Respiratory Patterns: A Video Handbook

Respiratory Patterns – A Video Handbook
Alexandre Rousseau, DVM, DACVIM, DACVECC
Cornell University Veterinary Specialists
Respiratory distress is a common presentation of emergency cases in small animal
veterinary practice. Diseases affecting the respiratory system are numerous and
diagnostic plan, treatment approach, and prognosis are directly related to the etiology
and severity. Numerous tools are available which allow the clinician to stabilize the
patient, monitor clinical progress (Pulse oximetry, arterial blood gas) and establish a
diagnosis (thoracic radiographs, echocardiogram, CT scan, bronchoscopy, etc).
However, stability of the patient can sometime delay diagnosis and therapy. A thorough
history, along with physical examination findings is of extreme importance. Utilizing
video and pictures, we will discuss several classic and more complicated cases
presented to our Emergency and Critical Care department.
The main function of the pulmonary system is to accomplish gas exchange. The lung
also acts as a blood reservoir, filters the microcirculation, and has important metabolic
and immunologic functions.
During gas exchange, the lungs move oxygen (O2) from the atmosphere into the blood
and evacuate carbon dioxide (CO2). The alveolar-capillary (blood-gas) interface is
extremely efficient as it has a large surface area (human lung ~50-100m2) and a very
thin barrier (0.3-0.5um).
To understand the patient with respiratory difficulty, it is also important to have a good
understanding of the mechanics of breathing. During inspiration, the diaphragm
contracts and moves caudally, creating a lower (more negative) intrapleural pressure.
External intercostal muscles also promote inspiration by moving the rib cage cranioventrally. Accessory muscles of inspiration are not observed during quiet breathing but
can contract vigorously during exercise and severe respiratory distress.
Expiration is passive during quiet breathing as the lungs and chest wall tend to return
to equilibrium after expansion. The most important expiratory muscles are the
abdominal muscles. Contraction of the internal intercostal muscles moves the ribs
caudo-dorsally therefore increasing pleural pressure, forcing air out.
The Respiratory System and its components
Upper airways:
Nose and nasal passages, choana, mouth, pharynx, larynx, and
trachea
Lower airways:
Bronchi, bronchioles
Lungs:
Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
During the assessment of a patient with respiratory disease, a clinician should try to
establish the possible source of the problem. Specific breathing patterns can be
observed with diseases affecting certain areas of the pulmonary system. Unfortunately,
patients with respiratory disorders commonly have more than one part of their
respiratory tract affected. For example, it is not uncommon to manage a patient with
laryngeal paralysis and aspiration pneumonia, and it has been well established that
patients with chronic asthma develop pulmonary parenchymal disease such as fibrosis.
First, establish whether the breathing disorder occurs during inspiration or expiration.
Expiratory disorders are quite specific and suggest intra-thoracic airway disease (lower
airway disease-bronchi/bronchioles). The presence of abnormal respiratory sounds such
as snoring, stertor, stridor, sneezing and reverse sneezing is more suggestive of upper
airway disease. Coughing, although significant in the assessment of your patient, is not
specific. Patients with lung disease (i.e. pneumonia), lower airway disease (i.e Feline
allergic bronchitis) and upper airway disease (i.e. tracheal collapse, kennel cough) can
exhibit coughing. The frequency and progression of a cough, concomitant hypoxemia,
and level of sickness are all important factors when trying to establish a proper
diagnostic and therapeutic plan.
Criteria of Stridorous and Stertorous Breathing
STRIDOR
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•
•
•
•
high pitched wheezing
turbulent air flow
upper airway
primarily inspiratory
musical
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•
•
•
•
STERTOR
poorly defined
harsh discontinuous
crackling sounds sonorous
snoring sound
no musical quality
If the inspiratory disorder is “non-noisy”, consider lung disease or pleural disease.
These disorders are commonly associated with abnormal lung sound on auscultation. As
previously discussed, the presence of abnormal upper respiratory sounds may interfere
with a proper thoracic auscultation. Muffled or absent pulmonary sounds are suggestive
of pleural space disease or space occupying masses. When severe, patients with pleural
space disease will have an exaggerated abdominal component to their inspiration due
to the limitation of thoracic expansion. Pulmonary crackles, wheezes and rales are
suggestive of lung pathology (including congestive heart failure) or bronchiolar
pathology.
Finally, as we will see with numerous video examples, physical examination and
understanding of respiratory patterns can be helpful in guiding diagnostic tests and
therapeutic options, and can expedite the recovery or establish an adequate prognosis
for respiratory patients.