Philip Woodrow, MA, RGN, DipN, Grad Cert Ed.
Practice Development Nurse, ITU, Kent and Canterbury Hospital NHS Trust
Nurses are often the first members of the health-care team to detect breathing problems in patients, and are often involved in caring for patients receiving respiratory support ranging from oxygen therapy (via a facemask or nasal cannulae) to non-invasive ventilation.
This paper describes the physiology of breathing and respiratory failure and should help nurses to:
- Identify respiratory failure
- Understand the main problems of respiratory failure
- Reflect on, and develop, their practice and development professionally in this area.
Breathing is controlled by the respiratory centres, which are situated with other vital centres in the medulla, part of the brain stem (Guyton and Hall, 2000). The respiratory centres increase both respiratory rate and the size of each breath with one or more of: high carbon dioxide levels; acidosis; low oxygen levels, in the blood. The higher these levels are, the more the respiratory centres are driven; lower equals less drive (Marieb, 2001).
Respiratory function can be measured by taking arterial blood gas samples, to record carbon dioxide and oxygen levels. Once levels are normalised, the rate and depth of breathing will decrease (Marieb, 2001). Low carbon dioxide levels, alkalosis or high oxygen levels may reduce the rate and size of breaths.
In healthy people, respiratory response occurs within three minutes of imbalance (Marieb, 2001), exerting up to double the effect of combined chemical buffers. Alveolar ventilation can increase up to 15 times or decrease to nothing (Marieb, 2001), which in turn can return a life-threatening pH of 7.0-7.2 back to the normal 7.3-7.4 in three to 12 minutes (Guyton and Hall, 2000).
Carbon dioxide normally has the greatest effect on respiratory drive (Marieb, 2001), but with constantly high levels of blood carbon dioxide from chronic obstructive pulmonary disease (sometimes called chronic airflow limitation), chemoreceptors can become desensitised to carbon dioxide, so respond more to oxygen levels (Marieb, 2001).
Giving high concentrations of oxygen to patients with COPD may therefore reduce their respiratory drive and increase rather than resolve their problems. However, Bateman and Leach (1998) suggest that the risk of respiratory depression in people with chronic respiratory diseases is overstated, since only 10-15% of such patients are at risk of bradypnoea if given high oxygen concentrations.
Mosby’s medical dictionary defines respiratory failure as ‘the inability of cardiac and pulmonary systems to maintain an adequate exchange of oxygen and carbon dioxide in the lungs’. This identifies it as failure of the respiratory system to meet both the body’s metabolic demand for oxygen and the clearance of carbon dioxide (metabolic waste).
Many pathologies can cause respiratory failure, but failure is a problem of either oxygenation or ventilation (British Thoracic Society, 2002). Diseases that increase the fluid barrier in alveoli or interstitial tissues (such as pulmonary oedema, emphysema) can cause oxygenation failure. It can also be caused by:
- Severe acute asthma
- Left ventricular failure and other causes of pulmonary oedema
- Pulmonary embolism
- Pneumonia (Crompton et al, 1999).
Carbon dioxide is far more soluble than oxygen, so it can perfuse across such oedematous tissue (Guyton and Hall, 2000). Carbon dioxide levels in blood may therefore remain normal when oxygen exchange is impaired. Oxygenation failure is often called type 1 (Box 1).
Ventilatory failure can be caused by increased airway resistance and reduced lung compliance (such as bronchitis), or any other mechanism resulting in insufficient volumes of gas to ventilate alveoli (Beers and Berkow, 1999). For example, low respiratory rate and/or low tidal volumes often occur during recovery from anaesthesia, or from opiates when oxygen levels are low. But carbon dioxide removal requires active tidal ventilation, so reduced tidal volumes and/or gas trapping prevents adequate carbon dioxide removal. Therefore both oxygen and carbon dioxide blood levels are affected. Therefore, in addition to blood oxygen levels being low (hypoxia), carbon dioxide blood levels are high (hypercapnia).
Respiratory failure can also be caused by a chest infection. Any identified infection is likely to be treated by appropriate antibiotics. If a chest infection is suspected but the organism (and its sensitivity) has not been identified, patients should be prescribed broad-spectrum antibiotics (Crompton et al, 1999).
Identifying respiratory failure
Identifying the type of respiratory failure by arterial blood gas sample is important, as it indicates what respiratory support may be needed. Type 1 respiratory failure may require only supple-mentary oxygen, but type 2 failure may require additional support such as continuous positive airway pressure (CPAP) or biphasic positive airway pressure (BiPAP) to increase exchange of both gases and, where possible, reverse any causes for low tidal volumes or low respiratory rates.
Where patients have actual or potential problems with breathing, observations of respiratory function should include: rate, depth, pattern and breath sounds (Mulligan, 2000).
In health, a normal respiratory rate at rest is 10-14 (Darovic, 1997). As previously stated, the respiratory centres normally respond to either high levels of carbon dioxide or low levels of oxygen. However, responses to increase respiratory rate and depth may be reduced with:
- Cerebral damage or impairment (Lumb, 2000)
- Opiate overdose (from excessive analgesia or some recreational drugs) (McCaffery, 1994).
Patients in pain, especially if this is increased by breathing deeply (as may occur following abdominal or chest surgery), can be reluctant to breathe deeply or frequently. Effective pain management is therefore important.Counting respiratory rate (for 30-60 seconds) is a simple but effective observation. However, if patients are aware their breathing is being counted, this is likely to affect their rate. With conscious and oriented patients, respirations should be counted when the nurse appears to be doing something else, such as taking their pulse.
Respiratory observations are frequently omitted or unrecorded, even when patients have respiratory problems (Kenward et al, 2001). While cyanosis and flaring of the nostrils indicate respiratory distress, and so should be noted and reported, they are both very late and unreliable signs, as they are not always evident despite severe respiratory failure (Darovic, 1997; Mulligan, 2000).
Depth of breaths depends on the space available for lung expansion. This varies between individuals but will also be affected by abnormal pressure of the chest cavity. For example, abdominal distension (which may be caused by conditions such as abdominal bleeding, ascites or pancreatitis) places pressure on the chest cavity, splinting the bases of (usually) both lungs. Anything occupying space in the lungs (such as pleural effusion, pneumothorax, carcinoma) also decreases the size of each breath.
Relatively static lung bases, usually from shallow breathing, provide a warm and moist environment for bacteria to breed, putting the patient at risk of chest infection (Wilson, 2001). Patients should be encouraged to take at least six deep breaths every hour with those at risk of developing an infection referred at an early stage to a physiotherapist. Incentive spirometers (usually provided by physiotherapists) enable patients and staff to see the effectiveness of deep-breathing exercises.
Understanding the significance of breath sounds is a skill that requires practice. However, laboured breathing or wheezing is often audible. More detailed sounds can be heard with a stethoscope. Identifying whether breath sounds are: normal; abnormal; diminished; absent.
Wheeze, crackles and unilateral, bilateral, pos-itional or radiated sounds provide valuable information for further investigation. More detailed interpretation of breath sounds is possible (Darovic, 1997), but this is a specialist skill that many nurses will not need unless they work in critical care environments. Although some problems identified in this section may need prolonged treatment, or be incurable, nurses can use a number of simple strategies to help patients breathe more efficiently.
Ensuring patients are sitting upright rather than lying down enables gravity to assist breathing thereby helping lung expansion (Thelan et al, 1998). Sitting forward, with forearms resting on a table and pillow will further increase lung expansion (Thelan et al, 1998). A few medical conditions, such as spinal injury, will prevent the use of these positions, so nurses should be aware of the patient’s diagnosis before suggesting them.
Work of breathing
Respiratory muscles like any other body tissue require oxygen. Increased work consumes more oxygen. The oxygen demand of respiratory muscle is termed the work of breathing. At rest, respiratory muscle uses 1-3% of total oxygen consumed by the body (Hinds and Watson, 1996), but hypoxia stimulates an increase in respiratory work.
While this increased respiratory work should deliver more oxygen to the body, in respiratory disease this does not always occur - the respiratory system may consume 25-30% of available oxygen (Hinds and Watson, 1996). If respiratory failure prevents any significant increase in arterial oxygen, this increased oxygen consumption may make the rest of the body even more hypoxic.
Room air is about 50% saturated at 20°C (Ballard et al, 1992), so dry gas such as oxygen absorbs moisture from the airway, causing drying of airway epithelium and dysfunction of cilia.
Lack of humidification causes airway damage, so if in doubt it is safer to humidify than to leave gas dry. Prolonged use of high-flow oxygen (above 4 litres per minute) should always be humidified; low-flow oxygen may also need to be humidified.
Warm air can carry more moisture than cold air (Jackson, 1996). So humidifying dry gas with water that is at room temperature will ensure moisture is absorbed from the patient’s airway. Humidifiers should ideally heat water to normal body temperature. However, heated humidification poses some dangers:
- Potential burns from overheated air
- A warm moist environment that can form a reservoir for infection
- Dangers to others from spilt water.
These problems make heated humidification unsuitable for most ward environments.
Drying and cracking of the lips can occur when oxygen is given by facemask, so lips should be kept moist, using an appropriate lubricant, such as white petroleum jelly.
Psychological care should be given for humanitarian and physiological reasons (Lawler, 1997). Breathing is fundamental to life. Severe breathlessness usually causes panic and a physiological stress (‘fight or flight’) response. The negative effects of fear on breathing may be clearly seen in asthma attacks. Prolonged stressful breathing significantly increases oxygen demand, often without significantly increasing supply. Profoundly hypoxic tissue will infarct, eventually leading to organ failure (Hinds and Watson, 1996). Providing a calm, controlled environment is important to reduce fear. Treatments and procedures should be clearly explained, remembering that hypoxia may impair understanding. Alleviating pain (see above) also helps reduce fear and the stress responses (Cheever, 1999).
Family and friends can provide valuable emotional support to patients (Bergbom and Askwall, 2000). They should therefore be given appropriate explanations and encouraged to spend time with patients. Although further discussion of this aspect is beyond the scope of this paper, planned care should also consider the needs of family and friends.
Oxygen is essential for human life. Respiratory failure is usually classed as type 1 (oxygenation failure: hypoxia but normocapnia and type 2 (ventilatory failure: hypoxia and hypercapnia. Either type may be immediately life threatening. Even if not life-threatening, respiratory failure places a strain on body tissues and systems.
The best way to treat respiratory failure will depend on its severity, and the likely benefits and complications of possible interventions. Nurses working in a range of care areas, including hospital and the community, may be the first health-care staff to detect the problem, or may be caring for patients receiving various treatments. They therefore need to understand how to recognise and assess respiratory failure, and how to assess responses to medical interventions.
- This educational hand-out can be photocopied and used in teaching sessions on this subject.
A patient with chronic obstructive pulmonary disease (COPD) is admitted to your ward, with peripheral oxygen saturation (SpO2) of 85%.- How much oxygen would you expect the patient to be prescribed and at what rate?
- Which method of delivery would be the most appropriate in this scenario?
- Identify the rationale for your care.
- Reflect on patients who have significant acute or chronic respiratory problems whom you are currently looking after
- List which of the above factors may impair their surfactant production, and so exacerbate their respiratory limitations
- List the respiratory observations that are made by nurses in your clinical area. After reading the section headlined ‘Rate’, identify further types of observations you think would be useful in your clinical practice
- Share and discuss these ideas with your colleagues
Using a care plan format, list the relevant aspects of care you would provide to a patient receiving humidified oxygen. Include the risks caused by using humidified oxygen and how they can be minimised.
Reflect on patients you have cared for who had respiratory failure. Note any signs they showed of psychological distress/needs.
- How were these needs met in your ward area?
- Has this activity raised any issues you wish to share with your colleagues?
Anderson, K.N., Anderson, L.E., Glanze, W.D. (eds) (1998) Mosby’s Medical Nursing and Allied Health Dictionary. (5th edition) St Louis: Mosby.
Ballard, K., Cheeseman, W., Ripiner, T., Wells, S. (1992)Humidification for ventilated patients. Intensive and Critical Care Nursing 8: 1, 2-9.
Bateman, N.T., Leach, R.M. (1998)Acute oxygen therapy. British Medical Journal 317: 7161, 798-801.
Beers, M.H., Berkow, R. (eds) (1999)The Merck Manual of Diagnosis and and Therapy. USA: Merck & Co.
Bergbom, I., Askwall, A. (2000)The nearest and dearest: a lifeline for ICU patients. Intensive and Critical Care Nursing 16: 6, 384-395.
British Thoracic Society. (2002)Non-invasive ventilation in acute respiratory failure. Thorax 57: 3, 192-211.
Cheever, K.H. (1999)Reducing the effects of acute pain in critically ill patients. Dimensions of Critical Care Nursing 18: 3, 14-23.
Cornock, M.A. (1996)Making sense of arterial blood gases and their interpretation. Nursing Times 92: 6, 30-31.
Crompton, G.K., Haslett, C., Chilvers, E.R. (1999)Diseases of the respiratory system. In: Haslett, C., Chilvers, E.R., Hunter, J.A.A. et al. (eds) Davidson’s Principles and Practice of Medicine. Edinburgh: Churchill Livingstone.
Darovic, G.O. (1997)Physical assessment of the pulmonary system. In: Darovic, G.O. (ed.) Hemodynamic Monitoring: invasive and noninvasive clinical application. (2nd edn) Philadelphia: W.B. Saunders Company.
Guyton, A.C., Hall, J.E. (2000)Textbook of Medical Physiology (10th edn) Philadelphia: W.B. Saunders Company.
Hinds, C.J., Watson, D. (1996)Intensive Care: A conscise textbook. (2nd edition) London: W.B. Saunders.
Jackson, C. (1996)Humidification in the upper respiratory tract: a physiological overview. Intensive and Critical Care Nursing 12: 1, 27-32.
Kenward, G., Hodgetts, T., Castle, N. (2001)Time to put the R back in TPR. Nursing Times 97: 40, 32-33.
Lawler, J. (1997)The Body in Nursing. South Melbourne: Churchill Livingstone.
Lumb, A.B. (2000)Nunn’s Applied Respiratory Physiology (5th edition). Oxford: Butterworth Heinemann.
Marieb, E.N. (2001)Human Anatomy and Physiology. (5th edition) San Francisco: Benjamin/Cummings Publishing Company Inc.
McCaffery, M., Beebe, A. (1994)Pain: Clinical manual for nursing practice. London: Mosby.
Mulligan, P. (2000)Respiratory care. In: Sheppard, M., Wright, M. (eds) High Dependency Nursing. London: Bailliere Tindall.
Thelan, L.A., Urden, L.D., Lough, M.E., Stacy, K.M. (1998)Critical Care Nursing: Diagnosis and management. St Louis: Mosby.
Wilson, J. (2001)Infection Control in Clinical Practice. Edinburgh: Bailliere Tindall.