Hard-to-heal wounds-those that fail to heal despite appropriate treatment-are a growing clinical challenge, often leading to significant discomfort, reduced quality of life, and high healthcare costs. These wounds are common among older adults and individuals with chronic conditions such as venous disease, diabetes, and lymphatic disorders. Photobiomodulation, a non-invasive therapy that uses specific wavelengths of light to stimulate biological processes, has shown promise in promoting wound healing. However, its effectiveness for long-standing, treatment-resistant wounds is not yet well established.

This pilot study aims to evaluate the effects of an accelerated photobiomodulation protocol using blue light in patients with hard-to-heal wounds. The study takes place in nurse-led outpatient wound care clinics within the local health authority of Turin (ASL Città di Torino, Italy), which serves a diverse urban population.

Eligible patients are adults with venous, diabetic, lymphatic, or mixed etiology wounds that have remained unhealed for at least two years. Participants receive blue light photobiomodulation treatment twice weekly for four weeks, in addition to standard wound care. Each session includes direct application of blue light to the wound area, following appropriate wound bed preparation and dressing changes.

The primary outcome is the reduction in wound size, measured at baseline, at the end of treatment (week 4), and at a follow-up visit (week 12). Secondary outcomes include changes in pain levels, wound exudate characteristics, and the condition of surrounding skin. Adverse events are monitored throughout the study.

By testing a standardized and replicable treatment protocol, this study seeks to generate preliminary evidence on whether blue light photobiomodulation can safely and effectively enhance healing in this complex patient population. Results may inform future clinical guidelines and support the integration of photobiomodulation into routine wound care pathways.

Inclusion Criteria:

• Adults aged ≥ 18 years;
• Presence of at least one hard-to-heal wound (defined as a wound unhealed despite treatment for ≥ 2 years);
• Wound etiology of venous, lymphatic, diabetic, or mixed origin (venous/lymphatic/arterial documented);
• Wound suitable for photobiomodulation treatment according to clinical evaluation;
• Ability to provide written informed consent;
• Willingness and ability to comply with the study protocol and attend scheduled visits.

Exclusion Criteria:

• Age < 18 years;
• Active oncological disease;
• Wound of exclusively arterial etiology;
• Wound with active infection at the time of enrollment;
• Participation in another interventional clinical trial within the past 3 months;
• Any medical or psychological condition that, in the investigator's judgment, would interfere with study participation or pose an unacceptable risk.

Given the small sample size and potential identifiability of individual cases, individual participant data will not be publicly shared. Aggregate data may be made available upon reasonable request to the corresponding author.