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Official Description

Respiratory flow volume loop

© Copyright 2025 American Medical Association. All rights reserved.

Common Language Description

The CPT® Code 94375 refers to a diagnostic procedure known as the respiratory flow volume loop. This test is a graphical representation that plots the flow of air during inhalation and exhalation against the volume of air exchanged, providing valuable insights into a patient's respiratory function. The X-axis of the graph represents the flow of air, while the Y-axis indicates the volume of air. This visual representation is crucial for assessing the effort and strength of a patient's breathing, as well as the movement of air through the respiratory system. The respiratory flow volume loop is instrumental in identifying specific patterns of obstruction in both the upper and lower airways, which can aid in the diagnosis of various pulmonary diseases. During the test, the patient is required to obstruct their nose and use a mouthpiece connected to a measuring device. The patient inhales deeply and then exhales forcefully into the device, allowing for the collection of data that is subsequently reported in two forms: a volume-time curve and a flow-volume curve. The results of the flow volume loop can reveal significant information about the presence of obstructive lung diseases, such as chronic obstructive pulmonary disease (COPD) and asthma, which typically present a concave shape on the flow-volume loop due to the obstruction of large airways that slows down the exhalation of air. In contrast, restrictive lung diseases usually display a normal-shaped flow-volume loop, albeit with a reduced total volume of air exchanged. Additionally, mixed type lung diseases may show various shapes on the flow-volume loop, indicating a combination of obstructive and restrictive patterns. Furthermore, the respiratory flow volume loop can help identify other respiratory issues, including large airway obstructions caused by conditions such as vocal cord paralysis, goiter, tumors in the trachea or larynx, and tracheal stenosis resulting from intubation. This comprehensive understanding of the respiratory flow volume loop is essential for healthcare professionals in diagnosing and managing respiratory conditions effectively.

© Copyright 2025 Coding Ahead. All rights reserved.

1. Indications

The respiratory flow volume loop (CPT® Code 94375) is indicated for use in various clinical scenarios where assessment of airway function is necessary. The following conditions and symptoms may warrant the performance of this procedure:

  • Obstructive Lung Disease - Conditions such as chronic obstructive pulmonary disease (COPD) and asthma, where airflow obstruction is present.
  • Restrictive Lung Disease - Situations where lung volume is reduced, but airflow is typically normal, necessitating evaluation of lung capacity.
  • Mixed Type Lung Disease - Cases where both obstructive and restrictive patterns are suspected, requiring detailed analysis of airflow dynamics.
  • Large Airway Obstruction - Symptoms indicating potential obstructions in the upper airways, such as vocal cord paralysis, goiter, or tumors in the trachea and larynx.
  • Tracheal Stenosis - Conditions resulting from intubation or other factors that may lead to narrowing of the trachea, affecting airflow.

2. Procedure

The procedure for conducting a respiratory flow volume loop involves several key steps to ensure accurate measurement and data collection. The following outlines the procedural steps:

  • Preparation of the Patient - The patient is instructed to sit comfortably and is provided with a mouthpiece connected to the measuring device. It is essential that the patient's nose is obstructed to ensure that all airflow is directed through the mouthpiece during the test.
  • Inhalation Phase - The patient is asked to inhale deeply through the mouthpiece, filling their lungs to maximum capacity. This step is crucial as it establishes the baseline volume for the subsequent exhalation.
  • Exhalation Phase - Following a deep inhalation, the patient is instructed to exhale forcefully and rapidly into the device. This phase is critical for capturing the flow of air as it exits the lungs, allowing for the assessment of both inspiratory and expiratory airflow.
  • Data Collection - As the patient exhales, the device records the airflow and volume data, which is then plotted to create the flow-volume loop. This data is typically presented in two formats: a volume-time curve and a flow-volume curve, providing a comprehensive view of the patient's respiratory function.
  • Completion of the Test - Once the data has been collected, the patient may be instructed to rest and breathe normally. The healthcare provider will then analyze the flow-volume loop to identify any patterns indicative of respiratory conditions.

3. Post-Procedure

After the respiratory flow volume loop procedure is completed, the patient may resume normal activities immediately, as there are typically no significant post-procedure restrictions. However, healthcare providers may advise patients to monitor for any unusual symptoms, such as shortness of breath or discomfort, following the test. The collected data will be analyzed by the healthcare professional to determine the presence of any obstructive or restrictive lung diseases, and appropriate follow-up care or treatment plans will be discussed based on the results. It is essential for the healthcare provider to communicate the findings clearly to the patient and outline any necessary next steps in their care.

Short Descr RESPIRATORY FLOW VOLUME LOOP
Medium Descr RESPIRATORY FLOW VOLUME LOOP
Long Descr Respiratory flow volume loop
Status Code Active Code
Global Days XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC) 1 - Diagnostic Tests for Radiology Services
Multiple Procedures (51) 0 - No payment adjustment rules for multiple procedures apply.
Bilateral Surgery (50) 0 - 150% payment adjustment for bilateral procedures does NOT apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 0 - Payment restriction for assistants at surgery applies to this procedure...
Co-Surgeons (62) 0 - Co-surgeons not permitted for this procedure.
Team Surgery (66) 0 - Team surgeons not permitted for this procedure.
Diagnostic Imaging Family 99 - Concept Does Not Apply
APC Status Indicator STV-Packaged Codes
Type of Service (TOS) 5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS) T2D - Other tests - other
MUE 1
CCS Clinical Classification 38 - Other diagnostic procedures on lung and bronchus

This is a primary code that can be used with these additional add-on codes.

94729 Addon Code MPFS Status: Active Code APC N Diffusing capacity (eg, carbon monoxide, membrane) (List separately in addition to code for primary procedure)
26 Professional component: certain procedures are a combination of a physician or other qualified health care professional component and a technical component. when the physician or other qualified health care professional component is reported separately, the service may be identified by adding modifier 26 to the usual procedure number.
59 Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25.
GC This service has been performed in part by a resident under the direction of a teaching physician
XU Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service
GW Service not related to the hospice patient's terminal condition
TC Technical component; under certain circumstances, a charge may be made for the technical component alone; under those circumstances the technical component charge is identified by adding modifier 'tc' to the usual procedure number; technical component charges are institutional charges and not billed separately by physicians; however, portable x-ray suppliers only bill for technical component and should utilize modifier tc; the charge data from portable x-ray suppliers will then be used to build customary and prevailing profiles
GA Waiver of liability statement issued as required by payer policy, individual case
CR Catastrophe/disaster related
GZ Item or service expected to be denied as not reasonable and necessary
Q6 Service furnished under a fee-for-time compensation arrangement by a substitute physician or by a substitute physical therapist furnishing outpatient physical therapy services in a health professional shortage area, a medically underserved area, or a rural area
GV Attending physician not employed or paid under arrangement by the patient's hospice provider
PD Diagnostic or related non diagnostic item or service provided in a wholly owned or operated entity to a patient who is admitted as an inpatient within 3 days
XE Separate encounter, a service that is distinct because it occurred during a separate encounter
CC Procedure code change (use 'cc' when the procedure code submitted was changed either for administrative reasons or because an incorrect code was filed)
25 Significant, separately identifiable evaluation and management service by the same physician or other qualified health care professional on the same day of the procedure or other service: it may be necessary to indicate that on the day a procedure or service identified by a cpt code was performed, the patient's condition required a significant, separately identifiable e/m service above and beyond the other service provided or beyond the usual preoperative and postoperative care associated with the procedure that was performed. a significant, separately identifiable e/m service is defined or substantiated by documentation that satisfies the relevant criteria for the respective e/m service to be reported (see evaluation and management services guidelines for instructions on determining level of e/m service). the e/m service may be prompted by the symptom or condition for which the procedure and/or service was provided. as such, different diagnoses are not required for reporting of the e/m services on the same date. this circumstance may be reported by adding modifier 25 to the appropriate level of e/m service. note: this modifier is not used to report an e/m service that resulted in a decision to perform surgery. see modifier 57 for significant, separately identifiable non-e/m services, see modifier 59.
51 Multiple procedures: when multiple procedures, other than e/m services, physical medicine and rehabilitation services or provision of supplies (eg, vaccines), are performed at the same session by the same individual, the primary procedure or service may be reported as listed. the additional procedure(s) or service(s) may be identified by appending modifier 51 to the additional procedure or service code(s). note: this modifier should not be appended to designated "add-on" codes (see appendix d).
52 Reduced services: under certain circumstances a service or procedure is partially reduced or eliminated at the discretion of the physician or other qualified health care professional. under these circumstances the service provided can be identified by its usual procedure number and the addition of modifier 52, signifying that the service is reduced. this provides a means of reporting reduced services without disturbing the identification of the basic service. note: for hospital outpatient reporting of a previously scheduled procedure/service that is partially reduced or cancelled as a result of extenuating circumstances or those that threaten the well-being of the patient prior to or after administration of anesthesia, see modifiers 73 and 74 (see modifiers approved for asc hospital outpatient use).
53 Discontinued procedure: under certain circumstances, the physician or other qualified health care professional may elect to terminate a surgical or diagnostic procedure. due to extenuating circumstances or those that threaten the well being of the patient, it may be necessary to indicate that a surgical or diagnostic procedure was started but discontinued. this circumstance may be reported by adding modifier 53 to the code reported by the individual for the discontinued procedure. note: this modifier is not used to report the elective cancellation of a procedure prior to the patient's anesthesia induction and/or surgical preparation in the operating suite. for outpatient hospital/ambulatory surgery center (asc) reporting of a previously scheduled procedure/service that is partially reduced or cancelled as a result of extenuating circumstances or those that threaten the well being of the patient prior to or after administration of anesthesia, see modifiers 73 and 74 (see modifiers approved for asc hospital outpatient use).
56 Preoperative management only: when 1 physician or other qualified health care professional performed the preoperative care and evaluation and another performed the surgical procedure, the preoperative component may be identified by adding modifier 56 to the usual procedure number.
58 Staged or related procedure or service by the same physician or other qualified health care professional during the postoperative period: it may be necessary to indicate that the performance of a procedure or service during the postoperative period was: (a) planned or anticipated (staged); (b) more extensive than the original procedure; or (c) for therapy following a surgical procedure. this circumstance may be reported by adding modifier 58 to the staged or related procedure. note: for treatment of a problem that requires a return to the operating/procedure room (eg, unanticipated clinical condition), see modifier 78.
76 Repeat procedure or service by same physician or other qualified health care professional: it may be necessary to indicate that a procedure or service was repeated by the same physician or other qualified health care professional subsequent to the original procedure or service. this circumstance may be reported by adding modifier 76 to the repeated procedure or service. note: this modifier should not be appended to an e/m service.
79 Unrelated procedure or service by the same physician or other qualified health care professional during the postoperative period: the individual may need to indicate that the performance of a procedure or service during the postoperative period was unrelated to the original procedure. this circumstance may be reported by using modifier 79. (for repeat procedures on the same day, see modifier 76.)
95 Synchronous telemedicine service rendered via a real-time interactive audio and video telecommunications system: synchronous telemedicine service is defined as a real-time interaction between a physician or other qualified health care professional and a patient who is located at a distant site from the physician or other qualified health care professional. the totality of the communication of information exchanged between the physician or other qualified health care professional and the patient during the course of the synchronous telemedicine service must be of an amount and nature that would be sufficient to meet the key components and/or requirements of the same service when rendered via a face-to-face interaction. modifier 95 may only be appended to the services listed in appendix p. appendix p is the list of cpt codes for services that are typically performed face-to-face, but may be rendered via a real-time (synchronous) interactive audio and video telecommunications system.
99 Multiple modifiers: under certain circumstances 2 or more modifiers may be necessary to completely delineate a service. in such situations modifier 99 should be added to the basic procedure, and other applicable modifiers may be listed as part of the description of the service.
AQ Physician providing a service in an unlisted health professional shortage area (hpsa)
FS Split (or shared) evaluation and management visit
GN Services delivered under an outpatient speech language pathology plan of care
GY Item or service statutorily excluded, does not meet the definition of any medicare benefit or, for non-medicare insurers, is not a contract benefit
Q1 Routine clinical service provided in a clinical research study that is in an approved clinical research study
Q5 Service furnished under a reciprocal billing arrangement by a substitute physician or by a substitute physical therapist furnishing outpatient physical therapy services in a health professional shortage area, a medically underserved area, or a rural area
RT Right side (used to identify procedures performed on the right side of the body)
SA Nurse practitioner rendering service in collaboration with a physician
U7 Medicaid level of care 7, as defined by each state
XP Separate practitioner, a service that is distinct because it was performed by a different practitioner
XS Separate structure, a service that is distinct because it was performed on a separate organ/structure
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