Noninvasive Positive-Pressure Ventilation for Respiratory Failure

NPPV is growing in popularity as a preferred treatment for patients with acute respiratory failure, especially those with hypercapnic respiratory failure.

Noninvasive ventilation has been defined as “the provision of ventilatory support through the patient’s upper airway using a mask or similar device.”1 Noninvasive positive-pressure ventilation (NPPV) can refer to the application of support using dedicated noninvasive interfaces. There are many different interfaces used in the application of NPPV; these include, but are not limited to, nasal masks, nasal pillows, oronasal (full-face) masks, total face masks, mouthpieces, and over-the-head hood or helmet devices.2 Specific headgear connects each type of interface to the patient.3 Although NPPV has been used to treat obstructive sleep apnea,4 it is also an important treatment for acute and chronic respiratory failure.

In the hospital setting, NPPV was first applied to patients experiencing acute exacerbations of chronic obstructive pulmonary disease (COPD).5 Most of the prospective, randomized controlled trials have been performed with this patient population. NPPV support for patients with acute respiratory failure has increased in recent years. Although NPPV may benefit patients with hypoxic respiratory failure, individuals with hypercapnic respiratory failure are likely to gain most from its use.

There have been a number of prospective, randomized controlled trials6-8 of NPPV that provide evidence of its benefits in treating hypercapnic respiratory failure associated with COPD exacerbation. Of the benefits cited, most noteworthy were a 66% decrease in the intubation rate, a reduced mortality rate, and shorter hospital and intensive care unit stays. In one retrospective study9 that examined a group of patients with hypercapnic exacerbations of COPD, individuals who responded to NPPV had significantly lower prognostic scores than those who ultimately required endotracheal intubation. Although the response to therapy cannot always be predicted, NPPV does appear to be beneficial for this particular patient population; therefore, its routine use for the hypercapnic patient during acute COPD exacerbation may be appropriate.10

In one randomized, controlled trial,11 it was hypothesized that the use of NPPV would reduce mortality and improve outcomes for COPD patients hospitalized with ventilatory failure. Patients who were randomized to the NPPV group received ventilatory support for less than 16 hours per day. Patients receiving NPPV had reduced levels of dyspnea, as well as improved arterial blood gas (ABG) results. This study demonstrated that the use of NPPV in this patient population is tolerated well, can reduce dyspnea, and can improve ABG levels.

Traditionally, the ventilatory management of patients in acute respiratory failure has been primarily accomplished through the use of endotracheal intubation. The adverse effects sometimes associated with this invasive technique have been well documented in the literature.12,13 These negative effects include ventilator-associated pneumonia, oral trauma, tracheoesophageal fistula, tracheal stenosis, and many other problems. An effort to minimize the many complications associated with invasive mechanical ventilation has led to the increased popularity of NPPV in recent years.

Cost is another reason to consider using NPPV (rather than conventional invasive ventilation) in selected patients. One study14 demonstrated a cost benefit of $3,244 per patient admission for NPPV, compared with standard therapy. These results were based on higher incidences of ventilator-acquired pneumonia, as well as prolonged mechanical ventilation, in those undergoing endotracheal intubation.

Avoiding intubation is an important objective in the treatment of patients with respiratory failure, particularly in those who are immunosuppressed. These patients typically exhibit poor outcomes, and this population has extremely high mortality rates. In one study15 of patients who required mechanical ventilation following bone-marrow transplantation, the mortality rate was close to 95%. Pneumonia and sepsis, along with other complications associated with endotracheal intubation and mechanical ventilation, play important roles in morbidity and mortality in this patient population.

Hilbert et al16 hypothesized that NPPV, initiated early and used intermittently as hypoxemic respiratory failure began, might lead to a reduction in the number of patients requiring endotracheal intubation and a decrease in associated complications. They looked at a group of 52 immunosuppressed patients, randomizing half to a standard-therapy group and the remainder to an NPPV group. The results of their study supported their original hypothesis. Less than half of the NPPV group required intubation, compared with more than 75% of the standard treatment group. The number of complications experienced were significantly fewer in the NPPV group, and mortality was approximately 30% less in the NPPV patients. It is important to note that NPPV was instituted early, prior to the development of severe respiratory failure. The importance of appropriate patient selection, combined with early intervention, cannot be overemphasized.

This patient group, in particular, may benefit from the establishment of an NPPV team composed of RCPs with exceptional NPPV skills. This team, which might also be helpful to NPPV patients in other categories, would be consulted every time a potential candidate was identified, based on a predetermined set of criteria (Table 1, page 22), by the nursing or medical staff. Once notified, the NPPV team would assess the patient and review inclusion and exclusion criteria for appropriateness. If the patient was determined to meet the criteria, NPPV would immediately be instituted by an RCP. The NPPV team, working closely with the pulmonary service, would monitor the patient’s status daily.

Entry Criteria/Indications Exclusion Criteria/Contraindications
Absolute polymorphonuclear leukocyte
count <1,000 cells per cubic millimeter
of blood
Requirement for emergency intubation for:
• Cardiopulmonary resuscitation
• Respiratory arrest
• Rapid deterioration in neurological status
Clinical history of pulmonary infiltrates and fever as evidenced by:
• Temperature >38.30°C
• Chest radiography finding of persistent
pulmonary infiltrates
• Deterioration in pulmonary gas exchange
Hemodynamic instability:
• Systolic blood pressure <80 mm Hg
• Evidence on electrocardiogram of ischemia
• Clinically significant ventricular arrhythmias
Signs of dyspnea at rest Chronic obstructive pulmonary disease
(according to American Thoracic Society criteria
Respiratory rate >30 breaths per minute Uncorrected bleeding diathesis
PaO2:FIO2 <200 with supplemental oxygen administration Tracheotomy, facial deformity, or recent history of oral, esophageal, or gastric surgery
Table 1. Patient selection criteria for noninvasive positive-pressure ventilation; FIO2=fraction of inspired oxygen. Adapted from N Engl J Med.16

The successful use of NPPV relies, to a great degree, on the skill of the RCPs involved in its administration. An increased amount of staff time is also required to work with the NPPV patient, particularly during the first 8 hours of NPPV use.8 Frequent communication, coaching, and encouragement by the clinician during the early stages of use are critical to achieving success. It is usually advisable to begin ventilation with minimal pressure, holding the mask in place during the early minutes of NPPV use. Permitting the patient to hold the mask, if feasible, for a few moments may help accustom him or her to the treatment. Periodic removal of the mask, when possible, may also lead to better patient tolerance.

The interface used plays an important role in the acceptance of NPPV by the patient. If an oronasal mask or nasal mask is used, choosing a device of the appropriate size and shape will increase potential success. The interface must be chosen based on the size and shape of the patient’s face. A one-size-fits-all approach should be avoided. The facial features of every patient are unique; therefore, the interface should be individualized. A mask that is too large or too small will lead to increased leaking, facial breakdown, and poor patient tolerance. Providing a cushion or barrier for the forehead and bridge of the nose may minimize nasal and facial sores caused by the pressure of the mask and straps. This protection should be applied prior to attaching the mask to the patient’s face.17 Patient comfort is one of the most important determinants of whether the intervention will be successful, so the additional time that it takes to choose a proper interface may lead to improved patient compliance.

The delivery of NPPV provides exciting opportunities for the respiratory clinician. RCPs are highly skilled providers of mechanical ventilatory support, and the use of NPPV presents a challenge for even the best of professionals. Noninvasive ventilation has evolved tremendously over recent years and has become an increasingly important adjunct to the care of the patient in acute or chronic respiratory failure. The appropriate use of noninvasive ventilation may result in positive patient outcomes, better patient tolerance, and improved comfort.17

Case Study
In December 2002, a 59-year-old male patient was admitted to a hospital in the Northeast U.S. with a preliminary diagnosis of acute respiratory failure/insufficiency secondary to COPD, lung cancer, and pneumonia. His clinical presentation included signs of acute respiratory distress (Table 2).

• Severe dyspnea
• Tachypnea (38 breaths per minute)
• Increased use of accessory muscles
• Abdominal paradox
Table 2. Patient’s symptoms of acute respiratory distress

Initial ABG analysis revealed acute respiratory acidosis with partial renal compensation. The patient had a pH of 7.21, a Paco2 of 85 mm Hg, a Pao2 of 109 mm Hg, a pulse-oximetry result (Spo2) of 100%, and a fraction of inspired oxygen (Fio2) of 100% delivered via nonrebreathing mask. A decision was initially made to intubate the patient and institute mechanical ventilatory support, but the patient’s level of alertness prompted an attempt to provide NPPV.

After a full-face mask of the appropriate size had been chosen, NPPV was initiated using a critical care ventilator. The use of NPPV was explained to the patient by the RCP, who then began ventilation using the pressure-support ventilation (PSV) mode. Initial settings included PSV of 15 cm H2O with positive end-expiratory pressure (PEEP) set at 2.5 cm H2O. The patient quickly became dyssynchronous with the NPPV due to a significant mask leak. The leak resulted in difficulty terminating the inspiratory portion of each breath. Following initial attempts to reposition the mask for a better seal, the RCP changed the mode of ventilation to pressure-control ventilation (PCV). The use of PCV allowed the therapist to set a specific inspiratory time, thus solving the dyssynchrony problem. The patient became very comfortable on PCV with an inspiratory pressure of 15 cm H2O, a set inspiratory time of 0.8 seconds, and a PEEP of 2.5 cm H2O. The Fio2 was reduced to 50%.

Approximately 1 hour following the institution of NPPV, the patient appeared comfortable with a respiratory rate of 14. Follow-up testing indicated a pH of 7.38, a Paco2 of 54 mm Hg, a Pao2 of 131 mm Hg, an Spo2 of 100%, and an Fio2 of 50%. The patient’s blood pressure and heart rate were within normal limits. NPPV was applied continuously during the first 8 hours, with a fairly rapid reduction in Fio2 followed by intermittent NPPV treatment over the next 2 days. NPPV was ultimately discontinued on the third day, with the patient requiring low-level supplemental oxygen. A chest radiograph performed on the third day demonstrated resolving pneumonia.

This case not only demonstrates the successful application of NPPV with avoidance of endotracheal intubation, but also shows the importance of the RCP’s skills in finding solutions that result in success.

Paul Nuccio, RRT, FAARC, is director of respiratory care, Brigham and Women’s Hospital, Boston.

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