2027 ICD-10-CM Diagnosis Code T70.3XXACaisson disease [decompression sickness], initial encounter

ICD-10-CM Codes›S00–T88›T66-T78›T70

ICD-10-CM T70.3XXA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T70.3XXA is a billable ICD-10-CM diagnosis code for caisson disease [decompression sickness], initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 922 through 923. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 4 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, initial encounter.

Code Identity

ICD-10-CM Code
T70.3XXA
Billable Status
Yes — Valid for Submission
Code Describes
Caisson disease [decompression sickness], initial encounter
Short Description
Caisson disease [decompression sickness], initial encounter
Same as the full description in the CMS dataset.
Parent Code
T70.3
Caisson disease [decompression sickness]

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT66-T78Other and unspecified effects of external causes
CategoryT70Effects of air pressure and water pressure
This CodeT70.3XXACaisson disease [decompression sickness], initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bends
  • Brown-Séquard syndrome due to decompression sickness
  • Cardiovascular decompression injury
  • Cerebellar decompression injury
  • Cerebral decompression injury
  • Cutaneous bends
  • Decompression sickness type I
  • Decompression sickness type II
  • Diving barotrauma
  • Musculoskeletal decompression sickness
  • Osteonecrosis due to Caisson disease
  • Pulmonary barotrauma
  • Pulmonary decompression injury
  • Spinal cord decompression injury
  • Visceral decompression injury

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Effects of air pressure and water pressure (T70). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to T70.3XXA: its own notes plus those printed at T70, block T66-T78, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block T66-T78 Other and unspecified effects of external causes applies to 456 codes
  • if applicable, place of occurrence, such as:
  • highway rest stop (Y92.523)
  • school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
  • service areas as the place of occurrence of the external cause (Y92.52-)
  • single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
  • transport vehicle as the place of occurrence of the external cause (Y92.81-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From T70 Effects of air pressure and water pressure applies to 24 codes
  • The appropriate 7th character is to be added to each code from category T70
Values for category T70 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name T70.3XXA, its category, or a range that includes it.

Code First 1

These codes say to code first a condition named in the note, and T70.3XXA is one of the conditions named.

  • M90.5 Osteonecrosis in diseases classified elsewhere
    caisson disease (T70.3) names T70.3, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ021
Effect of other external causes, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Decompression Sickness

    a condition occurring as a result of exposure to a rapid fall in ambient pressure. gases, nitrogen in particular, come out of solution and form bubbles in body fluid and blood. these gas bubbles accumulate in joint spaces and the peripheral circulation impairing tissue oxygenation causing disorientation, severe pain, and potentially death.

Patient EducationClinical

Barotrauma

Barotrauma means injury to your body because of changes in barometric (air) or water pressure. One common type happens to your ear. A change in altitude may cause your ears to hurt. This can happen if you are flying in an airplane, driving in the mountains, or scuba diving.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T70.3XXA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
993.3 Caisson disease
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About T70.3XXAOverview

What is the ICD-10 code for caisson disease [decompression sickness], initial encounter?

The ICD-10-CM code for caisson disease [decompression sickness], initial encounter is T70.3XXA (sometimes written as T703XXA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T70.3XXA (Caisson disease [decompression sickness]) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report caisson disease [decompression sickness], initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T70.3XXA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for caisson disease [decompression sickness], such as an emergency visit or first evaluation.

What MS-DRG does T70.3XXA group to?

When caisson disease [decompression sickness], initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 923, 922, with relative weights from 0.9980 to 1.6248 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T70.3XXA a CC or MCC?

CMS lists T70.3XXA as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 4 closely related codes in its exclusion list.