Question

Case 3

Brenda Williams is a 73 year old retired seamstress. She is a chain smoker. When her employer announced that smoking would no longer be allowed in the store, she retired. Since her retirement, Mrs. Williams has not been feeling well. She fatigues easily, even with light exertion. She has dyspnea and recently has begun to sleep on two pillows.

Early this morning, Mrs. Williams woke up with severe dyspnea and called 911. EMTs found her alert and oriented, and in significant respiratory distress. Her skin was pale with cyanotic nail beds, cool, and moist. Her pulse was 112, regular, and strong. Her respirations were 26, regular rhythm and depth, and labored. She had an increased anteroposterior chest diameter and audible expiratory wheezes. Blood pressure was 128/85. SpO2 was 83%. They noted pitting edema of her ankles. She denied chest pain. They put her on oxygen and transported her to the emergency room.

Her physician noted a long expiratory phase in her breathing. Based on this observation, her history, and her vital signs, he ordered the following tests:

Pulmonary function tests:
Vorced Expiratory Capacity (FEV1): reduced Residual volume: increased
Laboratory values:
Hemoglobin 14.5 g/dL (normal 12-15 g/dL) Arterial PO2 48 mmHg (normal 100 mmHg) O2 saturation 86% (normal 98-100%)
Arterial PCO2 69 mmHg (normal 40 mmHg) HCO3-: 34 mEq/L (normal 24 mEg/L)
pH: 7.31

The physician concludes that Mrs. Williams has a combination of emphysema and chronic bronchitis, called chronic obstructive pulmonary disease.

Questions:

9. Explain why Mrs. Williams was in respiratory distress.

10.Explain the physiological reasons for the signs that the EMTs assessed (skin, pulse, respiration, anteroposterior chest diameter, blood pressure, pulse oximetry, and pitting edema).

11.Explain the physiological reasons for each of her test results (both pulmonary and laboratory).

12.Which acid-base disorder does she have? What is the cause? What is the compensation? How does this alter oxygen delivery to the tissues?

13.Explain why her hemoglobin was normal but her SpO2 and her arterial PO2 were low. Should these tests have similar outcomes?

Answer 1

Answer 9:

The cause of respiratory distress is Acute exacerbation of Chronic obstructive pulmonary disease:

Clues to the diagnosis:

1. The patient has a history of smoking
2. The patient complains of breathlessness with minimal exertion
3. High respiratory rate
4. Prolonged expiratory phase
5. cyanosis - suggestive of low oxygen levels in the blood
6. Unable to sleep in the supine position and bilateral leg edema - suggestive of right heart failure
7. Increase anteroposterior diameter - suggestive of lung hyperinflation.
8. Wheeze - suggestive of expiratory airflow obstruction
9. Arterial blood gas - suggestive respiratory acidosis - ( low pH and high pCO2) - suggestive of respiratory muscle fatigue.

Answer 10:

1. Skin - cyanosis - due to increasing level of reduced hemoglobin in blood
2. Pulse - there is an increase in the pulse rate. this is because hypoxia
3. Respiratory -
   1. Increase respiratory rate - this is due to respiratory distress
   2. Wheeze - this is due expiratory airflow obstruction
   3. Prolonged expiratory phase - this is due expiratory airflow obstruction
4. Increase anterior-posterior diameter of the thorax - is due to hyperinflation.
   1. In COPD. there is expiratory airflow obstruction.
   2. This leads to incomplete exhalation of air. In other words, this leads to air trapping.
   3. This causes alveolar inflation.
   4. As a result, the lung is hyperinflated.
   5. When the patient has an acute attack of bronchospasm, this problem aggravates
5. Blood pressure is slightly high - due to respiratory distress
6. Pulse oximetry - the patient is respiratory distress due to bronchospasm and reduce alveolar surface area for oxygen exchange ( emphysema). therefore, the ventilation/perfusion ratio decreases and leads to incomplete oxygenation the blood entering the lungs. The overall effect is hypoxia
7. Pitting edema is due to right heart failure.
   1. COPD has lead to hypoxia
   2. Hypoxia causes vasospasm of the pulmonary vasculature.
   3. This causes increase in the blood pressure in the pulmonary vessel
   4. This leads to pulmonary hypertension.
   5. The right heart pumps blood into the lungs.
   6. As the right heart now has to work against the high blood pressure in the pulmonary veins, it fails.
   7. This leads to an increase in pressure downstream in the vena cava.
   8. This leads to engorged neck veins, passive hepatomegaly, and pedal edema

Answer 11:

The forced expiratory volume is reduced - because - there is expiratory airflow obstruction. Therefore, the patient is unable to exhale completely.

The residual volume is increased - due to incomplete exhalation, there is air trapping inside the lung, therefore, the amount of air remaining inside the lung even after forceful exhalation is high.

Answer 12:

This patient has uncompensated respiratory acidosis.

check the pH = 7.31. this is less than normal ( 7.35 - 7.45)

now check the pCO2 - 69. The pCO2 is high

Remember:

1. If the reduces pH and the increases pCO2 = respiratory acidosis
2. If the pH reduces and HCO3 also reduces= metabolic acidosis
3. If the pH increase and pCO2 reduces - respiratory alkalosis
4. If the pH increases and the HCO3 also increases = respiratory alkalosis

In this case, the pCO2 is high and the pH is low = this is suggestive of respiratory acidosis

The bicarb is also high. This means the kidneys have started compensating the low pH but not complete yet.

The pO2 is less than 60 mmHg - this is suggestive of hypoxia

When the pH falls (acidosis ) the oxygen dissociation curve moves towards the right. This means there will be increased unloading of Oxygen at the tissue level.

Answer 13:

The hemoglobin is normal - this means the patient's oxygen-carrying capacity of the blood is normal

The pCO2 and sPO2 is less because there is bronchospasm and destruction of the respiratory membrane. This has lead to reduce oxygen levels in the alveoli. Hence, the oxygen in the blood is also low.

So the hypoxia is due to the lung condition and not due to lack of hemoglobin.