Airways, lungs and breathing

Where you are

A respiratory record can describe an airway, lung tissue, the membrane around a lung, or a symptom of breathing difficulty. Your first job is to identify which structure or finding the author actually named. This lesson builds the map you will use when studying respiratory diagnoses and procedures.

Keep two notebook columns: anatomy and documentation. In the first, draw and label structures. In the second, record the exact words that a coding exercise supplies. Connecting the columns will help you distinguish what you know about the body from what this particular record establishes.

Follow the air

Air enters through the nose or mouth, passes toward the larynx and trachea, and reaches the bronchi. The bronchi branch into smaller bronchioles within the lungs. At the ends of the branching route are tiny air sacs called alveoli. [lungs-nhlbi]

The trachea divides into right and left primary bronchi. As the airways branch, their walls change. Smaller passages have less supporting cartilage; the smallest bronchioles lack it. The thin walls near the alveoli support gas exchange with nearby capillaries. [anatomy-airways]

Draw this as a branching route, leaving space beside each label. Do not draw the pleural cavity as the next tube after a bronchiole. It belongs in a different part of your map.

Now practice reading three fictional location phrases: “tracheal finding,” “left main bronchus,” and “right lung.” Each narrows the location differently. Copy the most specific supplied phrase instead of replacing all three with “chest.” You are preserving evidence that a later procedure or diagnosis lookup may need.

Air movement and gas exchange

Ventilation means moving air into and out of the lungs. During inspiration, the diaphragm contracts, the chest cavity expands, and the pressure change draws air inward. During ordinary expiration, relaxation and elastic recoil help air move outward. [anatomy-ventilation]

Gas exchange concerns oxygen moving from air into blood and carbon dioxide moving from blood into the air to be exhaled. The respiratory and circulatory systems therefore work together, but moving air and transporting blood are different processes. [lungs-nhlbi]

Use two arrows in your notebook: one along the airway and another between an air sac and a nearby blood vessel. Label the first ventilation and the second gas exchange. The arrows explain the relationship without requiring you to memorize a long definition.

For a coding exercise, physiological knowledge helps you understand the record. It does not authorize you to diagnose respiratory failure from a number, a device, or a description of effort. Find the documented assessment and apply the relevant coding instructions. [icd-guidelines, I.A.19]

Lung, lobe and pleura

The right lung has three lobes; the left has two. Each lung is surrounded by pleura. Visceral pleura covers the lung surface, while parietal pleura lines the thoracic wall. The small pleural space between them contains lubricating fluid. [anatomy-airways]

Add a border around each lung in your sketch. Label the lung itself separately from the pleural space. This gives you a way to explain why a record about fluid in that space and a record about a finding within lung tissue describe different locations.

Later procedure questions may distinguish the structure examined or treated, the approach, and the work performed. Begin with three blank fields: target, route, action. Fill them only from the operative report. A procedure name alone may not answer all three.

Three disease concepts

Asthma is a chronic airway condition in which inflammation and narrowing can restrict airflow. Its symptoms can vary and worsen during an attack. This basic definition explains the airway connection; the full diagnosis and its documented detail still matter for coding. [asthma-nhlbi]

Pneumonia is an infection affecting one or both lungs. It can involve fluid or pus in the alveoli, and different organisms can cause it. Knowing that several causes exist is a reason to read the documented diagnosis carefully, not to select an organism by guesswork. [pneumonia-nhlbi]

COPD stands for chronic obstructive pulmonary disease. Damage to airways or other lung structures restricts airflow. Emphysema involves damage to air-sac walls; chronic bronchitis involves persistent airway irritation and inflammation. These concepts help you understand the record, but classification requires the actual diagnoses and applicable instructions. [copd-nhlbi]

Make three short entries in your notebook. Beside each condition, write the structure or process that helps you remember its meaning. Leave coding categories for the later diagnosis lessons. The purpose here is to understand language before using the classification.

Worked example: preserve certainty

Original fictional office excerpt, August 26, 2026: the patient is evaluated for a cough. The clinician documents “cough; possible pneumonia,” orders further testing, and has not established a definitive diagnosis at the end of this encounter.

Separate the symptom from the uncertain explanation. In outpatient coding, a diagnosis stated as possible is not coded as though established. Report to the highest degree of certainty for that encounter, following the applicable instructions. [icd-guidelines, IV.H]

Write two sentences: “The record establishes cough.” “The record does not establish pneumonia.” Then identify the main term you would investigate in the Alphabetic Index and verify the candidate in the Tabular List. Do not supply a duration or subtype that the excerpt omits. [icd-guidelines, I.B.1; IV.F]

Change one fact: the final assessment now establishes pneumonia but does not identify an organism. The uncertainty problem has changed, but the missing-organism problem remains. Do not infer a bacterial cause from a medication list. Read the complete assessment and classification instructions before choosing an entry.

Book drill

Find an index route for cough and another for pneumonia. Follow each route into the Tabular List. Record which additional documentation could change your selection. Keep your notes about index navigation separate from any diagnosis you might expect clinically.

In your own CPT book, locate the respiratory surgery section and its introductory guidance. Identify how the section organizes structures and approaches. Read the relevant instructions in your licensed book; this course does not reproduce its descriptors. You are learning where to look before attempting procedure selection.

Common traps

Keep bronchi, bronchioles and alveoli distinct. Do not place pleural fluid inside an airway. Do not exchange a lung with a lobe. Do not turn a symptom into a confirmed disease or infer a disease subtype from a treatment. Preserve the record's anatomical detail and certainty together.

Practice

1. What is the difference between ventilation and gas exchange?

2. Is the pleural space part of the branching airway route?

3. In the fictional office excerpt, what prevents coding possible pneumonia as established?

Compare your reasoning

1. Ventilation moves air; gas exchange transfers oxygen and carbon dioxide between air and blood. 2. No. It lies between the pleural layers around a lung. 3. The assessment remains uncertain in an outpatient encounter; apply the outpatient certainty rule.

Checkpoint

Draw the airway route and add a separate pleural border. Explain where gas exchange occurs. For the fictional excerpt, distinguish the supported finding from an uncertain diagnosis and an undocumented organism. Finish by locating the two diagnosis routes in your book.

Sources

1. NCI SEER — Bronchi, bronchial tree and lungs. 2026. Accessed 2026-09-10.
2. NCI SEER — Mechanics of ventilation. 2026. Accessed 2026-09-10.
3. NHLBI — The respiratory system. 2026. Accessed 2026-09-10.
4. NHLBI — What is asthma?. 2026. Accessed 2026-09-10.
5. NHLBI — What is pneumonia?. 2026. Accessed 2026-09-10.
6. NHLBI — What is COPD?. 2026. Accessed 2026-09-10.
7. CDC/NCHS and CMS — ICD-10-CM April 1 2026 Guidelines. FY2026 April. Accessed 2026-09-10.