Intensive care is a means of delivering a higher level of physiological monitoring, organ support, therapeutic intervention, and nursing care than can routinely be delivered on general wards [1]. Patients are acutely ill and have deteriorated, or are expected to deteriorate, as a consequence of their presenting illness. Without intensive interventions their recovery may be compromised and their risk of death significantly increased. In some cases, there is an acute severe illness, such as pneumonia, in a previously healthy patient [12]. Because of the severity of the illness, the patient is at high risk of dying but has the potential to recover with high-intensity care in the ICU. Under these circumstances, most patients will want to have ICU level care. In many cases, an acute crisis occurs in the course of chronic progressive lung disease. A patient with irresectable lung cancer may become acutely ill with a pulmonary embolism, major hemoptysis, or pneumonia [13]. The immediate problem is treatable, although life expectancy from the underlying cancer may be limited. Similarly a patient with cystic fibrosis or advanced bronchiectasis may suffer a major hemoptysis or pneumothorax causing an acute crisis [14]. Aspiration pneumonia may occur in a patient compromised by neuromuscular disease and chronic respiratory failure. Acute exacerbations occur in the course of many chronic lung diseases such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, or fibrotic lung disease [8,14–17]. The decision to admit the patient to ICU should be on the basis that the deterioration is due to a reversible or at least partially recoverable process. These are complex decisions for the patient, the family, and the clinical team and it can be difficult to incorporate such acute crises into advance care planning as patients who may wish to be at home if they are dying may also want to have intensive treatment if there is a reasonable prospect of recovery. In some cases, the deterioration is due to progression of the underlying disease and there may be no identifiable reversible cause. Thus the outcome for patients with idiopathic pulmonary fibrosis admitted to ICU for respiratory support is generally poor unless a reversible complication is present [16,17].

There are several scoring systems used to try to predict which patients are unlikely to benefit from ICU level care, such as the APACHE score (acute physiology and chronic health evaluation). However, such scoring systems have substantial limitations and do not accurately predict the outcome in an individual patient [18]. Poor prognostic features include the absence of a reversible cause for the deterioration, diminished preceding functional reserve with impairment in activities of daily living, additional disease in other organ systems, and the development of multi-organ failure.

ICU care is inherently intrusive and burdensome, and some patients with advanced chronic lung disease may not wish to undergo ICU care, particularly if their deterioration is likely to indicate a progression of the underlying disease rather than a reversible complication. Failed ICU care under these circumstances may impose additional suffering and detract from the end of life experience of both the patients and their families [19]. Admission to ICU before death in the face of known poor prognosis may represent poor clinical judgment and decision making. Some studies raise concerns that patients being admitted to ICU may not have had comprehensive honest information about their prognosis and may not have had discussion of palliative care as an alternative [20]. Decisions to escalate to ICU level care often have to be made quickly and there is sometimes reluctance on the part of physicians to discuss the limitations of ICU care and the likely prognosis.

In some circumstances, it may be appropriate to set a “ceiling of care” whereby there is a trial of treatment and ICU support to reverse the disease process but with a recognition that if treatment fails or additional multi-organ complications occur ICU care should rapidly transition to focus on palliative end of life care. Ideally for many patients with chronic lung disease advanced care planning should have already addressed the patient’s wishes. In practice the patient and family may find it difficult to decide in advance, particularly when an acute crisis changes the situation. Further discussions will be needed at the time of crisis. Discussion of prognosis and the patient’s wishes and expectations are an important part of routine consultations in patients with progressive respiratory disease. Sometimes such discussions can be particularly complex, such as in the case of patients with advanced cystic fibrosis who may be close to death but hoping for a rescue lung transplantation [21]. Under these circumstances, palliative measures and some end of life discussions are still appropriate even where the disease trajectory may be dramatically altered by transplantation.

When a patient is admitted to hospital, early involvement of the ICU team may help in the discussion of the role and limitations of ICU care. There is a developing concept in ICU medicine of “care without walls” whereby the ICU setting is only part of a continuum of care for critically ill patients [1]. “Critical care outreach” involves the ICU team seeing patients on general wards and emergency departments so that there is early discussion of the role of ICU level care. The ICU team can support physicians in delivering care on medical wards and in deciding on the appropriateness of escalating care to the ICU setting. It should be recognized that high-intensity interventions are, of course, not confined to the ICU setting. Some patients with chronic respiratory failure receive long-term non-invasive ventilation at home. Patients with cystic fibrosis frequently receive high-intensity interventions at home including gastrostomy feeding and intravenous antibiotics administered via central venous access devices. Patients recovering from critical illness may be transferred from the ICU to “step down” care on a respiratory ward with post-ICU support from the “critical care outreach” team, particularly if the patient is receiving non-invasive ventilation or requires care of a tracheostomy. Patients and their families may be concerned at a change from a high level of staffing, such as one-to-one nursing, on the ICU to a lower level of staffing and support on a general ward. Many patients recovering from critical illness need ongoing rehabilitation, including psychological support, in recovering from the trauma of an acute illness. ICU follow-up clinics are being developed to manage the many long-term physical and psychological complications arising from critical illness, such as neuromyopathies, post-extubation airway problems, cognitive syndromes, and psychological problems, such as post-traumatic stress disorder.

There are substantial differences in how ICU level care is delivered in different countries and different hospitals [1]. It is increasingly recognized that intensive care is an applied principle and does not have boundaries and is not confined to the ICU setting [22]. When a patient’s condition necessitates admission to the high-technology ICU environment, with care delivered by a specialist ICU team, this should not be to the exclusion of the parent team, who should continue to be involved with both the patient and the family, particularly where long-term relationships may have already been established.

Critical illness is often associated with distressing symptoms such as pain, breathlessness, and anxiety [3–6]. The ICU setting is frightening for the patients and their families with high-technology equipment, noise from monitors, high levels of activity and bright lighting with some loss of day-night cycles. ICU interventions are inherently intrusive and burdensome. Nowadays ICU teams routinely include palliation of symptoms and distress in their overall care plan. It is important to be vigilant for specific symptoms such as pain, agitation, delirium, and distress [10,11,23]. Scoring systems, such as 10-point scales, may be used to quantify such symptoms and to assess the response to treatments with sedative and pain-relieving medications. Particular attention is needed with interventions that are known to cause distress and pain, such as endotracheal intubation, insertion of central venous or urinary catheters, insertion of nasogastric tubes and suctioning of the airway [24]. Other procedures, such as turning the patient in bed, have also been identified as causing particular distress. There are often difficulties in assessing symptoms in patients in ICU as many have an impaired level of consciousness and difficulties in communicating their needs when on mechanical ventilation with sedation [2–5]. Many studies show that these patients have distressing symptoms that may be underestimated by the clinical team. Sleep disturbance can lead to disorientation and delirium, and efforts should be made to provide some day-night cycle with reduced lighting and use of clocks to help to orientate the patient in time. Delirious patients often subsequently report having had delusions of being kidnapped and subjected to harm. Symptom control, relief of distress, explanation, and reassurance are of paramount importance throughout the whole process of ICU care [24].

Opioids are the main drugs used for relief of pain because of their powerful analgesic effect with additional beneficial sedative and anxiolytic effects [10,11]. Benzodiazepines help to relieve agitation and have additional useful amnesic properties, but need to be used judiciously, as sedation can be associated with increased morbidity and mortality [25]. Frequent visits by the family are often helpful in reassuring the patient, and the family should be encouraged to inform the ICU staff if they observe anything that they perceive as discomfort in the patient.