Respiratory System

Pathway of Air

Nasal cavity → pharynx →larynx → trachea→Bronchi→Respiratory bronchi →Bronchioles→ Alveolar ducts→ Alveoli

Conducting vs. Respiratory Zone Chart

Structure Zone Epithelium Type Function

Trachea Conducting Pseudostratified ciliated columnar epithelium Air passage; mucus trapping

Bronchi Conducting Pseudostratified ciliated columnar epithelium Air distribution

Bronchioles Conducting Simple ciliated cuboidal epithelium Smooth muscle control of airflow

Alveolar sacs Respiratory Simple squamous epithelium Gas exchange

Lungs and Pleura

Left vs. Right Lungs

The right lung has three lobes; the left lung has two lobes and a cardiac notch.

Pleural Membranes

The parietal pleura lines the chest wall; the visceral pleura covers the lung.

Pleural Function

Creates intrapulmonary pressure to keep lungs expanded.

If Damaged/Infected:

Pleurisy (inflammation) or pleural effusion(fluid accumulation).
Pleurisy causes chest pain, while pleural effusion may impair breathing.

Disorders

Pneumothorax

Air enters pleural space → lung collapse
Decreased ventilation on affected side
Treatment: With equipment: needle decompression or chest tube. Without equipment: Puncturing the lung to equalize pressure

Atelectasis

Alveoli collapse due to compression or obstruction
Reduced gas exchange
Treatment: Deep breathing, bronchiodilator medications

Gas Laws

Law Statement Clinical Example

Boyle’s Law Pressure ↑ → Volume ↓ Explains inspiration/exhalation

Dalton’s Law Each gas exerts a partial pressure Oxygen and CO₂ diffusion

Henry’s Law Gas dissolves based on partial pressure Oxygen exchange at alveoli

and solubility coefficient

Spirometry

Tidal Volume (TV)

Definition: Amount of air per breath
Normal value: ~500
Helps in maintaining adequate gas exchange

Inspiratory Reserve (IRV)

Definition: The extra air you can forcefully inhale after a normal, quiet breath
Normal value: ~3100
Helps assess lung functions and respiratory conditions

Expiratory Reserve (ERV)

Definition: Extra air that can be forcefully exhaled after a normal, quiet breath
Normal value: ~1200
Aids in assessing lung function and diagnosing diseases

Residual Volume (RV)

Definition: The amount of air that remains in the lungs after a forceful exhalation
Normal value: ~1200
Diagnostic indicator of lung disease

Pulmonary vs. Alveolar Ventilation

Term Definition How to Influence It

Pulmonary Ventilation Total air movement into/out of lungs per minute Change rate or depth

Alveolar Ventilation Air reaching alveoli for gas exchange Minimize dead space, slow deep breathing

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Mechanics of Breathing

A. Inspiration

↓ Diaphragm contracts

↓ Thoracic volume increases

↓ Intrapulmonary pressure decreases

↓ Air flows into the lungs

B. Expiration

↓ Diaphragm relaxes

↓ Thoracic volume decreases

↓ Intrapulmonary pressure increase

↓ Air flows out of the lungs

Primary Muscles- Diaphragm, external intercostals

Accessory Muscles (during exercise)- Sternocleidomastoid, pectoralis minor, abdominals

Airflow and Resistance

What does airflow depend on?

Pressure difference between the lungs and the atmosphere.

How can resistance change?

By altering airway diameter through bronchodilation or bronchoconstriction.

How can nurses influence airflow?

Administering bronchodilators or positioning patients to promote airflow.

Acid-Base Balance and Breathing

Hyperventilation

Increased CO₂ exhaled
Increase pH (alkalosis)
Encourage slow breathing

Hypoventilation

Increased CO₂ retained
Decrease pH (acidosis)
Stimulate breathing or administer O₂

Buffer System

Bicarbonate Buffer (H₂CO₃/HCO₃⁻)
Maintains pH 7.35–7.45
Monitor ABGs

Bicarbonate Buffer System

CO2 + H2O ⇄ H2CO3⇄ H+ + HCO3- ⇄ H2CO3 ⇄ CO2+ H2O

Respiratory Opposite Metabolic Equal

↓ CO2, ↑pH ↓ CO2, ↑pH ↓ CO2, ↓pH ↑ CO2, ↑pH

↑ CO₂ → ↑ H₂CO₃ → ↑ H⁺ → ↓ pH (acidosis)

↓ CO₂ → ↓ H₂CO₃ → ↓ H⁺ → ↑ pH (alkalosis)

Clinical Questions

Why is understanding respiratory mechanics crucial for patient care (e.g., in ventilator management)?

Helps clinicians monitor disease progression, prevent lung injury and diagnose respiratory problems.

How can nurses use breathing pattern assessment to detect early respiratory distress?

Breathing rate, depth, effort and rhythm are all factors that can allude to any respiratory conditions.

Why is it important to differentiate between hyperventilation and hypoventilation?

These two have different reactions in the body and require different medical treatment. Hypoventilation results in acidosis, and hyperventilation results in alkalosis.