• The dimensions of length and width of the wound will be considered first.  Measuring length and width of a wound to calculate its area sounds simple except that very few wounds are perfect rectangles (skin graft donor sites are the closest).  Most wounds are irregular in shape and it may be confusing to determine what to call the length and what the width. 
• The general convention in measuring wounds is to locate the longest axis or diameter of the wound and assign this axis as the LENGTH - some references suggest measuring the longest axis in the head- to -toe direction; however this can be confusing depending on the location of the wound and may also lead to inconsistencies.  This method may also lead to “widths” that are larger than the “lengths” which is not standard.  Therefore, selecting the longest axis as the length of the wound, regardless of its orientation is the current standard.  The measurement should be made in units of centimeters.  If as the wound heals, the direction of the longest axis changes, that is not a problem - just select the longest axis at each assessment.
• Once the length has been identified, the width is determined by then locating the longest wound axis which is perpendicular to the length.
• Multiplying these two values will give you the approximate area of the wound.  It may slightly overestimate the area because wounds are not rectangles but it has been shown to be a reliable, consistent measurement when performed as described.

• Wounds do not heal only by becoming smaller in area - they also heal by becoming more shallow - in fact, a wound may get more shallow before it decreases in area.  If the only dimensions you measure are length and width, you may incorrectly assume that healing is not progressing when the wound is actually filling up with granulation tissue.  Therefore depth measurement is an important aspect of wound assessment. 
• When a wound is very superficial - such as a minor abrasion - the depth may be very difficult to actually measure.  But because the skin is broken, you know there must be some depth dimension.  It is a general convention to estimate the depth of very superficial wounds as 0.1 cm (one millimeter) to indicate that the skin is not intact.  When there is appreciable depth, you must measure it.  And because wounds may have variable depth, it is usual to make your depth measurement at the deepest part of the wound.
• A method for depth measurement is illustrated next.
• You should not place a ruler into the wound to measure depth - you may create an additional injury with the edge of the ruler.  One method of measuring wound depth safely is to use a sterile, cotton-tipped applicator as illustrated in this slide.

• Step A:
• Take the applicator and place it gently into the wound so that the cotton tip just touches the wound base.  
• Now place a mark on the stem of the applicator at the level of the skin surface - or place your gloved finger at this spot (this is less precise that making a mark with a writing instrument).
• Step B:
• Once the level of the skin has been noted on the applicator stem, remove it from the wound and hold it up next to a ruler with a centimeter scale
• Note the distance from the end of the cotton to the mark.  This is the wound depth.

Undermining and Tunneling

Two characteristics that can complicate the assessment of wound dimensions are undermining and tunneling.  Undermining is an area of tissue injury that extends from the wound margins beneath intact skin and may exist completely around the wound circumference or some portion thereof.  Undermining is like a shelf or pocket.  Tunneling is similar in that it also involves tissue injury that extends form the wound margin beneath intact skin, but it is more limited in width - more like a tunnel or a tract.

• Undermining is common in sacral pressure ulcers  due to the shearing forces that are involved in the pathogenesis of the ulceration.  The wound photograph in this slide is an undermined wound.  The extent of the undermining has been noted on the intact skin with a surgical marking pen.
• Measuring the extent of undermining or tunneling is similar to measuring depth.  The next slide illustrates the method.

• The last aspect of the wound to be assessed and documented is the exudate (or drainage).  In general, wound exudate is highest during the inflammatory phase of healing and diminishes as the wound enters the proliferative phase.  However, many chronic wounds are also chronically inflamed and not progressing to the proliferative phase - so there are significant levels of wound exudate for a longer period of time.
• The features of wound exudate that we are interested in are the amount, the color, the consistency and the odor, if any.
• The color and consistency of wound exudate is a clue as to the bacterial status of the wound.  Normal exudate is clear yellow or serous and almost watery in consistency, with little or no odor.  Exudate right after a surgical or sharp debridement may be bloody or serosanguineous.  If the wound is infected, the exudate becomes thicker and more opaque.  Alternatively, the amount of exudate may increase significantly without a drastic change in color or thickness and this too is a sign of infection.  Odor is a sign of infection - certain bacteria have distinctive odors - like the sweetish odor of Pseudomonas.
• Documenting the amount of exudate is not only important to determining if the wound may be infected or heavily colonized with bacteria - the amount of exudate is often a criteria for the selection of a certain type of dressing.  If the exudate levels are decreasing, then it may be appropriate to switch to another type of dressing.  But assessing the amount of exudate might be difficult...