Download - Mechanisms of Ventilation
Mechanisms of Ventilation
Learning Targets: Define the process of ventilation. (knowledge)
Determine how certain factors affect breathing rate. (reasoning)
Ventilation- movement of air into and out of lungs
1 2 3-4 Also refer to the next page Structures 3-4 Inhalation 5-9
Contraction of external intercostal muscles pulls ribs upward and
outward. Diaphragm contracts. Volume of thoracic cavity increases.
Pressure in pleural cavity decreases. Lungs inflate as air rushes
in. 5-9 Image Inhalation (a) Maximum Inhalation (b)
10-11 Expiration (Exhalation)
12-15 Muscles of inhalation relax due to elastic recoil. Volume of
thoracic cavity decreases. Pressure in pleural cavity increases.
Lungs deflate. Exhalation (a) Maximum Exhalation (b)
16 Exhalation (a) Maximum Exhalation (b) Please watch by clicking
on the illustration.
Summary animation for questions 5-16. Theres more to it Like a new
balloon, a new lung has a lot of elastic recoil. It is difficult to
inflate. The first breath for an infant is 20 times more difficult
than any breath after that. Also, elastic recoil can also cause a
balloon or alveoli to completely collapse.
Alveoli cannot completely collapse.It would take too much energy to
breath. So the body produces surfactant which decrease elastic
recoil. Premature babies may not produce surfactant and need to
have it administer artificially. Surfactant A phospholipid Reduces
elastic recoil
17-19 A phospholipid Reduces elastic recoil Prevents complete
deflation of our lungs Measuring Breathing Intensities
A respiratory therapist uses a peek flow meter to measure the
patients breathing intensities. Breathing intensities graph
Selected volumes, capacities and levels
Tidal Volume (TV) Volume of air inspired/expired during rest
breathing. Expiratory Reserve Volume (ERV) Volume of air that can
be forcefully exhaled, below tidal volume. Inspiratory Reserve
Volume (IRV) Volume of air that can be inhaled, above tidal volume.
Vital Capacity (VC) Volume of air that can be inhaled/exhaled (i.e.
VC=IRV +TV+ERV) Residual Volume (RV) Volume of air left after
maximal expiration. Measurable, but not easily so. Total Lung
Capacity (TLC) Volume of air enclosed in the respiratory system
(i.e. TLC=RV+ERV+TV+IRV) Resting End Expiratory Level (REL)
Location in lung volume space where tidal breathing typically ends
(35-40 % VC in upright position) Some typical adult values
Typical Volumes & Capacities Vital Capacity (VC) 4-5 liters
Total Lung Capacity (TLC) ~ one liter more than VC Resting Tidal
Volume (TV) ~ 10 % VC Resting expiratory end level (REL) ~ 35-40%
VC when upright Typical Rest Breathing Values Respiratory rate
12-15 breaths/minute Alveolar Pressure Palv +/- 2 cm H20 Airflow ~
200 ml/sec How does breathing affect speech?