Non-invasive ventilation

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Non-invasive ventilation
BIPAP.JPG
The setup for non-invasive ventilation using a mechanical ventilator. Modern devices are often much smaller.
Other namesNon-invasive positive pressure ventilation (NIPPV), NIV, NPPV

Non-invasive ventilation (NIV) is the use of breathing support administered through a face mask, nasal mask, or a helmet. Air, usually with added oxygen, is given through the mask under positive pressure; generally the amount of pressure is alternated depending on whether someone is breathing in or out. It is termed "non-invasive" because it is delivered with a mask that is tightly fitted to the face or around the head, but without a need for tracheal intubation (a tube through the mouth into the windpipe). While there are similarities with regards to the interface, NIV is not the same as continuous positive airway pressure (CPAP), which applies a single level of positive airway pressure throughout the whole respiratory cycle; [1] CPAP does not deliver ventilation but is occasionally used in conditions also treated with NIV. [2]

Contents

Non-invasive ventilation is used in acute respiratory failure caused by a number of medical conditions, most prominently chronic obstructive pulmonary disease (COPD); numerous studies have shown that appropriate use of NIV reduces the need for invasive ventilation and its complications. Furthermore, it may be used on a long-term basis in people who cannot breathe independently as a result of a chronic condition.

Medical uses

NIV for acute respiratory failure is used particularly for severe exacerbations of chronic obstructive pulmonary disease (COPD) but also for acute decompensated heart failure and other acute conditions. [3] NIV can be used acutely and long-term. In some people who have presented with acute respiratory failure, there is an ongoing need for long-term use of NIV at home. [2]

Non-invasive ventilation has been suggested in the treatment for coronavirus disease 2019 (COVID-19) where shortages of invasive ventilation equipment and facilities may arise. [4] The risk of poorly fitting masks emitting aerosols can require full protection gear for caregivers. [5]

COPD

The most common indication for acute non-invasive ventilation is for acute exacerbation of chronic obstructive pulmonary disease. The decision to commence NIV, usually in the emergency department, depends on the initial response to medication (bronchodilators given by nebulizer) and the results of arterial blood gas tests. If after medical therapy the lungs remain unable to clear carbon dioxide from the bloodstream (respiratory acidosis), NIV may be indicated. Many people with COPD have chronically elevated CO2 levels with metabolic compensation, but NIV is only indicated if the CO2 is acutely increased to the point that the acidity levels of the blood are increased (pH<7.35). [6] There is no level of acidity above which NIV cannot be started, but more severe acidosis carries a higher risk that NIV alone is not effective and that mechanical ventilation will be required instead. [6]

Other causes of AHRF

Bronchiectasis may lead to acute hypercapnic respiratory failure (AHRF), and NIV may be used similarly as for COPD. [2] This is particularly the case where the underlying cause is cystic fibrosis. [2] Cystic fibrosis also causes high volumes of sputum (phlegm) which may require specialised physiotherapy assistance and sometimes the insertion of a mini-tracheostomy to clear this. [2]

In people with chest wall deformity or neuromuscular disease, NIV may be commenced if the CO2 level is elevated even if it has not yet caused acidosis. [2] In neuromuscular disease, a breathing measurement known as the vital capacity is used to determine a need for breathing support. [2]

Obesity hypoventilation syndrome (OHS) may cause acute hypercapnic respiratory failure. When this is the case, the criteria for commencing acute NIV are similar to those for COPD (decreased pH, elevated CO2), although there are some scenarios where NIV may be initiated in hospitalized people despite a normal pH; these include people with daytime somnolence, sleep-disordered breathing and/or evidence of right ventricle heart failure. [2]

In acute cardiogenic pulmonary oedema caused by decompensated heart failure, the quality of evidence is poor but studies have shown a reduced risk of death and a decreased need for tracheal intubation for both NIV and CPAP. [6] [7] Both CPAP and NIV may be used in the prehospital care setting. [6]

Acute severe asthma may cause AHRF, when it is labelled "near-fatal asthma". [8] There is limited evidence on whether NIV is effective in this situation, which carries a high risk of requiring mechanical ventilation. Professional guidelines therefore do not give a clear recommendation, [6] [8] and it is suggested that NIV is only used in an intensive care unit setting where further deterioration can be managed immediately, [8] or not at all. [2] Some people with chronic asthma develop fixed airways disease that resembles COPD, and NIV may be used in that setting. [2] [6]

Respiratory failure may develop after major surgery. NIV may be used in this setting during the recovery period. [6] In those who have undergone mechanical ventilation on the intensive care unit and are considered at high risk of recurrence, NIV may be used to prevent this. However, if respiratory failure does develop, recommencement of mechanical ventilation is recommended over NIV to treat this. [6] In those who were ventilated for hypercapnic respiratory failure, NIV may be used to facilitate the weaning process. [6]

Chronic/home use

Chronic use of NIV ("home NIV") may be indicated for severe COPD. [9]

Home NIV may also be indicated in people with neuromuscular disease and chest wall deformity. [2]

People with obesity hypoventilation syndrome often require NIV initially in their care, but many can be switched to CPAP. [2] American Thoracic Society (ATS) clinical practice guidelines recommend that NIV is provided on discharge with a further sleep study assessment as an outpatient. [10] With regards to initiation of positive pressure treatment, the ATS guidelines recommend that in people being investigated for possible obstructive sleep apnea (OSA, a related condition), measurement of arterial carbon dioxide (in high probability) or venous bicarbonate (in moderate probability) is performed to identify OHS and to determine an indication for treatment. In those with both severe OSA and OHS, initial treatment with CPAP is recommended although the quality of research supporting this over NIV is poor. [10] In the 30% of people with OHS who do not also have severe OSA, NIV may be more effective but is also more cost- and resource-intensive. [10] In those who have both OSA and OHS, poor response to CPAP despite good adherence may be an indication to switch to NIV. [11]

People with motor neuron disease (MND) may require home NIV in the course of their illness. Guidelines in the United Kingdom stipulate that assessment of respiratory function is part of the multidisciplinary management of MND. [12]

Terminology

A number of terms have been used in the medical literature to describe NIV. The more formal name "non-invasive positive pressure ventilation" (NPPV or NIPPV) has been used to distinguish it from the use of the now very rare negative pressure ventilator ("iron lung"). The brand name BiPAP/BIPAP (for Bilevel Positive Airway Pressure) has also enjoyed a degree of popularity, after an early NIV machine produced by Respironics, but its use is now discouraged. [13]

History

Non-invasive ventilation has been used since the 1940s for various indications, but its present-day use for chronic breathing problems arose in the 1980s for people with chronic respiratory muscle weakness, and in the 1990s on intensive care units and other acute care settings for acute respiratory failure. [13]

Since 2000 acute NIV has been used widely in the treatment of acute respiratory failure, particularly in people with COPD, including on general wards rather than the intensive care unit setting. In the United Kingdom, a 2017 report by NCEPOD found that there were widespread problems in the delivery of high-quality care to patients. [14]

Related Research Articles

Sleep apnea Disorder involving pauses in breathing during sleep

Sleep apnea, also spelled sleep apnoea, is a sleep disorder in which pauses in breathing or periods of shallow breathing during sleep occur more often than normal. Each pause can last for a few seconds to a few minutes and they happen many times a night. In the most common form, this follows loud snoring. There may be a choking or snorting sound as breathing resumes. Because the disorder disrupts normal sleep, those affected may experience sleepiness or feel tired during the day. In children, it may cause hyperactivity or problems in school.

Respironics is an American medical supply company that specializes in products that improve respiratory functions. It is based in the Pittsburgh suburb of Murrysville in Pennsylvania, United States.

Respiratory failure Inadequate gas exchange by the respiratory system

Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide or both cannot be kept at normal levels. A drop in the oxygen carried in blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be either acute or chronic. The definition of respiratory failure in clinical trials usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered mental status due to ischemia in the brain.

Shortness of breath Feeling of difficulty breathing

Shortness of breath (SOB), also known as dyspnea is a feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity", and recommends evaluating dyspnea by assessing the intensity of the distinct sensations, the degree of distress involved, and its burden or impact on activities of daily living. Distinct sensations include effort/work, chest tightness, and air hunger.

Obesity hypoventilation syndrome Condition in which severely overweight people fail to breathe rapidly or deeply enough

Obesity hypoventilation syndrome (OHS) is a condition in which severely overweight people fail to breathe rapidly or deeply enough, resulting in low oxygen levels and high blood carbon dioxide (CO2) levels. The syndrome is often associated with obstructive sleep apnea (OSA), which causes periods of absent or reduced breathing in sleep, resulting in many partial awakenings during the night and sleepiness during the day. The disease puts strain on the heart, which may lead to heart failure and leg swelling.

Positive airway pressure Mechanical ventilation in which airway pressure is always above atmospheric pressure

Positive airway pressure (PAP) is a mode of respiratory ventilation used in the treatment of sleep apnea. PAP ventilation is also commonly used for those who are critically ill in hospital with respiratory failure, in newborn infants (neonates), and for the prevention and treatment of atelectasis in patients with difficulty taking deep breaths. In these patients, PAP ventilation can prevent the need for tracheal intubation, or allow earlier extubation. Sometimes patients with neuromuscular diseases use this variety of ventilation as well. CPAP is an acronym for "continuous positive airway pressure", which was developed by Dr. George Gregory and colleagues in the neonatal intensive care unit at the University of California, San Francisco. A variation of the PAP system was developed by Professor Colin Sullivan at Royal Prince Alfred Hospital in Sydney, Australia, in 1981.

Hypercapnia Abnormally high tissue carbon dioxide levels

Hypercapnia (from the Greek hyper = "above" or "too much" and kapnos = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous product of the body's metabolism and is normally expelled through the lungs. Carbon dioxide may accumulate in any condition that causes hypoventilation, a reduction of alveolar ventilation (the clearance of air from the small sacs of the lung where gas exchange takes place). Inability of the lungs to clear carbon dioxide leads to respiratory acidosis. Eventually the body compensates for the raised acidity by retaining alkali in the kidneys, a process known as "metabolic compensation".

Respiratory acidosis Medical condition

Respiratory acidosis is a state in which decreased ventilation (hypoventilation) increases the concentration of carbon dioxide in the blood and decreases the blood's pH.

Respiratory disease Disease of the respiratory system

Respiratory diseases, or lung diseases, are pathological conditions affecting the organs and tissues that make gas exchange difficult in air-breathing animals. They include conditions of the respiratory tract including the trachea, bronchi, bronchioles, alveoli, pleurae, pleural cavity,the nerves and muscles of respiration. Respiratory diseases range from mild and self-limiting, such as the common cold, influenza, and pharyngitis to life-threatening diseases such as bacterial pneumonia, pulmonary embolism, tuberculosis, acute asthma, lung cancer, and severe acute respiratory syndromes, such as COVID-19. Respiratory diseases can be classified in many different ways, including by the organ or tissue involved, by the type and pattern of associated signs and symptoms, or by the cause of the disease.

Positive end-expiratory pressure (PEEP) is the pressure in the lungs above atmospheric pressure that exists at the end of expiration. The two types of PEEP are extrinsic PEEP and intrinsic PEEP. Pressure that is applied or increased during an inspiration is termed pressure support.

Alveolar lung disease Medical condition

Alveolar lung diseases, are a group of diseases that mainly affect the alveoli of the lungs.


Hypopnea is overly shallow breathing or an abnormally low respiratory rate. Hypopnea is defined by some to be less severe than apnea, while other researchers have discovered hypopnea to have a "similar if not indistinguishable impact" on the negative outcomes of sleep breathing disorders. In sleep clinics, obstructive sleep apnea syndrome or obstructive sleep apnea–hypopnea syndrome is normally diagnosed based on the frequent presence of apneas and/or hypopneas rather than differentiating between the two phenomena. Hypopnea is typically defined by a decreased amount of air movement into the lungs and can cause oxygen levels in the blood to drop. It commonly is due to partial obstruction of the upper airway.

Continuous positive airway pressure Form of ventilator which applies mild air pressure continuously to keep airways open

Continuous positive airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmospheric pressure is continuously applied to the upper respiratory tract of a person. The application of positive pressure may be intended to prevent upper airway collapse, as occurs in obstructive sleep apnea, or to reduce the work of breathing in conditions such as acute decompensated heart failure. CPAP therapy is highly effective for managing obstructive sleep apnea. Compliance and acceptance of use of CPAP therapy can be a limiting factor, with 8% of people stopping use after the first night and 50% within the first year.

Bronchitis Inflammation of the large airways in the lungs

Bronchitis is inflammation of the bronchi in the lungs that causes coughing. Symptoms include coughing up sputum, wheezing, shortness of breath, and chest pain. Bronchitis can be acute or chronic.

Pulmonary rehabilitation, also known as respiratory rehabilitation, is an important part of the management and health maintenance of people with chronic respiratory disease who remain symptomatic or continue to have decreased function despite standard medical treatment. It is a broad therapeutic concept. It is defined by the American Thoracic Society and the European Respiratory Society as an evidence-based, multidisciplinary, and comprehensive intervention for patients with chronic respiratory diseases who are symptomatic and often have decreased daily life activities. In general, pulmonary rehabilitation refers to a series of services that are administered to patients of respiratory disease and their families, typically to attempt to improve the quality of life for the patient. Pulmonary rehabilitation may be carried out in a variety of settings, depending on the patient's needs, and may or may not include pharmacologic intervention.

Acute exacerbation of chronic obstructive pulmonary disease Medical condition

An acute exacerbation of chronic obstructive pulmonary disease or acute exacerbations of chronic bronchitis (AECB), is a sudden worsening of chronic obstructive pulmonary disease (COPD) symptoms including shortness of breath, quantity and color of phlegm that typically lasts for several days.

Chronic obstructive pulmonary disease Lung disease involving long-term poor airflow

Chronic obstructive pulmonary disease (COPD) is a type of obstructive lung disease characterized by long-term breathing problems and poor airflow. The main symptoms include shortness of breath and cough with mucus production. COPD is a progressive disease, meaning it typically worsens over time. Eventually, everyday activities such as walking or dressing become difficult. Chronic bronchitis and emphysema are older terms used for different types of COPD. The term chronic bronchitis is still used to define a productive cough that is present for at least three months each year for two years. Those with such a cough are at a greater risk of developing COPD. The term emphysema is also used for the abnormal presence of air or other gas within tissues.

Heated humidified high-flow therapy

Heated humidified high-flow (HHHF) therapy, often also high flow nasal cannula(e) (HFNC) or high flow nasal oxygen (HFNO), is a type of respiratory support method that delivers a high flow of medical gas to a patient through an interface intended to create a wash-out of the upper airway. The applied gas is heated to best match human body temperature (37 °C) and humidified targeting ideal body saturation vapor pressure. It is used in acute and chronic breathing problems, and is a suitable choice for treatment of patients with severe or critical COVID-19.

Modes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. In general, mode selection is based on clinician familiarity and institutional preferences, since there is a paucity of evidence indicating that the mode affects clinical outcome. The most frequently used forms of volume-limited mechanical ventilation are intermittent mandatory ventilation (IMV) and continuous mandatory ventilation (CMV). There have been substantial changes in the nomenclature of mechanical ventilation over the years, but more recently it has become standardized by many respirology and pulmonology groups. Writing a mode is most proper in all capital letters with a dash between the control variable and the strategy.

Respiratory compromise describes a deterioration in respiratory function with a high likelihood of rapid progression to respiratory failure and death. Respiratory failure occurs when inadequate gas exchange by the respiratory system occurs, with a low oxygen level or a high carbon dioxide level.

References

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