How Do We Breathe? | Understanding Human Breathing

[FeynmanMH42]

I always thought breathing was caused by the diagphragm and intercostal (rib) muscles causing the lungs and chest cavity to expand, thus decreasing the pressure (Boyle's law) to below atmospheric pressure and causing air to rush into achieve equal pressure inside and outside the lungs.
But I have just seen a film of open heart surgery where much of the ribcage was removed and the lungs still moved up and down at about the same rate as normal breathing.
Clearly some mechanism of breathing was going on without rib muscles; is my knowledge of the human breathing mechanism wrong or do they use some kind of artificial means of ventilation?
If the second option is correct then how does this artificial mechanism work?
And if the first option is correct then how do we breathe?

 

[Moonbear]

During open heart surgery, the patient would be on a ventillator for respiratory support. The ventillator works on positive pressure, forcing air into the lungs. Once the air is in the lungs, gas exchange occurs the same way as when we normally breathe by a negative pressure mechanism.

 

[ravenprp]

Your understanding of the human breathing mechanism is partially correct. The diaphragm and intercostal muscles do play a crucial role in expanding the lungs and creating a pressure difference that allows air to flow in. However, there are other muscles and structures involved in the process of breathing as well.

During normal breathing, the diaphragm contracts and moves downward, which increases the volume of the chest cavity and decreases the pressure inside the lungs. At the same time, the intercostal muscles between the ribs also contract, causing the rib cage to expand and creating more space for the lungs to expand. This coordinated effort of the diaphragm and intercostal muscles is what allows us to breathe in and out.

However, in situations like open heart surgery where the rib cage needs to be removed, the diaphragm and intercostal muscles may not be able to function properly. In such cases, doctors may use mechanical ventilation to assist with breathing. This involves using a machine called a ventilator to deliver oxygen to the lungs and remove carbon dioxide from the body. The ventilator works by creating pressure differences in the lungs, similar to how the diaphragm and intercostal muscles do, to facilitate the movement of air in and out of the lungs.

So, in short, the human breathing mechanism involves the diaphragm and intercostal muscles working together, but in certain situations, artificial means of ventilation may be used to assist with breathing. It is important to note that mechanical ventilation is typically only used in medical settings and is not a part of our normal, everyday breathing process.