How is acute hypoxic and hypercapnic respiratory failure managed?

Management of Acute Hypoxic and Hypercapnic Respiratory Failure

Initial Assessment and Immediate Actions

Before initiating any ventilatory support, you must make and document a clear decision about whether the patient is a candidate for endotracheal intubation if non-invasive ventilation (NIV) fails—this decision should be verified with senior staff and documented in the case notes before starting NIV. 1

Arterial Blood Gas Analysis

• Immediately measure arterial blood gases to assess severity of hypercapnia and acidosis 2
• Key thresholds for decision-making:
  • pH <7.35 with PaCO2 >45 mmHg: Indicates need for NIV after maximal medical treatment 1
  • pH <7.25 (H+ >56 nmol/l): These patients respond less well and should be managed in HDU/ICU 1
  • Life-threatening hypoxemia with high A-a gradient: More appropriately managed by tracheal intubation 1

Oxygen Therapy Strategy

• For hypercapnic patients, use controlled oxygen therapy targeting SpO2 88-92% with 24% or 28% Venturi mask or nasal cannulae at 1-2 L/min to avoid worsening hypercapnia and respiratory acidosis 2
• Recheck arterial blood gases after 30-60 minutes of oxygen therapy to monitor for worsening hypercapnia 2
• Never administer high-concentration oxygen in hypercapnic patients—this can worsen hypercapnia and respiratory acidosis 2
• Never suddenly discontinue oxygen therapy in hypercapnic patients as this can cause life-threatening rebound hypoxemia 2

Non-Invasive Ventilation (NIV) Implementation

Clear Indications for NIV

NIV should be initiated if respiratory acidosis (pH <7.35, H+ >45 nmol/l) persists despite maximal medical treatment and controlled oxygen therapy. 1, 3

Specific patient populations where NIV is indicated:

• COPD exacerbation with persistent respiratory acidosis: This is the strongest indication (Grade A evidence) 1, 3
• Acute or acute-on-chronic hypercapnic respiratory failure due to chest wall deformity or neuromuscular disease 1
• Decompensated obstructive sleep apnea with respiratory acidosis: Use bi-level pressure support 1
• Cardiogenic pulmonary edema unresponsive to CPAP: NIV should be reserved for CPAP failures 1

Location of Care Decision

• Patients with pH 7.30-7.35: Can be managed on respiratory ward with appropriate monitoring 1
• Patients with pH <7.30: Should be managed in HDU/ICU 1
• Hypoxemic respiratory failure (pneumonia, ARDS, asthma): Should only receive NIV in HDU/ICU where immediate intubation is available 1, 4

NIV Setup Protocol

Use a full-face mask initially in the acute setting, changing to nasal mask after 24 hours as the patient improves. 1

Step-by-step initiation 1:

1. Explain NIV to the patient
2. Select appropriately sized mask and familiarize patient by holding it in place
3. Set up ventilator with bi-level pressure support
4. Attach pulse oximeter
5. Commence NIV, holding mask in place for first few minutes
6. Secure mask with straps/headgear
7. Add supplemental oxygen if SpO2 <85% 1
8. Instruct patient how to remove mask and summon help

Monitoring and Reassessment

Check arterial blood gases at 1-2 hours after initiating NIV to assess response. 1, 2

Critical monitoring parameters 4, 2:

• Continuous pulse oximetry for at least 24 hours after commencing NIV
• Respiratory rate and heart rate
• Patient comfort and conscious level
• Chest wall motion and accessory muscle recruitment

NIV Failure Criteria and Escalation

If PaCO2 and pH have deteriorated after 1-2 hours of NIV on optimal settings, institute alternative management plan immediately. 1

If no improvement in PaCO2 and pH by 4-6 hours, discontinue NIV and consider invasive ventilation. 1, 4

Immediate intubation is required if 4:

• Deteriorating conscious level
• Respiratory arrest or peri-arrest
• Persistent or worsening hypoxemia despite optimal NIV settings
• Development of complications such as pneumothorax
• Tidal volumes persistently >9.5 ml/kg predicted body weight

Before Declaring NIV Failure

Verify the following technical aspects 4:

• Optimal medical treatment of underlying condition
• Adequate mask fit
• Correct circuit setup
• Appropriate FiO2
• Patient synchronization with ventilator

Specific Considerations for Hypoxemic vs Hypercapnic Failure

Hypercapnic Respiratory Failure (Type II)

NIV is the predominant and most effective treatment for hypercapnic respiratory failure with moderate quality evidence showing 46% reduction in mortality and 65% reduction in need for intubation. 3

• NIV reduces intubation rates, mortality, and duration of ICU/hospital stays, particularly with mild to moderate respiratory acidosis 5, 3
• For COPD patients, ventilator settings need long expiration and short inspiration time to avoid hyperinflation and increased intrinsic PEEP 6

Hypoxemic Respiratory Failure (Type I)

High-flow nasal oxygen may be superior to conventional NIV for de novo acute hypoxemic respiratory failure, with significant mortality reduction. 4

• CPAP improves oxygenation in patients with diffuse pneumonia who remain hypoxic despite maximal medical treatment 1
• Many patients with acute pneumonia and hypoxemia resistant to high flow oxygen will require intubation—trials of CPAP or NIV should only occur in HDU or ICU settings 1
• NIV should not be used routinely in acute asthma 1

Absolute Contraindications to NIV

Do not use NIV in the following situations 1:

• Recent facial or upper airway surgery
• Facial burns or trauma
• Fixed upper airway obstruction
• Active vomiting
• Recent upper gastrointestinal surgery
• Inability to protect airway
• Copious respiratory secretions

These contraindications can be overridden only if contingency plans for intubation are in place or if a decision has been made not to proceed to invasive ventilation. 1

Critical Pitfalls to Avoid

The most dangerous error is delaying intubation when NIV is clearly failing—failure to recognize lack of improvement during noninvasive support may result in respiratory deterioration and/or cardiac arrest. 4, 2

Other common errors 4, 2:

• Using NIV on general ward for severe hypoxemic failure without ICU backup
• Continuing NIV beyond 4-6 hours without improvement
• Excessive oxygen administration in hypercapnic patients
• Inadequate sedation monitoring
• Failing to recognize that twitching may indicate worsening neurological status requiring more aggressive intervention

Adjunctive Pharmacological Management

For agitated or distressed patients with twitching and tachypnea, consider intravenous morphine 2.5-5 mg to provide symptom relief and improve NIV tolerance. 2

• When using nebulized bronchodilators, use ultrasonic or jet nebulizer driven by compressed air with supplementary oxygen via nasal cannulae to maintain 88-92% saturation 2

Service Organization Requirements

Facilities for NIV should be available 24 hours per day in all hospitals admitting patients with acute respiratory failure. 7

• Trained ICU staff, doctors, physiotherapists, or nurses can successfully set up and maintain NIV 1
• When setting up an acute NIV service, it is recommended that NIV be initiated and run by nursing staff 1
• Clear protocols should exist for on-call medical staff regarding indications, initiation, and supervision responsibility 1
• All patients started on NIV should be transferred to respiratory physician care as soon as possible 1