biomechanics of respiration.pptx

biomechanics of respiration

1. BIOMECHANICS OF RESPIRATION

2. The process of ventilation depends on mobility of bony rib thorax and ability of muscles of ventilation to move thorax.

3. GENERAL STRUCTURE AND FUNCTION RIBCAGE :

4. Ribs increase in length from 1-7 Then gradually decrease in length from 8-12

5. ARTICULATIONS OF RIBCAGE Manibriosternal and Xiphisternal joints – synchondrosis Costovertebral joints - synovial joints ( rotation and gliding motions occour )

6. Costochondral joints – synchondrosis Chondrosternal joints - 1,6,7- synchondrosis 2 to 5 – synovial joints Interchondral joints – synovial joints.

7. KINEMATICS OF RIBS AND MANIBRIOSTERNUM Costovertebral and costotransverse joints are mechanically linked , with single axis of motion for elevation and depression passing through centers of both joints.

8. Axis of rotation Motion Action Upper ribs (2-7) Near frontal plane In sagittal plane Pump handle Lower ribs (8-10) Near sagittal plane In frontal plane Bucket handle

9. MUSCLES ASSOCIATED WITH RIBCAGE

10. Diaphragm The diaphragm is the main muscle of inspiration. It is a musculotendinous sheet which separates the thorax from the abdomen. It is a large, dome-shaped muscle and is lower posteriorly than anteriorly. The right hemidiaphragm sits1–2 cm higher than the left hemidiaphragm due to the presence of the liver on the right. The superior surface of the diaphragm is covered with the parietal pleura. The pericardium which encloses the heart is attached to the central tendon of the diaphragm. The diaphragm has three openings to allow structures to pass between the thorax and the abdomen (oesophageal opening, aortic opening and vena caval opening)

11. The diaphragm is innervated by the phrenic nerve (remember that ‘C3, 4, 5 keep the diaphragm alive!’). The diaphragm has three sets of fibres: sternal, costal and lumbar. These fibres are all named according to their origin. All fibres converge into a central trefoil shaped (clover leaf) tendon. The sternal fibres of the diaphragm arise from the posterior surface of the xiphoid process. The fibres run upwards and medially to insert into the anterior border of the central tendon

12. The costal fibres make up the majority of muscle fibres of the diaphragm and arise from the inner surface of the lower six ribs and their costal cartilages. The fibres run upwards and medially to insert into the anterolateral part of the central tendon. The lumbar fibres arise in part from two crura. The right crus is larger and originates from the anterolateral aspects of the bodies and intervertebral discs of L1–L3. The left crus arises from the bodies and discs of L1 and L2. Both sets of crural fibres insert into the central tendon.

13. When contracting, the diaphragm descends and increases the vertical diameter of the thorax. During quiet breathing, the diaphragm descends just 1–2 cm (from the level of T8 to T9). However, in deep inspiration it can descend as much as 10 cm. Further descent of the diaphragm is prevented by compression of the abdominal organs. In this situation the central tendon now becomes the fixed point and further contraction of the diaphragm causes upward and outward movement of the ribs and forwards movement of the sternum.

14. The diaphragm is a highly aerobic and fatigue-resistant muscle compared with other skeletal muscles and more capable of long term rhythmic contraction.

15. DIAPHRAGM The costal fibres of diaphragm run vertically from their origin, in close apposition to rib cage , and then curve to become more horizontal before inserting into central tendon. The vertically travelling fibres which lie close to inner wall of lower rib cage form functional unit - “ ZONE OF APPOSITION ”

16. intercostal muscles The intercostal muscles pass between adjacent ribs. They span the intercostal space and there are 11 pairs between ribs 1 to 12. There are three layers of intercostals: external, internal and innermost. The intercostals are innervated by the intercostal nerves (T1–11)

17. The external intercostals are muscles of inspiration and form the outermost intercostal layer. They pass from the inferior border of the rib above to the superior border of the rib below. The fibres run diagonally in a downwards and forwards direction. Contraction of the external intercostals results in the rib below being pulled up towards the rib above, causing elevation of the rib cage (pump and bucket handle movement)

18. The interosseous part of the internal intercostals are muscles of expiration (the interchondral part of the internal intercostals are inspiratory muscles), and they form the middle intercostal layer. They pass from the inferior border of the rib above to the superior border of the rib below. The fibres run diagonally in a downwards and backwards direction, which is the opposite direction to the external intercostals. Contraction of the internal intercostals assists with forced expiration by drawing the ribs together and depressing the rib cage

19. The innermost intercostals form the deepest intercostal layer and run in the same direction as the internal intercostals. Their function is probably to stabilize the chest wall, preventing the intercostal spaces from ‘being sucked in’on inspiration and from ‘bulging out’ during expiration

20. INTERCOSTAL MUSCLES External intercostal muscle : raise lower rib upto higher rib ( inspiratory motion ) Internal intercostal muscles: lower the higher rib into lower rib (expiration motion ) The activation of intercostal muscles during ventilatory cycle is from cranial to caudal

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22. ACCESSORY MUSCLES OF RESPIRATION When thorax is stabilized , the accessory muscles of ventilation move vertebral column, arm ,head or pelvis on trunk. During times increased ventilator demand, the ribcage becomes mobile segment The accessory muscles therefore, increase diameter by moving ribcage upwards and downwards during inspiration ; and during expiration force diaphragm upward and thorax downward and inward.

23. Scalene Three pairs of scalene muscles (scalenus anterior, scalenus medius , and scalenus posterior) arise from the lower five or six cervical vertebrae and insert on the clavicle and first two ribs. They lift the upper chest when active. The scalene muscles are slightly active during resting inhalation and become more active with forceful inspiration, especially when ventilatory demands increase.

24. Scalene muscles Lifts first two ribs, and therefore sternum in pump handle motion of upper ribs. Also functions as stabilizers of ribcage , along with parasternals counteract paradoxical movement of upper chest

25. Sternocledomastoid Sternocleidomastoid muscles originate from the manubrium and clavicle and insert on the mastoid process of the temporal bone. Normally, this muscle flexes and rotates the head and is active during shoulder shrugging. When the head is held in an upright position by tensing the trapezius muscle of the upper back and neck, the sternocleidomastoid muscles can function to lift the upper chest. These muscles are active during forceful inspiration and become visible as thick bands on either side of the neck during the inspiratory phase in an individual who is in respiratory distress. This motion increases the anteroposterior diameter of the chest.

26. The major and minor pectoralis muscles are broad fan shaped muscles of the upper anterior chest. The pectoralis major originates on the humerus and inserts onto the clavicle and sternum. The pectoralis minor originates from the anterior region of the ribs 3 through 5 and inserts onto the scapula. They normally function to adduct the arms in a hugging motion. They are also capable of generating some anterior thoracic lift when the arms are braced on a surface in front of a subject. Individuals who have chronic shortness of breath often use these muscles by sitting in the “tripod” position

27. Trapezius The trapezius muscles are flat, triangular muscles located on the upper back and neck. Their action is to rotate the scapulae, lift the shoulders, and flex the head up and back. During forceful inspiration, they become more active by helping brace the head and allowing the sternocleidomastoid muscles to lift the thorax.

28. Accessory muscles Action SCM With trapezius stabilizing head, bilateral SCM pull ribcage superiorly( pump handle motion ). Muscle is recruited at the end of maximal inspiration. Pectoralis major Clavicular head Elevate upper ribcage when shoulders and humerus is stabilized. humeral attachment – above level of clavicle – pulls manubrium and sternum outward ( inspiratory action ) humeral attachment – below level of clavicle – pulls manubrium and upper ribs downward ( expiratory action ) Pectoralis minor Elevate 3 rd ,4 th and 5 th rib ( inspiration ) Levatores costarum Assist in elevation of upper ribs

29. Accessory muscle of expiration The accessory muscles of exhalation become active during forceful breathing. Generally, these muscles compress the thoracic cavity and facilitate exhalation. The muscle fibers of the internal intercostal muscles run downward and less obliquely than the external intercostal muscle fibers . This orientation causes these muscles to pull the ribs together, which results in compression of the thoracic cavity. They are stimulated by branches of the intercostal nerves and are most active during forceful exhalation. They also become active toward the end of deep inhalation and antagonize the lifting effect of the external intercostal muscles, which effectively stabilizes rib motion during forceful exhalation.

30. Abdominals – Assist with forced expiration Pulls the ribs and costal cartilages caudally ( in motion of exhalation) Also by increasing abdominal pressure the diaphragm is forced upwards into thoracic cage. Two roles of abdominals during respiration Increased abdominal pressure while lowering diaphragm is counteracted by tension in abdominal musculature When diaphragm is pushed cranially there is passive stretch exerted on fibres of diaphragm( optimizing the length tension relationship of fibres )

31. When the abdominal wall muscles contract, they compress the abdominal cavity. This compression forces the diaphragm upward, compressing the thoracic cavity. The abdominal muscles include pairs of external oblique, internal oblique, transverse abdominis, and rectus abdominis muscles. Forceful contraction of the abdominal wall muscle group results in increasing intraabdominal pressure, forcing the diaphragm upward and compressing the thorax. Abdominal wall muscles are active during resting and forceful exhalation.

32. They become more active when the elastic recoil of the lung and thorax cannot provide the needed expiratory flow during forceful exhalation, such as coughing, sneezing, talking loudly, and playing wind-powered musical instruments. The most active muscle of the group during resting and forceful exhalation in most body positions is the transverse abdominis. The least active muscles are the rectus abdominis. The abdominal muscles also can contribute to inspiration by contracting at end-exhalation. This contraction reduces end-expiratory lung volume so the chest wall can recoil outward, assisting the next inspiratory effort. Elevating abdominal pressure increases both the length and the radius of curvature of the diaphragm . Both of these effects result in greater transdiaphragmatic pressure for a given contractile tension.

33. Transverse thoracics Recruited along with abdominals and pulls the ribcage caudally Primary muscles when expiration is active – talking , coughing and laughing.

34. PATHOMECHANICS OF RESPIRATION Changes in pulmonary system can affect the biomechanics of thorax. COPD :- there is damage to airways and destruction of alveolar walls which diminishes the elastic recoil property of the lung Thus exhalation becomes ineffective in removing the adequate amount of air from thorax Air trapping and hyperinflation

35. The resting position of thorax is balance between elastic recoil properties of lung pulling inwards and normal outward spring of the ribcage In COPD there is imbalance between these two forces that alters lung volumes and ventilatory capacities. As elasticity decreases there is more air within the lungs There is increase in A-P diameter of hyperinflated thorax ( barrel shaped ) along with flattening of diaphragm at rest.

36. Hyperinflation Shortening of fibres of diaphragm Angle of pull of flattened diaphragm becomes more horizontal Contraction will pull the lower rib cage inward which works against lung inflation

37. Majority of inspiration is performed by other inspiratory muscles Which are less efficient compared to diaphragm Barrel chest + elevated thorax shortening SCM ing efficiency. Parasternals and scalene muscles generate greater force as lung approaches its total lung capacity

38. With forceful contractions of functioning muscles of upper ribcage (with an ineffective diaphragm) Diaphragm and abdominal contents may pull upwards in thorax During exhalation abdomen is pushed down and out Paradoxical thoracoabdominal breathing pattern ( it increases work of breathing as well as energy cost of breathing.