Physiology 2130 Lecture Notes - Lecture 51: Lung Volumes, Tidal Volume, Breathing
1 May 2018
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Lecture 051: Ventilation Lungs Volumes Dead space
Spirometry
● Method to measure lung volumes
● Old
○ Movement of the bell with inhalation/exhalation
○ The bell is connected to a pen so you can calculated the volumes
● New
○ Digitalized
Lung volumes: Definitions
● Tidal Volume
○ The volume of air inhaled with each breath
● Minute Volume or Pulmonary Ventilation
○ The volume of air inhaled per minute
○ MV/PV = Tidal volume x Frequency of Respiration
● Vital Capacity
○ The volume of air that can be forcibly exhaled after a maximal inspiration
● Inspiratory Reserve Volume (IRV)
○ The volume of air that can be forcibly inhaled following a normal inspiration
● Expiratory Reserve Volume (ERV)
○ The volume of air that can be forcibly exhaled following a normal expiration
● Maximal Voluntary Ventilation (MVV)
○ The volume of air that can be moved into and out of the lungs in one minute by
voluntary effort
○ Also called maximal breathing capacity
○ Normal MVV is in the range of 125-170 L/min
● Residual Volume (RV)
○ The volume of air remaining in the lungs after a maximal expiration
● Functional Residual Capacity (FRC)
○ The volume of air remaining in the lungs after a normal expiration
● Total Lung Capacity (TLC)
○ The Volume of air in the lungs at the end of maximal inspiration
Forced Expiratory Volume - 1 second (REV - 1 sec)
● The fraction of Vital Capacity expired in one second
● Measure by:
○ Asking the person to inhale as much as they
can, then exhale as much and as fast as the
can
● REV - 1 sec is decreased in asthma
Spirometry limitation
find more resources at oneclass.com
find more resources at oneclass.com
● Not all of the volumes can be measured
○ TLC, RV, FCR all can not be measured by a spirometer alone
● Use the Helium Dilution method instead
Helium Dilution Method
● Low concentration of helium in the upside down bell
● Helium does not cross the blood gas barrier
○ Has a very high Fick’s Low constant so it cannot dissolve into the tissue
● Thus the helium that is inhaled stays within the system
● C1 x V1 = C2 x (V1 + V2)
○ C1: Initial [He]
○ V1: Volume of spirometer
○ C2: final [He]
○ V2: Volume of FRC
● Example:
○ C1 = 6%
○ V1 = 5 L
○ C2 = 4%
○ What is the FRC (V2)?
■ V2 = (C1 x V1)/C2 - V1
■ = 2.5 L
Dead Space
● Airway that do not participate in gas exchange
Recall: Pulmonary Volume is the volume of air inhaled per minute
● However, not all of the inhaled air reaches the alveoli (that participate in gas exchange)
Alveolar Ventilation
● Is pulmonary ventilation - dead space ventilation
● Example 1:
○ Tidal volume: 600 mL
○ Respiratory rate: 10 bpm
○ Thus pulmonary ventilation: 6 L/min
○ Anatomic Dead space: 150 mL
■ Only 450 mL of the 600 mL tidal volume is available for gas exchange
○ Thus alveolar ventilation is 4.5 L /min
● Example 2:
○ Tidal volume: 200 mL
○ Respiratory rate: 30 bpm
○ Thus pulmonary ventilation: 6 L/min
○ Anatomic Dead space: 150 mL
■ Only 50 mL of the 200 mL tidal volume is available for gas exchange
○ Thus alveolar ventilation is 1.5 L /min
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The bell is connected to a pen so you can calculated the volumes. The volume of air inhaled with each breath. The volume of air inhaled per minute. Mv/pv = tidal volume x frequency of respiration. The volume of air that can be forcibly exhaled after a maximal inspiration. The volume of air that can be forcibly inhaled following a normal inspiration. The volume of air that can be forcibly exhaled following a normal expiration. The volume of air that can be moved into and out of the lungs in one minute by voluntary effort. Normal mvv is in the range of 125-170 l/min. The volume of air remaining in the lungs after a maximal expiration. The volume of air remaining in the lungs after a normal expiration. The volume of air in the lungs at the end of maximal inspiration. Forced expiratory volume - 1 second (rev - 1 sec) The fraction of vital capacity expired in one second.
