Respiratory Examination – Relevant Anatomy and Physiology

1. Division of Airway:

• Extrathoracic (Upper) airway: Nose to Upper trachea
• Intrathoracic (Lower) airway: Lower trachea to Alveoli and lungs

Note: Vocal fold is also regarded as the demarcating line between upper and lower respiratory tract

2. Angle of Louis: Junction of body of sternum to manubrium (2nd costal cartilage anteriorly and T4/5 posteriorly)

• 2nd rib joins manubrium (Start counting ribs)
• Bifurcation of trachea
• Beginning and end of arch of aorta
• Division of pulmonary trunk
• Division of mediastinum into superior and inferior
• Thoracic duct crosses from left to right

3. Bronchi and bronchioles: About 25 divisions of which last 16 are bronchioles (no cartilage, less goblet cells and less musculature)

4. Lungs and pleura:

a. Base

At Mid-clavicular line (Midpoint between tip of acromion and suprasternal notch)

• Lungs: 6th rib
• Pleura: 8th rib

At Mid-axillary line (Midpoint between anterior and posterior axillary line)

• Lungs: 8th rib
• Pleura: 10th rib

At Vertebral line (Vertical line over spinous process midline)

• Lungs: 10th rib
• Pleura: 12th rib

b. Apex: 1 inch above the clavicle in midclavicular line

c. Medial border: Touches parasternal line at Angle of Louis

• Right lung: Passes vertically downwards to reach base
• Left lung: Follows outer margin of heart to reach base

d. Interlobar fissures:

• Oblique/Major fissure: 6th rib in MCL – 5th rib MAL – medial border of scapula with hyperabducted arm – T2 spine
• Horizontal/Minor fissure (Only on right): Sternum at level of 4th costal cartilage – first line of oblique fissure

Anteriorly: Most upper lobe and whole middle lobe; Posteriorly: Most lower lobe

5. Ribs: 1-7 attach to sternum by cartilage; 8-10 attach to eachother by cartilage; 11-12 floating ribs

6. Topographical division of chest:

a. Anteriorly:

• Supraclavicular region
• Infraclavicular region
• Mammary region: Upper border of 3rd rib to Upper border of 6th rib (sternum to anterior axillary fold)
• Infra-mammary region: Upper margin of 6th rib to lower margin of thorax

b. Laterally: between axillary folds

• Axillary region: Upto upper margin of 6th rib
• Infra-axillary region: Upper margin of 6th rib to lower edge of thorax

c. Posteriorly:

• Suprascapular: Above spine of scapula
• Scapular: Body of scapula below spine
• Infrascapular: Below angle of scapula (7th rib)
• Interscapular: Between posterior edge of scapula

PHYSIOLOGY

a. Inspiration:

• Primary muscle: Diaphragm (Phrenic nerve – C3,4,5), External intercostal
• Accessory muscle: Scalene, Sternocleidomastoid, Alae nasi, Serratus anterior, Others
  • Lift and expand chest wall up creating more negative intrathoracic pressure and thus more air enters lung

b. Expiration:

• Primarily: Elastic recoil
• Secondarily: Internal intercostal, Anterior abdominal wall muscles