Would you be happy if a member of your family was in a hospital ward where there was only one doctor to every 100 patients?

On the face of it, such a ratio on the nightshift sounds worrying, like a gamble not worth taking with patients' health. What's more the figures have emerged just a few weeks after junior doctors at St John Hospital in West Lothian complained that the staffing levels they were expected to work with were unsafe. As part of The Herald's NHS: Time for Action campaign, staff have also told us some hospitals in Scotland are narrowly avoiding a crisis situation most days.

However, as the president of the Royal College of Physicians in Edinburgh, Dr Neil Dewhurst, points out, the ratio of 100 to 1 has existed in some Scottish hospitals for around 10 years now. Indeed, in some places, it is higher, in others much lower. There is also little evidence about what is, and is not, a safe level of staffing at night. Some nights, a ratio of 100 to one may be manageable, provided of course that everything goes according to plan which, as we know, rarely happens in hospitals.

The point is that the variation in the doctor-nurse ratio is far too great for a health service that seeks, in principle at least, to offer the same service to patients across the country. Stay at Aberdeen Royal Infirmary, for example, and you will be one of 65 patients per doctor; stay at the Royal Alexandra Hospital in Paisley on the other hand and it will be double that. More research is needed in this area, but the figures suggest some patients are receiving a worse service than others.

We should also be concerned about the effect these staffing levels are having on the doctors and nurses. In some cases, a ratio of 100 to one can leave doctors to cope in a system that is working, just about, but is very close to the bone. All it takes is for a staff member to be absent at the last minute for the wards to be plunged into crisis and the patient to doctor ratio to shoot up. Not only does it leave junior doctors stressed and tired, patients can be left waiting for long periods to be seen.

Clearly, hospital rotas are being run in this way because the right staff cannot be found to fill posts or there is no budget to increase staff numbers, but there must be enough capacity in rotas to allow for unexpected events. Dr Dewhurst of the Royal College of Physicians says the patient/doctor ratios suggest this is not happening and there may not be such capacity to cover a high level of unplanned care. Providing such cover is essential for the wellbeing of patients and staff.

There is an important caveat, however: doctor to patient ratios do not reflect the fact that the nature of staffing has changed in hospitals in recent years. More and more, the wards are staffed not only by junior doctors but also highly-trained, advanced nurse practitioners who play a key role in ensuring that patients get the care they need. It means looking at how many doctors are on shift at any one time does not tell the whole story.

Even so, there is some cause for concern in these patient-doctor ratios, not only in the wild variation across the country, but also in the signs that some wards are sailing dangerously close to the wind. You probably could leave a member of your family on such a ward and everthing would be fine - the point is you would never know what a close run thing it was.