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Chronic hypercapnic respiratory failure occurs in several conditions associated with hypoventilation. The mechanisms underlying the development of chronic hypercapnia include a combination of processes that increase metabolic CO2 production, reduce minute ventilation (V'e), or increase dead space fraction (Vd/Vt). Fundamental to the pathophysiology is a mismatch between increased load and a reduction in the capacity of the respiratory pump to compensate. Though neural respiratory drive may be decreased in a subset of central hypoventilation disorders, it is more commonly increased in attempting to maintain the load-capacity homeostatic balance.

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High-flow nasal therapy (HFNT) has an increasing role in the management of acute hypoxic respiratory failure. Due to its tolerable interface and ease of use, its role in chronic hypercapnic respiratory failure (CHRF) is emerging. This article examines the literature to date surrounding the short and long-term mechanisms of HFNT in sleep and wakefulness of CHRF patients. It is likely HFNT will have an increasing role in those patients intolerant of non-invasive ventilation.

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INTRODUCTION: Chronic effects of noninvasive ventilation on myocardial function in patients with obesity hypoventilation syndrome (OHS) are scarcely understood. The aim of the present study was to evaluate the long-term effects of volume-targeted bilevel positive airway pressure ventilation (BiPAP) on cardiac parameters and myocardial biomarkers in patients with OHS. METHODS: Clinically stable patients with OHS referred to the tertiary center for the initiation of long-term BiPAP therapy were consecutively enrolled. At baseline, all participants underwent overnight cardiorespiratory polygraphy. BiPAP therapy using volume-targeted spontaneous/timed mode delivered via an oro-nasal mask was initiated. Beat-to-beat noninvasive monitoring by impedance cardiography was used to assess heart function at baseline and after 3 and 12 months of BiPAP use. Serum troponin 1, N-Terminal Pro-B-Type Natriuretic Peptide (NT-ProBNP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) were monitored. RESULTS: Thirteen patients (10 men; mean age, 55.8 ± 9.8 years; mean body mass index of 47.8 ± 5.9 kg/m2) were recruited. From baseline to 3, and to 12 months of BiPAP use, left ventricular stroke volume (SV), ejection time (LVET), and ejection time index significantly increased (P = 0.030; P < 0.001; P = 0.003, respectively), while heart rate and systolic time ratio significantly decreased (P = 0.004; P = 0.034, respectively). Reductions in serum NT-proBNP, IL-6 and TNF-α were observed (P = 0.045; P = 0.018; P = 0.003, respectively). No significant changes in serum troponin were detected throughout the study. CONCLUSIONS: The present findings of increased SV, in association with lengthening of LVET, reductions of NT-proBNP and reductions in circulatory inflammatory markers in patients with stable OHS and chronic moderate-to-severe daytime hypercapnia treated with BiPAP over 1 year support the role of this therapeutic mode in such patients.

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Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease. Historically, two COPD phenotypes have been described: chronic bronchitis and emphysema. Although these phenotypes may provide additional characterization of the pathophysiology of the disease, they are not extensive enough to reflect the heterogeneity of COPD and do not provide granular categorization that indicates specific treatment, perhaps with the exception of adding inhaled glucocorticoids (ICS) in patients with chronic bronchitis. In this review, we describe COPD phenotypes that provide prognostication and/or indicate specific treatment. We also describe COPD-like phenotypes that do not necessarily meet the current diagnostic criteria for COPD but provide additional prognostication and may be the targets for future clinical trials.

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The purpose of this article is to identify (by brand name) and then classify the modes available on contemporary portable ventilators used for noninvasive ventilation in the United States. We propose a formal taxonomy that identifies the modes by their control variable, breath sequence, and targeting scheme, therefore describing what the mode does. Use of this taxonomy should be helpful in finding modes with comparable functionality that cater to the specific goal of mechanical ventilation and effective ventilatory strategies for each disease state.

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Chronic hypercapnic respiratory failure in obstructive lung diseases may benefit from nocturnal Home non-invasive ventilation (HNIV). It has been shown that in patients with persistence of hypercapnia after an acute episode of chronic obstructive pulmonary disease (COPD) exacerbation requiring mechanical ventilation, HNIV may improve the risk for new admission and survival. The ability to reach these aims depends on the correct timing of enrolling patients, as well as a correct definition of ventilatory needing and setting of the ventilator. This review tries to define a possible home treatment path of hypercapnic respiratory failure in COPD by analyzing the main studies published in recent years.

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BACKGROUND: Long-term noninvasive ventilation (NIV) can increase or maintain health-related quality of life (HRQoL) for patients with chronic hypercapnic respiratory failure (CHRF). Evidence from studies systematically assessing how NIV-specific factors influence HRQoL is limited. OBJECTIVES: The objective of this study was to describe HRQoL measured by the Severe Respiratory Insufficiency Questionnaire (SRI) in patients with CHRF treated with long-term NIV and to analyze the associations between HRQoL and hypoxemia, hypercapnia, and respiratory events such as apneas, hypopneas (AHI), and patient ventilator asynchrony (PVA) occurring during long-term NIV. METHODS: We included sixty-seven stable patients with established long-term NIV due to neuromuscular disease or thoracic cage disorders in a prospective cross-sectional study at Oslo University Hospital. Patients answered the SRI and underwent daytime arterial blood gases, nocturnal pulse oximetry, sleep polygraphy, and nocturnal transcutaneous CO2. RESULTS: The mean global SRI for 62 patients was 64.8 ± 14.5, with the highest score in SRI Social Relationships (79.5 ± 15.6). There were no differences in HRQoL between the different patient groups. Compliant patients had a significantly higher score in SRI Attendant and Sleep. Residual nocturnal hypoxemia affected both the subscale SRI "Respiratory Complaints" and SRI "Attendant Symptoms and Sleep." Persisting daytime hypercapnia, nocturnal hypoventilation, and high AHI affected the subscale SRI "Anxiety" negatively, while frequent PVA was associated with a lower score in SRI "Physical Function." CONCLUSION: In a group of patients with long-term NIV, undesired respiratory events during NIV are associated with lower HRQoL in several of the SRI subscales. We suggest designing interventional studies to confirm the possible relationship between HRQoL and respiratory events during long-term NIV.

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BACKGROUND: Long-term noninvasive ventilation (LTNIV) is widely used in patients with chronic hypercapnic respiratory failure (CHRF) related to COPD. Prognosis of these patients is however poor and heterogenous. RESEARCH QUESTION: In COPD patients under LTNIV for CHRF, is it possible to identify specific phenotypes which are predictive of probability of pursuing NIV and survival? STUDY DESIGN AND METHODS: A latent class analysis was performed in a COPD population under LTNIV included in a comprehensive database of patients in the Geneva Lake area, to determine clinically relevant phenotypes. The observation period of this subgroup of COPD was extended to allow assessment of survival and/or pursuit of NIV for at least 2 years after inclusion. A logistic regression was conducted to generate an equation accurately attributing an individual patient to a defined phenotype. The identified phenotypes were compared on a series of relevant variables, as well as for probability of pursuing NIV or survival. A competitive risk analysis allowed to distinguish death from other causes of cessation of NIV. RESULTS: Two phenotypes were identified: a "respiratory COPD" profile with very severe airway obstruction, a low or normal body mass index, and a low prevalence of comorbidities and a "systemic COPD" profile of obese COPDs with moderate airway obstruction and a high rate of cardiovascular and metabolic comorbidities. The logistic regression correctly classified 95.7% of patients studied. Probability of pursuing NIV and survival were significantly related to these phenotypes, with a poorer prognosis for "respiratory COPD." Probability of death 5 years after implementing NIV was 22.3% (95% CI: 15.4-32.2) for "systemic COPD" versus 47.2% (37.4-59.6) for "respiratory COPD" (p = 0.001). CONCLUSION: The two distinct phenotypes of COPD under LTNIV for CHRF identified appear to be strongly related to prognosis and require further validation in other cohort studies.

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Long term noninvasive ventilation (LTNIV) is a recognized treatment for chronic hypercapnic respiratory failure (CHRF). COPD, obesity-hypoventilation syndrome, neuromuscular disorders, various restrictive disorders, and patients with sleep-disordered breathing are the major groups concerned. The purpose of this narrative review is to summarize current knowledge in the field of monitoring during home ventilation. LTNIV improves symptoms related to CHRF, diurnal and nocturnal blood gases, survival, and health-related quality of life. Initially, patients with LTNIV were most often followed through elective short in-hospital stays to ensure patient comfort, correction of daytime blood gases and nocturnal oxygenation, and control of nocturnal respiratory events. Because of the widespread use of LTNIV, elective in-hospital monitoring has become logistically problematic, time consuming, and costly. LTNIV devices presently have a built-in software which records compliance, leaks, tidal volume, minute ventilation, cycles triggered and cycled by the patient and provides detailed pressure and flow curves. Although the engineering behind this information is remarkable, the quality and reliability of certain signals may vary. Interpretation of the curves provided requires a certain level of training. Coupling ventilator software with nocturnal pulse oximetry or transcutaneous capnography performed at the patient's home can however provide important information and allow adjustments of ventilator settings thus potentially avoiding hospital admissions. Strategies have been described to combine different tools for optimal detection of an inefficient ventilation. Recent devices also allow adapting certain parameters at a distance (pressure support, expiratory positive airway pressure, back-up respiratory rate), thus allowing progressive changes in these settings for increased patient comfort and tolerance, and reducing the requirement for in-hospital titration. Because we live in a connected world, analyzing large groups of patients through treatment of "big data" will probably improve our knowledge of clinical pathways of our patients, and factors associated with treatment success or failure, adherence and efficacy. This approach provides a useful add-on to randomized controlled studies and allows generating hypotheses for better management of HMV.

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Long-term mechanical ventilation is a well-established treatment for chronic hypercapnic respiratory failure (CHRF). It is aimed at improving CHRF-related symptoms, health-related quality of life, survival, and decreasing hospital admissions. In Switzerland, long-term mechanical ventilation has been increasingly used since the 1980s in hospital and home care settings. Over the years, its application has considerably expanded with accumulating evidence of beneficial effects in a broad range of conditions associated with CHRF. Most frequent indications for long-term mechanical ventilation are chronic obstructive pulmonary disease, obesity hypoventilation syndrome, neuromuscular and chest wall diseases. In the current consensus document, the Special Interest Group of the Swiss Society of Pulmonology reviews the most recent scientific literature on long-term mechanical ventilation and provides recommendations adapted to the particular setting of the Swiss healthcare system with a focus on the practice of non-invasive and invasive home ventilation in adults.

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INTRODUCTION: Home noninvasive mechanical ventilation (HNIV) in patients with chronic hypercapnic respiratory failure (CHRF) may improve the health-related quality of life (HRQoL) and reduce hospitalizations. OBJECTIVE: To determine the effects of HNIV on HRQoL, sleep quality and hospitalization rates in restrictive thoracic diseases (RTD) and chronic obstructive pulmonary disease (COPD) patients with CHRF. METHODS: In this prospective, single center study patients divided into two groups; the COPD and the RTD groups. HRQoL assessed by The Medical Outcome Study 36-Item Short-form Health Survey (SF-36) and Severe Respiratory Insufficiency (SRI); the sleep quality was assessed by Epworth and Pittsburgh Sleep Quality Index questionnaires. The patients were reevaluated first month, third months, sixth months and 1 year following HNIV establishment, during which time, hospitalization rates were recorded. RESULTS: Ninety (COPD n = 50, RTD n = 40) out of 102 eligible patients completed the study. Significant improvements in blood gases and HRQoL were observed in the first month of HNIV establishment and remained stable. Mean ± SD SRI summary scale improved significantly from 30 ± 12 baseline to 65 ± 16 at 1 year in COPD group (P < 0.001) and from 39 ± 13 to 63 ± 18 in RTD group (P < 0.001). HNIV reduced hospitalization rates from a mean of 1.9 ± 1.1 to 0.5 ± 0.9 in COPD group (P < 0.001) and a mean of 1.9 ± 1 to 0.5 ± 0.7 in RTD group (P < 0.001). CONCLUSION: HNIV improves HRQoL, sleep quality and gas exchange and reduces hospitalizations in patients with CHRF regardless of etiology.

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Background: The purpose of this guideline is to optimize evaluation and management of patients with obesity hypoventilation syndrome (OHS).Methods: A multidisciplinary panel identified and prioritized five clinical questions. The panel performed systematic reviews of available studies (up to July 2018) and followed the Grading of Recommendations, Assessment, Development, and Evaluation evidence-to-decision framework to develop recommendations. All panel members discussed and approved the recommendations.Recommendations: After considering the overall very low quality of the evidence, the panel made five conditional recommendations. We suggest that: 1) clinicians use a serum bicarbonate level <27 mmol/L to exclude the diagnosis of OHS in obese patients with sleep-disordered breathing when suspicion for OHS is not very high (<20%) but to measure arterial blood gases in patients strongly suspected of having OHS, 2) stable ambulatory patients with OHS receive positive airway pressure (PAP), 3) continuous positive airway pressure (CPAP) rather than noninvasive ventilation be offered as the first-line treatment to stable ambulatory patients with OHS and coexistent severe obstructive sleep apnea, 4) patients hospitalized with respiratory failure and suspected of having OHS be discharged with noninvasive ventilation until they undergo outpatient diagnostic procedures and PAP titration in the sleep laboratory (ideally within 2-3 mo), and 5) patients with OHS use weight-loss interventions that produce sustained weight loss of 25% to 30% of body weight to achieve resolution of OHS (which is more likely to be obtained with bariatric surgery).Conclusions: Clinicians may use these recommendations, on the basis of the best available evidence, to guide management and improve outcomes among patients with OHS.

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The role of noninvasive positive pressure ventilation (NIV) in severe chronic obstructive pulmonary disease (COPD) has been controversial. Over the past two decades, data primarily obtained from Europe have begun to define the clinical characteristics of patients likely to respond, the role of high-intensity NIV, and the potential best timing of initiating therapy. These approaches, however, have not been validated in the context of the U.S. healthcare delivery system. Use of NIV in severe COPD in the United States is limited by the practicalities of doing in-hospital titrations as well as a complex system of reimbursement. These systematic complexities, coupled with a still-emerging clinical trial database regarding the most effective means to deliver NIV, have led to persistent uncertainty regarding when in stable severe COPD treatment with NIV is actually appropriate. In this review, we propose an assessment algorithm and treatment plan that can be used in clinical practice in the United States, but we acknowledge that the absence of pivotal clinical trials largely precludes a robust evidence-based approach to this potentially valuable therapy.

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OBJECTIVES: To evaluate the sensitivity and specificity of a screening test panel for nocturnal hypoventilation (NH) and other sleep related respiratory events during monitoring of patients with chronic hypercapnic respiratory failure (CRF) treated with NIV. METHODS: We performed a prospective study at Oslo University Hospital. Eligible for inclusion were consecutive adults with CRF due to neuromuscular diseases or chest wall disorders treated with NIV scheduled for a follow-up visit. All patients underwent the screening test panel (clinical evaluation, daytime arterial blood gas (ABG), nocturnal pulse oximetry (SpO2) and data from ventilator software) and the reference tests; sleep polygraphy and nocturnal transcutaneous CO2. RESULTS: Of 67 patients included, NH was confirmed in 23-50 according to the 3 definitions used for NH, apnea-hypopnea index (AHIpolygraphy) ≥ 10 was confirmed in 16 and patient-ventilator asynchrony (PVA) ≥ 10% of total recording time in 14. Sensitivity of the combined screening test panel for NH was 87% (95% confidence interval 66-97), 84% (66-95) and 80% (66-90), for abnormal AHIpolygraphy 91% (59-100) and for PVA 71% (42-92). Sensitivity for NH of SpO2 was 48% (27-69), 39% (22-58) and 38% (24-53) and of daytime ABG 74% (52-90), 74% (55-88) and 68% (53-80). Sensitivity and specificity of AHIsoftware for AHIpolygraphy ≥ 10 was 93% (68-100) and 92% (81-98) respectively. DISCUSSION: In patients treated with long term NIV, screening test panel, nocturnal SpO2 and daytime ABG all failed to accurately detect NH, underlining the importance of nocturnal monitoring of CO2. AHIsoftware accurately identified obstructive events and can be used to modify NIV settings. TRIAL REGISTRATION: N° NCT01845233.

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BACKGROUND: Home noninvasive ventilation (NIV) has been increasingly used in stable chronic obstructive pulmonary disease (COPD) with chronic hypercapnic respiratory failure (CHRF). However its effectiveness remains debatable. AIM: To describe a follow-up of COPD patients under home NIV. METHODS: Retrospective descriptive study based on a prospective 3-year database that included COPD patients under home NIV between August 2011 and July 2014. RESULTS: Within the 334 patients initially screened, 109 (32.6%) had COPD with a mean±SD post-bronchodilator FEV1 of 38.6±14.9% predicted; age of 65.6±9.6 years. The mean±SD duration of ventilation was 63.4±51.1 months. Heterogeneous comorbidities that can contribute to CHRF were not excluded: obstructive sleep apnea and obesity were the most prevalent. Sixty-two (56.9%) patients started NIV during admission with acute respiratory failure. During follow-up there was a significant increase in mean inspiratory positive airway pressure (IPAP) and respiratory rate (19.5±4.4 vs. 23.6±5.3cmH2O and 10.7±5.2 vs. 15.2±1.4 breaths/min, respectively, p<0.0001), with a significant improvement in hypercapnia (PaCO2: 52.9±7.7 vs. 49.5±7.5mmHg, p<0.0001), with 93.3% of patients compliant to NIV. Admissions and days spent in hospital for respiratory illness significantly decreased after institution of NIV (respectively, 1.2±1.1 vs. 0.7±1.8 and 15.0±16.8 vs. 8.8±19.4, p<0.001). At final evaluation, patients with severe hypercapnia (n=47; PaCO2 ≥50mmHg) performing NIV at higher pressures (n=30; IPAP ≥25cmH2O) were more compliant (10.1±3.3 vs. 6.1±3.6h/day). Three-year mortality was 24.8% (27 of 109 patients). CONCLUSIONS: This is a real-life retrospective study in COPD patients with CHRF which results suggest benefit from home NIV. For most, NIV was effective and tolerable even at high pressures.

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BACKGROUND: Non-invasive ventilation (NIV) is increasingly used in the treatment of patients with chronic hypercapnic respiratory failure (CRF). Residual sleep related respiratory events under NIV such as obstructive or central apnea/hypopnea (AH), or patient-ventilator asynchrony (PVA), may compromise treatment efficacy and/or comfort. AIMS OF STUDY: 1/to quantify the frequency and describe the types of both AH and PVA in a large group of stable patients with CRF during night-time NIV; 2/to analyze the influence of these events on overnight pulse oximetry and transcutaneous CO2 and 3/to assess interrater agreement in identifying and quantifying AH and PVA. METHODS: We quantified AH and PVA by performing sleep polygraphy in 67 patients during elective follow-up visits. Traces were scored by two trained physicians. RESULTS: Residual AH were frequent: 34% of the patients had an AH Index >5/hour, with obstructive hypopnea being the most frequent event. In addition, 21% of the patients had PVA >10% of total recording time. No correlation was found between respiratory events and overnight hypercapnia. The intraclass correlation coefficients for scoring AHI and time with PVA were 0.97 (0.94-0.98) and 0.85 (0.75-0.91) respectively. CONCLUSIONS: Residual respiratory events are common in patients treated with long term NIV for chronic hypercapnic respiratory failure and can be scored with a very high interobserver agreement. However, these events were not associated with persistent nocturnal hypercapnia; thus, their clinical relevance has yet to be clarified. CLINICALTRIALS.GOV REGISTRATION N°: NCT01845233.

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BACKGROUND: The Severe Respiratory Insufficiency (SRI) Questionnaire was originally developed in German to assess health-related quality of life (HRQL) and was validated as a multidimensional instrument with high psychometric properties in chronic hypercapnic respiratory failure (CHRF) patients receiving noninvasive ventilation (NIV). We aimed to investigate the intercultural adaptation of the Japanese SRI Questionnaire and whether it is a reliable and valid HRQL questionnaire to administer to those patients. METHODS: The SRI Questionnaire was adapted to Japanese using a translation and back-translation procedure, followed by equivalency assessment. It was validated in 56 stable outpatients receiving NIV for CHRF, primarily due to chronic obstructive pulmonary disease (COPD) and/or pulmonary tuberculosis sequelae. RESULTS: Examination of the frequency distribution of the Japanese SRI Questionnaire showed that the subscales and summary were approximately normally distributed and well balanced. There were no significant differences in SRI scores between patients with COPD and pulmonary tuberculosis sequelae. Cronbach׳s α values representing internal consistency of seven SRI subscales ranged from 0.56 to 0.80; attendant symptoms and sleep had the lowest values. Cronbach׳s α value was 0.92 for the SRI summary. The SRI summary score was significantly related to all eight subscales of the Medical Outcomes Study 36-item short form, with correlation coefficients of 0.41-0.66. CONCLUSIONS: The Japanese SRI Questionnaire was produced using a standardized procedure and an equivalency study. It has high psychometric properties with internal consistency and concurrent validity. The Japanese SRI Questionnaire can be used to assess HRQL in patients on NIV for CHRF.

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BACKGROUND: Health status and mortality are important outcomes in patients with advanced pulmonary diseases receiving noninvasive ventilation (NIV). However, their relationship has not been thoroughly investigated. METHODS: The present study prospectively recruited 56 stable outpatients treated with NIV for chronic hypercapnic respiratory failure caused by chronic obstructive pulmonary disease and/or pulmonary tuberculosis sequelae. At baseline, health status was measured by the Medical Outcomes Study 36-item short form, a generic questionnaire; the St. George's Respiratory Questionnaire (SGRQ), a respiratory-specific questionnaire; and two respiratory failure-specific questionnaires, the Maugeri Respiratory Failure questionnaire and the Severe Respiratory Insufficiency (SRI) questionnaire. Arterial blood gas, pulmonary function, dyspnea and psychological status were also measured. RESULTS: In cross-sectional comparisons of the four health status questionnaires, the SGRQ and SRI questionnaire had lower floor and ceiling effects. During the 3-year follow-up, 16 patients (29%) died. Health status shown by the SGRQ and SRI was significantly predictive of mortality, independently of the physiological measures of low body mass index (BMI), hypercapnia, and low pulmonary function. Stepwise multivariate analyses indicated that the SRI summary score was the most significant predictor of mortality (P = 0.0006) followed by BMI (P = 0.012). CONCLUSION: There was a significant relationship between health status and 3-year mortality in patients with NIV, independently of under-nutrition, hypercapnia and low pulmonary function. Health status measurement is important not only to comprehensively evaluate disease severity in relation to its close association with mortality, but also to elucidate factors that improve the survival of patients with advanced respiratory diseases.

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BACKGROUND: Endoscopic lung volume reduction coil (LVRC) treatment is an option for selected patients with severe emphysema. In the advanced stages, emphysema leads to respiratory failure: hypoxemia and eventually chronic hypercapnic respiratory failure. It can be hypothesized that LVRC treatment, a procedure targeting hyperinflation and thereby reducing ventilatory workload, may be especially beneficial in patients with chronic hypercapnic respiratory failure. This study was conducted to gain first insights into the effects and the safety of LVRC treatment in patients with emphysema and chronic hypercapnic respiratory failure. METHODS: A retrospective observational study conducted in the Department of Respiratory Medicine at the University Medical Center Hamburg-Eppendorf, Germany on all patients with chronic hypercapnic respiratory failure in whom bilateral LVRC treatment was performed between 1 April 2012 and 30 September 2015. RESULTS: During the study period, bilateral LVRC treatment was performed in 10 patients with chronic hypercapnic respiratory failure. Compared with baseline, bilateral LVRC treatment led to a significant increase in mean forced expiratory volume in one second (FEV1) from 0.5 ± 0.1 l to 0.6 ± 0.2 l ( p = 0.004), a decrease in residual volume (RV) from 6.1 ± 0.9 l to 5.6 ± 1.1 l ( p = 0.02) and a reduction in partial pressure of carbon dioxide in arterial blood (PaCO2) from 53 ± 5 mmHg to 48 ± 4 mmHg ( p = 0.03). One case of hemoptysis requiring readmission to hospital was the only severe adverse event. CONCLUSIONS: LVRC treatment was safe and effective in patients with nonsevere chronic hypercapnic respiratory failure. It led not only to an improvement in lung function but also to a significant decrease in PaCO2.

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BACKGROUND: Extracorporeal carbon dioxide removal (ECCO2R) has been gaining interest to potentially facilitate gas transfer and equilibrate mild to moderate hypercapnic acidosis, when standard therapy with non-invasive ventilation is deemed refractory. However, concern regarding the effectiveness of low-flow CO2 removal remains. Additionally, the prospect to steadily reduce hypercapnia via low-flow ECCO2R technique is limited, especially with regional anticoagulation which potentially reduces the risk of bleeding. Therefore, an in vivo study was conducted to determine the efficacy of CO2 removal through a modified renal dialysis unit during the carbon dioxide dialysis study using systemic and regional anticoagulation. METHODS: The acute study was conducted for 14 h in landrace pigs (51 ± 3 kg). CO2 removal using a diffusion membrane oxygenator substituting the hemoconcentrator was provided for 6 h. Blood and gas (100 % O2) flows were set at 200 and 5 L/min, respectively. Anticoagulation was achieved by systemic heparinization (n = 7) or regional trisodium citrate 4 % (n = 7). RESULTS: The CO2 transfer was highest during the initial hour and ranged from 45 to 35 mL/min, achieving near eucapnic values. Regional and systemic anticoagulation were both effective in decreasing arterial pCO2 (from 8.9 ± 1.3 kPa to 5.6 ± 0.8 kPa and from 8.6 ± 1.0 kPa to 6.3 ± 0.7 kPa, p < 0.05 for both groups, respectively). Furthermore, pH improved (from 7.32 ± 0.08 to 7.47 ± 0.07 and from 7.37 ± 0.04 to 7.49 ± 0.01, p < 0.05) for both regional and systemic anticoagulation groups, respectively. Upon ceasing CO2 dialysis, hypercapnia ensued. The liver and kidney function test results were normal, and scanning electron microscopy analysis revealed only some cellular and fibrin adhesion on the oxygenator fibre in the heparin group. CONCLUSIONS: CO2 dialysis utilizing either regional or systemic anticoagulation showed to be safe and effective in steady transfer of CO2 and consequently optimizing pH.