One of the most exciting roles of the respiratory therapist that has emerged over the last decade or two is that of delivering noninvasive ventilation (NIV) to the patient in acute respiratory failure (ARF). In fact, NIV is now considered to be the standard of care for those patients suffering from acute-to-chronic respiratory failure. Why is this particularly exciting for the respiratory therapist? It is now a well-known fact that the successful implementation of noninvasive ventilation requires a somewhat cooperative patient, an appropriate ventilating device with a comfortable interface, and a skilled practitioner to work with the patient and to make the necessary adjustments to both settings and interface. To do this successfully requires a high level of expertise, as well as the compassion and patience to work closely with the patient, helping them understand the purpose and goals of the therapy.1

Who Benefits?

Numerous prospective, randomized controlled trials regarding NIV provide evidence of the benefits associated with its use in patients experiencing hypercapnic respiratory failure associated with an exacerbation of chronic obstructive pulmonary disease (COPD).2-5 Several of the benefits cited include a decreased rate of intubation, reduction in mortality, reduced length of stay in the intensive care unit (ICU), and reduction in the length of hospital stay. In addition to evidence that patients with acute respiratory failure due to COPD benefit from NIV, there is evidence to support the use of NIV in some patients suffering from cardiogenic pulmonary edema.6,7

Another area where positive results have been experienced is with immunocompromised patients in the early stages of acute respiratory failure. In one particular trial,8 researchers hypothesized that the early initiation of NIV, used intermittently as signs of hypoxemic respiratory failure began, might lead to a reduction in the number of patients requiring endotracheal intubation and associated complications. They looked at a group of 52 immunosuppressed patients, randomizing half to a standard therapy group and the remainder to a NIV group. The results of the study were consistent with the investigators’ original hypothesis: Less than half of the NIV group required intubation, compared to greater than 75% in the standard treatment group; the number of complications experienced by the patients studied was significantly less in the NIV group; and the mortality rate was approximately 30% lower in the NIV patients. It is important to note that NIV was instituted early, prior to patients developing severe respiratory failure.

Who Doesn’t?

There are additional areas in which the evidence supporting the use of NIV is less convincing, however. According to recent conference proceedings conducted by the American Association for Respiratory Care,9 there are several conditions—including acute severe asthma, acute lung injury and acute respiratory distress syndrome, extubation failure, pneumonia, and ARF in patients who have declared themselves as “do not intubate” (DNI)—where the evidence for NIV is weak or findings are conflicting.

In a recent systematic review looking at the use of NIV in severe asthma events, published by The Cochrane Library,10 out of 696 abstracts that produced 11 trials, all but one of the trials was excluded. In the one included trial involving 30 patients, those presenting to the emergency department (ED) were randomized to either a NIV group or a group receiving usual medical care alone. The results showed that the NIV group appeared to benefit more in terms of improvements in hospitalization rate, number of discharges from the ED, and also percent predicted in FEV1, FVC, PEFR, and respiratory rate. The authors of this study concluded that although the preliminary results appear promising, larger randomized controlled trials need to be performed in an effort to determine if there is a role for NIV in status asthmaticus patients.11

Recent research supports the use of NIV as a successful tool to facilitate weaning from invasive mechanical ventilation, both for removing patients from mechanical ventilation sooner and for providing support for patients who ultimately fail extubation. NIV may be a reasonable alternative for patients who are at risk of failing extubation, or for patients who do not meet all of the typical requirements for extubation.

The Downside to Invasive Ventilation

Although invasive mechanical ventilation (MV) is a highly effective lifesaving procedure, it has the potential for producing many undesirable side effects. Invasive mechanical ventilation has been associated with ventilator-acquired pneumonia (VAP), resulting in associated high mortality rate, sinusitis, longer stays in the ICU, lengthy hospital stays, and higher overall costs.12-14

In a multicenter, randomized trial by Nava et al,15 a group of COPD patients with acute hypercapnic respiratory failure who were intubated for 48 hours were put on a spontaneous breathing trial (SBT). Patients who failed the weaning attempt were randomized either to receive NIV by face mask following extubation or to remain intubated and continue receiving invasive mechanical ventilation. A follow-up of these patients 60 days later showed that the patients who received NIV had a shorter weaning time, reduced time in the intensive care unit, reduced incidence of nosocomial pneumonia, and improved survival rates (see Table).

As alluded to previously, decreasing the potential complications associated with prolonged intubation with the earlier removal of the endotracheal tube has been a topic of significant interest. An extensive review of the evidence related to the topic of NIV and weaning identified five studies that were considered to be of moderate to good quality. Of these studies, NIV was shown to reduce mortality, decrease the incidence of VAP, decrease the length of stay in the ICU, reduce the length of stay in the hospital, decrease the total duration of mechanical ventilatory support, and reduce the duration of endotracheal intubation.16

What about ALI/ARDS?

The benefits of using NIV to treat patients with acute hypoxemic respiratory failure have been unclear, particularly for those patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS). In an observational study, outcomes of patients with ALI who were treated with NIV were evaluated. Of 54 patients who were analyzed in the study, approximately 70% failed NIV. Although patients who showed improvement in their oxygenation status with NIV tended to have better outcomes, this was not found to have significance.17

According to Garpestad and Hill,18 when considering what patients to select for a NIV trial, it may be best to exclude those patients with multisystem organ failure, or those who are uncooperative, do not have the ability to protect their airway, or have problems with excessive secretions. The authors also recommend that when NIV is attempted with ALI/ARDS patients, it should be done so in the intensive care unit where they can be closely monitored, and if oxygenation fails to improve within 1 to 2 hours of initiating NIV, the patient should be intubated.

There continue to be conflicting opinions on the effectiveness of using noninvasive ventilation with pneumonia. Some studies suggest that pneumonia is considered a significant risk factor for NIV failure.19 There was, however, a study performed in Spain that suggested that NIV is effective in treating patients with acute hypoxemic respiratory failure who have more severe oxygenation problems in the presence of pneumonia.20

NIV in Transport

When caring for individuals receiving NIV, as well as those with invasive MV, intrahospital transport of the patient can be a particular challenge. Transport of the intubated and mechanically ventilated patient can be performed using a standard resuscitator bag connected to a portable oxygen source, or using a portable mechanical ventilator. Some institutions have begun using the patient’s critical care ventilator for transports within the hospital. This minimizes the need to disconnect the patient from the ventilator, thus maintaining a closed ventilating circuit. Until recently, this has been more problematic for the patient receiving NIV; noninvasive systems frequently lacked a reasonable battery source to permit such use.

Ventilator technology has improved significantly in both the invasive and noninvasive markets though, and now there are options to purchase noninvasive ventilating devices that possess adequate battery systems designed for patient transport. In addition to these options, most modern ventilators now have software options available for ventilating a patient noninvasively as well as invasively. Most of these devices also have adequate battery systems installed or available to allow the clinician to use the same device for both the ICU and transport.

In summary, the effectiveness of using noninvasive ventilation is well established for patients experiencing an acute exacerbation of COPD, for patients with cardiogenic pulmonary edema, and for immunosuppressed patients who develop ARF; and it is, in fact, considered to be standard of care for treating such patients. Further studies need to be done with other patient subgroups—such as patients with acute severe asthma, those with community- or hospital-acquired pneumonia, and patients who develop ALI/ARDS. The knowledge and skills of the respiratory therapist will continue to play a significant role in the successful application of noninvasive ventilation, and may also make major contributions to research that still remains to be accomplished.


Paul Nuccio, MS, RRT, is director of pulmonary services, Brigham and Women’s Hospital, Boston. For further information, contact [email protected]

References

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