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The use of positive pressure ventilation in dogs & cats with congestive heart failure | VetGirl Veterinary CE Podcasts

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In today’s VetGirl podcast, we review a study published out of North Carolina State University and University of Georgia on the use of positive-pressure ventilation (PPV) in dogs sand cats with congestive heart failure (CHF).

Positive-pressure ventilation (PPV) or mechanical ventilation is a potentially life saving therapeutic that can be used for patients with severe hypoxemia that fail to respond to oxygen therapy and medical management. Traditionally, the use of PPV is limited to the “50:50” rule: in other words, when the partial pressure of dissolved oxygen (PaO2) is < 50 mm Hg (despite oxygen therapy) and the partial pressure of carbon dioxide (PaCO2) is > 50 mm Hg. Check out our podcast with Dr. Lisa Powell, DACVECC on when to ventilate a patient here.

While PPV can be a successful concurrent treatment modality for hypoxemia, it can be quite costly, labor intensive, and fraught with complications (e.g., barotrauma, ventilator-associated pneumonia, etc.). Multiple retrospective studies have been conducted to evaluate the overall outcome and prognosis (See suggested reading below).

So, in this VetGirl podcast, we review the outcome of the use of PPV in dogs and cats with CHF. Severe clinical signs associated with acute, fulminant CHF can sometimes necessitate PPV to stabilize oxygenation and ventilation when medical management (including diuretics, oxygen therapy, and cardiovascular supportive medications) fail. The benefit of PPV in CHF patients is that it allows for alveolar recruitment, improves pulmonary gas exchange, minimizes patient distress (of severe dyspnea), reduces cardiac afterload, among other benefits. In human medicine, PPV (with or without endotracheal intubation) aids in treatment of moderate to severe CHF; however, this specific treatment for CHF has not been evaluated in veterinary patients.

So, Edwards et al conducted a retrospective study evaluating 16 patients (10 dogs, 6 cats) that were clinically and radiographically determined to have CHF. Echocardiographic evidence and necropsy were also used to support the diagnosis in this study. Exclusion criteria included patients with noncardiogenic pulmonary edema, noncardiac contributors to impaired ventilation (e.g., primary pulmonary disease), and lack of intention to treat (e.g., cases ventilated to obtain diagnostics only, prior to euthanasia).

Overall, this study found that 11 patients (69%) survived to extubation, with 10 surviving to discharge (62.5%). Six dogs (60%) and 4 cats (66%) survived. The median survival after discharge was 60 days (with a range of 45-1151 days). What was found to reduce survival in CHF patients treated with PPV was multifactorial:

  • Azotemia with a serum creatinine > 1.4 mg/dL
  • Development of oliguria or anuria
  • Use of pentobarbital in the anesthetic protocol
  • The year that the patient underwent PPV (prior to 2005 cases had a reduced survival)

Overall, this was a great study despite it’s small numbers and retrospective nature. That said, caution must be taken drawing too many conclusions with these limitations. This study does show that the use of PPV can be considered for treatment in patients with CHF. Not surprisingly, patients with underlying renal compromise have a poor prognosis (kidneys + heart = between a rock and a hard place). That said, the outcome for PPV in this study was much higher than previously reported in other studies (see suggested reading below).

Suggested Reading:

1. Lee JA, Drobatz KJ, Koch MW, et al. Indications for and outcome of positive-pressure ventilation in cats: 53 cats (1993-2002). J Am Vet Med Assoc 2005;226(6):924-931.

2. Hopper K, Haskins SC, Kass PH, et al. Indications, management, and outcome of long-term positive-pressure ventilation in dogs and cats: 148 cases (1990-2001). J Am Vet Med Assoc 2007;230(1):64-75.

3. Edwards TH, Coleman AE, Brainard BM, et al. Outcome of positive-pressure ventilation in dogs and cats with congestive heart failure: 16 cases (1992-2012). J Vet Emerg Crit Care 2014;24(5):586-593.

4. Campbell VL, King LG. Pulmonary function, ventilator management, and outcome of dogs with thoracic trauma and pulmonary contusions: 10 cases (1994-1998). J Am Vet Med Assoc 2000;217(10):1505-1509.

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