CWOCN Exam

Expect scenario items that hand you an ABI reading, a Braden subscale profile, a set of lab values or a description of a lesion and ask what it means, what the etiology is most likely to be, or what you should assess next. The chapters move from skin structure and healing physiology, through the history and diagnostic workup, to each major wound etiology, the lower extremity exam and the rules for detecting infection and obtaining cultures.

This chapter reviews the structure and functions of the skin, how wounds heal, the difference between partial-thickness and full-thickness repair, what makes a wound chronic, and the intrinsic and extrinsic factors that speed or stall healing. Every later decision about staging, dressings and prevention rests on these basics.

The skin is the largest organ of the body. It protects against microorganisms, chemicals and mechanical injury; regulates temperature through sweat and blood flow; prevents water loss; senses touch, pressure, temperature and pain; synthesizes vitamin D; and contributes to body image and communication. A healthy surface is slightly acidic (pH about 4.5 to 5.5), the so-called acid mantle, which discourages bacterial overgrowth. Alkaline soaps raise the pH and weaken this defense.

The epidermis is the thin, avascular outer layer. It receives nutrients by diffusion from the dermis. From deep to superficial its layers are the stratum basale (dividing keratinocytes and melanocytes), stratum spinosum, stratum granulosum, stratum lucidum (only on palms and soles) and the stratum corneum, a layer of dead, flattened, keratin-filled cells that forms the main barrier. Langerhans cells in the epidermis provide immune surveillance. Turnover from basal layer to shedding takes roughly four weeks in younger adults and lengthens with age.

The dermis lies beneath the epidermis and is joined to it by the dermal-epidermal junction, a wavy interface of rete ridges and dermal papillae that resists shearing. The dermis has a thin papillary layer and a thicker reticular layer. It contains collagen (strength), elastin (recoil), fibroblasts, blood and lymph vessels, nerve endings, hair follicles, sebaceous glands and sweat glands. Because hair follicles and glands are lined with epithelial cells that extend into the dermis, a partial-thickness wound can resurface from these islands as well as from its edges.

The hypodermis (subcutaneous tissue) is made of adipose and connective tissue. It insulates, stores energy and cushions underlying muscle and bone. It is poorly vascularized compared with muscle, which matters in pressure injury: deep tissues near bone can be damaged before the surface shows much change.

Skin Layers and Clinical Relevance

Older adults have a thinner epidermis, a flattened dermal-epidermal junction (so layers separate easily under friction and shear, producing skin tears and blisters), less collagen and elastin, fewer blood vessels, reduced sebum and sweat production (dry skin), slower cell turnover, reduced sensation and a weaker inflammatory response. Neonates, especially preterm infants, have a thin stratum corneum, higher transepidermal water loss and greater absorption of topical agents. Both extremes of age therefore need gentle cleansers, minimal adhesives and protection from friction.

Acute wound healing moves through four overlapping phases. The time frames are approximate and vary with patient factors.

Phases of Wound Healing

The macrophage is the key cell of the inflammatory phase because it directs the transition to repair through growth factors. Healthy granulation tissue is beefy red, moist and granular; pale or dusky granulation suggests poor perfusion, and bright red friable granulation that bleeds easily suggests infection or critical colonization. Epithelialization requires a moist, viable surface; epithelial cells migrate across the wound bed only about 3 cm from the edge, which is one reason large wounds need grafts or advanced therapies.

Memory Aid: "Help In Proper Mending" for Hemostasis, Inflammation, Proliferation, Maturation.

Partial-thickness wounds (limited to epidermis and part of the dermis) heal by regeneration: epithelial cells migrate from the wound edges and from hair follicles and glands. They usually heal quickly and without scar. Full-thickness wounds (through the dermis into subcutaneous tissue or deeper) heal by repair: granulation tissue fills the defect, the wound contracts, and epithelium covers the surface last. The result is scar tissue without hair follicles or glands.

A chronic wound fails to progress through the healing phases in an orderly and timely way, often stuck in prolonged inflammation with high protease levels, senescent cells and biofilm. A practical benchmark: if the wound area has not decreased by about 40% after 4 weeks of appropriate care (some sources use 30-50%), reassess the diagnosis and the plan.

Worked example of percent area change: a venous ulcer measures 4.0 cm long by 3.0 cm wide at baseline, an area of 12.0 square cm. After 4 weeks of compression it measures 3.0 cm by 2.5 cm, an area of 7.5 square cm. The reduction is 12.0 minus 7.5, which is 4.5 square cm. Divide 4.5 by 12.0 to get 0.375, a 37.5% reduction. That falls short of about 40%, so the WOC nurse should reassess: Is compression adequate and worn? Is there arterial disease, infection, biofilm or an atypical etiology needing biopsy?

Exam Tip: Length times width overestimates true area for irregular wounds, but it is consistent and acceptable for tracking. Always measure the same way, using head-to-toe length and perpendicular width, and compare like with like.

Factors are often grouped as intrinsic (within the patient) and extrinsic (from the environment or care).

Factors That Delay Healing

Smoking deserves special mention: nicotine causes vasoconstriction, carbon monoxide reduces oxygen carrying, and smoking impairs leukocyte function. Cessation is recommended for every wound patient who smokes.

Common Trap: Assuming a chronic wound is not healing because of the dressing. The exam usually wants you to look for an uncorrected cause (unrelieved pressure, unaddressed venous hypertension, poor perfusion, uncontrolled glucose, infection) before changing products.

Exposed dermis means partial-thickness loss; visible fat means full-thickness; exposed or palpable fascia, muscle, tendon, cartilage or bone means Stage 4 depth.

Healing phases: hemostasis, inflammation (about days 1 to 4-6), proliferation (about day 4 to week 3), maturation (up to 1-2 years; scar reaches at most about 80% tensile strength).

Partial-thickness wounds regenerate; full-thickness wounds heal by granulation, contraction and epithelialization.

Less than about 40% area reduction after 4 weeks of good care signals the need to reassess the diagnosis and plan.

Correct perfusion, glucose, nutrition, infection and mechanical causes before blaming the dressing.