Makindo Medical Notes

Introduction

Oxygen therapy is a critical component in the management of patients with hypoxemia and various respiratory conditions. It involves the administration of supplemental oxygen to maintain adequate tissue oxygenation, prevent hypoxia, and reduce the work of breathing. Understanding the appropriate use of oxygen delivery devices and their indications is essential for effective patient care.

Hypoxia can be life-threatening. Oxygen delivery depends on multiple variables, including the type of mask, the patient's respiratory rate, and minute volume. Simply increasing the flow rate does not always equate to a higher inspired oxygen concentration (FiO₂). The concentration of oxygen a patient inhales is determined by both the device used and the patient's breathing pattern. Fixed performance systems, like Venturi masks, allow for more accurate control of FiO₂.

Indications for Oxygen Therapy

• Correcting hypoxemia of any cause
• Acute myocardial infarction
• Severe trauma
• Post-anesthesia recovery
• Acute severe asthma
• Acute pulmonary edema
• Acute respiratory distress syndrome (ARDS)
• Pneumothorax (to aid reabsorption of air)
• Acute sickle cell crisis if hypoxic
• Cluster headaches
• Carbon monoxide poisoning

Precautions and Potential Complications

Oxygen therapy should be titrated to achieve adequate oxygenation while minimizing potential risks. Excessive oxygen administration can lead to complications, particularly in certain patient populations.

• May depress ventilation in patients with chronic hypercapnia (e.g., COPD patients who are CO₂ retainers)
• Can cause absorption atelectasis when high concentrations (>60% FiO₂) are used for prolonged periods
• Oxygen toxicity may occur with FiO₂ >50% for more than 24-48 hours
• In premature infants, high oxygen concentrations can lead to retinopathy of prematurity (ROP)
• Fire hazard due to the combustibility of oxygen-enriched environments

Types of Oxygen Delivery Devices

Oxygen delivery devices can be classified based on their ability to deliver variable or fixed concentrations of oxygen.

• Nasal Cannula:
  • Delivers low-flow oxygen at 1-6 liters per minute (L/min)
  • Provides approximately 24-44% FiO₂
  • Used for patients with mild hypoxemia or those requiring long-term oxygen therapy
  • Advantages: Comfortable, allows for eating and speaking
  • Limitations: FiO₂ varies with patient's breathing pattern
• Simple Face Mask (Hudson Mask):
  • Delivers oxygen at 5-10 L/min
  • Provides approximately 40-60% FiO₂
  • Used when moderate concentrations of oxygen are needed
  • Requires a minimum flow rate of 5 L/min to prevent CO₂ rebreathing
• Venturi Mask:
  • Delivers precise oxygen concentrations ranging from 24% to 60% FiO₂
  • Uses color-coded adapters to set specific FiO₂ levels
  • Ideal for patients who require controlled oxygen therapy, such as those with COPD
  • Advantages: Provides a consistent and accurate FiO₂ regardless of breathing pattern
• Non-Rebreather Mask with Reservoir Bag:
  • Delivers high-flow oxygen at 10-15 L/min
  • Provides up to 60-90% FiO₂
  • Has a reservoir bag and one-way valves to prevent rebreathing of exhaled air
  • Used in patients with severe hypoxia requiring high oxygen concentrations
  • Ensure the reservoir bag is inflated before placing on the patient
• High-Flow Nasal Cannula (HFNC):
  • Delivers heated and humidified oxygen at flow rates up to 60 L/min
  • Provides adjustable FiO₂ up to 100%
  • Used in moderate to severe respiratory distress
  • Advantages: Reduces dead space, improves comfort, and provides some positive airway pressure
• Bag-Valve Mask (BVM):
  • Manual resuscitator used to provide positive pressure ventilation
  • When connected to oxygen, can deliver nearly 100% FiO₂
  • Used in emergency situations when patients are not breathing adequately or at all
• Continuous Positive Airway Pressure (CPAP):
  • Provides continuous positive airway pressure to keep airways open
  • Used in conditions like obstructive sleep apnea, pulmonary edema, and certain cases of respiratory distress
  • Can deliver variable FiO₂ depending on oxygen settings
• Bilevel Positive Airway Pressure (BiPAP):
  • Delivers two levels of positive airway pressure: higher during inhalation (IPAP) and lower during exhalation (EPAP)
  • Used in patients with COPD exacerbations, respiratory failure, or sleep apnea
  • Allows for better ventilation support compared to CPAP

Clinical Indications for Specific Devices

• Nasal Cannula:
  • Mild hypoxemia
  • Stable patients requiring low oxygen supplementation
  • Patients who require mobility and comfort
• Simple Face Mask:
  • Moderate hypoxemia
  • Short-term therapy when higher FiO₂ is needed
• Venturi Mask:
  • Patients with COPD who require precise oxygen concentrations to prevent CO₂ retention
  • Patients at risk of hypoventilation with uncontrolled oxygen therapy
• Non-Rebreather Mask:
  • Severe hypoxia
  • Acute medical emergencies (e.g., trauma, myocardial infarction, pulmonary embolism)
  • Carbon monoxide poisoning
• High-Flow Nasal Cannula:
  • Moderate to severe respiratory distress
  • Patients requiring high FiO₂ with added benefits of humidification and reduced work of breathing
• Bag-Valve Mask:
  • Respiratory arrest
  • Assisting ventilation in patients with inadequate breathing
• CPAP/BiPAP:
  • Type I respiratory failure (CPAP)
  • Type II respiratory failure due to COPD exacerbations (BiPAP)
  • Sleep apnea management

Adjusting Oxygen Therapy

Oxygen therapy should be adjusted based on the patient's oxygen saturation (SpO₂) levels, clinical condition, and target oxygen saturation ranges.

• For most acutely ill patients: Target SpO₂ of 94-98%
• For patients at risk of CO₂ retention (e.g., COPD): Target SpO₂ of 88-92%
• Regular monitoring of SpO₂ and clinical assessment is essential
• Adjust oxygen delivery devices and flow rates accordingly to achieve target saturations

Summary of Oxygen Delivery Devices

Color-Coded Venturi Mask Adapters

Key Points

• Always assess the patient's clinical condition and oxygenation status before adjusting oxygen therapy
• Be aware of the risks of oxygen toxicity and CO₂ retention in susceptible patients
• Use pulse oximetry to monitor oxygen saturation and adjust therapy accordingly
• Document oxygen therapy, including device type, flow rate, and patient's response
• Ensure proper mask fit and check for leaks to optimize oxygen delivery

References

• British Thoracic Society (BTS) Guidelines for Oxygen Use in Adults in Healthcare and Emergency Settings
• NICE Guidelines on the Use of Oxygen Therapy
• World Health Organization (WHO) Oxygen Therapy for Children: A Manual for Health Workers