A 68-year-old went into respiratory arrest on the chest ward. He had been admitted 2 weeks previously for an exacerbation of chronic obstructive airways disease (COAD). He has had two previous episodes of reduced conscious level due to hypercapnoea, which resolved with non-invasive ventilation and oxygen titration.

He was immediately intubated on the ward and transferred to the intensive care unit for ventilation. Hypoxia was corrected to a PaO2 >8.0kPa with a moderate FiO2. However he remained very difficult to ventilate and maintained a persistently high PaCO2. The highest level was 21kPa. He was treated with B2 agonist nebulisers, anti-muscarinic nebulisers, systemic steroids, aminophylline infusions, magnesium infusions and a ketamine infusion. He also needed vasopressor support and for a period of time continuous renal replacement therapy. After a week when his ventilator pressures reduced he had an uneventful percutaneous tracheostomy. Sedation was then reduced and he was awake and spontaneously breathing but with a high level of support. He was recurrently troubled by episodes of bronchospasm and air trapping. The lowest settings for inspiratory pressure were 14 cmH2O. He deteriorated a number of times before care was withdrawn and he died 20 days later.

Can we predict which COAD patients will benefit from mechanical ventilation?

James Day

Chronic obstructive airways disease is a common disease and recurrently presents with respiratory failure. The management of these patients has been more aggressive over the last few decades. This is in keeping with a trend in intensive care to treat patients who are older and with chronic diseases. In 2004 exacerbations of COAD were the fourth leading cause of death worldwide. There is uncertainty whether invasive intubation is always appropriate and which prognostic variables are predictive of poor outcome.

The SUPPORT study (1) in 1996 was a prospective cohort study in 1,016 patients and showed survival time was independently related to severity of illness, body mass index (BMI), age, prior functional status, PaO2/FiO2, congestive heart failure, serum albumin, and the presence of cor pulmonate.

In 2008 the COPD and asthma outcome (CAOS) study (2), a prospective cohort study in the UK recruited 832 patients admitted to critical care with decompensated type 2 respiratory failure. Outcomes included survival at 180 days and quality of life. Of the cohort 62% survived to 180 days and of those who responded to the questionnaire 73% reported that their quality of life was the same or better than their pre-admission status. 96% said that they would choose similar treatment again.

National Institute for Clinical Excellence (NICE) guidelines published in 2011 (3). These look at all aspect of care for those with COAD. Regarding intensive care treatment they recommend patients with exacerbations should receive invasive ventilation when thought necessary. During exacerbations of COAD, functional status, BMI, requirement for oxygen when stable, comorbidities and previous admissions to intensive care units should be considered, in addition to age and forced expiratory volume in 1 second (FEV1), when assessing suitability for intubation and ventilation. Neither age nor FEV1 should be used in isolation when assessing suitability. They also recommend non-invasive ventilation should be considered for patients who are slow to wean from invasive ventilation.

It seems that we are more prejudiced against COAD compared to acute respiratory distress syndrome (ARDS). The mean duration of mechanical ventilation for COAD patients compared to ARDS patients was 5.1 vs. 8.8 respectively p<0.001 (4). However Nevins 2001 (5) identified a mean duration of ventilation of 9 days (median 4 days). The mortality rate in ICU for patients who received ventilation for an exacerbation of COPD was estimated at 22%. Patient receiving mechanical ventilation due to acute decompensation of COAD had a significantly lower mortality than patients receiving mechanical ventilation because of acute respiratory failure (ARF) or other aetiologies. COAD OR 0.70; (95% CI 0.59 to 0.83); p=<0.001 compared to coma OR 1.31; (95%CI; 1.19 to 1.45); p<0.001573.

Length of hospital stay in ICU was 1.2 days in the COAD patients compared to 24.5 days in the ARDS patients, p=0.07, whilst length of stay in hospital was 21.2 days in the COPD group versus 24.5 days in the ARDS group p=0.07 (4). Nevins (5) identified a mean duration of hospital stay of 22 days in COAD patients requiring ventilation.

In 2011 an integrative review looked to assess the prognostic variables predictive of mortality in patients with an exacerbation of COPD admitted to an intensive care unit (6). Prognostic variables associated with intermediate- term mortality were low Glasgow Coma Scale (GCS) on admission to ICU, cardio-respiratory arrest prior to ICU admission, cardiac dysrhythmia prior to ICU admission, and length of hospital stay prior to ICU admission and higher values of acute physiology scoring systems. Premorbid variables such as age, functional capacity, pulmonary function tests, prior hospital or ICU admissions, body mass index and long-term oxygen therapy were not found to be associated with intermediate-term mortality nor was the diagnosis attributed to the cause of the exacerbation.

Lessons learnt

In this case the negative prognostic markers were the respiratory arrest and the episodes of coma during this hospital stay and that the patient had already in hospital for more than 3 days. It would appear inappropriate and lacking in evidence to assume that patients admitted to the emergency department or acute medical unit with an exacerbation were not candidates for admission to the intensive care unit.

References

1. Connors A, Dawson N, Thomas C et al. Outcomes following acute exacerbation of severe chronic obstructive lung disease. The SUPPORT investigators (Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments). Am J Respir Crit Care Med 1996; 154: 959-67.
2. Wildman MJ, Sanderson CFB, Groves J, Reeves BC, Ayres JG, Harrison D, et al. Survival and quality of life for patients with COPD or asthma admitted to intensive care in a UK multi- centre cohort: The COPD and Asthma Outcome Study (CAOS). Thorax 2009; 64:128–32.
3. NHS.[http://www.nice.org.uk/nicemedia/live/13029/49425/49425.pdf].
4. Esteban A, Anzueto A, Frutos F et al. Characteristics and outcomes in adult patients receiving mechanical ventilation: a 28-day international study. Journal of the American Medical Association. 2002; 287(3):345- 355.
5. Nevins ML, Epstein SK. Predictors of outcome for patients with COPD requiring invasive mechanical ventilation. Chest. 2001; 119(6):1840- 1849.
6. Messer B, Griffiths J and Baudouin SV. The prognostic variables predictive of mortality in patients with an exacerbation of COPD admitted to the ICU: an integrative review. Q J Med 2012; 105:115– 126.