40 to 60 feet is deep, but possibly not significant enough to cause lung squeeze. I'm not a doctor, but I could see that happening if he was not used to going that deep or if hewas recovering from a cold or if his lungs had been already sensitive from any kind of prior lung trauma.
Some more info from around the web:
My experience with avoiding squeeze has led me to a few conclusions:
1.Packing is an advanced technique that may not be safe for everyone and requiring careful control so as not to injure lung tissue.
2.Packing for dive can lead to squeeze for a variety of reasons, even in shallow depths
3.Fast descents can increase severity and likelihood of lung injury
4.Vaslava equalizing, contractions, or tension in the diaphragm (common among beginners and intermediate freedivers) can lead to squeeze
5.Rapid depth progressions or big jumps in depth most often result in lung squeeze
6.Those most at risk are usually intermediate freedivers who are confident that they can hold their breath long enough to go deeper than 35m.
In my own diving, I follow these rules:
1.Never use lung packing while freediving (I have had to improve my equalizing techniques) and avoid excessive packing during static and dynamic
2.Go down slowly at less than 0.8 m/s or even slower in the first 30m of each dive (for gradual acclimatization )
3.Always allow enough time to achieve a certain depth goal (this is why I decided not to compete, because I had not done any dives over 40m since last summer and a few weeks was not enough to reach my goal)
source:
ImpulseAdventure's Peter Scott
Your lungs are designed to go from one size to another as you breathe in and out. The lungs never completely empty. In fact, if they did totally deflate they might not be able to reinflate because the small surfaces might stick together. That is a collapsed lung. The minimum size the lungs become when one fully exhales is known as the residual volume. If you compressed the chest and forced air to leave the lungs until they were smaller than the residual volume it could cause serious barotrauma. There could be lung rupture due to rib penetration. There might be a fluid build-up in the lungs leading to pneumonia. There could be a total lung collapse possibly resulting in death.
Taking a full breath and skin diving to 33' would cause the lungs to be 1/2 of their original size. At 66' they would be 1/3, and at 99' they would be 1/4. If your lungs' residual volume was between 1/3 and 1/4 serious damage might result from this breath-hold dive to 99'. Most people do not hold their breath and dive that deep so this is not usually considered a serious problem. The few divers that do dive that deep holding their breath have trained for years to do it, have a changed lung capacity, and probably have their lungs fill with fluid when they are at depth. The fluid prevents further compression. When they ascend and the lungs grow larger the fluid occupies only a small portion of the lungs preventing drowning. Incidentally, the free-diving record, held by a woman on 4/29/07, is 289'. On 4-11-08 Leo Muaoka did a free-dive to 249' in the Bahamas.
DeepSix.com
