NBRC CRT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Minute ventilation formula

Minute ventilation equals respiratory rate multiplied by tidal volume; normal adult values are roughly 5–8 L/min, and it reflects total gas moved per minute.

Predicted body weight formula

For males, 50 kg plus 2.3 kg for each inch over 60; for females, 45.5 kg plus 2.3 kg per inch over 60.

Normal arterial blood gas

pH 7.35–7.45, PaCO2 35–45 mm Hg, HCO3− 22–26 mEq/L, and PaO2 80–100 mm Hg while breathing room air at sea level.

Respiratory acidosis

A primary disorder with pH below 7.35 and PaCO2 above 45 mm Hg; causes include hypoventilation, airway obstruction, and neuromuscular weakness.

Respiratory alkalosis

A primary disorder with pH above 7.45 and PaCO2 below 35 mm Hg; causes include hyperventilation from pain, anxiety, hypoxia, or overventilation.

Metabolic acidosis

A primary disorder with pH below 7.35 and HCO3− below 22 mEq/L; compensation increases ventilation to lower PaCO2.

Winter's formula

Expected PaCO2 in metabolic acidosis equals 1.5 times serum HCO3− plus 8, with a margin of plus or minus 2 mm Hg.

P/F ratio

PaO2 divided by FiO2; a normal value exceeds 400, while values below 300 suggest impaired oxygenation and below 200 suggest severe impairment.

A-a gradient

Alveolar oxygen minus arterial oxygen; alveolar oxygen equals FiO2 times barometric pressure minus 47, minus PaCO2 divided by 0.8.

End-tidal CO2 normal

Normal end-tidal carbon dioxide is 35–45 mm Hg and approximates PaCO2 in healthy patients; a sudden decrease may indicate disconnection or low perfusion.

COPD oxygen target

For a COPD patient with chronic hypercapnia, titrate oxygen to SpO2 88–92% to reduce the risk of oxygen-induced hypercapnia.

Thorpe tube reading

Read the center of the float on an upright Thorpe-tube flowmeter; the tube must be calibrated for the gas and not obstructed downstream.

Oxygen cylinder duration

Duration in minutes equals gauge pressure in psi times cylinder factor, divided by flow in L/min; an E cylinder factor is 0.28.

Ventilator leak test

Occlude the patient Y-piece and observe the pressure; a sustained set pressure without decay indicates an intact circuit.

High-pressure alarm cause

Secretions, biting, kinked tubing, bronchospasm, or a water-filled circuit can raise airway pressure and trigger a high-pressure ventilator alarm.

Low-pressure alarm cause

Circuit disconnection, a leak, a loose humidifier, or inadequate gas supply can lower airway pressure and trigger a low-pressure ventilator alarm.

Airborne precautions

Use an N95 respirator and a negative-pressure room for tuberculosis, measles, and varicella; these pathogens remain suspended in air over long distances.

Droplet precautions

Use a surgical mask and eye protection for influenza, pertussis, and meningococcal disease; droplets travel short distances and settle quickly.

Contact precautions

Use gown and gloves and dedicate equipment for C. difficile, MRSA, and other contact-spread organisms; hand hygiene with soap and water is preferred for C. difficile.

High-level disinfection

Semicritical devices such as bronchoscopes require high-level disinfection to destroy all microorganisms except high numbers of bacterial spores.

Ethylene oxide use

Ethylene oxide sterilizes heat-sensitive equipment, but items must be aerated because residual gas is toxic and irritating.

Suction pressure adult

Typical adult suction negative pressure is −80 to −120 mm Hg; excessive pressure can damage mucosa and promote atelectasis.

Nasal cannula FiO2

At 1–6 L/min, a nasal cannula delivers approximately 24–44% oxygen; flow above 6 L/min often requires humidification.

Simple mask FiO2

A simple mask at 5–10 L/min delivers approximately 35–50% oxygen; minimum flow should be 5 L/min to clear exhaled CO2.

Venturi mask purpose

A Venturi mask uses an air-entrainment jet to deliver precise low FiO2 values, usually 24–50%, making it useful for controlled oxygen therapy.

Nonrebreather mask

At 10–15 L/min, a nonrebreather mask with a reservoir delivers approximately 80–95% oxygen; the bag must be inflated before use.

Initial ventilator settings

For most adults, start with tidal volume 6–8 mL/kg predicted body weight, rate 12–20/min, PEEP 5 cm H2O, and FiO2 to target saturation.

ARDS lung protection

Use tidal volume 4–6 mL/kg predicted body weight and keep plateau pressure at or below 30 cm H2O to reduce ventilator-induced lung injury.

RSBI

Rapid shallow breathing index equals respiratory rate divided by tidal volume in liters; a value below 105 suggests readiness for weaning.

MIP weaning threshold

A maximal inspiratory pressure more negative than −20 to −30 cm H2O suggests adequate respiratory muscle strength for weaning.

COPD oxygen titration

In COPD with chronic hypercapnia, titrate oxygen to SpO2 88–92%; avoid high-flow oxygen that may worsen CO2 retention.

HME contraindications

Avoid heat-and-moisture exchangers with thick secretions, hemoptysis, or very low tidal volumes because they can obstruct or add dead space.