When a carer hears a rattling sound of phlegm in a family member's throat, the first reaction of many is to bring out the suction machine. But having phlegm and needing suctioning are two different things, and even with phlegm, a tube in the airway is not necessarily needed. What really has to be judged is whether the patient can cough the phlegm up alone and, if not, whether assisted methods can help to clear it. Only when both fail does suctioning come last.
Put simply, phlegm does not always need suctioning. Suctioning is the last step of the airway clearance process. The patient should first try to cough voluntarily, then use cough assistance (chest percussion, breath stacking, a cough assist machine). Suctioning is done only when the secretions cannot be cleared, or when the patient has a tracheostomy or an artificial airway. The clinical guideline is very clear: suction only when secretions are present, and do not suction routinely on a timetable, to avoid mucosal injury and the risk of low oxygen (AARC 2010). In addition, the evidence for the effect of respiratory physiotherapy is mostly of low certainty, and the suctioning parameters are standards of clinical practice and not data from randomised controlled trials.
Where suctioning comes in the airway clearance process
Suctioning has never been the first-choice way to clear secretions. It is a step used only at the last point. The guideline on endotracheal suctioning is clear that suctioning should be done only when secretions are present and never routinely or on a timetable (AARC 2010). For airway clearance in patients with neuromuscular disease, the technique should also be matched to how effective the patient's cough is, rather than following the same checklist rigidly (Chatwin 2018).
Suctioning is not an everyday routine movement. This method is used as a remedy only when the patient has secretions collecting in the airway that cannot be cleared. The principle set by the clinical guideline is to suction only when secretions are present, and not to suction at every rattling sound. This is because suctioning through a tube irritates the airway, and suctioning too often does more harm than good (AARC 2010).
Three steps in deciding how to clear secretions
If airway clearance is pictured as a ladder that rises step by step from least to most invasive, the decision becomes much clearer. The care goal is always to clear the secretions in the gentlest way, as close as possible to the patient coughing alone. Only when the method on one level fails does the patient move up to the next.
The detailed steps of the first two levels of this ladder are not covered on this page. To choose a method of cough assistance and read the two PCF thresholds, see the page on cough assistance for people with neuromuscular disease. If suctioning has been shown to be needed and the patient wants to learn safe technique, see the page on safe steps for home suctioning.
Step 1: assess whether the patient can cough secretions up alone
Before moving up to suctioning, the first task is to assess the patient's own ability to clear secretions. Airway clearance techniques (such as chest percussion and the active cycle of breathing) are quite safe for patients in a stable phase and do increase the amount of sputum cleared, although the quality of evidence for some outcomes such as quality of life and lung function is low (Lee 2015). Starting with gentle methods is therefore fully supported clinically.
- Is the cough effective—First look at whether the force of the cough is enough and whether it feels as if secretions have been cleared. If the rattle is less after the patient coughs and breathing returns to normal, the patient has the ability to clear secretions alone.
- Can the patient sit up—If the patient can sit up or sit semi-reclined, gravity together with the body's effort already helps to bring secretions up. If the patient lies flat for a long time, secretions are harder to cough up.
- Is there enough fluid—Secretions are less thick when the body has enough water. Thick secretions are often due to a lack of fluid or humidification, and improving this first is more practical than rushing to suction.
Level 2, cough assistance: remember the PCF marker of below 270
A weak cough does not mean a tube must be put into the airway at once. The second level of the ladder uses chest percussion, breath stacking, manually assisted coughing and cough assist machines to help the patient cough up secretions alone. In this whole decision chain, the one clear hard marker is the peak cough flow (PCF). Once it falls below 270 L/min, the guideline recommends using cough assistance techniques (Strickland 2013).
When cough assistance is needed
- When PCF is below 270 L/min, the guideline recommends cough assistance (Strickland 2013)
- The patient's cough has become weaker and secretions cannot be brought up, with no improvement even after sitting up and taking in fluid
- The patient has neuromuscular disease, the muscles responsible for coughing are weak, and coughing alone can no longer clear secretions
Limits of the clinical evidence
- For cough assist machines (MI-E) in patients with neuromuscular disease, the evidence is currently not enough to support or oppose them as routine practice (Morrow 2013)
- 270 L/min is the one decision figure with a clear threshold, and in all other situations clinical judgement is needed
- 160 L/min represents an "ineffective cough". This is a dividing line from clinical observation, and is not the hard marker figure cited on this page
Step 3: which situations really need suctioning through a tube
Suctioning is useful only when neither voluntary coughing nor cough assistance can clear the secretions, or when the patient has an artificial airway. The patient has reached the level where suctioning is needed only in the kinds of situation below:
- The patient has a tracheostomy or an artificial airway that bypasses the normal cough reflex, so secretions collect in and around the tube
- Cough assistance methods such as chest percussion, breath stacking and cough assist machines have all been used, and the secretions left in the large airways still cannot be cleared
- Because of bulbar weakness or impaired swallowing, saliva and secretions keep collecting and the patient cannot cough them away (Chatwin 2018)
- The patient shows clear signs of retained secretions, such as a rattling sound, a fall in oxygen saturation or laboured breathing
- If only a slight rattle is heard and the patient can cough it away alone, this is not a situation that needs suctioning
- Suctioning by the clock, in the belief that suctioning is better than not suctioning, is a practice the clinical guideline does not recommend
How often to suction, and how it relates to a clean airway
Suctioning more often and putting the tube in deeper do not make the airway cleaner.
More suctioning is not better. The process of suctioning can cause brief adverse effects such as a fall in oxygen saturation, bleeding, or changes in blood pressure and heart rate. If the technique is poor, it can injure the airway mucosa and even raise the risk of infection acquired in hospital (AARC 2010). The aim of suctioning is only to clear the secretions. The guideline advises shallow rather than deep suctioning, giving oxygen first if the patient lacks oxygen, and not instilling saline routinely every time.
How to tell that the patient has secretions collecting and needs help
Since suctioning should not be done by the clock, the basis for the decision lies in clinical signs. Looking at the following indicators together to judge whether secretions are truly retained and cannot be coughed up is far more accurate than relying on one or two rattling sounds. The actual situation should still be assessed professionally by the visiting nurse or therapist.
Limits of the clinical evidence on the effect of airway clearance
In deciding which level of airway clearance to use, besides observing the patient's clinical condition, it is necessary to look honestly at how well the existing medical evidence supports each method. The overall quality of evidence for respiratory physiotherapy is low. Airway clearance is quite safe in the short term and does help to clear secretions, but it cannot be exaggerated into curing disease. The table below sets out what evidence exists beside the range that must not be overstated.
- Airway clearance in bronchiectasis: safe in stable patients and can increase the amount of sputum cleared (Lee 2015)
- Cough assistance has a clear marker for use: recommended when PCF is below 270 L/min (Strickland 2013)
- Suctioning, in selected patients only, safely clears retained secretions that the patient cannot cough away alone, for the time being (AARC 2010)
- Effects on quality of life and lung function are low-quality evidence and cannot be treated as settled results (Lee 2015)
- Cough assist machines (MI-E): the existing evidence is not enough to support or oppose routine use (Morrow 2013)
- The effect of chest physiotherapy on mortality and cure in adult pneumonia is very uncertain (Chen 2022), so it must not be claimed to lower mortality or to cure
Incidentally, the clinical guideline also does not recommend routine airway clearance in chronic obstructive pulmonary disease (Strickland 2013). Pulmonary rehabilitation exercise for COPD is a different prescription, and this page concentrates only on the decision of when suctioning is needed and does not repeat that exercise content.
Home care in Hong Kong and local resources
Put back into the Hong Kong home setting, the situations met most often are the ones below. The common principle is the same: do not suction by the clock, but act only when the clinical signs are clear.
Common home care situations
- When a bedbound older adult with a tracheostomy has a lot of phlegm, family members often cannot tell whether to use chest percussion or suctioning. The breath sounds and oxygen saturation should be observed first. If the older adult can cough alone or clear secretions with percussion, suctioning is not needed
- If a rattling sound is heard in the middle of the night and the oximeter alarm sounds at the same time, a carer easily becomes anxious and wants to suction deeply at once. At this point the patient should first be repositioned, given chest percussion and observed, and suctioning is needed only if there are signs of retained secretions
- If a patient with neuromuscular disease or after surgery has a weak cough and there is already a cough assist machine at home, cough assistance should be used first to help the patient cough secretions up, and suctioning is not always needed
Local resources in the health system
- The Hospital Authority's 智友站 (Smart Patient) provides official patient self-care and home care teaching material, at smartpatient.ha.org.hk
- Before a patient is discharged, ward nurses of the Hospital Authority teach family members how to suction a tracheostomy. For details see www.ha.org.hk
- The practical settings such as the suction pressure of the machine must follow the instructions of the hospital or those given at discharge, and the pressure must never be turned up by the family
In home physiotherapyassessments, the request family members make most often is to suction the patient every two hours. The core principle of home suctioning and secretion management, however, is to judge by whether signs of retained secretions have appeared, and not to follow a fixed timetable. The registered physiotherapists at Nova Health carefully observe the patient's rattling sounds, oxygen saturation readings and cough effectiveness. If secretions can be cleared with chest percussion or assisted coughing, no tube is used for suctioning. Suctioning is kept for patients for whom voluntary coughing and assistive techniques have both failed, or who have a tracheostomy or an artificial airway, which lowers the risk of mucosal injury and low oxygen. The therapist also explains the potential risks of suctioning to the family in detail, and stresses that the aim is that it is enough to clear what can be cleared, so that suctioning too deeply is avoided.