Chest Trauma

Author: Nur-Ain Nadir, MD , Nathan Stuempfig, DO  Kaiser Permanente Central Valley 

Editor: Nicholas E. Kman, MD, OSU Wexner Medical Center Department of Emergency Medicine

Updated: November 2019


Case Study

A 21-year-old male presents to the ED by ambulance with complaints of chest pain and shortness of breath that began after he was involved in an altercation outside of a gas station.  The patient states that he was stabbed on the right side of his chest with an unknown object.  The patient states he feels as though he can’t breathe.  On exam, the patient is able to talk but has severely labored breathing.  There is a large puncture wound to the right, upper anterior chest.  His trachea is noted to be deviated toward the left.  


Objectives

Upon completion of this module, you should be able to: 

  1. Diagnose, resuscitate, stabilize and manage chest trauma patients.
  2. Identify common pathophysiologic conditions occurring in chest trauma patients.
  3. Describe the components of a primary survey in a chest trauma patient. 
  4. Generate a differential diagnosis of potential traumatic injuries based on history and physical exam. 
  5. List commonly utilized imaging modalities in chest trauma. 
  6. Discuss the eventual disposition of chest trauma patients based on their diagnosis. 
  7. Appreciate the necessity for emergent surgical intervention in certain chest trauma conditions. 

Introduction

The thoracic cavity contains three major anatomical systems: the airway, lungs, and the cardiovascular system. As such, any blunt or penetrating trauma can cause significant disruption to each of these systems that can quickly prove to be life threatening unless rapidly identified and treated. Chest trauma accounts for approximately 25% of mortality in trauma patients.1,2  This rate is much higher in patients with polytraumatic injuries. 85-90% of chest trauma patients can be rapidly stabilized and resuscitated by a handful of critical procedures.  Trauma patients are commonly encountered in all emergency departments, not just in specified trauma centers. For this reason, emergency medicine providers should be prepared to appropriately evaluate, resuscitate and stabilize any patient with chest trauma.

Unlike other disease entities, trauma patients often present with a known traumatic mechanism such as a car collision, fall, gunshot or stab wound. In rare cases, a patient may present in a state of significant altered mental status and be unable to provide any significant history.  In these situations, certain physical examination clues to the presence of trauma include findings such as contusions, lacerations, or deformities.  Palpation of crepitus over the chest wall may also be appreciated.  

In patients who are awake and lucid, the chest trauma may present with chest pain, dyspnea, back or abdominal pain, and occasionally syncope. Unstable chest trauma patients may show signs of severe respiratory distress or profound shock requiring emergent resuscitation. Unstable chest trauma patients can also deteriorate to the point of traumatic arrest and depending on the mechanism of chest trauma, may be candidates for an emergent ED thoracotomy.

Mechanism of Injury 

Thoracic trauma can be distinguished by the mechanism of injury. Blunt trauma refers to mechanisms causing increased intrathoracic pressure such as car collisions (most common cause of thoracic trauma), and falls. By comparison, penetrating trauma largely refers to gunshots, stab wounds, and occasionally impalement. There is considerable overlap amongst the various traumatic disorders experienced in both penetrating and blunt chest trauma. However, in comparison to penetrating trauma, blunt chest trauma patients may have a more subtle presentation with less obvious physical exam findings. 


Initial Actions and Primary Survey

Life-threatening injuries associated with thoracic injuries are often identified in the primary survey by carefully assessing the patient’s ABCDEs.

The injuries to be identified and treated in the thoracic region during the  primary survey  are: 

  • Airway obstruction 
  • Tension pneumothorax 
  • Open pneumothorax 
  • Flail chest and pulmonary contusion 
  • Massive hemothorax 
  • Cardiac tamponade 

Secondary Survey:  Potentially Life-threatening Chest Injuries

  • Tracheobronchial tree injury
  • Simple pneumothorax
  • Pulmonary contusion
  • Hemothorax
  • Blunt cardiac injury
  • Traumatic aortic disruption
  • Blunt esophageal rupture
  • Traumatic diaphragmatic injury

These injuries usually require immediate interventions such as intubation, needle decompression, tube thoracostomy, or pericardiocentesis.  These life-threatening injuries and related problems are resolved as they are discovered. Chest trauma patients can present to the ED via Emergency Medical Services (EMS), often placed on a backboard and in a cervical collar. Prehospital treatment of penetrating thoracic trauma patients can include needle decompression, 3-sided occlusive dressing, and IV resuscitation.  Patients can also walk into the ED, in which case it is prudent to immediately apply a C-Spine collar and proceed with Advanced Trauma Life Support Assessment.

All trauma patients must be managed in accordance with ATLS algorithms1: 

  • A  (Airway with c-spine protection): Is the patient speaking in full sentences? 
  • B  (Breathing and Ventilation): Is the breathing labored? Are symmetrical, breath sounds present bilaterally? 
  • C  (Circulation with hemorrhage control): Are pulses present and symmetric? How does the patient’s skin appear? (cold clammy, warm well-perfused) 
  • D  (Disability): What is their GCS scale? Are they moving all extremities? 
  • E  (Exposure/Environmental Control): Completely expose the patient. Is rectal tone present? Is there any gross blood per rectum? 

Initial Interventions:

  • IV – 2 large-bore (minimum 18 Gauge) Antecubital IV 
  • O2 – Nasal cannula, Face Mask 
  • Monitor: Place the patient on a cardiac monitor. 

It is important to note that if there is any deficiency noted during the primary survey, the problem must be addressed immediately, without proceeding until the patient has been stabilized.  If the patient’s primary survey is intact, the adjuncts to the primary survey and resuscitation begins.  The adjuncts to the primary survey include any of the following as necessary: EKG, ABG, chest X-ray, pelvis x-ray, urinary catheter, eFAST exam and/or DPL. 

Next, a secondary survey must be performed. The secondary survey is the complete history and physical examination.  This is completed after the primary survey and after any intervention performed as part of an abnormal primary survey. 

Start by taking an “AMPLE” history: 

  • Allergies
  • Medications
  • Past Medical History
  • Last Meal
  • Events regarding the trauma

Chest exam should detail entry and exit wounds, the total number of wounds, ecchymosis and deformities, paradoxical movement, or crepitus. Bedside sonography should be used to perform an eFAST exam, which assesses for the presence of pneumothorax, hemothorax, cardiac tamponade and intraperitoneal blood.

Details of the trauma mechanism are crucial.  For motor vehicle accidents (MVAs) speed of collision, position of colliding cars to each other, position of patient in the car, seatbelt use, extent of car damage (intrusion, windshield damage, difficulty of extrication, air bag deployment) are important elements to elicit. With respect to falls, the height of fall is important to know. When treating patients with gunshot wounds, the type of gun, distance from the shooter, and number of shots heard are all relevant. For stab wounds, it is prudent to obtain information on the kind of weapon used. 


Presentation

Chest trauma can lead to several serious and potentially life-threatening injuries. As a generality, chest trauma patients present with chest pain and shortness of breath but can also present in shock (altered mental status) or in traumatic arrest. Presenting vital signs tend to range from slightly abnormal to floridly unstable. Thoracic injuries are identified by primary survey signs: tachypnea, respiratory distress, hypoxia, tracheal deviation, breath sounds, percussion abnormalities, and chest wall deformities. 1 Chest trauma injuries can range from thoracic wall contusion or laceration, to pneumothorax (PTX), flail chest, and cardiac tamponade. Any injury within the “box” described as the region in between the nipple lines, inferior neck line and diaphragm often results in injury to underlying organs. 


Tension Pneumothorax (PTX) 

Tension PTX typically presents with shortness of breath and chest pain in the setting of trauma and in certain cases, may present as traumatic arrest. Air is forced into the pleural space without any means of escape, eventually completely collapsing the affected lung. The mediastinum is pushed to the opposite side, decreasing venous return and compressing the opposite lung. Shock results from the decrease in venous return causing a reduction in cardiac output and is classified as obstructive shock.

Clinical findings include absent breath sounds ipsilateral to the PTX, tracheal deviation opposite to the PTX, crepitus and jugular venous distension. Bedside ultrasound can be used to confirm the absence of lung sliding on the site of suspicion. If the diagnosis of tension PTX is suspected, patients should undergo prompt needle decompression followed by tube thoracostomy. Tension pneumothorax is a clinical diagnosis and there should be no delays in obtaining chest x-rays to make this diagnosis. 


Pneumothorax 

The presentation for this entity is typically less dramatic than tension pneumothorax. Patients present with chest pain and shortness of breath, tachycardia, tachypnea, and hypoxia. On physical exam they often have bilateral breath sounds, although typically asymmetric with decreased breath sounds noted on the side of the PTX. Chest X-ray (figure 1a) and bedside ultrasonography (figure 1b) are useful in making the diagnosis. 

Figure 1a. Simple traumatic left sided pneumothorax. Image courtesey of Dr. Nikos Karapasias Radiopedia https://radiopaedia.org/cases/traumatic-pneumothorax-1?lang=us  Used by Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported licence (http://creativecommons.org/licenses/by-nc-sa/3.0/) (CC Licence)

Figure 1b: Ultrasound image including M Mode demonstrating a pneumothorax. Image courtesy of Creagh Boulger MD, The Ohio State University Wexner Medical Center. 


Open Pneumothorax 

Open pneumothorax is a sucking chest wall wound from penetrating injury.  This is typically caused by a defect in the chest wall greater than 2/3 diameter of the trachea.  In this case, air moves preferentially through chest-wall defect resulting in ineffective ventilation & hypoxia.  Patients present with complaints of chest pain and shortness of breath.  The physical exam is significant for sonorous breath sounds, sucking air from the wound, and shallow respirations. It is treated by placement of an occlusive dressing with tape on three sides to create an escape valve. If application of a 3-sided dressing is not performed, this injury can turn into a tension PTX. The ultimate treatment is a tube thoracostomy placed ipsilateral to the side of the wound but at a different anatomic location. 


Hemothorax 

Patient complaints include shortness of breath or chest pain.  Occasionally, patients may be asymptomatic.  Typical exam findings are decreased breath sounds and dullness to percussion.  Although vital signs typically indicate tachycardia, tachypnea or hypoxia, they may also be normal. The diagnosis can be confirmed with a bedside ultrasound which can reliably reveal the presence of a hemothorax (figure 2). Although chest x-ray can be utilized, the sensitivity of an upright chest x-ray is superior to that of a portable chest x-ray. The typical treatment is placement of a 36-40 French chest tube. If the hemothorax is retained despite the chest tube, then a video assisted thoracoscopic surgery is recommended.

Indications for emergent surgery are: 

  1. Greater than 1500 ml of blood output at initial chest tube placement and 
  2. 2) output of greater than 200 ml/hour of blood for 2-4 hours. 

Figure 2: Shows a collection of blood above (to the left on the figure denoted by asterisks) the diaphragm on this Hepatorenal view ultrasound (courtesy of Creagh Boulger MD, The Ohio State University Wexner Medical Center).


Flail Chest 

A flail chest occurs when patients suffer three or more rib fractures in two places. This occurs when a segment of the chest wall lacks bony continuity with the rest of the thoracic cage and results in severe disruption of normal chest wall movement – inability to create negative pressure for ventilation. Pulmonary contusion is a frequent complication. Patients present with chest pain, dyspnea, painful respirations and are tachycardic, tachypneic and hypoxic. Clinical findings are pertinent for a visible or palpable deformity, bruising or crepitus, paradoxical movement and splinting with secondary hypoventilation. Chest x-ray can be used to make the diagnosis (figure 3). Early intubation is advocated in elderly patients, those with multiple rib fractures or if patients are in respiratory failure.  The treatment goal is to re-expand the lung with Continuous Positive Airway Pressure (CPAP) or physiotherapy, with the goal of preventing atelectasis. For patients with less severe injuries, pain control and incentive spirometry can be attempted. All patients need admission for observation. 

Figure 3. A patient with flail chest, subcutaneous emphysema and pulmonary contusions on the right chest x-ray Image by Dr. Ian Bickle Courtesy of Radiopedia https://radiopaedia.org/cases/flail-chest?lang=us Used by Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported licence (http://creativecommons.org/licenses/by-nc-sa/3.0/) (CC Licence)


Pulmonary Contusion 

Severe blunt chest trauma causes leakage of blood and proteins into alveoli causing atelectasis, which can lead to Acute Respiratory Distress Syndrome (ARDS) (figure 3). Patients with pulmonary contusions can present asymptomatically but often complain of shortness of breath, chest pain, cough or hemoptysis. On exam tachypnea, tachycardia, and hypoxia are common. In severe cases ecchymosis can be evident over the chest wall and decreased breath sounds may be heard. Although chest x-ray is typically performed, the initial chest x-ray may appear relatively normal, especially within the first 6-12 hours after the injury. Computed Tomography (CT) has a greater sensitivity and specificity for the diagnosis of pulmonary contusions. For large pulmonary contusions and significant respiratory distress, patients may need to be intubated. Smaller contusions can be managed with conservative management that includes incentive spirometry, pulmonary toilet, pain control and careful fluid administration. Clinical vigilance is needed in patients with pulmonary contusion as they can blossom over the initial 48 hours.


Cardiac Contusion 

This injury is closely associated with sternal fractures and most commonly affects the right atrium and ventricle after blunt trauma to the chest. Patients may present without any specific signs or symptoms, however most report some chest pain. Physical exam may be completely normal. Some patients can have chest wall contusions and those with sternal fractures will likely have obvious sternal pain. 40% of patients with cardiac contusions can develop signs of decreased cardiac output.  

Diagnosis requires a high clinical suspicion. EKG usually shows non-specific findings, though first-degree AV block, PVCs, and Right Bundle Branch Block can be seen. Patients with suspected cardiac contusions require formal echocardiograms (2D-ECHOs) for evaluation of Ejection Fraction (EF). They should be observed for at least 23 hours on telemetry as they are at risk of developing dysrhythmias and cardiogenic shock. If the 2D-ECHO shows a reduced EF (new from prior), patients should undergo a dobutamine stress test. Elderly individuals are at high risk for this entity, and it is important to note that frequently they may present to the ED 12-72 hours after injury with signs of cardiac compromise. 


Cardiac Tamponade 

Cardiac Tamponade from chest trauma is caused by a penetrating injury to the heart with subsequent tamponade. Patients present with chest pain, shortness of breath, and frequently with altered mental status. On exam Beck’s triad (hypotension, Jugular Venous Distention, and distant heart sounds) may be present. A more frequent presentation is that of hypotension, shock, pulsus paradoxus (greater than 10 mm Hg decrease in systolic pressure with inspiration), and narrowing of pulse pressure. The diagnosis is clinical however, it can be made with bedside ultrasound while performing the eFAST exam (figure 4).  Although EKG may demonstrate electrical alternans, this is not frequently seen in traumatic tamponade. Chest x-ray can show an enlarged cardiac silhouette. In hemodynamically stable patients, pericardiocentesis is indicated. As little as 15 - 20 mL removal may result in immediate hemodynamic improvement. Unstable patients need emergency surgical intervention in the Operating Room (OR). Patients may present in PEA and if they lose their vitals while in the ED, ED thoracotomy is indicated. 

Figure 4. Pericardial Tamponade on bedside eFAST exam.(Modified for emphasis) Red outline is denoting border of the heart with the asteriks denoting areas of pericardial tamponade. Images by Dr. David Carroll Radiopedia https://radiopaedia.org/cases/pericardial-effusion-with-tamponade?lang=us Used by Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported licence (http://creativecommons.org/licenses/by-nc-sa/3.0/) (CC Licence)


Blunt Aortic Injury 

Blunt Aortic Injuries, or traumatic aortic disruption, are usually seen in sudden deceleration type injuries secondary to abrupt deceleration from a motor vehicle accident > 30 mph or > 40 ft fall.  Most traumatic aortic injuries involve the proximal aorta.  Patients fall into three categories: A) dead on scene – presumed complete aortic transection on impact. B) hemodynamically unstable – full thickness transection with active hemorrhage from the aorta.  C) Hemodynamically stable patients – partial thickness transection with possibility of pseudoaneurysm of the aorta.  These are commonly seen at the ligamentum arteriosum. 

Patients may present with vague complaints including chest/back pain and lower extremity complaints but may also present with altered mental status and extremely unstable vital signs. Unstable patients can present with a left sided hemothorax as well. In stable patients, physical findings are nonspecific. However, it is important to look for chest wall contusions as well as pulse and blood pressure discrepancies in the extremities. 

Diagnosis is suggested if the mediastinum is widened on a chest x-ray. A CTA (spiral CT) is diagnostic. Angiography is considered the gold standard and only performed if the spiral CT is unequivocal. Transesophageal Echocardiography (TEE) can be used for unstable patients, though intubation is required prior to testing.  The treatment for hemodynamically unstable patients is emergent surgery to cross-clamp the aorta. For stable patients, aggressive BP control to a SBP< 120 mmHg followed by eventual surgical correction is advocated. 


Great Vessel Injury 

The great vessels include the aorta, vena cava and pulmonary trunk. Patients present unstable and hypotensive with minimal improvement in blood pressure after IV fluid challenge. Most patients present in frank hypovolemic shock. Physical findings suspicions for great vessel injuries include an expanding hematoma, acute superior vena cava syndrome, or a hematoma compressing the trachea. The diagnosis is primarily clinical. If the patient is stable enough for advanced imaging, a CTA or Angiography are helpful, however most patients are too unstable for imaging. Treatment consists of initial fluid resuscitation followed by transfusion of packed RBC. Emergent surgical repair of the injury in the OR setting is required.


Tracheobronchial Tree Injury

This occurs in only 1 to 2% of blunt trauma. It is commonly caused by rapid deceleration with injury occurring 80% of the time at carina, distal trachea or origin of main stem bronchi.  Esophageal injuries present in 25%.  The clinical presentation will show dyspnea, dysphonia, hoarseness, and subcutaneous air. In the ED, providers may see a persistent pneumothorax with air leak despite well placed chest tube. Patients may need bronchoscopy for diagnosis and may need to selectively intubate uninvolved lung. Operative repair is indicated for lacerations of the bronchi involving more than 1/3 of the circumference.


Traumatic Arrest Secondary to Penetrating Chest Trauma 

A traumatic arrest from penetrating chest injury can occur due to penetrating cardiac injury and great vessel injury leading to massive hemorrhage or cardiac tamponade, in addition to pneumothorax/hemothorax. In these situations, closed CPR is futile. Management requires stabilization of the airway via endotracheal intubation, bilateral chest tubes and ED thoracotomy which allows open heart CPR, pericardiotomy and cross clamping of the aorta. If a pulse is obtained after these interventions, patients need immediate surgical intervention in the OR.

Indications for an ED thoracotomy include:

  • Penetrating trauma AND
  • Patients who are hemodynamically unstable despite appropriate fluid resuscitation OR patients who have been pulseless despite CPR for < 15 minutes 

An important caveat is that a qualified surgeon must be present at the time of the patient’s arrival to determine the need for and potential success of an emergency department resuscitative thoracotomy (ATLS 9th Edition).  This procedure is not indicated for patients with blunt chest trauma given the dismally low survival rate.


Diagnostic Testing

  1. Chest x-ray: All chest trauma patients should receive a portable chest radiograph. However, the sensitivity of a chest radiograph is only 65% for detection of acute traumatic injuries such as pneumothorax/hemothorax.  Chest x-ray is easily performed at the bedside with minimal disruption to resuscitative care.
  2. Chest CT:  CT scanning has a much higher sensitivity than chest x-ray for detection of acute traumatic chest injuries however, obtaining a chest CT requires transportation out of the ED and obtaining images can delay care.  CT imaging may not be possible, especially in hemodynamically unstable patients.
  3. eFAST Ultrasound:  Recent studies8  have also established the utility of bedside ultrasound – specifically the eFAST exam, in the diagnosis and management of several acute chest injuries such as hemothorax, pneumothorax, and cardiac tamponade. 
  4. EKG: An EKG may be helpful in patients with blunt chest trauma or single vehicle MVA to help elucidate a cause of the accident. 
  5. Pulse Oximetry: This is helpful to assess adequacy of oxygenation and need for supplemental O2. 
  6. Laboratory Testing:  Blood testing, including ABG, does not have much utility in making the diagnosis of any of the conditions listed above. Generally, for all trauma patients a type and screen should be requested in the likely event blood transfusion is needed. CBC will help later with determining the amount of blood loss.  Patients with cardiac contusion will require serial troponins.

Treatment

The immediate goal of treating patients with chest trauma is to maintain or reestablish adequate oxygen perfusion to the end organ systems by providing ventilatory and hemodynamic support.  Each intervention is aimed at mitigating the specific disease process and is discussed in detail above.   

  1. Hemodynamically unstable patients: Intravenous crystalloid fluid and Packed Red Blood Cell (O-Neg) transfusion with likely need for emergent or surgical intervention. 
  2. Tension Pneumothorax:  Needle decompression thoracostomy followed by tube thoracostomy
  3. Pneumothorax: Tube thoracostomy. See video of chest tube placement at: https://www.youtube.com/watch?v=IdmMR8JxmFo
  4. Open Pneumothorax: Three-sided valve dressing and tube placement at site separate from injury 
  5. Hemothorax: Tube thoracostomy.  If greater than 1500 ml of blood obtained on initial chest tube placement or more than 150-200ml/hr x 4 hours, then surgical intervention is necessary 
  6. Flail Chest: Symptomatic support with intubation and ventilation as needed. Incentive spirometry and pulmonary therapy are necessary. In extreme cases patients may require cardiothoracic surgical intervention. 
  7. Pulmonary Contusion: Symptomatic support with high flow oxygen, incentive spirometry, pain control, and intubation if necessary. 
  8. Cardiac Contusion: Close monitoring for any significant changes in ejection fraction with EKGs, echocardiogram and cardiac markers.
  9. Cardiac Tamponade: Pericardiocentesis followed by OR thoracotomy. See video of procedure at:  https://www.youtube.com/watch?v=GcoAHYcngEw
  10. Blunt Aortic Injury: In stable patients, treatment is aimed at blood pressure control followed by close observation and delayed aortic repair. If a patient is unstable then large volume blood transfusion and stat emergency aortic repair by Cardiothoracic and Vascular surgery is needed. 
  11. Great Vessel Injury: In an unstable patient, large volume blood transfusion and emergency surgical intervention are required. 

Pearls and Pitfalls

  • Chest trauma patients can present with several conditions each of which can be acutely life threatening; a majority of these conditions can be clinically diagnosed and treated during the primary survey. 
  • Tension pneumothorax is a clinical diagnosis, chest x rays are not indicated for making this diagnosis. 
  • Bedside ultrasonography can be extremely useful for diagnosing acute traumatic chest conditions. 
  • Only hemodynamically stable patients should be sent for advanced imaging such as CT scan.
  • ED thoracotomies are reserved for patients presenting with traumatic arrest secondary to penetrating chest trauma only 

Case Study

The patient is noted to be in severe respiratory distress.  There is significant concern for a tension pneumothorax given the type and location of the injury.  Oxygen was delivered via a non-rebreather mask and a right-sided needle decompression was performed which offered temporary relief.  Following needle decompression, a 28 F chest tube was placed in the right mid-axillary line.  A subsequent chest x-ray revealed proper chest tube placement with a small, left-sided pneumothorax.  The patient was monitored for 3 days in the hospital and discharged home after chest tube removal.  


References

  1. ATLS: Advanced Trauma Life Support for Doctors (Student Course Manual). Ninth ed. American College of Surgeons; 2013. 
  2. Bernardin, B. & J.M. Troquet. (2012). Initial management and resuscitation of severe chest trauma. Emergency Medicine Clinics of North America 30, 377. 
  3. Dev, S P (10/11/2007). “Videos in clinical medicine. Chest-tube insertion”. The New England journal of medicine (0028-4793), 357 (15), p. e15. 
  4. Fitch, M T (03/22/2012). “Videos in clinical medicine. Emergency pericardiocentesis”. The New England journal of medicine (0028-4793), 366 (12), p. e17. 
  5. Karmy-Jones R, Namias N, Coimbra R, et al. Western Trauma Association critical decisions in trauma: penetrating chest trauma. J Trauma Acute Care Surg 2014; 77:994.
  6. Nadir, N. & Doty. Chest Trauma. Yakobi, R. et al. (ed). In “New York Handbook of Emergency Medicine”. (2011) 
  7. Nandipati, K.C., S. Allamaneni, R. Kakarla, A. Wong, N. Richards, J. Satterfield, J.W. Turner, et al. (2011). Extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: Experience at a community based level I trauma center. Injury 42, 511. 
  8. Turner, E. (05/2013) “eFAST extended focused assessment sonography in trauma” https://www.youtube.com/watch?v=Yg78aU93SZE