Respiratory Pressures

MUSCLES OF RESPIRATION

Primary Muscles

• Responsible for changing the thoracic cage during normal or quiet breathing.

Accessory Muscles

• They are to help the primary muscle during forceful breathing.

1. Inspiratory Muscles
1. Primary muscle:  
1. Diaphragm muscle
2. External Intercostal muscle
2. Accessory muscle:
1. Sternocleidomastoid muscle
2. Scalene
3. Pectorals
4. Anterior serratus
5. Elevators of scapula
2. Expiratory muscles
1. Primary muscle:
1. Internal intercostal muscle
2. Accessory muscle:
1. Abdominal muscle

RESPIRATORY PRESSURES

1. Intra-alveolar pressure or Intra-pulmonary pressures: are the pressure existing in the alveoli of the lungs

2. Intrapleural pressure or Intrathoracic pressures:  are the pressure present in the pleural cavity i.e. between the visceral and parietal layer of the pleura. these pressure are negative

3. Atmospheric pressure:  pressure on the surface of the chest. It is considered as zero

4. Transmural pressure:  are pressure across the wall of the structure

TRANSMURAL PRESSURE = (Pressures inside the wall) - (Pressure outside the wall)

Fig.1: Respiratory pressures

Transmural pressure can be;

• Positive----- pressure responsible for inflating the lung
• Negative-----responsible for deflating the lung
• Zero-----no net inflating or deflating pressure

TYPES OF TRANSMURAL PRESSURE:

1. Transpulmonary pressure:
1. is the pressure across the alveoli
2.  = (intra-alveolar pressure) - (intrapleural pressure)
3. Transpulmonary pressure determine How much inflating or deflating pressure on the lung
2. Transthoracic pressure: 
1. is the pressure across the chest wall
2. = (Pleural pressure) - (Atmospheric pressure)
3. Trans respiratory pressure:
1. = (Alveolar pressure) - (Atmospheric pressure)