My princess started to develop a nocturnal cough in the last few days. Not a "little 11 year old girl" cough, but a deep "chesty old man with bronchitis" cough.
The change of the season tends to bring on a bit of bronchial hypersesponsiveness, that is characteristic of, and has essentially the same pathophysiology of, Asthma.
She (we) have always responded to SABAs and so I thought I would look at the common metered inhaler SABA.
SABAs are short acting beta-agonists. The most common in use (and over the counter in Australia) is Salbutamol marketed under the trade names of Asmol, or Ventolin. Many paramedics and nurses are familiar with the dosage forms of metered Aerosol (MA), nebulised and IV. This post looks at the MA variety that any "Joe Lunchbox " can buy from their chemist (drug store), with no prescription.
First let's look at the action. In bronchial - hypersesponsiveness and asthma, one principle pathophysiological principle is that of bronchospasm.
Smooth muscles that surround the bronchioles constrict like snakes squeezing their prey. This restricts the air flow and stimulates over secretion of the mucous secreting cells that line the respiratory tract. The symptoms are cough (cream sputum), and shortness of breath often with an audible wheeze as air squeezing through wet narrow tubes becomes turbulent.
Specialised adrenaline sensitive receptors in these smooth muscles, called Beta-receptors are stimulated by adrenaline (epinephrine) and instruct the muscles to relax. Thereby preventing the bronchial spasm of the muscle. Other chemicals and drugs work on these same Beta receptors, and have this same effect. Salbutamol is one such drug.
The beta receptor or more correctly "beta Adrenergic receptors" because of their stimulation by adrenaline, are activated as part of the Sympathetic nervous system (SNS) response to stress and shock or threat (fight or flight response). If you were being chased by a deadly drop bear, your SNS would release Adrenaline to increase heart rate, contractility, stimulate glucose release into blood, open your pupils to
Let more light in, constricts blood vessels in your skin and gut to allow more blood to flow to muscles and vital organs, AND... Relaxes smooth muscle in your lungs to allow you to ventilate easier.
Parts of this sympathetic response can be mimicked by drugs that are called Sympathomimetics. One such family of Sympsthomimetic is the Short (and long) Acting Beta Agonists (SABAs and LABAs).
Salbutamol -aka Albuterol in the USA (Ventolin) is a SABA that allows for constricted smooth bronchial muscle to relax, improving flow of air.
When buying Amy's Ventolin metered inhaler (puffer) yesterday I was very very surprised and disappointed to see the "how to use" leaflet showed images of the puffer being placed into the mouth of the model. No mention of a spacer device.
When these MA medications are used, the atomised gas is propelled at hundreds of MPH to the back of the throat or roof of the mouth where the drug is swallowed. It is not absorbed and as little as 0.2% of the dose gets to the lungs where they exert their effects topically.
It is functionally useless to use a MA puffer in your mouth. So I was astounded that the product insert showed this technique.
Used with a volume spacer device, either commercial, or makeshift with a water bottle, soda can or even an empty coffee cup, these puffers are more effective as nebulisers, and safer from an infection control point of view.
One other point. These sprays hold only two hundred (200) doses, yet contain enough compressed gas to continue making the characteristic spray sound for up to 350 squirts. The dangers inherent in this, is that a user could be using their MA with faith that they are getting medication delivered, but only getting the propellant gas.
Never use the patients own MA, always a fresh one when dosing.
In acute asthma attacks, the recommended first aid is a 4.4.4 procedure.
Sit the person up. Administer a dose via a spacer device and ask them to take 4 deep breaths. And repeat for 4 doses.
...
Wait 4 minutes and Repeat.
If no improvement in 10 minutes, or rapid deterioration occurs, they need hospital.
...
Steroids (IV Hydrocortisone, or Prednisone, betamethisone) does nothing for 4-6 hours.
Recap - 4 doses each with 4 breaths. Wait 4 minutes and repeat.
And ALWAYS use a volume spacer to allow the drug to atomise into a gas, before it is inhaled.
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