How to correctly select the model of a double-lumen bronchial tube

In thoracic surgery anesthesia and intensive care, the double-lumen endotracheal tube plays a fundamental and irreplaceable role. Simply put, it is the most classic, reliable, and widely used technique for achieving one-lung ventilation and lung isolation, and is the backbone of thoracic surgical anesthesia.

I. Importance of Choosing the Right Size for a Double-Lumen Bronchial Catheter.

An oversized or thickened endotracheal tube increases the risk of postoperative hoarseness, sore throat, and airway damage, and may even cause bronchial rupture. An undersized or thinned endotracheal tube increases ventilation resistance, hinders secretion drainage, and may cause more air to be injected into the cuff, leading to compression of surrounding tissues and local mucosal damage. The tube may also shift deeper into the bronchus, with tidal volume preferentially delivered to the lower lobes, potentially causing tension pneumothorax. The appropriate size matching standard is: the outer diameter of the bronchial lumen of the double-lumen endotracheal tube should be 1-2 mm smaller than the inner diameter of the patient's left main bronchus.

II.Appropriate Selection of Double-Lumen Bronchial Tube Size.

A suitable double-lumen tube size generally requires no significant resistance during insertion, that the bronchial end correctly reaches or can be guided by a fiberoptic bronchoscope to the intended main bronchus, and that there is no air leakage when the bronchial cuff is inflated to approximately 1-3 ml and the peak airway pressure reaches 30 cmH2O during positive pressure ventilation.

If significant resistance is felt during tube insertion, or if the bronchial cuff inflation volume is less than 0.5-1 ml after accurate positioning of the double-lumen tube but no air leakage is achieved when the peak airway pressure of 30 cmH2O is reached, the tube is considered too thick.If, after positioning, the bronchial cuff inflation exceeds 3 ml (or the resting cuff volume) to achieve the peak airway pressure of 30 cmH2O without air leakage, the tube is considered too thin.

III. Methods for Selecting the Size of a Double-Lumen Bronchial Tube

1. Experienced Selection Based on Patient Gender and Height: Miller's Anesthesiology recommends selecting the size based on gender and height: For women <152cm, choose 32Fr; 152-160cm, choose 35Fr; >160cm, choose 37Fr; For men <160cm, choose 37Fr; 160-170cm, choose 39Fr; >170cm, choose 41Fr.

Asian populations are generally smaller, and in clinical practice, the more commonly used method is: For women ≤153cm, choose 32Fr; 153-165cm, choose 35Fr; >165cm, choose 37Fr; For men ≤160cm, choose 35Fr; 160-178cm, choose 37Fr; >178cm, choose 39Fr.

The outer diameter of the tubing in different models of double-lumen tubes is relatively fixed (left tube):

41F: Main tube outer diameter 14-15mm, bronchial end outer diameter 11.2mm; 39F: Main tube outer diameter 13-14mm, bronchial end outer diameter 10.7mm; 37F: Main tube outer diameter 13-14mm, bronchial end outer diameter 10.2mm; 35F: Main tube outer diameter 12-13mm, bronchial end outer diameter 9.6mm.

2. CT scan measurement of an individual's tracheal or bronchial diameter – optimal standard.

CT measurement of the left main bronchus diameter helps predict and select the correct left-side double-lumen tube model. For left main bronchus diameters <10mm, 10mm, 11mm, 12mm, and >12mm, select 32F, 35F, 37F, 39F, and 41F respectively.

The double-lumen tube model is highly correlated with the tracheal inner diameter: (F) = 27 + 0.7 x tracheal inner diameter measurement (mm). For a predicted tracheal inner diameter ≥19mm, select 41F or 45F double-lumen tube; ≥17mm, select 39F; ≥15mm, select 37F; ≥13mm, select 35F; and ≥11mm, select 30F.

3. Ultrasonic measurement of tracheal outer diameter (mm): Place the ultrasound transversely about two finger widths above the middle of the upper edge of the patient's sternal manubrium, at the trachea. Adjust the depth of field and gain of the ultrasound as needed. The measurement of the widest point of the trachea in the left-right direction (including the tracheal wall) on the ultrasound image is taken as the patient's ultrasound tracheal outer diameter.