Is Non-Invasive Ventilation (NIV) support indicated for a patient with chronic pulmonary thromboembolism and myelofibrosis who is deteriorating and unable to maintain adequate oxygen saturation (SpO2) on a non-rebreather mask (NRM)?

NIV Support in Chronic Pulmonary Thromboembolism with Myelofibrosis

Direct Recommendation

NIV support should be attempted as a therapeutic trial in this deteriorating patient, but only in an HDU/ICU setting with immediate availability of invasive mechanical ventilation, given the high likelihood of NIV failure in severe hypoxemic respiratory failure. 1

Clinical Context and Decision Framework

This patient presents with hypoxemic respiratory failure (Type 1) rather than hypercapnic failure, as evidenced by inability to maintain SpO2 on non-rebreather mask. 2 The underlying chronic pulmonary thromboembolism creates significant V/Q mismatch and shunting, while myelofibrosis may contribute to pulmonary complications. 2

Key Considerations for NIV Trial

Location and Monitoring Requirements:

• This patient must be managed in HDU or ICU, not on a general ward. 1
• Many patients with severe hypoxemia resistant to high-flow oxygen will require intubation, and trials of NIV in this context should only occur in HDU/ICU settings. 1
• Patients should be monitored continuously with pulse oximetry for at least 24 hours after commencing NIV. 1, 3

Realistic Expectations:

• NIV has limited efficacy in pure hypoxemic respiratory failure compared to hypercapnic failure. 1, 4
• The evidence for NIV in severe hypoxemia is less conclusive than for conditions like COPD with hypercapnia. 4
• High-flow nasal oxygen (HFNC) may be superior to conventional NIV for de novo acute hypoxemic respiratory failure, with significant mortality reduction. 1, 2

Assessment Timeline and Failure Criteria

Initial Assessment (1-2 hours):

• Measure arterial blood gases after 1-2 hours of NIV to assess response. 1, 3
• Clinical evaluation should include patient comfort, conscious level, chest wall motion, accessory muscle recruitment, respiratory rate, and heart rate. 1
• Target oxygen saturation of 94-98% (not 88-92%, as this patient does not have hypercapnic risk). 1, 3

Reassessment (4-6 hours):

• If there has been no improvement in oxygenation and clinical status after 4-6 hours, NIV should be discontinued and invasive ventilation considered. 1
• Failure to recognize lack of improvement during noninvasive support may result in further respiratory deterioration and/or cardiac arrest, often with devastating consequences. 1

Critical Warning Signs of NIV Failure

Immediate intubation indicated if:

• Deteriorating conscious level 1
• Respiratory arrest or peri-arrest (unless rapid recovery with manual ventilation/NIV) 1
• Persistent or worsening hypoxemia despite optimal NIV settings 1
• Development of complications such as pneumothorax 1
• Tidal volumes persistently >9.5 ml/kg predicted body weight suggest need for intubation 1
• Rapid shallow breathing index (RSBI) >105 breaths/min/L may be associated with need for intubation 1

Technical Optimization Before Declaring Failure

Before abandoning NIV, verify:

• Optimal medical treatment of underlying condition is prescribed and given 1
• Mask fit is adequate with minimal leakage 1, 3
• Circuit is set up correctly without leaks 1
• FiO2 is appropriate (not excessive oxygen causing harm) 1
• Patient is synchronizing with the ventilator 1
• Consider helmet interface if available, which may reduce intubation rates compared to face mask in ARDS 1

Alternative: High-Flow Nasal Oxygen

Consider HFNC as alternative to conventional NIV:

• HFNC was associated with significantly lower intubation rates than standard oxygen or NIV in patients with PaO2/FiO2 ≤200 mmHg. 1
• HFNC generates low levels of PEEP, decreases work of breathing, and reduces dead space. 1
• May be better tolerated than face mask NIV in severe hypoxemic failure. 1, 5

Common Pitfalls to Avoid

• Delaying intubation when NIV is clearly failing increases mortality in acute respiratory failure. 1
• Using NIV on general ward for severe hypoxemic failure without ICU backup is inappropriate and dangerous. 1
• Continuing NIV beyond 4-6 hours without improvement in gas exchange or clinical status. 1
• Excessive oxygen administration without monitoring—maintain PaO2 70-90 mmHg or SaO2 92-97%. 1
• Inadequate sedation monitoring—if sedation is used, it should only be in HDU/ICU setting with close monitoring. 3

Ceiling of Care Decision

A decision about tracheal intubation should be made BEFORE commencing NIV in every patient. 1 This should be verified with senior medical staff and documented in case notes. 1 If invasive mechanical ventilation is not appropriate for this patient (given chronic conditions and prognosis), then NIV represents the ceiling of treatment, and goals of care should be clearly established. 1