Phlegm builds up after surgery because general anesthesia slows the tiny hair-like cilia that sweep mucus out of your airways, and pain from the incision makes it hard to cough with any real force. Clearing that phlegm matters: retained mucus can block small airways, collapse portions of the lung, and set the stage for pneumonia. The good news is that a handful of straightforward techniques, most of which you can do yourself in a hospital bed or at home, are enough to keep your airways open while you heal.
Why Surgery Causes Phlegm to Build Up
Your airways are lined with a layer of mucus that traps dust, bacteria, and debris. Normally, cilia underneath that mucus beat in coordinated waves to push it upward toward your throat, where you swallow or cough it away without thinking about it. Certain anesthetic drugs slow those cilia dramatically. In a study measuring mucociliary clearance in vivo, combinations of ketamine with xylazine or dexmedetomidine cut clearance rates roughly in half compared to baseline, while propofol alone and fentanyl-containing combinations did not cause the same depression.1Scientific Reports. Differential effect of anesthetics on mucociliary clearance in vivo in mice So the type of anesthesia you receive affects how sluggish your mucus transport becomes, but some degree of slowdown is nearly universal after general anesthesia.
On top of that, surgery weakens the muscles you need for a strong cough. The diaphragm, which does most of the work during breathing and coughing, can become temporarily dysfunctional after chest and abdominal procedures. Patients with diaphragmatic dysfunction after surgery tend to have worse lung compliance and sputum retention because their cough is simply too weak to move mucus out.2Journal of Thoracic Disease. Diaphragmatic dysfunction is associated with postoperative pulmonary complications in the aged patients underwent radical resection of esophageal cancer: a prospective observational study Pain from an incision compounds the problem: your body reflexively guards the wound, so you instinctively hold back when you try to cough. The combination of slower cilia, a weaker diaphragm, and pain-limited coughing creates conditions where mucus pools in the lower airways and becomes difficult to shift.
Why Clearing Phlegm Quickly Matters
Retained secretions are not just uncomfortable. When mucus plugs a bronchial tube, air cannot reach the lung tissue beyond the blockage, and that segment of lung collapses, a condition called atelectasis. A case series examining postoperative patients with acute lung collapse from mucus plugging found that an abundance of secretions can obstruct bronchi and cause lung collapse well away from the actual plug.3Cureus. The Role of Bronchoscopy and Chest Physiotherapy in Postoperative Patients With Acute Lung Atelectasis Due to Airway Mucus Plugging: A Case Series and Review of Entity That collapsed tissue becomes a breeding ground for bacteria. Patients undergoing lung cancer resection, for instance, face high rates of respiratory complications driven by hypoventilation, secretory retention, pain, and ineffective cough.4Pneumon. Risk factors for postoperative pneumonia in patients undergoing resection for non-small cell lung cancer The takeaway: the sooner you start working mucus out of your lungs, the lower your risk of a serious complication like pneumonia or prolonged hospital stay.
The Supported Cough Technique
Coughing after surgery hurts, especially if the incision is on your chest or abdomen. But avoiding coughing entirely is worse than the discomfort. The trick is to support your wound while you cough so the incision site is stabilized and the pain is manageable.
Grab a firm pillow, a folded towel, or even your own hands and press them firmly against the incision. This is called “splinting.” Take a slow, deep breath in through your nose, filling your lungs as much as you comfortably can. Then cough sharply two or three times while holding steady pressure against the wound. The splint prevents the abdominal wall or chest wall from bulging outward with each cough, which is what generates most of the pain. A randomized trial of patients who had major abdominal surgery found that those who wore an abdominal binder (a more constant form of splinting) did not experience the significant increase in pain and distress that the no-binder group did.5Physiotherapy Canada. The Effect of Abdominal Support on Functional Outcomes in Patients Following Major Abdominal Surgery: A Randomized Controlled Trial
If a full, forceful cough feels impossible at first, try a “huff cough” instead. You take the same deep breath but instead of an explosive cough, you exhale forcefully with your mouth open, making a “huh” sound. It generates less pressure on the wound while still creating enough airflow to move mucus upward. Aim to do either version every one to two hours while you are awake during the first few days after surgery.
Deep Breathing Exercises and Incentive Spirometry
Deep breathing is the foundation of postoperative lung care. When you breathe shallowly because of pain or sedation, the smallest airways at the base of your lungs tend to close. Periodic deep breaths pop them back open, and the airflow itself loosens mucus stuck in smaller tubes. A sustained deep breath held for a few seconds at the top allows air to seep behind mucus plugs and push them toward larger airways where you can cough them out.
Many hospitals hand you a plastic incentive spirometer at your bedside. You breathe in through a mouthpiece and try to raise a ball or piston to a target level, then hold the breath for a couple of seconds. The device offers visual feedback on your inspired volume, which is thought to improve technique and increase motivation compared to uncoached deep breathing alone.6JAMA Surgery. The Effect of Incentive Spirometry on Postoperative Pulmonary Function Following Laparotomy: A Randomized Clinical Trial Whether the spirometer adds measurable benefit beyond simple deep breathing exercises has been debated for years, and trial results are mixed. But even skeptics agree that using one does no harm and at least reminds you to keep breathing deeply, which is half the battle when you are groggy and sore.
A practical routine: use the spirometer (or just do slow, maximal inhales without one) ten times every hour while you are awake. After every ten breaths, follow up with two or three supported coughs. This simple cycle keeps mucus mobile throughout the day.
Getting Upright and Moving
Lying flat is the worst position for clearing phlegm. Mucus pools in your dependent lung zones, and gravity works against you instead of for you. Simply moving from lying down to sitting upright improves blood oxygen levels and lung function in surgical patients.7PubMed Central. Importance of early postoperative mobilization: comprehensive review Sitting at the edge of the bed, standing, and eventually walking the hallway all allow gravity to pull mucus downward toward the larger central airways where a cough can move it out.
You do not need to do laps around the ward. Even short walks to the bathroom and back, repeated a few times a day, help expand the lungs far more than hours of lying in bed punctuated by occasional spirometer use. If you cannot stand, elevating the head of the bed to at least 30 to 45 degrees keeps mucus from settling and makes each breath a little deeper.
Postural Drainage
Postural drainage takes gravity assistance a step further by positioning your body so that specific lung segments drain into larger airways. For mucus stuck in the lower lobes, lying on your side with the affected side up (so the lower lobes are above the main bronchi) helps. For upper-lobe secretions, sitting upright and leaning slightly forward is often enough. A study of esophageal cancer patients found that combining chest physical therapy with improved postural drainage effectively prevented postoperative atelectasis, aided chest drainage, and helped lung function recover.8Semantic Scholar / Chinese Journal of Modern Nurses. Application of chest physical therapy combined with improved postural drainage method in patients with esophageal cancer after operation
Your physical therapist or nurse can guide you on which positions are appropriate given the location of your surgery. Postural drainage is often paired with gentle chest percussion, where a cupped hand pats rhythmically over the area being drained, or with vibrations applied to the chest wall during exhalation. These techniques loosen adherent mucus from airway walls so gravity can do the rest.
Oscillatory PEP Devices
If you have ever seen someone breathe through a small handheld device that makes a buzzing, vibrating sensation, that is likely an oscillatory positive expiratory pressure (PEP) device. Brand names vary, but the principle is the same: you blow out through the device, which creates back-pressure in your lungs while simultaneously delivering rapid vibrations to the airway walls. The combination splints the airways open longer during exhalation, prevents small airways from collapsing, and shakes mucus free.
A study of cardiac surgery patients found that oscillatory PEP therapy had a positive effect on sputum clearance, ventilation, and the lungs’ ability to transfer oxygen into the blood.9PubMed. [The use of oscillatory respiratory therapy with positive expiratory pressure (PEP-therapy) to restore the functional state of the lungs in patients after cardiac surgery] These devices are appealing because they are easy to use independently and give you something active to do between coughing sessions.10Journal of the Scientific Society. Effect of Flutter Along with Conventional Chest Physiotherapy on Peak Expiratory Flow Rate among Coronary Artery Bypass Graft Patients Your respiratory therapist can set the resistance level and show you the correct technique. Sessions typically last five to fifteen minutes and are repeated several times daily.
Hydration and Nebulized Solutions
Thick, sticky mucus is harder to cough up than thin, watery mucus. Staying well hydrated by drinking fluids throughout the day helps keep secretions from drying out and cemite the airways. Hospitals may also offer nebulized saline to help thin secretions directly at the airway surface. Inhaled hypertonic saline draws water into the mucus layer by osmosis, making it less elastic and easier to expectorate. It also disrupts the chemical bonds within the mucus gel itself, reducing its stickiness.11Europe PMC / Journal of the Royal Society of Medicine. Mechanisms and applications of hypertonic saline
You might expect that over-the-counter mucolytic drugs like acetylcysteine (the fizzy tablets sometimes marketed for colds) would be the obvious solution. The reality is more nuanced. While the term “mucolytic” sounds helpful, reducing mucus viscosity too much can actually impair cough transport, because a cough works best on mucus with some body to it. For that reason, many older mucolytic agents like acetylcysteine are not considered effective for clearing lung secretions, and their routine postoperative use is generally not recommended.12Elsevier. The pharmacologic approach to airway clearance: Mucoactive agents Stick to adequate hydration and nebulized saline unless your doctor prescribes something specific.
Managing Pain So You Can Actually Cough
All of the techniques above depend on one thing: your willingness and ability to cough and breathe deeply. If the pain is severe enough, no amount of encouragement will get you to produce a strong cough. Adequate pain control after surgery is not just about comfort; it is a prerequisite for airway clearance.
Regional nerve blocks are increasingly used alongside (or instead of) high-dose opioids to control surgical pain while preserving the ability to cough. In a randomized trial of patients after minimally invasive cardiac surgery, a regional block of the chest wall roughly halved the 24-hour opioid requirement and produced lower pain scores both at rest and during coughing compared to fentanyl-based pain management.13Bioinformation. Effect of serratus anterior plane block versus fentanyl for postoperative pain control and stress response after minimally invasive cardiac surgery: Randomised controlled study Lower opioid use is itself a win for phlegm clearance, because opioids suppress the cough reflex and can slow gut motility, leading to nausea that discourages deep breathing.
If you find that pain is preventing you from coughing effectively, tell your nurse. Timing your airway clearance exercises 20 to 30 minutes after a dose of pain medication, when the drug is working at its peak, makes a noticeable difference. Do not push through severe pain without support, but also do not let mild discomfort become an excuse to skip every coughing session.
Who Is at Higher Risk
Some people accumulate more phlegm and have a harder time clearing it. Smokers are at the top of the list: a smoking history of 20 or more pack-years was associated with roughly five times the odds of postoperative pulmonary complications in patients with asthma.14BMC Pulmonary Medicine. Risk factors of postoperative pulmonary complications in patients with asthma and COPD Patients with COPD face added risk from longer operations, upper abdominal incisions, and older age, though being on active COPD treatment before surgery appears protective.
Older adults, people who are obese, and anyone with a pre-existing lung condition should expect a more intensive postoperative pulmonary routine. Your surgical team may bring in a respiratory therapist earlier and schedule more frequent sessions. If you fall into any of these groups, quitting or reducing smoking even a few weeks before surgery, and starting breathing exercises beforehand, can shift the odds in your favor.
What You Can Do Before Surgery
The best time to start clearing phlegm after surgery is, paradoxically, before surgery. Preoperative inspiratory muscle training, where you practice breathing against resistance using a small handheld trainer, strengthens the diaphragm and intercostal muscles so they hold up better under the stress of anesthesia and an incision. A Cochrane review found that preoperative inspiratory muscle training roughly halved the risk of postoperative atelectasis and cut pneumonia risk by more than half compared to usual care.15PubMed Central. Preoperative inspiratory muscle training for postoperative pulmonary complications in adults undergoing cardiac and major abdominal surgery
Even a short training period makes a difference. A randomized trial of patients awaiting heart valve surgery found that just three days of preoperative inspiratory muscle training improved lung function before the operation and reduced the number of patients who developed pulmonary complications, primarily atelectasis, after surgery.16Journal of Physiotherapy. Preoperative inspiratory muscle training improves lung function prior to elective heart valve surgery and reduces postoperative lung function impairment and pulmonary complications: a randomised trial If you have a scheduled surgery coming up, ask your surgical team whether an inspiratory muscle trainer would be appropriate. They are inexpensive and simple to use at home.
Oral Hygiene and Infection Prevention
This one surprises most people: keeping your mouth clean before and after surgery helps prevent postoperative pneumonia. The bacteria that cause hospital-acquired pneumonia often originate in the mouth and throat, and intubation during surgery can push them down into the lower airways. A large multicenter retrospective study of patients who had esophageal cancer surgery found that lack of perioperative oral care was an independent risk factor for pneumonia, alongside older age and smoking.17PubMed. Prevention of postoperative pneumonia by perioperative oral care in patients with esophageal cancer undergoing surgery: a multicenter retrospective study of 775 patients
Brushing your teeth, using an antiseptic mouthwash (chlorhexidine rinses are commonly used in hospitals), and keeping dentures clean are all part of the picture. Some hospitals have formalized preoperative oral hygiene protocols for high-risk surgeries. If yours has not mentioned it, bring it up. It is a low-effort intervention with a meaningful payoff.
When Coughing Is Restricted
Not every surgery allows aggressive coughing. After certain eye procedures, for instance, forceful coughing can raise intraocular pressure and threaten the surgical repair. A study comparing airway management techniques during eye surgery found that patients managed with a standard endotracheal tube coughed almost universally in the immediate postoperative period, while those managed with a laryngeal mask airway did not cough at all.18CrossRef API. The Effect of the Laryngeal Mask Airway on Coughing After Eye Surgery Under General Anesthesia The anesthetic team may choose techniques specifically to minimize coughing in these situations.
Brain surgery, spinal fusion, and hernia repair are other examples where your surgeon may restrict how forcefully you cough. In these cases, gentle huffing, frequent deep breaths, incentive spirometry, and early mobilization carry more of the load. Your surgical team will tell you what restrictions apply; make sure you ask if they do not volunteer the information.
When to Call for Help
Most postoperative phlegm resolves within a few days as the effects of anesthesia wear off and you return to normal activity. But some warning signs mean the mucus is winning. Watch for a fever developing a day or two after surgery, increasing shortness of breath even at rest, coughing up discolored (yellow, green, or rust-colored) sputum, or a rapid heart rate that was not present before. These may indicate atelectasis progressing to pneumonia or a mucus plug large enough to block a significant airway. If conservative techniques are not enough, the medical team can escalate to bronchoscopic suctioning, where a thin, flexible scope is passed into the airways to directly aspirate mucus plugs under visualization.3Cureus. The Role of Bronchoscopy and Chest Physiotherapy in Postoperative Patients With Acute Lung Atelectasis Due to Airway Mucus Plugging: A Case Series and Review of Entity That procedure sounds intimidating, but it is usually quick and effective.
The vast majority of people never need bronchoscopy. Consistent, frequent use of the simpler techniques described above is enough to keep mucus moving. The biggest obstacle is usually not a lack of knowledge but a lack of motivation: it is hard to make yourself cough and breathe deeply when you are exhausted, nauseated, and in pain. Set a timer, enlist a visitor to remind you, and treat your breathing exercises the way you would treat taking a prescribed medication. Your lungs will thank you for it.