Respiratory system: anatomy, gas transport, assessments, disorders (pneumothorax, pleural effusion, respiratory failure, ARDS, asthma) — review and clinical correlates

Ventilation

The mechanical movement of air into and out of the alveoli, requiring diaphragm and chest wall movement.

Perfusion

The blood flow through pulmonary capillaries to transport gases to and from the alveoli.

Pneumothorax

Collapsed lung due to air in the pleural space, disrupting negative pleural pressure.

Tension pneumothorax

A severe pneumothorax with progressive accumulation of air causing mediastinal shift and hemodynamic compromise.

Pleural effusion

Accumulation of fluid (serous fluid, blood, pus) in the pleural space.

ABG (arterial blood gas)

An arterial blood sample that measures PaO2, PaCO2, pH, HCO3-, and more.

Hypoxemia

Low arterial oxygen, defined as PaO2 < 80 mmHg.

Hypercapnia

Elevated carbon dioxide in the blood, defined as PaCO2 > 45 mmHg.

Oxygen-hemoglobin dissociation curve

Graph showing the relationship between PaO2 (x-axis) and SaO2 (y-axis).

V/Q mismatch

Imbalance between ventilation (V) and perfusion (Q); normal V ~ 4 L/min, Q ~ 5 L/min.

SaO2

Arterial oxygen saturation, representing the percentage of hemoglobin bound with oxygen.

FiO2

Fraction of inspired oxygen; the percentage of oxygen in inhaled air.

ARDS (acute respiratory distress syndrome)

Acute inflammatory lung injury causing diffuse alveolar damage and widespread hypoxemia.

Thoracentesis

Procedure to remove pleural fluid via needle, usually with the patient seated and leaning forward.

BPG / DPG (2,3-bisphosphoglycerate)

An intracellular compound that affects hemoglobin's affinity for oxygen.

Respiratory failure

Inadequate ventilation or perfusion causing hypoxemia and/or hypercapnia.