Sex and drugs and rock and roll (part 2)

Yesterday it was Ian Dury and polio. Today it is Ian Dury and the iron lung.

Beyond doubt the late great Ian Dury had polio. He may have been in an iron lung for the acute phase of his illness. Interviews about this week’s cinema release of the biopic ‘Sex and drugs and rock and roll’ with his son Baxter certainly suggest he was.
Being ‘in an iron lung’ is a strangely persistent medical cliché. It is a while since they were in routine use, as the technology has been largely superseded, but they are not out of use completely. The Lane Fox Unit, a national referral centre for chronic respiratory failure at Guys and St. Thomas' Hospital in London reports it still supports two or three people who are long term users of iron lungs as a result of polio.
Before tackling breathing with the unfamiliar iron lung we’ll have a look at breathing in familiar dramas. Think back to the last Holby City or Casualty calamity heart attack you saw. Someone in a bad way needs help with their breathing. Amongst some irrelevant distracting drama and faffing medical cliché the doctor pops a tube down the patient’s throat. He or she uses a translucent semi-rigid balloon, shaped like a rugby ball, to inflate their lungs via the tube. That’s the ambu bag. Puff puff puff. The bag will shortly be swapped for full on ‘life support’ with bespoke respiratory settings, an ITU bed, a designated nurse and a swivel eyed mistress tampering with a syringe and the ward sister's Ferrero Rocher.
The doctor is using an invasive method (tube in throat) and positive pressure (doctor puffs oxygen into the patient’s lungs) to keep the patient alive.
So we have one imaginary unfortunate unconscious with a tube in his mouth in an A and E department. Time to start imagining someone else, in an iron lung.
Basically, this person is entirely encased in a metal box which looks and sounds like this (thank you Science Museum) with their head poking out of an air tight seal. The air in the box is sucked out for each breath, forcing the person’s chest to expand, sucking air in through the patient’s nose or mouth as that’s the only place it can possibly come from.
He’s not encumbered with tubes or sedation after the initial acute respiratory problem which necessitated the iron lung in the first place. He can talk and eat, though his breathing is not under his own control. Polio in the 1940s and 50s has meant that a few patients have survived for literally decades dependent on their iron lung. Most will have spent significant periods of time at home, albeit in the iron lung, as the absence of a tube and full consciousness is a much more stable and safe proposition than faces our other imaginary ill person with his new tube going from A and E to ITU.
Iron lungs are a non invasive (no tube) negative pressure form of ventilation.
In normal breathing we create negative pressure by moving our ribs up and out and our diaphragm down, drawing air into our lungs. We are not passively waiting for the air to rush into our nose and mouth to inflate our lungs from the outside. That would be alarming and incompatible with life, as breathing out would be impossible.
Nowadays, doctors would go for a cuirass system of some kind or a positive pressure face or nose mask instead, where long term use of a breathing tube would be risky or impossible. 
Jousters or battle re-enactors looking for the latest in armour might recognise the word ‘cuirass’. To them it means a piece of armour for protecting the breast and back. In the context of medicine and breathing it refers to a device for ventilation where the patient wears an upper body shell - the cuirass - which compresses and relaxes, sucking air into and forcing air out of their lungs in as good an approximation of normal breathing as can be externally applied.