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Basics ⬇

Basics

Definition

  • Tachypnea-increased respiratory rate.
  • Panting-rapid, shallow, open-mouth breathing that is usually not associated with gas exchange issues.

Pathophysiology

  • Respiratory rate, rhythm, and effort are controlled by the respiratory center in the brainstem in response to numerous afferent pathways, both central and peripheral in origin. These include the cerebral cortex, central chemoreceptors, peripheral chemoreceptors, stimulation of mechanoreceptors in the airways that sense lung inflation and deflation, stimulation of irritant receptors of the airways, stimulation of C-fibers in the alveoli and pulmonary blood vessels that sense interstitial congestion, and baroreceptors that sense changes in blood pressure.
  • Tachypnea and panting can occur in response to stimulation of any of the above receptor pathways.

Systems Affected

Respiratory

Signalment

  • Dog and cat; no age, or sex predilection.
  • Older, large breed dogs predisposed to panting associated with laryngeal paralysis.
  • Brachycephalic dogs prone to panting due to upper airway obstruction.

Signs

Historical Findings

  • Patients with primary respiratory or cardiac disease usually have associated coughing or exercise intolerance.
  • Non-respiratory causes-clinical complaints associated with the primary disease, e.g., PU/PD/PP with hyperadrenocorticism, intermittent signs of systemic hypertension with pheochromocytoma.

Physical Examination Findings

  • Brachycephalic syndrome (stenotic nares, stertorous respirations associated with soft palate elongation or saccular eversion) may be observed.
  • Stridor can be evident on inspiration with upper airway diseases.
  • Lower airway disease-cough, expiratory wheezes on auscultation, abdominal effort.
  • Pulmonary parenchymal disease-may have crackles on auscultation; harsh or moist lung sounds common, may be normal.
  • Cardiogenic pulmonary edema-heart murmur or arrhythmia, tachycardia, gallop sound, hypothermia, pale mucous membranes, poor capillary refill time.
  • Pleural space disease-diminished breath sounds: ventrally-fluid; dorsally-air; unilaterally-space-occupying lesions, pyothorax, chylothorax.
  • Thoracic wall disease-visible and/or palpable trauma.
  • Non-respiratory diseases-findings will depend on the other diseases, e.g., pale mucous membranes if anemic, hepatomegaly with hyperadrenocorticism.
  • Other signs could indicate trauma.

Causes & Risk Factors

Panting

  • Pain, anxiety, hyperthermia.
  • Brachycephalic airway syndrome.
  • Central nervous system disease causing abnormal ventilatory control.
  • Cardiovascular compromise (shock), hypertension, arrhythmia.
  • Drug therapy (opioids)
  • Metabolic acidosis.
  • Laryngeal disease.
  • Cortisol or norepinephrine excess.
  • Can be a normal behavioral pattern in some dogs.

Tachypnea

  • Hypoxemia, hypercapnia, hypotension, hyperthermia, anemia, acidosis, systemic inflammation, brainstem disease.
  • Airway pathology-inhaled irritant, bronchoconstriction, airway compression, airway infection.
  • Interstitial pathology-edema, hemorrhage, inflammation, neoplasia, fibrosis.
  • Larynx-laryngeal paralysis, edema, collapse, foreign body, neoplasia, inflammation, trauma, webbing.
  • Trachea-collapse, stenosis, trauma, foreign body, neoplasia, parasites.
  • Lower airway disease-allergic disease, inflammation, infection (Mycoplasma), parasites, neoplastia.
  • Pulmonary parenchymal disease-edema (cardiogenic or non-cardiogenic), pneumonia or pneumonitis, neoplasia (primary or metastatic), hemorrhage.
  • Pulmonary thromboembolism associated with-IMHA, PLE, PLN, cardiac disease, neoplasia, heartworm disease.
  • Pericardial effusion.
  • Pleural effusion or pneumothorax.
  • Abdominal distention-organomegaly; neoplasia, pregnancy; obesity; ascites; gastric dilatation, torsion.
  • CNS disease-compression or infarct near the respiratory center.
  • Metabolic acidosis-diabetic ketoacidosis, diarrhea, uremia, renal tubular acidosis.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Tachypnea without respiratory distress-may be a non-respiratory problem.
  • Stertor and stridor are features of upper airway disease-auscultation over the trachea can help delineate upper airway noises from lower airway noises.
  • Thoracic auscultation and percussion-most useful for distinguishing pleural disease (dampened lung sounds, dull percussion) from parenchymal disease (normal, harsh or moist lung sounds, crackles on auscultation).
  • Wheezes on auscultation are suggestive of narrowed lower airway (bronchi, bronchioles).
  • Crackles on auscultation are features of airway collapse, bronchitis, edema, or other pulmonary parenchymal diseases.
  • Congestive heart failure-murmur, tachycardia, poor pulse quality, jugular pulses.

CBC/Biochemistry/Urinalysis

  • Anemia-can cause non-respiratory tachypnea.
  • Polycythemia-chronic hypoxia.
  • Inflammatory leukogram-pneumonia, pneumonitis, pyothorax, or non-respiratory causes (SIRS, sepsis).
  • Eosinophilia-hypersensitivity or parasitic airway disease.
  • Thrombocytosis-hyperadrenocorticism predisposes to PTE; alternatively, could indicate iron deficiency anemia.
  • Sodium:potassium ratio <27-can be seen with pleural or abdominal effusions.
  • High alkaline phosphatase-hyperadrenocorticism predisposes to panting and PTE.
  • Hypoproteinemia-may suggest protein losing disease that can predispose to PTE.
  • Proteinuria-can predispose to PTE.
  • Azotemia-if severe can lead to uremic pneumonitis.
  • Hyperglycemia, glucosuria, and ketonuria-could indicate ketoacidosis as cause of tachypnea.

Other Laboratory Tests

  • Fecal examinations if indicated.
  • Low dose dexamethasone suppression test to assess adrenal cortical function, if indicated.
  • Pleural fluid analysis.
  • Serum antigen or antibody titers-heartworm, toxoplasmosis, distemper, FeLV, FIV.
  • Pulse oximetry or arterial blood gas-can help differentiate pulmonary from non-respiratory causes.
  • Hemoglobin saturation with oxygen <95% supportive of hypoxemia.
  • PaO2-partial pressure of oxygen dissolved in arterial blood; normoxemia: PaO2 80–120 mmHg (room air, sea level), hypoxemia: PaO2 <80 mmHg; FIO2-fraction of inspired oxygen ranges from 0.21 (room air) to 1.0; PaO2/FIO2 ratio-measure of lung efficiency; PaO2/FIO2500-normal lung efficiency; 300–500-mild insufficiency; 200–300-moderate insufficiency; <200-severe insufficiency. Reduction in lung efficiency is most commonly due to pulmonary parenchymal disease.
  • PaCO2 or PvCO2-partial pressure of CO2 dissolved in arterial or venous blood; measure of ventilation; normal 30 mmHg < PCO2 <40 mmHg. Hypercapnia = hypoventilation = decreased alveolar minute ventilation. Hypocapnia = hyperventilation = increased alveolar MV. Hypoventilation can be due to upper airway obstruction, pleural space disease, thoracic wall disease and abdominal distention; respiratory muscle fatigue from a prolonged period of tachypnea can lead to hypoventilation.
  • Blood gas may reveal metabolic acidosis as a cause.
  • Coagulation testing-if suspect hemothorax and/or pulmonary hemorrhage.

Imaging

  • Cervical and thoracic radiography: laryngeal disease-increased density could suggest edema or soft tissue mass lesion. Also can see large airway narrowing, lymphadenopathy, intraluminal abnormalities. Lower airway disease-bronchial thickening, middle lung lobe consolidation (cats), atelectasis, hyperinflation and diaphragmatic flattening (primarily cats). Pneumonia-alveolar infiltrates; aspiration pneumonia usually cranioventral distribution or middle lobe affected. Cardiogenic pulmonary edema-enlarged cardiac silhouette, pulmonary venous distention, enlarged left atrium with perihilar pulmonary infiltrates in dogs; infiltrates can be of any distribution in cats. Noncardiogenic pulmonary edema- caudodorsal distribution. ARDS-diffuse, symmetrical alveolar infiltrates. Pulmonary vascular abnormalities-PTE, heartworm disease. Pleural space disease-pneumothorax, pleural effusion, mass lesions, diaphragmatic hernias. Thoracic wall disease-rib fractures, neoplasia.
  • Thoracic ultrasonography: evaluation of distribution of pleural effusion (excellent as guide for thoracocentesis), pneumothorax (absence of “glide sign”), and parenchymal disease (presence of “comet tail” artifact). Pulmonary mass identification-guide fine-needle aspiration; mediastinal evaluation.
  • Echocardiography: evaluate cardiac function if cardiogenic pulmonary edema or pleural effusion suspected; elevated pulmonary artery pressure and right ventricular overload can support diagnosis of PTE; visualize heart-based masses, rule out pericardial effusion.
  • Abdominal ultrasound: evaluation of abdominal distention, assess adrenal gland size.
  • Fluoroscopy: evaluate tracheal and/or large airway collapse; evaluate diaphragmatic function.
  • Computed tomography: airway, pulmonary parenchymal, and pleural space disease can be evaluated; can detect lesions not clearly defined on radiographs but requires general anesthesia.
  • Pulmonary vascular angiography: gold standard for diagnosis of PTE but requires general anesthesia.
  • Perfusion scintigraphy: abnormal perfusion scan is considered supportive of PTE.
  • May need CNS imaging.

Diagnostic Procedures

  • Laryngoscopy/nasopharyngoscopy/tracheoscopy-to evaluate laryngeal function and visualize foreign bodies and masses; visualize caudal nasopharyngeal region with flexible endoscope or spay hook and dental mirror.
  • Bronchoscopy-evaluate large and small airways; take biopsies; perform bronchoalveolar lavage for cytology and culture.
  • Thoracocentesis-fluid analysis and culture.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

  • Inpatient care if life-threatening; therapy depends on underlying cause.
  • Administer oxygen and see if tachypnea resolves-this would be supportive of a primary respiratory problem.
  • Upper airway disease-use sedation to reduce inspiratory effort. Check body temperature frequently and actively cool patients as needed. Severe upper airway disease requires intubation to stabilize; if the problem cannot be immediately cured, placement of a temporary tracheostomy tube is indicated. Remove foreign bodies; perform surgical excision/biopsy of masses, surgical correction for laryngeal paralysis and brachycephalic syndrome; give anti-inflammatory medications for laryngeal edema.
  • Lower airway disease-bronchodilators; oxygen therapy until stable; systemic corticosteroids may be required to stabilize cats with acute bronchoconstriction.
  • Pulmonary parenchymal disease-oxygen therapy, antibiotics if pneumonia; treat coagulation disorders; cardiogenic edema requires furosemide ± vasodilators. Non-cardiogenic edema requires oxygen therapy, may require positive-pressure ventilation if oxygen therapy alone is not adequate to stabilize the patient.
  • Pleural space disease-thoracocentesis for air and fluid. Place a chest tube if repeated chest taps are needed to keep patient stable.
  • Abdominal distention-drain ascites only as needed to keep the patient comfortable; relieve gastric distention.
  • Non-respiratory diseases-treat primary problem.

Nursing Care

  • Oxygen therapy via cage, nasal cannula, E-collar covered in plastic wrap, mask, or flow-by. Humidify oxygen source if giving oxygen therapy for more than a few hours.
  • Monitor temperature regularly, as hyperthermia will worsen respiratory difficulty.

Diet

Weight-reducing diet if obesity is a contributing cause.

Surgical Considerations

  • Anesthesia must be carefully tailored to the patient. Securing an airway is essential and rapid intravenous induction is important. Have multiple sizes of endotracheal tubes available if upper airway obstruction is suspected.
  • If laryngeal paralysis or brachycephalic syndrome is suspected, prepare for surgical correction at the time of diagnosis. Warn owners of increased likelihood of aspiration pneumonia in dogs with laryngeal disease.

Medications ⬆ ⬇

Medications

Drug(s)

Varies with underlying cause (see “Appropriate Health Care”).

Miscellaneous ⬆

Miscellaneous

Abbreviations

  • ARDS = acute respiratory distress syndrome
  • CNS = central nervous system
  • FeLV = feline leukemia virus
  • FIV = feline immunodeficiency virus
  • IMHA = immune-mediated hemolytic anemia
  • MV = minute ventilation
  • PLE = protein-losing enteropathy
  • PLN = protein-losing nephropathy
  • PTE = pulmonary thromboembolism
  • PU/PD/PP = polyuria, polydipsia, polyphagia
  • SIRS = systemic inflammatory response syndrome

Authors Yu Ueda and Kate Hopper

Consulting Editor Lynelle R. Johnson

Suggested Reading

Forney S. Dyspnea and tachypnea. In: Ettinger SJ, Feldman EC, eds., Textbook of Small Animal Internal Medicine, 7th ed. Philadelphia: Saunders Elsevier, 2010, pp. 253–255.

Mandell DC. Respiratory distress in cats. In: King LG, Textbook of Respiratory Disease in Dogs and Cats. Philadelphia: Saunders, 2004, pp. 12–17.