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Body plethysmographic determination of thoracic gas volume (VTG), airways resistance (R_aw), and specific airways conductance (sG_aw) may be considered medically necessary as an adjunct to complete pulmonary function testing for any of the following indications:

• Measurement of lung volumes to distinguish between restrictive and obstructive processes; or

• Evaluation of obstructive lung diseases, such as bullous emphysema and cystic fibrosis, which may produce artifactually low results if measured by helium (He) dilution or nitrogen (N₂) washout; or

• Measurement of lung volumes when multiple repeated trials are required, or when the subject is unable to perform multi-breath tests; or

• Evaluation of resistance to airflow where plethysmography is necessary for accurate calculation of true lung volumes in persons with obstructive processes; or

• Determination of response to bronchodilators in patients who fail to show an improvement in forced expiratory volume in 1 second (FEV1) by spirometry; or

• Determination of bronchial hyperreactivity in response to methacholine, histamine, or isocapnic hyperventilation; or

• Diagnosis of restrictive lung disease; or

• For following the course of established restrictive or obstructive lung disease, and response to treatment.

All body plethysmography that does not meet the above criteria as an adjunct to pulmonary function testing is considered not medically necessary including, but not limited to, measurement of body water, fat composition, or lean body mass (e.g., using such methods as bioelectric impedance, BOD POD®, or Tanita®).

The following plethysmography mo­dalities are considered experimental, investigational and/or unproven:

• Inductance plethysmography;

• Capacitance plethysmography;

• Mechanical oscillometry; or

• Photoelectric plethysmography.

NOTE 1: For bioimpedance for detection of lymphedema, see MED201.036, Bioimpedance Devices for Detection of Lymphedema.

NOTE 2: For thoracic bioimpedance and inert gas rebreathing, see MED202.058, Cardiac Hemodynamic Monitoring for the Management of Heart Failure in the Outpatient Setting.

NOTE 3: For penile plethysmography, see MED201.030, Sexual Dysfunctions, Assessment and Treatment.

Plethysmography is the measurement and recording (by one of several methods) of variations in the size of an organ, body part, or limb reflecting the circulation of blood to that body area.

Background

Body plethysmography may be used for measurement of residual volume, functional residual capacity and total lung capacity. The patient sits inside an airtight box, inhales or exhales to a particular volume (usually functional residual capacity [FRC]), and then a shutter drops across their breathing tube. The subject makes respiratory effort against the closed shutter causing their chest volume to expand and decompressing the air in their lungs. The increase in chest volume slightly reduces the box volume (the non-person volume of the box) and thus slightly increases the pressure in the box. A calculation is made to determine the original volume of gas present in the lungs when the shutter was closed. Body plethysmography may be appropriate for patients who have air spaces within the lungs that do not communicate with the bronchial tree. In these individuals, gas dilution methods of measurement would give an erroneously low volume reading. (11)

Body composition analysis (i.e., BOD POD, a Body Composition Tracking System) measures whole body mass and volume, which are then used to estimate whole body density. The patient sits in a fiberglass cabin while computerized pressure sensors determine the amount of air displaced by their bodies. Once whole-body density is measured, the relative proportions of body fat and lean body mass can be calculated using population specific equations which relate body density to body fat and lean tissue masses.

Another test frequently billed as total body plethysmography is Body Composition Analyzer/Scales (Tanita). A person's height, age, and gender are entered and the patient steps on the scales. Within seconds, weight, body mass index and body fat percentages are displayed. If more in-depth results are desired such as hydration levels, fat free mass, basal metabolism rate, a separate software package is available. This type of analysis is not true plethysmography.

In vivo (in the living body, referring to a process or reaction occurring therein) body composition analysis involves prediction of total body water, extracellular water and intracellular water using the bioelectrical impedance system.

Photoplethysmography uses a light emitting diode to measure blood volume and pressure changes, based on absorption and reflection of light through the skin. Inductance plethysmography employs sensors that are able to measure changes in a cross-sectional area of the patient, for example to measure air in the lungs or gas in the abdomen. Capacitance plethysmography is usually done on the arm or leg to detect venous flow obstruction. The blood volume and pressure are calculated based on the ability of the body to hold an electrical charge. Mechanical plethysmography devices measure the amount of air or water that is displaced, which determines blood volume changes. Electrical plethysmography devices have replaced most mechanical devices.

Regulatory Status

There are two body plethysmography systems that have been cleared by the U.S. Food and Drug Administration (FDA) through the 510k premarket notification process:

• Sonamet Body Composition Analyzer, as known as BOD POD, developed by Life Measurement, Inc., Concord, California was cleared on June 27, 2006 and is designed to measure the mass and estimate the body composition of individuals. Once an individual's body composition has been determined, the BOD POD is able to accurately estimate Resting Metabolic Rate (RMR) and Total Energy Expenditure (TEE). (1)

• Modified-Sonamet Body Composition Analyzer, also known as PEA BOD for infants, developed by Life Measurement, Inc., Concord, California was cleared on March 1, 2004 and is designed to measure the mass and estimate the body composition of infants with body weights ranging between 1- and 8-kilograms, who do not require life support. (2)

FDA Product Code: OAC.

This may not be an “all inclusive” list of body plethysmography devices/systems or those that claim to be plethysmography devices, systems or analyzers and is subject to change. Refer to the FDA web site at <www.fda.gov> for additional information on devices.

This policy was created in 1990 and has since been updated periodically with searches of the MedLine database through February 26, 2018. This policy is primarily based on the American Academy of Respiratory Care (1994, revised and updated 2001). (11)

Body Plethysmography

Spirometry is the standard method for measuring most relative lung volumes; however, it is incapable of providing information about absolute volumes of air in the lung. Thus, a different approach is required to measure residual volume, functional residual capacity, and total lung capacity. Two of the most common methods of obtaining information about these volumes are gas dilution tests and body plethysmography. In body plethysmography, patients sit inside an airtight chamber equipped to measure pressure, flow, or volume changes, inhales or exhales to a particular volume (usually FRC), and then a shutter drops across their breathing tube. The subjects make respiratory efforts against the closed shutter, causing their chest volume to expand and decompressing the air in their lungs. The most common measurements made using the body plethysmograph are thoracic gas volume (VTG) and airways resistance (R_aw). Airways conductance (G_aw) is also commonly calculated as the reciprocal of R_aw. Specific airways conductance (i.e., conductance/unit of lung volume) is routinely reported as sG_aw. Other tests that can be measured in the body plethysmograph include spirometry, bronchial challenge, diffusing capacity (DLCO), single-breath nitrogen (N₂), multiple-breath N₂ washout, pulmonary compliance, occlusion pressure, and cardiac output, including pulmonary blood flow. (3-11)

Other Plethysmography

Inductance, capacitance, mechanical oscillometry, bioelectric impedance, and photoelectric plethysmography have not yet reached a level of development such as to allow their routine use in the evaluation of peripheral artery disease.

While plethysmography has been used to aid in the diagnosis of peripheral vascular disease, Doppler/duplex ultrasound (US) scan has become the method of choice and gives a more accurate and definitive diagnosis.  Color flow Doppler/duplex US scans are newer and preferable methods of detecting a venous thrombus with accuracy near that of venography.  Doppler US has become the method of choice when scanning for venous occlusive disease.  Plethysmography cannot detect deep calf venous thrombus. (10)

Ongoing and Unpublished Clinical Trials

An online search of site ClinicalTrials.gov identified several clinical trials in Table 1 comparing body plethysmography to other lung function testing. (12)

Table 1. Summary of Key Trials

Table Key:

NCT: National Clinical Trial.

Practice Guidelines and Position Statements

American Association for Respiratory Care (AARC)

In May 2001, the AARC published their 2001 revised and updated clinical practice guidelines that outline the indications for body plethysmography to determine VTG and R_aw. The AARC stated the indications for body plethysmography as (11):

1.         “For diagnosis of restrictive lung disease;
2.         For measurement of lung volumes to distinguish between restrictive and obstructive processes;
3.         For evaluation of obstructive lung diseases, such as bullous emphysema and cystic fibrosis, which may produce artifactually low results if measured by helium dilution or N₂ washout. With simultaneously determined volumes, an index of trapped gas (i.e., functional residual capacity (FRC) _{plethysmograph}/ FRC_{helium dilution}) can be established;
4.         For measurement of lung volumes when multiple repeated trials are required or when the subject is unable to perform multibreath tests;
5.         For evaluation of resistance to airflow;
6.         For determination of the response to bronchodilators, as reflected by changes in R_aw, sG_aw, and VTG;
7.         For determination of bronchial hyperreactivity in response to methacholine, histamine, or isocapnic hyperventilation as reflected by changes in VTG, R_aw, and sG_aw;
8.         For following the course of disease and response to treatment.”

Furthermore, the AARC provided the guidance to age-specific indications, taking into consideration the learning ability and communications skills of the patient being tested:

1.        “Neonatal: This Guideline does not apply to the neonatal population.
2.         Pediatric: These procedures are appropriate for children who can perform spirometry of acceptable quality and can adequately follow directions for plethysmographic testing.
3.         Geriatric: These procedures are appropriate for members of the geriatric population who can perform spirometry of acceptable quality and adequately follow directions for plethysmographic testing.” (11)

American Thoracic Society (ATS)/European Respiratory Society (ERS)

In 2005, the ATS/ERS released joint guidelines “Standardisation of Lung Function Testing” (13) for both healthy individuals and in patients with lung disease. The guidance concluded that in healthy individuals, there are usually minimal differences in FRC measured by gas dilution/washout techniques and plethysmography. However, in patients with lung disease associated with gas trapping, most, but not all, studies indicate that FRC using plethysmography often exceeds the FRC measured by gas dilution. An official technical statement of the American Thoracic Society approved October 2017 recommends adherence to the 2005 ATS/ERS guidelines for the measurement of lung volumes including body plethysmography. (14)

According to UpToDate, (15) “body plethysmography is the gold standard for measurement of lung volumes, particularly in the setting of significant airflow obstruction. Alternative methods include helium dilution, nitrogen washout, and measurements based on chest imaging. Helium dilution and nitrogen washout may underestimate lung volume in patients with moderate to severe [chronic obstructive pulmonary disease] COPD because they do not access under or nonventilated areas. Measurements of total lung capacity (TLC) using the chest radiograph or high resolution computed tomography (HRCT) correlate within 15 percent of those obtained by body plethysmography. Since the TLC is equivalent to the amount of air seen in the lungs on a chest radiograph taken at maximal inspiration, it is important that the subject inhales maximally as the image is created.”

Summary of Evidence

Despite body plethysmography having been considered a gold standard for measurement of lung volumes, there are scant clinical trial outcomes available for review. Plethysmographic methods need to be validated in randomized, controlled, clinical studies that include long term outcome measures to evaluate the clinical effectiveness in the diagnosis of venous and arterial diseases. Primarily the evidence to support coverage is based upon professional guidelines, such as the American Association for Respiratory Care, and the current summary and recommendations from UpToDate. Therefore, plethysmography is considered medically necessary when meeting specific indications to complete pulmonary function testing.

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CODING:

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Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.

The presence or absence of procedure, service, supply, device or diagnosis codes in a Medical Policy document has no relevance for determination of benefit coverage for members or reimbursement for providers. Only the written coverage position in a medical policy should be used for such determinations.

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The Centers for Medicare and Medicaid Services (CMS) does have a national Medicare coverage position.

A national coverage position for Medicare may have been changed since this medical policy document was written. See Medicare's National Coverage at <http://www.cms.hhs.gov>.

1. FDA – 510 (k) Premarket Notification – Sonamet Body Composition Analyzer. Food and Drug Administration – Center for Devices and Radiologic Health (2006). Available at <https://accessdata.fda.gov> (accessed – 2018 March 2).

2. FDA – 510 (k) Premarket Notification – Modified - Sonamet Body Composition Analyzer. Food and Drug Administration – Center for Devices and Radiologic Health (2004). Available at <https://accessdata.fda.gov> (accessed – 2018 March 2).

3. Heijboer H, Buller H, Lensing AW, et al. A comparison of real-time compression ultrasonography with impedence plethysmography for the diagnosis of deep-vein thrombosis in symptomatic outpatients. N Engl J Med. Nov 4 1993; 329:1365-9. PMID 8413431

4. Plethysmography: Safety, Effectiveness, and Clinical Utility in Diagnosing Vascular Disease – Technology Assessment (Archived). Prepared by the Agency for Health Care Policy and Research/Center for Health Care Technology Chicago (1996). Available at <https://www.archive.ahrq.gov> (accessed – 2018 March 2).

5. Shoemaker WC, Belzberg H, Wo CC, et al. Multicenter study of non-invasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients. Chest. Dec 1998; 114:1643-52. PMID 9872201

6. Venous Thrombus Cardiovascular Disorders: Peripheral Vascular Disorders. Kenilworth, New Jersey: Merck Manual (1999); 1792-5.

7. Kraemer R, Blum A, Schibler A, et al. Ventilation in homogeneities of specific airway resistance in young children. Amer J Respir Criti Care Med. Feb 15 2005; 171(4):371-8. PMID 15531750

8. Bisgaard H, Nielsen KG. Plethysmographic measurements of specific airway resistance in young children. Chest. Jul 2005; 128(1):355-62. PMID 16002957

9. Thomas MR, Rafferty GF, Blowes R, et al. Plethysmograph and interpreter resistance measurements in prematurely born young children. Arch Dis Child Fetal Neonatal Ed. May 2006; 91(3):F193-6. PMID 16239293

10. Bubb KS. Venous Insufficiency. eRadimaging. Mar 15 2011; 1-16. Available at <http://www.eradimaging.com> (accessed - 2011 March 10).

11. Blonshine S, Foss C, Mottram C, et al. American Association for Respiratory Care (AARC) Clinical Practice Guidelines. Body Plethysmography: 2001 Revision & Update. Respir Care. May 2001; 46(5):506-13.

12. ClinicalTrials.gov. U.S. National Library of Medicine. Body Plethysmography. Available at <https://clinicaltrials.gov> (accessed - 2018 February 26).

13. Wanger J, Clausen JL, Coates A, et al. Standardisation of lung function testing. Eur Respir J. Sep 2005; 26(3):511-22. PMID 16135736

14. Culver BH, Graham BL, Coates AL, et al. Recommendations for a Standardized Pulmonary Function Report. An Official American Thoracic Society Technical Statement. Am J Respir Crit Care Med. Dec 1 2017; 196(11):1463-1472. PMID 29192835

15. McCormack M, Stroller JK, Hollingsworth H. Overview of pulmonary function testing in adults (Nov 2016). In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. Available at <http://www.uptodate.com> (accessed - 2016 December 12).