Tuesday, January 15, 2013

no more flat tires

One weekend when I was sixteen, my family was loading up the car to go visit my grandparents. As I climbed into the backseat, a stabbing pain in my chest hit me. My left shoulder cramped and my left arm was painful to move.  I told my dad about what I was feeling, and we both dismissed it as a random cramp. Five minutes later, the pain was worsening and I wondered if I was having a heart attack at only sixteen years old. We decided to swing by the emergency room just to be sure.

Come to find out, my left lung had spontaneously collapsed. As doctors with x-ray machines and pokey things began to swarm around, I looked at my unshakeable father standing in the corner of the room. He was looking at me and shifting his weight from side to side, with a furrowed brow and crossed arms. This meant he was confused.

It just so happened that my best friend’s father is a pulmonary specialist. As the drugs began to cloud my head, I watched Dad pacing outside of the room with a cell phone to his ear, talking to my friend’s dad, Dr. Liendo. A man with a well-placed sense of humor, he told my dad that I was experiencing a “flat tire,” and after several minutes of conversation, my dad was clear on what was happening.

One of the most misleading physiological comparisons is that of a lung to a balloon. (If I could legally encourage you to deface every balloon/lung demonstration you see at science education centers, I would). A balloon inflates by air being forcefully pushed into the vacant space inside. This is a positive pressure system, since the balloon inflates by air being pushed into it. But lungs do not work like this. They work on a negative pressure system, meaning that air is pulled into the spongy tissue that is the lungs- not an empty cavity like a balloon. What does the pulling, then? Lungs are not muscularized- but your chest cavity is.

Your diaphragm is the muscular floor of your chest cavity. When it is relaxed, it bows upwards. When it contracts, it straightens out and lowers down- making your chest cavity bigger and therefore expanding the lungs, pulling air in. Ahhh, yes. Your lungs are attached to the walls of your chest cavity. At least they’re supposed to be.

They are attached by a thin layer of moisture called the pleura (imagine two sheets of plastic being stuck together when they get wet). Should this adhesive moisture break contact with the lung surface and the chest wall, air will leak from the lung into this pocket, forming what’s called a “bleb” between the lung and chest wall.  Sometimes, the bleb heals and the pleura reseals itself. No harm no foul.

Left: A tiny bleb at the top of the lung
Right: The lung continues to collapse
Other times, the pleural break is large enough that the lung continues to pull away from the chest wall and collapses. Your diaphragm continues to expand the chest cavity, but the lung is a pathetic, shriveled, useless raisin. (This hurts a lot). This can be fixed by inserting a chest tube so that it rests in the chest cavity, allowing the air pocket to escape and the pleura to reseal. If it’s a stubborn one, they might even hook it up to a vacuum and suck it out.

Dr. Liendo likened this system to a tire (the chest cavity) and the innertube within (the lung). To this day, Dr. Liendo tells me that I am allowed “no more flat tires.” I will always be grateful to him for unfurrowing my dad’s brow that day.

And if a rash of vandalism against balloons being used as demonstration lungs breaks out after this, I will not be upset.