Gas Exchange, Impaired - Ventilation or Perfusion
Sue Galanes, RN, MS, CCRN
NANDA: The state in which the individual experiences a decreased
passage of oxygen and/or carbon dioxide between the alveoli of the lungs and
the vascular system
By the process of diffusion the exchange of oxygen and carbon
dioxide occurs in the alveolar-capillary membrane area. The relationship
between ventilation (airflow) and perfusion (blood flow) affects the efficiency
of the gas exchange. Normally there is a balance between ventilation and
perfusion. However, certain conditions can offset this balance, resulting in
impaired gas exchange. Altered blood flow from a pulmonary embolus or decreased
cardiac output or shock can cause ventilation without perfusion. Conditions
that cause changes or collapse of the alveoli impair ventilation, such as
atelectasis, pneumonia, pulmonary edema, and adult respiratory distress
syndrome (ARDS). Other factors affecting gas exchange include high altitudes,
hypoventilation, and altered oxygen carrying capacity of the blood from reduced
hemoglobin. Elderly patients have a decrease in pulmonary blood flow and
diffusion as well as reduced ventilation in the dependent regions of the lung
where perfusion is greatest. Chronic conditions such as chronic obstructive
pulmonary disease (COPD) put these patients at greater risk for hypoxia. Other
patients at risk for impaired gas exchange include those with a history of
smoking or pulmonary problems, obesity, prolonged periods of immobility, and
chest or upper abdominal incisions.
- Altered O2 supply
- Alveolar-capillary membrane changes
- Altered blood flow
- Altered oxygen-carrying capacity of blood
- Inability to move secretions
Patient maintains optimal gas exchange as evidenced by normal
ABGs and alert responsive mentation or no further reduction in mental
- (i) independent
- (i) Assess respirations: note quality, rate,
pattern, depth, and breathing effort.
- Both rapid, shallow breathing patterns and hypoventilation
affect gas exchange. Shallow, "sighless" breathing patterns postsurgery (as a
result of effect of anesthesia, pain, and immobility) reduce lung volume and
- (i) Assess lung sounds, noting areas of
decreased ventilation and the presence of adventitious sounds.
- (i) Assess for signs and symptoms of
hypoxemia: tachycardia, restlessness, diaphoresis, headache, lethargy, and
- (i) Assess for signs and symptoms of
atelectasis: diminished chest excursion, limited diaphragm excursion, bronchial
or tubular breath sounds, rales, tracheal shift to affected side.
- Collapse of alveoli increases physiological
- (i) Assess for signs or symptoms of pulmonary
infarction: cough, hemoptysis, pleuritic pain, consolidation, pleural effusion,
bronchial breathing, pleural friction rub, fever.
- (i) Monitor vital signs.
- With initial hypoxia and hypercapnia, blood pressure (BP),
heart rate, and respiratory rate all rise. As the hypoxia and/or hypercapnia
becomes more severe, BP may drop, heart rate tends to continue to be rapid with
arrhythmias, and respiratory failure may ensue with the patient unable to
maintain the rapid respiratory rate.
- (i) Assess for changes in orientation and
- Restlessness is an early sign of hypoxia. Chronic hypoxemia
may result in cognitive changes, such as memory changes.
- (c) Monitor arterial blood gases (ABGs) and
- Increasing PaCO2 and decreasing PaO2 are signs of respiratory failure. As the
patient begins to fail, the respiratory rate will decrease and PaCO2 will begin to rise. Some
patients, such as those with COPD, have a significant decrease in pulmonary
reserves, and any physiological stress may result in acute respiratory
- (c) Use pulse oximetry to monitor O2 saturation and pulse rate
- Pulse oximetry is a useful tool to detect changes in
oxygenation. O2 saturation
should be maintained at 90% or greater. This tool can be especially helpful in
the outpatient or rehabilitation setting where patients at risk for
desaturation from chronic pulmonary diseases can monitor the effects of
exercise or activity on their oxygen saturation levels. Home oxygen therapy can
then be prescribed as indicated. Patients should be assessed for the need for
oxygen both at rest and with activity. A higher liter flow of oxygen is
generally required for activity versus rest (e.g., 2 L at rest, and 4 L with
activity). Medicare guidelines for reimbursement for home oxygen require a
PaO2 <58 and/or oxygen
saturation88% on room air. Oxygen delivery is
then titrated to maintain an O2 saturation of 90% or greater.
- (i) Assess skin color for development of
- For cyanosis to be present, 5 gm of hemoglobin must
- (c) Monitor chest x-ray reports.
- Chest x-rays may guide the etiologic factors of the
impaired gas exchange. Keep in mind that radiographic studies of lung water lag
behind clinical presentation by 24 hours.
- (i) Monitor effects of position changes on
oxygenation (SaO2, ABGs,
SvO2, and end tidal CO2).
- Putting the most congested lung areas in the dependent
position (where perfusion is greatest) potentiates ventilation and perfusion
- (i) Assess patient's ability to cough
effectively to clear secretions. Note quantity, color, and consistency of
- Retained secretions impair gas exchange.
- (i) independent
- (c) Maintain oxygen administration device as
ordered, attempting to maintain O2 saturation at 90% or greater.
- To provide for adequate oxygenation.
- Avoid high concentration of O2 in patients with COPD.
- NOTE: If the patient is
allowed to eat, O2 still must
be given to the patient but in a different manner (e.g., changing from mask to
a nasal cannula).
- Hypoxia stimulates the drive to breathe in the chronic
CO2 retainer patient. When
applying oxygen, close monitoring is imperative to prevent unsafe increases in
the patient's PaO2, which
could result in apnea.
Eating is an activity and more O2 will be consumed than when the patient is at
rest. Immediately after the meal, the original oxygen delivery system should be
- (c) For patients who should be ambulatory,
provide extension tubing or portable oxygen apparatus
- To promote activity, facilitate more effective ventilation,
and optimize clearance of secretions.
- (i) Position with proper body alignment for
optimal respiratory excursion (if tolerated, head of bed at 45 degrees).
- This promotes lung expansion and improves air
- (i) Routinely check the patient's position so
he or she does not slide down in bed.
- This would cause the abdomen to compress the diaphragm,
which would cause respiratory embarrassment.
- (i) Position patient to facilitate
ventilation/perfusion matching. Use upright, high Fowler's position whenever
- High-Fowler's position allows for optimal diaphragm
excursion. When patient is positioned on side, the good side should be down
(e.g., lung with pulmonary embolus or atelectasis should be up).
- (i) Pace activities and schedule rest periods
to prevent fatigue.
- Even simple activities (such as bathing) during bed rest
can cause fatigue and increase oxygen consumption.
- (i) Change patient's position every 2
- This facilitates secretion movement and drainage.
- (i) Suction as needed.
- To clear secretions if the patient is unable to effectively
clear the airway.
- (i) Encourage deep breathing, using incentive
spirometer as indicated.
- To reduce alveolar collapse.
- (i) For postoperative patients, assist with
splinting the chest.
- To optimize deep breathing and coughing efforts.
- (i) Encourage or assist with ambulation as
- To promote lung expansion, facilitate secretion clearance,
and stimulate deep breathing.
- (i) Provide reassurance and allay anxiety:
- Have an agreed-on method for the patient to call for assistance
(e.g., call light, bell).
- Stay with the patient during episodes of respiratory
- (i) Anticipate need for intubation and
mechanical ventilation if patient is unable to maintain adequate gas
- Early intubation and mechanical ventilation are recommended
to prevent full decompensation of the patient. Mechanical ventilation provides
supportive care to maintain adequate oxygenation and ventilation to the
patient. Treatment also needs to focus on the underlying causal factor leading
to respiratory failure.
- (c) Administer medications as prescribed.
- The type depends on the etiologic factors of the problem
(e.g., antibiotics for pneumonia, bronchodilators for COPD,
anticoagulants/thrombolytics for pulmonary embolus, analgesics for thoracic
Education/Continuity of Care
- (i) independent
- (i) Explain the need to restrict and pace
activities to decrease oxygen consumption during the acute episode.
- (i) Explain the type of oxygen therapy being
used and why its maintenance is important.
- Issues related to home oxygen use, storage, or precautions
need to be addressed.
- (i) Teach the patient appropriate deep
breathing and coughing techniques.
- To facilitate adequate air exchange and secretion
- (c) Assist patient in obtaining home
nebulizer, as appropriate, and instruct in its use in collaboration with
- (c) Refer to home health services for nursing
care or oxygen management as appropriate.
Respiratory Monitoring; Oxygen Therapy; Airway Management
~ Care Plan Index ~
Outcomes Index ~
~ Care Plan Constructor Home ~