Now for the really bad news.
"Colds" can be from a number of causes and can affect a number of systems apart from just your ears.
Most cold's, 'flu' sniffles, call them what you like - are caused by viruses and there are literally dozens which as part of their spectrum produce nasal congestion (which gives the blocked up ears mentioned. )
Trouble is they also commonly affect other systems. Most significantly the balance mechanisms of the middle ear, the lining of the heart, the heart muscle itself the lungs, the joints and the liver. Specific Viruses tend to have a defined spectrum of systems that they affect while other viruses may affect different systems.
Unless you have tests done ie : blood tests (which unfortunately will take longer to give a result than the illness is likely to last) you aren't going to know if you are infected with a virus which causes these extras or not.
As a somewhat simplistic comment:
If your ears are blocked:
You are at risk of rupturing an ear drum either on ascent or descent. This causes pain, sometimes sudden deafness or loud ringing in the ears enough to make you functionally deaf.
Sudden changes of pressure due to rupturing of the drum can induce sudden vertigo +/- severe unstoppable vomiting.
Some viruses attack the middle ear independantly of the nose blocking stuff. Produces the same vertigo affect but doesn't need the preceeding blocked nose or ruturing of the ear drum. (proper name Acute Viral Labyrinthitis)
A number of cold viruses produce an inflammation of the heart lining (Acute Viral Pericarditis) or an inflammation of the muscle fibres of the heart (Viral Myocarditis) either of which can lead on to poor pump function or abnormal rhytms which can cause cardiac arrest.
As a completely unproven rule of thumb it has been said that if you have a cold/"flu" etc with muscle aches then you are at higher risk of the heart damage varient and should avoid excercise and stressing your heart till it all settles down.
If you have congestion on the chest you are at risk of phlegm blocking some smaller airways and causing decreases in your blood oxygen capacity - enough to make you hypoxic at helicopter altitudes.
If you have ever had a collapsed lung and have a tall and thin body shape then going up to high altitudes rapidly with congested chest you are at risk of another collapsed lung. (or perhaps your first collapsed lung)
Most people with colds obviously don't get these extra problems. Trouble with helicopter flying is it that it does put a big increased load on the respiratory, nervous and cardiac systems. (A number of studies have looked at heart rates, blood pressures etc in pilots and shown helicopter pilots operate at levels similar to moderate to severe excercise for the whole flight and like extreme excercise for approaches.)
Does any of this crap really ever affect pilots I hear the non-believers ask?
The SeaWorld crash from the gold coast in Oz ?maybe 15 years ago. Pilot plus 4 pax. All died. Diagnosis - Pilot was getting over a cold/viral illness with myocarditis (heart muscle damage). The extra cardiac workload thought to have triggered an abnormal heart rhythm. Post mortem showed definite myocarditis.
Here endth the lesson!
