Total Body Plethysmography

Number: 0474

Policy

Aetna considers total body plethysmography medically necessary as an adjunct to complete pulmonary function testing (including residual volumes and diffusion) for any of the following indications:

• For determination of bronchial hyper-reactivity in response to methacholine, histamine, or isocapnic hyperventilation; or
• For determination of response to bronchodilators in persons who show a clinical response but fail to show an improvement in forced expiratory volume in 1 second (FEV1) by spirometry; or
• 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 nitrogen washout; or
• For evaluation of resistance to airflow in persons with obstructive processes, where plethysmography is necessary for accurate calculation of true lung volumes; or
• For measurement of lung volumes to distinguish between restrictive and obstructive processes, where a restrictive process is suggested by a low vital capacity (less than 80 % predicted) on a spirometry test; or
• For measurement of lung volumes when multiple repeated trials are required, or when the subject is unable to perform multi-breath tests.

Aetna considers total body plethysmography experimental and investigational for all other indications including the following (not an all-inclusive list):

• Early detection of chronic obstructive pulmonary disease
• Pectus excavatum
• Primary pulmonary hypertension
• Prior to initiation of bleomycin therapy and during therapy to monitor drug toxicity
• Scoliosis
• Systemic sclerosis.

Background

This policy is based on the American Academy of Respiratory Care (AARC, 1994) Clinical Practice Guideline on Body Plethysmography.  Body plethysmography is a very sensitive lung measurement used to detect lung pathology that might be missed with conventional pulmonary function tests.

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 the functional residual capacity [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 increase in their chest volume slightly reduces the box volume and thus slightly increases the pressure in the box.  The most common measurements made using the body plethysmograph are thoracic gas volume (TGV) and airways resistance (Raw).  Airways conductance (Gaw) is also commonly calculated as the reciprocal of Raw.  Specific airways conductance (i.e., conductance/unit of lung volume) is routinely reported as SGaw.  Other tests that can be measured in the body plethysmograph include spirometry, bronchial challenge, diffusing capacity, single-breath nitrogen (N2), multiple-breath N2 washout, pulmonary compliance, occlusion pressure, and cardiac output, including pulmonary blood flow.

The American Academy of Respiratory Care's guidelines base their recommendations for body plethysmography on the test's advantages as compared with gas dilution techniques.

Lung volumes provide useful information that confirms the presence of restrictive lung disease suggested by a low vital capacity on a spirometry test.  Both plethysmography and gas dilution techniques measure the FRC, the residual air in the lung at the end of exhalation during tidal breathing.  This value is not obtainable with spirometry.

Unlike gas dilution tests (e.g., helium dilution and nitrogen wash-out techniques), body plethysmography has the ability to measure non-communicating or poorly communicating air spaces such as blebs or bullae, which usually are present in conditions involving air trapping such as cystic fibrosis or bullous emphysema.  Thus, plethysmography is preferred over gas dilution techniques in measuring lung volumes in obstructive conditions, when air trapping may occur, or where there is co-existing restriction and obstruction.

In addition to this advantage, body plethysmography allows multiple determinations of lung volumes to be made rapidly.

Although determination of the response to bronchodilators is a listed indication for body plethysmography based on the AARC guidelines, spirometry is the standard of care for evaluating response to bronchodilators.  Airflow limitation from asthma should usually demonstrate some degree of reversibility following acute treatment with a beta-agonist.  The currently recommended criteria for a significant response to a bronchodilator in adults are that either forced vital capacity (FVC) or forced expiratory volume in 1 second (FEV1) should increase by 12 % and by at least 200 ml, although complete consensus on this is lacking.  In patients with baseline airflow limitation, failure to improve following bronchodilator administration suggests an alternate diagnosis (e.g., chronic obstructive pulmonary disease) or airways inflammation that requires additional therapy (e.g., glucocorticoids).  It has also been suggested that clinicians measure other parameters of airflow obstruction in addition to spirometry, such as specific airway conductance (SGaw) obtained with a plethysmograph.  This approach increases the likelihood of observing airflow reversibility.  If a patient fails to show an improvement in FEV1 with albuterol treatment and a clinical response appears to occur, body plethysmography can be used to document this change.

Patients with mild or no airflow limitation may not show reversal after bronchodilator administration.  In such cases, a bronchial challenge with inhaled methacholine, histamine or other agents would be indicated to demonstrate reversible airflow obstruction.  Although response to bronchial challenge can be assessed by measurement of FEV1 with spirometry, it has been reported that sensitivity is increased by measurements of changes in FVC, SGaw, and TGV.  This result is in keeping with the known axial heterogeneity of the response of airways of difference caliber to bronchoactive agents.

Airway resistance can be measured directly using whole-body plethysmography, but is more commonly inferred from spirometric measurements of dynamic lung volumes and expiratory flow rates, which can be obtained more easily.  Airways resistance (Raw) and Gaw, the reciprocal of Raw, provide an effort independent measure of airway status.  They are a more sensitive measurement and will detect airways disease earlier than forced expiratory flow with spirometry.

Guidelines from the American Thoracic Society (Crapo, et al., 2000) recommend the use of spirometry for methacholine challenge testing (MCT), with body plethysmography reserved for persons who cannot perform spirometry. Regarding body plethysmography, the guidelines state: "Measures of airway resistance (Raw), usually expressed as specific conductance (sGaw), are alternative end points for MCT but should be used primarily in patients who cannot perform acceptable spirometry maneuvers. In patients with asthma and COPD, changes in Raw usually parallel changes in FEV1 with MCT, but both Raw and sGaw are more variable than FEV1."

According to the guideline on body plethysmography provided by the AARC (2001), the frequency with which plethysmography is repeated should depend on the clinical question(s) to be answered.

Vassallo and Trohman (2007) evaluated and synthesized evidence regarding optimal use of amiodarone for various arrhythmias.  The authors performed a systematic search of MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other studies with clinical pertinence.  The search was limited to human-participant, English-language reports published between 1970 and 2007.  Amiodarone was searched using the terms adverse effects, atrial fibrillation, atrial flutter, congestive heart failure, electrical storm, hypertrophic cardiomyopathy, implantable cardioverter-defibrillator, surgery, ventricular arrhythmia, ventricular fibrillation, and Wolff-Parkinson-White.  Bibliographies of identified articles and guidelines from official societies were reviewed for additional references.  A total of 92 identified studies met inclusion criteria and were included in the review.  Amiodarone may have clinical value in patients with left ventricular dysfunction and heart failure as first-line treatment for atrial fibrillation, though other agents are available.  Amiodarone is useful in acute management of sustained ventricular tachyarrythmias, regardless of hemodynamic stability.  The only role for prophylactic amiodarone is in the peri-operative period of cardiac surgery. Amiodarone may be effective as an adjunct to implantable cardioverter-defibrillator therapy to reduce number of shocks. However, amiodarone has a number of serious adverse effects, including corneal microdeposits (greater than 90%), optic neuropathy/neuritis (less than or equal to 1 % to 2 %), blue-gray skin discoloration (4 % to 9 %), photosensitivity (25 % to 75 %), hypothyroidism (6 %), hyperthyroidism (0.9 % to 2 %), pulmonary toxicity (1 % to 17 %), peripheral neuropathy (0.3 % annually), and hepatotoxicity (elevated enzyme levels, 15 % to 30 %; hepatitis and cirrhosis, less than 3 % [0.6 % annually]).  The authors concluded that amiodarone should be used with close follow-up in patients who are likely to derive the most benefit, namely those with atrial fibrillation and left ventricular dysfunction, those with acute sustained ventricular arrhythmias, those about to undergo cardiac surgery, and those with implantable cardioverter-defibrillators and symptomatic shocks.  This study did not mention the use of plethysmography in patients taking amiodarone.

An UpToDate review on “Bleomycin-induced lung injury” (Gilligan, 2013) states that “The use of pulmonary function tests, particularly the diffusion capacity (DLCO), to screen for early evidence of pulmonary toxicity is controversial.  We do not routinely order pulmonary function tests in patients prior to administering bleomycin or during therapy to screen for lung toxicity”.

Monitoring and Predicting Asthma in Children

Korten and colleagues (2019) stated that there is a lack of agreement among measures of asthma control in children.  In Central Europe, body plethysmography is additionally used for asthma monitoring.  However, its value is still unclear.  These investigators examined the possible additional value of body plethysmographic measures (specific resistance, residual volume-total lung capacity ratio [RV/TLC]) compared with spirometric measures forced expiratory volume in 1 second (FEV 1 ), forced vital capacity (FVC), FEV 1 /FVC, forced expiratory flow at 25 % to 75 % of FVC (FEF 25-75), and fraction of exhaled nitric oxide (FeNO) for assessment of asthma control.  A total of 145 asthmatic children aged 5 to 17 were included in this trial.  All subjects performed measurements of FeNO, spirometry, and body plethysmography.  Asthma control was assessed by the asthma control test (c-ACT/ACT) and a doctor's assessment of asthma control.  Investigating single lung function parameters, FEV1 , FEV 1 /FVC, FEF 25-75 and RV/TLC differed between controlled and partly controlled asthma.  However, these researchers found no differences between controlled and uncontrolled asthma with regard to single lung function parameters or for any parameter if examined in a multi-variable approach.  This was also true if these investigators combined obtained parameters from spirometry (comparing pathologic versus normal spirometry).  Examining the combination of body plethysmography and doctor's assessment of asthma control a significant association was found (p = 0.02).  Furthermore, combined spirometry and body plethysmography showed a significant association with both doctor's assessed asthma control (p = 0.009) and the c-ACT/ACT (p = 0.04).  The addition of FeNO did not improve the results.  The authors concluded that the combination of body plethysmography and spirometry showed best agreement with asthma control in children compared with spirometry or body plethysmography alone.  Moreover, these researchers stated that further studies are needed to determine if additional measurements of body plethysmography improve the outcome of children in asthma monitoring.

Elenius and colleagues (2021) noted that pre-school wheeze is highly prevalent; 30 % to 50 % of children have wheezed at least once before age 6.  Wheezing is not a disorder; it is a symptom of obstruction in the airways, and it is essential to identify the correct diagnosis behind this symptom.  An increasing number of studies provided evidence for novel diagnostic tools for monitoring and predicting asthma in the pediatric population.  Several techniques are available to measure airway obstruction and airway inflammation, including spirometry, impulse oscillometry (IOS), total-body plethysmography, bronchial hyper-responsiveness test, multiple breath washout test, measurements of exhaled nitric oxide (NO), as well as analyses of various other biomarkers.  These investigators systematically reviewed all the existing techniques available for measuring lung function and airway inflammation in pre-school children to examine their potential and clinical value in the routine diagnostics and monitoring of airway obstruction.  If applicable, measuring FEV1 using spirometry is considered useful.  For those unable to carry out spirometry, total-body plethysmography and IOS may be useful.  Bronchial reversibility to beta2-agonist and hyper-responsiveness test with running exercise challenge may improve the sensitivity of these tests.  The authors concluded that difficulty of measuring lung function and the lack of large randomized controlled trials (RCTs) made it difficult to establish guidelines for monitoring asthma in pre-school children.

Furthermore, UpToDate reviews on “An overview of asthma management” (Fanta, 2021) and “Asthma in children younger than 12 years: Initiating therapy and monitoring control” (Sawicki and Haver, 2021) do not mention total body plethysmography as a management option.

Early Detection of Chronic Obstructive Pulmonary Disease

Gupta and colleagues (2018) noted that chronic obstructive pulmonary disease (COPD) is the 4th most common cause of death in the world, for which smoking is a common cause.  It is preferable to diagnose COPD at an earlier stage and to assess its progression so that mortality and morbidity of the disease could be reduced.  In a comparative, randomized, cross-sectional study,, these researchers evaluated parameters of body plethysmography in Indian population where the data are lacking and examined if the use of body plethysmography can detect COPD earlier.  Healthy control subjects (CN), smokers without COPD diagnosis (SM) who were smoking for more than 5 pack-years and smokers with COPD who were further classified depending upon GOLD criteria as mild COPD (C1), moderate COPD (C2), and severe COPD (C3) (n = 30 each group) were considered.  All the participants were men who gave written informed consent.  Subject underwent routine spirometry (FEV1, FVC, FEV1/FVC, PEFR, and FEF25-75%) along with body plethysmography where sGaweff, sGawtot, residual volume (RV), total lung capacity (TLC), and inspiratory capacity (IC) were recorded.  The differences in lung function were compared between healthy controls and smokers and also between the 3 groups of COPD severity (GOLD guidelines) employing univariate analysis of variance and Bonferroni's post-hoc test.  Spirometry could not differentiate between smokers without COPD and healthy controls.  However, 3 parameters on body plethysmography (IC, sGawtot, and sGaweff) were sensitive enough to detect differences between smokers without COPD and healthy controls.  The authors concluded that using body plethysmography, the vexed question troubling the clinician, which of the smokers progress to COPD and who do not before they develop irreversible changes can perhaps be answered if further large-scale multi-center studies and long-term follow-up studies confirm the findings in this study.

Table: CPT Codes / HCPCS Codes / ICD-10 Codes

Code	Code Description
Information in the [brackets] below has been added for clarification purposes.   Codes requiring a 7th character are represented by "+":
CPT codes covered if selection criteria are met:
94726	Plethysmography for determination of lung volumes and, when performed, airway resistance
Other CPT codes related to the CPB:
94010 - 94070	Spirometry
Other HCPCS codes related to the CPB:
J9040	Injection, bleomycin sulfate, 15 units
ICD-10 codes covered if selection criteria are met (not all-inclusive):
D86.0 - D86.9	Sarcoidosis
E84.0 - E84.9	Cystic fibrosis
J09.X1 - J22 J40 - J99	Pneumonia and influenza, chronic obstructive pulmonary disease and allied conditions, pneumoconioses and other lung diseases due to external agents, and other diseases of respiratory system
ICD-10 codes not covered for indications listed in the CPB (not all inclusive):
I27.0	Primary pulmonary hypertension
M34.0 - M34.9	Systemic sclerosis (scleroderma)
M41.00 - M41.9	Scoliosis [includes kyphoscoliosis]
Q67.6	Pectus excavatum
Z51.81	Encounter for therapeutic drug level monitoring [bleomycin]

The above policy is based on the following references: