Priority Topic: Asthma & Priority Topic: Croup

Asthma
Key Feature 2: In a child with acute respiratory distress, distinguish asthma or bronchiolitis from croup and foreign body aspiration by taking an appropriate history and doing a physical examination.
Skill: Clinical Reasoning, Selectivity
Phase: History, Physical

Croup
Key Feature 3: In any patient presenting with respiratory symptoms, look specifically for the signs and symptoms that differentiate upper from lower respiratory disease (ex: stridor vs. wheeze vs. whoop). 
Skill: Clinical Reasoning
Phase: History, Physical

In a patient presenting with respiratory symptoms, it is important to look for signs and symptoms that differentiate upper from lower respiratory disease as this affects the workup to determine the underlying pathology.

As it pertains to the pediatric population (croup is usually a disease of childhood), my differential diagnosis for upper airway problems causing respiratory distress includes:
        1. Foreign body aspiration
        2. Anaphylaxis/angioedema
        3. Infection (croup, epiglottitis, tracheitis, retropharyngeal abscess)
        4. Trauma (mechanical, chemical)
        5. Other (structural, metabolic, neurological)

And my differential diagnosis for lower airway problems causing respiratory distress includes:

1. Bronchiolitis
2. Pneumonia, atelectasis
3. Asthma, bronchospasm
4. Respiratory distress syndrome of the neonate
5. Tracheo-esophageal fistula
6. Pulmonary embolus 

There is a table from UpToDate that gives an overview of the signs that may differentiate signs of upper airway obstruction from lower airway disease. It may be a bit more difficult to use symptoms as a method of distinguishing upper from lower airway disease, particularly in children, as cough, dyspnea, and respiratory distress (the main presenting symptoms for respiratory disease) may present in both processes. 

In a previous post I mentioned how breath sounds can be a very useful clinical sign to distinguish various locations and types of disease pathology. Stridor and stertor both signify upper airway obstruction, while wheeze and crackles tend to signify lower airway pathology. In the Key Feature for this post, it also makes mention of a "whoop" sound, classically known a the sound produced in "whooping cough," otherwise known a pertussis. It sounds like this:

According to some dude Peter Wehrwein, "People with pertussis make a whooping sound because they run out of breath after coughing hard several times in row; the whoop is the sound of a sudden, hard inhale." I have never encountered this sound, in keeping with the fact the pertussis vaccine is now part of the routine child immunization schedule and is now a rare disease. That being said, it is not eradicated either, so if the "whoop" sound is heard, having my ears perked up for suspicion of pertussis would be warranted.