Breath-hold Diving – Effect of Barometric Pressure on the Pulmonary System

00:02 In this lecture, we’re going to talk about barometric pressure and how it affects the pulmonary system.

00:07 We have a number of important learning goals to go through.

00:10 After this lecture, you will be able to identify the major physiological responses to both acute and chronic increases in barometric pressure as well as specific aspects of breath hold-diving.

00:24 In this lecture, we will also be able to identify the major physiological responses to decreases in barometric pressure both in acute and chronic conditions.

00:34 Finally, we’ll go through the important and very interesting process of understanding the pathophysiology of altitude illnesses including acute mountain sickness, high altitude cerebral edema and high altitude pulmonary edema.

00:49 Okay, let’s talk about high barometric pressures first.

00:54 To do that, what we’re going to do is talk about increases in barometric pressure.

01:00 Barometric pressure increases as you go beneath the level of the water.

01:05 So at sea level, you may have a barometric pressure of around 760 millimeters of mercury.

01:11 As you go only 30 meters underneath the water, you will double the barometric pressure.

01:18 What kind of changes happen when you do breath hold-diving? There’s both an increase in the amount of barometric pressure, but what that also does is changes the volume with in the lungs.

01:30 So if you started out with a volume of let’s say 6 liters.

01:34 If you go 30 meters underneath the water, you will decrease that in half to only 3 liters.

01:40 During the ascent or the process of you going back to the surface of the water, pressure will start to decrease and lung volume will increase and this just is a process of the physics involved with high barometric pressures.

01:56 I have a good example for you that hopefully will emphasize the importance of understanding how barometric pressure affects the ability to do your breath hold-diving and one very important clinical aspect.