How Far to Insert Correctly Sized Suction Catheter

It is essential to avoid inserting the suction catheter too deeply to prevent trauma and discomfort, while ensuring it's inserted far enough to effectively clear secretions. Below are guidelines for how far to insert suction catheter in different suctioning situations.

1) Endotracheal Tube Suctioning

Insertion Depth: The catheter should be inserted until mild resistance is felt, which indicates it is near or just above the carina (the point where the trachea divides into the left and right bronchi). Once resistance is felt, withdraw the catheter slightly (1–2 cm) before applying suction.

Avoid forceful insertion beyond the point of resistance to prevent trauma to the bronchial walls.

2) Tracheostomy Suctioning

Insertion Depth: The catheter is typically inserted to a depth that matches the length of the tracheostomy tube. Many tracheostomy tubes have a specific depth guideline (marked in centimeters) to ensure safe suctioning. If resistance is encountered, slightly withdraw the catheter before applying suction.

Measure the catheter length against the tracheostomy tube to prevent over-insertion. For most adult patients, suctioning should not extend into the bronchi unless medically indicated.

3) Nasopharyngeal or Oropharyngeal Suctioning

Insertion Depth: For nasopharyngeal or oropharyngeal suctioning (through the nose or mouth), insert the catheter until it reaches the back of the throat. In oropharyngeal suctioning, you usually insert until the patient coughs or gags slightly.

Ensure the catheter doesn't go deeper than necessary to avoid stimulating the gag reflex excessively or causing trauma to the mucosal lining.

4) General Guidelines

Catheter Size: Ensure the catheter size is appropriate for the patient. For example, in children and infants, use smaller-sized catheters (typically measured in French gauge). The size affects how far and easily the catheter can be inserted. Therefore in the next section we explain how to determine suction catheter size.

How to Determine Suction Catheter Size

Suction Catheter Size

Let’s first understand the term “suction catheter size”. “suction catheter size” refers to suction catheter diameter, measured in French gauge (Fr).

The suction catheter diameter is typically measured in French gauge (Fr). The French gauge system is used to specify the catheter's outer diameter, where one French gauge unit is equal to 1/3 mm in diameter.

A. French Gauge to Diameter Conversion

1 Fr = 1/3 mm in diameter

Diameter (mm) = French gauge (Fr) ÷ 3

B. Example Conversions

8 Fr = 8 ÷ 3 = 2.67 mm

12 Fr = 12 ÷ 3 = 4 mm

14 Fr = 14 ÷ 3 = 4.67 mm

C. Common Suction Catheter Sizes and Their Diameters

1) Small Sizes (e.g., for neonates and infants)

5 Fr: Diameter of approximately 1.67 mm (using formula: Diameter (mm) = French gauge (Fr) ÷ 3. Same formula is used in below calculations.)

6 Fr: Diameter of approximately 2 mm

8 Fr: Diameter of approximately 2.67 mm

2) Medium Sizes (e.g., for children):

10 Fr: Diameter of approximately 3.33 mm

12 Fr: Diameter of approximately 4 mm

3) Larger Sizes (e.g., for adults):

14 Fr: Diameter of approximately 4.67 mm

16 Fr: Diameter of approximately 5.33 mm

D. Choosing the Appropriate Diameter

Neonates and Infants: Smaller diameters (5–8 Fr) are used to avoid trauma to delicate airways.

Children: Medium diameters (8–10 Fr) are suitable for their larger airways but still require gentle suctioning.

Adults: Larger diameters (10–16 Fr) are often used for effective suctioning of thicker secretions.

How to Determine Suction Catheter Size Correctly

Suction catheter sizes are typically measured in French Gauge (Fr), where a larger number indicates a wider catheter diameter. In the passages below we discuss how to determine the correct size.

1) Endotracheal or Tracheostomy Tube Suctioning

To determine the size of the suction catheter for a patient with an endotracheal tube (ETT) or tracheostomy tube, a common rule is that the catheter's outer diameter should be less than half the inner diameter of the tube. This prevents the catheter from completely blocking the airway during suctioning, allowing airflow and oxygenation.

2) Age-Based Suction Catheter Sizing

In pediatric and neonatal patients, suction catheter size is often determined based on age or weight, as smaller catheters are required to prevent trauma to the delicate airways.

A. Neonates: 5–6 Fr

B. Infants: 6–8 Fr

C. Children: 8–10 Fr

D. Adults: 12–16 Fr

In general, Smaller patients (neonates and infants) require catheters between 5–8 Fr; Larger pediatric patients and adults typically require catheters between 10–16 Fr.

3) Clinical Context and Secretion Type

The thickness and volume of secretions also play a role in catheter size selection.

A. Thick Secretions: Larger catheters (12–16 Fr) may be needed to clear thicker or more viscous secretions.

B. Thin Secretions: Smaller catheters (6–10 Fr) are generally effective for thinner secretions.

4) Closed Suction Systems

When using a closed suction catheter (in-line suctioning) with a ventilator, catheter size should still be based on the endotracheal tube’s inner diameter, using the same formula. Closed systems often come in predetermined sizes (e.g., 10 Fr or 12 Fr), which match standard ETT sizes.

5) General Guidelines for Catheter Selection

A. Adults (General Use): 12–16 Fr

B. Children (Pediatrics): 8–10 Fr

C. Infants: 6–8 Fr

D. Neonates: 5–6 Fr