General introduction

Breathing is the source of our life energy. Inspiration has a much wider meaning than just taking in air: it also means being creative, in a very deep, complex sense. Expiration not only means exhaling air; it is relaxation, letting go, finally also letting go of life. This link between life, death, and breath has been considered by many religions and philosophical systems. In the Bible we read that God made man from the dust of the earth and breathed into his nostrils the breath of life, and man became a living being. In those ancient Indian texts that are particularly relevant to yoga, such as the Vedas, Upaniads, Yoga-Sūtras, and Haha-Yoga-Pradīpikā, breathing is described as the essential process related to life.

Our life starts with our first inhalation and ends with our last exhalation. We can survive without taking fluids for about 4 days, without solid food for about 4 weeks, but without breathing for only 2–3 minutes. Breathing also connects our inner body with the environment. Philosophically speaking it connects the individual with the universe. It also connects physical and psychological aspects and is related to all bodily systems. Therefore we need to ensure that our breathing and all related structures and functions work as well as possible. As breathing is fundamental for life and all structures and functions of our body, we will give a short introduction to the anatomy and physiology of respiration, as a preparation for the practical parts of this chapter.

Basic anatomy and physiology of respiration

External and internal respiration

Respiration consists of two processes: external and internal respiration. External respiration consists of all processes involved in the intake of oxygen and the elimination of carbon dioxide through the lungs. Internal or cellular respiration is the absorption of oxygen, metabolic processes that produce energy, and the elimination of carbon dioxide through the body cells. This acts to regenerate the cells. External respiration also serves other functions, such as smelling and producing sounds such as speaking and singing, laughing, and coughing (Hauke 1980).

The passage of air

Air enters the system through first the nostrils, then the nasal cavity and the paranasal sinuses. After this comes the pharynx, which consists of three parts: (1) the upper pharynx, behind the nose and connected to the ears via the eustachian tube; (2) the middle pharynx, where food and respiratory pathways cross; and (3) the lower part, connecting to the larynx (Figure 5.1). The structures from the nostrils to the lower pharynx form the upper respiratory system, whereas the larynx is the beginning of the lower respiratory system. The epiglottis covers the larynx during swallowing, interrupting the passage of air. The larynx produces the voice and also the cough reflex to protect the lower structures – the trachea, bronchi, bronchioli, and alveoli of the lungs. The lungs contain about 300 million alveoli, surrounded by pulmonary capillaries (Figure 5.2). Oxygen and carbon dioxide are exchanged between the alveoli and the pulmonary capillaries by diffusion through the respiratory membrane.

Figure 5.1 The upper and lower respiratory system.

Figure 5.2 The alveoli.

The pleura covers the lungs and connects them to the thoracic wall. There are two layers in the pleura: the visceral and the parietal pleura. These layers cannot be separated, as they adhere together; however, they slide over each other. In this way the lungs passively follow the movement of the thorax.

Normally we inhale and exhale through the nose. The warm air of exhalation helps to dilate the blood vessels, improving blood supply. Air inhaled through the nose is moistened, warmed, cleaned, and examined through the sense of smell.

The muscles of respiration

The muscles of inspiration

The main muscles of inspiration are the diaphragm and the external intercostal muscles. Parts of the internal intercostal muscles are also involved (Netter 2006).

The diaphragm is a dome-shaped, musculotendinous structure, separating the thoracic from the abdominal cavity (Figure 5.3). It is attached to the upper three lumbar vertebral bodies via the crurae, which are tendinous pillars. It is also attached to psoas and quadratus lumborum muscles through the arcuate ligaments, the lower six ribs and their cartilages, and the xiphoid process of the sternum. Good diaphragmatic function assists other structures, and vice versa.

Figure 5.3 The diaphragm.

With inhalation the diaphragm contracts and its central tendon moves downwards a few centimeters. The vertical diameter of the thorax is increased. The lower ribs are elevated and therefore the diameter of the lower thorax also increases. The upper ribs are elevated and the anteroposterior diameter of the chest increases. The organs underneath the diaphragm influence the mobility of the diaphragm and the experience of respiration. The dome of the diaphragm above the liver on the right side is higher than above the stomach and spleen on the left side. The liver is more solid and less compressible than the stomach and the spleen. Mindful awareness of the breathing movement in the area of the diaphragm allows us to feel more resistance on the right side during inhalation. Due to the mobility of the liver this difference can be balanced with practice. During normal exhalation the diaphragm relaxes; the dome moves upwards a few centimeters, and the lungs go into passive rebound.

The accessory muscles of inspiration are the sternocleidomastoid, scalenus anterior, medius, and posterior (some fibers of which are attached to the fascia covering the top of the lungs), serratus anterior, pectoralis minor, and erector spinae.

In inspiration the air is drawn into the lungs through active expansion of the thoracic cavity. The diaphragm is contracted and moved downwards a few centimeters. This causes 75% of air intake in normal breathing. Raising the side ribs at the beginning of inhalation can enhance movement of the diaphragm. The intercostal muscles raise the ribs, resulting in the remaining 25% of the air intake. Combining both actions, normal breathing can become quite deep yet still be very subtle. The breathing techniques we explain later in this chapter are based on this. This subtle, conscious, deep breathing is different from forced breathing using the accessory muscles of respiration. These accessory muscles are not very active in normal, quiet respiration.

The muscles of expiration

Normal, quiet exhalation is passive. The diaphragm relaxes and moves a few centimeters towards the head. The costal cartilages and the ribs are depressed through the transversus thoracis muscle and the internal intercostal muscles. In this way the space is reduced and air moves out of the lungs. The activity of all the abdominal muscles and the latissimus dorsi muscle causes forced exhalation. As forced inhalation, this is not relevant to our approach to breathing techniques. These accessory muscles are rather used in a balanced, mindful way to improve and stabilize the sitting postures for the breathing techniques.

The thoracic cage

The thoracic vertebrae, the ribs, and the sternum form the thoracic cage, the skeleton of the chest (Figure 5.4). This protects the thoracic organs; the respiratory muscles are also attached to the thoracic cage.

Figure 5.4 The thoracic cage.

The ribs and their movements with inhalation and exhalation

There are 12 pairs of ribs. The upper seven ribs, the true ribs, are directly connected to the sternum by separate costal cartilages. The eighth to twelfth ribs are the false ribs. The costal cartilages of the eighth, ninth, and tenth ribs are fused, forming the costal arch and connected to the costal cartilage of the seventh rib. Ribs 11 and 12, the floating ribs, are connected just to the thoracic vertebrae, but not the sternum. All other ribs are also connected to the thoracic vertebrae. The costovertebral joints are between the head of the rib, the vertebral body, and the intervertebral disc. The costotransverse joint is between the costal tubercle and the tip of the transverse process. The many different joint planes throughout the different segments of the thoracic spine and the corresponding ribs lead to rib movements in different planes around different axes and therefore to a very complex movement pattern of the ribs during inhalation and exhalation. The three main movement directions can be summarized as follows: (1) elevation of the lower ribs increases the transverse diameter of the thorax; (2) elevation of the upper ribs increases the anteroposterior diameter of the thorax and raises it; (3) elevation of the middle ribs increases both diameters. Ribs 11 and 12 move like callipers to create more space in the lower thorax (Kapandji 2008).

Due to adhesion between the visceral and parietal pleura, this expansion of the thoracic cage leads to an expansion of the thoracic space that is filled by the lungs. Through this expansion the pressure in the thoracic cavity is decreased in relation to the abdominal cavity and the outside. This increases venous return to the right atrium of the heart. Therefore more blood is supplied to the lungs for gas exchange. More air is sucked into the lungs, to supply oxygen for gas exchange. In normal exhalation these movements are reversed passively; during forced exhalation they are enhanced using the accessory respiratory muscles. Due to the attachments of the serratus anterior muscles the shoulder blades are closely related to the ribs as well. Therefore good mobility of the shoulder blades is important for breathing.

The spine

The spine needs a good balance between stability and flexibility. Activating the abdominal muscles sufficiently during inhalation stabilizes the lumbar spine. Due to contraction of the pelvic floor muscles the sacrum moves into counternutation, which lengthens the spine.

The thoracic spine bends backwards slightly. B K S Iyengar (2009) gives an elegant description that the ninth thoracic vertebra and the sternum move slightly towards the chin. As a result the physiological curves of the spine become flatter (Hartman 2001). Good mobility of the costovertebral joints is important for breathing. Good mobility of this area also improves the blood supply and drainage of the sympathetic chain that is close to the costovertebral joints.

The sternum

During inhalation the sternum moves forwards and upwards. Anterior movement of the upper sternum is more than that of the lower sternum (Kapandji 2008). This also involves various movements of the costal cartilages, the sternocostal joints, and the costochondral junction and is important for rib movement. In connection with sternal mobility the transverse thoracic muscle is particularly relevant and should be stretched and mobilized.

The exchange of oxygen and carbon dioxide between the alveoli and the blood vessels

The alveoli are the terminal air saccules of the lungs. Fine pulmonary capillaries surround them. Both are lined by layers of extremely thin epithelium and separated by membranes. In the alveoli the concentration of oxygen is higher than in the capillaries. Therefore oxygen moves passively by diffusion into the capillaries. In contrast the concentration of carbon dioxide is higher in the capillaries and moves passively by diffusion into the alveoli. Air containing less oxygen and more carbon dioxide is removed by exhalation. The fresh oxygen diffused into the capillaries is carried into all tissues and organs of the body by red blood cells for absorption by the cells of the body.

In conclusion, a basic understanding of these processes shows how important a good pattern of respiration is for sufficient oxygen supply, to maintain the acid/alkaline balance, and to support the functioning of all systems of the body. Breathing is also important for the musculoskeletal system and its functions, including exercise. By the same token, practicing breathing techniques contributes to good lung function. The supply of the alveoli with air and the capillaries with blood can be significantly improved through good posture and practicing.

The rhythm and volume of respiration

There is a significant difference between the normal respiratory volume of 500 ml and the maximum capacity of respiration of up to 5 litres (Martini & Nath 2008). In quiet breathing the main respiratory muscles are used for inhalation; exhalation is passive, by elastic rebound. The emphasis can either be on the contraction of the diaphragm or on raising the ribs through contraction of the external intercostal muscles to increase thoracic volume so that air can be drawn into the lungs. Normally diaphragmatic breathing is deeper – 75% of total volume – whereas costal breathing is shallower – 25% of total volume. It can be further differentiated between high, clavicular breathing, intercostal mid breathing, and diaphragmatic breathing (Iyengar 2009). In full breathing in yoga all areas can be integrated. Capacity is greatest if the ribs are raised when the diaphragm is pulled down. In forced breathing the accessory muscles of inhalation and exhalation are used. In general, quiet deep breathing moves more air than forced, noisy breathing. The normal respiratory rate is 12–18 breaths per minute, slightly higher in children. It is directed by the breathing center in the medulla oblongata, influenced by the concentration of oxygen and carbon dioxide in the blood, the autonomous nervous system, and emotions. It is also adapted to movement (Hauke 1980).

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