CHAPTER 3 Trauma 188 Expose and evaluate The patient should be appropriately exposed to facilitate a thorough ex amination. In particular, the neck and chest should be visualized. Once the assessment is c omplete, the patient should be covered up, especially in cold and damp conditions, to maint ain their core temperature. During this part of the examination, a quick visual inspection is made for other obvious musculoskeletal injuries. Reassessment If at anytime during the primary survey a patient deteriorates, it is importan t to return immediately to the beginning of the primary survey. In non- critical patients, a secondary survey may be appropriate. IF THE PATIENT DETERIORATES \200\223 ALWAYS GO BACK TO AIRWAY This page intentionally left blank CHAPTER 3 Trauma 190 Secondary survey The secondary survey is a head-to-toe examination undertaken in non- criti cal patients (for example, patients with minor injuries who may not require transportation to hospital) and is usually carried out in the ambulance. A comprehensive secondary survey is undertaken in the A&E department at a later stage. Assessment of the head Look for: - Lacerations - Bruising - Blood or CSF from the nose or e ars - Pupil size and reaction - Battle \200\231s sign and racoon eyes - Pallor - Cyanosis - Inspect the mouth for broken teeth, broken dentures, and debris. Feel for: - Scalp wounds - Scalp haematomas - Depressed skull fractures - Facial tenderness and fractures. Listen for: - Airway noise suggesting obstruction - Breathing rate and adequacy. Assessment of the neck The cervical collar should be removed and in-line manual stabilizati on maintained during examination of the neck. Look and feel for: - Tracheal position - Elevated jugular venous pressure - Laryngeal crepi tus (rare) - Surgical emphysema - Wounds - Swelling and tenderness - Midline cervical tende rness. Assessment of the chest Look for: - Wounds or penetrating injury - Chest wall deformity - S ymmetry of chest movements - Flail chest - Respiratory distress and pain with breathing. SECONDARY SURVEY1 191 Feel for: - Tenderness - Instability of a flail chest - Surgical emphysema - Percussion not e \200\224hyperesonance in pneumothorax or dullness with a haemothorax Feel the posterior chest wall for evidence of injury. Listen for: - Presence of equal breath sounds - Unilateral absence or reduction of breath s ounds due to a pneumothorax Unilateral reduction of breath sounds (usually posterior and basal) due to a haemothorax. Assessment of the abdomen Look for: - Abdominal wall contusion and penetrating wounds - Sea tbelt contusions and clothing imprints - Abdominal distension. Feel for: - Tenderness \200\224either generalized or localized - Guarding There is no value in assessing bowel signs in the pre-hospital environment. Assessment of the pelvis Look for: - Perineal wounds, swelling, and bruising - Blood at the urethral meatus. Feel for: Tenderness and instability from lateral and antero-posterior compres- sion. Only do this ONCE. Assessment of lower and upper extremities Look for: - Wounds and contusions - Deformity and swelling - Voluntary movements. Feel for: - Tenderness - Distal pulses - Sensation - Motor function - Joint movement. Injuries identified during the secondary survey may be treated immediately or, in some case s, left until after arrival in hospital. CHAPTER 3 Trauma 192 Head and neck injuries Mechanism of injury Blunt trauma is the most common mechanism of inj ury and follows inter- personal violence, falls, sports injuries, and road traffic collisio ns where, depending on the energy involved ( \200\230energy transfer \200\231), the injurie s produced range from simple scalp contusions and lacerations to non-survivable intracrania l injuries. Penetrating injuries include gunshot wounds, stab wounds with a knife or other sharp weapon , and, occasionally, impalement (for example, following falls from a height or industrial a ccidents). Pathophysiology of injury The brain consists of three main anatomical components. These are as and their principle functions are: - The cerebral hemispheres: Responsible for higher function including, sensory, motor, vision, and hearing. The cerebellum: Acts as a control center for balance and co-ordination. The brain stem: Contains vital control centers including the cardiac and respiratory centers. Following injury, the neurological deficit relates to the anatomical area of brain injury w hich may be further compromised by secondary complications (see below). Because there is no prospect of recovery of damaged nerve cells in the central nervous system, it is essential to provide optimal pre- hospital care in an attempt to minimize or prevent the subsequent mani- festation of secondary injury. The brain is surrounded by the meninges (dura mater, pia mater, and arachnoid mater) with p otential spaces within them for extradural and subdural haematoma formation. The brain is s uspended or floats in cerebrospinal fluid (CSF) which is found in the subarachnoid space an d functions as a shock absorber. The skull is a rigid box and, therefore, there is minimal space for brain expansion (for ex ample, due to cerebral oedema or haematoma formation) without producing an increase in intr acranial pressure (ICP). The skull base is tiered which makes the brain particularly vulnerable to twisting or decel eration injuries on the bony ridges. Parts of the skeleton are thinner, notably the cribrif orm plate and the middle ear, rendering these common sites of compound fractures with blood and CSF loss from the nose and ear respectively. Direct trauma produces both coup and contra-coup injuries including contusion, lacerations, oedema, and intracranial and intracerebral haematomas. Contra-coup injuries occur when the brain strikes the inside of the skull as a result of an impact elsewhere. HEAD AND NECK INJURIES1 193 Coup Contra coup Fig. 3.5 Coup and contra-coup injuries There are two principle types of brain injury: - Primary (direct) - Secondary (indirect). Primary (Direct) Brain Injury Secondary (Indirect) Hypoxia Hypovolaemia Cerebral odema Haematomas Hypoglycaemia Infection Primary brain injury relates to the mechanical events that occur at the moment of injury an d can only be influenced by accident prevention measures. Secondary injury relates to a com bination of factors which produce brain swelling. It is therefore essential that the immediate care practitioner addresses the issues of hypoxia, hypovolaemia, and hypoglycaemia. Cerebral perfusion must be maintained after a severe head injury where the cerebral perfusi on pressure (CPP) is related to the mean arterial pressure (MAP) (normally 80 \200\22390mmH g) and the mean intracra- nial pressure (MICP) (normally 5 \200\22310mmHg) by the equation: CPP = MAP \200\223 MICP It is desirable to maintain a cerebral perfusion pressure of between 70 \200\22380mmHg. Whi lst ICP is not measured in the pre-hospital environ- ment, cerebral perfusion pressure can be optimized by the correction of hypoxia and hypovolaemia (good ABC care). CHAPTER 3 Trauma 194 Patient assessment General assessment The initial assessment and management of the head-inj ured patient must begin with a search for life-threatening conditions. Particularly importa nt in head trauma, where the brain needs an adequate supply of oxygen, are: - A Adequate pr otected airway - B Uncompromised breathing - C Adequate cerebral perfusion. In patients suf fering head trauma, the cervical spine should be protected at all times. Specific assessmen t Neurological assessment during the primary survey follows ABC assessment and is limited t o pupillary equality and reaction to light and an AVPU assessment. - A Alert - V Response t o voice - P Response to pain - U Unresponsive. Patients responding only to pain or who are unresponsive are at risk of airway obstruction and usually have a Glasgow Coma Scale (GCS) of less than 8. A BM Stix \233\232 should always be undertaken to exclude hypoglycaemia as the cause of unconsciousness or as a contributing factor. A more detailed neurological examination is undertaken during the secondary survey which, i n many patients, occurs in hospital. The GCS provides a quantitative score by assessing eye opening, verbal response, and motor response. The painful stimulus should be applied above the neck to ensure that a cervical spine injury is not responsible for a lack of response. HEAD AND NECK INJURIES1 195 The Glasgow Coma Scale Eye opening Eyes are already open and blinking normally Eyes open in response to speech or specific questions Eyes open in response to pain No response E = 4 E = 3 E = 2 E = 1 Verbal response Fully orientated Confused conversation Inappropriate words Incomprehensible sounds No response to speech V = 5 V = 4 V = 3 V = 2 V = 1 Motor response Spontaneously moves limbs to command Localizes pain by purpose or motion tow ards the painful stimuli Withdraws or pulls away from painful stimuli Abnormal flexion, kno wn as decorticate posture Extensor response, known as decerebrate posture No movement M = 6 M = 5 M = 4 M = 3 M = 2 M = 1 Pupillary responses and limb responses to command in the conscious patient or painful stimu li in the unconscious patient are assessed to determine the presence of lateralizing signs or focal neurological deficit. Pressure over the supraorbital nerve is a useful painful sti mulus. During the secondary survey, the scalp is inspected. Simple abrasions and lacerations often need no specific treatment pre-hospital. Large scalp lacerations can bleed profusely and s hould be controlled by direct pressure. Should this prove ineffective, the edges of the wou nd can be inverted and direct pressure applied to secure haemostasis, or a number of large sutures can be inserted for temporary hemorrhage control. Hypotension should never be attri buted to scalp bleeding in an adult and alternative sites of blood loss should be sought. I n children, however, bleeding from large scalp wounds can produce clinical shock. Assessing the conscious level with the GCS provides a quantitative measurement, which acts as a baseline for further observations. A dete- riorating GCS may be the first indication o f neurological deterioration. When reporting the GCS, the scores for the individual compone nts should be given. The history of injury is important and, in the case of unconscious patients, onlookers may have important information regarding the mechanism of injury which should be passed onto th e staff of the emergency department. All patients with a history of unconsciousness should be transported to hospital, although the majority will have a transient loss of consciousness lasting a few seconds only. A meas ure of the degree of concussion is determined by the retrograde amnesia (last recollection before the accident) and the post traumatic amnesic period (first recollection after the ac cident). CHAPTER 3 Trauma 196 Helmet removal If there are a limited number of trained personnel available and the airway is clear, there is no urgency to remove the helmet. The only absolute and immediate indicat ion for helmet removal is an inability to open and maintain a clear airway. The removal of a motorcycle helmet should be a two-person technique and is undertaken as follows: - Undo the chin strap. - The first rescuer supports the neck from the front and progressively moves their hands up the back of the patient \200\231s neck during the procedure. The second rescuer, at the head of the patient, carefully expands the helmet laterally and tips the helmet forwards in a vertical plane, to clear the occiput, and then backwards, to clear the nose. Throughout the procedure, the rescuer controlling the neck ensures that they have firm control of the neck at all times. In an emergency, a lone rescuer may remove a motorcycle helmet as follows: - Kneel above th e patient \200\231s head. - Undo the chin strap. - Expand the helmet laterally. - Tilt the helmet forward until the occiput is clear. - Tilt the helmet backwards to release the chin from under the chin bar. - The rescuer maintains in-line immobilization by placing their ha nds either side of the patient \200\231s head and face and uses their forearms to complete removal of the helmet. HEAD AND NECK INJURIES1 197 Fig. 3.6 Helmet removal: two-person technique. Reprinted with permission from Greaves I et al. (2005). Emergency care: a textbook for paramedics, 2nd edn. W.B. Saunders Co. Ltd. Fig. 3.7 Helmet removal: one-person technique. Reprinted with permission from Greaves I et al. (2005). Emergency care: a textbook for paramedics, 2nd edn. W.B. Saunders Co. Ltd. CHAPTER 3 Trauma 198 Skull fractures The presence of a skull fracture is a reflection of the magnitude of force producing the head injury and, therefore, the degree of violence to which the underlying br ain has been subjected. This may be seen as an altera- tion in the level of consciousness. The risk of intracranial bleeding is significantly higher in patients with a skull fracture . Linear fractures These are common and are of particular relevance when they cross blood ves sels (for example, the middle meningeal artery in the parietal area), when they are often a ssociated with extradural haematoma. The fracture itself requires no specific treatment and is only diagnosed on X-ray in hospital. Compound fractures These occur in the cranial vault and are associated with overlying wound s which will require surgical debridement and, in the case of CSF leak, a neurosurgical opi nion. Many compound fractures are not obvious at the outset when only a simple laceration m ay be visible. The diagnosis may be made on X-ray. Where there is an obvious compound skull fracture, consideration should be given to direct transfer to a hospital with a neurosurgi cal facility, bearing in mind the patient \200\231s other injuries. A number of base skull fractures are also compound, as manifested by blood and CSF leak fro m the nose or ear. Antibiotics should only be given if there is a significant delay in the transfer to hospital. Basal skull fractures Weak points in the skull structure include the cribiform plate and th e petrous temporal bone and these are both sites of basal skull fractures, the common featu res of which are: - CSF leakage from the nose (rhinorrhoea) - CSF leakage from the ear (oto rrhoea) - Bleeding from the ears - Panda (raccoon) eyes (periorbital bruising) in anterior cranial fossa fractures Swelling and bruising over the mastoid process (Battle \200\231s sign). Panda eyes and Batt le \200\231s sign develop over a number of hours and are not usually seen at the outset. No specific treatment is necessary following blood and CSF loss in the pre-hospital environme nt. Depressed skull fractures Blunt weapons or strikes against protruding objects may fracture the skull pushing bone inwards. The dura is often torn and there is an associated underlyin g brain contusion or laceration. Treatment includes the application of a dressing and, if n ecessary, surrounding pressure to stop bleeding. In cases where there is a significant dela y to hospital, a broad spectrum antibiotic should be given. This page intentionally left blank CHAPTER 3 Trauma 200 Localized brain injury Localized brain injuries include: - Bruising or contusion - Intracra nial hemorrhage - Laceration and penetrating injury. Contusion Cerebral contusions result from direct injury and their size will depend on the m agnitude of the force involved. Most patients suffer a period of concussion. The diagnosis is made on a CT scan in hospital. Pre-hospital management follows the ABCDE regime. Intracranial hemorrhage Intracranial hemorrhage may be: - Extradural - Subdural - Intracere bral - Subarachnoid. Extradural haematoma This is an uncommon and sometimes rapidly fatal condition. Classically , it occurs due to a tear in the middle meningeal artery produced by an overlying parietal skull fracture. The patient recovers from an initial period of unconsciousness (concussion) but following a lucid interval lapses into unconsciousness as the intracranial pressure ri ses due to the enlarging haematoma in the extradural space. Complete recovery is possible w ith prompt surgical intervention. The classical features of raised intracranial pressure are: Decreasing level of consciousness - Increasing blood pressure - Falling pulse rate - Fallin g respiratory rate - Pupillary dilatation. Specific additional features may include weaknes s on the opposite side of the body to the head injury. The pupillary dilatation initially o ccurs on the same side as the injury but then becomes bilateral. The diagnosis is con- firm ed by CT scanning. Subdural haematoma These are more common than extradural haematomas and result from damage to blood vessels in the subdural space. Because they are due to venous bleeding, the haemat oma may collect more slowly. Acute subdural haematoma presents with the same features as ex tradural haematoma and should be treated by surgical intervention. The diagnosis is made in hospital by CT scan. Chronic subdural haematoma is an occasional cause of progressive conf usion in the elderly. Intracerebral haematoma Bleeding may occur within the cerebral hemispheres and may present with evidence of raised intracranial pressure. In contrast to extracerebral haematoma surge ry is not normally an option. LOCALIZED BRAIN INJURY1 201 Intracerebral hemorrhage Extradural haematoma Dura Subdural haematoma Fig. 3.8 Anatomy of intracranial bleeding. Reprinted with permission from Greaves I et al. (2005) Emergency care: a textbook for paramedics, 2nd edn. W.B. Saunders Co. Ltd. Subarachn oid hemorrhage Subarachnoid hemorrhage is a fairly common feature in severe brain injuries and is associated with a poor prognosis. The diagnosis is made on CT scanning. Serial neurological observations are essential in order to detect pro- gressive changes in the patient \200\231s neurological status, for example early deterioration in the level of consciousness following a lucid interval in a patient with an extradural haematoma. As much clinical history as possible should be given to the receiving staff in the emergency depar tment. Lacerations and penetrating head injuries Cerebral lacerations result from tearing o f brain tissue due to shearing forces and cause intracranial bleeding. Such injuries are as sociated with a high mortality rate. Intracerebral hemorrhage may also be caused by penetrating injuries. Causes include low vel ocity implements such as knives, industrial impalement, and road traffic accidents. The orb its and temporal regions are common sites of penetration since the bone in these areas is r elatively thin. Gunshot wounds to the head are becoming increasingly common in the UK and follow distinct p atterns, depending on the energy transfer. Both high- and low-energy transfer wounds lacera te and crush brain tissue. However, high-energy transfer wounds damage tissue extensively b y generating shock waves, temporary cavitation, and sucking contaminated debris into the wo und. Such injuries are almost invariably rapidly fatal. Injuries are also produced by bomb and grenade fragments. Treatment follows the normal ABCDE philosophy. Clean dressings should be applied to the entry and exit wounds. Generalized brain injury Diffuse axonal inj ury (DAI) results from major shearing injuries and commonly results in coma, which may last days, weeks, or be permanent. The diagnosis is made in hospital, based on clinical assessm ent and CT scanning. CHAPTER 3 Trauma 202 Neck injuries Blunt or penetrating injuries to the neck are associated with significant mor bidity or mortality. Vital structures at risk include the: - Trachea - Larynx - Jugular vei ns - Carotid artery - Esophagus The priority in management in the pre-hospital scene is to establish and maintain an open airway and control external blood loss. Cervical spine - Spinal cord and nerve roots - Thyroid gland - Thoracic duct. The neck should be examined for the following: Tracheal position - Neck vein distension - Laryngeal crepitus - Surgical emphysema - Wounds - Swelling - Posterior midline bony tenderness. Immobilization Any patient who has suffered major trauma or who has evidence of injuries ab ove the clavicle should be considered to be at risk of cervical spine injury and appropriat e measures must be taken to prevent any further damage. The cervical spine can only be cleared if: The patient is fully conscious - There is no history of alcohol or drug abuse - There are n o painful distracting injuries - There is no past history of significant neck injury - The patient does not suffer from rheumatoid arthritis or ankylosing spondylitis There is no midline posterior bony tenderness - There is no evidence of motor weakness or s ensory deficit. Patients at risk of cervical spine injury should receive inline manual stab ilization followed by the application of an appropriately sized semi- rigid collar. They sh ould be transported to hospital on a spinal board complete with head blocks and straps, unl ess the journey is likely to be prolonged, in which case transfer to a vacuum mattress is m ore appropriate. Penetrating neck injuries Many structures may be damaged. The priorities are an open airway and arrest of hemorrhage. The wound should be left undisturbed and if necessary direct pre ssure applied to arrest hemorrhage. Foreign bodies or embedded weapons should be left in si tu. Airway compromise due to bleeding may require, depending on clinical competencies, intu bation or a surgical airway. Some support to the neck and retention of dressings may be aff orded by the application of a cervical collar even in the absence of potential spine injury . NECK INJURIES1 203 (a) (b) Fig. 3.9 Sizing a cervical collar. Reprinted with permission from Greaves I and Porter K (1 997). Pre-hospital medicine \200\224the principles and practice of immediate care. Edward A rnold. Blunt trauma to the upper airway Injuries to the larynx may present with: - Hoarseness - St ridor - Tachypnoea - Surgical emphysema - Laryngeal crepitus. The patient should be left in the most comfortable position for breathing and oxygen therap y should be administered. In the event of clinical dete- rioration and airway compromise a surgical airway may be necessary. This may be made simpler by the presence of a hole in the larynx and access to the airway may simply require a skin incision. CHAPTER 3 Trauma 204 Faciomaxillary injuries Faciomaxillary injuries may occur in isolation or in association wi th other injuries. They may be immediately life-threatening due to airway obstruction or se vere hemorrhage. Anatomy The mandible is connected to the base of the skull by the narrow condyles at the te mporo-mandibular joint. The condyles are attached to the ramus of the mandible and, in turn , to the body which joins in the midline at the mental symphysis. The teeth are attached to the bone at the dentoalveolar margin. In a similar way, the maxilla supports the upper den tition and constitutes part of the orbital margin and lateral margin of the nose. The zygoma forms the outer margin of the cheek and orbital margin. The nose consists of a c artilaginous framework and a bony component that articulates with the frontal bone and the maxilla. Deep to the nose are the ethmoid sinuses and beneath the maxilla is the maxillary sinus. The facial skeleton has a rich blood supply from the facial artery, maxillary, artery, and ethmoidal artery which may account for potentially life- threatening hemorrhage following i njury. Mechanism of injury Blunt trauma from road traffic accidents, assaults, falls, and sports i njuries constitute the most common mechanisms of injury. Drink driving legisla- tion and se at belt laws have reduced the number of facial injuries due to road accidents. However, fac ial trauma due to interpersonal violence is increasing and is related to unemployment and a lcohol consumption. Penetrating trauma and burns are less frequent causes of facial trauma. FACIOMAXILLARY INJURIES1 205 Frontal bone Supraorbital ridge Nasal bone Infraorbital margin Zygoma Maxilla Mandible Fig. 3.10 Anatomy of the bony skeleton of the face. Reprinted with permission from Greaves I et al. (2005) Emergency care: a textbook for paramedics. 2nd edn. W.B. Saunders Co. Ltd. Immediate management In facial maxillary trauma, the airway may be compromised by: - Inhala tion of foreign bodies - Posterior impaction of a fractured maxilla - Loss of tongue contro l in a case of fractured mandible - Hemorrhage - Intra-oral swelling - Direct trauma to the larynx. In addition, hemorrhage can be severe and produce hypovolaemic shock. 2% of patien ts with facial injuries have cervical spine injury and manual stabilization, followed by a semi-rigid collar, head blocks, and tape should be used, with the patient positioned on a s pinal board. However, in the case of significant bleeding the supine position may result in airway obstruction. These patients may require manual spinal protection, whilst in the lat eral position, to permit postural drainage of blood. The patient with bilateral mandibular fractures may have no control over their tongue and will sit up and lean forwards to mainta in an open airway. Major bleeding may be controlled by the use of nasal Epistats \233\233, Foley catheters, or anterior or posterior nasal packing. In most cases, however, immediate transfer to hospital will be more appropriate. CHAPTER 3 Trauma 206 Soft and hard tissue injuries Facial injuries may be divided into soft tissue injuries, inc luding the eyes, and hard tissue injuries, including the teeth. Soft tissue injuries These include cuts and grazes, lacerations, and penetrating wounds. Bl eeding from the skin and oral mucosa can normally be controlled by direct pressure; profuse bleeding from the tongue can be controlled by pulling the tongue forward using a piece of gauze or alternatively by using a large suture and the application of traction. Foreign bodies should be left in situ unless they cause airway obstruction, in which case they should be removed and direct pressure applied. Injuries to the eye may result from blunt, penetrating, or chemical injury. Most serious ey e injuries require simple covering (without pressure) and transportation to hospital in the supine position. Penetrating foreign bodies should be left in situ. The eye exposed to che micals should be thoroughly irrigated with water. Hard tissue injuries, including teeth The mouth should always be inspected during the prima ry survey since broken teeth and broken dentures may be inhaled, especially in the unconsci ous patient. Avulsed teeth in children should be replaced and held until appropriate splint age can be applied in hospital. Should the child have an altered level of consciousness, th e tooth should be trans- ported to hospital in a container of milk. Mandibular fractures occur most commonly following assault. A blow to the right side of the jaw, for example, may produce a fracture of the angle of the jaw on the right side and a c ondylar neck fracture of the left side. The patient may complain of pain and swelling, diff iculty opening their mouth, and malocclusion. In addition, the patient \200\231s teeth may be fractured or displaced or missing. Treatment for this type of fracture is usually unnece ssary in the pre-hospital situation. The patient sustaining bilateral fractures of the body of the mandible may be unable to mai ntain an open airway as the tongue has lost structural support. This patient will not toler ate a supine position. A jaw thrust maneuver will not work and, if necessary, the tongue an d symphysis should be pulled forwards using a gloved hand. The patient may need positioning in the recovery position to facilitate postural drainage of blood and saliva. The patient is often found sitting forwards to allow natural drainage and should not be forced to lie s upine. Fractures of the maxilla commonly follow blunt trauma and can present as airway obstruction if the maxilla is impacted backwards. This can be relieved by hooking a gloved finger arou nd the soft pallet and pulling forwards. Fractures of the orbit and zygomatic complex are associated with periorbital bruising and s welling and, if displaced, the patient may complain of diplopia and infra-orbital nerve ane sthesia. Fractures of the nasal complex present with swelling and epistaxis which will usually respo nd to direct pressure. Midface fractures may be associated with significant hemorrhage whic h may require the use of nasal Epistats \233\233. FACIOMAXILLARY INJURIES1 207 Fig. 3.11 Nasal Epistats CHAPTER 3 Trauma 208 Chest injuries Injuries to the chest are responsible for up to a fourth of all trauma death s usually as a result of acute hypoxia or hypovolaemia. Mechanism of injury Blunt injuries Blunt trauma is the most common mechanism of chest injur y, the clinical consequences of which depend upon the amount of energy involved. These inju ries commonly follow road traffic collisions, falls, assaults, and sports injuries. The for ces involved are shear forces due to a change of speed (deceleration) and compressive force s. In a frontal impact road traffic collision, the driver may sustain a chest injury by dir ect contact with the steering wheel. At the time of impact, mobile organs continue to move forwards whereas fixed organs remain stationary. An example of this type of injury is teari ng at the junction of the arch of the aorta and the descending aorta. Compressive forces pr oduce damage to the underlying structures. For example, a lateral chest compression may pro duce chest wall contusion, rib fractures, a flail chest, and pulmonary contusion. Penetrating injuries The damage produced by a penetrating injury depends on the energy of t he weapon, the anatomical site, and the posture of the patient. Any wound between the umbil icus and the male nipple level equivalent may enter both the abdominal cavity and the plura l cavity. Penetrating wounds below the clavicle and above the costal margin, which lie within the mid -clavicular boundary, are likely to inflict critical mediastinal trauma. Blast injuries Primary blast injury results in alveolar hemorrhage and consolidation, pneum othorax, haemothorax, and air embolism. Penetrating injuries may also occur due to fragment s and displacement of the body. Anatomy and surface landmarks The trachea is a 2.5cm diameter tube made up of a number of i ncom- plete fibro-cartilagenous rings, which is lined by a mucous membrane. It begins at th e cricoid cartilage and ends at the carina where it bifurcates into the left and right main bronchi. The carina is at the level of the sternal angle (second rib). The trachea is a mi dline structure, the position of which can be checked in the suprasternal notch. The larynx can be palpated above the trachea. The right main bronchus is more vertical than the left and, therefore, aspirated foreign bo dies are more likely to enter the right side, although this will depend on the position of the patient at the time of the foreign body inhalation. The bronchial tree branches, becoming progressively smaller towards the periphery where it reaches the terminal bronchioles and alveoli. Gas exchange is by diffusion, facilitated by the close proximity of the alveoli and pulmonary capillaries. CHEST INJURIES1 209 Fig. 3.12 The danger area for thoracic and abdominal stab wounds. Any stab wound within the marked area may penetrate the pericardium. Reprinted with permission from Landon BA et al. , (1994). An Atlas of Trauma Management: The first hour. Taylor & Francis. CHAPTER 3 Trauma 210 The outer surface of the lung is covered by visceral pleura and the inner surface of the ch est is lined by the parietal pleura. These surfaces are closely applied by virtue of a nega tive pressure in the plural cavity. This is produced as a consequence of the tendency, by v irtue of tissue elasticity, for the lung and chest wall to pull in opposite directions. Dur ing the inspiratory phase of respiration, the diaphragm descends and the antero- posterior diameter of the chest increases, increasing the negative intra- thoracic pressure. In the p resence of an open airway, inspiration occurs. If there is an opening in the lung or chest wall, air will be sucked into the pleural space , producing a pneumothorax. In the presence of a flap-valve effect, this may become a tensi on pneumothorax, especially if the patient is receiving positive pressure ventilation or as sistance. During expiration, the diaphragm reaches the fifth intercostal space (equivalent to the mal e nipple level), although it can reach even higher if the patient is in a crouched position . The heart is positioned slightly to the left of the midline and is covered by the pericar dium. Stab wounds to the heart may result in bleeding into the space within the pericardium , producing cardiac tamponade. The heart, major blood vessels, trachea, and esophagus are p ositioned in the central part of the chest (mediastinum) and trauma to this region is often life threatening or rapidly fatal. Pathophysiology Normally, respiratory physiology relies on a concentration of oxygen flowin g into the alveoli (ventilation), where it is separated from blood flowing in the pulmonary capillaries (perfusion) by a thin membrane that facilitates oxygen (O2) and carbon dioxide (CO2) transfer (diffusion) between the alveoli and the capillaries. To maintain normality, the bal- ance between ventilation and perfusion is important. Impairment will lead to hypo xia and hypercarbia. Ventilation In a normal fit adult, 7 \200\2238ml/kg of air (approximately 500ml) is taken i nto the lungs with each breath. This amounts to approximately 5L per minute for a 70kg pati ent at rest. Only 70% (350ml) of each tidal volume reaches the terminal bronchioles where g as exchange occurs. The remaining 150ml remains in the upper airway and constitutes the ana tomical dead space. In addition, areas of ventilation without perfusion with blood constitu te the physiological dead space. In healthy adults, the anatomical and physiological dead s pace are approximately equal. Pulmonary perfusion There is a difference in blood flow between the apex and base of the lu ng because the pressure in the pulmonary circulation is much lower than the systemic circul ation. This results in under-perfusion of apical alveoli and over-perfusion of basal alveol i. At the bases, therefore, there is inadequate elimination of CO2 and uptake of oxygen. Th is blood is known as shunted blood. The effects of this are compensated by hypoxic pulmonar y vasoconstriction which diverts blood to better ventilated areas. CHEST INJURIES1 211 Diffusion The close proximity of the alveoli and pulmonary capillaries facilitates gas exch ange by passive diffusion due to a pressure gradient across the respiratory membrane. pO2 (alveoli) 100mmHg l pO2 (capillaries) 40mmHg pCO2 (pulmonary capillaries) 45mmHg l pCO2 (alveoli) 40mmHg The partial pressure is much smaller in relation to carbon dioxide exchange but this is not a problem because carbon dioxide is 20 times more soluble than oxygen. In the healthy adul t, exchange of both gasses takes place at the same rate. The lung has a pulmonary membrane surface equivalent to half a tennis court, making it ideal for gas exchange. Lung function may be compromised by poor ventilation (smoke inhalation, pain inhibition), reduced diffusi on (pneumothorax), or increased thickness of the respiratory membrane (pulmonary oedema). Patient assessment There are six immediate life-threatening conditions (ATOMIC) that should be detected in the primary survey. These are: - Airway obstruction - Tension pneumothorax - Open chest wound - Massive haemothorax - FlaIl chest - Cardiac tamponade. All patients wi th chest trauma require high-flow oxygen and this should be administered at 15L per minute after ascertaining that the airway is clear. A mask and non-rebreathable reservoir bag shou ld be used. Examination of the neck may reveal important physical signs suggestive of time- critical injury and must, therefore, take place before a collar is applied. The neck is exa mined for: - Tracheal position - Neck vein distension - Wounds - Surgical emphysema - Laryn geal crepitis - Spinal tenderness. Depending on clinical urgency, it may be more appropriat e to maintain inline cervical stabilization whilst completing the primary survey and to app ly a collar after it has been completed. Examination of the chest Where possible, the chest should be exposed, although this may be difficult in entrapments. A systematic examination should follow the sequence: - Inspection - Palpation - Percussion - Auscultation. CHAPTER 3 Trauma 212 DO NOT FORGET THE BACK The specific determents of the primary survey are summarized in Table 3.2. The back should always be checked for evidence of injury. In victims of assault, posterior stab wounds are relatively common. If it is impossible or untimely to turn the patient onto their side to i nspect their back, the gloved hand of the rescuer should be run down the back of the patien t \200\231s chest whilst in a supine position and then inspected for blood. Extreme care sh ould be used if there are fragments of broken glass about. Tension pneumothorax A tension pneumothorax may arise following blunt or penetrating trauma . Air is sucked into the plural space either through a hole in the chest wall or through a perforation in the visceral pleura, and a pneu- mothorax is produced. Should a flap be form ed, from pleura or other soft tissue, a one-way valve may result. This may allow air to pas s into the pleural space during inspiration but prevent it from leaving during expiration. The pneumothorax therefore increases in size, and the pressure inside the thorax rises. Thi s situation is worsened by coughing and positive pressure ventilation. Eventually, the pati ent becomes shocked because of impeded venous return and diminished cardiac output. The cla ssical features of a tension pneumothorax are: - Rapid respiratory rate - Decreased air ent ry - Hyper-resonant hemithorax - Rapid, weak pulse - Decreasing level of consciousness - De viated trachea (late sign) - Raised jugular venous pulse (if there is no accompanying hypov olaemia) - Cyanosis (very late). This condition can be rapidly fatal and the rescuer should have a high index of suspicion for the diagnosis. The treatment is a needle thoraco- cente sis using a 16 gauge cannula connected to a 10ml syringe. This is inserted into the second intercostal space in the midclavicular line. A rapid release of air confirms the diagnosis. The syringe and needle should be removed and the cannula left in situ and secured in posit ion. This cannula may become blocked or dislodged, particularly during patient transfer. If the patient deteriorates, reassessment using the primary survey is necessary. If it appear s that a tension pneumothorax is re-accumulating, a second cannula should be immediately in serted. Depending on clinical competence, the clinical situation, and the distance to a hospital, i t may (rarely) be necessary to consider a formal tube thoracocentesis. Thoracostomy with an Aschermann chest seal is an alternative. If needle thoracocentesis fails to demonstrate a tension pneumothorax, the needle should still be left in place. If it is likely that the needle may not have reached the pleural cavity and the possibility of tension pneumothorax is high, a second cannula can be inserted behind the pectoralis in the anterior axillary li ne high in the axilla. CHEST INJURIES1 213