Everyone who works in medicine of any kind understands that a patient’s airway and breathing are critical to their survival. If a patient does not have a patent airway or properly functioning respiratory tract, nothing else we do to resuscitate that patient will matter. This is the reason we always focus on A, B, C - airway, breathing, circulation and in that order. Our primary survey is in this order as well as our resuscitation efforts. Airway obstruction and blockage are the highest priority during a resuscitation event. Respiratory difficulties that are not directly related to an airway obstruction are next (think pleural effusion or pneumothorax). Life threatening cardiovascular emergencies are next and neurological resuscitation is last.
We often refer to respiratory distress as dyspnea, difficult, or labored breathing. The signs we typically see can be related to any number of abnormalities at any level of the respiratory system. I like to think of the respiratory system in three categories:
upper airway, the lung, and the pleural cavity. Difficulty breathing from airway obstruction can occur from the external nares, nasal passages, pharynx, larynx, trachea, bronchi, and down to small bronchioles. Many things can cause the airway to become obstructed: foreign body, vomit or hemorrhage, neoplasia, swelling or edema, trauma from fractures of the skull or larynx, hematoma formation and brachycephalic conformation.
Difficulty breathing can also occur due to the inability of the lungs to expand causing the lung to collapse. This makes it impossible for the lungs to move air into the alveoli and to allow gas exchange to occur. Damage to the CNS can affect the respiratory centers in the brain and affect control of the diaphragm. We see this in snake bites, tick paralysis, head trauma and neuro-muscular diseases. These diseases affect the brain and nerves ability to effectively tell the muscles of the chest wall to move and air movement into the lungs is compromised.
Damage to the chest wall is commonly seen in trauma and as a result of surgery; thoracotomy, rib fractures, intercostal muscle tears, punctures from bites or sharp objects and surgery to remove masses on the chest wall. All are causes to disrupt the chest wall causing severe pain, possible air in the pleural space or blood in the thoracic cavity. All of these can prevent the lungs from expanding when the animal inspires and can drastically affect gas exchange.
Pleural space disease is another reason the lung is unable to expand. The pleural space is a small space that exists between the outer surface of the lung and the inside surface of the chest wall. In healthy patients there is a small amount of fluid that acts as lubrication as the lung’s surface moves over the chest wall. This forms a cohesive contact that allows the lungs to fully expand on inspiration. When air or fluid gets into the pleural space, it prevents the lungs from having this cohesive contact with the thoracic wall and causes the lungs to collapse, severely affecting respiration.
Damage to the alveolus in the lungs, the gas exchange units, can occur due to aspiration of stomach contents/acid into the lungs or inflammatory, neoplastic, blood or fluid being present in the lungs. These situations can occur due to edema caused from congestive heart failure or blood getting into the alveolus from trauma. When the alveolus cannot get oxygen from the larger airways then gas exchange will be impaired. It becomes a domino effect: the alveolus can’t get oxygen , gas exchange can’t take place between the alveolus into the blood, the body senses it is not getting enough oxygen so it increases the respiratory rate and effort in an attempt to keep the vital organs oxygenated. This increased effort is why we see pronounced chest wall movement in heart disease with pulmonary edema and pneumonia. There are some cases where lung function is normal but blood flow to the lungs is impaired and oxygen can’t get into the circulation. Trauma to the vessels in the lungs and blood clots (pulmonary thromboembolism) are two common reasons for this presentation.
Patients that present in respiratory distress are often panicked, restless, tachypneic, pale or cyanotic, coughing, or open mouth breathing. They will often posture with their lips drawn back, neck and head extended, ribs showing, sometimes exhibit noise on inspiration and increased inspiration time (longer, deeper breaths.) These are signs commonly seen with a physical airway obstruction. This struggle with inspiration indicates serious disease since we will not see clinical signs in these animals until over 75% of their airway is compromised.
Patients can also present is expiratory dyspnea with the following signs: abdominal effort, extended expiration time, active expiration effort, rapid, shallow respiration and possibly an expiratory grunt. These signs may suggest pleural space disease or broncho-constriction and small airway disease as exemplified by asthmatic cats.
Patients that present with both inspiratory and expiratory dyspnea will present with a combination of the above signs. Inspiratory and expiratory effort is suggestive of disease involving lung tissue, the cardiovascular system, and blood disorders that affect the oxygen carrying capacity of the blood. Pleural space disease, pulmonary edema, CNS disease, aspiration or non-aspiration pneumonia, and hemoglobin deficits can also result in signs of both inspiratory and expiratory dyspnea. When a patient presents with cyanosis this is usually a late and unreliable sign of airway obstruction and hypoxia. Immediate action must be taken to secure a patent airway and restore ventilation.
When that respiratory distress patient arrives at your hospital it is helpful to have a “Respiratory Emergency Kit” or Crash Cart with the following in it and readily accessible:
- Endotracheal tubes 3.5 or 4.0, 6.0, 8.0 and a 10. (Usually these sizes will allow you to get a tube in to establish an airway immediately. You can always re-intubate later if need be for a perfect fit.)
- Laryngoscope with a good light source
- Red Rubber Urinary catheters x4 (18fr, 14fr, 12fr, 10fr)
- Tracheostomy tubes 3, 5, 8 and 10
- Lidocaine (to drip on the larynx to help prevent laryngospasm especially in cats) for intubation
- A small surgical kit containing:
- Hemostats-curved and straight
- Mayo scissors
- Rat tooth forceps
- Needle drivers
- Scalpel blades-10 or 15 and 11
- Sterile drape
- Sterile lap sponges and gauze
- Chest tubes: 8,10,14 and 16 fr (2 of each)
- Oxygen supply (wall or tank oxygen or anesthesia machine)
- Ambu-bags (learn how to use these and attach oxygen)
- Umbilical tape
- Pulse oximeter
- Butterfly needles 22G and 20G (5 of each)
- 3 way stopcocks
- Extension tubing
- 10 and 20 ml syringes (5 of each)
- Clippers and 18G needles x6
If you are in a position where a patient can not be intubated, there is always the last resort of a tracheostomy. Other procedures that might be tried first are inserting an 18G over the needle catheter (cats) or 14G over the needle catheter (dogs) between the tracheal rings (remove the stylet) or into the cricothyroid membrane at the caudal end of the laryngeal cartilages and connect to oxygen. This is a stop gap measure but provides some oxygen to the patient while you continue to establish a patent airway.
You can also use a red rubber urinary catheter as a stylet to help guide the ET tube into the trachea. Using a small chest tube (4-8fr) inserted between the tracheal rings into the trachea and connect to oxygen can also allow short-term oxygen delivery to the patient so the patient can be stabilized and preparations can be made for a tracheostomy.
Patients with accumulation of air or fluid within the pleural space will present with respiratory distress. An ultrasound of the thorax can assist in the diagnosis of pleural space disease, but if you don’t have an ultrasound machine, a diagnostic thoracocentesis can be performed. Decreased lung sounds can also suggest pleural space disease and indicate the need for thoracocentesis. Both sides of the chest should be drained when the thoracocentesis is done.
Pulse oximetry will help establish the effectiveness of breathing efforts. The pulse oximeter will measure the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. It gives us a rough idea of how effectively the lung is able to deliver oxygen to the blood.
The most important thing to remember with these patients is handling and sedation. These patients are very susceptible to dying during handling and minimal restraint is best. Avoid scruffing cats; use a towel for restraint if need be. These patients are hypoxic and hypoxemic and are very sensitive to anesthetics and sedatives requiring them to be used judiciously. Often times, fractions of normal doses are more appropriate for these patients.
Finally, when should you take radiographs? The rule of thumb is: nothing should die in radiology. It is tempting with these patients to immediately rush into radiology and shoot x-rays to see what is going on. Everyone has had that experience where you take an animal having difficulty breathing into x-ray and they struggle on the table, turn cyanotic or bite trying to get away and either die or come close to it just to get the radiograph. So is the stress of getting radiographs, (sometimes only one view which gives an incomplete diagnostic picture anyway) worth harming the patient? The answer is a resounding “NO”. Radiographs are an important tool when presented with respiratory disease. But timing is everything. So the question is “when is a good time to take radiographs?” The answer is when they are not in distress. It is extremely important to stabilize these patients first by providing supplemental oxygen either with flow-by, oxygen kennel or nasal prongs (whichever is less stressful and most effective), secure the airway, assess the pleural space and drain it if necessary and provide ventilator assistance if needed. When you do take radiographs plan on taking three views: right and left lateral and DV or VD if tolerated. If the patient becomes distressed during the taking of radiographs, stop and get them stabilized again. You may have to do the radiographs in stages.
These patients can be some of the most critical patients that we deal with. They need to be monitored every few minutes while they are being stabilized and then every 15-30 minutes, once they are stable. Remember, these patients can change status rapidly from stable to unstable in a matter of minutes. These animals are often very sick or trauma patients and are surviving on their own reserves only-and these reserves are limited. Handle with care, decrease stress and stabilize.