Posted on July 19, 2022 at 10:00 AM by Louis Bilancia
In a medical setting, patient care and safety are a top priority. Providing a high level of care requires the safe and effective operation and maintenance of medical devices and equipment. But what happens when a patient is injured, and it’s not clear how the injury occurred?
In the mid-2000s, staff in a local city hospital removed the infrared (IR) and ultraviolet (UV) filters from a halogen bulb operatory lamp in a surgical suite. The filters were not returned to the lamp, and physicians and patients were exposed to the full electromagnetic radiation spectrum emitted by the halogen lamp light.
Different wavelengths of the electromagnetic spectrum can cause injury to exposed living tissue inside and outside of the body (e.g. sunburn).
Patient injuries were discovered during post-surgery follow-ups. In several patients, the surgery sites did not heal as expected and required long-term use of sterile compression bandages. Upon investigation, it was observed that the surgical sites showed signs of what looked like burn trauma.
It is estimated that over 1,000 individuals may have been exposed to unfiltered light. Several were diagnosed with severe tissue damage and at least one case was untreatable, even with tissue grafts and long-term use of sterile compression bandages.
Testing and Measurement
The surgical light, also known as a surgical luminaire, was designed with infrared (IR) and ultraviolet (UV) filters that pass only those wavelengths that are visible to the human eye, so the surgeon sees realistic colors during surgery.
High filament temperatures cause halogen incandescent bulbs to emit light with a greater color temperature and potentially hazardous wavelengths, including UVA, UVB, UVC and IR.
During the investigation, ESi used a spectroradiometer to evaluate the radiation output of the subject lamp. This instrument can measure the intensity of light and covers the UVA, UVB, visible light, and IR spectrums.
The intensity of each wavelength of light was measured from 240 nm to 1050 nm, which covers the UVA and visible spectrum, and a portion of the UVB and IR spectrums. Wavelengths between 400-790 nm can be seen and felt by people.
ESi’s measurements showed that total energy from the unfiltered UV light between 280 nm and 315 nm UVB band was approximately 25 μW/cm2, with and without the luminaire diffuser. Without the filters in place, UVB intensity peaked at about 100 μW/cm2 at 377 nm. With both the diffuser and optical filter in place, the UV irradiance between 250 nm and 377 nm was approximately 0.1 μW/cm2. The UV wavelengths were intense enough to cause the observed tissue injuries.
While human skin has evolved to have a certain resistance to UV wavelengths, exposed subcutaneous tissue has little to no resistance, and the damage caused is cumulative and compounding. Additionally, the most destructive UV wavelengths are both carcinogenic and germicidal (cytotoxic).
The luminaire instruction manual specified both acceptable and unacceptable methods for cleaning the lenses and filters. In addition, the filters were replaceable components of the luminaire. The surgical luminaires were intended to operate only with the optical filters in place and unfortunately, were not designed with interlocks to prevent use when the filters were removed.