Doom Dome

We manage our ward work differently these days. Different from when I was a lad. We do blocks of time on the ward, looking after all the patients in the ward for those two weeks. It makes for a high intensity fortnight, not least because we look after all the patients in the high dependency unit.

We have a disproportionately high number of patients in the HDU, compared with other specialities. Even if patients go in there under a different speciality, they often develop respiratory complications, become our responsibility, and leave HDU under our care. I’m sure this is the case in lots of HDUs around the country, certainly those not looked after by the intensivists.

We have more to offer our patients with respiratory these days – high flow nasal oxygen, NIV and CPAP are used frequently. But their use leads to difficult decisions – what to do when a patient becomes dependent on CPAP.

CPAP masks are uncomfortable, patients don’t like wearing them, and often refuse to wear then again, making the decision to continue a straightforward one. But the CPAP hood, the dome that fits over the whole of the patient’s head, is far more comfortable, and better tolerated. So well tolerated that patients are happy to sit with the hood on all day. It’s now commonplace to be faced with the situation where a patient sits happily on the hood, but once it’s removed, even briefly, their saturations plummet, and the hood is put back on.

The hood-dependent patient is not easy to manage.

Before anyone is put on NIV a decision is made on ceiling of treatment, duration of treatment, criteria for withdrawal of ventilation. But CPAP is often nurse initiated, the decision to use it made by doctors in training, and does not come, perhaps, with the same thought as NIV. Faced with a hyperaemic patient overnight, the decision to put on the CPAP hood is easy for the overnight team – our ICU won’t usually come to see a patient until CPAP has been trialled, and failed, and for a patient who is ‘not for ICU’, CPAP can keep the patients well saturated until the morning ward round.

On my last couple of weeks on the ward, like most weeks looking after HDU, I had patients who had been put on the hood overnight. The registrar looked despondent. “No-one who goes on the hood ever gets better”, she said. She was right about the patients that week. The other registrars agreed – patients who go on the “Doom Dome” do not do well. But CPAP works, does’t it?

In 2004, as a research fellow, I went to the American Thoracic Society Conference in Orlando. One of the talks I went to was about the utility of CPAP in respiratory failure. The speaker showed very clearly that CPAP works. For pulmonary oedema. But for any other indication CPAP was of little use, or a holding measure prior to intubation and ventilation.

CPAP gets used a lot for management of respiratory failure associated with CAP. This study suggests the use of CPAP in CAP, but it’s only 3 patients! This more recent study, with 123 patients, shows that although patients receiving CPAP had better SaO2 readings, their outcome was no different. The BTS guidelines for management of pneumonia state that CPAP is not routinely indicated for management of respiratory failure due to CAP – evidence level A-. But we still do it. It’s nice when the numbers get better – we feel like we’re doing something. But we’re only treating the numbers.

So we’re left with those patients who are dependent on the hood, but with no realistic expectation that they’ll get better, and a difficult decision to make. We have the evidence, but do we ignore it? Or do we hope we can make it work on a case by case basis?

I suspect this is a problem that’s not going away.

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