Systematic review
Effect of long-term mechanical ventilation (LTMV) part 2 – thoracic restrictive disorders or adipositas hypoventilation syndrome
Systematic review
|Updated
The Norwegian Directorate of Health requested the Norwegian Knowledge Centre for Health Services to review the effects of LTMV. In response we have prepared and are publishing three consecutive reports to address this question. This is the second report in the series in which we review the effects of LTMV for patients with obesity hypoventilation syndrome (OHS) and for patients with chest wall diseases.
Key message
Background
Patients who fail to maintain adequate respiration by themselves may need long-term mechanical ventilation (LTMV) for shorter or longer consecutive time periods. Patients who need LTMV are heterogeneous with respect to age, diagnosis and the progression of their disease. Recent Norwegian data also suggests considerable regional differences in the indication for initiation of LTMV.
Commission
The Norwegian Directorate of Health requested the Norwegian Knowledge Centre for Health Services to review the effects of LTMV. In response we have prepared and are publishing three consecutive reports to address this question. This is the second report in the series in which we review the effects of LTMV for patients with obesity hypoventilation syndrome (OHS) and for patients with chest wall diseases.
Main findings
Obesity hypoventilation syndrom (OHS)
- We did not identify studies of the effect of LTMV and patient survival.
- LTMV-treatment may be associated with a decrease in the number of hospital admittances and improvements in some parameters related to quality of life and sleep. However, the quality of the evidence is very low and it is not possible to draw clear conclusions about the effectiveness of LTMV.
Chest wall disease (CWD)
- LTMV may be associated with increased survival compared to LTOT (Long Term Oxygen Treatment) alone, but the quality of the evidence is low and any conclusion is uncertain.
- LTMV may be associated with fewer hospital admissions and improvements in some parameters related to quality of life and sleep. However, the quality of the evidence is very low and it is not possible to draw any clear conclusions based on the available evidence.
Summary
Background
Patients with a variety of disorders may require long-term mechanical ventilation (LTMV). The potential users are heterogeneous in terms of diagnosis (pathophysiology), age, and prognosis. Recent Norwegian data show that children with 40 different diagnoses are registered users of LTMV, with spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD) being the most common. Among adult LTMV-users, the most frequent diagnoses are stable chronic obstructive pulmonary disease (COPD), obesity hypoventilation syndrome (OHS), amyotrophic lateral sclerosis (ALS) and sequelae of poliomyelitis.
The need for LTMV is in some cases obvious. For example, a comprehensive spinal cord injury located in the upper part of the neck will affect the central respiratory center as well as respiratory muscles, and round-the-clock use of respirator is necessary to maintain breathing. In other cases, patients are only in need for ventilator support some hours each day, for example during the night. The medical indications underlying initiation of LTMV are unclear, and recent Norwegian data shows substantial regional variations in when LTMV is being used.
We have summarized the existing scientific evidence about the effects of LTMV for patients with neuromuscular disease, central respiratory failure, chest wall disorders, obesity hypoventilation syndrome (OHS) and chronic obstructive pulmonary disease (COPD). The current report comprises evidence for effectiveness of LTMV for patients with obesity hypoventilation syndrome and for patients with chest wall disorders.
Methods
We searched for systematic reviews and primary studies in MEDLINE, EMBASE, SVEMED, Pedro, Cochrane Library, DARE, and ISI Web of Science. Two people screened titles and abstracts independently, and selected systematic reviews and primary studies for inclusion. We assessed methodological quality of included systematic reviews using a locally developed checklist, whereas primary studies were critically appraised according to the risk of bias domains.
We categorized included trials with respect to various diagnostic groups, and extracted relevant data. The overall quality of the documentation was considered for the four primary outcomes: survival, quality of life, hospitalization and sleep using the GRADE instrument. Results were combined in a meta-analysis when possible and deemed appropriate.
Result
We included 33 studies about the use of LTMV among patients with obesity hypoventilation syndrome and patients with chest wall disease. Most included studies are observational studies without a control group, but we also included two randomized controlled trials and five observational studies with control groups.
One RCT compared BiPAP (Bilevel Positive Airways Pressure) and CPAP (Continuous Positive Airways Pressure) for selected patients with obesity hypoventilation syndrome. The study included patients who were satisfactorily ventilated with CPAP, but was inconclusive with respect to the difference between CPAP and BiPAP on our primary outcomes.
For the comparison LTMV versus no LTMV for obesity hypoventilation syndrome we included one RCT comparing the effectiveness of LTMV versus life style advices and 15 studies presenting relevant before versus after data. None of the studies included survival as an outcome. Two case series – very low quality evidence – suggested a positive correlation between LTMV and quality of life scales subdomains. The authors of the RCT did not observe differences in sleepiness (measured one month after initiation of LTMV) between patient randomised to LTMV and life style advice respectively. Some case series suggested an association between the use of LTMV and fewer hospital admissions and positive changes in several sleep-related outcomes. Nearly all studies documented a positive association between the use of LTMV and improvements in daytime arterial blood gas levels.
For patients with chest wall disease we found three controlled observational studies comparing survival among patients using LTMV and LTOT alone. All the three studies reported improved survival following LTMV, but the quality of evidence is low and it is therefore not possible to draw firm conclusions. Data on the effect of LTMV on quality of life are based on uncontrolled observational studies. Initiation of LTMV was associated with positive changes in quality of life, fewer hospital admissions and improved sleep, but it is important to point out that the quality of the evidence is very low and that it is impossible to draw firm conclusions.
Discussion
Situations exist where the effectiveness of LTMV is obvious and evidence from randomized controlled trials is unnecessary. It is important to emphasize that these situations are not dealt with in this report. However, situations also exist where there is uncertainty about whether and when LTMV should be initiated, as reflected by the local and regional variations in use of this type of treatment. The variation in practice suggests a need for robust studies to help inform decisions about when LTMV should be initiated.
We included 33 articles in this systematic review, mainly case series where it is known that the risk of bias is high. Further research, for example well-conducted and robust observational studies, can possibly contribute to less variation in clinical practice.
Conclusions
Obesity hypoventilation syndrome (OHS)
- We did not identify studies from which we could estimate association between initialisation of LTMV and patient survival.
- Starting LTMV-treatment may be associated with a decrease in the number of hospital admittances and improvements in some parameters related to quality of life and sleep. However, the quality of the evidence is very low and it is not possible to draw clear conclusions about the effectiveness of LTMV.
- One randomized controlled trial compared CPAP versus BiPAP in a selected group of patients known to respond adequately to CPAP. The results of the trial were too imprecise to conclude whether the two method differed from each other with respect to our primary outcome, i.e. survival, hospitalisation, quality of life, and sleep.
Chest wall disease (CWD)
- LTMV may be associated with increased survival compared to long-term oxygen treatment alone, but the quality of the evidence is low and any conclusion is uncertain.
- LTMV may be associated with fewer hospital admissions and improvements in some parameters related to quality of life and sleep. However, the quality of the evidence is very low and it is not possible to draw any clear conclusions based on the best available evidence.