Is it safe to inhale nitrous oxide (N2O) during delivery if you have asthma?

Safety of Nitrous Oxide During Delivery for Asthma Patients

Nitrous oxide (Entonox) should be avoided in patients with asthma during delivery due to potential risks of hypercapnia and swinging between hyperoxaemia and hypoxaemia. 1

Understanding Nitrous Oxide Use in Labor

Nitrous oxide is commonly used as an analgesic during labor in the form of Entonox, a 50:50 mixture of oxygen and nitrous oxide. While it provides rapid onset of analgesia with minimal side effects for many patients, special considerations apply to those with asthma.

Mechanism and Administration

• Self-administered via facemask with a demand valve
• Rapid onset of action (within a few breaths)
• Primary side effect is drowsiness
• Rapid washout when mask is removed

Risks for Asthma Patients

The British Thoracic Society (BTS) guidelines specifically caution against using Entonox in patients at risk of respiratory complications:

• High oxygen concentration concerns: The 50% oxygen concentration in Entonox may precipitate hypercapnic respiratory failure in susceptible patients 1
• Risk of oxygen fluctuation: If the patient becomes drowsy from either hypercapnia or the sedating effect of Entonox, they may drop the mask, resulting in dangerous swings between hyperoxaemia and hypoxaemia 1
• Potential for bronchospasm: Nitrous oxide can potentially expand in air-filled cavities, which may be problematic for patients with reactive airway disease

Pregnancy and Asthma Management

Instead of focusing on nitrous oxide for pain management, priority should be given to maintaining optimal asthma control during pregnancy:

• Monthly monitoring of asthma symptoms and lung function during prenatal visits is essential 1, 2
• Maintain controller medications: It is safer for pregnant women to be treated with appropriate asthma medications than to have uncontrolled symptoms 1
• Preferred medications during pregnancy:
  • Albuterol (salbutamol) is the preferred SABA for rescue use 1, 2
  • Inhaled corticosteroids are the preferred long-term control medications 1, 2

Alternative Pain Management Options

For asthmatic patients in labor, consider these safer alternatives to nitrous oxide:

• Regional anesthesia (epidural or spinal) is generally safe and effective for asthmatic patients
• Opioid analgesics administered under appropriate supervision
• Non-pharmacological approaches: breathing techniques, positioning, massage, and hydrotherapy

Clinical Decision Algorithm

1. Assess asthma control before delivery:

   • Review medication use and adherence
   • Evaluate lung function if possible
   • Check for recent exacerbations

2. If asthma is well-controlled:

   • Still avoid nitrous oxide based on BTS guidelines 1
   • Recommend regional anesthesia as first-line pain management

3. If asthma is poorly controlled:

   • Optimize asthma management immediately
   • Absolutely avoid nitrous oxide
   • Consider early epidural placement
   • Have rescue medications readily available

Important Considerations

• Maintain oxygen saturation monitoring throughout labor for asthmatic patients
• Have rescue bronchodilators immediately available
• Ensure the labor and delivery team is aware of the patient's asthma diagnosis
• Consider monthly evaluation of asthma symptoms throughout pregnancy as recommended by guidelines 2

Remember that maintaining asthma control during pregnancy is crucial for both maternal and fetal health. Uncontrolled asthma poses greater risks than appropriate medication use during pregnancy 1, 2.