Vital Signs

Introduction

Vital signs include the measurement of: temperature, respiratory rate, pulse, blood pressure and, where appropriate, blood oxygen saturation. These numbers provide critical information (hence the name “vital”) about a patient’s state of health. In particular, they:

1. Can identify the existence of an acute medical problem.
2. Are a means of rapidly quantifying the magnitude of an illness and how well the body is
   coping with the resultant physiologic stress. The more deranged the vitals, the sicker the
   patient.
3. Are a marker of chronic disease states (e.g. hypertension is defined as chronically elevated blood pressure).

Most patients will have had their vital signs measured by an RN or health care assistant before you have a chance to see them. However, these values are of such great importance that you should get in the habit of repeating them yourself, particularly if you are going to use these values as the basis for management decisions. This not only allows you to practice obtaining vital signs but provides an opportunity to verify their accuracy. As noted below, there is significant potential for measurement error, so repeat determinations can provide critical information.

Getting Started

The examination room should be quiet, warm and well lit. After you have finished interviewing the patient, provide them with a gown (a.k.a. “Johnny”) and leave the room (or draw a separating curtain) while they change. Instruct them to remove all of their clothing (except for briefs) and put on the gown so that the opening is in the rear. Occasionally, patient’s will end up using them as ponchos, capes or in other creative ways. While this may make for a more attractive ensemble it will also, unfortunately, interfere with your ability to perform an examination! Prior to measuring vital signs, the patient should have had the opportunity to sit for approximately five minutes so that the values are not affected by the exertion required to walk to the exam room. All measurements are made while the patient is seated.

Observation

Before diving in, take a minute or so to look at the patient in their entirety, making your observations, if possible, from an out-of-the way perch. Does the patient seem anxious, in pain, upset? What about their dress and hygiene? Remember, the exam begins as soon as you lay eyes on the patient.

Temperature

This is generally obtained using an oral thermometer that provides a digital reading when the sensor is placed under the patient’s tongue. As most exam rooms do not have thermometers, it is not necessary to repeat this measurement unless, of course, the recorded value seems discordant with the patient’s clinical condition (e.g. they feel hot but reportedly have no fever or vice versa). Depending on the bias of a particular institution, temperature is measured in either Celcius or Farenheit, with a fever defined as greater then 38-38.5 C or 101-101.5 F. Rectal temperatures, which most closely reflect internal or core values, are approximately 1 degree F higher then those obtained orally.

Respiratory Rate

Respirations are recorded as breaths per minute. They should be counted for at least 30 seconds as the total number of breaths in a 15 second period is rather small and any miscounting can result in rather large errors when multiplied by 4. Try to do this as surreptitiously as possible so that the patient does not consciously alter their rate of breathing. This can be done by observing the rise and fall of the patient’s hospital gown while you appear to be taking their pulse. Normal is between 12 and 20. In general, this measurement offers no relevant information for the routine examination. However, particularly in the setting of cardio-pulmonary illness, it can be a very reliable marker of disease activity.

Pulse

This can be measured at any place where there is a large artery (e.g. carotid, femoral, or simply by
listening over the heart), though for the sake of convenience it is generally done by palpating the radial
impulse. You may find it helpful to feel both radial arteries simultaneously, doubling the sensory input and helping to insure the accuracy of your measurements. Place the tips of your index and middle fingers just proximal to the patients wrist on the thumb side, orienting them so that they are both over the length of the vessel.

Vascular Anatomy	The location of the radial artery (surface anatomy on the left, gross anatomy on the right)	Technique for Measuring the Radial Pulse

Frequently, you can see transmitted pulsations on careful visual inspection of this region, which may
help in locating this artery. Upper extremity peripheral vascular disease is relatively uncommon, so the radial
artery should be readily palpable in most patients. Push lightly at first, adding pressure if there is a lot of subcutaneous fat or you are unable to detect a pulse. If you push too hard, you might occlude the vessel and mistake your own pulse for that of the patient. During palpation, note the following:

1. Quantity: Measure the rate of the pulse (recorded in beats per minute). Count for 30 seconds
   and multiply by 2 (or 15 seconds x 4). If the rate is particularly slow or fast, it is probably best to measure for a full 60 seconds in order to minimize the impact of any error in recording over shorter periods of time. Normal is between 60 and 100.
2. Regularity: Is the time between beats constant? In the normal setting, the heart rate should
   appear metronomic. Irregular rhythms, however, are quite common. If the pattern is entirely chaotic with no discernable pattern, it is referred to as irregularly irregular and likely represents atrial fibrillation. Extra beats can also be added into the normal pattern, in which case the rhythm is described as regularly irregular. This may occur, for example, when impulses originating from the ventricle are interposed at regular junctures on the normal rhythm. If the pulse is irregular, it’s a good idea to verify the rate by listening over the heart (see cardiac exam section). This is because certain rhythm disturbances do not allow adequate ventricular filling with each beat. The resultant systole may generate a rather small stroke volume whose impulse is not palpable in the periphery.
3. Volume: Does the pulse volume (i.e. the subjective sense of fullness) feel
   normal? This reflects changes in stroke volume. In the setting of hypovolemia,
   for example, the pulse volume is relatively low (aka weak or thready). There
   may even be beat to beat variation in the volume, occurring occasionally with
   systolic heart failure.

Blood Pressure

Blood pressure (BP) is measured using mercury based manometers, with readings reported in millimeters of mercury (mm Hg). The size of the BP cuff will affect the accuracy of these readings. The inflatable bladder, which can be felt through the vinyl covering of the cuff, should reach roughly 80% around the circumference of the arm while its width should cover roughly 40%. If it is too small, the readings will be artificially elevated. The opposite occurs if the cuff is too large. Clinics should have at least 2 cuff sizes available, normal and large. Try to use the one that is most appropriate, recognizing that there will rarely be a perfect fit.

1. Wrap the cuff around the patient’s upper arm so that the line marked “artery”
   is roughly over the brachial artery, located towards the medial aspect of
   the antecubital fossa (i.e. the crook on the inside of their elbow). The placement
   does not have to be exact nor do you actually need to identify this artery
   by palpation.

   Antecubital Fossa

   The antecubital fossa anatomy (surface anatomy on the left, gross anatomy on the right)

2. Put on your stethescope so that the ear pieces are angled away from your
   head. Twist the head piece so that the diaphragm is engaged. This can be verified
   by gently tapping on the end, which should produce a sound. With your left
   hand, place the diaphragm over the area of the brachial artery. While most
   practitioners use the diaphragm of the stethescope, the bell may actually
   be superior for picking up the low pitched sounds used for measuring BP. Experiment
   with both and see if this makes a difference. It’s worth mentioning that a
   number of different models of stethescops are available on the market, each
   with its own variation on the structure of the diaphragm and bell. Read the
   instruction manual accompanying your stethoscope in order to determine how
   your device works.
3. Grasp the patient’s right elbow with your right hand and raise their arm so that the brachial
   artery is roughly at the same height as the heart. The arm should remain somewhat bent and
   completely relaxed. You can provide additional support by gently trapping their hand and forearm
   between your body and right elbow. If the arm is held too high, the reading will be artifactually
   lowered, and vice versa.
4. Turn the valve on the pumping bulb clockwise (may be counter clockwise in some cuffs) until
   it no longer moves. This is the position which allows air to enter and remain in the bladder.
5. Hold the diaphragm in place with your left hand. Use your right hand to pump
   the bulb until you have generated 150 mmHg on the manometer. This is a bit above the top end of
   normal for systolic blood pressure (SBP). Then listen. If you immediately hear sound, you have
   underestimated the SBP. Pump up an additional 20 mmHg and repeat. Now slowly deflate the
   blood pressure cuff (i.e. a few mm Hg per second) by turning the valve in a counter-clockwise
   direction while listening over the brachial artery and watching the pressure gauge. The first sound
   that you hear reflects the flow of blood through the no longer completely occluded brachial artery.
   The value on the manometer at this moment is the SBP. Note that although the needle may
   oscillate prior to this time, it is the sound of blood flow that indicates the SBP.
6. Continue listening while you slowly deflate the cuff. The diastolic blood
   pressure (DBP) is measured when the sound completely disappears. This is the
   point when the pressure within the vessel is greater then that supplied by
   the cuff, allowing the free flow of blood without turbulence and thus no audible
   sound. These are known as the Sounds of Koratkoff.Technique for Measuring Blood Pressure 

7. Repeat the measurement on the patient’s other arm, reversing the position of your hands.
   The two readings should be within 10-15 mm Hg of each other. Differences greater then this imply that there is differential blood flow to each arm, which most frequently occurs in the setting of subclavian artery atherosclerosis.
8. Occasionally you will be unsure as to the point where systole or diastole occurred and wish to repeat the measurement. Ideally, you should allow the cuff to completely deflate, permit any venous congestion in the arm to resolve (which otherwise may lead to inaccurate measurements), and then repeat a minute or so later. Furthermore, while no one has ever lost a limb secondary to BP cuff induced ischemia, repeated measurement can be uncomfortable for the patient, another good reason for giving the arm a break.
9. Avoid moving your hands or the head of the stethescope while you are taking readings as this
   may produce noise that can obscure the Sounds of Koratkoff.
10. You can verify the SBP by palpation. To do this, position the patient’s right arm as described above. Place the index and middle fingers of your right hand over the radial artery. Inflate the cuff until you can no longer feel the pulse, or simply to a value 10 points above the SBP as determined by auscultation. Slowly deflate the cuff until you can again detect a radial pulse and note the reading on the manometer. This is the SBP and should be the same as the value determined with the use of your stethescope.

Normal is between 100/60 and 140/90. Hypertension is thus defined as either SBP greater then 140 or DBP greater than 90. It is important to recognize that blood pressure is rarely elevated to a level that causes acute symptoms. That is, while hypertension in general is common, emergencies resulting from extremely high values and subsequent acute end organ dysfunction are quite rare. Rather, it is the chronically elevated
values which lead to target organ damage, though in a slow and relatively silent fashion. At the other end
of the spectrum, the minimal SBP required to maintain perfusion varies with the individual. Therefore, interpretation of low values must take into account the clinical situation. Those with poorly functioning hearts, for example, can adjust to a chronically low SBP (e.g. 80-90) and live without symptoms of hypoperfusion. However others, used to higher baseline values, might become quite ill if their SBPs were suddenly decreased to these same levels.

Many things can alter the accuracy of your readings. In order to limit their impact, remember the following:

1. Do not place the blood pressure cuff over a patients clothing or roll a tight fitting sleeve above their biceps when determining blood pressure as either can cause elevated readings.
2. Make sure the patient has had an opportunity to rest before measuring their BP. Try the following
   experiment to assess the impact that this can have. Take a patient’s BP after they’ve rested. Then repeat after they’ve walked briskly in place for several minutes. Patients who are not too physically active (i.e. relatively deconditioned) will develop an elevation in both their SBP and DBP. Also, see what effect raising or lowering the arm, and thus the position of the brachial artery relative to the heart, has on BP. If you have a chance, obtain measurements on the same patient with both a large and small cuff. These exercises should give you an appreciation for the magnitude of error that can be introduced when improper technique is utilized.
3. If the reading is surprisingly high or low, repeat the measurement towards the end of your exam.
4. Instruct your patients to avoid coffee, smoking or any other unprescribed
   drug with sympathomimetic activity on the day of the measurement.
5. Orthostatic (a.k.a. postural) measurements of pulse and blood pressure are part of the assessment for hypovolemia. This requires first measuring these values when the patient is supine and then repeating them after they have stood for 2 minutes, which allows for equilibration. Normally, SBP does not vary by more then 20 points when a patient moves from lying to standing. In the setting of significant volume depletion, a greater then 20 point drop may be seen. Changes of lesser magnitude occur when moving from lying to sitting or sitting to standing. This is frequently associated with symptoms of cerebral hypoperfusion (e.g..
   light headedness). Heart rate should increase by more then 20 points in a normal physiologic attempt to augment cardiac output by providing chronotropic compensation. In the setting of GI bleeding, for example, a drop in blood pressure and/or rise in heart rate after this maneuver is a marker of significant blood loss and has important prognostic implications. Orthostatic measurements may also be used to determine if postural dizziness, a common complaint with multiple possible explanations, is the result of a fall in blood pressure. For example, patients who suffer from diabetes frequently have autonomic nervous system dysfunction and cannot generate appropriate arteriolar vaosconstriction when changing positions. This results in postural vital sign changes and symptoms. The 20 point value is a rough guideline. In general, the greater the change, the more likely it is to cause symptoms and be of clinical relevance.
6. If possible, measure the blood pressure of a patient who has an indwelling arterial catheter (these
   patients can be found in the ICU with the help of a preceptor). Arterial transducers are an extremely accurate tool for assessing blood pressure and therefore provide a method for checking your non-invasive technique.

Oxygen Saturation

Over the past decade, this non-invasive measurement of gas exchange and red blood cell oxygen carrying capacity has become available in all hospitals and many clinics. While imperfect, it can provide important information about cardio-pulmonary dysfunction and is considered by many to be a fifth vital sign. In particular, for those suffering from either acute or chronic cardio-pulmonary disorders, it can help quantify the degree of impairment.