Improving outcomes for patients in respiratory distress

Providing oxygen via a face mask (left) with flow rates of 2 to 3 L/min can increase FiO2 to 35% to 55%, whereas using anesthetic machine tubing (right) at the same flow rate only increases FiO2 to 24% to 45%.

We have all heard the STAT triage call to the lobby for the “panting” cat, or spoken on the phone with a panicked owner whose French bulldog is wheezing uncontrollably after playing fetch outside in the heat. Streamlining nursing care for patients in respiratory distress is critical to improving outcomes. Preparation, triage, assessment, and establishing a treatment plan based on the clinical signs can increase the odds that the patient will be discharged safely from the hospital.

Preparation, triage, and initial assessment.

The minute a technician hears that a respiratory emergency is presenting to the hospital, it is time to get ready. Vascular access supplies, a way to evaluate and secure the airway (ie, appropriately sized endotracheal tubes, laryngoscope), and a plan to provide supplemental oxygen should be in place before the patient enters the treatment area.

Immediate nursing care steps should include the following:

• Evaluate the patient’s airway and intubate, if needed.
• Perform an initial assessment by obtaining the patient’s baseline temperature, respiratory rate and effort, heart rate, pulse oximetry parameters (if the patient allows), mucous membrane color, capillary refill time, mentation, and posture.¹
• Provide supplemental oxygen therapy.
• Obtain vascular access.
• Begin active cooling therapy depending on patient temperature.
• Provide sedation/anxiolytic therapy.
• Obtain a thorough patient history.

A thorough patient history can change the treatment plan significantly. Asking guiding questions will greatly aid in the ability to gather a more complete clinical picture:

• Did the respiratory signs come on abruptly, or has the animal been declining over time?
• Do you give daily, weekly, or monthly medications?
• Does the pet have any previously diagnosed conditions or illnesses?
• Has this happened before?
• Has the patient had anesthesia or sedation recently?
• Is there any chance of toxicity or trauma?
• Has the animal gone missing recently?
• Does the animal frequently get tired after exercising or in the heat?

Answers to these questions will assist the practitioner or veterinary team in determining whether the patient is suffering from upper airway, lower airway, pulmonary parenchymal, or pleural space disease.

Providing supplemental oxygen therapy

An immediate treatment step for patients in respiratory distress is to provide supplemental oxygen. This can be accomplished in a number of ways, including via oxygen cage, face mask, or nasal oxygen cannula. The goal of supplemental oxygen therapy is to increase the percentage of oxygen in the air the patient is breathing (FiO2, Table 1). Normal FiO2 of room air is 21%.

Increasing the FiO2 around the patient can rarely be accomplished by providing “flow-by” oxygen via anesthetic machine tubing because oxygen disperses too quickly in open space (Figure 1). If an oxygen cage is not available, and the patient is stressed by placement of a face mask or nasal cannula, anxiolytic therapy should be considered to facilitate appropriate supplementation. It is important to note that nasal oxygen cannulas are irrelevant in brachycephalic breeds due to their abnormal facial anatomy.²

Causes of respiratory distress

Upper airway disease

The upper airway consists of the larynx, trachea, and nasopharynx. Brachycephalic airway obstruction occurs in both dogs and cats. The most commonly affected canine breeds include bulldogs, boxers, pugs, Cavalier King Charles spaniels, shih tzus, and mastiffs. Among cats, Persians and British shorthair are the breeds frequently affected. Other upper airway diseases include laryngeal paralysis (seen more often in geriatric Labrador and golden retrievers, and hypothyroid dogs), tracheal collapse (Yorkshire terriers and Chihuahuas), and nasopharyngeal polyps (juvenile cats).

The most noticeable clinical signs of upper airway disease are loud and stridorous inspiratory effort, and cyanosis. These patients often require anxiolytic therapy to facilitate appropriate nursing care (Table 2). Sedation with butorphanol, acepromazine, or dexmedetomidine (Figure 2) can allow the patient to become relaxed enough to tolerate a face mask, intravenous catheter placement, and cooling therapy, if indicated.

Figure 2. A dog with suspected laryngeal paralysis presented with significant respiratory stridor (top). Fifteen minutes after administration of oral transmucosal acepromazine (0.05 mg/kg), the patient was sedate but rousable and had significantly decreased respiratory effort and stridor (bottom).

Patients with upper airway disease, specifically brachycephalic breeds, often present with hyperthermia, and active cooling must be initiated if the animal’s temperature exceeds 105 °F(personal communication, Dickerson N, University of California, San Francisco, 2020). Active cooling is achieved by maximizing heat dissipation mechanisms and can be accomplished by dousing the entire body with tepid water, increasing air circulation over the body with fans to improve evaporation, and intravenous fluid therapy.³ Care must be taken when initiating active cooling, and it should be stopped once the patient’s temperature has dropped to 103 °F, as body temperature will continue to drop and patients may become hypothermic.

Depending on patient history, glucocorticoids such as dexamethasone sodium phosphate (0.1-0.25 mg/kg via slow IV) may be administered at the discretion of the veterinarian to reduce laryngeal swelling.

Careful handling and reducing stress are critical to providing appropriate nursing care to the patient in respiratory distress. It is important to monitor carefully for adverse effects of anxiolytic medications as patients can become oversedated and occlude their own airway if not watched closely. Pulse oximetry (with the probe on the lip, toe, vulva, or prepuce), electrocardiography, and blood pressure (oscillometric or Doppler) should be monitored as soon as the patient is tolerant.

Lower airway disease

Lower airway disease involves expiratory airway obstruction. Patients presenting with lower airway obstruction are able to move air into their trachea and lungs, but have constriction or obstruction when trying to exhale, resulting in expiratory effort.

Lower airway diseases include feline asthma (common in Siamese cats) and canine chronic bronchitis (in Northern breed dogs, such as the Siberian husky, Alaskan malamute, and samoyed); lower airway disease can also result from acute anaphylaxis. Clinical signs include coughing, wheezing, and gagging in dogs, and an abdominal “push” on expiration in cats.¹

Pulmonary parenchymal disease

Pulmonary parenchymal disease is marked by decreased pulmonary compliance, meaning the lungs cannot expand properly. Pulmonary parenchymal diseases affect the terminal and respiratory bronchioles, interstitium, alveoli, and vasculature.⁵ Examples include pneumonia (aspiration or bacterial), cardiogenic pulmonary edema, non-cardiogenic pulmonary edema (secondary to choking or near-drowning, electrical cord bites, snake bites, sepsis, upper airway obstruction, and adult respiratory distress syndrome),⁵ and pulmonary contusions from trauma such as being hit by a car.

In addition to inspiratory and expiratory effort, clinical signs include crackles and wheezes on thoracic auscultation.⁵ Treatments include diuretics (cardiogenic and noncardiogenic pulmonary edema), antibiotic therapy and hydration (pneumonia), and supplemental oxygen. Nebulization could be a useful treatment tool in patients with pneumonia.

Pleural space disease

Patients with pleural space disease typically present with rapid, shallow breathing because of the lung’s limited ability to expand and ventilate. These patients are working hard to breathe. If the pleural space is filled with air, neoplastic tissue, fluid, or other organs (eg, diaphragmatic hernia), the lungs have less room to expand normally. Common disease processes that result in pleural space disease include pleural effusion (secondary to heart failure or neoplasia), pneumothorax (secondary to infection, foreign material, or trauma), and hemothorax.

Thoracentesis to remove air or fluid from the pleural cavity can almost immediately alleviate clinical signs in these patients; in some cases a chest tube can be placed to facilitate drainage procedures. Once the animal is stable, it is typically placed in an oxygen kennel while a diagnostic plan is being determined. Diagnostics can include TFAST (quick thoracic ultrasound), thoracic radiography, advanced imaging (computed tomography, echocardiography), and cytology of any aspirated fluid.¹

Conclusion

Technicians play a crucial role in the initial evaluation and treatment of patients in respiratory distress. Careful preparation, providing initial treatments, evaluating clinical signs, and obtaining a careful patient history can significantly improve outcomes for these patients.

Jordan Sanchez, RVT, has been in working veterinary medicine for nearly a decade, practicing in shelter medicine, field medicine, and specialty anesthesia. She currently works as an anesthesia technician in Portland, Oregon, and plans to pursue veterinary technician specialty certification in anesthesia and analgesia.

References

1. Sumner C, Rozanski E. Management of respiratory emergencies in small animals.Vet Clin Small Anim Pract. 2013;43:799-815. doi:10.1016/j.cvsm.2013.03.005
2. Sharp CR. Approach to respiratory distress in dogs and cats. Todays Veterinary Practice.https://todaysveterinarypractice.com/approach-to-respiratory-distress-in-dogs-and-cats. Accessed September 20, 2020.
3. Hemmelgarn C, Gannon K. Heatstroke: Clinical signs, treatment and prognosis.VetLearn.com. http://vetfolio-vetstreet.s3.amazonaws.com/94/d5ef00bd5e11e28e71005056ad4736/file/PV2013_Hemmelgarn2_CE.pdf. 2013. Accessed September 20, 2020.
4. Plumb DC. Plumb’s veterinary drug handbook. 5th ed. Wiley-Blackwell; 2011.
5. Hackett T. (2009). Pulmonary parenchymal disease. dvm360. https://www.dvm360.com/view/pulmonary-parenchymal-disease-proceeding. Accessed April 24, 2020.