Oct 08, 2026 Closing the Pediatric PFT Gap: Bringing Complete Lung Testing Within Reach for Kids
For a child with persistent respiratory symptoms, spirometry can provide important information—but it does not answer every pulmonary function question. Lung volumes can help identify restriction, hyperinflation and air trapping, while diffusing capacity (DLCO) adds information about gas transfer. Together, these measurements can provide a more complete physiologic picture.
Yet access to a complete pediatric PFT can become complicated once testing needs extend beyond spirometry.
Traditional lung volume measurement may require a body plethysmography cabin, dedicated laboratory space, specialized equipment and a patient who can comfortably cooperate with the testing procedure. For practices without that infrastructure, children may need to be referred to a hospital or dedicated PFT laboratory simply to complete the next part of their pulmonary function assessment.
That creates an access gap between the testing a clinician wants and the testing that can practically be performed where the child already receives care.
New approaches to pediatric pulmonary function testing can help close that gap. Cabinless technology now makes it possible to measure lung volumes during relaxed tidal breathing without placing the patient inside a body box—creating an opportunity to bring more comprehensive pulmonary testing closer to children and their clinicians.
Where the Pediatric PFT Gap Actually Opens Up
The pediatric PFT gap often appears when the clinical question requires more than spirometry. Pediatric spirometry can assess airflow, but confirming restriction or characterizing air trapping and hyperinflation requires lung volume measurements. When those capabilities are unavailable locally, the child may need referral to a hospital or specialized pulmonary function laboratory.
Spirometry is a familiar starting point for lung function testing in children. Measurements such as FEV1 and FVC can help clinicians assess ventilatory patterns and evaluate airway disease.
But spirometry does not directly measure total lung capacity (TLC) or residual volume (RV).
That distinction matters.
A reduced FVC, for example, may raise suspicion for restriction, but lung volume measurement is required to establish whether TLC is actually reduced. Similarly, measurements such as RV and RV/TLC can provide additional information when the clinician is evaluating air trapping or hyperinflation.
DLCO answers another question by assessing gas transfer across the alveolar-capillary interface.
A more comprehensive pediatric pulmonary function test may therefore include three complementary components:
- Spirometry: airflow and forced expiratory volumes
- Lung volumes: TLC, RV and functional residual capacity (FRC)
- DLCO: diffusing capacity and gas-transfer assessment
The clinical gap is not necessarily a lack of interest in obtaining those measurements. Frequently, it is a lack of practical access to all three in the setting where the patient is already being seen.
Why Kids Struggle Inside a Traditional Body Box
Body plethysmography requires the patient to sit inside an enclosed cabin and cooperate with a defined testing procedure. For some children, the combination of enclosure, unfamiliar equipment and respiratory coaching can make testing more difficult. A cabinless approach removes the enclosure itself from the equation.
For an adult who has undergone pulmonary function testing multiple times, entering a body box may be routine.
A child may experience the environment very differently.
The patient is asked to sit in an enclosed transparent cabin, wear a nose clip, breathe through a mouthpiece and follow the technologist’s instructions. Accurate pulmonary function testing depends on cooperation and technique, so discomfort or uncertainty can affect the testing experience.
Children also vary substantially in developmental readiness. Chronological age alone does not determine whether a child can successfully complete every maneuver.
This is why the patient experience is more than a convenience issue in pediatric PFT.
Simplifying the parts of testing that can be simplified may help clinicians and technicians focus their coaching on the portions that genuinely require active patient effort.
Removing the cabin is one such opportunity.
What Pediatric PFT Can Measure at Each Age
Pediatric PFT capability depends on the child’s developmental ability, the measurement being performed and the technology available—not simply chronological age. For the MiniBox+, children from age 5 can be tested. Spirometry, lung volume measurements and DLCO each have different cooperation requirements, so test selection should be individualized.
There is no single age at which every child becomes equally capable of performing every pulmonary function maneuver.
That is an important distinction when clinicians discuss a pulmonary function test in children.
Spirometry requires the child to understand and execute a coached forced expiratory maneuver. With appropriate pediatric coaching, many school-aged children can produce useful measurements, while performance in younger children varies.
Lung volume testing depends on the measurement method. Traditional body plethysmography involves specific breathing procedures inside a cabin. With the MiniBox+, lung volume measurements are obtained during relaxed tidal breathing, and PulmOne specifies pediatric use beginning at age 5.
DLCO typically requires greater cooperation because it uses a single-breath maneuver involving inspiration, breath holding and expiration.
In practice, the question is therefore not simply, “Is this child old enough for a PFT?”
A more useful question is:
Which measurements can this individual child perform reliably, and which testing technology minimizes unnecessary barriers to obtaining them?
That approach keeps the clinical question—not the equipment—at the center of pediatric pulmonary function testing.
The Equipment Barrier That Sends Kids Elsewhere
Complete PFT capability has traditionally required infrastructure that many office practices do not have. A body plethysmograph occupies substantial space, while conventional pulmonary laboratories require equipment, trained personnel and workflow capacity. When those resources are unavailable, children who need lung volumes or DLCO may be referred elsewhere.
The referral may be clinically appropriate. But sometimes it is driven primarily by equipment availability.
That distinction matters for practices evaluating how pulmonary care is delivered.
A child may already have established relationships with a pulmonologist, allergist or multidisciplinary care team. If the practice can perform spirometry but not lung volumes or DLCO, obtaining a more complete physiologic assessment introduces another location, another appointment and another workflow.
Traditional body plethysmography also has a physical footprint that can make adoption difficult for practices where space is limited.
This creates an infrastructure problem:
The clinician may have the expertise to interpret a complete PFT, and the patient may already be in the office—but the necessary testing capability is somewhere else.
Compact PFT technology changes that equation by separating complete pulmonary function testing from the assumption that lung volumes require a dedicated cabin.
For pediatric care in particular, that creates an opportunity to bring more of the diagnostic pathway into the child’s existing medical home.
How Tidal-Breathing Lung Volumes Skip the Cabin
The MiniBox+ measures lung volumes without a body cabin or inert gas. The patient breathes normally through a mouthpiece while the system obtains lung volume measurements in as little as 60 seconds of tidal breathing. A multicenter CHEST study found MiniBox TLC measurements were not significantly different from conventional body plethysmography measurements.
This is where cabinless testing represents more than a smaller piece of equipment.
It changes the measurement experience.
The MiniBox method derives total lung capacity during tidal breathing by analyzing gas pressures and airflow immediately before and after brief airway occlusions. The method does not require the patient to enter a sealed cabin or inhale an inert gas for lung volume measurement.
For the MiniBox+, lung volume measurement can be completed with as little as 60 seconds of relaxed tidal breathing.
The method has also been evaluated against conventional body plethysmography in peer-reviewed research.
A multicenter study published in CHEST evaluated 266 healthy participants and patients with obstructive or restrictive disorders across five centers in the United States and Europe. Researchers compared TLC measured using the MiniBox with TLC measured by conventional whole-body plethysmography.
Across the populations studied, there were no statistically significant differences between TLC measurements obtained using the two techniques. The investigators concluded that the MiniBox represented a clinically reliable method for obtaining lung volumes equivalent to plethysmography values.
Importantly, this study validated the lung volume measurement method across the studied population; it was not designed as a pediatric-specific equivalence trial.
For pediatric practice, the relevance lies in what the technology removes from the testing process: the body cabin and complex lung-volume respiratory maneuvers.
MiniBox+ is specified for testing children beginning at age 5, allowing appropriately selected pediatric patients to undergo cabinless lung volume measurement in the same compact system used for spirometry and DLCO.
Bring Pediatric Testing Into the Medical Home
Cabinless PFT technology can allow practices to perform spirometry, lung volumes and DLCO without installing a traditional body box. For children who can complete the required testing, that can keep more of the pulmonary function assessment within the office or clinic where their respiratory care is already managed.
Access changes the care pathway.
Consider a child being followed for persistent dyspnea, suspected restrictive physiology, asthma with concern for air trapping, or a systemic condition with potential pulmonary involvement.
When only spirometry is available locally, additional physiologic questions can trigger an outside referral.
With complete PFT capability in the practice, clinicians can potentially obtain spirometry, lung volumes and DLCO within the same clinical environment.
For the patient and family, that may mean fewer transitions between facilities.
For the clinician, it means pulmonary physiology can become more directly integrated into the visit, follow-up strategy and longitudinal record.
And for the practice, a compact system removes one of the historical barriers to offering complete PFT: the assumption that measuring lung volumes requires enough space for a body plethysmography cabin.
The MiniBox+ weighs less than 18 pounds and can be used as a desktop or cart-mounted system. A complete PFT—including spirometry, lung volumes and DLCO—can be performed in as little as 15 to 20 minutes, depending on the patient and testing required.
The goal is not to replace specialized pediatric pulmonary laboratories when advanced testing or specialist resources are needed.
It is to make routine, clinically appropriate pulmonary function testing available in more of the places where children already receive respiratory care.
How Pediatric Lung Testing Gets Reimbursed
In the United States, pulmonary function testing is billed according to the test performed rather than through a separate pediatric PFT code. Common codes include CPT 94010 for spirometry, 94726 for plethysmographic lung volume determination and 94729 for diffusing capacity. Coverage and payment depend on payer policy, medical necessity and documentation.
For practices considering in-office pediatric lung volume and DLCO testing, reimbursement is an operational question as well as a clinical one.
Common PFT codes include:
94010 — Spirometry
Used for measurement and graphic recording of forced expiratory airflow and capacity.
94060 — Bronchodilator responsiveness
Used for spirometry before and after administration of a bronchodilator when clinically indicated.
94726 — Lung volumes by plethysmography
Used for determination of lung volumes using plethysmography.
94729 — Diffusing capacity
Used for measurement of pulmonary diffusing capacity, such as DLCO.
The MiniBox+ performs tests corresponding to established pulmonary function CPT codes, including 94010, 94060, 94726 and 94729.
Coding alone, however, does not guarantee payment. Coverage varies by payer and plan, and documentation should support why each component of testing was medically necessary. Practices should verify current payer policies and coding requirements rather than assuming that every complete PFT battery is reimbursable for every patient.
The broader operational point is significant: bringing complete PFT capability into an office does not require creating an entirely new category of pulmonary testing. The same established testing components—spirometry, lung volumes and diffusing capacity—remain clinically recognizable and separately coded.
What Do Clinicians Ask Before Testing Kids?
Before ordering pediatric PFT, clinicians should identify the physiologic question, determine which measurements are needed and consider whether the child can cooperate with each required maneuver. Equipment, space, patient comfort, quality control, reference values and reimbursement should also be considered when deciding where testing is performed.
At what age can a child have a pediatric PFT?
It depends on the test, the child and the equipment. Some pulmonary function maneuvers require more active cooperation than others. The MiniBox+ is specified for use in children from age 5, with lung volume measurement performed during relaxed tidal breathing.
Is pediatric spirometry the same as a complete PFT?
No. Spirometry measures airflow and forced expiratory volumes but does not directly measure TLC or RV. A complete pulmonary function assessment may add lung volumes and DLCO when those measurements are clinically indicated.
Can spirometry diagnose restriction in a child?
Spirometry can suggest a restrictive ventilatory pattern, but a reduced TLC is needed to establish physiologic restriction. Lung volume measurement therefore provides information that spirometry alone cannot.
Does lung volume testing always require a body box?
No. Cabinless lung volume measurement is available. The MiniBox+ measures TLC, FRC and RV without enclosing the patient in a body cabin and without using inert gas for the lung volume measurement.
How long does cabinless lung volume testing take?
MiniBox+ lung volume measurements can be obtained with as little as 60 seconds of tidal breathing. A complete PFT with spirometry, lung volumes and DLCO can be performed in as little as 15 to 20 minutes.
How does cabinless lung volume measurement compare with a body box?
In a 266-participant, five-center study published in CHEST, TLC measured by the MiniBox was compared with conventional body plethysmography. Researchers found no significant differences between TLC measurements obtained with the two techniques and concluded that the MiniBox method provided clinically reliable lung volume measurements equivalent to plethysmography values.
The study included healthy participants and patients with obstructive and restrictive disease and validated the underlying MiniBox lung-volume method. It should not, however, be characterized as a pediatric-specific equivalence study.
Which reference standards should be used for children?
Pediatric PFT interpretation requires appropriate reference equations that account for variables such as age, height and sex. Laboratories should follow applicable ATS/ERS technical standards and use appropriate reference equations, such as Global Lung Function Initiative (GLI) equations where applicable to the measurement and patient population.
When is complete PFT useful in pediatric care?
The answer depends on the clinical question. Lung volumes may add important information when restriction, hyperinflation or air trapping is being evaluated, while DLCO provides information about gas transfer. Testing should be selected based on clinical indication rather than routinely ordering every available measurement.
Closing the Access Gap
The central challenge in pediatric pulmonary function testing is not simply whether children can be tested.
It is whether clinicians can obtain the right pulmonary measurements, in the right patient, without unnecessary barriers created by the testing environment itself.
Spirometry remains foundational. But when the clinical question extends to restriction, hyperinflation, air trapping or gas transfer, spirometry alone may leave important physiologic questions unanswered.
Historically, answering those questions could mean sending the child somewhere with a full pulmonary function laboratory and a body plethysmograph.
That is no longer the only model.
With the MiniBox+, children from age 5 can access spirometry, cabinless lung volume measurements and DLCO through one compact PFT system. Lung volumes can be measured during as little as 60 seconds of relaxed tidal breathing, without placing the patient inside a cabin.
For pulmonologists and other clinicians caring for children with respiratory disease, that creates a different possibility: bring more complete pulmonary function testing to the patient instead of sending the patient to the equipment.
Learn how MiniBox+ can bring complete, cabinless PFT capability to your practice.
Clinical References
- Fredberg JJ, et al. Validation of a Novel Compact System for the Measurement of Lung Volumes. CHEST. 2021;159(6):2356-2365. doi:10.1016/j.chest.2021.01.052.
- American Thoracic Society/European Respiratory Society technical standards and guidance for pulmonary function testing.
- Global Lung Function Initiative reference equations and resources.
- Centers for Medicare & Medicaid Services. Pulmonary function testing coding and billing guidance.
Reimbursement information is provided for general informational purposes only and does not constitute coding or billing advice. Coverage and reimbursement vary by payer, plan, indication and documentation. Providers should verify current requirements with the applicable payer.