6. Mechanics of Breathing Flashcards
What is the goal of breathing?
Movement of O2 into body and elim. of CO2 waste out of body
How does thoracic cage when coupled overlying muscles play into mechanics of breathing?
Contraction of accessory muscles gen. F + causes change in size of thoracic cage –> vacuum in pleural space comm. this F to lungs –> lung expansion
When are accessory muscles recruited for breathing?
When require more ventilation/gas exchange in lungs. In pt w disease or increased O2 requirements, muscles may get overtaxed –> resp. failure
What are the major muscle(s) of the thoracic cage?
Diaphragm + external intercostal muscles
What are the accessory muscles of inspiration?
Sternocleidomastoid + scalene muscles (pull ribs upwards –> increase A-P girth of chest)
What are the accessory muscles of expiration?
Abd. muscles + internal intercostal muscles (pull ribs downwards –> decrease A-P girth of chest)
What links the chest wall + lungs?
Pleural space
At rest, is there a P gradient b/w atm + thoracic space?
No
When chest cavity expands, is there a P gradient?
Yes, decrease in P w/in thoracic space causes air to flow in thru airway from atm
What two pleurae make up the pleural space?
Parietal (chest wall) + visceral (lungs) pleurae
What does pleural space allow transmittance of?
Negative P gen. by expansion of chest wall
Describe the mechanism of action of pleural space and how it contributes to breathing.
Expansion of chest pulls on parietal pleura, which gen. negative P within pleural space. This vacuum force pulls on visceral pleura, causing lung expansion + decrease in P within lungs –> airflow in.
What happens during violation of pleura?
Loss of negative space + collapse of lung! Pneumothorax!
What are the three types of pneumothoraces?
- Closed/tension
- Open/”sucking” chest wound
- Spontaneous
What is a closed/tension pneumothorax?
Violation in pleural space but chest wall intact –> not in direct contact w atm; air can leak into pleural space + increase P w/in chest (tension pneumo)
Every time pt breaths, pneumo worsens + P increases –> requires chest tube to relieve P
What is an open pneumothorax?
Opening in chest wall + potentially in lung as well –> allows air to move from atm into pleural space –> collapsed lung; sucking chest wound occurs when hole cont. from chest wall + thru lungs (air comes in through chest wall + out through airway)
What is a spontaneous pneumothorax?
Resulting from rupture of lung due to pulmonary blebs or weaknesses in lung
What is the result of a collapsed lung?
Impaired gas exchange
What is more severe: tension or open pneumothorax?
Tension
What is a common treatment for bilateral open pneumothorax?
Placing chest tube into pleural space to suck out air until wound heals + lungs can fully expand
How does the increased P in tension pneumothorax affect physiology?
Increased P in pleural space if great enough can push against other side of chest (mediastinal shift) –> P against heart + great vessels –> impairs fxn of heart, arterial blood out of heart, + venous drainage of heart –> –> cardiac arrest!
