Noninvasive Ventilation (NIV)

Noninvasive ventilation (NIV) is an advanced respiratory support that does not require an artificial, invasive airway. This technique is commonly used during acute respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure. The most common forms of NIV are noninvasive positive pressure ventilation (NIPPV) and high-flow nasal cannula (HFNC). In acute respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure, NIV is frequently used to prevent intubation for invasive mechanical ventilation, if there are no contraindications. There are more established contraindications to NIPPV in comparison to HFNC, but NIPPV has demonstrated clear mortality benefit in chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) and congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure exacerbations.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Indications

Definition

Noninvasive ventilation (NIV) is respiratory support that does not require an artificial, invasive airway (such as an endotracheal tube).

Types

  • Noninvasive positive pressure ventilation (NIPPV): 
    • Can be provided with: 
      • Continuous positive airway pressure (CPAP) 
      • Bilevel positive airway pressure (BiPAP).
    • Typically applied with a sealed face mask that covers both the nose Nose The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Anatomy of the Nose and the mouth. 
    • Can also be used in the form of a helmet
    • Positive airway pressure allows alveolar recruitment to participate in oxygenation. 
  • High-flow nasal cannula (HFNC):
    • Another form of NIV that uses high concentrations of oxygen, which may be delivered at up to 60 L/min via large-bore nasal cannula
    • At higher flow rates, HFNC generates positive end-expiratory pressure (PEEP) above the physiologic level.

Indications

The most common indication for use is acute respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure:

  • Ideally, for conscious patients with spontaneous breathing 
  • Moderate to severe hypoxemia or hypercapnia
  • Increased respiratory effort and tachypnea:
    • Accessory muscle use, pursed-lip breathing
    • Goal is to prevent fatigue.

Common conditions that may be suitable for NIV:

  • Acute hypoxic respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure
    • Infection/ pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma exacerbation
    • Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism
    • Atelectasis Atelectasis Atelectasis is the partial or complete collapse of a part of the lung. Atelectasis is almost always a secondary phenomenon from conditions causing bronchial obstruction, external compression, surfactant deficiency, or scarring. Atelectasis
    • Posttrauma
  • Acute hypercapnic respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure +/– acute hypoxic respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure:
    • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma or chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) ( COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)) exacerbation
    • Congestive heart failure ( CHF CHF Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure) exacerbation/ pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema
    • Hypoventilation from sedation
    • Progressive obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity hypoventilation syndrome
    • Progressive neuromuscular disorder
  • Note: Studies have shown a mortality benefit of NIPPV in COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) and CHF CHF Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure exacerbations.

Contraindications

While NIV may reduce the need for invasive mechanical ventilation and its associated complications, careful consideration for patient selection is essential to prevent harm. 

Common contraindications for NIPPV include:

  • Cardiac or respiratory arrest
  • Poor airway protection:
    • Increased secretions
    • Impaired coughing/swallowing
    • Altered mental status
  • Upper airway trauma/anatomical abnormality
  • Unstable hemodynamics 
  • Recent maxillofacial surgery
  • Uncontrollable vomiting
  • Patient refusal 

Contraindications for HFNC:

  • There are no clear absolute contraindications at this time, as few studies are available.
  • Potential contraindications include:
    • Facial anomalies preventing proper fit
    • After upper airway surgery

Noninvasive Positive Pressure Ventilation

Basic settings controlled by the operator

  • PEEP or expiratory positive airway pressure (EPAP): 
    • Pressure remaining in the distal airways at the end of expiration
    • Keeps the alveoli open to participate in oxygenation
    • Can be ↑ to improve oxygenation (↑ PaO2)
    • Can be lowered to ↓ oxygenation (↓ PaO2)
  • Inspiratory positive airway pressure (IPAP; for BiPAP): 
    • The amount of positive pressure delivered with each inspiration 
    • ↑ IPAP → ↑ tidal volume → ↑ ventilation → ↓ PaCO2
    • ↓ IPAP → ↓ tidal volume → ↓ ventilation → ↑ PaCO2  
    • Note: Changes in ventilation can occur only if EPAP is not changed in the same proportion.
  • Fraction of inspired oxygen (FiO2): 
    • Percentage of oxygen delivered directly to the individual 
    • ↑ FiO2 → ↑ oxygenation 
    • ↓ FiO2 → ↓ oxygenation
  • Note:
    • In CPAP: a constant PEEP is used → provides continuous positive pressure throughout the breathing cycle
    • In BiPAP: IPAP and EPAP are used → provides different pressures for inhalation and exhalation

Background physiology

  • Constant positive airway pressure → improves alveolar recruitment → improves hypoxemia
  • IPAP during inhalation, in addition to the set EPAP/PEEP, creates bilevel ventilation 
    • The pressure gradient between the IPAP and the EPAP correlates with the tidal volume delivered.
    • This relationship ultimately regulates CO2 clearance.
  • NIV can be used to:
    • Improve alveolar ventilation → improve hypercapnia and acidosis
    • Recruit alveoli and deliver ↑ FiO2 → help reverse hypoxia
      • Maintains open airway and prevents dynamic hyperinflation of alveoli
      • Improves ventilation/perfusion (V/Q) mismatch
    • Ameliorate respiratory distress/work of breathing
    • Reduce left ventricular preload and afterload:
      • Consequently, increasing right ventricular (RV) afterload and reducing RV preload
      • Can be beneficial in left-sided heart failure, but should be used with caution in right-sided heart failure

High-Flow Nasal Cannula

Basic settings controlled by the operator

There are 2 parameters that affect oxygenation:

  • Flow rate (generally optimized first to avoid FiO2 levels > 60%, when possible)
  • FiO2

Background physiology

  • HFNC delivers heated and humidified oxygen for the following physiologic effects:
    • Washes out CO2 from the anatomical dead space
    • Can generate a moderate level of PEEP → ↑ recruitment of collapsed alveoli 
    • Improved comfort (improves compliance) through: 
      • Humidification and warming of oxygen 
      • No mask
    • May have fewer hemodynamic effects than NIPPV
    • Can ↓ work of breathing
  • Best used in acute hypoxic respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure:
    • May have a role in mild or moderate hypercapnic respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure
    • May be able to prevent intubation in select individuals
    • Can be combined easily with inhaled vasodilators 
    • Sometimes use preintubation for oxygen delivery

Complications

The most feared complication for NIV is delaying a potentially lifesaving intervention because of poor patient selection. 

  • Intubation is not without risk, but it is often necessary in the critical care setting. 
  • Delaying intubation in a rapidly deteriorating individual may result in increased mortality.

Major complications for noninvasive positive pressure ventilation

  • Barotrauma (rare)
  • Pressure ulcers/necrosis of the nasal bridge (from the mask)
  • Claustrophobia or anxiety
  • Aspiration from vomiting
  • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension in right heart failure or hypovolemia 
  • Reduced communication

Major complication for high-flow nasal cannula

  • Epistaxis
  • Abdominal distention 
  • Aspiration
  • Barotrauma (rare, and lower risk than NIPPV and mechanical ventilation)

Weaning

Timing

There are no set guidelines on how to specifically wean, but can be considered when on minimal NIV settings:

  • Minimal BiPap settings are considered: 
    • IPAP, ≤ 10 mm Hg 
    • PEEP, 5 mm Hg
    • FiO2, ≤ 40%, with good oxygen saturations
    • Settings can be variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables and depend on comorbidities.
  • Minimal HFNC settings are considered: 
    • Flow, ≤ 20 L/min 
    • FiO2, ≤ 40%

Considerations before weaning

  • Was the underlying reason for use addressed, and is it resolving?
  • Has severe tachypnea resolved?
  • Is the individual on minimal NIV settings?
  • Is the SpO2 > 88%–92% or the PaO2 > 55‒60 mm Hg?
  • Has the individual’s mental status improved?

Weaning trial

Once weaned to minimal settings, a weaning trial can be attempted:

  • Remove individual from NIV and use nasal cannula and closely monitor for deterioration.
  • Individuals may be trailed off for about an hour → reassess respiratory status frequently thereafter

References

  1. Luecke, T., Pelosi, P. (2005). Clinical review: positive end-expiratory pressure and cardiac output. Critical Care 9:607. https://doi.org/10.1186/cc3877
  2. Nickson, C. (2019, September 14). Non-invasive ventilation (NIV). Life in the Fast Lane. https://litfl.com/non-invasive-ventilation-niv/
  3. Nishimura, M. (2015). High-flow nasal cannula oxygen therapy in adults. J Intens Care 3(1):15. https://doi.org/10.1186/s40560-015-0084-5
  4. Hackett, A.J. (2018). Non-Invasive ventilation in Critical CARE: Positive pressure ventilation AND High-flow oxygen therapy. PulmCCM. Retrieved December 12, 2021, from https://pulmccm.org/critical-care-review/non-invasive-ventilation-in-critical-care-positive-pressure-ventilation-and-high-flow-oxygen-therapy/
  5. Soo Hoo, G.W. (2020). Noninvasive ventilation. Medscape. Retrieved December 12, 2021, from https://emedicine.medscape.com/article/304235-overview#a1
  6. Hyzy, R.C. (2021). Heated and humidified high-flow nasal oxygen in adults: practical considerations and potential applications. UpToDate. Retrieved December 12, 2021, from https://www.uptodate.com/contents/heated-and-humidified-high-flow-nasal-oxygen-in-adults-practical-considerations-and-potential-applications#H1033389248
  7. Hyzy, R.C., McSparron, J.I. (2021). Noninvasive ventilation in adults with acute respiratory failure: benefits and contraindications. UpToDate. Retrieved December 12, 2021, from https://www.uptodate.com/contents/noninvasive-ventilation-in-adults-with-acute-respiratory-failure-benefits-and-contraindications
  8. Pinto, V.L., Sharma, S. (2021). Continuous positive airway pressure. StatPearls. Retrieved December 12, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK482178/

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