How Long Do Pulmonary Function Tests Take?

A basic spirometry session, the most common pulmonary function test, typically takes about 15 to 30 minutes from start to finish. But “pulmonary function tests” is an umbrella term covering several distinct procedures, and the total time in the lab depends entirely on which ones your doctor ordered. A simple pre- and post-bronchodilator spirometry visit can wrap up in under an hour, while a methacholine challenge or full cardiopulmonary exercise test can keep you in the clinic for two hours or more. Understanding what each test involves makes it easier to plan your day and know what to expect.

Spirometry Alone Is the Fastest Option

Spirometry is the bread-and-butter lung function test. You breathe into a mouthpiece, take the deepest breath you can, and blow out as hard and as long as possible. The technician needs at least three acceptable efforts that closely match each other, and coaching you through those attempts is where most of the time goes. Some people nail it in five or six tries; others need a dozen before the results are consistent enough to be reliable. For most adults, the blowing portion itself takes roughly 10 to 15 minutes once you are seated and the equipment is calibrated.

Add in the time the technician spends entering your height, weight, age, and ethnicity into the system, explaining the maneuver, fitting the nose clip, and reviewing the tracings on-screen, and you are looking at about 20 to 30 minutes total for a standalone spirometry appointment. If your results are clean and reproducible early, you could be out even sooner.

Bronchodilator Reversibility Testing Adds a Waiting Period

When doctors want to know whether your airways open up in response to a rescue inhaler, they add a reversibility component. You do a round of spirometry first, then inhale a bronchodilator (usually salbutamol or albuterol), and then sit and wait before repeating the spirometry. That waiting period is where the extra time comes from, and the ideal length of that wait has been a subject of debate in pulmonary labs.

A study of adults with obstructive lung disease found that the mean individual peak bronchodilation occurred at 20 minutes for forced vital capacity and at 30 minutes for the key measure of airflow obstruction, with 20 minutes being the ideal time to judge reversibility in most cases.¹ Many labs historically used a shorter wait. In one pediatric pulmonary clinic, the average wait before repeat spirometry was only about 6.5 minutes before the clinic implemented a protocol change, which then extended it to roughly 16 minutes. That protocol change added only about 9 minutes to the total clinic visit, bringing the average from 83 to 92 minutes.²

So a pre- and post-bronchodilator spirometry visit, including check-in and paperwork, usually runs somewhere between 45 minutes and an hour and a half. If your lab follows the guideline of waiting 15 to 20 minutes after the bronchodilator, expect to be there closer to an hour. That waiting time is not wasted; the drug simply needs those minutes to reach its full effect on your airways, and testing too early can miss a meaningful response.

Lung Diffusion Testing and the Pauses Between Attempts

The diffusion capacity test, commonly called DLCO, measures how efficiently your lungs transfer gas from inhaled air into your bloodstream. Instead of blowing out as hard as you can, you breathe in a small, harmless amount of carbon monoxide mixed with a tracer gas, hold your breath for about 10 seconds, then exhale. The equipment measures how much carbon monoxide your lungs absorbed during that breath-hold.

The test itself sounds quick, but the pauses between attempts are what stretch the appointment. Guidelines recommend waiting at least 4 minutes between each attempt so the test gas clears from your lungs before the next one. If you have obstructive lung disease, that interval should be longer, around 10 minutes, because trapped air takes more time to wash out.³ You typically need at least two acceptable maneuvers, and sometimes three or four if the first attempts do not meet quality standards. With the test itself, the rest intervals, and the setup time, a standalone DLCO test takes roughly 20 to 40 minutes.

In practice, most labs order DLCO alongside spirometry. When both are done in the same visit, the combined session usually takes 30 to 60 minutes for someone with healthy or mildly impaired lungs, but can stretch past an hour for someone with severe obstruction who needs longer wash-out intervals between diffusion attempts.

Full Pulmonary Function Testing with Lung Volumes

When your doctor orders “full PFTs,” the requisition usually includes spirometry, DLCO, and lung volume measurements. Lung volumes are measured either in a body plethysmograph (a clear, phone-booth-sized box you sit inside) or by breathing a dilute helium mixture or nitrogen washout gas for several minutes. The plethysmography box approach is faster; you sit inside, the door closes, and you pant gently against a closed shutter while the pressure changes in the box reveal how much air your lungs hold. That portion takes about 10 to 15 minutes including the coaching and repeated efforts.

A complete PFT panel combining spirometry, lung volumes, and diffusion capacity generally takes 45 minutes to an hour and a half. The range is wide because it depends on how quickly you produce reproducible results, how much rest time you need between maneuvers, and how congested the lab is. If you have severe lung disease, expect the longer end of that range because your test gas clearance is slower and you may need more attempts to meet quality criteria.

Methacholine Challenge Tests Take the Longest

If your doctor suspects asthma but your baseline spirometry looks normal, a methacholine challenge (also called a bronchial provocation test) can reveal whether your airways are hyper-responsive. This is the most time-consuming pulmonary function test most people will encounter.

The procedure follows a stepwise protocol. First, you perform baseline spirometry. Then you inhale a saline control solution and repeat spirometry. After that, you inhale progressively higher concentrations of methacholine, with spirometry repeated after each dose to check whether your airflow has dropped significantly. The interval between consecutive doses generally should not exceed 3 minutes, and lung function measurements are taken at 30 and 90 seconds after each inhalation.⁴ The test ends either when your lung function drops by 20 percent or more, or when you have inhaled the highest concentration without a significant drop.

After the provocative phase, you inhale a bronchodilator and do one more round of spirometry to confirm your airways have recovered. All told, a methacholine challenge typically takes 60 to 90 minutes, though some protocols with more dose steps can run closer to two hours. You should plan to feel mildly short of breath during the test if your airways do react, but the bronchodilator at the end reverses this quickly.

Cardiopulmonary Exercise Testing

Cardiopulmonary exercise testing (CPET) combines lung function measurement with a graded exercise protocol on a stationary bike or treadmill while you breathe through a mask or mouthpiece. It is used to figure out whether unexplained shortness of breath originates from the lungs, the heart, deconditioning, or some combination.

The recommended protocol includes a resting phase of at least 3 minutes, a 3-minute unloaded warm-up phase (pedaling with no resistance), an 8- to 12-minute incremental phase where resistance increases steadily, and a recovery phase of at least 2 to 3 minutes.⁵ That adds up to roughly 16 to 21 minutes of actual testing time. But the appointment itself runs much longer because it includes setup of the ECG leads, blood pressure cuff, and pulse oximeter; calibration of the metabolic cart; baseline spirometry before the exercise; and a monitoring period afterward to make sure your heart rate and blood pressure return to normal.

Expect a CPET appointment to take 60 to 90 minutes in total. Some centers ask you to arrive 15 to 30 minutes early so the technician can explain the protocol, review your medications, and place the monitoring equipment without feeling rushed.

Pre-Test Preparation That Affects Your Schedule

The clock on your pulmonary function test actually starts well before you sit down in the lab. Several medications can influence your results, and you may be asked to withhold them for specific periods before the test. Bronchodilators are the biggest concern. Short-acting inhalers like albuterol are typically withheld for 4 to 6 hours, and long-acting bronchodilators for 12 to 24 hours. Even caffeine and smoking can affect airway tone and should be avoided for several hours beforehand.

A study of patients referred for pulmonary function testing found that drugs that could potentially affect reversibility measurements were frequently consumed within the recommended withholding windows, despite published guidelines advising otherwise.⁶ If you arrive having used your inhaler that morning, the technician may ask you to wait and come back, or your results may carry a disclaimer that they were obtained while on bronchodilator therapy. Either way, it is worth double-checking the preparation instructions with your doctor’s office a day or two before your appointment so you do not waste a trip.

You will also be asked to avoid heavy meals for a couple of hours before testing, since a full stomach can restrict how deeply you breathe. Wear loose, comfortable clothing that does not constrict your chest or abdomen. Tight waistbands and restrictive bras can measurably reduce the volumes you produce.

Testing Children and Preschoolers

Pulmonary function testing in children follows the same principles as in adults but almost always takes longer per attempt. Young children need more coaching, more demonstration, and more patience. They may not understand the instruction to “blow as hard and as long as you can,” and repeated failed attempts can lead to frustration and fatigue for everyone involved.

Specialized pediatric centers have developed strategies to get reliable results from preschool-aged children by using games, animations, and incentive tools. One center that has performed over 7,000 spirometry and impulse oscillometry tests on young children found that practical coaching strategies significantly improved success rates.⁷ Even so, parents should expect a pediatric PFT visit to take longer than an adult one. Budgeting 60 to 90 minutes for a visit that would take an adult 30 to 45 minutes is a reasonable starting point. Some children will finish faster; others may need the test rescheduled if they simply cannot cooperate on a given day.

Impulse Oscillometry as a Faster Alternative

One reason pediatric testing can run long is that spirometry requires a forceful, coordinated effort. Impulse oscillometry (IOS) sidesteps that problem. During IOS, you simply breathe normally through a mouthpiece while the machine sends small sound-wave pulses into your airways and measures how they bounce back. The maneuver takes about 30 seconds per trial, and because it requires only quiet tidal breathing, it works well for young children, elderly patients, and anyone who struggles with the forced breathing that spirometry demands.

Research comparing IOS to spirometry in patients with COPD and asthma found that IOS resistance measurements showed high repeatability, with consistency scores exceeding 0.8 on a standard reliability scale. That repeatability was actually higher than spirometry’s in patients with more severe disease, where spirometry’s reproducibility decreased as disease worsened.⁸ In terms of time, an IOS session including several trials and quality review can be done in about 10 to 15 minutes, making it one of the fastest pulmonary function assessments available. It does not replace spirometry for every clinical question, but when the goal is to screen for airway obstruction or track changes over time, IOS is efficient and well-tolerated.

Home Spirometry and How It Compares

Portable spirometers have made it possible to track lung function at home rather than visiting a lab every time. These devices are used in research settings, post-transplant monitoring, and increasingly in asthma management programs. A feasibility study in young adults with asthma had participants complete spirometry twice daily using a portable device, demonstrating that home monitoring is practical for engaged patients.⁹

Each home session takes only a few minutes, since you are skipping the check-in, the equipment calibration by a technician, and the coaching. You blow into the handheld device a few times, the results sync to an app, and you are done. The trade-off is accuracy and completeness: without a trained technician watching your technique and quality-checking each effort in real time, home spirometry values tend to be more variable than lab results. Home devices also cannot measure lung volumes or diffusion capacity. They are best thought of as a complement to periodic lab testing, not a replacement for it.

Why Your Visit Might Run Longer Than Expected

Even if you know which tests are on your order, several factors can stretch the appointment beyond the typical range. The most common is difficulty producing reproducible results. The lab technician cannot accept a spirometry effort where you coughed partway through, started blowing too late, or did not exhale long enough. Each rejected attempt means another round of coaching and another try, and some patients need ten or more attempts before getting three good ones.

Disease severity also plays a role. Patients with severe obstruction take longer to empty their lungs during spirometry (exhalation times of 15 seconds or more are common, compared to 6 seconds in a healthy person). The rest intervals between DLCO maneuvers need to be extended to allow test gas clearance, as noted earlier. And if you become short of breath or dizzy between maneuvers, the technician will pause and let you recover before continuing.

Lab scheduling is another wild card. Most pulmonary function labs serve multiple patients simultaneously on different equipment, and a backup early in the day can cascade through the schedule. Arriving on time and having followed the preparation instructions gives you the best shot at getting in and out without unnecessary delays.

What to Expect Physically During Testing

Spirometry and DLCO are not painful, but they are physically demanding in a way that surprises many first-timers. The forced exhalation maneuver requires a genuinely maximal effort, and doing it repeatedly can leave you lightheaded, flushed, or briefly short of breath. Some people feel mild chest tightness or a coughing fit after blowing hard several times in a row. These sensations are normal and pass quickly.

Methacholine challenges intentionally provoke your airways, so you should expect some chest tightness, wheezing, or coughing if your airways are reactive. The technician monitors you throughout and administers a bronchodilator as soon as the test endpoint is reached. Exercise testing on the bike or treadmill will make you sweaty and winded by design; the whole point is to push you to your symptom-limited maximum. Bringing a change of shirt and a water bottle is not a bad idea.

Across all tests, the nose clip is the most universally annoying part. It pinches your nostrils shut so all airflow goes through the mouthpiece, and it can feel uncomfortable after 20 or 30 minutes of repeated use. If it is slipping or hurting, ask the technician to adjust it. A poorly fitting nose clip can actually compromise your results by allowing air to leak around it.