WHAT THESE STUDIES ADD:

• Noninvasive ventilation has been shown to be appropriate and beneficial for patients with severe hypoxemic respiratory failure caused by pneumonia and for those with hypercapnic cardiogenic pulmonary edema.

BARCELONA—In patients with respiratory failure, noninvasive ventilation (NIV) has recently been considered as an alternative to mechanical ventilation, under the rationale that avoiding intubation will lessen the incidence of complications and poor outcomes. Two European studies have evaluated NIV—in the ICU and in the emergency department—and found that successful use of NIV depends on both careful patient selection and the familiarity of physicians and nurses with the procedure.

EXPERIENCE IN THE ICU

Researchers from Spain conducted a prospective, randomized, controlled study in three ICUs; included were 105 consecutive patients with severe acute hypoxemic respiratory failure.[1] Hypoxemia was defined as an arterial oxygen tension or saturation that remained low for more than six to eight hours. Within 24 hours of being admitted to the ICU, patients received either:
• NIV (via a face or nasal mask) using bilevel positive airway pressure and ventilator specifically designed for NIV, or
• Conventional oxygen therapy, administered at high concentrations.

There were 51 patients in the NIV group and 54 in the control group. Compared with the control group, the NIV patients had a lower intubation rate (25% vs 52%). Additionally, the probability of not requiring mechanical ventilation over time was greater in the NIV group.

Hospital and ICU lengths of stay did not differ between groups. However, the incidence of septic shock was markedly lower in the NIV patients. Furthermore, ICU mortality was lower and probability of 90-day survival higher in the NIV group.

Both forms of treatment alleviated arterial hypoxemia and slowed the respiratory rate. However, the benefits achieved were markedly greater in the NIV group than in the controls.

The benefits of NIV were most noticeable in the patients with pneumonia; in this group, NIV clearly lowered the intubation rate and ICU mortality. In contrast, NIV had no effect on either variable in the patients with ARDS.

Considering reasons for NIV’s overall effectiveness, the authors speculated that delaying intubation by using NIV may allow severely ill patients time to respond to treatment of their underlying disease, thus improving their clinical condition, lowering their risk of respiratory failure, and increasing their rate of survival. The authors acknowledged that the success of NIV depends on patient selection, the experience of physicians and nurses in using NIV, and the type of ventilator used.

EMERGENCY DEPARTMENT NIV

Investigators from Italy found that NIV does not affect clinical outcomes in most patients with cardiogenic pulmonary edema, although it does benefit patients with hypercapnia.[2] They conducted a multicenter, randomized, prospective study in emergency departments and compared NIV with standard oxygen therapy in patients with acute cardiogenic pulmonary edema.

The investigators set out to judge the feasibility of NIV outside of the ICU and to observe any effect on mortality, intubation rates, and physiological variables. They also examined the use of NIV in hypercapnia.

One hundred thirty consecutive patients with cardiogenic pulmonary edema were recruited from five emergency departments. Each treatment group had 65 patients. At the end of the study, there were no between-group differences in the need for intubation or in hospital mortality. However, after 30 minutes of treatment, the patients given NIV had a significantly higher PaO2/FiO2 ratio than did the controls, and this difference persisted for at least three hours. In addition, the respiratory rate, dyspnea score, blood pressure, and heart rate improved more rapidly from baseline in the NIV group.

Subgroup analysis suggested that the effects of NIV were influenced by the extent of hypercapnia. When the authors examined the subgroup of patients with a PaCO2 above 45 mm Hg, they found that the percentage of patients needing intubation was significantly lower among those treated with NIV than among the controls. There was also a trend to decreased mortality in the NIV group. No differences in outcome were seen among those with PaCO2 levels below that threshold.

Stefano Nava, MD, Chief of the Respiratory Unit at Fondazione S. Maugeri, Istituto Scientifico di Pavia, in Pavia, Italy, said that despite the lack of overall effect on clinical outcomes, NIV improved healing time and dyspnea. He also offered an important insight for the apparent lack of efficacy of NIV in patients with a PaCO2 below 45 mm Hg: In this study, only a small number of nonhypercapnic patients needed to be intubated for respiratory reasons—mainly because most of them had already been intubated for cardiovascular reasons.

When administering NIV outside of the ICU, Dr. Nava explained, “the most important thing is to select the appropriate patients. For instance, in hypercapnic respiratory failure, that would be patients with a pH less than 7.39.”

According to Dr. Nava, NIV should be used “first line in hypercapnic respiratory failure—with the exclusion of coma and respiratory arrest. There are also good indications for its use in pulmonary edema, in immunocompromised patients, and in those with postsurgical complications.” In other situations, he added, caution is needed.

—Gale Jurasek

References
1. Ferrer M, Esquinas A, Leon M, et al. Noninvasive ventilation in severe hypoxemic respiratory failure. A randomized clinical trial. Am J Respir Crit Care Med. 2003;168:1438-1444.
2. Nava S, Carbone G, DiBattista N, et al. Noninvasive ventilation in cardiogenic pulmonary edema. A multicenter randomized trial. Am J Respir Crit Care Med. 2003;168:1432-1437.

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