Smoking and Carbon Monoxide:
Hemoglobin in red blood cells transports oxygen to body tissue. Anything that adheres to hemoglobin takes up space on the cell and limits the amount of oxygen that gets to body tissue. Smoking deposits carbon monoxide on the hemoglobin and literally takes up space that should be carrying oxygen. If you smoke, realize your susceptibility to Hypoxia is heightened. A leaky exhaust system can certainly raise carbon monoxide levels in the cockpit to dangerous levels.
As the glider cockpit pressure decreases during ascent, the expanding air in the middle ear pushes the Eustachian tube open, allowing the air to escape down the nasal passages, equalizing the middle ear chamber pressure with the outside pressure. However, on descent the pilot must periodically open the Eustachian tube to equalize pressure. This can be done by swallowing, yawning, tensing muscles in the throat or by doing the Valsalva Maneuver. The Valsalva Maneuver is done by closing your month, pinching your nose shut and attempting to blow through your nostrils. An ear block can produce severe pain and loss of hearing that can last for several hours. If an ear block does not clear shortly after landing, a physician should be consulted.
A sinus block can produce the same excruciating pain as an ear block. Again, don't fly with a cold, sinusitis, or a nasal allergic condition.
Decompression Sickness After Scuba Diving:
Pilots should allow their body to rid itself of excess nitrogen absorbed during diving. The recommended waiting time before going to flight altitudes of up to 8,000 feet is at least 12 hours after diving which has not required controlled ascent, and at least 24 hours after diving which has required controlled ascent. The waiting time for flights above 8,000 feet is 24 hours. Flying too soon after scuba diving could allow nitrogen gas bubbles to form around joints and muscles causing severe pain.
Hyperventilation in Flight:
It is an abnormal increase in the volume of air breathed in and out of the lungs. This can occur during a stressful situation. During hyperventilation, the pilot blows off excessive carbon dioxide from his body. This can cause lightheadedness, suffocation, drowsiness, and tingling in the extremities. Incapacitation can result from disorientation and painful muscle spasms. A pilot can stop hyperventilation by breathing into a paper bag or simply recognizing the symptoms and making a conscious effort to slow down his/her breathing. Do you carry a paper bag, I don't. But singing works well also. Singing forces you to breath normally. It might not be audibly pleasant for your passengers, but you passing out might make them a little more uncomfortable.