Patients who are in hospital should have observations, including respiratory observations, taken and recorded regularly, as follows:

If the patient is acutely ill or at risk of respiratory deterioration, they will require continuous pulse oximetry and frequent respiratory assessment (Tait et al. [194]). Similarly, if the patient is receiving oxygen therapy, they will need to be closely monitored to ensure its efficacy (Marini and Dries [112]). Any patient who has, or is at risk of, chronic hypercapnia should have close monitoring of their respiratory function, with observations performed accordingly (O'Driscoll et al. [147]).

Any healthcare professional who has been trained and assessed as competent can perform a respiratory assessment and pulse oximetry in accordance with local hospital policy.

Although pulse oximetry is a useful tool in the assessment of respiratory status, its limitations should be recognized. One of the main limitations is its inability to reliably detect hypoventilation (particularly in patients receiving supplemental oxygen) and carbon dioxide retention (Lough [105]); the latter is usually confirmed by measurement of PaCO₂ via arterial blood gas analysis (Brown and Cadogan [31]). Likewise, 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 (Adam et al. [2]). Other factors that may affect pulse oximetry readings include the following:

In a conscious patient, a quick way to check airway patency is to ask them a question; a normal verbal response confirms that the patient's airway is clear (this also indicates that they are breathing and that their brain is being perfused) (Goulden and Clarke [74]; see also Chapter c12: Respiratory care, CPR and blood transfusion).

Airway obstruction can have a subtle presentation, with signs and symptoms that depend on the type of obstruction; regardless, it is usually a medical emergency (Brown and Cadogan [31]). A partial airway obstruction, where some air is allowed through, is generally associated with noises such as choking, snoring, hoarseness (harsh, deep voice) or stridor (harsh, high‐pitched sound occurring usually on inspiration) (Wilkinson et al. [215]). In this case, the person may be agitated and panicked. It is important to assess whether there is any obstruction to the patient's airway as a result of vomit, blood, foreign bodies or the patient's tongue (Sprigings and Chambers [189]).

In contrast, in a complete airway obstruction, where there is no air getting through, there will be no breath sounds and the chest will not move (Sprigings and Chambers [189]); the patient will be extremely distressed and, if left untreated, they will lose consciousness quickly. In both cases, the presence of hypoxia implies a medical emergency due to impending respiratory arrest, irrespective of the location of the obstruction (upper or lower airway) (Adam et al. [2]). Its management can include the Heimlich manoeuvre (a technique used to release foreign objects from a person's airway), epinephrine injection (used to reverse airway swelling caused by an allergic reaction) and CPR (Brown and Cadogan [31]).

Breathing assessment is required to assess the patient's ability to adequately ventilate; it starts by observing the patient and how they breathe (Bickley [18]). It is important that the following aspects are observed:

Cyanosis is a blue tone to the skin and mucous membranes, which may occur when high levels of unsaturated haemoglobin are present in the blood; it may be detectable when oxygen saturation of arterial blood drops below 90% (Peate and Wild [157]). Cyanosis is, however, often considered a late sign of respiratory deterioration and may be difficult to detect, particularly in artificial lighting (Brown and Cadogan [31]). There are two types of cyanosis: central, affecting the lips and oral mucosa, usually indicating cardiorespiratory insufficiency, and peripheral, observed in the skin and nail beds, usually indicating poor peripheral circulation if seen in isolation (Wilkinson et al. [215]). Patients who are anaemic may not be cyanotic as there is insufficient haemoglobin to generate the blue tone (Adam et al. [2]). Similarly, a pale skin tone may indicate that the patient is anaemic or in shock (Bickley [18]).

The use of accessory muscles (such as the sternocleidomastoid, scalene, trapezius and abdominals) to increase inspiration may suggest that the patient has difficulty breathing and is in respiratory distress (Bickley [18]). Observe the patient's neck during inspiration to see whether there is any contraction of the sternomastoid or other accessory muscles (Cleave [45]). In addition, some patients may breathe through pursed lips in an attempt to increase resistance on expiration, which helps to keep the alveoli open, or have nasal flaring as they attempt to force more air into their lungs (Bickley [18]).

The normal respiratory rate in adults is 12–18 breaths per minute with expiration lasting approximately twice as long as inspiration (Peate and Wild [157]). The rate should be counted for one full minute to fully assess both the rate and the rhythm (Bickley [18]). An increase from the patient's normal respiratory rate by as little as 3–5 breaths per minute is an early and important sign of respiratory distress or acute illness (Blows [21]). Patients with a respiratory rate greater than 21 breaths per minute should have frequent observations and be closely monitored; if they also have other physiological alterations, they should receive prompt medical attention, as should all patients with a respiratory rate greater than 25 breaths per minute (RCP [171]). Respiratory rates of 9 or less also require urgent medical care (RCP [171]). Respiratory rate can be classified as follows:

The respiratory assessment should also consider the shape and expansion of the chest (Bickley [18]). The anteroposterior diameter of the chest wall may give an indication of underlying respiratory conditions or other problems (Brown and Cadogan [31]); it may change with age or increase in chronic pulmonary disease (Bickley [18]). It is also important to view the way the chest expands with each breath; when normal, it should be equal and bilateral (Sprigings and Chambers [189]). Any paradoxical movements – such as only one side of the chest moving, greater movement on one side, or one side moving up and the other moving down – should be noted as they can indicate a particular problem with one side of the chest (Adam et al. [2]). Asymmetrical chest expansion is abnormal and may indicate pleural disease, pulmonary fibrosis, collapse of upper lobes or bronchial obstruction; spinal deformities such as kyphosis also influence lung expansion (Wilkinson et al. [215]).

Following the above – and if a more thorough assessment is required in order to assess the patient's ability to adequately ventilate – percussion, palpation and auscultation of the chest should be performed (Adam et al. [2]). These assessment techniques will enable the identification of any added or absent breath sounds that may indicate lung abnormalities (such as an infection or pneumothorax).

In addition, respiratory assessment involves assessing the entire patient for other signs or symptoms, such as high temperature (which may be suggestive of pneumonia), increased pulse (which may indicate cardiovascular disease) and low blood pressure (which may indicate sepsis) (Bickley [18]). The patient's level of consciousness should also be assessed, including how alert and orientated they are and whether they appear to be distressed (Peate and Wild [157]). If the patient can only speak in very short sentences or can only say a few words without needing to stop to breathe, then they are in respiratory distress (Bickley [18]).