Emergency Medical Transportation Guidelines for Nurses in Primary Care

Chapter 3 - General Nursing Care Considerations in Aeromedical Evacuations

Environmental Flight Stressors

• Noise and Vibration
• Temperature and Related Factors
• Lighting and Space

Equipment in the Aeromedical Environment

• Intravenous Therapy
• Suctioning
• Nasogastric Tubes
• Orthopedic Devices
• Endotracheal and Tracheostomy Tubes
• Colostomy Bags
• Foley Catheters

Oxygen Therapy

• Oxygen Delivery Systems

Appendix 3-1: Administration of Oxygen in Flight

• Oxygen Supply
• Oxygen Requirements at Specific Altitudes
• Duration of Oxygen Supply
• Oxygen Regulators

Environmental Flight Stressors

Noise and Vibration

The high noise level and vibrations experienced in most aircraft may lead to auditory and general physical fatigue on the part of the caregiver, reduced ability to concentrate, problems in communicating with the client and the crew, and difficulties in monitoring the client.

Auditory fatigue consists of a reversible shift in the threshold of hearing caused by prolonged exposure to high noise levels. Use of headsets (if available) will prevent this problem.

Temperature and Related Factors

Unstable temperature, lack of humidity (which may result in dehydration), and drafts or ventilation problems are three interrelated, potentially troublesome factors in air transport. The degree to which they occur depends upon the aircraft.

Thermal stress can cause a variety of physiologic responses, including changes in oxygen demands, changes in the size of blood vessels and excessive perspiration. Thermal stress can lead to fatigue and motion sickness. The main problem with temperature occurs during transfer of the client from the community facility (e.g., the nursing station) to the aircraft in winter. An open truck may be the only vehicle available. If the client is able and his or her condition is stable enough, seat the client in the cab of a heated truck for transport to the airstrip; ensure that the stretcher is brought along. Be organized so as to ensure that the client is not exposed to the outside environment for any longer than necessary. The pilot should be requested to adjust temperature and ventilation in the aircraft according to the needs of the client.

Lighting and Space

In general, the lighting and space available on most aircrafts are less than optimal for assessing the client and performing procedures. Therefore, all medevac bags should contain at least one flashlight with extra batteries. Small pen flashlights are often useful as well.

Because of space limitations, familiarize yourself with the interior of the aircraft to be used before the client is loaded. The medical escort should supervise the placement of the client and equipment. Oxygen and emergency equipment should be within easy reach. In most circumstances the client will be positioned with his or her head toward the nose of the aircraft. See chapter 4, "Primary Care during Transport," for details about positioning the client for specific clinical conditions.The client and equipment should be safely secured by the air crew and checked by the medical escort.

Equipment in the Aeromedical Environment

Many pieces of equipment that run on electricity may interfere with the aircraft's avionics. Therefore, use only equipment that has been tested for safety in the aviation environment.

Intravenous Therapy

IV lines can be affected by reduced atmospheric pressure (which results in gas expansion) and turbulence. Possible effects include variable flow rate and dislodgement. In addition, flow rates may be affected by the lower gravity at high altitudes, as the IV reservoir may be only 0.6 m (2 ft) or less above the infusion cannula.

The IV tubing may become constricted because of confined spaces or problems in positioning the client's hand or arm.

If an IV line is required for administration of medications or maintenance of body fluids, it should be inserted before the flight begins. At least two sites should be available for all seriously ill clients. It is preferable to insert the largest-bore IV cannula possible (18 gauge or larger for adults).

Management of IV Lines

• Carefully secure all IV lines, particularly during loading and unloading procedures.
• Position the IV fluid as high as possible above the IV insertion site.
• Use infusion pumps (if available) to control IV rates, especially in children and for the administration of medications by continuous infusion in any client.
• Closely monitor IV infusions during flight, particularly during ascent and descent.
• If the transfer from the community facility to the aircraft is expected to be lengthy or difficult, a saline lock cannula may be inserted, with full IV hookup on board the plane.
• To keep IV solutions from freezing, place containers in a sleeping bag during transit, if possible.
• If low flow rate in the IV line creates a problem, flow may be increased by applying pressure to the IV bag. This should be done with an IV pressure infusor whenever possible. Care is needed when the reservoir is almost depleted, as applying pressure on the IV bag at this stage may result in air embolus. Ablood pressure cuff should not be used to apply pressure, as the cuff obscures the fluid level in the bag, and changes in altitude will cause changes in the pressure exerted by the cuff. If IV flow rates must be increased, it is safest to do so by intermittently squeezing the bag to deliver boluses of fluid when required.

Suctioning

For oral, nasal or pharyngeal suctioning, higher-pressure suctioning is required for prompt removal of viscous secretions, vomitus and blood. Conversely, lower-pressure suctioning will minimize mucosal trauma.

Provide continuous reassurance during any suctioning procedure.

Suction should be continued for no more than 5–10 seconds at a time.

Suctioning Equipment

• In most dedicated aircraft used for medevac, suctioning units are permanently installed.
• A manual or foot-operated suction pump (e.g., Ambu Suction Pump) may offer a backup. Although cumbersome, this equipment may be used until electrical suction can be instituted or can be used as emergency backup for the latter.

Suction Catheter

• Have available a tonsil-tip suction device
• Have available suction catheters in a variety of sizes, to accommodate clients of all ages
• Be aware that in cold temperatures, fluid in small-bore tubing may freeze and the tubing may become plugged up

Nasogastric Tubes

It is best to leave the nasogastric tube to straight drainage. It may be left open to ambient cabin pressure, with intermittent suction applied manually by a catheter-tipped syringe.

Orthopedic Devices

Orthopedic air splints are not to be used because of the hazards associated with expansion of gas during ascent.

Back slab casts or wood splints are safer for initial immobilization, as either can accommodate tissue swelling and gas expansion. Full casts that have been in place for less than 72 hours should be split on two sides (bi-valving) before flight.

Endotracheal and Tracheostomy Tubes

Cuffs on tubes such as endotracheal and tracheostomy tubes are usually filled with air. During flight this air can expand, putting pressure on the trachea and causing ischemia. Therefore, before the flight, replace the air with sterile water.

Colostomy Bags

The expansion of gas within the bowel stimulates colonic motility, which results in large amounts of gaseous discharge and distension of the bag during flight.

Management

• If gaseous distension occurs, relieve it by inserting a catheter through the colostomy opening
• If the bag has a tight seal, open the end of the bag, expel the gas and re-close bag.
• Have an extra supply of colostomy bags on hand
• During the flight, moderately restrict the client's intake of fluids

Foley Catheters

During flight, air in the catheter can expand, putting pressure on the urethra. Therefore, the balloon should be filled with sterile water, not air.

Oxygen Therapy

It is frequently difficult to clinically assess for signs of hypoxia during flight because of noise, poor lighting and other factors. Therefore, pre-flight assessment for the presence or risk of hypoxia, liberal use of oxygen and monitoring of oxygen saturation by pulse oximetry (if available) in flight are very important.

Pulse oximetry readings are not accurate in clients with poor perfusion or carbon monoxide poisoning.

There are several key points about oxygen delivery in the aeromedical environment:

• As altitude increases, oxygen requirements increase
• As altitude decreases, oxygen requirements decrease
• Clients requiring oxygen on the ground may require a higher flow rate or a different delivery system to meet their oxygen needs during flight
• Estimated oxygen consumption must be calculated before the flight to ensure that an adequate supply of oxygen is available

See Appendix 3-1, "Administration of Oxygen in Flight," below, for further details on use of oxygen in the aeromedical environment.

Oxygen Delivery Systems

See Table 3-1 to determine the oxygen percentage delivered at various flow rates with different types of equipment.

Nasal Cannula

• Preferable to nasal catheter
• Delivers low concentration of inspired oxygen (24% at 1 L/min) while allowing the client to eat, speak and drink
• Oxygen is partly humidified and warmed by the nasal passages
• Humidify oxygen if transport is expected to exceed 1 hour

Venturi Mask

• Delivers a concentration percentage ranging from 24% to 60%
• Does not guarantee delivery of a specified percentage of oxygen; rather guarantees that the specified oxygen concentration is not exceeded
• May be modified to deliver inhaled medications (e.g., salbutamol)
• Air entrainment parts must be kept clear and open

Non-Rebreather Mask with Reservoir Bag

• For any client requiring a high concentration of oxygen (e.g., asthma or multiple trauma)
• At 10–12 L/min, oxygen concentration of 95% may be obtained, assuming that mask fit is adequate
• Flow rate must be high enough to prevent complete collapse of the reservoir bag with each breath
• Oxygen should be flowing into the mask and the bag should be full before it is put on the client

Positive Pressure Oxygenation

Positive pressure ventilation may be delivered by any of the following means:

• Mouth-to-mouth resuscitation
• Mouth-to-mask resuscitation
• Bag-valve mask device (e.g., Ambu bag)

Table 3-1: Determining Oxygen Percentage from Flow Rate (L/min)*

*Assumes respiratory rate of 16--20 breaths/min.
†Low-flow systems: % oxygen delivered is variable and unpredictable.
‡High-flow systems: % oxygen delivered is consistent and predictable, assuming that the mask fits.

Appendix 3-1: Administration of Oxygen in Flight

Oxygen Supply

Oxygen for transport is usually supplied as gaseous compressed oxygen (GOX).

The most common type of container for gaseous compressed oxygen is a cylinder. The cylinders are usually made of steel and come in different sizes (size E is the most common). Many dedicated medevac aircraft use aluminum tanks because of the significant weight advantage. In most medevac aircraft, large tanks of oxygen (often 2-M size) are installed in the cabin, providing a reliable source of oxygen. Portable tanks may be taken on charter flights and on medevac by surface transport.

Check all oxygen cylinders before the transport to ensure that they are completely filled, since tanks may leak or they may inadvertently be returned empty from a previous medevac. In addition, carefully estimate the number of tanks required for the trip, based on the flow rate required and the air time to destination or an alternate destination.

Oxygen Requirements at Specific Altitudes

The following equation is used to determine the fraction of inspired oxygen (Fio₂) requirement when flying to a different altitude.

where

Fio₂ = fraction of inspired oxygen that client is currently receiving

AP₁ = current barometric or atmospheric pressure (in mm Hg)

AP₂ = destination barometric or atmospheric pressure (in mm Hg)

Fio₂(a) = fraction of inspired oxygen that client will need at destination altitude

Example

Client is receiving 30% oxygen, current altitude is 2000 ft (where pressure is 706 mm Hg), and flight altitude is expected to be 6000 ft (where pressure is 609 mm Hg).

Therefore, the client will need oxygen delivered at 35% throughout the transport at 6000 ft if his or her condition remains unchanged.

To determine barometric pressures at various altitudes, see Table 2-2, "Barometric Pressure at Various Altitudes," in chapter 2, "Aeromedical Evacuation"

Duration of Oxygen Supply

To calculate the length of time that an oxygen tank will last, you must be familiar with the capacity of the various sizes of tanks, the "tank factors" and the equation that follows.

Tanks come in a variety of sizes, each with its own multiplying factor used in calculating capacity:

The following equation is used to calculate duration of oxygen supply:

where tank pressure is in pounds per square inch, flow rate is in liters per minute, and duration of supply is in minutes.

Example

For an E cylinder with a pressure of 1500 psi and a flow rate of 3 L/min:

See below for duration of oxygen supply of different tank sizes at various rates.

In determining how much oxygen will be needed, add 2 hours to estimated flight time, to ensure adequate oxygen supply in case of delay.

Oxygen Regulators

Oxygen regulators are calibrated for accuracy at sea level. At altitude, oxygen will flow faster than the setting on the flow meter.