This document discusses lung volumes, aspects of ventilation, and regional differences in respiration. It explains how lung volumes like tidal volume, vital capacity, residual volume, and functional residual capacity are measured using a spirometer. Total ventilation is the product of tidal volume and breathing frequency. Alveolar ventilation accounts for ventilation lost to anatomic dead space. Regional ventilation differs depending on body position, with more ventilation occurring in lower lung zones when upright and more on the dependent side when lying laterally.

1. VENTILATION
PRESENTER: Keagan Kirugo
DISCUSSANTS:The Circle

5. OBJECTIVES
 Lung volumes
 Aspects of ventilation
 Regional differences in respiration

6. A. LUNG VOLUMES

7.  Lung volumes are measured by a spirometer.
 Using the original spirometer in the previous
slide for demonstration purposes; during
exhalation, the bell goes up and the pen goes
down marking a moving chart.

8.  Normal breathing is seen, the tidal volume.
 Next, the subject takes a maximum
inspiration followed by a maximum
expiration.The exhaled volume is the vital
capacity.
 However, some gas remains in the lung after
maximum expiration is the residual volume.
The volume of gas remaining in the lung after
a normal expiration is the functional residual
capacity (FRC)

10.  Spirometer is limited in the measurement of
residual volume, FRC andTLC.
 FRC can be measured by the Helium-dilution
method and plethysmography.

12.  The spirometer is filled with a small
concentration of helium (He). He is insoluble
thus cannot be absorbed by the blood.
 Valve is opened and the subject takes normal
breaths.The patient starts to breath at FRC.
 Breathing continues till there is equilibration
between the spirometer and the alveolar gas.

13.  Oxygen is added at this point to cater for the
O2 requirement of the subject. CO2 that is
exhaled is removed.
 FRC is thus obtained by
C1 xV1= C2 x (V1 + FRC)
 Plethysmography has replaced helium-
dilution method.

15. B. ASPECTS OF VENTILATION
 Total ventilation=Tidal volume x frequency
of breathing in a minute
 Thus change in tidal volume and frequency of
breathing will affect the total ventilation.
 Alveolar ventilation=Total ventilation –
(anatomic dead space x frequency of
breathing in one minute)

16. C. REGIONAL DIFFERENCES IN
VENTILATION
 Ventilation in lower zones > upper zones.
 This is demonstrated by inhalation of
radioactive xenon gas.The radiation emitted
is picked up by a radiation camera.
 The above is in upright posture. On supine
posture, the ventilation is relatively the same
at the different zones. On lateral posture, the
dependent side is greatly ventilated.