OXYGENATION

Learning Outcomes

Discuss respiration phases Discuss concept of partial pressure Describe components of nursing

assessment of respiratory system Use assessment parameter to determine

characteristics and severity of the major symptoms of respiratory dysfunction

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Function of Respiratory System Facilitates oxygen transport, respiration and

ventilation, and gas exchange. Oxygen (O2) supplied to and carbon dioxide

(CO2) from cells by way of circulating blood. O2 diffuses from the capillary through the

capillary wall to the interstitial fluid. Then it diffuses through the membrane of tissue cells where it is used for cellular respiration.

CO2 occurs by diffusion in the opposite direction.

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Respiration

After capillary exchange, blood enters the systemic veins (venous blood) and travels to pulmonary circulation.

O2 concentration in blood within capillaries of lung is lower than in the alveoli therefore O2 diffuses from alveoli to blood.

CO2 has higher concentration in blood than alveoli therefore diffuses from blood to alveoli.

Ventilation continually replenishes the O2 and removes the CO2 from airways and lungs.

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Ventilation

Physical factors that govern air flow in and out the lungs refer to mechanics of ventilation. This includes: Air pressure variances Resistance to air flow Lung compliance

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Air Pressure Variances

Air flows from regions of higher pressure to a region of lower pressure.

Inspiration: lowers pressure inside of thorax to pressure below that of atmospheric pressure.

Expiration: lungs recoil and decrease size of thoracic cavity resulting in alveolar pressure that exceed atmospheric pressure.

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Airway Resistance

Any process that changes the bronchial diameter or width affects airway resistance and alters rate of air flow fro a given pressure gradient. Asthma Chronic bronchitis Airway obstruction from tumor Loss of lung elasticity

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Compliance

Pressure changes can change lung volume. Measure of elasticity, expandability, and

distendability of the lungs and thoracic structures is called compliance.

Surface tension of the alveoli and connective tissue can affect lung compliance.

Compliances is determined by examining the volume pressure relationship in the lungs and thorax

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Compliance Continued

Normal = (1.0L/cm H20) if lungs and thorax easily stretch and distend when pressure is applied.

High = when lungs lose elasticity and thorax is over distended e.g.. Emphysema

Low – lungs and thorax stiff e.g.. Pneumothorax, pleural effusion, pulmonary fibrosis. Patient need to greater than normal energy to achieve normal levels of ventilation.

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Lung Volume (see table 21-1) Tidal volume: volume of air inhaled and

exhaled with each breath. 500 ml Inspiratory reserve volume: maximum

volume of air that can be inhaled after normal inhalation. 3000 ml

Expiratory reserve volume: the maximum volume of air that can be exhaled forcibly after a normal exhalation. 1100 ml

Residual volume: volume of air remaining in the lungs after a maximum exhalation. 1200 ml

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Lung Capacities (see table 21-1) Vital capacity: maximum volume of air

exhaled from the point of maximum inspiration. 4600 ml

Inspiratory capacity: maximum volume of air inhaled after normal expiration. 3500 ml

Functional residual capacity: volume of air remaining in the lungs after a normal expiration. 2300 ml

Total lung capacity: volume of air in the lungs after a maximum inspiration. 5800 ml

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So What?

Obesity, ascities, pregnancy can decrease expiratory reserve volume.

Obstructive disease can increase residual volume.

Generalized fatigue, pulmonary edema, COPD and decrease vital capacity

Functional residual capacity can be increased with COPD and decreased with ARDS

Lung capacity may be decreased with pneumonia, COPD.

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Ventilation and Perfusion

Ventilation is the flow of gas in and out of lungs

Perfusion is the filling of the pulmonary capillaries with blood.

Adequate gas exchange depends on ventilation and perfusion (V/Q).

Alterations occur with changes in pulmonary artery pressure, alveolar pressure, and gravity.

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V/Q States

Low: perfusion exceeds ventilation e.g.. obstruction of distal airways e.g. pneumonia, atelectasis, tumor

High: ventilation exceeds perfusion e.g. pulmonary emboli, pulmonary infarction and cardiogenic shock.

Silent: absence of ventilation and perfusion pneumothorax ad severe respiratory distress syndrome.

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Partial Pressure

Air mixture gaseous consisting of nitrogen, O2 and CO2, water vapor, helium and argon.

Atmospheric pressure at sea level is about 760 mmHg.

Partial pressure is the pressure exerted by each type of gas in a mixture of gases and proportional to the concentration of that gas in the mixture.

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Partial Pressure (PO2)

For purposes of blood gas analysis, the amount of a gas present is expressed in terms of "partial pressure." This is the amount of total gas pressure due to the substance being measured. For example, at sea level the total atmospheric pressure is 760 mm Hg. The amount of this pressure that is due to oxygen is 0.21 x 760 = 160 mm Hg. We would say that the partial pressure of oxygen at sea level in dry air is 160 mm Hg.

If atmospheric pressure is lower, the partial pressure of a gas will be proportionately decreased. In Salt Lake City, the atmospheric pressure is 647 mm Hg. The partial pressure of oxygen in dry air in Salt Lake is 0.21 x 647 = 136 mm Hg.

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Partial Pressure (PCO2)

The partial pressure of carbon dioxide in dry air at sea level is 0.03 x 760 = 0.3 mm Hg. However, in the lung carbon dioxide exits the blood to raise the carbon dioxide content of the air. The partial pressure of carbon dioxide in the lung air sacs is around 40 mm Hg. Because this carbon dioxide gas must displace oxygen and nitrogen, the partial pressure of oxygen in the lung air sac will be lower than in outside air.

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Partial Pressure (Water Vapor) Water vapor enters the air when it's exposed

to water. The maximum amount of water vapor in the air varies with temperature. At body temperature (37 centigrade) air can be saturated up to 47 mm Hg. As further water vapor enters the air, other water must condense out - the water content of the air is limited to 47 mm Hg. Therefore in the lung, where air is totally water-saturated, the partial pressure of water vapor would be 47 mm Hg.

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Partial Pressure Continued

Large amounts of O2 can be transported in blood because it combines easily with hemoglobin to form oxyhemoglobin.

Volume dissolved in plasma varies with the partial pressure of oxygen in the arteries (PaO2).

Higher the PaO2, the greater the amount of O2 dissolved.

PaO2 is the amount of oxygen combined with hemoglobin.

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Nursing Assessment Inspection Chest inspection allows you to see visible

external signs of respiratory function. Assess the front, back, and sides of the chest

for any scars, wounds, or lesions. Look for symmetry of chest wall movement.

Observe the duration of the inspiratory/expiratory cycle. Prolonged expiration occurs when an individual has difficulty expelling air, as is often seen in patients with emphysema.

Note the patient's respiratory pattern and breathing rhythm. In a healthy adult, inaudible respirations should occur between 12 and 20 times each minute.

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Inspection Continued

Look to see if the patient uses accessory muscles of respiration. Observe for intercostal retractions, nasal flaring, or pursed lip breathing, all of which indicate airflow obstruction and poor ventilation. Intercostal retractions are visible indentations between the ribs as the intercostal muscles aid in breathing. Nasal flaring describes intermittent outward movements of the nostrils with each inspiration. Pursed lip breathing refers to partial closure of the lips to allow air to be expired slowly.

Inspect the neck and look at the patient's posture. A patient with chronic obstructive pulmonary disease (COPD) will lean forward and prop himself up with his arms to improve breathing. Postural changes may also be seen with thoracic deformities such as scoliosis and kyphosis.

Observe the patient's level of consciousness. Confusion or changes in mental status are important signs of potential respiratory problems.

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Palpation

Use the surface of the fingers and hands to feel for abnormalities. identify chest movement symmetry, chest skeletal abnormalities, tenderness, skin temperature changes, swelling, and masses.

To assess the symmetry of chest expansion during breathing, stand behind the person, and place your hands with fingers spread apart beneath his or her arms, on the sides of the chest, about 2 inches below the axilla. Your fingers should be pointing toward the anterior chest - this will let you feel the chest rising and falling on inspiration and expiration. Ask the person to breathe out completely – observe your hands and thumbs to see that they have moved equally on both sides.

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Palpation Continued

After checking for symmetrical chest expansion, feel for tactile fremitus. Fremitus refers to vibratory tremors that can be felt through the chest by palpation. To assess for tactile fremitus, ask the patient to say “99” or “blue moon”. While the patient is speaking, palpate the chest from one side to the other. Tactile fremitus is normally found over the mainstem bronchi near the clavicles in the front or between the scapulae in the back. As you move your hands downward and outward, fremitus should decrease. Decreased fremitus in areas where fremitus is normally expected indicates obstruction, pnemothorax, or emphysema. Increased fremitus may indicate compression or consolidation of lung tissue, as occurs in pneumonia.

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Percussion

Percussion is an assessment technique which produces sounds by the examiner tapping on the patient's chest wall. Just as lightly tapping on a container with your hands produces various sounds, so tapping on the chest wall produces sounds based on the amount of air in the lungs.

Percussion sets the chest wall and underlying tissues into motion, producing audible sounds and palpable vibrations. Percussion helps to determine whether the underlying tissues are filled with air, fluid, or solid material.

Percussing the anterior chest is most easily done with the patient lying supine; the patient should sit when percussing the posterior chest. Place the first part of the middle finger of your nondominant hand firmly on the patient's skin. Then, strike the finger placed on the patient's skin with the end of the middle finger of your dominant hand.

Work from the top part of the chest downward, comparing sounds heard on both the right and left sides of the chest. Visualize the structures underneath as you proceed.

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Percussion Continued

Resonant sounds are low pitched, hollow sounds heard over normal lung tissue.

Flat or extremely dull sounds are normally heard over solid areas such as bones.

Dull or thud like sounds are normally heard over dense areas such as the heart or liver. Dullness replaces resonance when fluid or solid tissue replaces air-containing lung tissues, such as occurs with pneumonia, pleural effusions, or tumors.

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Percussion Continued

Hyperresonant sounds that are louder and lower pitched than resonant sounds are normally heard when percussing the chests of children and very thin adults. Hyperresonant sounds may also be heard when percussing lungs hyperinflated with air, such as may occur in patients with COPD, or patients having an acute asthmatic attack. An area of hyperresonance on one side of the chest may indicate a pneumothorax.

Tympanic sounds are hollow, high, drum like sounds. Tympany is normally heard over the stomach, but is not a normal chest sound. Tympanic sounds heard over the chest indicate excessive air in the chest, such as may occur with pneumothorax.

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Auscultate

Normal breath sounds are classified as tracheal, bronchial, bronchovesicular, and vesicular sounds. The patterns of normal breath sounds are created by the effect of body structures on air moving through airways. In addition to their location, breath sounds are described by: duration (how long the sound lasts), intensity (how loud the sound is), pitch (how high or low the sound is), and timing (when the sound occurs in the

respiratory cycle).

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Diagram Front & Back28

Crackles (Rales)

Crackles (or rales) are caused by fluid in the small airways or atelectasis. Crackles are referred to as discontinuous sounds; they are intermittent, nonmusical and brief. Crackles may be heard on inspiration or expiration. The popping sounds produced are created when air is forced through respiratory passages that are narrowed by fluid, mucus, or pus. Crackles are often associated with inflammation or infection of the small bronchi, bronchioles, and alveoli. Crackles that don't clear after a cough may indicate pulmonary edema or fluid in the alveoli due to heart failure or adult respiratory distress syndrome (ARDS).

Crackles are often described as fine, medium, and coarse. Fine crackles are soft, high-pitched, and very brief. You can

simulate this sound by rolling a strand of hair between your fingers near your ear, or by moistening your thumb and index finger and separating them near your ear.

Coarse crackles are somewhat louder, lower in pitch, and last longer than fine crackles. They have been described as sounding like opening a Velcro fastener.

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Wheezing

Wheezes are sounds that are heard continuously during inspiration or expiration, or during both inspiration and expiration. They are caused by air moving through airways narrowed by constriction or swelling of airway or partial airway obstruction.

Wheezes that are relatively high pitched and have a shrill or squeaking may occur when airways are narrowed, such as may occur during an acute asthmatic attack.

Wheezes that are lower-pitched sounds with a snoring or moaning may indicate secretions in large airways, such as occurs with bronchitis, may produce these sounds; they may clear somewhat with coughing.

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Pleural Friction Rub

Pleural friction rubs are low-pitched, grating, or creaking sounds that occur when inflamed pleural surfaces rub together during respiration. More often heard on inspiration than expiration, the pleural friction rub is easy to confuse with a pericardial friction rub. To determine whether the sound is a pleural friction rub or a pericardial friction rub, ask the patient to hold his breath briefly. If the rubbing sound continues, its a pericardial friction rub because the inflamed pericardial layers continue rubbing together with each heart beat - a pleural rub stops when breathing stops.

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Stridor

Stridor refers to a high-pitched harsh sound heard during inspiration.. Stridor is caused by obstruction of the upper airway, is a sign of respiratory distress and thus requires immediate attention.

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