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Gandaki Medical College
By: Gyaltsen Gurung
To define and classify ventilation and perfusion
in lungs.
To describe zone of perfusion in lungs
To describe ventilation perfusion ratio in lungs
To correlate VENTILATION and PERFUSION ratio with PULMONARY TUBERCULOSIS
OBJECTIVES
VENTILATIONThe rate at which air enters or leaves the lungs.
Types : i) Pulmonary Ventilation
ii) Alveolar Ventilation
1)Pulmonary Ventilation (minute ventilation or respiratory minute volume): Is the volume of air moving in and out of respiratory tract in a given unit of time during quiet breathing.
INTRODUCTION
Pulmonary Ventilation= Tidal volume X Respiratory Rate
= 500 ml x 12/minute
= 6000 ml/minute
2) Alveolar ventilation: It is the amount of air utilized for gaseous exchange every minute.
Alveolar ventilation
= (Tidal volume – Dead space) X Respiratory Rate
= ( 500 – 150 ) ml x 12/minute
= 4200ml/minute
TYPES OF VENTILATION.....
PERFUSION: The movement of blood into
the lungs through pulmonary capillaries.
VENTILATION/PERFUSION RATIO :
It is the ratio of alveolar ventilation and the amount of blood that perfuse the alveoli.
Mathematically, V/Q = 0.84
VENTILATION AND PERFUSION
ZONES OF LUNGS
Zone 1: No blood flow
Reason: More negative intrapleural pressure alveoli size↑ & lower arterial pressure due to gravity → decrease diameter of vessels
Zone 2: Intermittent blood flow
Reason: arterial pressure is greater than alveolar and venous pressure. Whereas, venules pressure are less than alveolar pressure venules are collapsed
Zone 3: Continuous blood flow
Reason: Due to gravity, there is high pressure → vasodilation → more blood flow
ZONE OF PERFUSION
Ventilation and Perfusion
(5ml/minute)
(0.56ml/minute)
(10.3ml/minute)
Zone 1: 1.92 L/minute
Reason: Increase size of alveoli
Zone 2: 4 L/minute
Reason: intermittent size of alveoli
Zone 3: 6.5 L/minute
Reason: Decrease size of alveoli
ZONE OF VENTILATION
It is the ratio of alveolar ventilation and the amount of blood that perfuse the alveoli.
Calculation:
V/Q= alveolar ventilation ÷ pulmonary blood flow
Alveolar ventilation= 4200ml/minute
Pulmonary blood flow=5000ml/minute
So, V/Q= 0.84
Ventilation/Perfusion (V/Q) Ratio
V/Q RATIO IN LUNGS
Zone 1: Ventilation(V) >>> Perfusion(Q)
V/Q= 3.4 (high)
Zone 2: Ventilation(V) = Perfusion(Q)
V/Q= 0.8 (average)
Zone 3: Perfusion(Q) >>> Ventilation(V)
V/Q=0.63(low)
V/Q IN DIFFERENT ZONES OF LUNGS
Apical Zone of lungs : It is more infected by
Pulmonary Tuberculosis
Reasons: i) There is low perfusion.
ii) There is higher V/Q , higher PO2 and lower PCO2
(M.tubercle is strict aerobes)
iii) Less of the oxygen is carried away by the blood in apex of lungs. ( Highest O2 available)
V/Q and PULMONARY TUBERCULOSIS
Zone 1: Ventilation(V) >>> Perfusion(Q)
V/Q= 3.4 (high)
Zone 2: Ventilation(V) = Perfusion(Q)
V/Q= 0.8 (average)
Zone 3: Perfusion(Q) >>> Ventilation(V)
V/Q=0.63(low)
Apex: It is more infected by Pulmonary Tuberculosis because
SUMMARY
Guyton and Hall ( 13th edition) Text Book of Medical
Physiology
K Sembulingam and Prema Sembulingam(6th
edition) Essentials of Medical Physiology
Ananthanarayan and Paniker’s( 9th edition)
Text Book of Microbiology
REFERENCES