In a tenement building in Sham Shui Po, an older man who had had a stroke and has a tracheostomy has just come home from hospital, and his wife looks after him alone. The community nurse taught suction technique at the first home visit, but the wife still has no confidence about how deep to insert the catheter and how long to suction. Whenever she hears phlegm in her husband's throat she rushes to suction, and often only dares to stop when his face is flushed red and the number on the oximeter has dropped sharply. She asked the visiting therapist: "Does louder phlegm mean I have to suction longer and deeper?"
The facts are the opposite. Home suctioning mainly serves patients with a tracheostomy, an artificial airway, or a weak cough who cannot clear phlegm themselves. It can safely and briefly help to clear retained secretions, but it is only a supporting measure for particular patients, and there is no research evidence that it lowers mortality or other hard outcomes. The core of the procedure is safety: each suction lasts no more than 15 seconds, oxygen saturation is monitored throughout, movements stay gentle, and the principles of infection control are strictly kept (AARC guideline, Restrepo et al. 2010). The sections below go through which patients really need suctioning, the correct procedure, and the steps where mistakes are most often made.
Which patients need suctioning at home
Suctioning is not "suction whenever there seems a lot of phlegm". It is meant for patients who cannot cough up secretions on their own. The core of the clinical judgement is whether the patient can clear the airway alone. The American AARC guideline states clearly that for patients with neuromuscular disease whose peak cough flow (PCF) is below 270 L/min, cough assistance techniques should be considered (Strickland et al. 2013). This value is one of the few hard markers in respiratory care that has a clear threshold.
| Tracheostomy / long-term intubation | Because an artificial opening has been made in the trachea, the normal cough reflex and the cilia that clear phlegm are bypassed, and phlegm easily collects inside and outside the tracheostomy tube, so the need for suctioning has to be assessed regularly. |
| Neuromuscular disease (such as motor neurone disease) | The breathing and cough muscles of these patients are not strong enough, and when peak cough flow falls below 270 L/min it is hard for them to clear phlegm alone. They belong to the group for whom the AARC guideline advises cough assistance (Strickland et al. 2013). |
| Impaired consciousness or swallowing | If the patient cannot cough effectively or protect his own airway, phlegm and saliva easily collect. In such cases a professional assessment must decide which method of suctioning to use and how often. |
| Not suitable for everyone | If the patient can cough alone and there is not much phlegm, routine suctioning should not be done. Too much suctioning only irritates the airway mucosa and raises the risk of injury and infection. |
It is worth noting that besides suctioning there are a number of other breathing support methods. Manual chest percussion and airway clearance techniques belong to a different professional area, and the details can be found in chest percussion and airway clearance techniques. The mechanical insufflation-exsufflation (MI-E) cough assistance for patients with a weak cough is covered on the page on cough assistance for people with neuromuscular disease.
What suctioning can and cannot do
Carers must first set reasonable expectations: suctioning safely and briefly helps to clear retained secretions, and is not a way of treating disease in itself. The clinical evidence for respiratory physiotherapy is generally of low certainty at present, and claiming that suctioning can "treat pneumonia" or "reduce hospital admissions" is an exaggeration.
A systematic review looked at the effect of manual hyperinflation in critically ill intubated patients on ventilators, and concluded that it could not be shown to have real clinical benefit. Only some inconsistent short-term physiological changes were seen (some patients had better lung compliance and sputum clearance, but patients with acute lung injury did not), and there was no effect on the main outcomes such as shortening the hospital stay or preventing ventilator-associated pneumonia. The related side effects are rare, but cardiac output falls temporarily by about 10 to 15%, which has little clinical effect (Paulus et al. 2012).
Similarly, a Cochrane review found that chest physiotherapy may have no clear effect on mortality in adult pneumonia (conventional chest physiotherapy RR 1.03, 95% confidence interval 0.15 to 7.13, from 2 trials with 225 people). The certainty of evidence is extremely low, and for cure rate it also mostly had no clear effect (Chen et al. 2022). As for airway clearance techniques, another Cochrane review found them safe in stable bronchiectasis, with more phlegm cleared and a possible improvement in quality of life, but all outcomes rest on low-quality evidence, and the effect on the number of exacerbations is unclear (Lee et al. 2015).
In other words, the right place for suctioning is "helping patients who cannot clear phlegm alone to clear it safely", and not "curing the disease at its root". Once this is recognised, carers will not suction too much or too hard in their eagerness to help.
The five safety principles of suctioning in the AARC clinical practice guideline
The five points below are not ordinary research data. They are the safety limits set out in the clinical practice guideline on suctioning by the American Association for Respiratory Care (AARC) (Restrepo et al. 2010), and the iron rules of procedure that home carers most need to remember:
There is one more principle about oxygen: pre-oxygenation before suctioning should be considered only when the patient has a clinically clear fall in oxygen saturation, and no extra oxygen needs to be given as a routine every time (Restrepo et al. 2010).
The correct steps for using a home suction machine
The procedure below is based on the AARC safety markers (Restrepo et al. 2010). Because different models of home suction machine differ slightly in how the negative pressure is set and in the design of the connectors, the machine in the patient's home should be used in practice, following the method demonstrated in person by the community nurse or the physiotherapist.
- 1Check the equipment, wash hands and put on glovesFirst check that the suction pressure has been set as the healthcare team instructed, that the catheter size is right, and that the collection bottle is clean. Then wash hands thoroughly and put on clean gloves, keeping an aseptic technique throughout.
- 2Let the patient settle the breathing and measure oxygen saturationBefore suctioning, note the patient's usual oxygen reading. Only when the patient's oxygen saturation is clearly low is oxygen given first as the healthcare team instructed, and in general no extra oxygen is given as a routine every time.
- 3Insert gently to a suitable depthWhen putting the catheter in, do not cover the suction control port, and place the catheter gently into the airway. Suction should be shallow, avoiding pushing the catheter to the bottom so that it hits the carina and injures the mucosa.
- 4Suction intermittently while withdrawing, no more than 15 seconds in allCover the control port to start suction, rotate the catheter and withdraw it, applying intermittent suction. From the start of negative pressure to the catheter being fully out, the whole process must be under 15 seconds, and the oximeter reading must be watched throughout.
- 5Stop, let the patient settle the breathing and watch oxygen saturationStop at once after one suction and let the patient catch their breath. Watch carefully whether oxygen saturation recovers and whether the face colour and breathing return to normal, and only then decide whether another suction is needed.
- 6Clean the catheter and equipment and record the phlegmAfter suctioning, rinse the suction tubing with clean water and wash the collection bottle as instructed. Also note the amount, colour and thickness of the phlegm, and if it turns yellow-green or has blood streaks, tell the healthcare team early.
Oxygen monitoring before and after suctioning, and danger signs
During home suctioning, the pulse oximeter is the most important safety line. Because suction briefly takes oxygen out of the airway, the carer must on every occasion "note a baseline before, watch the reading during, and see whether it recovers after".
If during suctioning the patient's face turns blue, oxygen saturation drops sharply, the heartbeat is abnormal or the phlegm is blood-stained, stop suctioning and withdraw the catheter at once, let the patient catch their breath or give oxygen as the healthcare team instructed, and watch whether oxygen saturation recovers. These situations are mostly because a single suction went on too long or the movements were too hurried. If this keeps happening, stop at once and contact the community nurse or the treating healthcare team, and never force on with suctioning.
If the home also has a mechanical cough assist machine, tracheostomy equipment or a ventilator, the settings and the meaning of the alarms should first be explained clearly by the healthcare professionals. For the principles of care of a home ventilator and tracheostomy, see the page on home ventilators and tracheostomy care.
Infection control and cleaning the equipment
The airway is the gateway straight to the lungs, and if suction equipment is not kept clean, bacteria are sent into the lower airway again and again. The AARC guideline stresses in particular that an aseptic or clean technique must be kept during the procedure (Restrepo et al. 2010). In the home, carers can go through the checklist below item by item:
- Wash hands thoroughly before and after every suction, and wear clean gloves during suctioning
- Rinse the tubing at once after every suction, and change suction catheters regularly as the healthcare team instructs
- Empty, wash and disinfect the collection bottle regularly, and never leave phlegm in it overnight
- Change the water used to rinse the suction tubing and the humidifier water of the ventilator as instructed, and never reuse dirty water
- Watch the colour and smell of the phlegm, and tell the healthcare team at once if it turns yellow-green or has blood in it
- Never reuse a single-use catheter for convenience, and never use the same catheter for both the mouth and the artificial airway in turn
Common carer mistakes and the main points of home training
When a physiotherapist visits for an assessment, the most common problem is not that the carer cannot work the machine, but "suctioning too often and too deep". The first lesson of home training is therefore often "cut down unnecessary suctioning", teaching family members to recognise the clinical signals that really call for suctioning and to give up the habit of rushing to suction at the slightest sound of phlegm.
Here is a real case. A patient with motor neurone disease in Sha Tin used a suction machine at home, and the domestic helper, after suctioning at night, did not wash the catheter and the collection bottle thoroughly. Within a few days the patient's phlegm became yellow and thick. After the physiotherapist visited, the infection control routine was reorganised: the tubing must be rinsed after every use, catheters changed daily as instructed and the collection bottle disinfected at set times. The family was also taught to recognise the warning sign that "phlegm changing colour means the healthcare team must be told". This is the key to doing suctioning safely and not blindly doing more of it.
Ways to clear phlegm other than suctioning
Suctioning is only one part of secretion management and is by no means the only method. For a patient with a weak cough, chest percussion, airway clearance techniques and cough assistance are also used together clinically. The current medical evidence has to be viewed objectively as well, however. For mechanical insufflation-exsufflation (MI-E) cough assistance in people with neuromuscular disease, the current evidence is "not enough to support or oppose its use" (5 trials with 105 people, all short term, with no data on mortality or quality of life; Morrow et al. 2013). For general airway clearance techniques, the guideline also does not recommend routine use in patients with chronic obstructive pulmonary disease (Strickland et al. 2013).
To see how home respiratory physiotherapy gives families systematic technical training and follow-up, see the page on home respiratory rehabilitation training for carers in Hong Kong. For a full picture of the respiratory treatment techniques and who they suit, go back to the overview of home respiratory physiotherapy and read what is needed.
When a physiotherapist is needed
If a family member has just come home from hospital with a tracheostomy or a suction machine and the carer has no idea how deep to insert the catheter and how long to suction, or if the patient has repeated sharp drops in oxygen saturation at each suction and the phlegm turns yellow-green or even blood-stained, a professional should be arranged to visit and assess. In the public system, the Hospital Authority Community Nursing Service can be referred by the treating doctor in a public hospital or by the discharge department, and a community nurse visits to give tracheostomy care, suctioning and guidance for carers (enquiries can go to the hospital that treated the patient or the Hospital Authority hotline 2300 6555, and the community medical services section at www.ha.org.hk can also be browsed). Carers can also phone the Social Welfare Department's "Carers Support Line" 182 183 at any time to ask about respite and community support services. As for private support, when the registered physiotherapists at Nova Health provide home physiotherapy, they use the suction machine in the patient's own home to demonstrate on the spot the intermittent suction technique and the main points of oxygen monitoring, and prepare a step card in Cantonese for the family to stick at the head of the bed, so that a non-professional carer, even alone late at night, can still complete the whole procedure step by step and safely.