CRT (CREST) flashcards

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

Normal adult respiratory rate

At rest, an adult typically breathes 12 to 20 times per minute. Rates persistently above 20 (tachypnea) or below 12 (bradypnea) indicate a need for further assessment.

Normal adult SpO2

Pulse oximetry in a healthy adult at sea level on room air is typically 94 to 100 percent. Values below 90 percent indicate hypoxemia requiring prompt evaluation.

Arterial blood gas interpretation order

Assess pH first to identify acidemia or alkalemia, then PaCO2 to determine the respiratory component, then bicarbonate to determine the metabolic component, and finally check whether compensation is appropriate.

Acute respiratory acidosis compensation

In acute respiratory acidosis, bicarbonate rises approximately 1 mEq/L for every 10 mm Hg increase in PaCO2. A larger rise suggests a chronic process or coexisting metabolic alkalosis.

Chronic respiratory acidosis compensation

In chronic respiratory acidosis, renal compensation raises bicarbonate approximately 3 to 4 mEq/L for every 10 mm Hg increase in PaCO2, reflecting renal retention of bicarbonate over days.

P/F ratio meaning

The PaO2 divided by the fraction of inspired oxygen estimates oxygenation efficiency. A ratio below 300 suggests significant impairment; below 200 indicates severe dysfunction such as ARDS.

Spirometry obstruction criterion

Obstruction is present when the FEV1/FVC ratio falls below the lower limit of normal, commonly less than 0.70. Severity is then graded using the FEV1 as a percent of predicted.

Bronchodilator reversibility criterion

Significant reversibility on spirometry is a post-bronchodilator increase in FEV1 of at least 12 percent and at least 200 mL compared with the pre-bronchodilator value.

Chest radiograph reading sequence

Review technical quality first, then airways, bones, cardiac silhouette, diaphragm, effusions, lung fields, gastric bubble, and hardware. This systematic order prevents missed findings.

Nasal cannula FiO2 range

Low-flow nasal cannula at 1 to 6 L/min delivers an approximate FiO2 of 24 to 44 percent, varying with the patient's inspiratory flow and breathing pattern.

Venturi mask function

An air-entrainment mask uses a jet and fixed orifice to mix oxygen with room air, delivering a precise, fixed FiO2, typically between 24 and 50 percent, regardless of patient effort.

High-flow nasal cannula

Heated, humidified high-flow nasal cannula delivers flows up to about 60 L/min with titratable FiO2 from 21 to 100 percent, providing some positive pressure and improving comfort and washout of dead space.

Humidification threshold

Supplemental oxygen generally requires humidification when nasal cannula flow exceeds about 4 L/min, or whenever an artificial airway bypasses the upper airway's normal warming and moistening function.

Aerosol particle size

Therapeutic aerosols are most effective when particles are roughly 1 to 5 micrometers, allowing deposition in the lower respiratory tract rather than the upper airway or device.

Lung-protective tidal volume

In volume-control ventilation, a lung-protective tidal volume is about 6 mL/kg of predicted body weight, commonly used in ARDS to limit ventilator-induced lung injury from overdistension.

Rapid shallow breathing index

The RSBI is the respiratory rate divided by tidal volume in liters. A value below 105 suggests a patient is likely to tolerate weaning from mechanical ventilation.

NIV indications

Noninvasive ventilation, such as CPAP or BiPAP, is indicated for acute hypercapnic COPD exacerbation and cardiogenic pulmonary edema. Inability to protect the airway is a contraindication.

Postural drainage principle

Postural drainage positions the patient so the affected lung segment is uppermost, allowing gravity to move secretions toward the central airways for expectoration or suctioning.

Racemic epinephrine use

Nebulized racemic epinephrine reduces mucosal edema and is used for post-extubation stridor or upper airway swelling, providing temporary relief while definitive treatment is arranged.

Tension pneumothorax action

A tension pneumothorax requires immediate needle decompression, typically at the second intercostal space midclavicular line or fifth space anterior axillary line, followed by tube thoracostomy.

Transmission-based precautions

Contact precautions apply to MRSA and C. difficile, droplet precautions to influenza and pertussis, and airborne precautions to tuberculosis, measles, and varicella, requiring N95 or higher.

Oxygen source safety distance

Keep oxygen sources away from open flames and smoking, generally at least 5 to 10 feet. Avoid oil or grease on regulators and use cotton or synthetic fabrics to reduce static.

Cylinder duration formula

Duration in minutes equals cylinder pressure in psig times the cylinder factor divided by flow in L/min. Common factors are 0.28 for E and 3.14 for H/K cylinders.

Semicritical device disinfection

Semicritical items contact intact mucous membranes, such as bronchoscopes. They require high-level disinfection, while critical items require sterilization and noncritical items need only low-level disinfection.

Blood gas analyzer QC frequency

Run two levels of control material at least every 8 hours and after electrode changes or maintenance. Verify calibration, check for clots, and document all results per laboratory policy.

Carboxyhemoglobin oximetry error

Standard pulse oximeters cannot distinguish carboxyhemoglobin from oxyhemoglobin, so readings appear falsely high in carbon monoxide poisoning. Co-oximetry is needed for accurate measurement.

High-pressure ventilator alarm

A high-pressure alarm suggests increased resistance or decreased compliance, such as secretions, biting, kinked tubing, or bronchospasm. Assess the patient first, then the circuit.

Low-pressure ventilator alarm

A low-pressure alarm usually indicates a disconnection, circuit leak, or cuff leak. Check the patient and circuit immediately, since loss of ventilation can be rapid and serious.

Two-identifier verification

Before any therapy, verify patient identity using two independent identifiers, such as name and date of birth, and confirm the order matches the intended treatment.

Critical value reporting

Critical laboratory or monitoring values, such as severe hypoxemia or dangerous hyperkalemia, must be reported promptly to the responsible clinician and documented according to protocol.

Standard precautions scope

Standard precautions apply to every patient regardless of diagnosis and include hand hygiene, gloves, gown, mask, and eye protection based on anticipated exposure to blood or body fluids.

Airborne precautions requirements

Airborne precautions are used for tuberculosis, measles, and varicella. They require a negative-pressure room and an N95 or higher respirator for all entering healthcare personnel.