High-flow nasal oxygen therapy (HFNOT) has emerged as a valuable non-invasive treatment for dogs experiencing respiratory distress. By delivering heated and humidified oxygen at high flow rates, HFNOT enhances oxygenation and reduces the work of breathing. This advanced technique can be an alternative to mechanical ventilation in some cases. High flow nasal oxygen therapy is now available at North Shore Veterinary Specialist and Emergency Centre, and Brisbane Veterinary Specialist Centre.

Clinical Applications:

HFNOT is particularly beneficial in cases of acute respiratory failure due to pulmonary parenchymal disease, and carbon monoxide intoxication. Only contraindications are patients with severe nasal discharge and respiratory failure due to hypoventilation. These patients are not suited for HFNOT. It has also been utilised in cats and foals for similar indications.

Efficacy and Benefits:

Studies have demonstrated that HFNOT improves oxygenation parameters, decreases breathing frequency, and reduces the need for more invasive respiratory support. For instance, a study involving 20 dogs with hypoxaemic respiratory failure showed significant improvements in arterial oxygen levels and respiratory rate after initiating HFNOT.

Safety and Tolerance:

HFNOT is generally well-tolerated by dogs. Complications are rare and typically self-limiting, often resulting in lower morbidity and mortality compared to invasive ventilation techniques. In a study assessing the use of HFNOT during bronchoscopy in dogs and cats, no complications were reported, and the therapy was deemed feasible and safe.

Considerations:

While HFNOT offers significant advantages, it is not a replacement for mechanical ventilation. Oxygen toxicity can occur if patients are maintained at 100% FiOâ‚‚ for extended periods, so careful monitoring is essential. Additionally, the diameter of the nasal prong cannula should be appropriately sized to prevent airway irritation.

In summary, HFNOT is a promising and effective treatment modality for dogs with respiratory distress, offering a non-invasive alternative to mechanical ventilation with a favourable safety profile.

Case Report: Use of high flow nasal oxygen in Greyhound with collapse, coagulopathy, and aspiration pneumonia secondary to suspected snake envenomation

Patient Information:

  • Species: Dog
  • Breed: Greyhound
  • Age: 2 years and 5 months
  • Sex: Male
  • Presenting Complaint: Collapse, and unable to stand at home.

History and Clinical Presentation:

  • A greyhound presented to North Shore Veterinary Specialist and Emergency Centre in the evening after found at home collapsed and unable to stand. The owner reported he was fine earlier in the day. Owner mentioned potential exposure to rat bait. Upon examination, the dog was found to be conscious but collapsed in lateral recumbency. Bleeding was noticed from the gums.

Clinical Findings and diagnostics:

  • Physical Exam: The dog was lethargic, and unable to stand. Mucous membranes were pink, but bleeding was present from the gums. Ecchymosis was noticed on the left hock.
  • Point of care ultrasound: No effusion present in thorax and abdomen.
  • Neurological Examination: No focal neurological deficits, though the dog exhibited generalised weakness.
  • Blood Tests:
    • Coagulation profile and thromboelastography were consistent with clotting factor deficiency, and no strong evidence of hyperfibrinolysis, supporting coagulopathy.
    • Biochemistry showed marginal elevation in ALT and AST, with mild elevation in Creatine kinase (CK), supporting muscle damage.

Case progression:

Patient received treatment for the coagulopathy with a plasma transfusion and vitamin K therapy. The coagulopathy resolved, and the patient was able to stand without support but remained weak. During the hospitalisation period blood tests were repeated and showed marked elevation in CK (from 1100 to 16000 U/L in 48 hours). This made coagulopathy and myopathy secondary to snake envenomation more likely than rodenticide coagulopathy. The patient continued to improve with symptomatic care. Unfortunately, he developed regurgitation and on examination was found to have significant respiratory compromise. Radiographs were performed, which showed alveolar changes in the cranial and middle lung lobes, with a distended oesophagus containing air and fluid. Aspiration pneumonia with megaoesophagus was diagnosed secondary to the neurotoxin of the snake envenomation.

The patient was hypoxaemic and initially, was started on conventional oxygen supplementation via nasal cannula, but despite this, oxygen saturation did not improve significantly, remaining below 89%. HFNOT was initiated with a flow rate of 50 L/min (2 L/kg/min) and an oxygen concentration of 60%. This resulted in immediate improvement in respiratory distress and oxygen saturation, which rose to 95% within hours. 

Outcome:

  • Within 12-24 hours of HFNO initiation, the greyhound’s respiratory status significantly improved, with oxygen saturation stabilizing at 95% on lower oxygen concentrations. The aspiration pneumonia began to show signs of resolution on chest radiographs.
  • Over the next 72 hours, the dog’s condition stabilized, with improvement in the pneumonia and no further episodes of regurgitation or aspiration. The dog was weaned off HFNO and discharged after 5 days with follow-up instructions for continued antibiotic therapy and monitoring

Diagnosis:

  1. Primary Diagnosis: Snake envenomation causing coagulopathy and myopathy.
  2. Secondary Diagnosis: Aspiration pneumonia secondary to gastroesophageal reflux, likely due to the neurotoxic effects of venom.

Discussion: In this greyhound, the coagulopathy and myopathy secondary to the snake bite led to regurgitation and aspiration pneumonia. High Flow Nasal Oxygen was essential in improving respiratory function when traditional oxygen therapy failed, and the dog made a full recovery after appropriate treatment. This case emphasises the use of HFNO for managing severe respiratory distress in a case complicated by aspiration pneumonia.