PFT Equipment Pulmonary Function Testing Machines Illustration

PFT Equipment: Pulmonary Function Testing Machines (2024)

by | Updated: Apr 28, 2024

Pulmonary function testing (PFT) is an invaluable tool in diagnosing and monitoring several types of respiratory conditions.

The equipment used in PFTs provides insights into lung volume, flow, diffusion capacity, and gas exchange, among other parameters.

To grasp the full spectrum of these tests, it’s essential to understand the different types of PFT equipment and their respective functions.

This article breaks down the primary types of PFT equipment, including their unique functions, applications, and significance in respiratory evaluations.

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What is PFT Equipment?

PFT (Pulmonary Function Test) equipment refers to specialized devices used to evaluate the functionality of a patient’s lungs and respiratory system. These tools measure lung capacity, volume, gas exchange, and airflow, helping clinicians diagnose, monitor, and treat respiratory conditions like asthma, chronic obstructive pulmonary disease (COPD), and other pulmonary disorders.

Types of PFT Equipment

Pulmonary function testing (PFT) equipment is employed to measure various aspects of lung function. Here are the primary types of PFT equipment:

  • Spirometer
  • Peak flowmeter
  • Body plethysmograph
  • Pulmonary gas analyzer
  • Gas-conditioning device
  • Blood gas analyzer
  • Silverman pneumotachometer
  • Pulse oximeter

Note: Each of these equipment types provides unique insights into lung function and helps in diagnosing and monitoring a myriad of respiratory conditions.


A spirometer is a diagnostic device used to measure the volume of air inspired and expired by the lungs.

It provides vital information about how much air the lungs can hold and how quickly one can move air in and out of the lungs.

This equipment is essential for diagnosing conditions like asthma, COPD, and other respiratory disorders.

Spirometer PFT Device Vector

Peak Flowmeter

A peak flowmeter is a handheld device that measures the peak expiratory flow rate (PEFR) – the maximum speed one can exhale.

By monitoring these rates, patients and healthcare providers can gauge the severity of asthma, the effectiveness of treatment, and even predict asthma attacks.

Regular measurements help in adjusting medications and interventions accordingly.

Peak Flow Meter Device Vector

Body Plethysmograph

A body plethysmograph assesses lung volume by having a patient sit inside an airtight chamber.

The device calculates the amount of air in the lungs by measuring the pressure changes inside the chamber as the patient breathes in and out.

It offers a more comprehensive lung function evaluation and is one of the only PFT devices that is capable of measuring a patient’s residual volume (RV).

Patient in Body Box Plethysmography PFT Vector

Pulmonary Gas Analyzer

A pulmonary gas analyzer is a device that measures the concentration of gases (typically oxygen and carbon dioxide) in the inhaled and exhaled air.

It provides insights into how effectively the lungs transfer oxygen into the blood and remove carbon dioxide from the blood.

These measurements are crucial for understanding the efficiency of the respiratory process and detecting abnormalities.

Gas-Conditioning Device

Often used in conjunction with other PFT equipment, a gas-conditioning device adjusts the humidity and temperature of the air/gas mixtures involved in pulmonary function testing.

This ensures that the measurements are consistent and not affected by external factors, leading to more accurate and reliable results.

Blood Gas Analyzer

A blood gas analyzer measures oxygen, carbon dioxide, and pH levels in arterial blood.

Assessing the concentration of these gases gives a clear picture of how effectively the lungs are moving oxygen into the blood and removing carbon dioxide from it.

This information is vital for the management and diagnosis of patients with acute or chronic respiratory failure and other conditions affecting gas exchange.

Silverman Pneumotachometer

The Silverman pneumotachometer is a flow-measuring device that determines the rate of airflow into and out of the lungs.

Equipped with a series of fine-mesh screens or slits, it measures the drop in pressure as air flows through.

This tool aids in generating flow-volume loops, which are essential for assessing conditions like airway obstructions.

Pulse Oximeter

A pulse oximeter is a noninvasive device that measures the saturation level of oxygen in the blood, commonly referred to as SpO2.

By placing a sensor typically on a fingertip or earlobe, it uses light absorption techniques to gauge oxygen saturation.

This equipment offers rapid insights into whether a person is receiving enough oxygen, making it a crucial tool in scenarios from routine check-ups to emergency situations.

Pulse Oximeter Device Vector

What is Pulmonary Function Testing?

Pulmonary function testing (PFT) is a comprehensive evaluation of the respiratory system’s function, used to diagnose and monitor lung diseases and conditions.

These tests measure the lungs’ ability to move air in and out, how well oxygen enters the bloodstream, and how effectively carbon dioxide is eliminated.

PFTs offer insights into the functional state of the lungs, assisting in identifying the type and severity of pulmonary problems.

Types of Pulmonary Function Tests

Each type of pulmonary function test provides specific insights into the health and performance of the respiratory system.

Here are the primary types:

  • Spirometry: A test that measures the amount (volume) and speed (flow) of air that can be inhaled and exhaled. It’s especially useful for diagnosing conditions that affect airflow, such as asthma and COPD.
  • Plethysmography: Assesses the total amount of air the lungs can hold by measuring functional residual capacity (FRC) and total lung capacity (TLC). It helps detect restrictive lung diseases.
  • Diffusion Capacity (DLCO): Evaluates how well oxygen passes from the lungs into the bloodstream. This test is crucial for identifying problems related to the alveoli, the tiny air sacs in the lungs.
  • Bronchial Challenge Test: Measures lung function in response to various stimuli (like methacholine or exercise) to assess the reactivity or “responsiveness” of the airways, commonly used in asthma diagnosis.
  • Six-Minute Walk Test (6MWT): A submaximal exercise test that assesses aerobic capacity and endurance. The distance covered in six minutes serves as an indicator of functional status, especially in conditions like pulmonary hypertension or interstitial lung disease.
  • Peak Expiratory Flow (PEF): Measures the fastest speed at which a person can exhale. It’s often used by asthma patients to monitor their condition at home with a peak flow meter.
  • Fractional Exhaled Nitric Oxide (FeNO) Test: Measures the concentration of nitric oxide in the breath. Elevated levels can indicate inflammation in the airways, which can be a sign of asthma or other inflammatory lung conditions.
  • Maximal Voluntary Ventilation (MVV): Assesses the maximum amount of air a person can inhale and exhale within one minute. This test gives an idea about the endurance of the respiratory muscles and the overall lung function.
  • Nitrogen Washout: A test that measures lung volume by analyzing the amount of nitrogen exhaled after inhaling pure oxygen. Used to determine total lung capacity and functional residual capacity, and to assess the distribution of ventilation within the lungs.

Note: Lung function testing can be used individually or in combination, depending on the specific clinical question. Proper interpretation requires understanding the interplay between the tests, the patient’s clinical presentation, and other diagnostic information.

FAQs About PFT Equipment

What is the Most Common Type of PFT Equipment?

The most common type of PFT equipment is the spirometer. It is used to measure the volume and speed of air that a patient can inhale and exhale.

Spirometry helps physicians diagnose and treat patients with both obstructive and restrictive lung diseases.

What are the Different Types of Spirometers?

There are several different types of spirometers, including:

  • Volume-displacement
  • Water-seal
  • Dry-rolling seal
  • Bellows-type
  • Flow-sensing
  • Portable
  • Ultrasonic

Note: Each type of spirometer has the same ultimate goal; however, they all function slightly differently. The type of spirometer that is used will depend on the specific needs of the patient.

What are the Types of Plethysmography?

There are three primary types of plethysmography:

  1. Body
  2. Pressure
  3. Flow

Body plethysmography is the most common type and is able to measure a patient’s residual volume.

As their names suggest, pressure and flow plethysmography can measure the changes in pressure and flow in the lungs, respectively.

What are Gas Distribution Tests?

Gas distribution tests assess how well gases like oxygen and carbon dioxide are distributed and exchanged within the lungs.

These tests, including the diffusion capacity for carbon monoxide (DLCO), offer insights into the functionality of the alveoli and the efficiency of gas transfer between the lungs and bloodstream.

Abnormal results can indicate issues such as emphysema, pulmonary fibrosis, or other conditions affecting the lung’s air sacs.

What Equipment is Used for Pulmonary Function Testing?

For pulmonary function testing, various equipment is used, depending on the specific test being conducted.

The primary devices include a spirometer, plethysmograph, diffusion capacity apparatus, and sometimes, gas analyzers for arterial blood gas analysis.

These tools help measure different aspects of lung function, from airflow to gas exchange.

Does a Spirometer Measure Lung Capacity?

No, a spirometer primarily measures airflow, capturing data such as the volume of air inhaled and exhaled over time.

However, it can measure certain lung volumes like the forced vital capacity (FVC).

To measure the total lung capacity (TLC), other tests like plethysmography or nitrogen washout are typically required.

Related: PFT TMC Exam Practice Questions

Final Thoughts

PFT equipment is used for assessing pulmonary health and assisting in making informed decisions about a patient’s condition.

From measuring airflow obstructions to detecting diffusion impairments, these tools remain essential in the early detection, diagnosis, and management of respiratory diseases.

As the field of respiratory medicine continues to evolve, it’s crucial for medical professionals to be well-versed in the capabilities and uses of different PFT devices, ensuring optimal patient outcomes.

John Landry, BS, RRT

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


  • Faarc, Mottram Carl Ba Rrt Rpft. Ruppel’s Manual of Pulmonary Function Testing. 11th ed., Mosby, 2017.
  • Faarc, Kacmarek Robert PhD Rrt, et al. Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
  • Ponce MC, Sankari A, Sharma S. Pulmonary Function Tests. [Updated 2022 Sep 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023.

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