Oct 10, 2017 A New Method to Measure Lung Volumes
Lung Volume measurements go beyond the flow rate and volume that spirometry can measure and gives further volume information about a patient’s lungs.
Lung Volume measurement determined by gas dilution methods are nearly 100 years old with the original method using hydrogen. Due to obvious safety concerns, hydrogen use did not last long and two methods – nitrogen washout and helium dilution – became the standard. Gas dilution methods for determining FRC are well accepted, but very few talk about the difficulty, effort, and time it takes to get good efforts. Both methods require a wait time between efforts with nitrogen washout having a recommended 60-minute wait period between efforts for patients with obstructive lung disease.
Body Plethysmography is not so simple
Lung volume measurement by body plethysmography have been around since the 1950’s. It is based on Boyle’s Law and its pressure-volume relationship. With a known pressure and volume of a box, the patient sits inside and performs a series of panting maneuvers during occlusion of the breathing apparatus. It is the mouth pressure during this occlusion and the subsequent change in pressure and volume of the box that is used to determine thoracic gas volume (TGV). TGV equals FRC when measured at end-expiratory breathing level.
The body plethysmograph is considered the “gold” standard for lung volume measurement; however, without an extremely well-trained technologist, there are a host of errors that can and do occur. Panting at end-expiratory level for 4 to 7 seconds is not easy, the temperature gradient between box air temperature and lung temperature causes drift that must be accounted for, it is not necessarily viable for claustrophobic and large-size patients, and there is potential for technologist bias when it comes to adjusting the PBox /PMouth loops.
The MiniBox+: Easier for Patients and Technologists
PulmOne’s MiniBox+™ is an innovative, desktop device for gasless LVM, as well as spirometry and diffusion testing, designed to improve ease of use and access to complete Pulmonary Function Testing (PFT).
The MiniBox+ developed by PulmOne is an innovative device developed to change the pulmonary function testing field from a cumbersome, difficult, and expensive practice to one that makes it easier for patients and technologists. It’s designed to reduce the cost of healthcare via smaller footprint and lower cost of ownership. The MiniBox+ is a desktop, gasless lung volume measurement system that can also perform spirometry and diffusion, delivering a new and modern device. It improves ease of use and access to complete pulmonary function testing.
The MiniBox+ PFT device uses several ~100 millisecond interruptions during normal tidal breathing. This mouth pressure data and its effect on the 15-liter internal box with known volume and pressure is combined into a data model and algorithm to determine thoracic gas volume. After six successful automatic interruptions the patient performs a slow vital capacity to complete the measurement. We now have the TLC, VC, FRC (TGV), ERV, and RV parameters. The entire effort takes ~90 seconds to complete.
The advantages of the MiniBox+ are:
- The patient needs to only tidal breath for ~6 -10 breaths followed by a slow vital capacity
- It does not require specific panting maneuver or rebreathing gases
- Does not require a patient to fit into a body box where they may be too big or claustrophobic
- Repeated efforts can be done sequentially, as there is no wait time between efforts.
The MiniBox+ provides an innovative solution to the traditional lung volume methods and brings testing to more patients at a lower cost.