Acute Dyspnea – 1

DYSPNEA.  Literally “difficult breathing,” a potentially lethal complaint.  In English we say “Short Of Breath,” hence the common abbreviation SOB [one reason some clinicians won’t let patients peruse their charts].  Based on chronology, divide the differential into Acute Dyspnea [less than 2-3 weeks duration], and Chronic Dyspnea [3-4 weeks or more].

But first, let’s touch on LIFE-THREATENING DYSPNEA, defined purely by our own eyes.  If a patient presents to your out-patient office or clinic gasping for breath, call 911 and generate a quick working diagnosis to keep them alive until the E.D.

Stethoscopes help distinguish diagnoses, they don’t tell how sick somebody is.  Look at the patient (though it’s good to know their baseline, which may not be possible).

  • Central cyanosis (face) implies imminent death or intubation.
  • Use of accessory muscles in an adult [first appearing at the tracheal notch, then as supraclavicular retractions, and finally intercostally] denotes significant hypoxia.
  • A respiratory rate ≥28/min. is serious, if not due to panic attack or fever.

Agitation, leading to confusion, suggests life-threatening hypoxia.  It’s impossible to distinguish the delirium of life-threatening dyspnea from that of simple drug intoxication or psychosis.  Stories circulate of asthmatics who die sedated and restrained in the “quiet room.”

Somnolence is worse.  I once took a phone call from a family member who reassured me, “Grandpa’s lungs were acting up, but he’s feeling better, resting quietly now.” [R.I.P.].

Pulse oximetry only identifies severe distress.  An O2 saturation ≤89% is bad, close to an arterial blood gas pO2 of 60mmHg, but higher values hardly help.  Those of 90% – 94% are equivocal.  Over 95% will only lull a false security if a patient is retracting.  Never trust a number.

When a patient appears in obvious respiratory distress, sort quickly through the differential:




  • Asthma / COPD Exacerbation
  • Pulmonary Embolism
  • Pneumonia
  • Pneumothorax
  • Guillain-Barré (& other neurological causes)
  • Poisons (CO, etc.)
Upper Airway

  • Anaphylaxis
  • Angioedema
  • Tracheal Foreign Body / Obstruction
  • Infections in Deep Mouth/Throat
  • Tracheal Trauma

  • Poisoning
  • Acidosis
  • Sepsis
  • Acute Chest Syndrome (sickle cell)
  • Numerous causes

Red = Common         Blue = Uncommon, but “Not-To-Miss”

Obviously, none of these should be missed.  But in an out-of-hospital primary care setting, especially if transport to an E.D. may be delayed, the highlighted entities are common enough & have clear stabilizing treatments available.  This Blog doesn’t discuss treatment, but will touch on it here, because it’s intimately connected with diagnosis.  Make a working diagnosis based on treatment options.

A patient appears in severe respiratory distress, you call 911, give oxygen, & assess.  Get whatever history you can, look at their age, check vital signs, & listen to the lungs.

I won’t discuss intubation.  If you’re experienced in knowing when & how to do so, you’re already fine.  If not, don’t try.  Ventilate with bag & mask if it comes to that.

Suppose you can’t get a good history for whatever reason, like the patient can hardly breathe or concentrate, and no significant others are around.  Base treatment decisions on a lung exam & vital signs:

  • Bilateral wheezes, or rhonchi, or just a long expiratory phase, suggest asthma / COPD.  Give a nebulized β-2 agonist.  [might also be anaphylaxis; see below].
  • Bibasilar rales (inspiratory crackles) suggest acute heart failureFurosemide IV can buy time.  If history or EKG suggest acute MI, give ASA 325 mg.
  • Stridor denotes an upper airway problem.  DON’T check the throat if fever & drooling suggest possible epiglottitis.  Think anaphylaxis: give IM epinephrine, 0.3 – 0.5 mg of 1:1,000 solution (Peds: 0.01 mg/kg; 1 mg = 1 ml here; EpiPen = 0.3 mg) if patient meets criteria described below.
    • Stridor in a restaurant generates an imminent Heimlich maneuver.  Maybe for a young child as well.
  • Focal rales suggest pneumonia, especially if febrile.
  • Unilateral absence of breath sounds is a pleural effusion or pneumonia if dull to percussion, a pneumothorax if hyperresonant.
  • Clear Lungs can be anything.
  • The younger the patient, the more likely it’s asthmatreat as such.
  • The older the patient, bronchospasm vs. heart failure may be a tough call.

Don’t confuse wheezing & rhonchi with stridor: the former are lower airway, stridor is tracheal & above.  Stridor is a high pitched sound during inspiration, heard best over the trachea or upper sternal borders, with a typically normal long inspiratory phase of respiration.  Wheezes are long, usually high-pitched, expiratory sounds, with expiratory phase longer than inspiration.  Rhonchi are any squeaks or gurgles, inspiratory or expiratory, with a long expiratory phase as well.

Rales, as noted above, are inspiratory crackles.

Sure, there’s “cardiac asthma,” i.e. classic wheezes actually due to CHF.  I’ve also seen bibasilar rales clear with Albuterol.  But this is rare.  If a patient is in severe distress, play the odds.

PEARL:  Sometimes in Asthma or COPD, lungs sound clear on auscultation, but the expiratory phase is longer than inspiratory (the reverse of a normal lung exam).  If you hear this abnormality, you’ve diagnosed bronchospasm, even without a wheeze.  This is crucial in the patient with diminished breath sounds.

Vital signs will suggest Sepsis or Shock, capillary filling will be very slow.  These patients need an IV, Normal Saline wide open (but NOT  if shock may be cardiogenic).  Distinguishing types of Shock:

  • Hypovolemic: Tachycardia, Obvious source of blood or fluid loss.
  • Septic:  Fever, Tachycardia.
  • Anaphylactic:  Tachycardia, Appropriate history of Allergen
  • Cardiogenic:  Bradycardia (heart block) or Tachyarrhythmia. Older age, no history for other cause of shock.  Maybe Chest Pain.

If you’re able to obtain a history, when a patient appears in extremis, be sure to get an AMPLE one:

A – Allergies
M – Medications
P – Past Medical History
L – Last Meal (if may need surgery)
E – Events (i.e. History of Present Illness)

Probably start with the latter, because when someone’s gasping for breath & dying, it’s a little strange to start at the top.  Still, don’t get too bogged down that the patient goes out on you before you’ve found what meds they’re on, & what they’re allergic to.

Assuming you’re able to get a history & perform additional physical exam on our patient with extreme dyspnea, focus on the key entities in the differential.  Ask about past diagnoses.  Seek additional findings:

**  Myocardial Infarction:  Seek 2 subsets of info (see “Chest Pain – 1”):

  • Symptoms: chest pain or pressure (or similar discomfort in the left shoulder, upper arm, or jaw), nausea/vomiting, diaphoresis, lightheadedness.
  • Risk Factors: man >40 / post-menopausal woman, diabetes, hypertension, smoking, hyperlipidemia, same-day cocaine/amphetamine use, Hx of exertional chest pain.

**  Heart Failure:

  • Inquire about recent chest pain / pressure and other Sx suggestive of M.I.
  • Signs — Bibasilar rales, jugular venous distention, hepatojugular reflux, arrhythmias, S3 or S4 gallops, significant murmurs of valvular disease, pedal edema.

**  Asthma: Ask re past Hx of recurrent cough & SOB, episodes frequent or prolonged.  Anybody who’s had “bronchitis” several times a year undoubtedly really has asthma.

**  Foreign Body Aspiration:  Did symptoms start abruptly while eating (especially in a child or elder)?  Did symptoms start abruptly in a young child?

**  Anaphylaxis — An easily-missed preventable death.  In the context of acute-onset SOB (minutes to 2-3 hours), maybe stridor or wheezes, make the diagnosis if EITHER:

  • generalized itching, hives, flushing; OR swollen lips, tongue, uvula
  • history of exposure to a likely allergen; PLUS either persistent vomiting/abdominal cramps, or hypotension

Anaphylaxis can cause either upper airway obstruction (with stridor), bronchospasm (with wheezing), or shock.

Common culprit allergens: medications, bees, nuts, or shellfish (also eggs, soy in children).

If you diagnosis anaphylaxis, give IM epinephrine as noted above.  NEVER delay.  [Note that we’re discussing anaphylaxis in the context of acute SOB.  For patients who present in no distress, with only urticaria, an antihistamine alone is completely appropriate.]

A student related how she got anaphylactic when stung in an elevator.  A man inside, sensing her distress but unsure what to do, instinctively reached out to touch.  The student, furious at being touched by a strange male in an elevator, had an endogenous surge of epinephrine, & her reaction cleared.  So if you see anaphylaxis in the field, do something frightfully outrageous [though maybe explain briefly to a bystander first].

Next time we’ll begin to discuss the patient with recent onset SOB who’s not in immediate distress (see posting Acute Dyspnea – 2).

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