Lungs are the organs for purification of blood. Purification means oxygenation of blood & removal of Carbon dioxide. The deoxygenated blood (PO2- 40 mm of Hg)(PCO2-45 mm of Hg ) is pumped by right ventricle to reach the lungs. The oxygenated blood (PO2-104 mm of Hg) (PCO2-40 mm of Hg) is brought back to left atrium, to be pumped by left ventricle to reach each & every cell of the body.
(To be precise the effective PO2 is 95 mm of Hg).
Alveoli are the functional units of lungs. They are terminal ends of bronchial airways, where gaseous exchange takes place. They are surrounded by rich network of capillaries which bring blood for this exchange. There are two factors that determine the PO2 and PCO2 in the alveoli. These two factors are
However in a normal person in the upright position, the normal capillary blood flow in upper part of lungs is significantly less in relation with alveolar ventilation. Therefore at the top of lung VA/Q is greater, as much as 2.5 times of normal value. Hence this space is called Physiological Dead Space in lungs. At other extreme, in lower part of lungs, there is significant poor ventilation in relation with blood flow. So here, the VA/Q is 0.6 times of ideal, which is called Physiological Shunt.
However during exercise, the blood flow to the upper part of lungs increases & air entry to lower parts.
Role of Yogic Postures & Bucket Handle breathing in improving VA/Q in upper & lower lobes of lungs.
All back bending postures where cervical & thoracic spine is in extension, upper part of chest is directed towards gravity. Due to gravitational pull the amount of alveolar capillary perfusion increases significantly. This reduces the dead space in upper parts of lungs, improving the outcome, optimizing the VA/Q ratio. Examples of these postures are many but the simple one which can be done by everyone is Setubandha Asan.We need to increase the duration to be in this posture. Second example is Viparitdandasan on bench. This bench gives support to whole spine; hence one can remain in this posture for 10-15 minutes with comfort. Names of other back bending postures are, Ushtrasan, Matsyasan, Chakrasan. However it is not advisable to increase duration of these asanas as they lead to excessive compression in lumbar spine.
Bucket Handle Breathing is the conscious breathing occurring in lower part of rib cage. Lower part of rib cage is the area of 8th,9th & 10th ribs. These ribs have wider diameter of circumference. In quiet involuntary inhalation, the central tendon of thoracic diaphragm contracts & moves down, increasing the thoracic cavity in vertical dimension. This reduces the abdominal cavity, leading to ballooning of abdominal wall. This is called abdominal breathing.
In Bucket Handle Breathing, the transverse dimension of lower part of rib cage is expanded. This does not occur involuntarily.This is to be learnt & practiced every day. The muscles responsible for this expansion are
Viparitdandasan on bench