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A Respiratory Pattern‐Based Approach to Dyspnea
Christopher G. Byers, DVM, DACVECC, DACVIM (SAIM), CVJ

CriticalCareDVM.com, Omaha, NE, USA

The initial approach to a patient with respiratory distress shallow tachypnea. The initial evaluation of a patient
is of the utmost importance as it can determine whether should ideally begin from afar, as the breathing pattern
these critical patients live or die. Classic clinical signs of may change with manipulation. Making an accurate
respiratory distress include tachypnea, head and neck assessment after handling can be far more challenging.
extension, open‐mouth breathing, anxiety, cyanosis,
nares flaring, abducted elbows, orthopnea, and paradox-
ical movement of the chest and/or abdomen. Overt signs Upper Airway
of respiratory distress are more commonly seen in dogs
than cats. Unfortunately, cats readily mask disease sever- The upper respiratory tract, that includes the nares,
ity, and commonly the only evidence of respiratory dys- nasal cavity, pharynx, and larynx, is simply a conduit
function may be tachypnea and prominent respiratory from the nares to the glottis. Diseases of the upper res-
motions in sternal recumbency. piratory tract are relatively common in both dogs and
The first step in examining a patient with a respiratory cats (Table 29.1). Upon presentation, the owner may
emergency is to perform a primary survey, efficiently report that a patient snores and/or has exercise intoler-
evaluating airway, breathing, and circulation (ABCs). ance, dysphagia, regurgitation, and/or posttussive retch-
If the airway is not patent, it must be cleared of obstruc- ing. They may also report that these clinical signs
tion and immediate orotracheal intubation performed. If are associated with and/or exacerbated by excitement,
an upper airway obstruction prevents orotracheal intu- humidity, and/or elevated ambient temperatures.
bation, an emergency tracheostomy must be performed. Physical examination may identify referred upper airway
If there are no airway patency issues, a clinician should sounds, orthopnea, bilateral elbow abduction, restless-
evaluate the patient’s breathing pattern and work of ness, dysynchronous breathing, and cyanosis. Affected
breathing. Particular attention should be given to the patients commonly have abnormal respiratory sounds
phase of breathing affected, and effort should be made to and pattern of breathing; the classic upper airway breath-
determine if the breathing pattern is obstructive or ing pattern is characterized by increased inspiratory
restrictive. time and effort compared to expiration. Increased nasal
Anatomical localization of the cause of respiratory dis- noise (stertor) and/or laryngeal noise (stridor) may also
tress is assessed through a “look, listen and feel” approach, be present, depending on the site of airflow turbulence.
and may be a very powerful tool for assessing underlying Occasionally, pulmonary crackles that form due to
structural changes. Increased inspiratory effort is com- noncardiogenic pulmonary edema may be auscultated.
monly associated with extrathoracic disorders while Diseases of the upper airway commonly cause at least
increased expiratory effort is most often due to intratho- partial airway obstruction that markedly reduces proper
racic diseases. An obstructive breathing pattern indi- airflow. The resultant turbulent airflow promotes the
cates inappropriate movement of air into and/or out of formation of edema and inflammation that subsequently
the lungs and is frequently associated with a slower res- increases the work of breathing and further narrows the
piratory rate and deeper breaths than normal. A restric- affected airway, creating a vicious cycle. Combined with
tive breathing pattern is characterized by inadequate a reduced ability to effectively eliminate heat from the
expansion of the chest wall and/or lungs, resulting in body via evaporation, affected patients may readily

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical