Look, Listen and Feel! Initial Evaluation of the Emergency Respiratory Patient
Christopher G. Byers, DVM, DACVECC, DACVIM (SAIM)
The initial approach to a patient with respiratory distress is of utmost importance as it can determine whether these critical patients will live or die. Classic clinical signs of respiratory distress are listed in Table 1.
Table 1. Classic Signs of Respiratory Distress.
Tachypnea
Head and neck extension
Opened mouth
Anxiety
Cyanosis
Nares flaring
Abducted elbows
Orthopnea
Paradoxical movement of the chest and/or abdomen
Signs of respiratory distress are more commonly seen in dogs compared to cats. Unfortunately, cats readily mask disease severity and commonly the only evidence of respiratory dysfunction is tachypnea and prominent respiratory motions in sternal recumbency.
The first step in examining a patient with a respiratory emergency is to perform a primary survey efficiently evaluating airway, breathing, and circulation (ABCs). If the airway is not patent, it must be cleared of obstruction and immediate intubation performed. If an upper airway obstruction prevents orotracheal intubation, an emergency tracheostomy must be done.
If intubation is deemed necessary, rapid induction with minimal cardiopulmonary depression should be accomplished. Common induction drugs are listed in Table 2.
Table 2. Common Induction Drugs in Respiratory Emergencies.
|
Drug(s)
|
Doses
|
|
Ketamine / Midazolam
|
5 mg/kg ketamine IV; 0.25 mg/kg midazolam IV
|
|
Midazolam / Fentanyl
|
0.25 mg/kg midazolam IV; 3–5 mcg/kg fentanyl IV
|
|
Etomidate
|
0.5–2.0 mg/kg IV
|
|
Propofol
|
3–8 mg/kg IV
|
|
Thiopental
|
5–10 mg/kg IV
|
If there are no airway patency issues (or once they have been addressed), a clinician should evaluate the patient's breathing pattern. The initial evaluation of a patient begins from afar, as the breathing pattern may change with patient manipulation. Making an accurate assessment, after handling, can be far more challenging.
Anatomical localization of the cause of respiratory distress is assessed through a "look, listen and feel" approach (Table 3). Supplemental oxygen should be provided while performing a primary survey (Table 4).
Table 3. Classic Anatomical Localizations.
|
Anatomic location
|
Most common causes
|
Useful distinguishing features
|
|
Upper airway disease
|
Foreign body, nasopharyngeal polyp, pharyngeal/laryngeal edema, mass, hemorrhage, laryngeal paralysis, tracheal collapse, brachycephalic airway syndrome
|
Stertor, stridor, noisy breathing, paradoxical abdominal movement, cyanosis, anxiety, exaggerated respiratory movements without breathing sounds
|
|
Chest wall disease
|
Flail chest, opened chest wound
|
Palpable thoracic body wall defect, paradoxical movement of flail segment
|
|
Pleural space disease
|
Pneumothorax, hemothorax, diaphragmatic hernia, chylothorax, pyothorax, right-sided heart failure, mediastinal disease, pleuritis
|
Rapid shallow respirations, muffled breath & heart sounds, paradoxical abdominal movement
|
|
Small airway disease
|
Chronic bronchitis, feline asthma
|
Prolonged expiration; expiratory "grunt"
|
|
Parenchymal disease
|
Pneumonia, pulmonary neoplasia, infiltrative disease, pulmonary contusions, cardiogenic pulmonary edema, non-cardiogenic pulmonary edema
|
Labored inspiration and expiration, harsh lung sounds, crackles, wheezes, dysrhythmias, murmur
|
Dr. Steven Haskins previously coined the term "look alikes" to describe non-respiratory causes of increased respiratory effort. These problems, that do not cause hypoxemia, include hypotension, pain, acidosis, behavioral disorders, anemia, and drugs. All may frequently be mistaken for indicating respiratory pathology.
Table 4. Methods of Provided Supplemental Oxygen.
|
Method
|
FiO2
|
Advantages
|
Disadvantages
|
|
Flow-by
|
25–45%
|
Inexpensive; simple
|
Requires high-flow rates (6–8 L/min; may upset stressed patient; requires an assistant to monitor patient
|
|
Face mask
|
35–95% depending on tightness of facemask
|
Inexpensive, convenient, easily administered
|
Some patients don't tolerate face mask; requires an assistant to monitor patient
|
|
Oxygen cage
|
40–90%
|
Allows animal to receive oxygen without manipulation
|
Expensive; requires large volume of oxygen to fill cage; oxygen level drops when cage door is opened; potential for patient over-heating
|
|
Intranasal
|
Unilateral: 30–35% @ 50 mL/kg/min
Bilateral: 55–60% @ 100 mL/kg/min
|
Inexpensive, allows continuous supplementation during manipulation
|
Patient may not tolerate nasal line(s) or jetting of oxygen
|
|
Elizabethan collar with plastic wrap
|
30–40% @ 0.2–0.5 L/min
|
Inexpensive
|
Patient may not tolerate collar; potential for hyperthermia; frequently requires an assistant to monitor patient
|
|
Intra-tracheal
|
40–60% @ 50 mL/kg min
|
Method of provision for patients with upper airway obstruction
|
Airway irritation, potential for tube kinking, potential for sedation, insertion site complications
|
One attempt may be made to place a peripheral intravenous catheter in order to facilitate administration of emergency intravenous medications. The patient should then be placed in a temperature-controlled, oxygen-enriched environment (i.e., oxygen cage) for observation. Should inhaled medications not be available and/or should a patent IV catheter not be available, continued venipuncture should not be attempted. Instead, medications should be given via appropriate alternative routes (IM, SQ), and then the patient should be placed in an oxygen cage.
Patients with respiratory distress require frequent serial evaluations of multiple physical parameters, particularly respiratory rate, respiratory effort, and lung sounds. Additionally, critical care monitoring modalities, particularly pulse oximetry and arterial blood gas analyses, provide invaluable information to afford optimal patient management.
References
References are available upon request.