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380 PART 4: Pulmonary Disorders

abnormalities in respiratory mechanics despite a high stimulation of university referral hospital, it was found that NIPPV use increased grad-
the respiratory centers. This can be modified by NIPPV, which allows ually, in lockstep with a decline in conventional treatment with ETI.
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the patient to take larger volumes with less effort, thus reversing the In parallel with this gradual increase in NIPPV use, the nosocomial
clinical abnormalities resulting from hypoxemia, hypercapnia, and infection and mortality rates have significantly diminished.
acidosis. 49,55 At baseline, the transdiaphragmatic pressure generated Attention should be paid when using NIPPV in the most severely
by these patients can be considerably higher than normal and rep- affected patients, such as those with an arterial pH <7.30 on admission,
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resents a high percentage of their maximal diaphragmatic force, a especially outside the ICU, if the staff is not experienced in NIPPV appli-
situation that carries a major risk of respiratory muscle fatigue. 49,56,57 cation and not aware of its limitations. A very low pH, marked mental sta-
The main role of NIPPV is to offer the patient a way to increase the tus alterations at NIPPV initiation, presence of comorbidities, and a high
tidal volume at a lower work level. The use of ventilatory modalities severity score are associated with early NIPPV failure or late secondary
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working in synchrony with the patient’s efforts allows larger breaths failure after an initial improvement. Several of these factors seem to
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https://kat.cr/user/tahir99/
to be taken with less effort. As a result of the increased alveolar ven- indicate that a longer time from onset of the exacerbation to NIPPV ini-
) and pH val- tiation may reduce the likelihood of success. Every effort should be made
tilation, arterial partial carbon dioxide pressure (Pa CO 2
ues improve, and this in turn reduces the patient’s ventilatory drive, to deliver NIPPV early, and close monitoring is in order when NIPPV is
thereby lowering the respiratory rate and improving the dyspnea. started late, a situation where NIPPV is less effective. 71
Some controversies exist concerning the use of NIPPV to treat
Clinical Evidence: An international consensus conference published patients with hypercapnic encephalopathy due to ARF associated with
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in 2001 has recommended that NIPPV should be considered as a first- COPD exacerbation. Several observational studies showed positive
line treatment in patients with acute COPD exacerbation and, more clinical results 72,73 ; however, caution might be taken when applying
recently, different national guidelines advocated this practice. 59,60 NIPPV in patients with altered level of consciousness. Close monitor-
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The Global Initiative for Chronic Obstructive Lung Disease (GOLD) ing is mandatory and any delay in consciousness improvement should
in 2013, reinforced the importance of NIPPV when treating COPD be interpreted as NIPPV failure and lead to prompt intubation.
exacerbations with a high level of evidence (Evidence A) based on The need for invasive MV after NIPPV failure in acute COPD exac-
its considerable rate of success (80%–85%) in this clinical situation. 61 erbations represents a challenging context and this subgroup of patients
The first evidence that NIPPV markedly reduced the need for ETI has a relatively high mortality rate and a greater length of hospital stay,
came from case-control series reported in 1990. Subsequently, several as shown in a large observational study. Patients requiring invasive
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prospective randomized trials confirmed that NIPPV reduced the need MV after NIPPV failure had 61% greater odds of death compared with
for ETI and the rate of complications, shortened the length of stay, and patients directly placed on invasive MV (95% CI, 24%-109%) and 677%
improved survival in patients with COPD. 50,52,53,62-65 Studies conducted greater odds of death compared with a patient treated with NIPPV suc-
in the United Kingdom established that NIPPV was also effective in cess without transition to invasive MV (95% CI, 475%-948%).
non-ICU settings. 50,65 In the largest ICU study reported to date, Brochard In conclusion, NIPPV offers many advantages over invasive MV to
and colleagues randomized 85 patients with COPD to treatment with treat exacerbations of COPD and there is strong evidence that NIPPV is
or without face mask pressure-support ventilation. The ETI rate was cost effective, being both more efficient and cheaper compared to stan-
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74% in the controls given standard medical treatment and 26% in the dard therapy alone during the treatment of these group of patients. 75,76
NIPPV group. Benefits in the NIPPV group included a decreased rate of
complications during the ICU stay, a shorter length of hospital stay and, Long-Term Survival: A few studies have suggested that NIPPV use
more importantly, a significant reduction in mortality (from 29% to 9%). may be associated with higher 1-year survival rates, as compared
The overall decrease in mortality was ascribable to reductions in the to standard ICU therapy or invasive MV. 71,77-79 Although these stud-
need for ETI and in various ICU-related complications. In the United ies have a number of methodological flaws, the consistency of their
Kingdom, Plant and colleagues conducted a prospective multicenter results suggests an interesting benefit of NIPPV. Some authors argue
randomized trial comparing standard therapy alone (control group) to for continuing home NIPPV after exacerbations. One of the benefits
NIPPV in 236 COPD patients admitted to general respiratory wards for could be a reduction of the readmission rate, as suggested in one small
ARF. Treatment failure (defined as fulfillment of criteria for ARF) was randomized controlled trial. 80,81
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more common in the control group (27%) than in the NIPPV group Other Forms of Chronic Respiratory Failure: All forms of acute-on-
(15%), and NIPPV was associated with a lower in-hospital mortality chronic ventilatory failure share several common pathophysiologic
rate. Because of admission policies in the United Kingdom, patients who pathways, although major differences also exist. NIPPV may be
failed NIPPV were not routinely transferred to the ICU. slightly less effective in patients with chronic restrictive lung dis-
These studies made clear that early NIPPV to prevent further deterio- ease than in patients with COPD in the acute phase, but it remains
ration need to be an important component of the first-line therapy for an interesting option to propose, especially when compliance is
COPD exacerbation. 66 still preserved. 82
A recent database analyzed 7,511,267 admissions for acute exacerba-
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tions of COPD in the United States from 1998 to 2008, of which 612,650 Negative Pressure Ventilation: This technique is available in very few
(8.1%) required respiratory support. The authors showed an increase centers in the world. In acute exacerbations of COPD, it seems to
in the use of NIPPV (from 1.0% to 4.5% of all admissions) and a 42% provide better outcomes than conventional invasive MV and may be
decline in invasive MV (from 6.0% to 3.5% of all admissions). Intubation similar to face mask NIPPV. 83-85
and in-hospital mortality have declined during this period. By 2008, Location: During the last decade, health care providers became
NIPPV was used more frequently than invasive MV as the first-line increasingly confident in applying NIPPV, since, contrasting with
therapy for acute exacerbations of COPD. invasive MV, it can be realized outside the ICU, freeing up ICU beds.
Whether the results of randomized controlled trials entirely apply to The study by Plant and associates cited above was performed in respi-
everyday ICU practice must be evaluated. This is particularly important ratory wards, where the staff received 8 hours of training over the
with NIPPV, since there is a learning curve, as shown at least in two 3 months preceding the study. 65
studies. In a single-center study by Carlucci and colleagues, the NIPPV The feasibility of treating patients with COPD out of the ICU has been
success rate remained stable over the study period, but the patients demonstrated, but an appropriate training of the ward staff is necessary.
treated with NIPPV during the last few years of the study period had NIPPV usage will probably continue to increase outside the ICU in the
levels and lower pH values. coming years, since now NIPPV is largely available in several medical
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more severe disease with higher Pa CO 2
In fact, progressively, more severe exacerbations could be treated with services. Hence, some hospitals have created special nursing units to
NIPPV out of the ICU. In an 8-year study performed in a French assist NIPPV delivery, located commonly next to the ICU. 86

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