Managing Shortness of Breath. Self Learn series 15

How to manage shortness of breath at home.

Shortness of breath is defined as labored or difficult breathing associated with a variety of disorders, indicating inadequate ventilation or low blood oxygen. Before we proceed to learn how to manage this stressful situation we will review how the normal healthy respiratory system works.

Illustration 1. Positioning of head and neck to maintain a clear airway.

Shortness of breath is also called “Dyspnoea” in medical / nursing terminology. (Latin dyspnoea, Greek dyspnoia from dyspnoos - short of breath) or shortness of breath (SOB) is perceived and/or real difficulty during breathing. This includes the presence of pain on breathing, for example when a patient has pleuresy. It is an extremely common symptom of many disorders, including emphysema, COPD, broken ribs, lung cancer, malignant hypertension, and so forth.

This article is written for ordinary people, without a medical background and includes suggestions on how to cope with shortness of breath. Many of the home interventions, like positioning the patient right do not require a prescription but medications like diuretics and broncho dilators require a prescription from a medical prectitioner in most countries.

Picture 1. Cross-section of the Brain showing the location of the breathing centre in the medulla oblongata of the hind brain.

The desire to breathe, in most of us comes from the Respiratory Centre located in the brain. The process is unconscious and is affected by drugs, eg anaesthesia, exercise, shifts of body fluids and shifts in the levels of carbon dioxide. There are three main components which control respiration. These are: a. The Respiratory centre or controlling area in the brain, b. an afferent pathway and c. an efferent pathway.

The neurones (nerve cells) of the controlling area integrate the information from other parts of the body and produce a coordinated response. This response from the central controlling area is carried to the various organs and muscles along efferent pathways. The input to the central controlling area is from the various sensors via the afferent pathways.

The central controlling area for breathing, called the respiratory centre, is in the lower part of the brain stem, in the medulla oblongata. There are "inspiratory neurones" which are active during inspiration and inactive during expiration. Other neurones are active during expiration but not inspiration-the "expiratory neurones". These two groups of neurones automatically maintain a rhythmic cycling pattern of inspiration and expiration. This automatic rhythm can be modified by the afferent information eg exercise and certain chemicals in the brain.

1. Afferent Nerve Supply: Central Chemorreceptors. Please see picture 2 Chemoreceptors are cell which are sensitive to chemical stimuli. Thes are located on the floor of the fourth ventricle (part of the brain stem) that respond to the acidity of the cerebrospinal fluid (CSF) and the output from these cells influences breathing. An acidic CSF causes hyperventilation this is the reason for dyspnoea with conditions such as diabetic ketoacidosis. An alkaline CSF inhibits the respiratory centre. Carbon dioxide in the blood can rapidly diffuse across into the CSF, and there is a balance between the level of carbon dioxide, hydrogen ion and bicarbonate ion in the CSF. If the carbon dioxide in the blood increases (eg following exercise), then the carbon dioxide, hydrogen ion and bicarbonate ion concentrations increase correspondingly in the CSF. This increase in CSF acidity causes hyperventilation which lowers the carbon dioxide concentration in the blood. A low blood carbon dioxide level (hypocarbia) has the opposite effect and may occur, for example, following controlled ventilation during anaesthesia. This may delay the return of spontaneous breathing at the end of surgery.
2. Afferent Nerve Supply: Peripheral chemoreceptors. These are located in the carotid and aortic bodies. They are small pieces of tissue that contain chemoreceptors which respond to the oxygen and carbon dioxide concentrations in arterial blood. The carotid body is the more important of the two and is situated at the division of the common carotid artery into the external and internal carotid arteries in the neck. The aortic body is found on the aortic arch. The information from the carotid body is carried along the glossopharyngeal nerve (the ninth cranial nerve) and the information from the aortic body is along the vagus nerve (the tenth cranial nerve), to the respiratory centre. The output from the carotid body is thought to provide information to allow immediate regulation of breathing, breath by breath, by the respiratory centre. In normal people, if the arterial blood reaching the carotid body has a partial pressure of oxygen of 10kPa (80mmHg) or a carbon dioxide partial pressure of more than approximately 5kPa, (40mmHg), then there is an immediate and marked increase in breathing. These limits can be modified by disease or age; for example, people with chronic bronchitis may tolerate an increased concentration of carbon dioxide or a decreased concentration of oxygen in the blood or both.
3. Afferent Nerve Supply: Brain. Breathing can be influenced by other parts of the brain. We can all consciously breathe deeply and more rapidly (called hyperventilation), and this can happen, for example, before starting strenuous exercise. Intensely emotional situations, for example, distressing sights, will also cause hyperventilation. Hyperventilation is also part of the response to massive blood loss. This response is co-ordinated by the autonomic system in the hypothalamus and the vasomotor centre in the brain stem.


Picture 2. Cross section of the brain showing the Afferent nerve (pathway to the brain).

4. Afferent Nerve Supply: Lung. There are various receptors in the lung which modulate the patient’s breathing. Receptors in the wall of the bronchi respond to irritant substances and cause coughing, breath holding and sneezing. In the elastic tissues of the lung and the chest wall are receptors that respond to stretch. There are stretch responses that occur when the lung and chest wall are distended and inhibit further inspiration. This is an obvious safety mechanism to avoid overdistension. Conversely, when the lung volume is low, then there are opposite reflexes. A small increase in lung size may stimulate stretch receptors to cause further inspiration. This can sometimes be seen in anaesthetised patients who have been given an opioid; spontaneous breathing may be absent or very slow, but if the patient is given a small positive pressure breath by the anaesthetist, then inspiration is stimulated and the patient takes a deep breath. This reflex may also have some function in newborn babies just after delivery, when small breaths may stimulate further inspiration. There are also stretch receptors in the blood vessels in the lung. If these are stretched, as in heart failure, the response is to hyperventilate. The information from these receptors in the lung is carried to the respiratory centre along the vagus nerve.