What conditions require supplemental oxygen at night?

Common Reasons for Nocturnal Supplemental Oxygen

Supplemental oxygen at night is most commonly recommended for chronic hypoxemia from pulmonary diseases, nocturnal desaturation in pulmonary arterial hypertension, sleep-disordered breathing with severe hypoxemia when positive airway pressure cannot be tolerated, and chronic lung disease of infancy with nocturnal oxygen desaturation. 1

Primary Indications by Disease Category

Chronic Obstructive Pulmonary Disease (COPD)

• Long-term oxygen therapy (LTOT) is indicated when resting PaO2 ≤7.3 kPa (55 mm Hg) or oxygen saturation ≤88%, which provides survival benefit and improves pulmonary hemodynamics. 1
• LTOT should be prescribed when resting PaO2 is ≤8 kPa (60 mm Hg) with evidence of peripheral edema, polycythemia (hematocrit ≥55%), or pulmonary hypertension. 1
• Nocturnal desaturation occurs commonly in COPD due to ventilation-perfusion mismatch, decreased functional capacity, and nocturnal hypoventilation particularly during REM sleep. 1
• Approximately one-third of COPD patients qualified for LTOT require increased oxygen flow during sleep beyond their daytime requirements. 2
• Current guidelines do not support oxygen therapy for moderate resting hypoxemia (SaO2 89-93%) or isolated exercise desaturation without meeting criteria for severe hypoxemia. 1, 3

Pulmonary Arterial Hypertension (PAH)

• Nocturnal desaturation occurs in 77% of patients with PAH, primarily related to underlying gas exchange disturbances rather than sleep apnea. 1
• The goal is to maintain oxygen saturation ≥90% in adults and ≥92% in infants and children during sleep to prevent hypoxia-induced pulmonary vasoconstriction that exacerbates pulmonary hypertension. 1
• Nocturnal desaturation is strongly associated with lower FEV1 values, lower resting oxygenation, and higher alveolar-arterial oxygen gradients. 1

Chronic Lung Disease of Infancy (CLDI) and Bronchopulmonary Dysplasia (BPD)

• Supplemental oxygen should maintain saturation ≥95% to promote growth and lung repair, provide adequate exercise tolerance, and diminish pulmonary artery hypertension. 1
• Oxygenation decreases during feeding and sleep, making monitoring during these periods essential before weaning from supplemental oxygen. 1
• Persistent nighttime oxygen is often necessary after daytime use has been discontinued due to altered lung mechanics and irregular breathing during sleep. 1
• Maintaining oxygen saturation >90% reduces the frequency of central apnea and transient elevations in pulmonary artery pressure. 1

Sleep-Disordered Breathing (SDB)

• For severe nocturnal hypoxemia (≥5% of recording time with SpO2 <90%) in patients who cannot tolerate positive airway pressure or are awaiting surgical treatment, nocturnal oxygen is suggested. 1
• Oxygen therapy significantly improves oxygen saturation in obstructive sleep apnea but is inferior to positive airway pressure in reducing apnea severity and may prolong obstructive apnea duration. 4
• In children with sleep-disordered breathing and severe nocturnal hypoxemia, supplemental oxygen increases oxygenation and may mitigate adverse cardiopulmonary consequences. 1

Interstitial Lung Disease (ILD)

• LTOT should be prescribed for patients with ILD with resting PaO2 ≤7.3 kPa (55 mm Hg). 1
• LTOT should be prescribed when resting PaO2 is ≤8 kPa (60 mm Hg) in the presence of peripheral edema or pulmonary hypertension. 1
• These recommendations are extrapolated from COPD evidence, as no randomized controlled trials exist specifically for ILD. 1

Cystic Fibrosis (CF)

• LTOT should be prescribed for patients with CF with resting PaO2 ≤7.3 kPa (55 mm Hg). 1
• LTOT should be prescribed when resting PaO2 is ≤8 kPa (60 mm Hg) with peripheral edema, polycythemia (hematocrit ≥55%), or pulmonary hypertension. 1
• Nocturnal low-flow oxygen effectively alleviates nocturnal hypoxemia in CF patients with stable COPD without causing clinically important hypercapnia. 5

Physiological Mechanisms Requiring Nocturnal Oxygen

Sleep-Related Oxygen Desaturation

• Healthy individuals experience greater variation in oxygen saturation during sleep than while awake, with mean minimum saturation nadirs of 90.4% overall and 89.3% in those aged >60 years. 1
• In diseased states, this normal nocturnal dip is exaggerated, leading to clinically significant hypoxemia. 1
• REM sleep is particularly vulnerable, with minimal oxygen saturation occurring during this stage. 5

Prevention of Complications

• Nocturnal hypoxemia triggers hypoxia-induced pulmonary vasoconstriction, worsening preexistent pulmonary hypertension and right ventricular strain. 1
• Maintaining adequate oxygenation prevents activation of the renin-angiotensin system and reduces salt and water retention. 1
• In infants with CLDI, preventing hypoxemic episodes is the most effective means of preventing sudden infant death syndrome. 1

Assessment and Monitoring Requirements

Diagnostic Evaluation

• Pulse oximetry is the primary method for assessing oxygen levels, with multiple determinations during rest, sleep, feeding, and high activity. 1, 6
• Chronic hypoxemia in infants is defined as ≥5% of recording time with SpO2 ≤93% on continuous recording, or at least three separate findings of SpO2 ≤93% on intermittent measurements. 1
• Overnight pulse oximetry should include at least 8 hours of sleep for reliable prediction of oxygen needs. 1
• Polysomnography is recommended when obstructive sleep apnea is suspected or when symptoms suggest upper airway obstruction. 1

Target Oxygen Saturation Levels

• For most adults with chronic lung disease: maintain SpO2 ≥90% during sleep. 1
• For infants and children with PAH: maintain SpO2 ≥92% during sleep. 1
• For infants with CLDI/BPD past the age of oxygen-induced retinopathy risk: maintain SpO2 ≥95%. 1
• For general adult oxygen therapy: target range of 94-98% achieves normal or near-normal saturation for most adults. 1

Important Clinical Caveats

When Nocturnal Oxygen May Not Be Indicated

• COPD patients with moderate resting hypoxemia (SaO2 89-93%) or isolated exercise desaturation without severe resting hypoxemia do not benefit from supplemental oxygen in terms of survival, hospitalizations, or quality of life. 1, 3
• The ongoing International Nocturnal Oxygen (INOX) Trial is investigating whether nocturnal oxygen for COPD patients with isolated nocturnal desaturation affects mortality. 1

Monitoring for Adequate Treatment

• Approximately one-third of COPD patients on LTOT require increased oxygen flow during sleep beyond daytime requirements, confirmed by overnight pulse oximetry. 2
• If right ventricular hypertrophy persists or oxygen weaning is slow, screen for undertreatment during sleep, poor compliance, congenital cardiac defects, upper airway obstruction, or chronic aspiration with gastroesophageal reflux. 1
• Low-flow oxygen at 2 L/min improves oxygenation and prolongs sleep in COPD patients without adversely affecting sleep-disordered breathing or causing clinically significant CO2 retention. 7