Enabling Objectives
  1. Revise the definition of bruises and describe the superficial structures of the chest wall.
  2. Describe the bones, joints and muscles of the chest wall, including the diaphragm.
  3. Describe the mechanism of breathing movements and indicate the effect of rib fractures.
  4. Identify the normal rate of breathing, explain the use of high flow oxygen and revise the usage of a pulse oximeter.




1. Describe rapid assessment, what is needed?

Reassessment is very important as the patients condition either improves, deteriorates or stays unchanged and the ABCDE needs to be carried out again. Assessment of the severity of the injury needs to be carried out, and all the injuries should be asseses, e.g. in blunt trauma. Analgesic should be given in the case of major trauma (entonox) 50% of nitrous oxide and 50% oxygen may be given until secondary survey. In addition morphine can be given intravenously the dose being titrated against the patients response.
What is the patients tetanus status and are antibiotics required. Are any further radiological investigations required? This depends on the condition of the patient, if hypoxia or haemodynamical unstability is present then these must be treated first. Once the condition stabilises, radiographs of particular sites of injury can be taken into account, so other specialised investigations can be carried out.
All changes need to be documented properly and should be accurate. The only way to achieve this is to have one dedicated person recording the data and the exact times of the problem. A radiograph should be taken from the chest if the patient had trauma and if possible the patients positions is partially erect or fully erect.

2. What is the normal anatomy of the thorax and physiology?

The thorax refers to the entire chest, whereas the skeletal part is called the thoracic cage. The different pats are the sternum, costal cartilage, ribs and the bodies of the thoracic vertebrae.
The thoracic cage is narrower at the top (superior) and broader at the bottom (inferior), however flattened from the front and the back, the thoracic cage encloses and protects the organs and provides support for the bones of the shoulder girdle and upper limbs.

Sternum:

The sternum or breastbone is the front flat bone located I the centre of the anterior thoracic cage, it measures about 15 cm in length and consists of three parts. The manubrium, the body and the xiphoid process are the three parts of the sternum, and they fused by the age of 25. The sternal angle is formed at the junction of the manubrium and the body, the manubrium has two different notches the suprasternal notch and the clavicular notch. The manubrium also articulates with the costal cartilage of the first and second cartilage, whereas the body of the sternum corresponds to the second to the tenth costal cartilage, the xiphoid process consists of hyaline cartilage which is important for attachment of abdominal muscles; however it does not ossify until the age of 40. The xiphoid process can be broken and driven into the internal organs during wrong CPR.

Ribs:
In total twelve pair of ribs give the structural support to the thoracic cavity. The ribs increase in length from the first till the seventh pair; the ribs have a direct anterior attachment to the sternum by hyaline cartilage. The function of the costal cartilage is to contribute elasticity of the thoracic cage and prevent various blows so fractures of ribs and sternum is prevented. The ribs that are connected to the sternum directly through cartilage are true vertebrosternal ribs. The articulation formed between the ribs and the sternum are called sternocostal joints. The remaining five ribs are false ribs because their costal cartilage either attaches indirectly to the sternum or do not attach to the sternum at all. The ribs 8-10 attach to each other through their cartilage and then to the cartilage of the seventh rib, they are called vertebronchondral ribs. The eleventh and twelth pairs of ribs are false ribs and do not connect to the sternum at all, and they are floating (vertebral) ribs as their costal cartilage is not long enough.
These ribs only attach themselves posteriorly to the thoracic vertebrae. Inflammation of one or more costal cartilage is called costochondritis.
The head of a rib is connected towards the corresponding vertebra, it can connect at the superior and inferior facet (depending which ones are present) these two connect to the demifacets of two vertebrae (this connection is called the vertebrocostal joint), as well as the articular part of the tubercle that connects to the transverse process of the vertebra. In addition the rib has a costal angel and a costal groove provides protection for blood vessels and small nerves. The costal cartilage connects the ribs to the sternum.
The neck part is the part after the head and it connects to the transverse process of the vertebra through the nonarticular part of the tubercle via a ligament. The articular part of the tubercle articulates with the facet of a transverse process of the inferor of the two vertebrae.
The spaces between the ribs are called the intercostal spaces and are occupied by intercostal muscles, blood vessels and nerves. Usually lungs and other structures can be accessed through the intercostal space as special rib retractors can be used for the space in between, as the cartilage are elastic enough in younger individuals.

3. What is the effect of fracture of (a) rib/s?

It is the most common chest injury and they result from high exerted force on the chest, and the break either occurs at the point of maximum force applied or the weakest point in the rib, the site of greatest curvature inside the costal angle.
The most common fractures occur are the middle ribs and they may cause puncture of the heart, lungs, great vessels, bronchi, trachea, oesophagus, spleen, liver and kidney. Usually they are quite painful, and bandages are not used as they can cause pneumonia, that results from lack of proper lung ventilation. Dislocated ribs involve displacement of a costal cartilage from the sternum, with resulting pain, especially during deep inhalations.
Seperated ribs involve displacement of a rib and its costal cartilage; as a result a rib may move superiorly overriding the rib above and causing severe pain.

4. What are the mechanisms of breathing?

As we have just seen, you move air into and out of the respiratory systems by changing the volume if the lungs. Those changes alter the pressure relationship and change move air. The changes of volume in the lungs occur through the contraction of skeletal muscles – specificially, those that insert on the rib cage. The thoracic and abdominopelvic cavities are separated by the diaphragm. Because of the nature of

Respirotary Muscles
The most important muscles ar e the diaphragm and the external, intercostal muscle. These muscles are active during normal breathing at rest. The accessory respiratory muscles become active when the depth and frequency of respiration must be increased markedly. These muscles include the internal intercostal, sterno0cleidomastoid, serratus anterior, dominis, external and internal oblique, and rectus abdominis muscles.

Muscles used for inhalation:

The following muscles are responsible for inhalation:

The diaphragm contracts and flattens the floor of the thoracic cavity, increasing its volume and drawing air into the lungs. Diaphragmatic contraction is responsible for roughly 75% of the air movement in normal breathing at rest.

Contraction of the external intercostal muscles assists in inhalation by elevating the ribs. This action contributes roughly 25% to the volume of air in the lungs in rest.

Contraction of the accessory muscles such as the sternocleidomastoid, serratus anterior, pectoralis minor, and scalene muscles, can assist the external intercostal muscles in elevating the ribs. These muscles increase the speed and amount of rib movement.

Muscles used in exhalation.
It can be active or passive, if it is active it may involve the following muscles.

Internal intercostal and transversus thoracis muscles depresses the ribs and reduces the witdh and depth of the thoracic cavity.
The abdominal muscles, including the external and internal oblique, transversus abdominis and the rectus abdominis muscles, can assists the internal intercostal muyscles in exhalation by compressing the abdomen and forcing the diaphragm upward.

Modes of Breathing.

The respiratory muscles are used in various combinations depending on the volume of air that must be moved into or out of the system. Respiratory movements are usually classified as quit breathing or forced breathing according to the pattern of muscle activity during a single respiratory cycle.

Quit Breathing: In quit breathing or eupnea, inhalation involves muscular contractions, but exhalation is a passive process. Inhalation usually involves the contraction of both the diaphragm and the external intercostals muscles. The relative contributions of these muscles can vary:

  • During diaphragmatic breathing or deep breathing contraction of the diaphragm provides the necessary change in thoracic volume. Air is drawn into the lungs as the diaphragm contracts and is exhaled passively when the diaphragm relaxes.
  • In costal breathing or shallow breathing the thoracic volume changen because the rib cage alters its shape. Inhalation occurs when contractions of the external intercostals muscles elevate the ribs and enlarge the thoracic cavity. Exhalation occurs passively when these muscles relax.

During quit breathing, expansion of the lungs stretches their elastic fibers. In additionm elevation of the rib cage stretches opposing skeletal muscles and elastic fibers in the connective tissues of the body wall. When the muscles of inhalation relax, these elastic components recoil, returning the diaphragm the rib cage, or both to their original positions. This phenomenon is called elastic rebound.
Diaphragmatic breathing typically occurs at minimal levels of activity. As increased volumes of air are required, inspiratory movements become larger and the contribution of rib movements increases. Even when you are at rest, costal breathing can predominate when abdominal pressure, fluids or masses restrict diaphragmatic movements. For example, pregnant woman increasingly rely on costal breathing as the enlarging uterus pushes the abdominal viscera against the diaphragm.
Forced Breathing Hyperpnea or forced breathing involves active inspiratory and expiratory movements. Forced Breathing calls on the accessory muscles to assist with inhalation and exhalation involves contraction of the internal intercostals muscles. At absolute maximums levels of forced breathing the abdominal muscles are involved in exhalalation. Their contraction compresses the abdominal contents, pushing them up against the diapgram and further reducing the volume of the thoracic cavity.


5. What is the normal breathing rate?
Normal breathing rate is between 9 breaths/min and 25 breaths/min.

6. What is a pulse Oximeter, what does it measure?

Pulse oximeter measures the pulse and oxygen saturation of the blood, inside the body through emitting light of the wavelength 660nm and 910nm and the absorption of the light can give the values for the oxygen saturation of the blood. The importance of this device is very crucial in emergency medicine as they give out results in few seconds. An indication of 100% saturation of the blood does not indicate a clear saturation as there could be high carbondioxide levels.

7. Why give high flow oxygen?

Delivers 95% oxygen.