`Arterial Blood Gas (ABG)

Specimen of arterial blood that assesses oxygenation, ventilation, and acid-base status.

Performed to evaluate the client’s acid-base balance and oxygenation. Arterial blood is used because it provides a truer reflection of gas exchange in the pulmonary system than venous blood. Blood gases may be drawn by laboratory technicians, respiratory therapy personnel, or nurses with specialized skills. Because a high –pressure artery is used to obtain blood, it is important to apply pressure to the puncture site for 5 minutes. After the procedure to reduce the risk of bleeding or bruising.

Six Measurements are commonly used to interpret arterial blood gas test: Ph :a measure of relative acidity or alkalinity of the blood. PaO2: the pressure exerted by oxygen dissolved in the plasma of arterial

blood; an indirect measure of blood oxygen content. PaCO2 : the partial pressure of carbon dioxide in arterial plasma; the

respiratory component of acid-base determination. Bicarbonate HCO 3־ : a measure of the metabolic component of acid-base

balance. Base Excess (BE): a calculated value of bicarbonate levels, also reflective

of the metabolic component of acid-base balance. Oxygen Saturation (SaO2): the percentage of hemoglobin saturated

(combined) with oxygen.

Procedure of obtaining specimen for ABG:1. Do Allen’s test (to check for competence of the artery from which

sample will be derived)2. Use Heparinized syringe (heparin is flushed through the barrel of the

syringe)3. No bubbles in the syringe (remember, it is blood gas being measured

here)4. Send specimen on ice and occlude needle to prevent air from coming

in the syringe5. Check site for hematoma, bleeding, and pain6. Avoid suctioning prior to drawing blood specimen.

Normal Values of Arterial Blood Gases

pH 7.35-7.45PaO2 80-100 mmHgPaCO2 35-45 mmHgHCO3־ 22-26 meq/LBE -2 to +2 meq/LSaO2 95-98%

InterpretationsPh: less than 7.35~ acidosisPh: greater than 7.45~alkalosis

If ph is 7 and below or 7.8 and above death occurs. PCO2: less than 35

~alkalosisPCO2: greater than 45~acidosis

HCO3: less than 22~acidosis

HCO3: greater than 26~alkalosis

If pH and PCO2 are primarily affected, Respiratory Acid-Base Imbalance will result.

If pH and PCO3 are primarily affected, Metabolic Acid-Base Imbalance will be experienced.

The kidneys and lungs attempts to compensate one another in maintaining acid-base balance.

In acid-base imbalances, the normal bicarbonate-carbonic acid ratio of 20:1 is lost. The body attempts to compensate in an effort to maintain the normal 20:1 ratio.

In compensation, the kidneys attempt to compensate for changes in blood CO2 by making a corresponding adjustment in blood bicarbonate. Normally, almost all the bicarbonate formed by the kidneys are retained.

On the other hand, the lungs attempt to compensate for abnormal changes in blood bicarbonate by making corresponding adjustment in blood CO2.

Another compensatory mechanism for acid-base imbalances is shifting of hydrogen ions from the ECF to the ICF or vice versa:

Chest PhysiotherapyWhat is chest Physiotherapy?Chest physiotherapy usually refers to the used to postural drainage in combination with adjunctive techniques that are thought to enhance the clearance of the mucus from the airway. These techniques include manual percussion, vibration, and squeezing of the chest. The goals of chest physiotherapy are to remove bronchial secretions, improve ventilation and increase the efficiency of the respiratory muscles. Why do we need to perform Chest Physiotherapy?to remove the secretions toallow more effectivebreathing and increase theamount of oxygen getting intothe body. POSTURAL DRAINAGE(Segmented Bronchial Drainage)

This uses gravity and correct positioning to bring the secretions into the throat where it is easier to remove.

Because the patient usually sits in an upright position, secretions are likely to accumulate in the lower parts of the lungs. When postural drainage is used, the patient is placed sequentially in different positions, so that the force of gravity helps to drain secretions from the smaller bronchial airways to the main bronchial and trachea. The secretions then are removed by coughing.

Nursing Consideration

The nurse should be aware of the patient’s diagnosis as well as the lung lobes or segments involved, the cardiac status and any structural deformities of the chest wall and spine. Auscultating the chest before and after the procedure helps to identify the areas needing drainage and the effectiveness of treatment.

Postural drainage is usually performed two to four times daily, before meals (to prevent nausea, vomiting and aspiration.) And at the bedtime. If prescribed, bronchodilators, water or saline may be nebulized and inhaled before postural drainage to dilate the bronchioles, reduce bronchospasm, decrease the thickness of mucus and sputum and combat edema of the bronchial walls. Percussion

Percussion is rhythmically striking the chest wall with cupped hands. It is also called cupping, clapping, or tapotement. The purpose of percussion is to break up thick secretions in the lungs so that they can be more easily removed. Percussion is performed on each lung segment for one to two minutes at a time.

VibrationTechnique of applying manual compression and tremor to the chest

wall during the exhalation phase of respiration. This maneuver helps to increase the velocity of the air expired from the small airways, freeing the mucus. After three or four vibrations the patient is encouraged to cough, using the abdominal muscles.

Nursing InterventionWhen performing chest physiotherapy, it is important to make sure

the patient is comfortable, is not wearing restrictive clothing and has not just eaten a meal. The upper most of the lungs are treated first. Medication is given for pain, as prescribed, before percussion and vibration: and pillows are used to support as needed. The positions are varied, but focus is placed on the affected areas. On completion of the treatment, the patient is assisted to a comfortable position. The treatment should be stopped if any of the following develop:

• Increased pain • Increased shortness of breath • Weakness • Light-headedness • Hemoptysis • Precautions!

Chest physiotherapy should not be performed on people with: • bleeding from the lungs• neck or head injuries• fractured ribs• collapsed lungs• damaged chest walls• tuberculosis

• acute asthma• recent heart attack• pulmonary embolism• lung abscess• active hemorrhage• some spine injuries• recent surgery, open wounds, or burns •