A 28-year-old female patient is intubated for status asthmaticus. After 4 hours, the team notices asymmetrical breath sounds with decreased air entry on the right side. The endotracheal tube position is suspected to be malpositioned. Which investigation should be performed first to confirm right mainstem intubation?

## Investigation of Choice for Suspected Mainstem Intubation ### Clinical Scenario Asymmetrical breath sounds with unilateral decreased air entry in an intubated patient is classic for right mainstem intubation. The investigation must: - Confirm tube position relative to the carina - Be rapid and non-invasive - Be available at the bedside - Guide immediate corrective action (tube withdrawal) ### Why Portable Chest X-ray is First-Line **Key Point:** Portable chest X-ray with a radiopaque tube position marker is the standard initial investigation for suspected endotracheal tube malposition. It directly visualizes tube position relative to the carina and mainstem bronchi. **High-Yield:** Chest X-ray allows: 1. Measurement of tube tip distance from the carina (normal: 3–5 cm above carina) 2. Confirmation of right vs. left mainstem intubation 3. Identification of other complications (aspiration, pneumothorax, atelectasis) 4. Rapid bedside availability ### Diagnostic Criteria on Chest X-ray | Finding | Interpretation | |---|---| | Tube tip 3–5 cm above carina | Correct position | | Tube tip < 2 cm from carina | Risk of cuff herniation | | Tube tip in right mainstem | Right mainstem intubation (common) | | Tube tip in left mainstem | Left mainstem intubation (rare, difficult) | | Asymmetrical lung inflation | Suggests mainstem intubation | **Clinical Pearl:** Right mainstem intubation is more common than left because the right mainstem bronchus is more vertical and in line with the trachea. Asymmetrical breath sounds with right-sided decrease should prompt immediate CXR confirmation and tube withdrawal by 1–2 cm. **Mnemonic:** **TUBE** — **T**ip position, **U**nder 3 cm risk, **B**ronchus intubation, **E**xamine clinically first **Warning:** Do not rely on clinical examination alone (asymmetrical breath sounds) to diagnose mainstem intubation; some patients with right mainstem intubation may have deceptively symmetrical sounds due to transmitted breath sounds. CXR confirmation is mandatory. ### When to Proceed to FOB Fiber-optic bronchoscopy is reserved for: - Inability to obtain adequate CXR (e.g., portable film too poor quality) - Suspected tube obstruction or kinking (not just malposition) - Therapeutic intervention needed (clearing obstruction) - Confirmation after tube repositioning [cite:Benumof & Hagberg Airway Management 3e Ch 15]