Acute respiratory distress—what to do when they are so blue (Proceedings)

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Acute respiratory distress—what to do when they are so blue (Proceedings)


Definition/etiology

Acute respiratory distress (ARD) is the sudden onset of rapid and/or labored respiratory. It can be caused by pathology or obstruction associated with the nasal passages, oral cavity, pharynx, larynx, trachea, bronchi, alveoli, pulmonary vasculature or lymphatics, pulmonary innervation, chest wall, diaphragm, or pleural space.

Pathophysiology required

Respiratory distress occurs in the following order of progression from least to most severe: increased respiratory rate; change in breathing pattern with increased work of breathing; change in posture; open mouth breathing; cyanosis (paO2 < 60 mmHg); death. Cyanosis, severe work of breathing (active intercostal muscle contraction for movement of the rib cage, open mouth breathing with lips retracted at the commissures), barrel chested appearance of the rib cage, and/or blood or foam coming from the trachea are signs of catastrophic acute respiratory distress. These animals are dying before your eyes. Severe work of breathing is manifested by using the abdominal muscles and diaphragm for chest movement. The amount of work required will be dependent upon how much of the lung or thorax is involved and whether the problem is acute (more work required) or chronic.

Key points primary survey

  • Determine severity of ARD – catastrophic, severe or mild
  • Breathing patterns suggests anatomical location of pathology
  • Assess perfusion and hydration.

Primary survey

Immediately determine if the animal is breathing. If not, intubate and ventilate. Determine the degree of respiratory distress (catastrophic, severe, mild). In an acute severe or catastrophic situation, the animal will assume a body position of relief.

The dog will want to stand with elbows abducted and back arched. As the pathology progresses, the dog will extend his neck and open mouth breath. The cat will tuck the front and rear legs and feet tightly under their body and arch their backs elevating their sternum off of the surface. With chronic distress the cat does not have a specific position of relief

It is important to determine the location of the pathology.(large airway, pleural space disease, parenchymal disease, small airway) by observing the pattern of breathing and careful auscultation. Observation of the rib cage-abdomen junction is ideal to determine whether the chest and abdomen are moving together, in the same direction, or if they are moving in opposition. It is also important to note inspiratory to expiratory time ratio (normally 1:2).

If breathing is loud, heard without the aid of a stethescope, large airway obstruction is the likely cause. Castrophic large airway obstruction presents with severe cyanosis and cardiovascular compromise. The breathing sounds may not be loud if the animal is losing consciousness or is exhausted from trying to breath against an obstruction. Inspiratory stridor suggests upper airway pathology and expiratory stridor suggests lower airway pathology. Stridor on both inspiration and expiration suggests either involvement of the entire trachea such as tracheal collapse or a fixed obstruction such as a mass.

Rapid, shallow breathing with the chest and abdomen moving together, in the same direction at the same time is most compatible with lung parenchymal disease. Auscultation will find louder than normal lung sounds with early disease and crackles and rales in the area of involvement with severe disease. Cats will have louder than normal lung sounds as their primary auscultatory finding unless the lung involvement is severe.

An irregular breathing pattern, with the chest and abdomen moving in opposition to one another is most compatible with pleural space disease. Auscultation may find dull or muffled lung sounds in the location of the pathology. Percussion in large breed dogs can find an area of dullness at the site of the pleural space pathology. Lung sounds can be normal in a cat with pleural space disease. Catastrophic tension pneumothorax will present with the animal having a barrel chested appearance and severe cardiovascular compromise. There will be little chest wall movement. A noncompressible anterior mediastinum suggests an anterior mediastinal mass in the cat.

Short inspiration and prolonged expiration, with an expiratory push of the diaphragm, is compatible with small airway disease. Auscultation should find high pitched wheezes.

Rapid breathing with normal effort will suggest non-respiratory tract related causes such as pain, CNS disease, peripheral nerve pathology, neuromuscular disease, muscle pathology, or metabolic acidosis.

A brief history is immediately obtained to determine if there is known trauma, exposure to rodenticides, past medical history of heart disease or recurrent breathing problems, signs of illness other than ARD, or recent vomiting.