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Wednesday, July 21, 2010

Respiratory Failure Lexicon

1. Respiratory Failure: Failure of the lungs to provide adequate oxygenation or ventilation for the blood. May result from either oxygenation failure or ventilation failure.

2. Oxygenation failure: PO2 less than 60 with an FiO2 greater than 60. Increased oxygenation does not improve PO2. Also referred to refractory hypoxemia.

3. Refractory Hypoxemia: PO2 less than 60 with an FiO2 greater than 60.

4. Ventilatory Failure: Inadequate Ventilation between the lungs and atmosphere resulting in an inapropriate elevation of CO2 in teh arterial blood to a level greater than 45. May actually be clinically diagnosed when the pH is less than 7.35 and the CO2 is higher than 45 (some patients have a normal pH with a higher CO2, and this is not indicative of respiratory failure).

5. Hypoxemia: This refers to low levels of oxygen in the blood. Is present when the PO2 is below the predicted normal for the patient. For most patients. For patients older than 60, you should subtract 1 from these values for each year older than 60, whereas mild hypoxemia for a 70 YO may be a PO2 of 50-70. The degree of hypoxemia is defined as below:
  • Mild hypoxemia: PO2 equals 60-79
  • Moderate Hypoxemia: PO2 equalls 40-59
  • Severe Hypoxemia: PO2 less than 40
6. Hypoxia: This refers to low amount of oxygen in the tissues, and may lead to serious consequences as a result of inadequate tissue oxygenation. This usually results in an increase in cardiac output, which may be observed by an increase in heart rate and blood pressure. Patients with severe hypoxia or poor cardiac function may not be able to compensate. Hypoxia may result in severe consequences.

7. Hypoxic Hypoxemia: This is hypoxemia that results in hypoxia. Diagnosed by low PO2 and low tissue perfussion which may be observed by cyanosis.

8. Cyanosis: A blue discoloration of the skin due to tissue hypoxia.

9. Central Cyanosis: A blue discoloration of the core of the body, such as the face and chest, caused by moderate to severe tissue hypoxia and hypoxemia.

10. Acrocyanosis: A blue discoloration of the fingers, toes and lips that may result from mild-moderate tissue hypoxia.

11. V/Q mismatching: This is the most common cause of tissue hypoxia. This occurs when some region of the lungs is poorly ventilated but remains well perfused (blood flow is normal). The result here is that some blood leaves the lungs without getting oxygenated. To determine if hypoxia is caused by V/Q mismatching, increase the FiO2 and watch the SpO2 and PO2. If the SpO2 and PO2 increase with increasing the oxygen, then you probably have a disease of V/Q mismatching. Diseases of V/Q mismatching include: PE, pneumothorax, asthma,emphysema, pneumonia, bronchitis, heartfailure, congenital heart disease, aging.

12. Shunting: This is another cause of hypoxia/hypoxemia. This refers to blood being shunted from the right side of the heart to the left without coming in contact with the lungs. This is a result of poor perfusion of bloodflow to the lungs or in the lungs, even while the patient continues to have good ventilation (CO2 is normal). To determine if hypoxia is caused by shunting, increase the FiO2 and watch the SpO2 and PO2. If the SpO2 and PO2 DO NOT INCREASE with increasing the oxygen, you probably have some degree of shunting. Diseases of shunting include: pneumonia, atelectasis, pulmonary edema, ARDS, congenital heart defects of the neonate

13. Abdominal alterans: Alternating for short periods between breathing with the accessory muscles and breathing with the diaphragm.

14. Abdominal paradox: The inward movement of the abdomen with each inspiratory effort. Also referred to as paradoxical breathing.

I'll add the above to the Respiratory Therapy Lexicon.

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