Hydrogel dressings in the British Journal of Midwifery

nurse-with-clipboardA few weeks ago, I talked about a ‘clinical case study’ posted on a medical supply manufacturer’s website, apparently demonstrating the benefits of using hydrogel dressings when breastfeeding. Unfortunately, the study was poorly designed, and therefore unable to provide support for its considerable claims. It showed, at best, that the dressings did not appear to cause any major problems for a small group of women.

Since then, the dressings have been tested in a larger, controlled study, published in the British Journal of Midwifery1. The article, which describes the dressings as ‘designed to physically protect wounds while maintaining a moist environment,’ concludes that, ‘the dressings can reduce the pain and discomfort associated with nipple excoriation.’ This rhetoric sounds pretty impressive – but does it accurately reflect the strength of the evidence?

On the surface, the study appears to be well designed and reported: 64 mothers were randomly assigned to either the experimental group (wearing dressings between feeds) or the control group (rubbing breast milk on the nipple after a feed), and self-reported pain scores were recorded in interviews 5 times over 14 days. If you read the article carefully, however, a number of inconsistencies become apparent. The abstract and ‘study objectives’ sections say that the aim of the study was to compare the dressings with ‘breastmilk expression and patient education (control group).’ We learn later that in fact both groups received education. The study hypothesis was that, ‘the dressings may reduce nipple pain and excoriation.’ While excoriation (skin wounding/abrasion) is mentioned several times, it was never actually measured – or if it was, the results are not reported.

That the dressings resulted in ‘a considerable reduction in pain’ is highlighted in a special ‘key points’ box. In fact, pain was significantly lower in the dressings group on only one occasion – day 12. The results section states that the average score for the dressings group on this day was 1.3, compared to 2.0 in the control group, and refers you to a graph showing how the scores declined over time. Confusingly, this graph shows the control group score on day 12 not as 2.0, but as 1.4. Clearly, one set of figures is wrong. Given the gradual downward trend of both sets of scores, it would be pretty odd if a pain score went from 1.4 two days previously, to 2.0 (the highest score, recorded at the start of the study), and back down to 1.4 two days later. It seems more plausible that the figures are misreported in the text, and that the statistical tests were in fact conducted with errroneous data. ‘Comfort scores’ are also reported to be consistently lower in the dressings group, although it is not completely clear what these are. They are not mentioned in the method section, and are described in the results section as ‘acceptance of the treatment’ measured using the 1-5 verbal descriptor pain scale. This is the same scale used to measure the other pain score, and how the two actually differ is not explained. Again, the graph and text do not match. The text says that comfort was recorded on days 3, 5, 10 and 12, but the graph also shows data for this measure on days 7 and 14. Interestingly, days 3, 5, 10 and 12 result in comfort scores of 1.0 for the dressings, whilst 7 and 14 show the scores as 1.2 and 1.4 respectively – is it possible these higher scores were conveniently excluded from the analysis?

There are other examples of sloppiness that call into question the integrity of the research. In the introduction, a paper is cited as saying that nipple pain typically starts to decline by day 12. In fact, the study reported in this paper only lasted 7 days2 (this same error occurs in the ‘clinical case study’ reported on the manufacturers website – one can only assume the authors copied the reference without actually bothering to check it). We are told 11 participants dropped out of the study, but not which group they belonged to (they could all potentially have been using the dressings). It is also not clear why 30 people were ‘randomized’ to the dressings group, and 34 to the control group. Why not have 32 in each? A presentation at the International Lactation Consultants’ Association (ILCA) Conference describing the study in progress stated there were 30 women in each group3; why the control group then increases by 4 (unbalancing the design) is a mystery. This presentation also said that breastfeeding duration was being analyzed. Why is this data not provided?

Given that these less than convincing results are reported with great enthusiasm, you would be forgiven for thinking that this might simply have been a promotional exercise. And that, of course, is precisely what it is. Although it is described as ‘sponsored’ research, and discretely labeled as a ‘product focus’, it is not a study that would ever have been published with a negative result.

If you ignore the problems with the figures, and simply take the data at face value, it is possible that the dressings may have provided increased ‘comfort’ for some women. The difference between the scores of the two groups is less than a point, however, and could conceivably be down to experimenter bias, as the investigators conducting the study may have been keen to obtain a positive outcome for their sponsor. Even if the effect is genuine, it certainly does not translate into the substantial support for the dressings claimed in the article. The dressings are marketed as having moist wound healing properties, and although these are alluded to frequently, they are never actually tested. Previous research has shown that hydrogel dressings do not help nipple wounds to heal more quickly when women are breastfeeding, and may potentially foster infection4. When you consider it in this context, what initially appears to be genuinely useful research, may in fact be harmful propaganda.

  1. Br J Midwifery. 2004 Apr;12(4):244-248.
  2. Nurs Res. 1995 Nov-Dec;44(6):347-51.
  3. J Hum Lact 2004; 20; 211.
  4. Arch Pediatr Adolesc Med. 1998 Nov;152(11):1077-82.

Should ‘moist wound healing’ principles be applied to cracked nipples?

pot-of-vaselineMaintaining a slightly damp, rather than dry, environment under a dressing has been shown in many studies to help wounds heal faster. Moisture prevents a scab from forming, which allows new epithelium cells to move across the surface of the wound more quickly, and reduces the time it takes it to close1.

As the technique appears to improve the healing rates of a range of skin lesions2, it has been suggested that its benefits may extend to cracked nipples3, and there are now several off-the-shelf creams and dressings that claim to maintain a moist environment, and thus help the healing process. The inference is not, at first glance, unreasonable – if moisture helps skin to regenerate more quickly, then it may well help injured nipples to recover too. It is important to remember, however, that nipples are subject to a unique set of circumstances when a mother is breastfeeding, so it is also quite possible that the application of the technique might not be appropriate. Is there any scientific evidence that applying moist wound healing principles can aid the recovery of cracked or injured nipples?

In a study comparing dressings made from hydrogel with lanolin (both classified by the Breastfeeding Network as having ‘moist wound healing’ properties)4, 106 mothers were allocated at random to one of two groups: the first was given hydrogel dressings to use between feeds; the second was given lanolin cream. Mothers started using the treatments within 24 hours of giving birth, and their effectiveness was assessed via telephone interviews 3, 4 or 5, 7, 10 and 12 days later. The researchers found mothers reported significantly lower pain scores (a difference of just under 1 point, on a scale of 1-5) in the hydrogel group on days 10 and 12.

There were a couple of problems with this study (actually, there were several, but I’ll limit it to the major ones). Firstly, there was no baseline group of mothers not applying anything to their nipples, so it is not possible to say whether either treatment was better than simply leaving nipples alone. A second issue is that the people conducting the interview were aware, when they spoke to the participants, which treatment they were receiving. The researchers claim that to have conducted the study blind would have been ‘impossible’, an unsubstantiated and somewhat odd statement, as it would appear to be completely possible to interview a mother over the phone without knowing what she had on her nipples. Knowledge of the treatment group in this type of study is a problem if there is any chance that the researcher may have a bias towards a particular treatment, as they may subconsciously influence the patients’ responses. It may be worth mentioning at this point that the research was funded by Tyco, the manufacturers of the dressings.

These criticisms are, however, a digression. The main thing to note about this research is that it did not test whether the dressings actually helped wounds to heal. Although moist wound healing is touted in the introduction as the ‘science bit’ justifying the use of the dressings, it is not mentioned anywhere in the procedure or the results.

A hospital-funded study comparing hydrogel and lanolin – this time documenting the impact that the treatments had on bleeding and cracked nipples – did not find the dressings to be quite so effective5. Researchers who were blind to the treatment group rated nipples as healing significantly better when women used lanolin with breast shells, rather than hydrogel dressings. Self-reported measures of pain were also significantly lower in the lanolin group. A final point worth mentioning is that the study was halted early, due to a third of the 21 women in the hydrogel dressing group developing an infection.

Although this study compared two treatments, it is again compromised by the lack of a proper control group. We can see that lanolin appears to result in improved healing and lower pain scores when it is compared with hydrogel, but we still do not have any evidence that moist wound healing techniques are useful for treating injured nipples when breastfeeding – to ascertain this requires a control group where mothers keep their nipples dry.

So far, there appear to be only two studies that have looked at this issue. An experiment published in 1995 examined whether using a polyethylene adhesive dressing had any effect on the development of nipple redness, fissures and pain6. 50 mothers took part in the study, using a dressing on one nipple, and leaving the other untreated. Although the mothers reported less pain when feeding with the treated nipples, the researchers caution that this may simply have been because of the ‘Hawthorne Effect’ (the mere fact there is an intervention is enough to cause an improvement.) The dressings made no difference to the development or healing of fissures or redness, as reported by observers blind to the treatment group. 16% of the participants dropped out due to finding the dressings uncomfortable, and 66% said they found it uncomfortable to remove them – something they had to do before every feed.

A more recent study looked specifically at the effect of lanolin on the healing of nipple fissures7. 225 women, all with fissures, were randomly allocated to one of three groups: in the first group mothers applied lanolin 3 times a day; in the second they applied breast milk after each feed; in the third they applied nothing. The appearance of their nipples was assessed 3, 5, 7 and 10 days after starting the treatment by researchers who did not know which group the mothers were assigned to. There was no significant difference in healing time between the breast milk and no-treatment groups. The nipples of the women using lanolin, however, took significantly longer to heal (45% of this group took longer than 7 days, as opposed to 32% of the milk group, and 25% of the no-treatment group).

There is another area of research, which does not examine the use of moist wound healing directly, but is still relevant to the debate. Broken skin makes nipples vulnerable to infection8, which may mean there is an additional problem with keeping nipples damp, rather than dry: organisms like thrush are known to thrive in warm, moist environments9.

Given the possible risk of infection, and the evidence that maintaining a moist environment around cracked nipples may potentially delay the healing process, it seems to unwise to recommend the application of the products described above to mothers with cracked or fissured nipples. In spite of this, they continue to be promoted by both commercial companies and health professionals on scientific grounds. Until evidence that genuinely supports its use is found, presenting moist wound healing to mothers as a clinically tested treatment is at best misguided, and at worst dishonest.

  1. Nature. 1962 Jan 20;193:293-4.
  2. Br J Nurs. 2008 Aug 14-Sep 10;17(15):S4, S6, S8 passim.
  3. J Hum Lact. 1997 Dec;13(4):313-8.
  4. J Obstet Gynecol Neonatal Nurs. 2003 Jul-Aug;32(4):486-94.
  5. Arch Pediatr Adolesc Med. 1998 Nov;152(11):1077-82.
  6. Nurs Res. 1995 Nov-Dec;44(6):347-51
  7. Saudi Med J. 2005 Aug;26(8):1231-4
  8. J Hum Lact. 1991 Dec;7(4):177-81.
  9. Hum Lact. 1999 Dec;15(4):281-8.
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