There are several methods for hoisting a patient into a helicopter, ranging from stretcher systems to simple slings. They all affect the respiration and hemodynamics to varying degrees, which has resulted in some serious incidents with injuries or death as a consequence. A study in Aviat Space Environ Med 2011 compares the physiological impact of the four most common methods.

The study
Various methods of hoisting a patient was tested in regards to spirometry (FEV1, FVC, FEV1/FVC and inspiratory capacity), SaO2, pulse frequency and respiratory frequency.

Subjects were 27 healthy adult volunteers. Hoist methods are described in the image to the right.

A traditional stretcher is obviously the most common way to hoist a patient. One problem is how the patient will lie flat on his back during the hoist. Lying totally flat on your back is deleterious in regards to lung volumes and breathing. In a marginal patient this could be an issue.

The rescue basket is a method used by the US coast guard. It’s simply a cage lowered into the water or ground. The patient will be transported sitting or semi-sitting in the cage which should be the most optimal position in regards to respiratory volumes.

The single sling method (SSling) is simply a sling that goes under the arms around the chest. It should be obvious how it compresses the thorax and has a negative impact on respiratory volumes.

The double sling method addresses that by adding an extra sling loop that lifts around the legs, off-loading some of the thoracal compression.

As expected SSling was the method with the most impact on vital physiology.

FEV1, FVC and IC were all reduced by 0,5-1L. The DSling and traditional stretcher spared lung volumes somewhat but were still significantly reduced. The rescue basket displayed no change in lung volumes compared to baseline values.

As for the secondary measurements only the SSLing had significant effects. Pulse frequency and respiratory frequency increased, and SaO2 decreased with the SSling while they remained at baseline with the other hoisting methods.

Take-home message
The rescuebasket seems to be the safest way to hoist the really sick or injured patients. The single sling method had significant deleterious impact on lung volumes and vital parameters.

Study lives here.

This is a translation and reworking of a post originally published late 2011.

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