Page 61 - Journal of Special Operations Medicine - Fall 2017

A Comparison of Ventilation Rates
Between a Standard Bag-Valve-Mask and a New Design
in a Prehospital Setting During Training Simulations

2
1
Joseph T. Costello, DSc, PA-C *; Paul B. Allen, DSc, PA-C ;
Robert Levesque, MPAS, PA-C 3

ABSTRACT
Background: Excessive ventilation of sick and injured patients and tidal volume (TV) delivered, both of which are controlled
is associated with increased morbidity and mortality. Combat by the operator of the device. Because excessive ventilation
Medical Systems (CMS) is developing a new bag-valve-mask depends on the individual healthcare provider, changes in the
®
(BVM) designed to limit ventilation rates. The purpose of equipment that address rate, TV, or both could decrease or
this study was to compare ventilation rates between a stan- eliminate this error. Therefore, it has been recommended that
5
dard BVM device and the CMS device. Methods: This was a a means to remove the human error component in the use of
prospective, observational, semirandomized, crossover study the BVM device be further developed. 1,5
using Army Medics. Data were collected during Brigade Com-
bat Team Trauma Training classes at Camp Bullis, Texas. Combat Medical Systems (CMS; http://www.combatmedical
®
Subjects were observed during manikin simulation training systems.com) is developing a new BVM device that limits the
in classroom and field environments, with total duration of rate of ventilation by controlling the amount of time for the
manual ventilation and number of breaths given recorded for bag to inflate. This device uses a spring to inflate over 5–6 sec-
each device. Analysis was performed on overall ventilation onds and is designed to prevent excessive ventilation. It is also
rate in breaths per minute (BPM) and also by grouping the designed to be completely compressed, with the intent of reduc-
subjects by ventilation rates in low, correct, and high groups ing variability in TVs. This device has the potential to address
based on an ideal rate of 10–12 BPM. Results: A total of 89 many of the current shortcomings of the traditional BVM.
Medics were enrolled and completed the classroom portion of
the study, with a subset of 36 evaluated in the field. A small Physiology
but statistically significant difference in overall BPM between Significantly increased intrathoracic pressure resulting from
devices was seen in the classroom (p < .001) but not in the positive pressure ventilation decreases venous return to the
field (p > .05). The study device significantly decreased the heart by compressing the low-pressure veins, and subsequently
incidence of high ventilation rates when compared by groups decreases cardiac output, systolic blood pressure, and coro-
in both the classroom (p < .001) and the field (p = .044), but nary perfusion pressure. With higher ventilation rates, the
1,2
it also increased the rate of low ventilation rates. Conclusion: increased thoracic pressure is present for a longer time and
The study device effectively reduced rates of excessive ventila- decreases the ability of the cardiovascular system to deliver
tion in the classroom and the field. oxygen via the blood to tissue and organs. This is particularly
problematic in hypotensive patients.
Keywords: bag-valve-mask; BVM; hyperventilation; hemor-
rhage; traumatic brain injury; TBI; prehospital; trauma Hyperventilation occurs when carbon dioxide is cleared from
the body through ventilation at a rate greater than it is pro-
duced. It results in hypocarbia and induces respiratory alkalo-
sis. Both of these factors cause hemoglobin, the oxygen-binding
Introduction
portion of blood, to bind more tightly to oxygen, increasing the
Excessive ventilation of sick and injured patients is associ- likelihood of poor gas exchange. Hypocarbia also has a direct
ated with increased morbidity and mortality. The current effect on blood vessels, leading to cerebral vasoconstriction and
1–5
standard of practice is the use of a traditional bag-valve-mask inadequate oxygen delivery to the brain, which can be espe-
(BVM) to provide ventilation to critically ill and/or injured cially detrimental in patients who have suffered a traumatic
persons. Current BVM devices do not have a method to con- brain injury (TBI). 3,5
trol ventilation rate and this may contribute to excessive ven-
tilation rates, which have been implicated in iatrogenically Military Relevance
induced morbidity and mortality. Excessive ventilation of patients with both significant hem-
orrhage and/or TBI is associated with worse outcomes when
Excessive ventilation with BVM devices can occur among compared with accepted recommendations for proper ventila-
well-trained healthcare professionals and is not limited to un- tion rates. These two conditions have obvious significance
2,3
usual circumstances or the undertrained. The minute ventila- for the military, given the high incidence of both types of
1,6
tion provided to patients is the product of the ventilation rate injuries in combat casualties due to the frequent occurrence of
*Correspondence to joseph.t.costello10.mil@mail.mil
1 Dr Costello is with the San Antonio Military Medical Center (SAMMC), San Antonio, TX. Dr Allen is with the SAMMC, San Antonio, TX.
2
3 Mr Levesque is with the SAMMC, San Antonio, TX.
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