Chapter 181 - Oxygen therapy

Question 1

Explain why an increase in FiO2 will lead to an increase in arterial oxygen saturation of hemoglobin (SaO2) .

Answer 1

An increase in FiO2 will lead to an increase in SaO2 in most situations. With supplemental oxygen, there is an increase in the partial pressure of arterial oxygen (PaO2) and a subsequent shift of the oxyhemoglobin dissociation curve to the left, facilitating the binding of oxygen to hemoglobin and leading to a subsequent increase in SaO2.

The increase in SaO2 is more profound with primary pulmonary disease or injury causing a defect in gas exchange versus disease or injury causing anemia or a decrease in binding of oxygen to hemoglobin such as carbon monoxide poisoning.

Question 2

What percentage of FiO2 would be achieved with the following oxygen therapies?

1. Flow-by oxygen
2. Oxygen delivery with face mask
3. An oxygen hood using an Elizabethan collar and covering the opening 75–90% with clear plastic wrap
4. Nasal oxygen
5. Oxygen cage
6. transtracheal catheter (TTC)

Answer 2

1. 25-40%
2. Oxygen delivery with face mask provides for a variable FiO2 of 35–60%
3. 75–90%
4. through a nasal cannula can provide a FiO2 of up to 70%. However, the FiO2 delivered to the patient can be variable and is influenced by flow rates, panting, and respiratory rate.
5. for immediate delivery of a FiO2 up to 60%
6. 80%

Question 3

Contraindications for nasal oxygen?

Answer 3

facial trauma or other nasal obstruction precluding placement of nasal cannula or prongs.

Question 4

Recommended flow rate for nasal oxygen?

Answer 4

Recommended flow rate through each nasal cannula is 100 mL/kg/min.

Question 5

What patients would need intubation and positive pressure ventilation (PPV) ?

Answer 5

Patients presenting with severe work of breathing
hypoxemia (PaO2 < 60 mmHg or SpO2 < 90%)
hypercapnia (PaCO2 > 60 mmHg)
unresponsive to non-invasive oxygen support

Question 6

Complications associated with PPV?

Answer 6

Complications associated with PPV include ventilator-acquired pneumonia, pneumothorax, and effects of prolonged sedation and immobility.

Question 7

How does hyperbaric oxygen therapy work?

Answer 7

1. By increasing atmospheric pressure beyond 1 atmosphere (1atm), more oxygen can be dissolved in and transported by plasma.
2. increased amount of oxygen dissolved in blood will increase the partial pressure of oxygen as measured by PaO2. This allows for improved diffusion of oxygen into the tissues compared to oxygen being transported by hemoglobin.

Question 8

In terms of monitoring for oxygen therapy,

when should we escalate the current oxygen therapy?

Answer 8

SpO2 readings of less than 92% with continued signs of respiratory distress indicate the need for escalation of oxygen therapy.

PaO2 less than 70 mmHg with continued signs of respiratory distress requires escalation of oxygen therapy.

PaCO2 greater than 50 mmHg indicates hypoventilation and mechanical ventilation should be considered for these patients.