Biomedical Engineering Reference
In-Depth Information
personal protective equipment, and to follow safe work prac-
tices at all times.
Though often seen as an adversary, an OH&S offi cer, can
be a strong advocate for safety, if viewed as a professional
partner. This resource person can be a member of the team
approach, assisting the LSO with audit, compliance, educa-
tion, and staff motivation, and always resulting in fewer risks
of injury for patient and staff, less potential for legal entan-
glement, and overall lower costs for the program. Remember,
even though it may seem that the cost of laser safety training
is high, it is always far less than the cost of one injury or
lawsuit.
Control of access to equipment is accomplished by two
procedures: key storage away from the console and position-
ing a dedicated operator at the control panel whenever the
laser is in use. When an individual is operating (activating
the equipment) and using (delivering the energy to the tar-
get tissue) the laser without assistants present, he or she is
responsible for controlling access to all components of the
device.
Protective eyewear, corresponding to the laser in use, should
be placed with each door sign posted at NOHA/NHZ entry-
ways, to be used by anyone who has to enter the laser room in
an emergency. Signs should only be posted when the laser is in
actual use, and removed or covered when the laser is turned
off and key removed. These are indicators to others in the
facility that there is a potentially hazardous situation in the
room, and safety procedures are in effect. If the sign is left up
all the time, it loses its meaning, and staff tends to become
casual about entering the room. When signs are used properly,
there is no need to lock doors or connect lasers to interlocks,
which are hazardous and should never be utilized in medical
settings (Fig. 17.1).
Windows and doors should be covered with barriers for all
wavelengths that transmit through glass. The LSO must
assess the facility to determine what type of coverings are
required, and the options vary from black barrier curtains, to
purpose built window fi lms marked with the actual OD of
protection (Fig. 17.2). The criteria for selection of window
covers include nonfl ammability, infection control guidelines,
and ability of the material to reduce the laser transmission
below the MPE.
The control panel of the laser should never be left activated
and unattended. If the operator has to leave the room, the laser
should be turned off, and the key removed and either stored or
taken with the operator or LSO. If the operator sets up and
tests the laser, but then must wait while the patient comes into
the room, the laser must be kept on standby. This mode deac-
tivates the shutter and prevents accidental misfi ring. The only
time the laser should be turned to the ready mode, is when the
clinician is aimed at target tissue, and is ready to treat.
State law determines the licensing requirements for who can
operate a laser under the supervision of a physician. In an
operating theater, a technician operating a laser should be
supervised by a licensed medical professional. In private prac-
tice, the laser user (clinician) frequently functions as the
supervisor. No untrained individual should ever be allowed to
operate a laser under any circumstance, without immediate
supervision of a competent laser user.
In the case of rental lasers, the renter and the staff must be
educated about the laser and its delivery systems, accessory
equipment, mechanism of action, all safety measures, and
minor troubleshooting. Clinicians should insist on compre-
hensive staff training for two reasons: one in order to meet
standards; two, regardless of what equipment is being used, or
who owns the equipment, the professional staff are responsi-
ble for patient advocacy, management, and safety.
The footswitch for activating the laser must be given only to
the credentialed laser user. Position all other footswitch acti-
vated devices away from the laser and clearly indicate to the
user, which pedal is for the laser, and which ones are for other
devices. Accidental activation of the pedal is one of the most
commonly reported accidents.
Procedural Control Measures
Controlling hazards in the laser treatment room depends on
controlled access to the room and to the equipment, proper
use of personal protective devices, monitoring testing and
operations of the laser and its delivery systems, appropriate
applications, and vigilance on the part of each laser team
member.
Controlled Access
Controlled access is based on the identifi cation of the NOHA
(a term used in IEC standards), or nominal hazard zone
(NHZ—a term used in American National Standards). This is
the area within which the level of exposure to laser radiation
can exceed the maximum permissible exposure (MPE) levels.
The MPE is a mathematical calculation based on variables
including wavelength, power, distance, and time of exposure,
which results in a length of time (usually milliseconds) an
unprotected eye can be exposed to laser radiation, without
producing injury. The NOHA/NHZ is a mathematical calcula-
tion, resulting in an area around the laser, within which laser
hazards may exist, and protective devices are required. These
values should be readily available from the laser manufactur-
er's documentation.
Standards indicate procedures for maintaining a controlled
access area. Some of the key points are as follows:
1. Regulation CAUTION (DANGER) signs are posted
visibly, on each entry way into the NOHA/NHZ.
2. Appropriate protective eyewear for laser in use, is
placed with the signs at each entryway. These are
removed only at conclusion of the procedure.
3. Windows are covered with blinds, shades, or other
nonfl ammable barriers that reduce transmission
of the beam to acceptable levels below the MPE for
laser wavelengths that can penetrate glass (long
wavelengths that absorb in water do not need win-
dow barrier protection).
4. Everyone within the NOHA is authorized by
the LSO.
5. Doors are kept closed, but not locked at all times
during laser use.
The measurement that defi nes the NOHA/NHZ may be
obtained from the manufacturer of the laser, by having the
LSO perform the calculations, or by designating the entire
room as the controlled area. If the entire room is so designated,
everyone in the room must follow all safety procedures at all
times, including wearing of protective eyewear.
