative pressure
What is another word for the “stretchability” of the lung?
compliance
Compliance is the inverse of what value?
elastance
How do you calculate compliance from a pressure-volume curve?
it is the slope of the pressure volume curve, or:
change in volume/change in pressure
What word is used to describe the pressure-volume curve of the lung?
hysteresis
What causes the hysteresis seen in the pressure-volume curve of the lung?
surface tension
Decreased compliance is caused by diseases like what? What do they do to the lungs?
Restrictive diseases: fibrosis, edema
make the lungs stiffer where you cannot get air IN
Do people with decreased compliance have a higher or lower FRC?
lower
Increased compliance is caused by diseases like what? What do they do to the lungs?
Obstructive ventilatory defects: emphysema
Makes the lungs more stretchy and prone to collapse where you cannot get air OUT
Do people with increased compliance have a higher or lower FRC?
Higher (must breathe in larger volumes to fill lungs–barrel-shaped chests)
True or false: intrapleural pressure is always a negative value.
FALSE: forced expiration will change intrapleural pressure to a positive value which can be problematic (cause collapsed airways) for people with COPD or people with reduced elastic recoil (increased compliance)
A flow-volume loop of an obstructive ventilatory defect will show what?
inability to expire at a normal rate
A flow-volume loop of a restrictive ventilatory defect will show what?
reduced volume of air in lungs (can’t get as much in
What are the two major factors that determine lung compliance?
1) Tissue properties (1/3 is dependent on collagen, elastin, and interdependence)
2) Surface tension (molecular attractive force between lipid molecules
What is surfactant?
a mixture of phospholipids (ex. DPPC), cholesterol, and proteins produces by type II pneumocytes and stored in lamellar bodies
What stimulates surfactant production?
deep breaths
What is the major role of surfactant?
Increases lung compliance
Reduces the work needed to expand lungs
Reduces the tendency for pulmonary edema
In neonatal RDS, the lack of surfactant does what to the lung compliance?
decreases compliance
Which has a greater pressure, a large or small alveoli?
small (decreased radius, increased pressure)
What is the most important factor in resistance of airflow through the lungs?
radius of airway!
List the 4 factors affecting airway resistance.
1) Lateral traction (elastic tissue holding airway open from outside)
2) Lung volume (means increased airway diameter)
3) Relaxation/contraction of bronchial smooth muscle
4) Density and viscosity of inhaled gas
