Suctioning an adult ICU patient: Clinical practice - the suction catheter

Recommendations for practice





The size of the suction catheter should be less than half the internal diameter of the tracheal tube.



The total suction procedure (from insertion to removal of catheter) should take a maximum of 15 seconds with negative pressure applied continuously as the catheter is being withdrawn from the tracheal tube.



In patients considered at high risk of adverse events, trauma to, and stimulation of, the carina should be minimised to prevent complications. Therefore, the suction catheter should only be inserted down a tracheal tube until it just emerges out of the lumen of the tube .



In patients not considered at high risk of adverse events, the suction catheter may be passed until either a point of resistance is felt or a cough is stimulated, then the catheter should be withdrawn 1-2 cm prior to continuous suction.



The maximum occluded suction pressure should be limited to - 80 to 150 mmHg (20kPa) for open suction system (OSS) and closed suction system (CSS). The wall outlet should have a high pressure gauge attached.


The evidence review for these recommendations was current to December 2012. Clinicians are advised to check the literature as research may have been published that change these recommendations.

Clinical practice

The size of the suction catheter and the duration of suctioning (i.e. application of negative pressure) will directly influence the volume of secretions removed, however, there are potential adverse effects on respiratory function. In agreement with previous research, a systematic review (SR), a literature review (LR) and an interrupted time series/crossover design (ITS/XO) consistently support limiting the diameter of the suction catheter to less than 50% of the internal diameter of the tracheal tube (1-3).

Two SRs and one LR consistently found continuous suctioning on withdrawal of the catheter prevented the high initial flows that are generated with intermittent suction (1, 3, 4). Some of the research this recommendation is based on is dated and no new research has been pursued in this area. The recommendation is to apply continuous suction upon withdrawal of the catheter.

The above three reviews consistently agreed on use of a minimally invasive airway suction (MIAS) technique but again there is no new evidence in this field and some of this research pertains to neonates, not adults (1, 3, 4).

In four recent studies, including two SRs, one LR and one ITS/XO study, there continues to be limited and conflicting evidence regarding the suction pressure that should be applied during the withdrawal of the catheter (1, 3-5). A SR continues to recommend an occluded negative pressure (measured by occlusion of the suction tubing) of less than 150mmHg (approximately -200cmH2O) (1). Expert opinion is that this would require further investigation as absolute values and pressure units of measurement are inconsistent across the literature.

Practice point - Suction catheter size

Suction catheter size formula

  • (Fr) = [ETT size(mm) minus 1] then multiply by 2 (3), or
  • 3FG = 1mm diameter (1FG approx. 0.3mm diameter).

For example, for a size 8 ETT:

  • using the first formula, {8 minus 1} then multiply by 2 = 14Fr (this formula will give a slightly larger catheter size), or
  • using the second formula half the diameter of 8mm = 4mm. Then multiply this number by 3 = size 12 FG.

Pressure (units of measurement) conversions






















As consistently reported in two SRs and one LR, stimulation of the carina by the suction catheter has a number of potential adverse effects including patient distress, severe coughing and bradycardia as well as causing damage to the tracheal mucosa (1, 3, 4).

Practice point - Suction catheter insertion depth

  • For patients deemed at low risk of adverse events it was agreed at the consensus meeting that the suction catheter may be inserted to the point of resistance or until a cough is stimulated. The catheter should then be withdrawn 1-2cm prior to the application of suction to ensure it is not against the airway wall. Suction should then be held continuously as the catheter is slowly withdrawn from the airway. It may be necessary to hold the suction catheter in the same place for a period of time if a large amount of secretions are present. The consensus opinion of the group is that patient participation always be included when possible with active large inspiration and active cough when possible rather than by catheter stimulation.
  • To clear secretions from the primary and secondary bronchus into the trachea where they may be removed an intubated patient must cough or provide faster expiratory to inspiratory flow ratios.
    • It was agreed to at the consensus meeting that patients who are found to have adverse reactions to suctioning, such as those with unstable CVS, high ICP, lack of cough reflex, coagulopathy or high risk of bronchospasm (see table: Hazards/complications of suctioning) should have the stimulation of their carina avoided. This may be achieved by measuring the length of the suction catheter against the length of the ETT or tracheostomy tube and only inserting until the catheter just emerges out of the lumen of the tube. As no cough will be stimulated, the patient may be encouraged to cough to command, or suction may be combined with expiratory vibrations, VHI/MHI, assisted cough or other techniques to increase expiratory flow rates to improve suction effectiveness, limiting the number of required passes.

A recent SR and an LR consistently found that suction time should be limited to a maximum of 10-15 seconds in order to minimise the risk of hypoxia, atelectasis and trauma (1, 3). It was also recommended that suction should be performed in a continuous manner only as the suction catheter is being removed. This is also the consensus opinion of the group.

No new evidence has been found to support the recommendation in the 2007 guideline limiting the number of passes of the suction catheter to a maximum of three (6). Clinicians should reassess the need for suctioning based upon assessment of clinical signs and should continuously monitor the patients SpO2, sustained or transient physiological responses to suctioning and outcome measures (see Table: Assessment pre/during/post suction/outcome measures).

Assessment pre/during/post suction/outcome measures

Physiological variablePre-suctionDuring suctionPost-suction outcome measures
Breath soundsNil added (I)
SpO2Improved (I) *
Respiratory rateImproved (I)
Pattern of breathingImproved (I)
Sputum colourDocument
Sputum amountDocument
Sputum viscosityDocument
Palpation  (I)
Arterial blood gases (ABGs) >20mins (D) #
Ventilator parameters
Saw-tooth pattern Absent (I)
Tidal volume Increased (I)
Peak airway pressure Decreased (I)
Compliance Increased (I)
ECG rate (HR)Baseline (D)
ECG rhythmBaseline (D)
Blood pressure (BP) Baseline (D)
Mean arterial pressure (MAP)Baseline (D)
Intracranial pressureAs indicatedAs indicatedAs indicated (I)

(D) delayed improvement >10mins, (I) immediate improvement <10mins, * may be delayed in patients with impaired circulation, # ABGs are not routinely required post suctioning.

Grading of recommendation taxonomy

Grade of recommendation



Body of evidence can be trusted to guide evidence


Body of evidence can be trusted to guide practice in most situations


Body of evidence provides some support for recommendation/s but care should be taken in its application


Body of evidence is weak and recommendation must be applied with caution


Consensus was set as a median of ≥ 7

Grades A–D are based on NHMRC grades (7)


  1. (AARC) AARC. AARC Clinical Practice Guidelines.  Endotracheal suctioning of mechanically ventilated patients with artificial airways. Respiratory Care. 2010;Jun; 55(6):758-64.
  2. Vanner R, Bick E. Tracheal pressures during open suctioning. Anaesthesia. 2008;63:313-5.
  3. Pederson CM, Rosendahl-Nielsen M, Hjermind J, Egerod I. Endotracheal suctioning of the adult intubated patient - What is the evidence? Intensive and Critical Care Nursing. 2009;25:21-30.
  4. Overend TJ, Anderson CM, Brooks D, Cicutto L, Kein M, McAuslan D, et al. Updating the evidence base for suctioning adult patients: a systematic review. Canadian Respiratory Journal. 2009;16(3):e6-e17.
  5. Lasocki S, Lu Q, Sartorious A, Fouillat D, Remerand F, Rouby J. Open versus closed-circuit endotracheal suctioning in acute lung injury. Anesthesiology. 2006;Jan(104):39-47.
  6. Rolls K, Smith K, Jones P, Tuipulotu M, Butcher R, A/Prof Kent B, et al. Suctioning an Adult with a Tracheal Tube. Penrith: Intensive Care Coordination & Monitoring Unit (ICCMU) & NSW Health, 2007.
  7. NHMRC. NHMRC additional levels of evidence and grades for recommendations for developers of guidelines:PILOT PROGRAM 2005 - 2007. Australian Government; 2005.


The information on this page is general in nature and cannot reflect individual patient variation. It reflects Australian intensive care practice, which may differ from that in other countries. It is intended as a supplement to the more specific information provided by the doctors and nurses caring for your loved one. ICNSW attests to the accuracy of the information contained here but takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.