Firstly, I would like to thank Drs A. Esquinas and C. Zamarro for their comments on our paper.1

The ageing of the population is a current reality. On a worldwide level, it is estimated that by 2050, around 2 billion people will be over 60 years of age.2 This phenomenon will be more acute in countries such as Spain, Italy and Japan. Ageing in itself is not a disease state, but fragile individuals are likely to be more susceptible to a series of comorbidities.3

This situation means that specific strategies for acute respiratory failure in the elderly must be implemented and, above all, we should further develop our understanding of the patients who would benefit most from non-invasive mechanical ventilation (NIMV).

In response to the questions raised by Drs Esquinas and Zamarro:

• 1.

  In our study, 65% of the patients had a “do not intubate” (DNI) order. The main reason for signing the DNI orders was the patients’ underlying situation and advanced stage of disease. While no guidelines are currently available for placing a patient on a DNI order, the decision is made by the treating pulmonologist in the Respiratory Monitoring Unit (RMU) or the on-duty pulmonologist, and, in the large majority of cases, agreed with family members after they have been informed of the patient's clinical situation.

  At present, our group is performing a study in patients on a limited treatment plan (LTP), in an attempt to define the characteristics of this population, and our aim is publish these data shortly. In general, according to the preliminary data, we limit therapeutic intervention in patients who are more highly dependent (as determined using the Barthel index), those with more comorbidities and those of more advanced age.

• 2.

  We agree that heart failure had an impact on mortality and was one of the reasons why mortality was higher than that in other series which included more patients with a diagnosis of chronic obstructive pulmonary disease (COPD).4

  In our analysis, patients with COPD with a worse prognosis during their hospital stay had lower pH levels and higher PaCO2 levels. They also had higher C-reactive protein levels (P<.008) and a higher percentage of neutrophils (P<.009). Other factors increasing the relative risk (RR) of readmission in this group were home oxygen therapy on discharge (RR=1.65; 95% confidence interval [95% CI], −2.62 to 5.92) and previous admissions with respiratory acidosis requiring NIMV (RR=2.18; 95% CI, 1.77–2.59). We did not specifically analyse any data on the underlying life situation of the patients, although we are developing a hypothesis on the possible impact of the patient's life situation on readmission.

• 3.

  In our experience, patients who required NIMV in subsequent readmissions were managed in the RMU under the same care protocol. With some exceptions, when NIMV was initiated outside the RMU, the patient was transferred to this unit within 24–48h, depending on the availability of beds.

• 4.

  Any complications that the patients presented during their RMU stay, including cardiovascular and renal problems, were managed by the unit pulmonologist or the on-duty pulmonologist. If the patient required specialised care or if specific techniques needed to be performed, the case was discussed with the appropriate specialist. The application of specific techniques, such as dialysis in the case of renal failure or the use of biogenic amines, was limited on a case-by-case basis, after a multidisciplinary assessment of the patient and with the agreement of the patient and/or the family.

  With regard to your question on when NIMV should be limited, no data are currently available to support a clear answer. In our practice, we base the decision on clinical criteria and in accordance with the wishes of the patient and the family. The data from our ongoing LTP study will allow us to define more clearly the characteristics of the patients for whom the decision is taken to limit treatment and reasons for coming to that decision. We believe that these data will help us to plan larger studies and establish action guidelines.

• 5.

  Home mechanical ventilation (HMV) is prescribed for COPD after a second admission with respiratory acidosis and hypercapnia. In this subgroup, HMV was a protective factor against readmission (RR=0.76; 95% CI, 0.35–1.17).

• 6.

  We have not carried out a cost-efficacy analysis, so we cannot provide any specific data in that respect. According to data from other studies, a bed in a RMU is cheaper than an intensive care unit bed.5 Thus, the use of specialised units which shorten hospital stay and reduce complications should entail a reduction in costs. In any case, this would be an interesting basis for a future study that might confirm this supposition.

In conclusion, we agree on the need for the creation of specific spaces for the application of NIMV and for multidisciplinary protocols, both during admission and on discharge, aimed specifically at the elderly population.