PaCO2 six months after the initiation of long-term noninvasive ventilation in patients with COPD

Relationship Between Episodic Nocturnal Hypercapnia and History of Exacerbations in Patients with Advanced Chronic Obstructive Pulmonary Disease

Purpose

An episodic increase in transcutaneous carbon dioxide pressure (PtcCO₂) is often recognized in patients with advanced chronic obstructive pulmonary disease (COPD) by overnight PtcCO₂ monitoring. This phenomenon, called episodic nocturnal hypercapnia (eNH), mainly corresponds to rapid eye movement (REM) sleep-related hypoventilation. However, it is unclear whether eNH is associated with the frequency of COPD exacerbation. We aimed to investigate whether a relationship exists between COPD exacerbation and eNH.

Patients and Methods

We enrolled consecutive patients with stable, severe, or very severe COPD with a daytime arterial carbon dioxide pressure (PaCO₂) <55.0 mmHg who underwent overnight PtcCO₂ monitoring from April 2013 to January 2017. We retrospectively analyzed the prevalence of eNH and sleep-associated hypoventilation (SH) as defined by the American Academy of Sleep Medicine. Moreover, we compared the relationship between the frequency of COPD exacerbations in the previous year and eNH or SH.

Results

Twenty-four patients were included in this study. The study patients had a mean daytime PaCO₂ and nocturnal PtcCO₂ of 43.3 ± 6.8 mmHg and 42.9 ± 9.6 mmHg, respectively. Six (25.0%) and 11 (45.9%) of the 24 patients met the SH and eNH criteria, respectively. The odds ratios of SH and eNH for at least one annual exacerbation were 1.0 [95% confidence interval (CI): 0.16–6.00] and 11.1 [95% CI: 1.39–87.7], respectively. The odds ratios of SH and eNH for at least two annual exacerbations were 0.3 [95% CI: 0.04–2.64] and 6.6 [95% CI: 1.06–39.4], respectively.

Conclusion

In patients with advanced COPD and a daytime PaCO₂ <55.0 mmHg, eNH may be associated with a history of more frequent exacerbations than SH. Further studies are required to validate these findings.

The cost-effectiveness of domiciliary non-invasive ventilation in patients with end-stage chronic obstructive pulmonary disease: a systematic review and economic evaluation

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic progressive lung disease characterised by non-reversible airflow obstruction. Exacerbations are a key cause of morbidity and mortality and place a considerable burden on health-care systems. While there is evidence that patients benefit from non-invasive ventilation (NIV) in hospital during an acute exacerbation, evidence supporting home use for more stable COPD patients is limited. In the U.K., domiciliary NIV is considered on health economic grounds in patients after three hospital admissions for acute hypercapnic respiratory failure.

OBJECTIVE

To assess the clinical effectiveness and cost-effectiveness of domiciliary NIV by systematic review and economic evaluation.

DATA SOURCES

Bibliographic databases, conference proceedings and ongoing trial registries up to September 2014.

METHODS

Standard systematic review methods were used for identifying relevant clinical effectiveness and cost-effectiveness studies assessing NIV compared with usual care or comparing different types of NIV. Risk of bias was assessed using Cochrane guidelines and relevant economic checklists. Results for primary effectiveness outcomes (mortality, hospitalisations, exacerbations and quality of life) were presented, where possible, in forest plots. A speculative Markov decision model was developed to compare the cost-effectiveness of domiciliary NIV with usual care from a UK perspective for post-hospital and more stable populations separately.

RESULTS

Thirty-one controlled effectiveness studies were identified, which report a variety of outcomes. For stable patients, a modest volume of evidence found no benefit from domiciliary NIV for survival and some non-significant beneficial trends for hospitalisations and quality of life. For post-hospital patients, no benefit from NIV could be shown in terms of survival (from randomised controlled trials) and findings for hospital admissions were inconsistent and based on limited evidence. No conclusions could be drawn regarding potential benefit from different types of NIV. No cost-effectiveness studies of domiciliary NIV were identified. Economic modelling suggested that NIV may be cost-effective in a stable population at a threshold of £30,000 per quality-adjusted life-year (QALY) gained (incremental cost-effectiveness ratio £28,162), but this is associated with uncertainty. In the case of the post-hospital population, results for three separate base cases ranged from usual care dominating to NIV being cost-effective, with an incremental cost-effectiveness ratio of less than £10,000 per QALY gained. All estimates were sensitive to effectiveness estimates, length of benefit from NIV (currently unknown) and some costs. Modelling suggested that reductions in the rate of hospital admissions per patient per year of 24% and 15% in the stable and post-hospital populations, respectively, are required for NIV to be cost-effective.

LIMITATIONS

Evidence on key clinical outcomes remains limited, particularly quality-of-life and long-term (> 2 years) effects. Economic modelling should be viewed as speculative because of uncertainty around effect estimates, baseline risks, length of benefit of NIV and limited quality-of-life/utility data.

CONCLUSIONS

The cost-effectiveness of domiciliary NIV remains uncertain and the findings in this report are sensitive to emergent data. Further evidence is required to identify patients most likely to benefit from domiciliary NIV and to establish optimum time points for starting NIV and equipment settings.

FUTURE WORK RECOMMENDATIONS

The results from this report will need to be re-examined in the light of any new trial results, particularly in terms of reducing the uncertainty in the economic model. Any new randomised controlled trials should consider including a sham non-invasive ventilation arm and/or a higher- and lower-pressure arm. Individual participant data analyses may help to determine whether or not there are any patient characteristics or equipment settings that are predictive of a benefit of NIV and to establish optimum time points for starting (and potentially discounting) NIV.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42012003286.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The Importance of Stabilizing PaCO2 during Long-term Non-invasive Ventilation in Subjects with COPD

OBJECTIVE

In subjects with chronic obstructive pulmonary disease (COPD), the effect of partial pressure of CO2 (PaCO2) alterations during long-term non-invasive ventilation (NIV) on continuance remains uncertain. We herein investigated the utility of PaCO2 stability during long-term NIV as a prognostic outcome.

METHODS

We retrospectively assessed data from 54 subjects with COPD who received long-term NIV. The annual alteration in PaCO2 during NIV was determined using a simple linear regression method for each subject who had at least two 6-month intervals of PaCO2 data. Annual alterations in PaCO2 during long-term NIV and probable confounders were examined, and long-term NIV discontinuation was the major outcome.

RESULTS

Data from 37 subjects who met the criteria were analyzed. PaCO2 during long-term NIV increased slightly in 19 subjects (group 1, <2 mm Hg/y), and increased greatly in 18 subjects (group 2, >2 mmHg/y). In the multivariate modality model, smaller annual alterations in PaCO2 (p=0.009) and lower PaCO2 6 months after the start of long-term NIV (6 m-PaCO2) (p=0.03) were associated with a significantly higher probability of continuing NIV. The 2- and 5-year probabilities of continuing NIV were 89% and 66% for group 1 and 78% and 32% for group 2, respectively.

CONCLUSION

A lower 6 m-PaCO2 and a lower annual alteration of PaCO2 during long-term NIV are significant predictive variables for patients with COPD.