NBRC TMC Mnemonics: 12 Memory Tricks for the CRT Exam

Adventitious breath sounds

“Wheeze narrows, Crackles pop, Rhonchi rumble, Stridor's up top”

1. WWheeze: continuous, high-pitched; narrowed lower airways (bronchospasm, also 'cardiac asthma' in heart failure)
2. CCrackles: discontinuous; fine = collapsed alveoli popping open (atelectasis, fibrosis, pulmonary edema), coarse = secretions in larger airways
3. RRhonchi: low-pitched, rumbling; secretions in large airways, often change or clear after a cough
4. SStridor: loud, mostly inspiratory; upper-airway narrowing (post-extubation edema, croup, epiglottitis, foreign body)

Use it when: When a stem gives you a breath sound and asks for the cause, the next treatment (bronchodilator, suction, diuretic, racemic epinephrine) or the next test.

Careful: Stridor is an emergency sign, not a wheeze variant: after extubation it calls for cool aerosol or racemic epinephrine and readiness to reintubate. A wheeze on one side only suggests a foreign body or tumor, not asthma, and diminished sounds on one side after intubation mean a mainstem intubation or pneumothorax.

Obstructive vs restrictive PFT patterns

“Obstructed: air can't get OUT. Restricted: there's no ROOM.”

Obstructive (asthma, COPD, CF, bronchiectasis): FEV1/FVC ratio is low, TLC is normal or high, RV and FRC are high from air trapping. Restrictive (fibrosis, obesity, neuromuscular disease, chest-wall deformity): TLC is low, FVC is low, and the FEV1/FVC ratio is normal or high. DLCO then splits the groups: low in emphysema and interstitial lung disease, normal in asthma and in restriction caused by chest wall or muscles.

Use it when: When a PFT table asks you to name the pattern, recommend lung volumes or DLCO, or decide whether a bronchodilator study is worth doing.

Careful: A low FVC alone cannot prove restriction, because air trapping lowers FVC in obstruction too; only a low TLC confirms it. The bronchodilator-response rule changed: the 2022 ERS/ATS standard uses a change of more than 10% of the predicted FEV1 or FVC, while many prep books still teach the 2005 rule of 12% and 200 mL.

Trachea shift, percussion and fremitus

“Air and fluid PUSH, collapse PULLS”

1. PushTrachea shifts AWAY from a tension pneumothorax or a large pleural effusion
2. PullTrachea shifts TOWARD lobar atelectasis, pneumonectomy or upper-lobe fibrosis
3. DrumHyperresonant percussion = air: pneumothorax, emphysema, hyperinflation
4. DullDull percussion = something solid or wet: consolidation, effusion, atelectasis

Use it when: When a stem combines chest-wall findings (percussion note, tracheal position, tactile fremitus, chest film) and asks which condition fits or what to do next.

Careful: Fremitus separates the dull conditions: it is increased over consolidation (sound carries through solid lung) but decreased over an effusion or a pneumothorax. A tension pneumothorax with hypotension is treated by decompression before any film is ordered.

Sputum clues

“Pink froth floods, rust is pneumococcus, currant jelly is Klebsiella, foul is anaerobes”

1. PinkPink, frothy: pulmonary edema
2. RustRusty: pneumococcal (Streptococcus pneumoniae) pneumonia
3. JellyRed currant jelly: Klebsiella pneumonia
4. FoulFoul-smelling: anaerobic infection, lung abscess or bronchiectasis

Use it when: When the chart or the patient's history describes sputum and the item asks for the likely cause or the right test (culture and sensitivity, Gram stain).

Careful: Yellow or green color means pus (neutrophils and their enzymes), not a specific organism, so green sputum alone does not prove Pseudomonas. Frank blood (hemoptysis) needs its own workup: TB, cancer, pulmonary embolism or bronchiectasis.

Low-flow oxygen devices

“Cannula: 21 plus 4 per liter, stop at 6. Mask: never under 5. Non-rebreather: keep the bag full.”

Nasal cannula 1-6 L/min gives roughly 24-44% (about 4% added per liter). Simple mask 5-10 L/min gives roughly 35-50%; at least 5 L/min is needed to wash exhaled CO2 out of the mask. Partial rebreather and non-rebreather run at about 10-15 L/min, enough that the reservoir bag does not collapse on inspiration; a non-rebreather typically delivers about 60-80%.

Use it when: When the item asks which device or flow gives a target FiO2, or why a patient is not getting the expected oxygen.

Careful: These are low-flow devices, so the delivered FiO2 changes with the patient's breathing pattern: a tachypneic patient gets less than the table says. A reservoir bag that collapses during inspiration means the flow is too low; increase it. Patients who need a precise FiO2 need a high-flow system.

Air-entrainment ratios (magic box)

“Magic box: 100 minus FiO2 is air, FiO2 minus 20 is oxygen”

Write 20 top-left, 100 bottom-left and the desired FiO2 in the middle, then subtract across the diagonals. Top right = 100 - FiO2 = parts of air; bottom right = FiO2 - 20 = parts of oxygen. Example at 40%: 60:20, reduced to 3:1. Total flow = oxygen flow x (air parts + oxygen parts), so 10 L/min at 3:1 gives 40 L/min.

Use it when: When the item asks for an air-to-oxygen ratio, the total flow from an air-entrainment mask or nebulizer, or whether the device can meet the patient's inspiratory demand.

Careful: The box gives approximate ratios: 35% works out to about 4.6:1 but charts list 5:1, so pick the closest option. As FiO2 rises the ratio shrinks and total flow falls, so at 50% and above a single entrainment device often cannot meet a distressed patient's demand. Water in the tubing or a downstream block reduces entrainment, so the FiO2 rises while total flow drops.

Chest drainage system

“Tidaling means the Tube is open; bubbling in the water seal means a Break (leak)”

Water-seal chamber: the level should rise and fall with breathing (tidaling; on spontaneous breathing it rises on inspiration, and the pattern reverses on positive-pressure ventilation). Continuous bubbling there means an air leak, from the patient or the system. Intermittent bubbling on exhalation or cough is expected while a pneumothorax is still draining. No tidaling means either the lung has re-expanded or the tube is kinked or clotted. In a wet suction-control chamber, gentle continuous bubbling is normal.

Use it when: When the item describes what a chest drain is doing and asks for the cause or the fix: a new leak, a blocked tube, or a normal finding.

Careful: Do not clamp a chest tube to transport or to 'fix' bubbling: clamping a tube that is still evacuating air can produce a tension pneumothorax. Vigorous bubbling in the suction-control chamber does not add suction; it just evaporates water. Dry-suction systems use a regulator dial instead of a water column.

Airborne precautions

“My Chicken Hez TB”

1. MyMeasles (rubeola)
2. ChickenChickenpox (varicella)
3. HezHerpes zoster, disseminated (or localized in an immunocompromised patient)
4. TBTuberculosis (pulmonary or laryngeal, suspected or confirmed)

Use it when: When the item asks which patient needs an airborne infection isolation (negative-pressure) room and an N95 or higher respirator, or where a nebulizer or sputum induction may be done.

Careful: Influenza, pertussis and meningococcus are droplet (surgical mask), and C. difficile is contact with soap-and-water hand-washing, not airborne. Aerosol-generating procedures on a patient with an airborne disease belong in the negative-pressure room or a booth, never on an open ward.

Respiratory drug name stems

“-terol, -tropium, -sone/-nide, -lukast, -mab”

1. -terolBeta-2 agonists: albuterol, levalbuterol (short-acting); salmeterol, formoterol, arformoterol, vilanterol, olodaterol (long-acting)
2. -tropiumAnticholinergics (antimuscarinics): ipratropium (short-acting), tiotropium (long-acting)
3. -sone/-nideInhaled corticosteroids: fluticasone, mometasone, beclomethasone, budesonide, ciclesonide
4. -lukastLeukotriene receptor antagonists: montelukast, zafirlukast
5. -mabMonoclonal antibodies for severe asthma: omalizumab, mepolizumab, benralizumab, dupilumab, tezepelumab

Use it when: When a stem names a drug and asks for its class, its role (rescue vs maintenance) or the right change to the care plan.

Careful: Not every drug follows the stem: umeclidinium, aclidinium, glycopyrrolate and revefenacin are also long-acting anticholinergics, and zileuton is a leukotriene modifier without -lukast. Salmeterol is slow in onset and never a rescue drug. A long-acting beta agonist is never used alone in asthma; it goes with an inhaled steroid.

MDI vs DPI technique

“MDI: slow and hold. DPI: fast and forceful.”

Metered-dose inhaler: shake (suspensions) and prime as labeled, use a valved holding chamber when possible, inhale slowly over 3-5 seconds, then hold the breath for up to 10 seconds. Dry-powder inhaler: no shaking and no spacer, never exhale into the device, then inhale quickly and deeply, because the patient's own inspiratory flow breaks up the powder.

Use it when: When the item asks how to teach an inhaler, why a patient's technique is failing, or which device suits a patient (child, elderly, severe distress).

Careful: A DPI needs a strong inspiratory flow (roughly 30-60 L/min depending on the device), so it is a poor choice in a severe exacerbation or for young children. Rinse and spit after any inhaled steroid to reduce thrush and hoarseness.

Order of inhaled treatments in cystic fibrosis

“Open, Thin, Clear, Treat”

1. OpenBronchodilator first (for example albuterol)
2. ThinHypertonic saline, then dornase alfa (Pulmozyme)
3. ClearAirway clearance technique (vest, PEP, autogenic drainage, huffing)
4. TreatInhaled antibiotic last, so it reaches airways that have just been cleared

Use it when: When an item asks which treatment comes first in a CF regimen, or why hypertonic saline caused bronchospasm.

Careful: Hypertonic saline and acetylcysteine can trigger bronchospasm, which is why the bronchodilator goes first. Dornase alfa must be refrigerated and protected from light, and it should not be mixed with other drugs in the same nebulizer. Timing of dornase can vary by CF center, so follow the prescribed plan when it differs.

Artificial airway suctioning

“Please Suction For Half, Not more”

1. PPreoxygenate before suctioning (adults and children)
2. SShallow suctioning first; go deep only if shallow is ineffective
3. FFifteen seconds maximum of applied suction per pass
4. HHalf: catheter occludes less than 50% of the tube lumen (less than 70% in neonates)
5. NNo routine normal saline instillation

Use it when: When the item asks how to suction an intubated or tracheostomy patient, what to change after desaturation during suctioning, or which catheter size to choose.

Careful: The 2022 AARC guideline caps suction pressure at about -200 mm Hg for adults and -120 mm Hg for neonates and children (80-100 mm Hg is the usual neonatal range), while many textbooks still teach the 2010 adult limit of 150 mm Hg. Use the lowest pressure that clears secretions. Suction only when indicated, not on a schedule.