Principles and treatment monitoring
Controlled oxygen delivery reliably reduces in-hospital patient mortality compared to the use of 100% O₂. The main principle is flow titration monitored by a pulse oximeter. The starting flow rate is typically 5–7 L/min with a possible increase up to 10 L/min.
If a pulse oximeter is unavailable, therapy is still performed, but careful clinical observation is required. The onset of drowsiness, clinical deterioration, or fatigue may indicate the development of hypercapnia and progression of respiratory failure.
Indications and target values
The baseline criterion for initiating therapy is hypoxemia (SpO₂ < 90% or PaO₂ < 60 mmHg). However, in concurrent pulmonary hypertension, the treatment threshold is higher—SpO₂ < 92%.
In specific clinical situations, the tactics change:
- Bronchial asthma exacerbation: the target saturation in adults should not exceed 96%. Exceeding this leads to hyperoxia, which worsens outcomes and causes oxygen waste.
- ST-elevation myocardial infarction: routine oxygen administration with normal saturation (SpO₂ ≥ 90%) is not recommended. Therapy is indicated only in the presence of hypoxemia or acute heart failure.
- Influenza in adults: oxygen is administered in the presence of signs of acute respiratory failure and SpO₂ < 92%.
- Hepatopulmonary syndrome in liver cirrhosis: long-term oxygen therapy is the only recommended conservative method for severe hypoxia (PaO₂ < 60 mmHg or SatO₂ < 88% on room air, as well as during nocturnal desaturation).
Delivery systems and equipment
The choice of device depends on the severity of the patient's condition and their response to treatment:
- Low-flow nasal cannula: provides a fraction of inspired oxygen (FiO₂) of 0.25–0.4.
- Face mask: allows achieving an FiO₂ of 0.35–0.5.
- High-flow nasal cannula: used with specialized high-flow oxygen therapy devices.
Oxygen sources include cylinders or concentrators. Stationary concentrators are bulky and used at home, while modern portable models allow patients to walk and maintain mobility.
Long-term oxygen therapy (LTOT)
In chronic cor pulmonale, LTOT is a critically important component of pulmonary hypertension management. The regimen requires continuous, low-flow oxygen administration for 18–24 hours a day over many months. This reliably increases survival, reduces the severity of pulmonary hypertension, and improves quality of life.
Additionally, individually dosed normobaric hypo- and hyperoxygenation therapy can be used in stable ischemic heart disease to increase physical performance if standard exercise training is limited.
Hyperbaric oxygenation (HBO)
This is a method of tissue oxygenation under elevated pressure, implementing etiotropic and pathogenetic principles of hypoxia treatment.
Main indications for HBO:
- Anaerobic infections: high oxygen pressure suppresses the growth of anaerobes (e.g., in tetanus or gas gangrene caused by Clostridium perfringens).
- Traumatic brain injury: used as part of anticonvulsant therapy and respiratory support.
- Hemorrhage: used strictly after bleeding has been stopped to restore tissue oxygenation.
Non-invasive and invasive ventilation
If standard oxygen therapy is ineffective, non-invasive positive pressure ventilation (NIV) is applied. The method of choice is bilevel positive airway pressure (BiPAP). An absolute indication for NIV is daytime hypercapnia. The method combats hypoventilation, relieves dyspnea, and prevents chest wall muscle wasting (especially when using a high pressure difference).
If NIV fails, acidosis worsens, and severe hypoxemia persists, endotracheal intubation and transition to invasive mechanical ventilation are indicated.
Class and exam questions
Can oxygen therapy be administered if a pulse oximeter is not at hand?
Yes, the lack of a device is not a reason to withhold oxygen. However, in this case, strict clinical monitoring of the patient's condition is necessary to timely notice signs of hypercapnia (drowsiness, fatigue).
Do all patients with myocardial infarction need oxygen?
No, routine administration of oxygen to patients without hypoxemia (SpO₂ ≥ 90%) is not recommended. It is indicated only when saturation drops below 90% or when myocardial infarction is complicated by acute heart failure.
How to recognize a true shunt in hypoxemia?
The main sign of a true shunt is the inability to raise the PaO₂ level above 60 mmHg even when using high doses of oxygen. This is frequently seen in atelectasis, pneumothorax, pneumonia, or pulmonary embolism.
What else to study on this topic
- Pathophysiology of hypercapnia development during uncontrolled oxygen therapy.
- Specific features of the BiPAP mode and airway clearance techniques.
- Differential diagnosis of the causes of true intrapulmonary shunt.
- Medical therapy for hepatopulmonary syndrome and reasons for its ineffectiveness.
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