Noninvasive positive pressure ventilation reduces need for mechanical ventilation and mortality in COPD exacerbations or cardiogenic pulmonary edema.
Decreases work of breathing and improves gas exchange.
Observational studies with noninvasive ventilation and acute hypoxia respiratory failure indicate a treatment failure rate as high as 50%.
Data does not support use of noninvasive positive pressure ventilation in hypercapneic acute hypoxemic respiratory failure.
Lowers the risk of nosocomial infections when compared to mechanical ventilation.
The ventilatory mode of choice in selected patients with respiratory failure caused by COPD.
For patients who are spontaneously breathing with acute respiratory failure,noninvasive positive pressure ventilation with a tight fitting facemask reduces morbidity and mortality in patients with acute respiratory failure caused by exacerbation of COPD.
Noninvasive ventilation is a value in some patients with hypoxemia from cardiogenic pulmonary edema.
Bronchiectasis and cystic fibrosis may lead to acute hypercapnic respiratory failure (AHRF), and NIV may be used similarly as for COPD.
In people with chest wall deformity or neuromuscular disease, NIV may be used if the CO2 level is elevated.
In neuromuscular disease, the vital capacity is used to determine a need for breathing support.
Obesity hypoventilation syndrome (OHS) may cause acute hypercapnic respiratory failure.
NIV use in acute cardiogenic pulmonary edema caused by decompensated heart failure, has shown a reduced risk of death and a decreased need for tracheal intubation.
Acute severe asthma may cause acute hypercapnic respiratory failure.
Whether NIV is effective in this situation, is not clear: NIV is only used in an intensive care unit setting where further deterioration can be managed immediately.
With chronic asthma and fixed airways disease that resembles COPD, NIV may be used.
NIV may be used in respiratory failure that may develop after major surgery.
NIV may be used during the recovery period.
NIV may be used to prevent recurrence of mechanical ventilation on the intensive care unit.
If respiratory failure does develop, recommencement of mechanical ventilation is recommended over NIV.
In patients ventilated for hypercapnic respiratory failure, NIV may be used to facilitate the weaning process.
Chronic use of NIV may be indicated for severe COPD.
Home NIV may also be indicated in people with neuromuscular disease and chest wall deformity.
People with motor neuron disease (MND) may require home NIV.
This is the same as non-invasive positive pressure ventilation(NPPV or NIPPV).
Postoperative respiratory failure is a common indication for invasive mechanical ventilation and accounts for more than 20% of all patients receiving ventilatory support.
To facilitate early extubation and prevent postoperative respiratory failure noninvasive ventilation with positive pressure is utilized to reduce the work of breathing, increase and expiratory lung volume and improve oxygenation.
The use of noninvasive continuous positive airway pressure following abdominal surgery reduces postoperative pulmonary complications, including the need for reintubation.
In patients following lung resection the use of NIV with inspiratory pressure assist decreased re intubation rates by half versus usual care with supplemental oxygen, chest physiotherapy and bronchodilators alone.
In mechanically ventilated patients at high risk of extubation failure, the use of high flow nasal oxygen with non-invasive ventilation immediately after excavation significantly decreases the risk of re-intubation compared with high flow nasal oxygen alone.
Noninvasive Respiratory Support for Adults with Acute Respiratory Failure
Invasive mechanical ventilation, particularly positive-pressure ventilation, has been the cornerstone of the management of severe forms of acute respiratory failure.
To reduce the complications and mortality associated with intubation and positive-pressure ventilation the use of noninvasive devices have
been advocated.
Noninvasive respiratory support is highly beneficial for cardiogenic pulmonary edema and chronic obstructive pulmonary disease (COPD) exacerbations.
The three main methods of noninvasive support are used in the acute care setting: a high flow of gas delivered through a large-bore nonocclusive nasal cannula, that is high-flow nasal cannula, continuous positive airway pressure (CPAP), and noninvasive ventilation, pressure-support ventilation with positive end-expiratory pressure [PEEP]).
Respiratory failure has two main components: ventilatory dysfunction and hypoxemia.
Ventilatory dysfunction causes dyspnea, increased work of breathing, use of accessory muscles, and hypercapnia, and is best treated by methods of ventilatory support.
Hypoxemia suggests inadequate gas exchange and warrants oxygen therapy and positive pressures to improve gas exchange.
Ventilatory dysfunction and hypoxemia are often combined due to injuries/diseases that cause abnormal gas exchange resulting in abnormal breathing mechanics.
Ventilatory dysfunction and hypoxemia
can also be dissociated, and require different respiratory support efforts.
High-Flow Nasal Cannula with
high gas flow rates (≥30 liters per minute and up to 60 to 80 liters per minute) with a set fraction of inspired oxygen (Fio2) of 0.21 to 1.0 can be administered through a nasal cannula.
By heating the nasal gas flow to 34° to 37°C, and with humidification to make gas delivery comfortable, (the high flow, usually higher than the patient’s own inspiratory peak flow) , allows for the effective delivery of the intended Fio2.
High flows also generate a small level of nonadjustable PEEP, that is slightly higher when the mouth is kept closed.
High flow reduces ventilation requirements and inspiratory muscle effort through a washout of the dead space in the upper airway during expiration.
High flow allows fresh gas with a con- trolled Fio2 to be available at the beginning of each inspiration, thereby slightly reducing the quantity of ventilation that needs to be generated by the patient to clear carbon dioxide.
The use of a high-flow nasal cannula is often associated with a prolonged expiration through a resistive effect that reduces the respiratory rate.
High flow may also assist in mucociliary clearance of secretions through humidified gas.
High flow is easy to apply, and generally causes minimal discomfort.
With CPAP, the patient breathes with a constant level of positive pressure that is maintained during both inspiration and expiration.
CPAP may be deployed with intensive care mechanical ventilators or with continuous-flow open circuits.
CPAP can also be delivered through open-to-atmosphere valves that have internal microchannels through which a jet of oxygen is delivered.
PEEP in the form of CPAP or noninva- sive ventilation can be very effective in relieving respiratory distress in patients with cardiogenic pulmonary edema by improving both cardiac and respiratory function.
Noninvasive ventilation is a patient-triggered, pressure-targeted mode of ventilation in which positive inspiratory pressure is delivered above a PEEP level at each patient-triggered breath.
The inspiratory pressure directly in- creases the tidal volume by raising the pressure gradient between the mouth and the alveoli, reducing the required effort to breathe.
Hypoventilation and respiratory acidosis situations are best treated with noninvasive ventilation by substantially reducing the work of breathing.
By decreasing the work of breathing, it also decreases oxygen consumption and improves gas exchange.
In patients with hypoxemic respiratory failure, the effect of positive inspiratory pressure needs to be monitored to ensure that it does not lead to excessive tidal volumes
The most commonly used patient interface for CPAP and noninvasive ventilation is the oronasal face mask.
The oronasal face mask covers the nose and the mouth and is secured with head straps.
Leakage of gas around the mask limits the efficacy of the device, and makes monitoring of the tidal volume less precise.
Total face masks, exert no direct pressure on the nose, can be used with less skin breakdown, and their efficacy is similar to that of masks with lower internal volumes.
The helmet is a larger interface for the delivery of CPAP or noninvasive ventilation.
The helmet allows for more prolonged use of CPAP or noninvasive ventilation than does the oronasal face mask.
Acute hypoxemic respiratory failure is often characterized by a combination of lung inflammation or infection, pulmonary edema, and atelectasis resulting in impaired oxygenation, ventilation, and respiratory mechanics.
Invasive mechanical ventilation, delivered with targeted pressures and volumes to prevent ventilator-induced lung injury, is used in the context of worsening gas exchange and high effort to breathe.
Invasive mechanical ventilation often involves heavy sedation.
Noninvasive respiratory support may facilitate gas ex- change while maintaining wakefulness and spontaneous breathing.
The spontaneous generation of negative intrathoracic pressures can have beneficial effects on gas exchange and the distribution of ventilation.
Noninvasive respiratory support is used frequently with the hope of reducing the need for intubation.
The greatest benefit of preemptive use of noninvasive ventilation in the context of acute hypoxemic respiratory failure
is seen in selected high-risk patients with obesity or cardiac conditions.
In the context of extubation after surgery, no benefit has been found for preemptive use of continuous positive airway pressure after abdominal surgery; however, a potential benefit of preemptive use of a high-flow nasal cannula has been found in this context in higher-risk patients and patients with hypoxemia.
A benefit of rescue noninvasive ventilation after abdominal surgery has also been found.
Studies suggest a lower risk of intubation and lower 90-day mortality with the use of a helmet than with the use of a face mask for noninvasive ventilation.
Patients in the helmet group have less discomfort from noninvasive ventilation at higher PEEP values than patients in a face-mask group.
All non- invasive respiratory support devices potentially decrease the risk of endotracheal intubation more effectively than conventional oxygen therapy, among patients with mild-to-moderate respiratory failure and in the absence of severe organ failure or shock.
Evidence for a benefit of noninvasive respiratory support for more severe forms of respiratory failure is less clear, with some data suggesting potential risks associated with face-mask noninvasive ventilation.
Uncertainties regarding whether to use noninvasive respiratory support, which device to use, the risk factors associated with failure, and how to monitor for failure in patients with higher severities of hypoxemia.
With cardiogenic pulmonary edema, noninvasive respiratory support strategies are used as bridging therapy during hypoxemia and respiratory distress while urgent medical therapies of diuretics and vasodilators are used.
Noninvasive respiratory support decreases the work of breathing, increases functional residual capacity, and enhancescardiac function.
CPAP and noninvasive ventilation with a face mask in patients with cardiogenic pulmonary edema show a reduced risk of endo- tracheal intubation and reduced in-hospital mortality associated with these methods.
When patients present with both hypoxemia and hypercapnia, it is advisable to use noninvasive ventilation as a first choice.
Noninvasive ventilation with a face mask has been very effective in the context of COPD exacerbations.
Use face-mask NIV for COPD, OHS, or congestive heart failure exacerbation.
Intubation for the presence acute hypoxemic respiratory failure is considered in the absence of an underlying chronic condition in patients with high severity of illness, shock, acute kidney injury, decreased level of consciousness, or severe hypoxemia.
Consider trial of high flow nasal cannula oxygen or trial of CPAP or NIV for acute hypoxemic respiratory failure in the absence of an underlying chronic conditionin patients with mild or moderate hypoxemia.
Pao2:Fio2 <150 with presence of ARDS indicates high risk of face-mask NIV failure and death.
Pao2:Fio2 <200 1 hr after initiation of face-mask NIV, particularly in the context of large tidal volumes (>9 to 9.5 ml/kg),27,28 indicates high risk of face- mask NIV failure.
Evidence suggests benefits of re- duced risk of intubation with helmet NIV as compared with face-mask NIV and HFNC in patients with moderate hypoxemic respiratory failure.
Helmet NIV may consider its use in patients with moderate hypoxemia, particularly in the presence of high work of breathing.
A series of randomized, controlled trials have evaluated the effectiveness of face-mask noninvasive ventilation as compared with conventional oxygen therapy for COPD exacerbations.
Face- mask noninvasive ventilation consistently showed success in preventing intubation and decreasing hospital mortality among these patients.
Non- invasive ventilation is strongly recommended as the first-line therapy for this population.
Insufficient evidence surrounding the role of a high-flow nasal cannula for COPD exacerbations.
Patients with obesity hypoventilation and mixed forms of respiratory failure may also benefit from both the PEEP and the driving pressure of noninvasive ventilation.
12 to 20% of patients may be determined to need reintubation within the week after extubation with noninvasive therapy compared with conventional oxygen therapy.
The use of noninvasive ventilation or a high-flow nasal cannula immediately after extubation has been successful in prevent- ing reintubation in certain high-risk populations, such as patients with COPD, coexisting cardiac conditions, or obesity.
Application of noninvasive ventilation in combination with a high-flow nasal cannula in patients who were at risk for being reintubated was associated with a lower risk of reintubation and postextubation respiratory failure at day 7 than the use of a high-flow nasal can- nula alone.
Lower risks of reintubation and death in the intensive care unit by day 7 associated with noninvasive ventilation than with a high-flow nasal cannula among patients with obesity
but not among patients of normal or lower-than-normal body weight.
The application of noninvasive respiratory support as a rescue maneuver in the context of postextubation acute respiratory failure has not shown great success.
The use of face-mask non- invasive ventilation in this context has been as- sociated with delayed intubation and increased mortality.
These findings may not be generalizable to patients with COPD exacerbations or cardiogenic pulmonary edema, since the trials of rescue noninvasive ventilation have predominantly involved patients with pneumonia.
The application of preemptive CPAP was not shown to decrease a composite of pneumonia, endotracheal intubation, or death within 30 days after postoperative extubation in a recent large, randomized trial involving patients undergoing abdominal surgery.
In a meta-analysis of 11 trials, preemptive use of a high-flow nasal cannula decreased the risk of intubation more effectively than conventional oxygen therapy.
CPAP and noninvasive ventilation have been effective in decreasing the incidence of reintubation and complications in patients who have postextubation hypoxemia after abdominal surgery.
Failure of noninvasive respiratory support is noted in only 15 to 20% of COPD exacerbations but in up to 40 to 60% of cases of acute hypoxemic respiratory failure.
The decision to use noninvasive methods in patients with brain or circulatory dysfunction should be made very cautiously, ex- cept when the dysfunction can be reversed by noninvasive ventilatory support.
Noninvasive ventilation failure has been found to be an independent risk factor for death in the ICU in patients with hypoxemic respiratory failure.
Helmet noninvasive ventilation as compared with a high-flow nasal cannula, in patients with a low partial pressure of arterial carbon dioxide (Paco2) (<35 mm Hg) derived the greatest benefit from helmet noninvasive ventilation with respect to a decreased risk of intubation.
This effect was not seen among patients with a normal or higher Paco2 (≥35 mm Hg).
A low or decreasing respiratory rate associated with greater likelihood of NIV success.
Continued large intrathoracic pressure swings and large tidal volumes, ultimately lead to excessive work of breathing, oxygen consumption, cardiac overload, or patient self-inflicted lung injury.