Before performing a radial artery puncture for ABG sampling, the respiratory therapist should perform the:

Modified Allen test. The modified Allen test is performed before radial artery puncture to confirm adequate collateral circulation through the ulnar artery. If the ulnar artery is insufficient (negative Allen test — hand does not re-color within 15 seconds after releasing ulnar compression), the radial artery should not be punctured on that side.

When observing a chest drainage system, continuous air bubbles in the water seal chamber indicate:

An air leak is present in the system or from the patient. Continuous air bubbles in the water seal chamber indicate an air leak. The leak may be at the patient (ongoing pneumothorax, bronchopleural fistula) or in the drainage system (loose connections, cracked tubing). Intermittent bubbling with coughing or expiration may be normal, but continuous bubbling requires investigation.

An AHI (Apnea-Hypopnea Index) of 22 events per hour on a sleep study indicates:

Moderate obstructive sleep apnea. An AHI of 22 falls in the moderate OSA range (15-29 events per hour). AHI <5 is normal, 5-14 is mild, 15-29 is moderate, and ≥30 is severe. Moderate-to-severe OSA is typically treated with CPAP therapy, which is titrated during a follow-up sleep study to determine the optimal pressure.

For a 4-year-old child, what size UNCUFFED endotracheal tube is appropriate?

5.0 mm. The uncuffed ETT size formula is (age/4) + 4. For a 4-year-old: (4/4) + 4 = 1 + 4 = 5.0 mm. The cuffed ETT formula is (age/4) + 3.5, which would give 4.5 mm for the same child. Always have one size larger and one size smaller available.

During an ABG draw, air bubbles in the sample will cause which of the following errors?

Falsely elevated PaO2 and falsely decreased PaCO2. Air bubbles in an ABG sample equilibrate with the blood, causing room air contamination. Since room air has a higher PO2 (~150 mmHg) and lower PCO2 (~0.3 mmHg) than arterial blood, the result is a falsely elevated PaO2 and falsely decreased PaCO2. All air bubbles must be removed immediately after collection.

4.3 Specialty Procedures | CRT/RRT Respiratory Therapist Exam | Free Exam Prep

Key Takeaways

Chest tubes drain air (pneumothorax) or fluid (pleural effusion, hemothorax) from the pleural space; connected to a drainage system with a water seal
Arterial line sampling: modified Allen test first to confirm collateral ulnar circulation; use pre-heparinized syringe, remove air bubbles, transport on ice
Bronchoscopy assistance: RT manages airway and monitors SpO2/ETCO2 during the procedure; may assist with BAL and biopsy specimen collection
Sleep studies (PSG) monitor EEG, EMG, EOG, ECG, airflow, respiratory effort, SpO2, and body position to diagnose sleep disorders
CPAP titration is the primary treatment for obstructive sleep apnea (OSA); typical pressures 5-20 cmH2O
Neonatal surfactant therapy: administered via ET tube (INSURE or LISA technique); for neonatal RDS (premature infants)
High-frequency oscillatory ventilation (HFOV): delivers very small VT at very high rates (180-900 breaths/min); used in refractory neonatal/pediatric respiratory failure
Pediatric RT considerations: uncuffed ETTs traditionally used under age 8; weight-based drug dosing; Broselow tape for emergency sizing

Specialty Procedures

Respiratory therapists perform and assist with a variety of specialized procedures. The TMC exam tests your knowledge of these procedures, including indications, technique, monitoring, and complications. This section covers chest tube management, arterial sampling, bronchoscopy, sleep studies, and neonatal/pediatric considerations.

Chest Tube Management

Chest tubes (thoracostomy tubes) are placed to drain air, blood, or fluid from the pleural space.

Indications:

Pneumothorax (spontaneous, traumatic, iatrogenic)
Pleural effusion (parapneumonic, malignant)
Hemothorax (blood in the pleural space)
Empyema (pus in the pleural space)
Post-thoracic surgery drainage

Chest Drainage System Components:

Chamber	Function
Collection chamber	Collects drained fluid; measures output
Water seal chamber	Filled with 2 cm of water; acts as a one-way valve to prevent air from re-entering the pleural space
Suction control chamber	Regulates negative pressure applied; typically set at -20 cmH2O

RT Responsibilities:

Monitor drainage amount, color, and character (serous, sanguineous, purulent)
Observe the water seal for tidaling (fluctuation with respiration = normal, patent tube)
Observe for continuous air bubbles in the water seal (air leak present)
Ensure the drainage system is below the patient's chest level
Never clamp a chest tube without a physician order (risk of tension pneumothorax)
Report sudden cessation of drainage, respiratory distress, or subcutaneous emphysema

Arterial Blood Sampling (ABG Draw)

Pre-procedure — Modified Allen Test:

Performed before radial artery puncture to confirm collateral ulnar circulation
Have the patient make a fist while you compress both radial and ulnar arteries
Patient opens hand (should be blanched/pale)
Release the ulnar artery while maintaining radial compression
Positive test (normal): Hand re-colors within 5-15 seconds → safe to proceed
Negative test: Hand remains blanched → do NOT puncture the radial artery (try the other wrist or use an alternative site)

Sampling Technique:

Use a pre-heparinized ABG syringe
Puncture the radial artery at a 45-degree angle (brachial: 60 degrees; femoral: 90 degrees)
Allow arterial pressure to fill the syringe (do not aspirate forcefully)
Remove all air bubbles immediately (air contamination falsely elevates PaO2 and lowers PaCO2)
Apply firm pressure for at least 5 minutes (15+ minutes if anticoagulated)
Transport on ice if analysis will be delayed >15 minutes; otherwise analyze immediately

Bronchoscopy Assistance

During flexible bronchoscopy, the respiratory therapist provides critical support:

RT Role During Bronchoscopy:

Manage the airway (especially if patient is intubated)
Monitor SpO2, ETCO2, ECG, and vital signs continuously
Administer supplemental oxygen (typically high-flow)
Assist with lidocaine administration for topical anesthesia
Assist with specimen collection (bronchoalveolar lavage, brushings, biopsies)
Provide manual ventilation or adjust ventilator settings as needed
Post-procedure: Monitor for complications (pneumothorax, bleeding, bronchospasm)

Sleep Studies (Polysomnography — PSG)

Polysomnography monitors multiple physiological signals during sleep:

Channel	Measurement	Purpose
EEG	Brain waves	Determine sleep stage
EOG	Eye movements	Identify REM sleep
EMG	Muscle tone (chin, legs)	Detect REM atonia, leg movements
ECG	Heart rhythm	Cardiac arrhythmias
Airflow (nasal, oral)	Breathing	Detect apneas and hypopneas
Respiratory effort (thoracic, abdominal)	Chest/abdominal movement	Distinguish obstructive vs. central apneas
SpO2	Oxygen saturation	Desaturation events
Body position	Supine, lateral, prone	Positional apnea
Snoring microphone	Sound	Snoring severity

Apnea-Hypopnea Index (AHI):

AHI	OSA Severity
<5	Normal
5-14	Mild OSA
15-29	Moderate OSA
≥30	Severe OSA

Neonatal and Pediatric Considerations

Topic	Key Points
Surfactant therapy	Given via ET tube for neonatal RDS; INSURE (Intubate-Surfactant-Extubate) or LISA (Less Invasive Surfactant Administration)
Neonatal CPAP	First-line for preterm infants with RDS; bubble CPAP or ventilator CPAP
HFOV (High-Frequency Oscillatory Ventilation)	Very small VT at 180-900 breaths/min; used for refractory neonatal/pediatric failure
ETT sizing	Uncuffed: (age/4) + 4; Cuffed: (age/4) + 3.5; term neonates: 3.0-3.5 mm
Drug dosing	Weight-based (mg/kg); use Broselow tape in emergencies
Pediatric assessment triangle	Appearance, Work of Breathing, Circulation (rapid assessment tool)

CRT/RRT Respiratory Therapist Exam

1Introduction: NBRC TMC Exam Overview

2Chapter 1: Patient Data Evaluation

3Chapter 2: Airway Management & Oxygen Therapy

4Chapter 3: Mechanical Ventilation

5Chapter 4: Pharmacology & Equipment

6Chapter 5: Infection Control, Ethics & Professional Practice