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382 PART 4: Pulmonary Disorders

leakage, which would make NIPPV administration difficult and patient- Great care should be utilized when applying NIPPV to hypox-
ventilator synchrony poor. At the opposite, insufficient pressure may emic patients because of possible downsides of the technique. 20,113
translate into unsatisfactory inspiratory muscle unloading. Low PEEP An international survey evaluated NIPPV practice as a first-line
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levels can be insufficient to improve oxygenation, whereas high levels therapy in early ARDS patients. They found that a higher SAPS II and
of PEEP may promote adverse hemodynamic effects and limit the pres- Pa O 2 /Fi O 2 ≤175 mm Hg 1 hour after initiation of NPPV were indepen-
sure support level. In a physiologic study realized in 10 patients with dently associated with NIPPV failure. This survey showed that NIPPV
mild ARDS, L’Her and coworkers confirmed the limited efficacy of use avoided ETI in no more than 50% of patients even in experienced
116
CPAP alone in lessening the work of breathing. The addition of pressure centers highlighting that a low number of patients with more severe
support was necessary to reduce the neuromuscular drive, significantly forms of ARDS can be successfully treated with NIPPV (31%), and that
unload the inspiratory muscles and improve dyspnea, whereas effects on close monitoring is crucial when using this technique as a first-line
oxygenation were dependent on the PEEP level. therapy in patients with ARDS.
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Other studies, described very high rates of NIPPV failure in patients
Clinical Evidence with pneumonia and severe hypoxemia. 118,127-129 Several signals, there-
CPAP A clinical investigation published in 2000 evaluated whether face fore, indicate that NIPPV should be applied with caution in patients
mask CPAP produced physiologic benefits and reduced the need for with severe community-acquired pneumonia. If employed, this treat-
ETI in patients with acute hypoxemic nonhypercapnic respiratory insuf- ment should not delay intubation when clinical signs and symptoms
] warn for impending NIPPV failure. 130
ficiency (arterial oxygen tension/inspired oxygen fraction [Pa O 2 /Fi O 2
<300 mm Hg). Despite an early favorable physiologic response to In sum, which subgroup of hypoxemic patients will really benefit
113
CPAP in terms of comfort and oxygenation, no differences were found with NIPPV use with minimizing its potential risks is still a field for
in the need for ETI, in-hospital mortality, or length of ICU stay. In addi- investigation. The following categories of patients have been more spe-
tion, the use of CPAP was associated with a higher rate of complications cifically studied.
including stress ulcer bleeding and cardiac arrest at the time of ETI.
Therefore, CPAP alone cannot be recommended as a means of avoiding ■ SUBGROUPS
ETI in patients with mild to severe ARDS. Its use should be limited to a Immunocompromised Patients: In immunocompromised patients any
short initial period when no other method is available. intervention reducing the infection risk may significantly improve the
short-term prognosis. Therefore, as the decreased rate of infectious
PSV and PEEP Until the end of the 1990s, the most convincing successes 6,7,69
with NIPPV had been obtained in patients with acute respiratory acido- complications is one significant benefit of NIPPV, its use seems par-
8,120,122,124
sis in whom hypoxemia was not the main reason for respiratory failure. ticularly attractive in this population. Several trials have shown
An early randomized controlled trial by Wysocki and colleagues found major benefits of NIPPV as a preventive measure during episodes of
no benefit of NIPPV in patients with no previous history of chronic lung acute hypoxemic respiratory failure in solid organ- transplant patients
disease, except in the subgroup of patients who developed acute hyper- or in patients with severe immunosuppression, particularly related to
8,120,122
capnia. In the following years, NIPPV has been shown to be beneficial hematologic malignancies and neutropenia. Significant reduc-
117
in carefully selected patients with a variety of patterns of hypoxemic tions in ETI use, infectious complications, length of stay, and
respiratory failure, 8,64,114,115,118-121 reducing the need for ETI and improv- mortality occurred with NIPPV. Similarly, patients experiencing
ing outcomes. 120,122-124 Patient selection generally excluded patients who Pneumocystis carinii pneumonia during the course of HIV infection
have shock, neurologic disorders with a need for upper airway protec- seem to benefit from NIPPV, as suggested in a case-control study by
124
tion, respiratory arrest, a poor cooperation, or other concomitant organ Confalonieri and associates. In a study by Squadrone et al, patients
failure. In a randomized controlled study by Antonelli and coworkers, with hematological malignancy presenting early signs of respiratory
NIPPV using PSV and PEEP was highly beneficial and associated with dysfunction of noninfectious etiology were randomized while still
less adverse effects compared to conventional mechanical ventilation, in the hematology ward to receive either CPAP ventilation as a
<200 mm Hg). These patients were preventive measure or standard oxygen therapy. CPAP ventilation
in hypoxemic patients (Pa O 2 /Fi O 2 substantially decreased the ICU admission rate, the subsequent intu-
free from COPD, hemodynamic instability, or neurologic impairment,
and were randomized when they reached predefined criteria for ETI. bation rates, the hospital mortality, and hospital- and ICU-free days,
115
131
Improvements in oxygenation were similar with the noninvasive and as well as episodes of pneumonia and sepsis. Notwithstanding the
the invasive approach. Despite a 30% failure rate, patients treated with methodological limitations of this study (unblinded, small sample
NIPPV had overall shorter durations of ventilation and ICU stays and size, single center study), these results are promising and need confir-
experienced fewer complications. This study demonstrated that NIPPV mation in future trials.
could be effective in selected patients with hypoxemic respiratory failure In the immunocompromised population NIPPV failure is associated
132,133
without hemodynamic or mental impairment. Others randomized con- with a mortality of more than 70%. Careful patient selection and
trolled trials confirmed this beneficial effect. 114,121 The study by Ferrer early initiation of NIPPV are therefore of utmost importance for mini-
133
et al compared oxygen therapy versus NIPPV in 105 patients admitted to mizing the possibility of intubation and maximizing patients benefits.
121
failure due to community-acquired pneumonia, ARDS, CPE, or other dis- ■ PREOXYGENATION BEFORE INTUBATION
the ICUs of three hospitals for acute nonhypercapnic hypoxemic respiratory
eases. NIPPV use decreased the need for ETI (25% vs 52%), the incidence Baillard et al evaluated 53 patients who required ETI due to ARF
134
of septic shock, and the ICU mortality rate (18% vs 39%) and increased the and significant hypoxemia (Pa O 2 <100 mm Hg under a high Fi O 2 mask).
cumulative 90-day survival rate, indicating that NIPPV could be effective in The patients were allocated to 3 minutes preoxygenation, before ETI,
avoiding ETI and improving survival in hypoxemic situations. It is impor- performed by a nonrebreathing bag-valve mask (control group), or
tant to use the technique in cooperative patients without hemodynamic PSV and PEEP (NIPPV group) used as a preoxygenation method.
instability, major respiratory secretions, or other organ failures. Compared to the control group, the NIPPV group showed a statistically
A recent small prospective, multicenter, randomized controlled trial significant improvement in pulse oximetry and Pa O 2 levels and a lower
125
included 40 patients whose diagnosis was mild ARDS. Half of patients number of patients had a pulse oximetry (Sp O 2 ) below 80% during the
included had pulmonary infection as the reason for ARDS, and they were ETI procedure (7% vs 46%, respectively); in no patient NIV had to be
allocated either to PSV and PEEP ventilation (NIPPV group) or high- interrupted due to intolerance of this technique suggesting the safety of
concentration oxygen therapy (control group). Less patients required intu- this approach in this specific situation. A recent review considers that
135
bation and were intubated in the NIPPV group compared to control group NIPPV should be used for preoxygenation and ventilation in patients
and NIPPV use was associated with a lower number of organ failures. who cannot get Sp O 2 greater than 93% to 95% with high Fi O 2 .

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