Transcript Chapter 8 Vital Signs

Chapter 8 Vital Signs
Section Ⅳ Blood Pressure
Section Ⅳ Blood Pressure

Physiology of Blood Pressure

Factors Affecting Blood Pressure

Abnormal Blood Pressure

Nursing process and blood pressure
determination
Physiology of Blood Pressure

Blood pressure is the lateral pressure on the walls of
an artery by the flowing blood under pressure from
the heart．

Generally, it refers to arterial pressure, especially the
blood pressure of humeral artery unless giving clear
indication.
Physiology of Blood Pressure

Forming of blood pressure

The heart generates pressure during the cardiac cycle
to perfuse the organs of the body with blood.

The cardiovascular system is a hermetic tract system.

Blood flows from the heart to the arteries, into the
capillaries and veins, and then back to the heart.
Physiology of Blood Pressure

Forming of blood pressure

Blood flows throughout the circulatory system
because of pressure changes．
Blood moves from an area of high pressure to an area
of low pressure．
In this system, to the forming of blood pressure
precondition: an adequate blood volume
essential factors: heart’s contraction
peripheral resistance
elasticity of vessel walls


Physiology of Blood Pressure

concepts

The peak of maximum pressure when ejection occurs is
the systolic blood pressure.

When the ventricles relax, the blood remaining in the
arteries exerts a minimum or diastolic blood pressure．

The difference between systolic and diastolic pressure is
the pulse pressure．

The standard unit for measuring blood pressure is
millimeters of mercury (mmHg).
Physiology of Blood Pressure

Bp is a good indicator of cardiovascular health．

Blood pressure reflects the interrelationship
among
cardiac output
peripheral vascular resistance
blood volume
blood viscosity
artery elasticity
Cardiac Output


A person’s cardiac output is the volume of blood pumped
by the heart (stroke volume) during 1 minute (heart rate).
Bp depends on the cardiac output and peripheral
vascular resistance.
cardiac output increase
greater heart muscle contractility,
an increase in heart rate
an increase in blood volume
more blood is pumped against arterial walls
Bp rise
Peripheral Resistance

Arteries and arterioles are surrounded by smooth
muscle.

Resistance to blood flow determined by the tone of
vascular musculature and diameter of blood vessels

The smaller the lumen of a vessel，the greater
peripheral vascular resistance to blood flow．

As resistance rises，arterial blood pressure rises．
Blood Volume

Most adults have a circulating blood volume of
about 5000 ml．

Normally the blood volume remains constant．

circulating blood volume increases
more pressure is exerted against arterial walls
Bp rise
Blood Viscosity

The thickness or viscosity of blood affects the ease
with which blood flows through small vessels.

The hematocrit，or percentage of red blood cells
in the blood，determines blood viscosity.

When the hematocrit rises and blood flow slows，
arterial blood pressure increases．The heart must
contract more forcefully to move the viscous blood
through the circulatory system.
Elasticity of Vessel Walls

Normally the walls of an artery are elastic and easily
distensible．

Arterial distensibility prevents wide fluctuations in blood
pressure．

With a reduced elasticity there is greater resistance to
blood flow，and the systemic pressure rises．

Systolic pressure is more significantly elevated than
diastolic pressure as a result of reduced arterial
elasticity．
Factors Affecting Blood Pressure

Age: Blood pressure tends to rise with advancing age.
Average Blood Pressure At Various Ages
Age
Arterial pressure (mmHg)
Newborn (1 month)
1 year
6 years
84/54
95／65
105／65
10~13 years
110／65
14~17 years
120／75
Middle adult
Older adult
120／80
140~160／80~90
Factors Affecting Blood Pressure

Gender
no clinically significant difference between boys and
girls before puberty; adult males have higher readings
than females about 5mmHg; menopause women tend to
have higher levels of Bp, become no significant
difference between men

Stress
Anxiety
heart rate
fear
peripheral resistance
pain
if stress is not relieved
Bp

Exercise
cardiac output
Bp
Bp
Factors Affecting Blood Pressure

Diurnal Variations:
a lower Bp in the morning
rising throughout the day
peaking in late afternoon or evening
lowering at night

Medications: Antihypertensive medications

Position: Standing >sitting > Lying down
Somatotype: the tall and the obese have higher Bp
Temperature: cold vessels constrict Bp


Bp
Factors Affecting Blood Pressure

Sites:

systolic pressure is 10~20mmHg higher in right arm
than that in left arm ;
> 20mmHg between both arms

varied arteritis
congenital artery
malformation
thromboangiitis
systolic pressure is 20~40mmHg higher in lower
limbs than in arms, but the diastolic pressure is the
same. (except arteriostenosis or arterial obstruction)
Abnormal Blood Pressure

Hypertension

Hypotension
Hypertension
Definition and Classification of Blood Pressure (WHO/ISH)
Category
Optimal
Normal
Systolic
(mmHg)
<120
<130
Diastolic
(mmHg)
<80
<85
High normal
130~139
85~89
Hypertension：
Stage 1 (Mild)
Stage 2 (Moderate)
Stage 3 (Severe)
Systolic hypertension
140~159
160~179
≥180
≥140
90~99
100~109
≥110
<90
Hypertension

Hypertension is associated with the thickening and
loss of elasticity in the arterial walls．


Persons with a family history of hypertension are at
significant risk．
Risk factors: obesity;
cigarette smoking;
heavy alcohol consumption;
high blood cholesterol 1evels
continued exposure to stress
high salt diet
Hypotension

be generally considered when the systolic blood pressure falls to
90mmHg or below

can be caused by bleeding, shock, severe burn, prolonged,
diarrhea and vomiting.

Orthostatic hypotension refers to the low blood pressure when the
patient changes from lying position to standing position. It is
usually the result of peripheral vasodilatation in which the blood
flow increases and the blood flowing to main body organs
decreases, especially the brain, often causing the person to feel
fainted.
Nursing process and
blood pressure determination

Assessment

Measurement

to evaluate the general state of cardiovascular health
VCD
and its response to other system imbalances

the patient’s usual condition, such as age, sex, the state
of illness and treatment, and whether the patients have
hemiplegia and dysfunctions or other complications
Nursing Diagnosis

Hypotension, hypertension，and narrow or wide
pulse pressures are defining characteristics of many
nursing diagnoses and are considered along with other
assessment data．

Related nursing diagnoses include activity intolerance,
anxiety, cardiac output decreasing, and fluid volume
deficit.
Nursing Plan
including

appropriate interventions based on the nursing
diagnosis identified and the related factors

the patient’s understanding on the purpose of
taking blood pressure

cooperating with nursing and treatment
Implementation
 Keep surroundings quiet and the temperature
appropriate.

Have light and digestible, low fat and low cholesterol,
high vitamins and high cellulose diet. Limit salt intake
according to the patient’s blood pressure level.

Form the habit of regular life. Have enough sleeping,
stop smoking and drinking, maintain bowels smooth.
Implementation

Keep stable feeling and decrease factors affecting
emotion.

Exercise appropriately.

Closely monitor the patients’ blood pressure and
condition. Instruct patients to take medicine on time
and observe reactions of medicine.

Health instruction: teach the patients and family
members to take blood pressure and observe the
complications of hypertension and basic first-aid skills.
Evaluation

evaluate the patients’ outcomes by assessing
the blood pressure following each intervention;

evaluate patients’ mental state and
cooperation with treatment and nursing;

evaluate patients’ knowledge about health.
SECTION Ⅴ RESPIRATION

Physiology of Respiration

Abnormal Respiration

Nursing Process and Respiratory
Determination

Nursing Skills Improving
the Functions of Respiration
Physiology of Respiration

Basic Conceptions

Respiration Process

Control of respiration

Normal respiration

Factors influencing character of respirations
Basic Conceptions

Respiration is the mechanism the body uses to
exchange gases between the atmosphere and the
blood and the cells．

External respiration refers to the exchange of oxygen
and carbon dioxide between the alveoli of lung and
the pulmonary blood.

Internal respiration refers to the exchange of oxygen
and carbon dioxide between the circulating blood
and the cells of the body tissues.
Basic Conceptions

Inspiration refers to the intake of air into the lungs.

Expiration refers to breathing out or the movement
of gases from the lungs to the atmosphere.

Ventilation is also used to refer to the movement of
air in and out of the lungs.

There are two basic types of breathing: thoracic
breathing and diaphragmatic breathing
Respiration Process
Control of respiration

Respiratory center

Reflex mechanisms

Chemoreceptors Control
Respiratory center





be composed of several clusters of neurons in central
nervous system
stimulate and regulate respiration
be distributed over the cerebral cortex of the brain,
diencephalons, pons, medulla, and spinal cord
Pons and medulla oblongata control normal
respiratory rhythm.
Higher centers above midbrain lie in cerebral ganglion
and the cerebral cortex of the brain.
The cerebral cortex of the brain voluntarily controls
ventilation and regulates activity of brain stem center.
Reflex mechanisms

Hering-Breure reflex
(pulmonary stretch reflex)

Proprioceptor reflex

Defense reflex: filtration of air,
mucociliary clearance system,
cough reflex,
sneeze reflex,
reflex bronchoconstriction,
alveolar macrophages
Hering-Breure reflex

As the lungs inflate, pulmonary stretch receptors
activate the inspiratory center to inhibit further lung
expansion, while as lungs deflate, expiration is
inhibited and inspiration is stimulated. This is called
Hering-Breure reflex.

Hering-Breure reflex helps to maintain normal
respiration rhythm.
Proprioceptor reflex

Proprioceptors are present in the chest wall and
diaphragm and provide information about thoracic
inflation.

Proprioceptors provide feedback and introduce
impulse to maintain normal respiration, which enables
the strength of the contraction to be varied if the
airway resistance increases.
Chemoreceptors Control

Respiration is controlled by the level of carbon
dioxide (C02), oxygen (O2), and the concentration of
hydrogen ion ( [H+] ) in the arterial blood.

Central chemoreceptors are located in the medulla
and respond to changes in [H+]. An increase in [H+]
(acidosis) causes the medulla to increase the
respiratory rate and depth. The most important
factor in the control of ventilation is the level of C02 in
the arterial blood．
Chemoreceptors Control

Peripheral chemoreceptors are located in the carotid
bodies at the bifurcation of the common carotid
arteries and in the aortic bodies above and below the
aortic arch.

The peripheral chemoreceptors respond to decrease in
PaO2 and pH and to increase in PaCO2. These changes
also cause stimulation of the respiratory center.
Chemoreceptors Control

In a healthy person an increase in PaCO2 or
decrease in pH causes an immediate increase
in the respiratory rate.
The PaCO2 does not
vary more than about 3mmHg if lung function is
normal.
Chemoreceptors Control

Conditions such as chronic obstructive pulmonary
disease (COPD) alter lung function and may result in
chronically elevated PaCO2 levels. ---adapting

The chemoreceptors in the carotid artery and aorta of
these patients are sensitive to hypoxemia，or low levels
of arterial O2.

If PaO2 1evels fall， these receptors signal the brain to
increase the rate and depth of ventilation．

Hypoxemia helps to control ventilation in patients with
chronic lung disease．
Normal respiration

The nurse assesses ventilation by determining the rate，
depth，and rhythm of breathing．

Adults normally breathe in a smooth，uninterrupted
pattern of 12 to 20 breaths per minute under a quiet
state.

Generally thoracic breathing is seen in female, while
diaphragmatic breathing is more in male and children.
Factors influencing character
of respirations

Age
The respiratory rate
varies with age.
The younger the age,
the more rapid the
respiratory rate is.
Age
Newborn
Infant (6 month )
Toddler (2 years )
Child
Adolescent
Adult
Rate
30~60
30~50
25~32
20~30
16~19
12~20

Sex:
Female’s R is more rapid than male’s for the same age.

Exercise: increase R rate and depth to meet the body’s
need for additional oxygen

Emotion:
fear
strong emotions anger
nervousness
stimulate R center
pause
or rate
Anxiety
stimulate sympathetic
rate and depth

Smoking:
Chronic smoking

lung’s airways
rate
Pain:
acute pain
stimulate sympathetic rate and depth
inhibit or splint chest wall movement when pain is in
area of chest or abdomen.

Medications:
Narcotic, analgesics ,sedatives rate and depth.
Amphetamines , cocaine rate and depth.

Brain stem injury:
impairs the R center
inhibits rate and rhythm
Mechanics of Breathing

Inspiration is an active process．

respiratory center sends impulse along the phrenic nerve,
causing the diaphragm contracts
Abdominal organs move downward and forward to move
air into the 1ungs．
During a normal relaxed breath a person inhales 500 m1
of air．This amount is referred to as the tidal volume．



Expiration is a passive process．

the diaphragm relaxes and the abdominal organs return to
their original positions．
The lung and chest wall return to a relaxed position．

Abnormal Respiration

Respiratory Rate

Respiratory Depth

Respiratory Rhythm

Respiratory Nature

Respiratory Sound
Respiratory Rate
The respiratory rate is the number of respiration in
breaths per minute. Breathing that is normal in rate
and depth is called eupnea.

Tachypnea. Rate of breathing is regular but
abnormally rapid (greater than 24 breaths per
minute)．Common causes are fever, pain, over
fatigue, and hyperthyroidism.

Bradypnea. Rate of breathing is regular but
abnormally slow ( less than 12 breaths per minute)．
It can be seen with anesthetics or sedatives overdose,
and brain tumor with intracranial pressure increase.
Respiratory Depth

Deep breathing (Kussmaul’s respiration).

abnormally deep but regular

[H+]
stimulates respiratory receptors
produce hyperventilation

acidosis, diabetes ketoacidosis and uremia acidosis

Shallow breathing.

refers to the exchange of a small volume of air and the
lungs inflate and deflate to the minimal extent

be seen with respiratory muscle paralysis, chest or lung
diseases and shock
Respiratory Rhythm

Cheyne-Stokes Respiration.

Biots Breathing.

Nodding Breathing.

Sigh Breathing.
Cheyne-Stokes Respiration

Respiratory cycle begins with slow, shallow breaths
that gradually increase to abnormal rate and
depth．Then the pattern reverses，breathing slows
and becomes shallow, climaxing in periods of apnea
for about several seconds (5 to 20 seconds) before
respiration resumes．It’s a cycle in which respiration
gradually wax and wane in a regular pattern with
alternating periods of breathing and apnea.
Cheyne-Stokes Respiration

The mechanism is the depression of respiratory center
or severe hypoxia, causing the increase of PaCO2 to
some extent, which result in hyperventilation. When
the accumulated carbon dioxide is blown off, the
decreased level of it can’t stimulate chemoreceptors
and causes apnea. As its level increases again, the
shallow and slow breathing then increase in rate and
depth again, alternating the cycle.

It often occurs with congestive heart failure, increased
intracranial pressure, brain injury and uremia.
Biots Breathing

is a cycle pattern in which a series of normal breaths
followed by a short, irregular period of apnea．

mechanism is similar to Cheyne-Stokes respiration.

often occurs before the breathing completely stops,
with worse prognosis.

common causes are head trauma and heart stroke.
Nodding Breathing

It is a breathing pattern in which the
sternocleidomastoid muscles are involved.
The patient’s head moves upward and
downward with breathing.

It often indicates respiratory failure.
Sigh Breathing

It is a prolonged deeper breathing with sigh sound
followed by a short period of interval.

Occasional sigh breathing is normal.

It is commonly seen with emotional dysfunction,
such as nervousness and neurosis.

Repeated and frequent sigh breathing often
indicates the approaching of death.
Respiratory Nature

Dyspnea.
a difficult, labored, or painful breathing ; usually involves the
accessory muscles of respiration visible in the neck.

Inspiratory Dyspnea.
partial upper respiratory tracts be obstructed,
supclavicular, suprasternal and intercostal retractions
causes are laryngeal edema or foreign bodies in trachea

Expiratory Dysnea.
partial lower respiratory tracts be obstructed
often be seen with obstructive pulmonary diseases

Mixed Dysnea.
Respiratory Sound


Snoring Respiration.
a deep breath pattern with snoring

accumulated secretions in trachea and bronchus

mostly be seen with coma or neurologic diseases

Stridulant Respiration.
 Harsh and high-pitched inspiratory sound can be heard

upper respiratory tracts obstruction(larynx ,trachea);
infants or children with laryngitis.
Nursing Process and
Respiratory Determination

Assessment

Nursing Diagnosis

Nursing Plan

Implementation

Evaluation
Assessment

estimate the time interval after each respiratory cycle

assess R rate，pattern，and depth, rhythm

assess for risk factors, symptoms and signs of R
alterations

assess other information, such as age, the status of an
illness and treatment

whether suffering from cough, expectoration,
hemoptysis, cyanosis, dyspnea, or chest pain
Nursing Diagnosis

activity intolerance

ineffective breathing


gas exchange impairment
ineffective airway clearance, and so on.
Nursing Plan
includes

interventions based on the nursing diagnosis
identified and the related factor

understand the purpose of taking respiration
measurement

cooperate with nursing care and treatment
Implementation

Provide a comfortable environment. Instruct the
patient to have appropriate rest.

Closely observe changes of the patient’s condition.
Instruct patient to take medicine on time and observe
reactions of the medicine.

Maintain adequate hydration and nutrition.

Oxygen inhalation and sputum suction are provided
according to the patient’s condition. Monitor
respiration, collect sputum specimen as needed.

Give mental and social support.

Health instruction: stop smoking and drinking, form
the habit of regular life. Teach the patients and family
members basic first-aid skills.
Evaluation

The nurse evaluates nursing outcomes by assessing
the respiratory rate, depth, rhythm each
intervention.

Evaluates the patient’s mental status, degree of
cooperation with treatment and understanding
about health knowledge.
Nursing Skills Improving
the Functions of Respiration

Methods to clean out secretions of airway

Deep breathing and effective coughing

Chest Percussion

Postural drainage

Suctioning

Oxygenic Therapy
Deep breathing and effective
coughing

With patient sitting upright, instruct patient to
breathe in slowly through nose to expand chest and
abdomen, and to hold sustained inspiration for 3 to 5
seconds, then exhale slowly through mouth.

After several deep breathe, instruct patient to inhale
deeply, hold breath for several seconds, lean forward,
and cough rapidly through an open mouth, using
abdominal, thigh, and buttock muscles.



Instruct patient with pulmonary condition to exhale
through pursed lips and to cough throughout
exhalation in several short bursts.
Instruct patient with abdominal incision to cross arms
over pillows as abdominal muscles contract during
cough.
Instruct patient to use manual pressure on wound, or
support incision with palms of your hands.

Assess patient regularly and provide positive
reinforcement. Encourage patient to repeat deep
breathing exercises several times hourly.
Chest Percussion

Cup hands with thumbs and fingers closed. Keep wrists
loosen and relaxed and rhythmically flex and extend
wrists to clap over area.

This motion produces vibrations that loosen secretions
for easier removal with postural drainage and coughing.

Use percussion for 30 to 60 seconds over an area several
times a day, but up to 3 to 5 minutes for the patient with
slimy secretions.

Do not percuss over bony prominences,such as
vertebral column or scapula.
Postural drainage

use positioning techniques to draw secretions from
specific segments of the lungs and bronchi into the
trachea. Coughing or suctioning normally removes
secretions from the trachea.

its use depends on assessment findings.

Have patient remain in each position for 15 min for
pulmonary toilet (5 min in position; 5 min for
percussion, vibration, and coughing; 5 min for
bronchial drainage.)
Postural drainage

to evaluate the patient’s tolerance during postural
drainage: assess the patient’s pulse, respiratory rates,
pallor, diaphoresis, dyspnea, and fatigue

Postural drainage should carry out 2 to 4 times a day
for 15 to 20 minutes unless the patient feel weak or
faint.
Suctioning

Suctioning is a method to remove airway secretions
through oral cavity, nasopharyngeal cavity or artificial
airway to clear respiratory airway and to prevent
complications, such as pneumonia, atelectasis and
choke.

Any patient (e.g. elder with weakness, critical, coma,
anaesthetic patients) is unable to remove secretions
with effective coughing must use suctioning.
VCD
Suctioning

Purposes
1. To maintain airway smooth and prevent
airway obstructions.
2. To promote respiratory function
3. To prevent pneumonia that may results from
accumulated secretions.

Equipment
Portable or wall suction unit with connecting tubing
Sterile water or normal saline
Sterile gloves
Sterile basin
Two pitchers with caps:sterile normal saline
sterile catheters in sterile container
Sterile gauzes
Clean drape or towel
Gag, tongue depressor, and tongue forceps if necessary

Procedures
1. Assess for signs and symptoms indicating presence of
upper airway secretions
2. Explain to patient
3. Properly position patient
4. Place towel on pillow or under patient’s chin
5. Turn suction device on and set vacuum regulator to
appropriate negative pressure ( Adults: 40.0-53.3kPa;
Children< 40.0kPa).
wear gloves

Procedures
6. Connect connecting tubing to suction machine and
catheter
Check equipment is functioning properly by suctioning
small amount of normal saline from pitcher.
Coat distal 6-8cm of catheter with normal saline.
7. Suction
Oral suctioning
10 -15cm
Pharyngeal suctioning (tip of nose - base of ear lobe )
Tracheal suctioning 20-24 cm
Artificial airway suction (until resistance is met )

Procedures
8. Disconnect catheter from connecting tubing; discard
into appropriate receptacle. Pull gloves off. Turn off
suction device.
9. Wash hands.
10. Prepare equipment for next suctioning.
11. Observe patient for absence of airway secretions,
restlessness, oral secretions.
12. Record the amount, consistency, color, and odor of
secretions and patient’s response to procedure;
document patient’s presuctioning and postsuctioning
respiratory status.
Oxygenic Therapy

The goal of oxygenic therapy is to prevent or relieve
hypoxia.

Oxygen is considered a drug that requires a
physician’s prescription for administration.

The nurse must know the indication, dosage, route of
administration, and potential complications of its use.

Classification of Hypoxia
Classification
Hypotonic hypoxia
Characteristics
Decreased level of PaO2 and
CaO2 in arterial blood
Causes
high altitude disease,
COPD, or congenital
heart diseases
Circulatory hypoxia Poor tissue perfusion
with oxygenated blood
shock, heart failure,
and so on
Hemic hypoxia
anemia, carbon
monoxide poisoning, or
methemoglobinemia
Inadequate or
alterations of quality of
hemoglobin lead to
hemic hypoxia
Histogenous hypoxia The inability of tissues
to extract oxygen from
blood
cyanide poisoning

Level of Hypoxia
Mild Hypoxemia: PaO2>6.67kPa (50 mmHg), SaO2 >80%, no
cyanotic. In general, oxygen therapy is not indicated for patients
in this level of hypoxemia. patients who complain dyspnea may
receive low flow oxygen therapy (1-2 L/min).
Moderate Hypoxemia: PaO2 4-6.67kPa (30-50mmHg), SaO2 6080%. patients have dyspnea or cyanotic. patients need middle
flow oxygen therapy (2-4 L/min).
Severe Hypoxemia: PaO2 < 4kPa (30 mmHg), SaO2<60%.
patients have severe dyspnea or may have severe cyanotic. It is
absolute indication for oxygen therapy. patients need high flow
oxygen therapy (4-6L/min).

Complications of Oxygen therapy and
Prevention
Prolonged administration ( >24h) of high concentration
( >60%) of oxygen can result in some complications,
mostly be seen include
Oxygen Toxicity
Absorption Atelectasis
Dryness of Respiratory Secretions
Retrolental Fibroplasia
Respiration Depression
Oxygen Toxicity

Prolonged administration of high concentration of
oxygen leads to lung substantive changes

Manifestations : uncomfortable, pain, and burning
sensation under sternum in early stage of oxygen
toxicity, then have increased respiratory rate, nausea,
vomiting, restlessness, and dry cough.
Oxygen Toxicity

Methods for preventing oxygen toxicity :

avoiding prolonged administration of high
concentration of oxygen

measuring oxygen concentration and saturation of
arterial blood regularly

observing effects and side effects of oxygen therapy
Absorption Atelectasis

When patients inspire oxygen of high concentration, in
alveoli most of nitrogen gas that is not absorbable, is
replaced by oxygen. Once bronchia are obstructed by
secretions, oxygen in alveoli is absorbed rapidly and
absorption atelectasis occurs.
Absorption Atelectasis

Manifestations : restlessness, increased respiration
rate and heart rate, raised blood pressure, dyspnea,
and even coma.

Prevention of obstruction in respiratory tract is
essential for preventing absorption atelectasis.
patients should be encouraged often to make deep
breath and effective cough, and change body
position more often to prevent stasis of secretions.
Dryness of Respiratory Secretions

Oxygen from cylinder system or wall-outlet system is
dry. Dry gases dehydrate the respiratory mucous
membranes and secretions become thick and viscous
which is hard to remove.

Humidification should be strengthened while
delivering oxygen to prevent dehydration of
respiratory mucous membrane and dryness of
respiratory secretions.
Retrolental Fibroplasia

High arterial oxygen tensions are a major factor in
causing retrolental fibroplasias in neonates, especially
in preterm newborns, which may result in irreversible
blindness.

The condition is caused by blood vessels growing into
vitreous, which is followed later by fibrosis.

Oxygen therapy for neonates should control
concentration of oxygen and time of therapy.
Respiration Depression

It occurs among patients with type Ⅱ respiratory
failure who have decreased PaO2 and increased PaCO2.

prolonged high level of PaCO2 in arterial blood
respiratory center in the medulla is not sensitive
to concentration of CO2 and regulation of respiration
mainly depends on the stimulation to peripheral
chemoreceptors of decreased O2.
Respiration Depression

When patients inspire oxygen of high concentration,
this stimulation is eliminated leading to depression of
respiration and even respiration cease.

Oxygen therapy of low concentration and low flow
rate should be administered for patients with type Ⅱ
respiratory failure to maintain patients’ PaO2 at 8kPa