Incidence and causes of non-invasive mechanical ventilation failure after initial success

Abstract

Background-The rate of failure of noninvasive mechanical ventilation (NIMV) in patients with chronic obstructive pulmonary disease (COPD) with acute respiratory insuYciency ranges from 5% to 40%. Most of the studies report an incidence of "late failure" (after >48 hours of NIMV) of about 10-20%. The recognition of this subset of patients is critical because prolonged application of NIMV may unduly delay the time of intubation. Methods-In this multicentre study the primary aims were to assess the rate of "late NIMV failure" and possible associated predictive factors; secondary aims of the study were evaluation of the best ventilatory strategy in this subset of patients and their outcomes in and out of hospital. The study was performed in two respiratory intensive care units (ICUs) on patients with COPD admitted with an episode of hypercapnic respiratory failure (mean (SD) pH 7.23 (0.07), PaCO 2 85.3 (15.8) mm Hg). Results-One hundred and thirty seven patients initially responded to NIMV in terms of objective (arterial blood gas tensions) and subjective improvement. After 8.4 (2.8) days of NIMV 31 patients (23%; 95% confidence interval (CI) 18 to 33) experienced a new episode of acute respiratory failure while still ventilated. The occurrence of "late NIMV failure" was significantly associated with functional limitations (ADL scale) before admission to the respiratory ICU, the presence of medical complications (particularly hyperglycaemia), and a lower pH on admission. Depending on their willingness or not to be intubated, the patients received invasive ventilation (n=19) or "more aggressive" (more hours/day) NIMV (n=12). Eleven (92%) of those in this latter subgroup died while in the respiratory ICU compared with 10 (53%) of the patients receiving invasive ventilation. The overall 90 day mortality was 21% and, after discharge from hospital, was similar in the "late NIMV failure" group and in patients who did not experience a second episode of acute respiratory failure.Conclusions-The chance of COPD patients with acute respiratory failure having a second episode of acute respiratory failure after an initial (first 48 hours) successful response to NIMV is about 20%. This event is more likely to occur in patients with more severe functional and clinical disease who have more complications at the time of admission to the ICU. These patients have a very poor inhospital prognosis, especially if NIMV is continued rather than prompt initiation of invasive ventilation.

Nasal high flow therapy: a novel treatment rather than a more expensive oxygen device

“…within 48 h of NHF initiation) was associated with lower overall ICU mortality, better extubation success and more ventilator-free days than late intubation when patients had received NHF therapy that failed [29]. The 48 h time frame is in accordance with that of MORETTI et al [28], who recorded particularly high mortality (67.7%) in patients with NIV failure who were intubated after the aforementioned time. Some significant factors could have influenced the results of this study [29].…”

“…A question that is raised in cases of NHF failure in immunocompromised patients is the delay of optimal treatment initiation, which could further increase the mortality rates in this group of patients at very high risk of death, as shown with NIV failure in the general population [28]. To date, only one study has shown that NHF failure was not associated with higher mortality rates [74], but undoubtedly, further studies are needed to clarify the safe time frame of NHF application as well as the specific indications of NHF oxygen delivery in immunocompromised patients.…”

“…As with NIV [28], there is a great concern about the optimum duration of NHF use. The potential masking of any respiratory deterioration may increase mortality due to delayed intubation [29].…”

High flow oxygen cannula: the other side of the moon

“…These results fit with a recent cohort study of patients with severe acute respiratory failure in which after only 6 h of HFNC, nonresponders had significantly worse hypoxemia and increased oxygen requirements, suggesting objective exclusion criteria and that the decision to intubate can be anticipated within 6 h of an HFNC trial [9]. These results also remind us of the reports on non-invasive mechanical ventilation (NIV) that showed many years ago that NIV failure could be strongly associated with higher mortality in such patients [10], inasmuch as NIV failure occurred late [11]. However, the study by Kang et al [8] does not tell us that HFNC should not be used in acute hypoxemic acute respiratory failure.…”

Effect of varying the pressurisation rate during noninvasive pressure support ventilation

“…However, these results are only achieved if NIV is set properly and the patient9s acceptance and tolerance of the procedure are optimal. Several clinical studies have reported that lack of compliance to ventilation is one of the major causes of failure in both acute hypercapnic and pure hypoxic respiratory failure [26][27][28].…”