A person's pulse rate can be influenced by several factors, including age, the person's sex, exercise, temperature, medications, intravascular volume, stress, positioning, pathology, hormones and electrolytes (Marini and Dries [112], Wilkinson et al. [215]). The approximate usual ranges are illustrated in Table 14.1.

The pulse may also vary depending on posture. For example, the pulse of a healthy man may be around 66 beats per minute when he is lying down, but it may increase to 70 beats per minute when he is sitting up and 80 beats per minute when he suddenly stands; in women, the pulse is slightly faster (Marieb and Hoehn [110]).

The pulse rate of an individual with a healthy heart tends to be relatively constant; however, when blood volume drops suddenly or when the heart has been weakened by disease, the stroke volume declines and cardiac output is maintained only by increasing the rate of the heart beat (Tortora and Derrickson [199]).

Cardiac output (CO) is the amount of blood pumped out by each ventricle in 1 minute (Lin [104]). It is the product of heart rate (HR) and stroke volume (SV) (Box 14.1). Stroke volume is defined as the volume of blood pumped out by one ventricle with each beat (Lin [104], Mehta and Arora [115]).

Using normal resting values for HR (75 beats per minute) and SV (70 mL per beat), the average adult cardiac output can be calculated as (Tortora and Derrickson [199]):

The heart rate and therefore pulse rate are influenced by various factors acting through neural, chemical and physically induced homeostatic mechanisms (see Figure 14.5 for factors that increase cardiac output):

Tachycardia is an abnormally fast heart rate, over 100 beats per minute in adults (Wilkinson et al. [215]). It may result from exercise or exertion, an elevated body temperature, stress, certain drugs or heart disease (Marieb and Hoehn [110]). Persistent tachycardia (even at rest) is considered pathological because tachycardia can lead to fibrillation (Marieb and Hoehn [110]).

The pulse rhythm is the sequence of beats, which in health should be regular (Wilkinson et al. [215]). The co‐ordinated action of the muscles of the heart in producing a regular heart rhythm is caused by the ability of cardiac muscle to contract inherently without nervous control (Marieb and Hoehn [110]). The co‐ordinated action of the muscles in the heart results from two physiological factors:

The nodal or conduction system is composed of the sinoatrial node, the atrioventricular node, the atrioventricular bundle and the Purkinje fibres (Marieb and Keller [111]). The sinoatrial node is the pacemaker and initiates each impulse, which leads to a wave of contraction, setting the rhythm for the heart as a whole (Figure 14.6) (Waugh and Grant [207]). A rhythm that is initiated at the sinoatrial node is called ‘sinus rhythm’ (Waugh and Grant [207]).

In patients younger than 40 years, irregularities may be linked to breathing when the heart rate increases on inspiration and decreases on expiration (Blows [21]). Although this is rarely noticeable in adults, it is normal and is known as sinus arrhythmia (Tortora and Derrickson [199]). Defects in the conduction system of the heart can cause irregular heart rhythms, or arrhythmias, which result in unco‐ordinated contraction of the heart (Marieb and Keller [111]). These can be felt when palpating the pulse and can be seen on an ECG tracing.

Amplitude is a reflection of pulse strength and the elasticity of the arterial wall, which varies with alternating strong and weak ventricular contractions (Bickley [18]). In patients with arteriosclerosis, the arteries feel hard and different, in terms of flexibility, when compared to those of young, healthy adults (Tortora and Derrickson [199]). It takes some clinical experience to be able to identify these differences in amplitude; however, it is important to be able to recognize major changes, such as the faint flickering pulse of the severely hypovolaemic patient or the irregular pulse of cardiac arrhythmias (Adam et al. [2]).

Irregular heart rhythms can be present in patients of all age groups regardless of previous medical history or co‐morbidities (Brown and Cadogan [31]). Among all of the different types, atrial fibrillation is the most common, especially in the older population, and it can lead to heart failure and potentially death (Sprigings and Chambers [189]). It starts with a disruption of rhythm in the atrial areas of the heart, occurring at extremely rapid and unco‐ordinated intervals (Wilkinson et al. [215]). The rapid impulses result in the ventricles not being able to respond to every atrial beat and, therefore, the ventricles contract irregularly (Adam et al. [2]). Among the possible causes of atrial fibrillation, some of the most common are ischaemic heart disease, acute illness, electrolyte imbalance and thyrotoxicosis (Marini and Dries [112]); if poorly managed, patients with atrial fibrillation are at increased risk of arterial thromboembolism and stroke (Phang and Manning [161]).

Assessing and detecting abnormalities in the ventricular rate by checking the radial pulse is considered an unreliable method as some contractions may not be strong enough to transmit a pulse wave that is detectable at the radial artery (Sprigings and Chambers [189]). Hence, monitoring of the apex beat and radial pulse is advisable in patients with atrial fibrillation, because it will determine the ventricular rate more reliably and identify whether there is an apex beat–radial pulse deficit (Sprigings and Chambers [189]). This procedure requires two nurses and is described below in the section on assessing gross pulse irregularity. In addition, a 12‐lead ECG should be taken to confirm any arrhythmias (see the section on ECG below).

A paradoxical pulse is a pulse that markedly decreases in amplitude during inspiration (Swanevelder [193]). On inspiration, blood is pooled in the lungs, decreasing the amount of blood that is returned to the left side of the heart; this affects the consequent stroke volume (Marieb and Keller [111]). A paradoxical pulse is usually regarded as normal, although, in conjunction with features such as hypotension and dyspnoea, it may indicate cardiac tamponade, hypovolaemia, severe airway obstruction or tension pneumothorax (Bickley [18]).

When there is a gross pulse irregularity, a stethoscope may be used to assess the apical heartbeat by placing the diaphragm of the stethoscope over the apex of the heart and counting the beats for 60 seconds (Bickley [18]). A second nurse should record the radial pulse at the same time and the deficit between the two should be noted using, for example, different colours on the patient's chart to indicate the apex and radial rates (Jackson [86]).

Co‐morbidities such as atherosclerosis, diabetes, heart failure, and peripheral arterial or vascular disease can affect the blood circulation in the lower limbs (Wilkinson et al. [215]). Palpating the dorsalis pedis pulse (Figure 14.7), which is on the dorsal surface of the foot; the posterior tibial pulse (Figure 14.8), which is located near the Achilles tendon; and the popliteal pulse (Figure 14.9), which is felt at the back of the knee, can provide an insight into the amount of circulatory compromise, if any (Bickley [18]). Where indicated, feeling for the femoral pulses is also of value for an accurate clinical assessment (Bickley [18]).

Inspection is another form of assessment as ischaemia, deep vein thrombosis and any other compromising vascularity illness may cause changes in the warmth and colour of the lower limbs, including in the capillary refill (Bajwa et al. [11]). Patients with certain types of cancer or who have previously had vascular interventions, such as coronary artery bypass, are more prone to circulatory changes in the lower limbs and therefore a precise assessment will prevent complications that may lead to, for example, amputation (Bailey et al. [10]).