Conditions affecting the functioning of the respiratory system
Asthma is an inflammatory condition that leads to tightening of the muscles around the bronchioles, causing these finest airways to become even more narrow and
reducing the flow of air in and out of the lungs.
It can be treated using inhalers or atomiser masks, typically providing:
- corticosteroids - used regularly as preventive medications to treat the inflammation within the airways
- salbutamol (ventolin) - to provide quick relief by relaxing the muscles and opening the airways
Of course the intake of these drugs can be problematic if the airways have already started to become constricted.
An asthma attack is a sudden worsening of asthma symptoms caused by the tightening of muscles around the bronchioles (bronchospasm). During the asthma attack, the lining of the airways also becomes swollen or inflamed and thicker mucus - more than normal - is produced.
Asthmatics are encouraged to monitor their condition by measuring their peak flow
by blowing into a simple device.
Typical values for a healthy male aged 40 are 600 L/min or above, falling to 500 at age 65. For women values are generally lower.
Pulmonary fibrosis scars and thickens the tissue on the outside and between the alveoli and it reduces the volume of the lungs, without affecting the airways.
This results in shortness of breath, dry cough and general fatigue.
In clinics, spirometer machines can be used to record the flow of air breathed out over a short period of time, giving a trace like the ones below.
The average volume of air breathed out by three groups of people
On this graphic, group A had healthy lungs.
Groups B and C had different lung conditions that affect breathing, mentioned above.
Use the shape of these traces to answer the questions below.
You should be able to comment using these values:
1 Forced expiratory volume (FEV)
: the greatest volume of air a person can breathe out in 1 second.
2 Forced vital capacity (FVC): the greatest volume of air a person can breathe out in a single breath.
3 Together with the probable effect caused by the airways
Click here for the equivalent questions (below) about asthma
Which group, B or C, had fibrosis of their lungs?
Group > B
1> They breathe out nearly as quickly as the healthy at the start [similar FEV to group A - 67%]
2> The total volume breathed out [FVC] is reduced below normal because deflation of lungs stops at a lower value [62% of A]
3> So bronchioles are not affected as they do not provide much resistance to flow
Chronic obstructive pulmonary disease (COPD)
This term covers a group of lung conditions that cause breathing difficulties.
The following symptoms are common:
increasing breathlessness, particularly after activity
a persistent chesty cough with phlegm (thick mucus) - often described as a "smoker's cough"
frequent chest infections
The main causes are long-term exposure to airborne irritants, including tobacco smoke, marijuana smoke, air pollution, and chemical fumes and dust.
is a condition in which the walls between the alveoli break down and
enlarge the air spaces. This reduces the area for gas exchange and so an affected person experiences breathing difficulties after exercise.
The lung tissue has less elasticity, possibly caused by reduction in the amount of elastin in the connective tissue surrounding the alveoli.
This is long-term inflammation of the main airways: trachea and bronchi. Smoke causes cilia to stop beating, and more mucus is produced, reducing movement of air into the lungs.
is an infection in one or both lungs, possibly caused by bacteria, viruses, or fungi. This causes inflammation of the alveoli, and they fill with fluid, reducing access of oxygen to the alveolar epithelium and making it difficult to breathe.
Coronavirus (Covid 19)
This virus infects the respiratory system, and may cause symptoms of variable seriousness:
a high body temperature
a new, continuous cough
Infected persons may get better after 7 days' isolation, or if symptoms worsen then hospitalisation may be necessary.
Here, oxygen is often supplied via a simple face mask or nasal tube because ordinary air does not provide enough oxygen when alveolar surfaces are covered with fluid and breathing is laboured.
Further deterioration may be treated using different levels of technology, in an intensive care unit:
Continuous Positive Airway Pressure (CPAP)
is a form of non-invasive ventilation
(using a firmly attached mask but not 'intubation') that often works best with Covid-19 patients.
This technique was developed to treat sleep apnoea at home.
It may use resources that are in short supply.
Some CPAP machines use 50 litres of oxygen per minute for a single patient.
is a more serious process, taking over the breathing process using a pump and electronic control system, together with a humidifier.
The oxygen is sent into the body via a tube inserted through the mouth and into the airway, and gases leaving the lungs are continuously analysed, especially for CO2
Mechanical ventilator for positive pressure ventilation
Picture credit: Peter lamb
This generally requires sedation (induced muscle paralysis, possibly using the 'poison arrow' compound curare which is an inhibitor of acetylcholine esterase) to prevent the body's natural breathing movements, and requires supervision by highly trained staff.
Unfortunately these procedures may be accompanied by other health problems:
Ventilator-induced lung injury (VILI) and ventilator-associated lung injury (VALI).
Barotrauma is a form of VILI that is associated with alveolar rupture due to the associated pressure;
comes in many forms.
Squamous cell carcinoma
begins in the tissues that line the larger bronchi, but it can spread to other parts of the body.
It is especially linked to exposure to cigarette smoke, but it has also been found that the second most significant risk factor is the radioactive gas radon which is naturally released from rocks like granite in some parts of the country. It is thought that improvements in building construction including double glazing have caused less draughty houses in which the gas can accumulate.
is a form of cancer that mainly affects the lining of the lungs (pleura), altough it can affect other parts of the body.
It is caused by long-term exposure to irritant substances such as asbestos fibres from roofing and walling products (asbestosis), or stone dust (silicosis). Presumably they are breathed in and pass through the walls of the alveoli and into the pleura on the outside of the lung.