PB chp 13 Flashcards
(23 cards)
Improving the ventilatory status of a patient with hypercapnic respiratory failure can be accomplished how? (3 general concepts)
improving alveolar ventilation
reducing physiological dead space
reducing carbon dioxide (CO2) production
Improving oxygenation can be accomplished in what 4 general ways?
administering enriched oxygen
PEEP
CPAP
Patient Positioning
An increase in CO2 of 1 mm Hg will reduce the PaO2 by ?
1.25 mm Hg
reduction in oxygen in the tissues
Hypoxia
reduction in the partial pressure of oxygen in the blood
Hypoxemia
What causes Hypoxemic hypoxia?
lower than normal PaO2,
ascent to altitude,
hypoventilation
What causes Anemic hypoxia
lower than normal red blood cell count [anemia], abnormal hemoglobin,
What kind of Hypoxia does the patient have when they have reduced cardiac output, decreased tissue perfusion?
Circulatory hypoxia
What kind of Hypoxia does a patient have when cyanide poisoning is involved?
Histotoxic hypoxia
When hypoventilation causes hypoxemia, increasing ____ ______ generally improves oxygenation
minute ventilation
A patient with myasthenia gravis is placed on mechanical ventilation. The chest radiograph is normal. Breath sounds are clear. Initial ABGs on 0.25 FIO2 20 minutes after beginning ventilation are as follows: pH = 7.31; PaCO2 = 62 mm Hg; bicarbonate = 31 mEq/L; and PaO2 = 58 mm Hg. What change in ventilator setting might improve this patient’s ABG findings?
The patient has respiratory acidosis. The PaO2 indicates moderate hypoxemia. A common reaction by clinicians in this situation is to increase the FIO2. However, the cause of the hypoxemia is the elevated CO2. The PaCO2 is about 40 mm Hg above normal, therefore the PaO2 will be about 50 mm Hg below its actual value. The most appropriate way to increase the PaO2 is to increase ventilation.
What is PVO2 & its normal value?
Partial pressure of mixed venous oxygen
40mmhg
What is P(A-a)O2 & its normal value?
Alveolar-arterial oxygen tension gradient
5-10 mm Hg (FIO2 = 0.21)
30-60 mm Hg (FIO2 = 1.0)
PaO2/FIO2
PaO2 range = 80-100 mm Hg; FIO2 = 0.21
Ratio of PaO2 to fractional inspired oxygen
380-475
What is DO2 & its normal value?
Oxygen delivery
1000 mL/min
What is VO2 & its normal value?
Oxygen consumption
250 mL/min
Generally in chronic patients, what should you keep the FIO2 Below?
60%
100% FIO2 over long periods of time can cause what (3) to happen?
absorption Jo Anne
increase intrapulmonary shunting
o2 toxicity
After being supported on a ventilator for 30 minutes, a patient’s PaO2 is 40 mm Hg on an FIO2 of 0.75. Acid-base status is normal and all other ventilator parameters are within the acceptable range. PEEP is 3 cm H2O. What FIO2 is required to achieve a desired PaO2 of 60 mm Hg? Is your answer possible? Can you think of another form of therapy to improve oxygenation?
Desired FIO2 = (60 × 0.75)/40 = 1.13
No, this is not possible. You can’t give more than 100% oxygen. Along with increasing the FIO2 to 1, another method of improving oxygenation is to use PEEP.
If the PAW increases, what happens to the PaO2?
Increases
Factors that affect PAW during positive-pressure ventilation (5)
include peak inspiratory pressure (PIP) total PEEP (or auto-PEEP plus extrinsic or set PEEP [PEEPE] inspiratory-to-expiratory (I:E) ratios, respiratory rate (f) inspiratory flow pattern
As the percent of pulmonary shunt increases, hypoxemia worsens. What are some pathologic conditions associated with an increased shunt fraction.
atelectasis, pulmonary edema, pneumonia, pneumothorax, and complete airway obstruction.
What is the difference between PEEP and CPAP
The term PEEP as it is commonly used implies that the patient is receiving mechanical ventilatory support and the baseline pressure is above zero CPAP is pressure above the ambient pressure maintained during spontaneous ventilation.
With CPAP, expiratory positive airway pressure (EPAP) and inspiratory positive airway pressure (IPAP) are both positive and equal, albeit the ventilator does not provide mandatory breaths
