Page 2008 - Cote clinical veterinary advisor dogs and cats 4th

Upper Airway Obstruction 1005

• Subglottic structures: tracheal collapse deliberate inspiration and rapid exhalation), ○ Anxiolytic drugs (e.g., trazodone 2-7 mg/
(p. 194), FB, tracheal neoplasia, tracheal often with the point of stridor audible in kg PO q 12h)
VetBooks.ir to the airway (e.g., thyroid carcinoma, lesion. Stertor, in nonbrachycephic breeds, may Nutrition/Diet Diseases and Disorders
hypoplasia, trauma. Mass lesions external
the upper airway, helps localize the anatomic
be indicative of altered upper airway airflow.
cervical abscess) can cause narrowing or
Weight loss diet may be indicated for long-term
collapse of the airway.
Signalment, history, and exam findings usually
allow a refined differential diagnosis. Oral treatment of obesity.
HISTORY, CHIEF COMPLAINT and laryngeal exam, diagnostic imaging, and Behavior/Exercise
• Loud breathing (new stertor or stridor) is endoscopy confirm the site (and sometimes Avoid heat stress.
most consistent finding. Respiratory effort nature) of the obstruction.
may be mild or severe. Acute distress after Possible Complications
playing with an object (e.g., ball) suggests Differential Diagnosis Recurrence of clinical signs, aspiration pneu-
FB obstruction. Neoplasia may manifest as Occasionally, pleural effusion in cats mimics monia, noncardiogenic pulmonary edema, and/
progressive dyspnea. Laryngeal paralysis often upper respiratory obstruction. or respiratory arrest
is accompanied by a change in the sound
of the bark (dysphonia). Clinical signs often Initial Database Recommended Monitoring
are exacerbated by exercise, excitement, or • Oral/laryngeal exam under sedation Monitor respiratory rate/effort, oxygenation,
on a warm day. is the most important diagnostic test and ventilatory status.
• Foreign object (e.g., ball, marble, acorn) (p. 1125).
aspiration may be witnessed, although the ○ Be prepared for an emergent intubation PROGNOSIS & OUTCOME
mistaken belief that an FB has been aspi- or tracheostomy (and possibly positive-
rated is a common error that some clients pressure ventilation if noncardiogenic • Depends on the underlying problem and
believe passionately (“something stuck in the pulmonary edema is present (pp. 1166 severity of clinical signs
throat”) even when the problem is clearly and 1185). • Prognosis worse for cases with noncardiogenic
different (e.g., pulmonary edema, pleural ○ Doxapram 2.2 mg/kg IV can stimulate pulmonary edema or pneumonia
effusion). ventilation during exam but may
result in glottic constriction requiring PEARLS & CONSIDERATIONS
PHYSICAL EXAM FINDINGS intubation.
• Noisy, stridorous (laryngeal or subglottic) • Ancillary testing includes radiographs (cervi- Comments
or stertorous (nasal or nasopharyngeal) cal and thoracic), CBC, serum biochemistry • Up to one-half the diameter of the airway
breathing profile, and evaluation of oxygenation can be compromised without obvious clinical
○ Typically exaggerated inspiratory effort (pulse oximetry or arterial blood gas [ABG] signs.
○ Noise may be heard only on inspiratory analysis). • Major errors include underestimating the
(dynamic obstruction) or during both patient’s distress, overzealous exam without a
phases (fixed obstruction). Advanced or Confirmatory Testing set action plan (e.g., having tools for intuba-
• Sometimes, orthopneic posture, cyanosis, Bronchoscopy (p. 1074), fluoroscopy, or CT tion immediately available), and performance
paradoxic breathing (chest and abdomen may be useful for evaluating focal lesions and of tests or procedures that are detrimental
move in opposition), bulging at thoracic inlet dynamic changes or for obtaining biopsies or to the condition of the patient at that
(lung lobe herniation), Horner’s syndrome cytologic specimens. time.
(nasopharyngeal polyp) • A common radiographic misdiagnosis is the
• Hyperthermia possible (excessive muscle TREATMENT interpretation of a prominent or mineralized
activity, ineffective cooling) (but normal) larynx as an FB, especially if
• Specific conformations (e.g., short nose) Treatment Overview the neck is radiographed obliquely.
raise the suspicion of associated malforma- Minimize stress while making diagnosis; • Thoracic radiography and positive-pressure
tions. sometimes the diagnosis and treatment occur ventilation should be planned in case dyspnea
• Loud sounds may be referred to the lower simultaneously (e.g., FB is identified and and/or hypoxemia persist after relief of upper
airways; auscult over the trachea to help removed). A general approach to treatment is airway obstruction, as can occur when
determine origin. provided on p. 1453. noncardiogenic pulmonary edema is also
• Obesity may magnify clinical signs. present.
Acute General Treatment • Dogs may be presented with pulmonary
Etiology and Pathophysiology • Sedatives or analgesics, glucocorticoids edema after a choking episode has resolved
• Most resistance to airflow occurs in the upper at antiinflammatory doses, and oxygen (e.g., “hanging” on chain).
airways. Any fixed or dynamic obstruction supplementation (p. 1146) can be
in the upper airways increases resistance to lifesaving. Prevention
breathing and, subsequently, the work of • Secure airway patency if necessary (p. 1166). Avoid overexertion, prevent heat stress, and
breathing. • Hyperthermia (i.e., muscle activity or ineffec- know the medical options that are avail-
• Inspiration against a partially or completely tive cooling, not true fever) can respond to able to help break the cycle of distress and
closed upper airway may cause noncardio- physical cooling but not to antiinflammatory dyspnea. Stenotic nares should be repaired
genic pulmonary edema as the alveoli become drugs (p. 421). early in life.
flooded with plasma due to negative pressure • Remove foreign object, if present.
generated in the airways. Technician Tips
Chronic Treatment Minimize stress by using minimal restraint
DIAGNOSIS • Surgical correction: laryngeal tie-back and pursuing treatments in a stepwise manner.
procedure, remove nasopharyngeal polyp, Procedures (e.g., catheter placement, blood
Diagnostic Overview repair stenotic nares, and so forth sampling, individual radiographs) may need
Upper airway obstruction is recognized on • Medical management to be staged, depending on the stability of the
physical exam. Inspiratory dyspnea (restrictive ○ Environmental control (e.g., avoid neck animal. Injectable medications may be preferred
breathing pattern characterized by a slow and leads, avoid excessive heat) to oral.

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