2027 ICD-10-CM Diagnosis Code T70.29XAOther effects of high altitude, initial encounter

ICD-10-CM Codes›S00–T88›T66-T78›T70

ICD-10-CM T70.29XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T70.29XA is a billable ICD-10-CM diagnosis code for other effects of high altitude, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Effect of other external causes, initial encounter.

Code Identity

ICD-10-CM Code
T70.29XA
Billable Status
Yes — Valid for Submission
Code Describes
Other effects of high altitude, initial encounter
Short Description
Other effects of high altitude, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T70.29
Other effects of high altitude

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 CodeT70.29XAOther effects of high altitude, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute mountain sickness
  • Aerodontalgia
  • Anoxia caused by high altitude
  • Barotrauma
  • Barotrauma of ascent
  • Barotrauma of descent
  • Bends
  • Chronic mountain sickness
  • Decompression sickness type II
  • Ebullism
  • Effects of air pressure
  • Effects of high altitude
  • Erythrocytosis caused by low atmospheric pressure
  • Erythrocytosis due to tissue hypoxemia
  • Finding of sensation of tooth
  • Gastrointestinal barotrauma
  • Headache caused by high altitude
  • High altitude pulmonary edema
  • High altitude retinopathy
  • Local pressure effects
  • Pulmonary barotrauma
  • Pulmonary hypertension caused by low air pressure due to chronic exposure to high altitude
  • Pulmonary hypertension due to lung disease and/or hypoxia
  • Subacute mountain sickness
  • Toothache
  • 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 T70.29XA: its own notes plus those printed at T70.2, 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 T70.2 Other and unspecified effects of high altitude applies to 6 codes
  • polycythemia due to high altitude (D75.1)
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 T70.29XA, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming T70.29XA: they are not reported together with it, unless the two conditions are unrelated.

  • T71 Asphyxiation
    anoxia due to high altitude (T70.2) names T70.2, 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

  • Barotrauma

    injury following pressure changes; includes injury to the eustachian tube, ear drum, lung and stomach.

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 T70.29XA to ICD-9-CMHistory

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

ICD-9-CM
993.2 Eff high altitud NEC/NOS
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 T70.29XAOverview

What is the ICD-10 code for other effects of high altitude, initial encounter?

The ICD-10-CM code for other effects of high altitude, initial encounter is T70.29XA (sometimes written as T7029XA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T70.29XA (Other effects of high altitude) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other effects of high altitude, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T70.29XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for other effects of high altitude, such as an emergency visit or first evaluation.

What MS-DRG does T70.29XA group to?

When other effects of high altitude, 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.

What is the ICD-9 equivalent of T70.29XA?

Under the General Equivalence Mappings, other effects of high altitude, initial encounter converts to ICD-9-CM 993.2 (eff high altitud NEC/NOS). The mapping is approximate, so confirm the match fits the documentation.