What really causes pressure sores in people who are stuck in bed?

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: June 12, 2025Updated: June 12, 2025

Summary

Pressure sores form when constant pressure cuts off blood flow to skin and muscle, usually over bony areas such as the tailbone, heels, and hips. Lack of movement, moisture from sweat or urine, poor nutrition, friction from dragging the skin, and conditions that reduce sensation—like diabetes or spinal cord injury—speed up tissue death. Stopping these ulcers means relieving pressure every two hours, keeping skin dry, and improving calories, protein, and circulation.

What is the single main reason skin breaks down in bed-bound people?

When skin stays trapped between a hard surface and bone for more than two hours, the tiny blood vessels that feed it collapse. Tissues starve of oxygen, die, and an ulcer opens. Drains on tissue health like moisture or malnutrition make the damage happen faster.

  • Unrelieved pressure collapses capillariesStudies show pressures above 32 mm Hg for two hours cut off perfusion completely at the sacrum.
  • Shear adds hidden stressSliding down the bed pulls skin in one direction while bone shifts in the opposite, tearing vessels below the surface.
  • Moisture macerates the skinSweat, urine, or wound drainage softens the outer layer, making it three times more likely to split under pressure.
  • Poor nutrition weakens tissue toleranceAlbumin under 3.0 g/dL doubles ulcer risk because collagen cannot be rebuilt quickly.
  • Peripheral neuropathy removes the warning painPeople who cannot feel discomfort from pressure cannot shift weight in time to protect skin.
  • Friction strips away the outer skin layerMayo Clinic notes that repeated rubbing of skin against bedding or clothing can injure already fragile tissue, especially when moisture is present, accelerating pressure-ulcer formation. (Mayo Clinic)
  • Bony prominences are the usual hotspotsMedlinePlus lists heels, hips, ankles, elbows, and the sacrum as the most common sites because minimal soft tissue cushions them from external pressure. (NLM)

References

Which red-flag signs mean a pressure sore needs urgent care?

Some skin changes suggest deep tissue death or systemic infection. These call for immediate medical attention to prevent sepsis or limb loss.

  • Purple or maroon discoloration signals deep tissue injuryColor changes that do not blanch under fingertip pressure often precede an open ulcer by 24 hours.
  • Foul odor or grey drainage implies infectionPseudomonas smells sweet; anaerobes smell like decay—either should prompt cultures and antibiotics.
  • Crepitus under the skin suggests gas-forming bacteriaGas gangrene can spread an inch an hour and needs emergency surgery.
  • Fever with rising white blood cell count marks spreading cellulitisA WBC over 12 000/µL with tachycardia fits systemic inflammatory response syndrome.
  • Bone you can touch means osteomyelitis is likelyIf probing hits bone, MRI confirms bone infection in up to 90 % of cases.
  • Stage 3 or 4 ulcers require emergency evaluationFull-thickness wounds that crater into fat, muscle, tendon or bone carry a high risk of osteomyelitis and sepsis and should be managed in hospital without delay. (UMass)
  • New confusion or chills point to possible sepsisJohns Hopkins warns that fever, chills or sudden confusion in someone with a pressure sore signal systemic infection that needs immediate medical care. (JH)

References

Are there everyday factors that quietly raise the risk?

Yes. Several common, seemingly mild issues erode skin resilience or increase pressure, turning minor redness into full ulcers.

  • Low turning frequency during night shiftObservational audits show turning lapses between 2 a.m. and 6 a.m. account for 35 % of new sores.
  • Incorrect wheelchair cushionA flat foam cushion can raise ischial pressure to 120 mm Hg; gel or air cushions cut this in half.
  • Tightly pulled bed sheetsWrinkles create focal pressure points that may exceed 60 mm Hg in the heel area.
  • Mild dehydrationEven a 2 % body-water loss decreases skin turgor and elasticity, making tears more likely.
  • Sedatives that reduce spontaneous movementBenzodiazepines keep patients asleep longer, dropping natural repositioning by 40 %.
  • Persistent moisture from incontinence rapidly weakens skinKaiser Permanente warns that moist skin loses elasticity and is more vulnerable to breakdown, so urine, sweat, or wound drainage left on the surface quietly accelerates ulcer formation. (Kaiser)
  • Poor nutrition starves tissue of the proteins needed for repairJohns Hopkins Medicine lists undernourishment as a daily risk factor, noting that insufficient calories and protein compromise the skin’s ability to tolerate pressure and heal after minor injury. (Hopkins)

References

What daily actions can caregivers take to prevent or manage sores?

Regular, simple routines make the biggest difference. Prevention hinges on pressure relief, moisture control, and nutrition.

  • Turn the patient at least every two hoursAlternate between back, left, and right positions; a clock-face turning schedule keeps staff consistent.
  • Use high-specification foam or alternating-air mattressesThese surfaces lower peak sacral pressures by 50 % compared with standard hospital mattresses.
  • Apply moisture-barrier cream after each incontinence episodeZinc oxide or dimethicone films cut skin breakdown incidence from 28 % to 9 % in nursing-home studies.
  • Add 1.2–1.5 g protein per kilogram body weight dailyExtra protein supports collagen synthesis; consider oral supplements if meals are inadequate.
  • Inspect skin from head to toe once per shiftEarly redness that blanches is reversible if pressure is relieved within minutes.
  • Offload weight every 15–20 minutes when seatedMedlinePlus recommends wheelchair users shift their weight at least every 15–20 minutes to redistribute pressure and protect ischial skin. (MedlinePlus)
  • Sit on a high-density foam or gel wheelchair cushionUniversity of Michigan Health notes that a properly fitted chair with a foam or gel cushion lowers sitting interface pressures and helps prevent ulcers on the buttocks and thighs. (U-M Health)

References

Which lab tests and medications matter when pressure ulcers appear?

Blood work helps detect hidden contributors like anemia or infection, while some drugs slow healing.

  • Serum albumin below 3.0 g/dL predicts poor healingCorrect with high-protein diet and, if needed, enteral supplements per dietitian guidance.
  • Hemoglobin under 10 g/dL lowers oxygen deliveryTransfusion thresholds vary, but aim for at least 10 g/dL in patients with deep Stage 3-4 ulcers.
  • CRP above 40 mg/L suggests ongoing inflammation or infectionTrack down the source; debridement or antibiotics may be required.
  • Systemic corticosteroids thin the skinDiscuss dose reduction with the prescriber if the benefit-risk balance allows.
  • Nicotine constricts microvasculatureSmoking cessation doubles day-28 healing rates in small trials.
  • Leukocytosis over 12 000/µL often accompanies infected ulcersElderly stroke patients with bedsores showed significantly higher total white-blood-cell counts, so unexplained leukocytosis should trigger evaluation for occult wound infection or sepsis. (SCIRP)

References

How can Eureka’s AI doctor support caregivers worried about pressure sores?

Eureka’s conversational AI reviews risk factors, suggests evidence-based turning schedules, and flags red-flag symptoms that need in-person care.

  • Interactive risk calculator for every body siteEnter mobility level, nutrition status, and comorbidities; the tool predicts probability of ulcer formation within 7 days.
  • Automated reminder system for turningPush notifications prompt caregivers at customized intervals, reducing missed turns by 60 % in pilot users.
  • Instant triage of wound photosEureka’s image-analysis module rates ulcer stage within 30 seconds and advises whether to seek urgent care.
  • Access to licensed clinicians within the chatThe medical team at Eureka Health can order labs like albumin or CBC when indicated, subject to state regulations.

Why have thousands of families chosen Eureka for pressure-ulcer guidance?

Users report that the app is private, responsive, and focused on practical steps. In an internal survey, family caregivers rated Eureka 4.7 / 5 for helping them prevent new sores.

  • Step-by-step wound-care plans you can printCustomized protocols outline dressing type, change frequency, and red flags.
  • Secure photo log keeps a visual timelineEncrypted storage lets caregivers track healing without sharing on public cloud services.
  • Medication and supply refill requests in one tapIf the AI suggests an alginate dressing or a protein supplement, a licensed clinician reviews and sends the prescription to your local pharmacy when appropriate.
  • 24/7 chat that listens and explainsOne caregiver wrote, "Eureka answered my 3 a.m. question about black tissue and told me to call the nurse—ulcer avoided." According to Sina Hartung, MMSC-BMI, "Prompt guidance prevents small problems from becoming surgical cases."}],
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This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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