Vital Signs: Respiratory Rate

There  is  only  limited  research  relating  to monitoring  respiratory  rate,  and  these studies  focused  on  issues  such  as  the inaccuracy of respiratory rate measurement and  respiratory  rate  as  a  marker  for respiratory dysfunction. 

Inaccuracies  in  respiratory  measurement have  been reported in the literature. One study  compared  respiratory  rate  counted using a 15 second count  period, to  a full minute,  and  found  significant  differences in the rates. Respiratory rates measurement in children under five years, for a 30 second  or  60  second  period,  suggesting the 60 seconds resulted in the least variability. 

Another study found that rapid respiratory rates  in  babies,  counted  using  a  stethoscope, were 20% to 50% higher than those counted from beside the cot without the aid of the stethoscope. 

The value of respiratory rate as an indica- tor of potential respiratory dysfunction has been investigated but findings suggest it is of limited value. One study found that only 33% of people presenting to an emergency department  with  a  oxygen  saturation  below 90% had an increased respiratory rate. 

An  evaluation  of  respiratory  rate  for  the differentiation  of  the  severity  of  illness  in babies under  6 months found it  not  to be very useful. Approximately half of the babies  had  a  respiratory  rate  above  50 breaths per minute, thereby questioning the value  of having a "cut-off" at 50 breaths per minute as the indicator of serious respiratory illness. It has also been reported that factors such as crying, sleeping, agitation and age have a significant influence on the respiratory rate. As a result of these and  similar  studies  the  value  of  respiratory rate as an indicator of serious illness is limited.

Vital Signs: Pulse Rate

There  has  been  very   little  research evaluating the measurement of pulse rates. It  is  likely,  that  when  heart  rate  is  of concern,  cardiac  monitors  are  used  to determine not  only rate, but  also rhythm. The  role  of the "pattern of the pulse", for example  regular  pulse  versus  irregular pulse  or  strong  pulse  versus  weak  pulse, have not been addressed in the context of vital signs or patient observations. On this basis,  an  important  role  of  pulse  rate monitoring will likely be  to  identify when more advanced monitoring is required. 

Measurement  of  a  person's  pulse  rate  in the  presence  of  atrial  fibrillation  was evaluated  and  results  suggest  that  pulse rate,    measured    apically    using    a stethoscope for a 60 second count period, is likely to be the most accurate rate. This study  noted  that  86%  of  nurses  underestimated  the  pulse  rate,  and  that  as  the heart rate increased the magnitude of error also      increased.      Another      study recommended a 30 second count  period as the most accurate and efficient way of measuring  pulse  rate,  noting  that  the  15 second count time was the least accurate. A  third  study  found  that  there  was  no advantage in using the longer 60 seconds, over  the  15 or  30 second count  periods. These researchers suggest that counting an accurate pulse rate may be more difficult than commonly recognised. 

A study assessing infants apical pulse rate using a stethoscope, suggested that length of  time  may  not  be  the  primary  factor  in errors, and that like respiratory rate, pulse rate also appears to be influenced by infant states in addition to illness.

While these studies have identified that the accuracy  of  pulse  rate  measurements  is influenced by the number of seconds that the   pulse   is   counted,   the   clinical significance of these findings is unclear. The contradictory  findings  of  studies  suggest that  the  count  period  used  to  determine pulse rate is of only limited significance.

Vital Signs : Temperature measurement

The largest volume of research identified during the  literature search   addressed   various aspects     of      temperature measurement.  These  studies highlight  the  large  range  of methods  and  body  sites  that are used for the measurement of  temperature  (see  table three).  Because  of  the  volume of  research,  comparisons  of different  temperature measurement  methods  will  be summarised  as  a  separate systematic review. Summarised in  this  practice  information sheet  are  studies  addressing aspects of oral, rectal axillary and tympanic temperatures. 

General Issues

While  much  attention  has focused   on   measurement accuracy, one study evaluated touch as a screen for fever and found  that  while  mothers  and medical students overestimated the  incidence  of  fever  when using touch, they rarely missed its  presence  in  a  child.  The results  of  this  study  perhaps challenge  the  current  focus  of research  on  the  accuracy  of measurements  using  tenths  of a  degree,  when  simple  touch is  an  accurate  measure  for fever.  The  use  of  temperature as a discharge criterion for an ambulatory  surgical  unit  has been   studied,   but   results suggest  it  is  not  useful  in neither     rapid     or     deep differentiating  readiness  for Oral Temperatures Studies  evaluating  measurements from the different areas of the mouth recommend using either the right or left posterior sublingual  pocket,  as  these result   in   higher   recorded temperatures. 

Evaluation  of  the  impact  of oxygen    therapy    on    oral temperatures  have  reported contradictory results regarding its  statistical  significance, however  no  study  reported  a clinically  significant  effect. 

Similarly, different  rates  of oxygen flow, from 2 litres to 6 litres per minute, and warmed or  cooled  inspired  gas,  were found not to have an influence on oral temperature measurements.  Two  studies found  that  rapid  respiratory rates had a small influence on oral  temperatures,  but  these results  were  contradicted  by another   study   that   found breathing,     alone     or in combination, had any significant   effect   on   oral temperatures.

Studies   have   shown   that drinking hot or cold water has a    significant    impact    on recorded  oral  temperatures, and  it  has  been  suggested waiting 15 to 20 minutes after drinks  to  ensure  accuracy. Smoking does not change oral temperature measurements.

Researchers have evaluated the of the temperature accuracy time  required  for  mercury thermometers  to  accurately record   the   person's   oral temperature. One study found that with healthy adults, using a  two  minute  insertion  time resulted    in    27%    of    the temperature  readings  having an  error  of  at  least  0.3°C.  A study  assessing  thermometer insertion  time  in  afebrile  and febrile adults, suggested a six minute  insertion  time  as  a compromise  between  optimal time  and  clinical  practicality while another recommended a seven minute insertion time to ensure the majority of afebrile and  febrile  temperatures  are correctly recorded. However, a survey  of  nurses  showed  that most     left     the     mercury thermometer  in  the  mouth  for less than 3 minutes.

Axillary Temperature

There has been only limited re- search  focusing  on  axillary temperatures.   One   study evaluated axillary temperature measurements  in  elderly  females, and found great variation  between  individuals.

While  the mean axillary temperatures were approximately 36°C, the wide range of tem- peratures  encountered  prevented  the  identification  of  a single figure that could be considered  the  "normal"  axillary temperature.  Another  study evaluated  the  influence  of  intravenous infusions, via upper limbs of neonates, on axillary temperatures and found there was little significance in terms

Tympanic Temperature

There has been considerable research addressing tympanic temperature measurements ranging from the influence of infection and cerumen on measurement accuracy, to optimal technique. Studies have evaluated the impact of otitis media on tympanic temperatures and suggest it has little effect. While some studies have reported a statistically significant difference in tympanic temperatures between ears in people with unilateral otitis media, this difference was approximately 0.1°C and so of little clinical importance. The presence of cerumen  does  influence  tympanic  temperature  readings,  and  while  results  are  variable,  they  suggest  a significant  proportion  of the  temperature readings taken from  the occluded ear  will be  more  than 0.3°C lower than the ear that is not occluded.

Studies  evaluating  technique  suggest  an  ear  tug  should  be  used  during  the  measurement  of  tympanic temperatures, as this is reported to straighten the external auditory canal. Failure to use the ear tug means infrared thermometers are only partially directed at  the  tympanic membrane. The tug technique  in adults has  been described  as  pulling  the  pinna  (auricle  of  ear)  in  an  upward  and  backward  direction,  and  in infants it is pulling the pinna in a backward direction.

Evaluations  of  the  impact  of  ambient  temperatures  on  tympanic  temperatures  suggest  that  while  a  hot environment can significantly affect readings, cold appears to have little effect.

Cost  analyses of the different  temperature measurement methods suggest  infrared measurements may be the  most  cost  effective  despite  the  greater  initial  costs.  These  savings  are  the  result  of  the  rapid  reading capabilities of these instruments, and the labour cost savings that result.

Rectal Temperature

Many  studies  have  compared  the  different  methods  of  temperature  measurement,  and  commonly  rectal temperatures are used as the standard comparison. However, these studies will be summarised in a separate systematic  review.  The  most  common  reported issue  related  to  rectal temperature  measurement  is  that  of rectal perforation, which appears to be a risk primarily for the newborn and very young. Other reported complications include peritonitis secondary to rectal perforation, and one case of intra-spinal migration of a rectal thermometer in a two year old, which broke during routine rectal temperature measurement. A ten year  review of hospital records identified 16 children admitted to a surgical unit  with broken or  retained rectal thermometers. In response to this problem axillary temperature measurements have been recommended in  preference  to  the  rectal  measurements.  With  the  advent  of  infrared  tympanic  thermometers,  these complications are likely to become less common.

Vital Signs: Blood Pressure Measurement

Studies  addressing  the  measurement  of blood pressure with a sphygmomanometer have  focused on issues such as the  accuracy of indirect blood pressure, palpation versus  auscultation  cuff  size,  position  of arm during measurements and health care workers technique. 

Direct versus Indirect

Several studies have compared direct (intra-arterial)  and  indirect  (auscultation) measurements  of  blood  pressure.  There appears  to  be  little  significant  difference in  systolic  pressures  measured  by  either method,  with  differences  ranging  from  3 mmHg in two studies to 12mmHg in a third.

Differences in diastolic blood pressure are greater, and  are  influenced  by  the  refer- ence point that is used. When the phase V Korotkoff's sound is used (disappearance of the sound), both methods provide similar pressures. However when the phase IV Korotkoff's sound (muffling), is used, auscultated measurements are significantly greater  than  intra-arterial  pressures  (see table  one).  A  study  in  children  reported the use of either auscultation or palpation overestimated systolic pressure. See table two for current recommended practice for the measurement of blood pressure.

Palpation versus Auscultation

A comparison between systolic blood pressure  measurements  taken  by  auscultation and  palpation  found  both  were  within  8 mmHg. While palpation has been commonly limited to the measurement of systolic blood pressure,  one  study  reported  that  diastolic pressures could be accurately palpated using the brachial artery to identify the sharp phase  IV  Korotkoff's  sound,  However,  the value  of  this  technique  in  clinical  practice, and its accuracy when used by health care workers, has yet to be demonstrated.

Cuff Size

The length and width of the inflatable cuff (bladder)   that   is   used   during   the measurement of blood pressure may be a source of error. Much of the research has focused on  cuff  width,  (the  dimension across along the bladder) as the potential source of this error. The standard width of currently available cuffs is approximately 12cm, with both larger and smaller sizes also available. Studies have shown that the use  of  a cuff  that  is  too  narrow  results in an overestimation of blood pressure, and a cuff that is too wide underestimates blood pressure.  Length of cuff  appears  to  have little influence on accuracy.

For  obese  people  it  has  been  suggested that  large  cuffs  (15cm  width)  will  be required    when    the    person's    arm circumferences is between 33 -35cm, and a thigh cuff (18cm width) may be needed if  the  arm  circumferences  is  greater  than 41cm.  However,  difficulties  in  applying thigh cuffs to large arms have been reported. Cuff width may also be important when  measuring   blood   pressure   in neonates  and  a  cuff    width  equal  to approximately     50%     of     the     arm circumference has been recommended.

Arm and Body Position

Comparisons of blood pressures measured in  the  sitting  person  with  their  arm  supported  horizontally  or  with  the  arm  resting  at  their  side,  have  found  an average difference in systolic pressure of 11mmHg and diastolic pressure of 12mmHg. When the  arm  was  placed  above  or  below  the level  of  the  heart,  blood  pressure  measurements   changed   by   as   much   as 20mmHg. As a result  of  this, it  has been recommended  that  blood  pressures  be taken in the sitting position with arm supported horizontally at approximately heart level.

Bell versus Diaphragm

The accuracy of blood pressures measured with  the  bell  or  the  diaphragm  of  the stethoscope  have been investigated. One study  found  the  bell  of  the  stethoscope resulted  in  higher  readings  than  those taken using the  diaphragm. These  results were  supported  by  another  study,  with researchers recommending the use of the bell for all blood pressure measurements. 

Health Care Workers Technique

The  technique  used by  health care  workers  to  measure  blood  pressure  has  been shown to differ from recommended practice.  Using  the  American  Heart  Association Guidelines as the standard, one  study found that 57% of nursing students failed to  comply  with  these  guidelines  in  areas such  as  cuff  placement,  estimation  of systolic pressure by palpation, calculation of  proper  inflation  pressure,  and  proper stethoscope  placement.  Another  study  of 172  health  care  workers  concluded  that nurses  and  physicians  evaluated  blood pressure in an inadequate, incorrect and inaccurate way, and that only 3% of general  practitioners  and  2%  of  nurses  obtained reliable  results. Two studies evaluating  the  impact  of  education  programs on  blood  pressure  measurement,  found they increased agreement between the different  blood  pressure  readings  and  also significantly reduced differences in operator technique.

Limitations

A  descriptive  study  of  blood  pressures in critically  ill  patients  who  had  suffered  a cardiac arrest highlighted some limitations to these measurements. Of the 15 patients investigated,  5  patients  had  adequate intra-arterial   blood   pressures,   but unreadable  cuff  pressures.  Four  patients had  cuff  pressures  approaching  normal, but had an inadequate cardiac output. This study suggests that indirect blood pressure measurements  do  not  always  accurately reflect haemodynamic status of critically ill people.

Diabetes mellitus (DM)

Diagnosis (confirm with the same test on another day)

Symptoms of diabetes

·         Polyuria

·         Polydipsia

·         Weight loss

·         Nocturia

·         Polyphagia

·         Blurry vision

·         PLUS random plasma Glucose ε 11.1 mmol/L (200 mg/dL) OR FBS ε 7.0 mmol/L (126 mg/dL) OR plasma glucose value ε 11.1 mmol/L (200 mg/dL) during two hour OGTT

Diagnostic testing

• Fasting blood glucose (FBG): best drawn the morning after overnight fast

• Oral glucose tolerance test (OGTT): 75 g glucose ingested, then plasma glucose levels measured following 0 and 120 minutes

Classification of Diabetes mellitus

Diabetes Secondary to Specific Etiologies

1.       Genetic

• Down syndrome, Turner’s syndrome, Huntington’s disease, genetic defects in ß-cell function and insulin action

2.       Diseases of the endocrine/exocrine pancreas

• Pancreatitis, neoplasia, cystic fibrosis (CF), hemochromatosis (bronzed diabetes)

3.       Endocrinopathies

• acromegaly, Cushing’s syndrome, glucagonoma, hyperthyroidism

4.       Drug-induced

• ß-agonists, glucocorticoids, thiazides, phenytoin

5.       Infections

• Cytomegalovirus (CMV), congenital rubella

Gestational Diabetes (GDM)

Glucose intolerance that develops during pregnancy

Incidence

• 2-4% of all pregnancies

Risk factors

• Age > 25 • member of high-risk ethnic group

• Obesity

• Previous GDM

• 1º relative with DM

• Previous macrosomic baby (> 4 kg)

Screening and diagnosis

• Any pregnant woman should be screened between 24 and 28 weeks

• 50 g glucose challenge test, measuring glucose one hour later

• If abnormal (7.8 mmol/L; 140 mg/dL), then 75 g oral glucose tolerance test (OGTT) should be done

• If any two of the following three values are met or exceeded, a diagnosis of GDM is established

• Fasting glucose ε 5.3 mmol/L (95 mg/dL)

• 1 hr value ε 10.6 mmol/L (190 mg/dL)

• 2 hr ε 8.9 mmol/L (160 mg/dL)

Fetus

Maternal hyperglycemia induces hyperinsulinemia in fetus results in macrosomia (insulin acts as a growth factor)

GDM: prone to respiratory distress, neonatal hypoglycemia, hypocalcemia, hyperbilirubinemia, polycythemia, and prematurity

Preexisting DM: all of the above plus intrauterine growth restriction (IUGR), sacral agenesis, cardiac structural defects

Mother

 Increased risk of developing subsequent type 2 DM

Progression of diabetic retinopathy and nephropathy

Management

• Preconception care to normalize HbA1c (if preexisting DM)

• Tight glucose control (shown to decrease both fetal and maternal complications)

• Oral hypoglycemics contraindicated

• Insulin to maintain tight glycemic control if diet inadequate

• Fetus must be monitored carefully

Impaired Glucose Tolerance (IGT)

Diagnosis based on

• Fasting glucose 6.1-6.9 mmol/L (110-125 mg/dL)

• 2-hour OGTT 7.8-11.1 mmol/L (140-199 mg/dL)

1-5% per year develops DM

50-80% reverts to normal glucose tolerance

Weight loss may improve glucose tolerance

Associated with progressively greater risk of developing macrovascular complications

Complications of diabetes

The majority of complications involve the vascular system

Aggravating factors: poor glycemic control, inadequate control of hypertension and cholesterol, smoking, high fat diet

Macroangiopathy

accelerated atherosclerosis leading to coronary artery disease (CAD), stroke, pulmonary vascular disease (PVD) most common cause of death in type 2 DM

Microangiopathy             

_ Major chronic complication of type 1 and type 2 DM

_ Path gnomonic lesion is basement membrane thickening

_ Classically causes retinopathy, nephropathy and neuropathy

_ Can involve many other organs, including heart and skin

1. Retinopathy

Epidemiology

• Present in 50% of patients after 10 years with DM

• One of the leading causes of blindness in North America

Types

• Non-proliferative (background)

• Generally no symptoms but may affect macula and impair vision

• Microaneurysms, hard exudates, dot and blot hemorrhages

• Pre-proliferative

• 10-40% progress to proliferative within one year

• Macular edema, venous shunts and beading, nerve fiber layer micro infarcts (cotton wool spots)

Proliferative

• Great risk for loss of vision

• neovascularization, fibrous scarring, vitreal detachment, retinal detachment

Presentation

• Asymptomatic to complete loss of vision

Prevention and management

• Tight glycemic control

• Photocoagulation (eliminates neovascularization)

• vitrectomy

• Frequent follow-up visits with an ophthalmologist (immediate referral after diagnosis of type 2 DM; in type 1, only after 5 years of DM

2. Nephropathy

Epidemiology

• Diabetes-induced renal failure is the most common cause of renal failure in North America

• 20-40% of persons with type 1 DM (after 5-10 years) and 4-20% with type 2 DM have progressive nephropathy

Presentation

• Initial changes include microalbuminuria, increased glomerular filtration rate (GFR) (up to 140%), enlarged kidneys

• Over 15 years, progresses to cause hypertension, persistent proteinuria (macroalbuminuria), nephrotic syndrome, renal failure

Prevention and management

• Tight glucose control

• Tight blood pressure control – ACE inhibitors (Shown to reduce nephropathic complications) and calcium channel blockers (CCB)

• limit use of nephrotoxic drugs and dyes

• Protein restriction (controversial)

3. Neuropathy

Epidemiology

• Common in both type 1 and type 2 DM

Pathophysiology

• Metabolic defect thought to be due to increased sorbitol and/or decreased myoinositol (exact mechanisms not understood)

Types

• Distal symmetric “glove and stocking” polyneuropathy

• Autonomic dysfunction (e.g. gastroparesis)

• Mononeuropathy (e.g. carpal tunnel syndrome)

Presentation

• Paresthesias or neuropathic pain

• Motor or sensory deficits (including cranial nerves)

• Orthostatic hypotension

• Impotence

• voiding difficulties

• Foot ulcers

Prevention and management

• Tight glucose control

• Anti-depressants (e.g. amitriptyline), capsaicin, and anti-epileptics (e.g. Tegretol, Neurontin) for painful neuropathic syndromes

• Erythromycin and domperidone for gastroparesis

• foot care education

4. Other Complications

·         Skin disease

·         Bone and joint disease

·         Cataracts

Treatment of diabetes

Diabetes Control and Complications Trial (DCCT) (1993) demonstrated a 50-70% decrease in microvascular complications in type 1 DM in an intensively treated group as compared to a conventionally treated group

United Kingdom Prospective Diabetes Study (1998) demonstrated a

• Decrease in diabetes complications in intensively treated group compared to conventionally treated group

• marked decrease in vascular complications in those with

Well-controlled blood pressure

Diet

·         Energy intake to achieve and maintain desirable weight

·         Other recommendations as per Canada's Food Guide

Lifestyle

Regular physical exercise can improve insulin sensitivity and lower lipid concentrations and blood pressure

stop smoking and decrease alcohol consumption

Oral Hypoglycemic Agents

Mainly for type 2 DM

Clinical Pearl

·         Sulfonyureas and Meglitimides “squeeze” endogenous insulin from the pancreas.

·         Biguanides and Thiazolidinediones act primarily in peripheral tissues remote from the pancreas.

Insulin (see Table)

Doses adjusted for individual patient needs to meet target glycemic control

Administration

• Subcutaneous injections

• Continuous subcutaneous insulin infusion pump

• IV infusion (regular insulin only)

Preparations

• Ultra-rapid (Humalog)

• Rapid or regular (R or Toronto)

• Intermediate (N or NPH, L or Lente)

• Long-acting (U or Ultralente)

_ Multiple daily injections of different types of insulin usually necessary for optimal glucose control

_ Estimate of total daily insulin requirement when starting an adult type 1 diabetes patient on insulin = 0.5 - 0.6 units/kg

 Glucose Monitoring

_ Frequent self-monitoring and recording of blood glucose is now standard management

_ Hemoglobin A1c (HbA1c or glycosylated hemoglobin)

• Percentage indicates level of plasma glucose over past 3 months

• Extremely useful for monitoring patient’s long-term diabetes control

• Goal is to maintain HbA1c within 5-8% range (i.e. average blood glucose 5.0-11.0 mmol/L)

• HbA1c ε 10% indicates poor control

Variable Insulin Dose Schedule (“Sliding Scale”)

_ Patient takes fixed doses of intermediate-acting insulin (N) but varies doses of fast-acting insulin (R or H) based on blood glucose reading at time of dose

_ Use baseline R or H dose when in blood glucose target range; add or subtract units when above or below target

_ allows patient to make corrections to avoid long periods of hyper- or hypoglycemia

Insulin Pump Therapy

_ External, battery-operated pump continuously delivers basal dose of fast-acting insulin through small subcutaneous catheter

_ At meals, patient programs pump to deliver extra insulin bolus

_ Basal dose may be increased or decreased based on activity, sleep, etc.

_ Advantages: more flexible lifestyle (sleep in, eat / skip meals when desired), better glucose control

_ Disadvantages: very expensive, increased risk of DKA if pump inadvertently disconnected, frequent blood glucose testing required