Non-invasive ventilation in chronic obstructive pulmonary disease: management of acute type 2 respiratory failure

Abstract

IntroductionNon-invasive ventilation (NIV) in the management of acute type II respiratory failure in patients with chronic obstructive pulmonary disease (COPD) represents one of the major technical advances in respiratory care over the last decade. The National Institute for Health and Clinical Excellence (NICE) recommend that NIV be available in all hospitals admitting patients with COPD. 1 This has led to a rapid expansion in the provision of NIV services with over 90% of UK admitting hospitals offering this intervention. The UK national audit of acute hospital COPD care in 2003, however, suggested that treatment was often applied to patients outside the existing British Thoracic Society (BTS) inclusion criteria. 2,3 This document updates the 2002 BTS guidance and provides a specific focus on the use of NIV in COPD patients with acute type 2 respiratory failure. While there are a variety of ventilator units available most centres now use bi-level positive airways pressure (BiPAP) units and this guideline refers specifically to this form of ventilatory support although many of the principles encompassed are applicable to other forms of NIV. The guideline has been produced for the clinician caring for COPD patients in the emergency and ward areas of acute hospitals. Guideline development was in accordance with the AGREE principles and is summarised in the online version of this guideline (www.rcplondon. ac.uk/pubs/brochure.aspx?e=258). An extended version of this guideline encompassing service provision is available on the BTS website. Clinical contextNon-invasive ventilation, within the intensive care unit and the ward environment, has been shown in randomised controlled trials and systematic reviews to reduce intubation rate and mortality in COPD patients with decompensated respiratory acidosis (pH <7.35 and PaCO 2 >6 kPa) following immediate medical therapy. 5-14 It should therefore be considered within the first 60 minutes of hospital arrival in all patients with an acute exacerbation of COPD in whom a respiratory acidosis persists despite maximum standard medical treatment, which includes:• controlled oxygen to maintain SaO 2 88-92% • nebulised salbutamol 2.5-5 mg • nebulised ipratroprium 500 µg • prednisolone 30 mg • antibiotic agent (when indicated).A clearly documented treatment plan for NIV, including how potential failure will be dealt with and whether escalation to intubation and mechanical ventilation is indicated, should be documented in the case notes at the outset of treatment. Whenever possible the patient and carers should be involved in these discussions. Once started, patient comfort, breathing synchrony and enhanced compliance are key factors in determining outcome. Low starting pressures increase patient compliance but should be quickly adjusted upwards to achieve therapeutic effect. If effective, treatment will usually be required until the acute cause has resolved, commonly about two to three days.s CONCISE GUIDELINES

Acidotic Hypercapnia: A Case Series of Acidosis Driven Respiratory Muscle Dysfunction

“…At present, respiratory failure is widely categorized as either type 1 (hypoxemia) or type 2 (hypoxemia with an associated hypercapnia). Previous prospective randomized trials demonstrating the efficacy of NIV in patients with type 2 respiratory failure secondary to an AECOPD, used the pH as the primary indicator of the acuity of the respiratory failure (without reference to the serum bicarbonate concentration) [1]. Therefore, patients with type 2 respiratory failure secondary to metabolic acidosis, as described in this case series, were not previously recognized as a subgroup.…”

“…A 64-year-old housewife with type 2 diabetes mellitus (on metformin) and a background ventilatory insufficiency due to COPD (FEV 1 …”

“…There is now a substantial evidence base demonstrating the efficacy of non-invasive ventilation (NIV) in patients who develop hypercapnic respiratory failure associated with acidosis, predominantly in those with chronic obstructive pulmonary disease (COPD) [1,2]. However, there is a paucity of information about 1) whether the hypercapnia caused a respiratory acidosis (hypercapnic acidosis) as classically occurs with COPD; 2) whether metabolic acidosis led to hypercapnia (acidotic hypercapnia); and 3) whether the management of patients with acidotic hypercapnia should differ from those with hypercapnic acidosis.…”

Management of acute exacerbations of chronic obstructive pulmonary disease:the first 24 hours

“…A useful summary statement has recently been published. 4 Patients who are obtunded and periarrest require immediate intubation and mechanical ventilation. There is some evidence that intensivists are reluctant to accept COPD exacerbators to the intensive care unit because of the perceived low survival rates or concerns about weaning delays after intubation.…”

Non-invasive ventilation: established and expanding roles

“…Arterial blood gas tensions should be repeated after an appropriate interval, usually one to two hours. 10 Approximately 20% of patients acidotic on arrival in accident and emergency can be expected to improve, with pH returning into the normal range with these interventions alone. 11 NIV is recommended in hypercapnic patients when the pH remains less than 7.35 and the respiratory rate greater than 23 breaths per minute.…”