An incentive spirometer measures how deeply you can inhale, displayed as a volume reading in milliliters (mL) on the side of the device. Most models have a large clear column with a piston that rises as you breathe in, and a numbered scale running from about 250 mL up to 2,500 or 5,000 mL. The higher the piston climbs, the deeper your breath.
Parts of the Device
A standard incentive spirometer has three main parts you need to pay attention to: the main column, the flow indicator, and the goal marker.
The main column is the large transparent chamber where a piston (usually yellow) rises when you inhale through the mouthpiece. The numbers printed along the side of this column represent volume in milliliters. Whatever number the piston reaches at the peak of your breath is your inspiratory volume for that breath.
The smaller chamber, often mounted on top or to the side, contains a ball or float that indicates your flow rate, meaning how fast you’re pulling air in. This is your coach indicator. You want this ball to stay in a target zone (sometimes marked by two arrows or a shaded window) throughout your breath. If the ball shoots to the top, you’re inhaling too fast. If it barely lifts, you’re not inhaling with enough effort. A slow, steady breath that keeps the ball floating in the middle zone is the goal.
The goal marker is a sliding indicator on the outside of the main column. You set it to mark the volume you’re trying to reach. After your best breath, slide this marker to that level so you have a visible target for every attempt that follows.
How to Take a Reading
Sit upright or as close to upright as you can. Hold the spirometer level in front of you so the piston moves freely. Seal your lips tightly around the mouthpiece, then inhale slowly and deeply. Watch the piston rise. At the same time, glance at the flow indicator to make sure you’re breathing in at a steady pace, not gulping air.
When you’ve inhaled as fully as you can, note where the top of the piston lines up with the volume scale. That number, in milliliters, is your reading. Hold your breath for about 3 to 5 seconds before exhaling, then remove the mouthpiece and breathe out normally. Holding at the top of the breath helps keep your lungs fully expanded, which is the whole point of the exercise.
The piston should ideally rise into a marked target zone, often outlined in blue. If it reaches that zone and your flow indicator stayed steady, you’ve taken a good breath. If it falls short, that’s your baseline to improve from.
Setting and Adjusting Your Goal
Your healthcare team will typically give you a starting target based on your height, age, and the reason you’re using the device. If no one gave you a number, take three slow, deep breaths and note your best volume. Slide the goal marker to that level. This becomes the minimum you aim for on every subsequent breath.
As your lung capacity improves (especially during recovery from surgery), move the marker up in small increments. A common progression is raising your target by 250 mL once you can consistently hit your current goal. For context, a healthy adult’s full inspiratory capacity is typically well above 2,500 mL, but post-surgical patients often start much lower.
Volume vs. Flow Spirometers
Most incentive spirometers given to patients are volume-oriented, meaning the main reading is in milliliters and you watch a piston rise inside a calibrated column. These are the most common type in hospitals and for home use.
Flow-oriented spirometers work a bit differently. Instead of a piston, they have one to three lightweight balls in separate chambers. Each ball lifts when you reach a certain flow rate. You read these by counting how many balls you can keep elevated simultaneously. Three balls floating means you’re generating the strongest airflow. These devices measure how fast air moves rather than how much total air you inhale, so there’s no milliliter scale to read.
If your device has a numbered column with a piston, read the volume. If it has floating balls, count the balls and focus on keeping them elevated for the full duration of your breath.
How Often to Use It
There’s no single evidence-based frequency that outperforms all others, but the most common recommendations from clinical practice are 10 breaths every 1 to 2 hours while you’re awake, 10 breaths 5 times a day, or 15 breaths every 4 hours. Your doctor or respiratory therapist may adjust this based on your situation. The key is consistency: short, frequent sessions throughout the day work better than one long session.
Between sets, breathe normally and rest. If you feel lightheaded during a session, pause for a minute before continuing. That dizziness just means you’re hyperventilating slightly, and it passes quickly.
Common Reading Mistakes
The most frequent error is inhaling too quickly. A fast, sharp breath makes the piston jump but doesn’t actually fill your lungs as deeply as a slow, controlled inhalation. If your flow indicator ball slams to the top of its chamber, slow down. A good breath takes 3 to 5 seconds on the way in.
Tilting the device also skews your reading. The piston relies on gravity, so holding the spirometer at an angle can make it rise more easily or with more resistance than it should. Keep it upright and level.
Another common mistake is exhaling into the mouthpiece. The device only measures inhalation. Breathe out away from the mouthpiece, then seal your lips and inhale. If you blow into it, the piston won’t move and you may push moisture into the device.
Tracking Your Progress
Write down your best reading from each session, not the average. Over days and weeks, you should see a steady upward trend. A typical post-surgical patient might start around 750 to 1,250 mL and work back toward 2,000 mL or higher over several weeks. Progress isn’t always linear. Mornings may produce lower numbers than afternoons, and pain levels, fatigue, and medications all affect your readings day to day.
If your numbers plateau or drop consistently over several days, that’s worth mentioning to your care team. A sustained decline can signal developing complications like fluid in the lungs or worsening atelectasis (partially collapsed lung tissue), which is exactly what the spirometer is designed to help prevent.
Keeping the Device Clean
Wash the mouthpiece daily with mild dish soap and warm water, then let it air dry completely. Once a week, disinfect it by soaking it for 5 minutes in 70% rubbing alcohol or for 30 minutes in a white vinegar solution. Don’t submerge the main column or any internal components unless the manufacturer’s instructions say it’s safe. Moisture trapped inside the chamber can make the piston stick and give you inaccurate readings.