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ORIGINAL ARTICLE
Utility of respiratory ward-based NIV in acidotic hypercapnic respiratory failure CHIRAG DAVE,1 ALICE TURNER,1,2 AJIT THOMAS,3 BEN BEAUCHAMP,1 BIMAN CHAKRABORTY,4 ASAD ALI,5 RAHUL MUKHERJEE1 AND DEV BANERJEE6,7 1
Academic Department of Sleep & Ventilation, Heart of England NHS Foundation Trust, 2College of Medical and Dental Sciences, Queen Elizabeth Hospital Research Laboratories and 4School of Mathematics, University of Birmingham, Birmingham and 3Department of Respiratory Medicine, University North Staffordshire Hospital and 5Department of Respiratory Medicine, University Hospitals Coventry and Warwickshire, Coventry, UK, and 6Department of Thoracic and Sleep Medicine, St Vincent’s Hospital Darlinghurst and Clinical School, University of New South Wales and 7Centre for Integrated Research and Understanding Sleep (CIRUS), Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia
ABSTRACT Background and objective: We sought to elicit predictors of in-hospital mortality for first and subsequent admissions with acidotic hypercapnic respiratory failure (AHRF) in a cohort of chronic obstructive pulmonary disease patients who have undergone wardbased non-invasive ventilation (NIV), and identify features associated with long-term survival. Methods: Analysis of prospectively collected data at a single centre on patients undergoing NIV for AHRF between 2004 and 2009. Predictors of in-hospital mortality and intubation were sought by logistic regression and predictors of long-term survival by Cox regression. Results: Initial pH exhibited a threshold effect for in-hospital mortality at pH 7.15. This relationship remained in patients undergoing their first episode of AHRF. In both first and subsequent admissions, a pH threshold of 7.25 at 4 h was associated with better prognosis (P = 0.02 and P = 0.04 respectively). In second or subsequent episodes of AHRF, mortality was lower and predicted only by age (P = 0.002) on multivariate analysis. Conclusions: NIV could be used on medical wards for patients with pH 7.16 or greater on their first admission, although more conservative values should continue to be used for those with a second or subsequent episodes of AHRF. Key words: chronic obstructive pulmonary disease, exacerbation, non-invasive ventilation, rational use of resources, respiratory failure. Abbreviations: AHRF, acidotic hypercapnic respiratory failure; CI, confidence interval; COPD, chronic obstructive pulmonary disease; CT, computed tomography; CXR, chest X-ray; Correspondence: Rahul Mukherjee, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK. Email: [email protected] Received 12 February 2014; invited to revise 26 March, 17 May and 17 June 2014; revised 24 April, 11 June and 7 July 2014; accepted 7 July 2014 (Associate Editor: Amanda Piper). Article first published online: 25 August 2014 © 2014 Asian Pacific Society of Respirology
SUMMARY AT A GLANCE NIV is increasingly used in patients with COPD exacerbations outside an ICU setting. We show that patients with a lower pre-NIV pH (7.15–7.25) do as well as those with a higher pH, potentially advocating its use in a relatively low intensity setting of a respiratory ward-based NIV unit as opposed to a Critical Care Unit. Future guidelines should to take this into account.
EPAP, expiratory positive airway pressure; FEV1, forced expiratory volume in 1 s; HDU, high-dependency unit; ICU, intensive care unit; IPAP, inspiratory positive airway pressure; IQR, interquartile range; ITU, intensive therapy unit; NIV, non-invasive ventilation; OR, odds ratio; SEM, standard error of mean.
INTRODUCTION Chronic obstructive pulmonary disease (COPD) causes one in eight medical hospital admissions in the UK and is the 5th most common presentation to emergency departments.1 Thirty-five per cent of all COPD admissions have type 1 respiratory failure (defined as partial pressure of oxygen (pO2) 6.0 kPa), suggesting that type 2 respiratory failure occurs in a high proportion of cases.2,3 Non-invasive ventilation (NIV) is standard care for COPD exacerbations with acidotic hypercapnic respiratory failure (AHRF).4 Standard medical therapy will improve 80% of patients with a pH between 7.3 and 7.35.5 If pH is 7.26; a threshold identified by subgroup analysis in an early study of ward-based care.5 Guidelines on the application of NIV may need to be amended as experience with ward-based NIV has grown with time,8 with success in older patients,9 and those with hypercapnic encephalopathy.10 NIV audits have also shown benefits in terms of hospital discharge.2,3 While long-term survival may be poor in some, it is good in sufficient numbers to warrant its increasing use.8,11 Readmission and mortality rates in COPD survivors treated with NIV is well documented, but very little data exists on those patients that have second or subsequent presentations with AHRF.12 Up to half of patients with AHRF managed acutely with NIV die in the subsequent year, the majority from respiratory failure.12 Little data exists on patients that have recurrent AHRF episodes. We sought to examine mortality and NIV success rates in patients treated in a respiratory ward with the aim of assessing whether NIV can be effectively used in this setting in more severely acidotic (pH < 7.26) COPD patients, and whether the predictors of outcome differ on second or subsequent presentations with AHRF. We also wished to describe longterm outcomes for this patient cohort, and potential predictors of long-term survival. These patients were also compared with COPD patients managed in a high-dependency unit (HDU) or intensive care unit (ICU) setting. Respirology (2014) 19, 1241–1247
METHODS Patients and data collection This is a prospective observational cohort study of admissions to the respiratory ward, ICU and HDU with AHRF with a diagnosis of COPD, between August 2004 and December 2009. COPD was defined by forced expiratory volume in 1 s (FEV1)/forced vital capacity
ORIGINAL ARTICLE
Utility of respiratory ward-based NIV in acidotic hypercapnic respiratory failure CHIRAG DAVE,1 ALICE TURNER,1,2 AJIT THOMAS,3 BEN BEAUCHAMP,1 BIMAN CHAKRABORTY,4 ASAD ALI,5 RAHUL MUKHERJEE1 AND DEV BANERJEE6,7 1
Academic Department of Sleep & Ventilation, Heart of England NHS Foundation Trust, 2College of Medical and Dental Sciences, Queen Elizabeth Hospital Research Laboratories and 4School of Mathematics, University of Birmingham, Birmingham and 3Department of Respiratory Medicine, University North Staffordshire Hospital and 5Department of Respiratory Medicine, University Hospitals Coventry and Warwickshire, Coventry, UK, and 6Department of Thoracic and Sleep Medicine, St Vincent’s Hospital Darlinghurst and Clinical School, University of New South Wales and 7Centre for Integrated Research and Understanding Sleep (CIRUS), Woolcock Institute of Medical Research, University of Sydney, Sydney, New South Wales, Australia
ABSTRACT Background and objective: We sought to elicit predictors of in-hospital mortality for first and subsequent admissions with acidotic hypercapnic respiratory failure (AHRF) in a cohort of chronic obstructive pulmonary disease patients who have undergone wardbased non-invasive ventilation (NIV), and identify features associated with long-term survival. Methods: Analysis of prospectively collected data at a single centre on patients undergoing NIV for AHRF between 2004 and 2009. Predictors of in-hospital mortality and intubation were sought by logistic regression and predictors of long-term survival by Cox regression. Results: Initial pH exhibited a threshold effect for in-hospital mortality at pH 7.15. This relationship remained in patients undergoing their first episode of AHRF. In both first and subsequent admissions, a pH threshold of 7.25 at 4 h was associated with better prognosis (P = 0.02 and P = 0.04 respectively). In second or subsequent episodes of AHRF, mortality was lower and predicted only by age (P = 0.002) on multivariate analysis. Conclusions: NIV could be used on medical wards for patients with pH 7.16 or greater on their first admission, although more conservative values should continue to be used for those with a second or subsequent episodes of AHRF. Key words: chronic obstructive pulmonary disease, exacerbation, non-invasive ventilation, rational use of resources, respiratory failure. Abbreviations: AHRF, acidotic hypercapnic respiratory failure; CI, confidence interval; COPD, chronic obstructive pulmonary disease; CT, computed tomography; CXR, chest X-ray; Correspondence: Rahul Mukherjee, Heart of England NHS Foundation Trust, Bordesley Green East, Birmingham B9 5SS, UK. Email: [email protected] Received 12 February 2014; invited to revise 26 March, 17 May and 17 June 2014; revised 24 April, 11 June and 7 July 2014; accepted 7 July 2014 (Associate Editor: Amanda Piper). Article first published online: 25 August 2014 © 2014 Asian Pacific Society of Respirology
SUMMARY AT A GLANCE NIV is increasingly used in patients with COPD exacerbations outside an ICU setting. We show that patients with a lower pre-NIV pH (7.15–7.25) do as well as those with a higher pH, potentially advocating its use in a relatively low intensity setting of a respiratory ward-based NIV unit as opposed to a Critical Care Unit. Future guidelines should to take this into account.
EPAP, expiratory positive airway pressure; FEV1, forced expiratory volume in 1 s; HDU, high-dependency unit; ICU, intensive care unit; IPAP, inspiratory positive airway pressure; IQR, interquartile range; ITU, intensive therapy unit; NIV, non-invasive ventilation; OR, odds ratio; SEM, standard error of mean.
INTRODUCTION Chronic obstructive pulmonary disease (COPD) causes one in eight medical hospital admissions in the UK and is the 5th most common presentation to emergency departments.1 Thirty-five per cent of all COPD admissions have type 1 respiratory failure (defined as partial pressure of oxygen (pO2) 6.0 kPa), suggesting that type 2 respiratory failure occurs in a high proportion of cases.2,3 Non-invasive ventilation (NIV) is standard care for COPD exacerbations with acidotic hypercapnic respiratory failure (AHRF).4 Standard medical therapy will improve 80% of patients with a pH between 7.3 and 7.35.5 If pH is 7.26; a threshold identified by subgroup analysis in an early study of ward-based care.5 Guidelines on the application of NIV may need to be amended as experience with ward-based NIV has grown with time,8 with success in older patients,9 and those with hypercapnic encephalopathy.10 NIV audits have also shown benefits in terms of hospital discharge.2,3 While long-term survival may be poor in some, it is good in sufficient numbers to warrant its increasing use.8,11 Readmission and mortality rates in COPD survivors treated with NIV is well documented, but very little data exists on those patients that have second or subsequent presentations with AHRF.12 Up to half of patients with AHRF managed acutely with NIV die in the subsequent year, the majority from respiratory failure.12 Little data exists on patients that have recurrent AHRF episodes. We sought to examine mortality and NIV success rates in patients treated in a respiratory ward with the aim of assessing whether NIV can be effectively used in this setting in more severely acidotic (pH < 7.26) COPD patients, and whether the predictors of outcome differ on second or subsequent presentations with AHRF. We also wished to describe longterm outcomes for this patient cohort, and potential predictors of long-term survival. These patients were also compared with COPD patients managed in a high-dependency unit (HDU) or intensive care unit (ICU) setting. Respirology (2014) 19, 1241–1247
METHODS Patients and data collection This is a prospective observational cohort study of admissions to the respiratory ward, ICU and HDU with AHRF with a diagnosis of COPD, between August 2004 and December 2009. COPD was defined by forced expiratory volume in 1 s (FEV1)/forced vital capacity
