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(AP) diameter which may give an indication of underlying respiratory conditions or problems (Higginson and Jones 2009). The AP diameter may change with ageing, and it might also increase in chronic pulmonary disease (Bickley and Szilagyi 2009). As well as observing the shape of the chest wall, it is also important to view the way the chest expands with each breath; when normal, it should be equal and bilateral (Higginson and Jones 2009). Any paradoxical movements should be noted as they can indicate a particular problem with one side of the chest (Higginson and Jones 2009).

Pulse oximetry

This is a continuous and noninvasive monitor which measures the oxygen saturation of the patient (Higginson and Jones 2009). These devices work by measuring the colour of the blood as oxyhaemoglobin is a brighter red than haemoglobin; from this, the device can work out what percentage of the haemoglobin is oxygenated (Davies and Moores 2003). A normal oxygen saturation will range between 95% and 100% (Parkman 2007) but patients with chronic respiratory conditions may have lower oxygen saturations which have become ‘normal’ for them (Higginson and Jones 2009). Therefore, the patient’s doctor should specify what saturation is acceptable for patients with chronic respiratory conditions (Levine 2007).

The British Thoracic Society states that oxygen saturation should be kept at 94–98% for acutely ill adults and 88–92% for those at risk or known to have hypercapnia (O’Driscoll et al. 2008). In patients who are not hypoxic, a sudden drop of greater than 3% of their oxygen saturation should prompt the nurse to check that the device is working correctly and, if so, to undertake further assessment into the patient’s condition (O’Driscoll et al. 2008). Arterial blood gases also produce a reading of oxygen saturation, but the use of pulse oximetry may reduce the need for arterial samples to be taken (Simpson 2006).

General condition or distress of the patient

Respiratory assessment also involves assessing the entire patient for other signs or symptoms of respiratory insufficiency; these include assessing the level of consciousness of the patient, how alert and orientated they are and if they appear distressed (Docherty 2002). If the patient can only speak in very short sentences or only a few words without needing to stop to breathe then they are in respiratory distress (Higginson and Jones 2009).

Preprocedural considerations

Equipment

Pulse oximeter

In order to achieve a successful reading, the sensor of the pulse oximeter should be placed in the best location to achieve the reading. Therefore the sensor may be attached to the patient’s fingers, ears, toes or nose (Higginson and Jones 2009, Moore 2004a). The sensor contains one red lightemitting diode and one infrared lightemitting diode, placed opposite a photodetector which measures the light of both frequencies absorbed by oxyhaemoglobin and deoxyhaemoglobin (Moore 2004a). Pulse oximetry does not give an indication of haemoglobin so if the patient is profoundly anaemic then their oxygen saturation may be normal but they may still be hypoxic (Levine 2007).

Pulse oximetry should not be used if there is a risk of light interference from surgical lamps, infrared warming lamps or even direct sunlight (Adam and Osborne 2005). It should not be used in patients with carbon monoxide poisoning as the device cannot differentiate between carbon monoxide and oxygen. Smoke inhalation causes similar problems so pulse oximetry should be cautiously (Levine 2007).

Specific patient preparations

Positioning of the patient can help ease any respiratory distress and facilitate the assessment and observation of their breathing (Moore 2004b). The patient should be positioned upright, if this is not contraindicated, with their head slightly forward and it may be useful to remove clothing from their thorax to aid with observation of their breathing (Moore 2004b). Positioning can also help to relax the patient and therefore potentially reduce the distress resulting from breathlessness (Gosselink et al. 2008).