FREE CRT Study Guide 2026: Earn the NBRC Credential

This free CRT study guide is built around the credential itself: how you earn the NBRC Certified Respiratory Therapist credential, and the clinical content that earning it certifies.^[1]

The CRT is awarded by passing one exam — the Therapist Multiple-Choice (TMC) Examination — at the low cut score. The same exam, scored against a higher cut, plus a second simulation exam, is the path to the advanced RRT. This guide makes that CRT-vs-RRT decision clear, then walks the highest-yield clinical content.

It is interactive, not a wall of text: worked clinical scenarios, comparison tables, labeled diagrams, and built-in flashcards. Round out your prep with our CRT practice questions and flashcards.

CRT Credential Snapshot

Initiation and Modification of Interventions is by far the largest content area — about 70 of the 140 scored items (half the exam), followed by Patient Data Evaluation (~50) and Troubleshooting and Quality Control (~20). Weight your study toward interventions — ventilation, airways, oxygen therapy, and pharmacology — while keeping blood-gas interpretation sharp, because it threads through the whole exam.^[2]

The CRT Credential Path (CRT vs RRT)

This is the part candidates most often get confused about, so make it second nature. There is one multiple-choice exam — the TMC — scored against two cut scores.^[1][2]

Clearing the low cut earns the CRT. Clearing the high cut earns the CRT and also makes you eligible to sit the Clinical Simulation Examination (CSE); passing the CSE earns the RRT. So the CRT is one exam, and the RRT is two.

Why does the distinction matter for your study plan? If your goal is the CRT, you are preparing for a single multiple-choice exam and aiming to clear the low cut comfortably.

If your goal is the RRT, you must clear the higher cut on the same multiple-choice content — so you need a larger margin — and then prepare separately for the scenario-based CSE.^[3] Either way, the clinical content in this guide is exactly what the multiple-choice exam tests.

Blood Gases & Acid–Base

Arterial blood gas interpretation lives in Patient Data Evaluation and is one of the most testable skills the CRT certifies.^[4] If you can read a gas quickly and correctly, you bank points across every section.

The 5-Step ABG Method

Interpret every gas in the same order. First the pH: below 7.35 is acidemia, above 7.45 is alkalemia. Then the PaCO2 (normal 35–45 mm Hg) and the HCO3 (normal 22–26 mEq/L).

Whichever value moves the same way as the pH disturbance is the primary cause — a respiratory problem if it is the PaCO2, a metabolic problem if it is the HCO3. Finally, check whether the other system has shifted to compensate.^[4]

Disorders, Compensation & the Anion Gap

There are four primary disorders:

• Respiratory acidosis (low pH, high PaCO2) comes from hypoventilation.
• Respiratory alkalosis (high pH, low PaCO2) from hyperventilation.
• Metabolic acidosis (low pH, low HCO3) from ketoacidosis, lactic acidosis, or renal failure.
• Metabolic alkalosis (high pH, high HCO3) from vomiting, diuretics, or NG suction.

Compensation tells you timing: a near-normal HCO3 with a high PaCO2 is acute; a high HCO3 that pulls the pH back toward normal is a chronic, compensated respiratory acidosis (the COPD baseline).

For a metabolic acidosis, the anion gap — sodium minus chloride plus bicarbonate — separates high-gap (ketoacids, lactate) from normal-gap causes, and Winter's formula (expected PaCO2 ≈ 1.5 × HCO3 + 8) checks whether the lungs are compensating appropriately.

Oxygenation & Hemoximetry

Still in Patient Data Evaluation, this module covers how you measure oxygenation at the bedside — the calculations, the co-oximetry pitfalls, and the capnogram.^[4]

P/F Ratio & A–a Gradient

The P/F ratio (PaO2 ÷ FiO2 as a decimal) grades oxygenation and ARDS severity: under the Berlin definition (with PEEP ≥ 5 cm H2O), 200–300 is mild, 100–200 is moderate, and 100 or below is severe.^[5] For example, a PaO2 of 60 on an FiO2 of 0.60 gives a P/F of 100.

The A–a gradient (alveolar PO2 minus arterial PaO2) tells you why a patient is hypoxemic: a normal gradient with hypoxemia means pure hypoventilation (a CO2 problem), while a widened gradient means a gas-exchange problem — V/Q mismatch, shunt, or impaired diffusion. The gradient also widens modestly with age.

CO-Oximetry, Pulse Ox & Capnography

Standard pulse oximetry cannot detect carboxyhemoglobin (carbon-monoxide poisoning reads a falsely normal SpO2 — suspect it after a fire) or methemoglobin (SpO2 stuck near 85% with cyanosis that does not improve on oxygen) — CO-oximetry is required for both. Capnography measures exhaled CO2: a normal square waveform after intubation confirms the tube is in the trachea, and a sudden rise during CPR signals return of spontaneous circulation.

Pulmonary Diagnostics

The last part of Patient Data Evaluation: reading pulmonary function tests and the lung volumes that classify a respiratory disorder.^[7]

Obstructive vs Restrictive Patterns

The FEV1/FVC ratio is the first fork: a value below about 0.70 with a reduced FEV1 is an obstructive pattern (asthma or COPD); a normal or high ratio with reduced volumes points to a restrictive process. Asthma obstruction is reversible (FEV1 improves ≥12% and ≥200 mL after a bronchodilator); COPD obstruction is fixed.^[7] A small post-bronchodilator change (for example, 1.50 L to 1.62 L) is not a significant response.

Lung Volumes & DLCO

Lung volumes confirm the pattern. An obstructive process shows a reduced FEV1/FVC ratio with a normal or increased total lung capacity from air trapping (an elevated residual volume); a restrictive process shows a reduced total lung capacity. The diffusing capacity (DLCO) adds the gas-transfer picture: it is reduced when the alveolar–capillary surface is lost — emphysema (wall destruction), interstitial disease, or pulmonary vascular disease — and is typically normal or high in asthma, which helps separate the two obstructive diseases.^[7]

Devices, Cylinders & Flowmeters

This module opens Troubleshooting and Quality Control — the smallest content area (~20 items) but full of fast, recognizable points about equipment and the calculations the CRT must do at the bedside.^[2]

Oxygen Delivery Devices

The key split is low-flow vs high-flow. A low-flow device (nasal cannula, simple mask, nonrebreather) supplies less than the patient's total inspiratory demand, so the actual FiO2 varies with the breathing pattern — a tachypneic patient entrains more room air and gets a lower effective FiO2.

A high-flow device (air-entrainment/Venturi mask, high-flow nasal cannula) delivers a total flow that meets or exceeds demand and so gives a fixed, predictable FiO2.^[11] On a Venturi mask, raising the set FiO2 lowers total flow because less room air is entrained, which can leave a high-demand patient short of flow.

Cylinder Duration & Flowmeters

A CRT must know how long an oxygen cylinder will last. Multiply the cylinder factor by the gauge pressure (psig), then divide by the flow (L/min): the H-cylinder factor is about 3.14 and the E-cylinder factor about 0.28. An H-cylinder at 2200 psig running 8 L/min lasts (3.14 × 2200) ÷ 8 ≈ 860 minutes; an E-cylinder at 1200 psig running 5 L/min lasts (0.28 × 1200) ÷ 5 ≈ 67 minutes.

Always change a cylinder at a safe residual of about 200–500 psig. For flowmeters, use a back-pressure-compensated Thorpe tube (float downstream of the needle valve) so a downstream restriction does not falsely lower the reading, and remember that Bourdon-gauge flowmeters are position-independent for transport.

Infection Control & QC

The rest of Troubleshooting and Quality Control: keeping equipment and patients safe and keeping the blood gas analyzer trustworthy — high-yield for therapists, who perform many aerosol-generating procedures.^[10]

Spaulding & Isolation Precautions

The Spaulding classification sets the required level of reprocessing by infection risk:

• Critical items enter sterile tissue or the bloodstream and must be sterilized.
• Semicritical items contact mucous membranes (a reusable laryngoscope blade) and require at least high-level disinfection.
• Noncritical items touch only intact skin and need low- or intermediate-level disinfection.^[10]

For isolation, match the precaution to the route of spread: airborne precautions (negative-pressure room, fit-tested N95) for tuberculosis, measles, varicella;^[9] droplet (surgical mask) for influenza and pertussis; contact (gown and gloves) for MRSA and C. difficile. When donning PPE for an aerosol-generating treatment, the order is gown, respirator, eye protection, gloves.

Analyzer Quality Control

A blood gas analyzer is calibrated at two precise points to set both the offset and the slope of each electrode, then verified daily with controls plotted on a Levey–Jennings chart. Westgard rules flag a shift (an abrupt jump to one side of the mean, as from a new reagent lot) versus a trend (a gradual drift, as from an aging electrode). An out-of-range control means you hold patient results, correct the analyzer, and repeat the control before reporting — and remember that precise but not accurate describes results that are tightly grouped but off the true value.

Airway Management

Now into Initiation and Modification of Interventions — the largest content area and the heart of the exam. Airway management is the foundation: establishing, protecting, and maintaining a patent airway.^[11]

Airway Adjuncts

Match the adjunct to the patient. An oropharyngeal airway holds the tongue forward in a deeply unresponsive patient and can act as a bite block, but it provokes gagging in anyone with an intact gag reflex — too long it pushes the epiglottis down and worsens obstruction, too short it fails to hold the tongue forward. A nasopharyngeal airway is better tolerated by a conscious or semiconscious patient and gives a conduit for nasotracheal suctioning; advanced too far it stimulates the larynx and causes gagging.

ET Tubes, Cuffs & Placement

Keep ET cuff pressure at 20–30 cm H2O — high enough to seal, low enough to avoid tracheal mucosal ischemia (a measured 38 means you remove air; a measured 16 means you add air). Confirm placement after intubation with capnography (a sustained square waveform), equal bilateral breath sounds with an absent epigastric sound, and a chest film showing the tip about 2–6 cm above the carina.

During cardiac arrest a colorimetric CO2 detector may read low despite correct placement because poor pulmonary blood flow limits CO2 delivery — progressive gastric distension with no CO2 waveform instead suggests esophageal intubation.

Ventilation & Noninvasive Support

Mechanical and noninvasive ventilation are the single highest-yield topics in Interventions — modes, PEEP, alarms, CPAP vs BiPAP, and weaning all live here.^[6]

Modes, PEEP & Alarms

Know the core modes.

• In assist-control (A/C), every breath is delivered at the full set tidal volume or pressure, giving the most support — the mode for a heavily sedated or paralyzed patient with no drive.
• In SIMV, mandatory breaths are synchronized with the patient's efforts and spontaneous breaths in between get only what the patient generates (often plus pressure support).
• In pressure support, the patient triggers every breath and a set inspiratory pressure augments it.

PEEP keeps alveoli open to improve oxygenation so the FiO2 can be lowered, but raising it too far drops cardiac output (a falling blood pressure right after a PEEP increase) and risks barotrauma. For alarms, high pressure means obstruction or stiffness (secretions, kink, bronchospasm, falling compliance, pneumothorax) and low pressure means a leak or disconnection.

CPAP, BiPAP & Weaning

CPAP delivers one continuous pressure throughout the breath — it splints open alveoli and the upper airway (great for cardiogenic pulmonary edema and obstructive sleep apnea) but does not actively assist ventilation. Bilevel (BiPAP) sets a higher inspiratory (IPAP) and lower expiratory (EPAP) pressure: the IPAP–EPAP difference is pressure support, so widening it lowers a high PaCO2, while raising EPAP improves oxygenation like PEEP.

Wean with a spontaneous breathing trial when the patient is stable, oxygenating on minimal support, and showing a favorable rapid shallow breathing index — but extubation also requires that the patient can protect the airway with an intact gag and cough.

Pharmacology & Airway Clearance

The rest of Interventions: the drugs you deliver and the techniques that clear secretions and re-expand lung — high-yield because therapists administer them directly.^[8]

Respiratory Pharmacology

Albuterol is a short-acting beta-2 agonist that relaxes bronchial smooth muscle quickly — first-line for acute bronchospasm; levalbuterol is an option when racemic albuterol causes marked tachycardia. Ipratropium is a short-acting anticholinergic often combined with albuterol, and tiotropium is its long-acting cousin for COPD maintenance.

Racemic epinephrine constricts mucosal vessels to shrink upper-airway swelling — croup and post-extubation stridor. Dornase alfa cleaves the DNA-rich sputum of cystic fibrosis (give a bronchodilator first), while heliox lowers gas density to cut the work of breathing through severely narrowed airways.^[8]

Airway Clearance & Lung Expansion

Postural drainage positions the affected segment uppermost so gravity drains secretions; avoid head-down positions when intracranial pressure is raised. PEP therapy and oscillatory devices (flutter, Acapella) splint airways open and mobilize mucus, and the oscillation vest suits patients who cannot tolerate manual chest physiotherapy. For lung expansion, incentive spirometry has an alert, cooperative patient take slow, sustained deep breaths (high-yield after upper-abdominal or thoracic surgery), while IPPB is reserved for patients who cannot take an adequate deep breath on their own.^[11]

How to Use This Study Guide

Work through the guide one module at a time. After each one, check it off in the contents to raise your exam-readiness score, then drill the same content in our free practice questions and flashcards — active recall and timed practice are what move knowledge into exam-day performance.

• Decide CRT or RRT first. It is one exam; for the CRT clear the low cut comfortably, for the RRT build a bigger margin and prepare separately for the CSE.
• Weight your time by the blueprint. Interventions is half the exam — ventilation, airways, oxygen therapy, and drugs come first.
• Make ABG interpretation automatic. Blood gases thread through every section; the 5-step method, the anion gap, and Winter's formula should be reflexive.
• Drill the calculations. P/F ratio, anion gap, Winter's formula, auto-PEEP, dynamic compliance, and cylinder duration show up repeatedly — practice them until they're fast.
• Learn the alarm and device rules. High vs low pressure, low-flow vs high-flow, the cuff-pressure window, and CPAP vs BiPAP are quick, reliable points.
• Then prove it. When a module feels solid, confirm with our practice questions — and pair this with our TMC Exam study guide for the same content from the exam-mechanics angle.

Common clinical concepts the CRT credential certifies — each answered briefly and backed by an official source (NBRC, NHLBI/NIH, CDC, ARDSnet, or AARC). Tap any card to test yourself.

CRT Glossary

Key CRT credential and clinical terms in one place. Hover any dotted term throughout the guide for its definition; the full list is below.

CRT

Certified Respiratory Therapist — the NBRC's entry-level respiratory-care credential, earned by passing the Therapist Multiple-Choice (TMC) Examination at the low cut score; many states require it for licensure.

RRT

Registered Respiratory Therapist — the NBRC's advanced credential, earned by passing the TMC at the high cut score and then passing the Clinical Simulation Examination (CSE).

NBRC

The National Board for Respiratory Care — the body that develops and administers the TMC Exam, the Clinical Simulation Examination, and the CRT and RRT credentials.

TMC Exam

The Therapist Multiple-Choice Examination — the single multiple-choice exam that earns the CRT at its low cut score and unlocks CSE eligibility (toward the RRT) at its high cut score.

CSE

Clinical Simulation Examination — the NBRC's scenario-based second exam; passing it after a high-cut TMC is required to earn the RRT credential.

cut score

The minimum number of correct scored items needed to pass; the TMC has two — a low cut score that earns the CRT and a higher cut score that adds eligibility for the CSE.

CoARC

The Commission on Accreditation for Respiratory Care — accredits the respiratory-care degree programs whose graduates are eligible to sit the NBRC's credentialing exams.

respiratory acidosis

An acid-base disorder with a low pH and a high PaCO2 caused by hypoventilation (e.g., COPD, oversedation), so carbon dioxide accumulates in the blood.

respiratory alkalosis

An acid-base disorder with a high pH and a low PaCO2 caused by hyperventilation (e.g., anxiety, pain, pulmonary embolism, hypoxia), blowing off carbon dioxide.

metabolic acidosis

An acid-base disorder with a low pH and a low HCO3, as in diabetic ketoacidosis, lactic acidosis, renal failure, or diarrhea.

metabolic alkalosis

An acid-base disorder with a high pH and a high HCO3, as from vomiting, diuretics, or nasogastric suction.

anion gap

Sodium minus the sum of chloride and bicarbonate (normally ~8–12 mEq/L); a high value signals accumulation of unmeasured acids, as in ketoacidosis or lactic acidosis.

Winter's formula

An estimate of the expected respiratory compensation for a metabolic acidosis: expected PaCO2 ≈ 1.5 × HCO3 + 8 (±2).

P/F ratio

The PaO2 divided by the FiO2 (as a decimal); under the Berlin definition it grades ARDS severity — 200–300 mild, 100–200 moderate, and 100 or below severe.

A-a gradient

The alveolar–arterial oxygen gradient, the difference between alveolar PO2 and arterial PaO2; a widened gradient indicates a gas-exchange (V/Q mismatch, shunt, diffusion) problem.

carboxyhemoglobin

Hemoglobin bound to carbon monoxide; it cannot carry oxygen and is missed by standard pulse oximetry, so CO-oximetry is needed to detect carbon-monoxide poisoning.

methemoglobin

Hemoglobin whose iron is in the ferric (Fe3+) state and cannot bind oxygen; it causes cyanosis with a pulse oximeter often reading near 85% and is detected by CO-oximetry.

capnography

Continuous measurement of exhaled carbon dioxide; a normal square waveform confirms tracheal tube placement, and a sudden rise during CPR signals return of spontaneous circulation.

DLCO

The single-breath diffusing capacity for carbon monoxide — how readily gas crosses the alveolar–capillary membrane; reduced in emphysema, interstitial, and pulmonary vascular disease.

FEV1/FVC ratio

The fraction of forced vital capacity exhaled in the first second; below about 0.70 defines an obstructive pattern (asthma or COPD).

auto-PEEP

Intrinsic PEEP — gas trapped in the alveoli when exhalation is incomplete before the next breath (common in COPD/asthma); detected with an expiratory-hold maneuver.

PEEP

Positive end-expiratory pressure — pressure held in the lungs at the end of exhalation to keep alveoli open and improve oxygenation.

plateau pressure

The ventilator pressure measured during an inspiratory hold (no flow); it reflects lung compliance and is kept below 30 cm H2O to limit ventilator-induced lung injury.

ET cuff pressure

The pressure in an endotracheal tube cuff, kept at 20–30 cm H2O — high enough to seal but low enough to avoid tracheal mucosal ischemia.

CPAP

Continuous positive airway pressure — one constant pressure throughout the breath; splints open alveoli and the upper airway (cardiogenic edema, sleep apnea) without actively assisting ventilation.

BiPAP

Bilevel positive airway pressure — a higher inspiratory (IPAP) and lower expiratory (EPAP) pressure; the IPAP–EPAP difference augments tidal volume to lower a high PaCO2.

Spaulding classification

A system that sorts devices by infection risk — critical (sterilize), semicritical (high-level disinfection), and noncritical (low/intermediate disinfection).

airborne precautions

Isolation for pathogens carried in small droplet nuclei (tuberculosis, measles, varicella): a negative-pressure room and a fit-tested N95 respirator.

cylinder factor

A constant (H ≈ 3.14, E ≈ 0.28) multiplied by gauge pressure and divided by flow to estimate the minutes of oxygen left in a compressed-gas cylinder.

heliox

A low-density helium–oxygen mixture that reduces turbulent flow and the work of breathing through narrowed airways in severe obstruction; benefit falls as the oxygen fraction rises.

albuterol

A short-acting beta-2 agonist that rapidly relaxes bronchial smooth muscle; first-line for acute bronchospasm such as an asthma exacerbation.

CRT Study Guide FAQ

References

1. 1.National Board for Respiratory Care (NBRC). “Certified Respiratory Therapist (CRT).” NBRC. ↑
2. 2.National Board for Respiratory Care (NBRC). “Therapist Multiple-Choice Examination — Detailed Content Outline.” NBRC. ↑
3. 3.National Board for Respiratory Care (NBRC). “Registered Respiratory Therapist (RRT).” NBRC. ↑
4. 4.National Heart, Lung, and Blood Institute (NHLBI). “Respiratory Failure.” nhlbi.nih.gov. ↑
5. 5.National Heart, Lung, and Blood Institute (NHLBI). “ARDS (Acute Respiratory Distress Syndrome).” nhlbi.nih.gov. ↑
6. 6.ARDS Network (ARDSnet) / NHLBI. “ARDSnet Ventilator Protocol.” ardsnet.org. ↑
7. 7.National Heart, Lung, and Blood Institute (NHLBI). “COPD.” nhlbi.nih.gov. ↑
8. 8.National Heart, Lung, and Blood Institute (NHLBI). “Asthma.” nhlbi.nih.gov. ↑
9. 9.Centers for Disease Control and Prevention (CDC). “Tuberculosis Infection Control in Healthcare Settings.” cdc.gov. ↑
10. 10.Centers for Disease Control and Prevention (CDC). “Isolation Precautions / Disinfection & Sterilization.” cdc.gov. ↑
11. 11.American Association for Respiratory Care (AARC). “Clinical Practice Guidelines.” aarc.org. ↑

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