Table 1.
Characteristics of Participants
Fifty-nine patients had an initial SpO of 100%: 22 (37%) of
2
these had ETCO values outside therapeutic range (30-35), and
2
Demographics
11 (19%) had values in the critical range (< 25, > 45). Improve-
Mean age
Men
41.5 (SDEV 22.6, 95% CI 37.3 to 45.7)
ment (moving toward 30-35) was seen in 67% of these patients.
71
45
85
31
(61%)
(39%)
(73%)
(27%)
We next looked at those patients whose initial ETCO val-
2
Women
White
ues were outside the therapeutic range (30-35 mmHg) or were
in the critical range (< 25, > 45) and examined the impact of
AMP crew on ventilatory status. By definition, initial ETCO2
values that, on final measurement, moved toward therapeutic
or outside critical ranges (ie, increased with low initial values
or decreased with high ones) were considered a positive
change. The values that moved in the opposite direction, re-
mained unchanged, or went from being low on the therapeu-
tic/critical ranges to high were considered a negative change.
Nonwhite
Mechanism of injury/chief complaint/mission type
Medical
CHF/COPD
39
6
Trauma
Vehicular
62
15
8
MI/cardiac
CVA
8
Fall
8
Penetrating
Other
5
Other medical 17
34
1
In the 83 patients with nontherapeutic ETCO values on
2
Burn
14
49
66
Drowning
presentation, 61 (73%) changed toward therapeutic ranges.
Scene
(43%)
(57%)
(X2, P = 0.03). In the 41 patients who were outside the critical
Interfacility
range, 33 (80%) had final ETCO values that moved toward
2
normal (X2, P = 0.001).
Methods
Discussion
This retrospective, consecutive case series study was con-
ducted at an air medical program (AMP) based at a university
hospital trauma center in the Northeast. The study included
Our results showed 72% of CO levels were outside the ther-
2
apeutic range on our arrival, and more than a third (n = 41)
were in the critical range. With the use of capnography, we were
116 men and women of all ages who were intubated before the
clearly able to raise or lower the CO levels in most patients and
2
helicopter arrived and for whom ETCO measurement was
keep them within a more therapeutic level, depending on the
patient’s injury or illness.
2
available. Data collected included demographics, injury mecha-
nism or chief complaint, vital signs (heart rate, respiratory rate,
blood pressure, and oxygenation), and initial and final ETCO2
Other research has shown that manual ventilation produces
recurrent low tidal volumes, loss of minute ventilation, and
frequent acidotic/alkalotic states. Acidosis can cause tachycar-
dia, decreased cardiac contractility, increased cerebral blood
flow, and a shift to the right of the oxyhemoglobin dissociation
curve. Alkalosis can cause arrhythmias, decreased cardiac out-
put, and a shift to the left of the oxyhemoglobin dissociation
measurements. Normal ETCO was defined as 35-40 mmHg.
2
Therapeutic ETCO in the presence of head injury or pathology
2
was defined as 30-35 mmHg. Data were entered into a database
(Paradox 7.0: Borland, Scotts Valley, CA) and analyzed using
SPSS (7.5.1, SPSS Inc., Chicago, IL).
curve. With the use of ETCO monitoring, we can effectively
2
Results
reduce these occurrences in flight.
The 116 patients studied were divided between 66 (57%) in-
terfacility and 50 (43%) scene flights. One patient had a reading
of 0 on both initial application and arrival at the receiving facil-
ity; therefore, this patient was excluded from analysis. Demo-
graphics and mechanism of injury or medical condition for the
Capnography also affords us the opportunity to effectively
treat head trauma and pulmonary-compromised patients in the
prehospital setting. Hyperventilation of patients who suffer
cerebral tissue edema is a well-documented treatment, though
its utility is questionable and in fact may be deleterious to pa-
remaining patients are listed in Table 1. Mean initial ETCO was
tient outcome. Although CO treatment levels vary from hospi-
2
2
2
8.6 mmHg (range 0 to 68, 95% CI 28.0 to 30.3). Nineteen pa-
tal to hospital or physician to physician, hyperventilation is
known to cause vasoconstriction at levels of 27 to 35 mmHg.
This mild vasoconstriction once was thought to reduce cere-
bral blood volume, thereby facilitating reduced intracranial
tients had an oxygenation value less than 90% on arrival. All but
one of these patients on arriving at the receiving facility showed
improvement in SpO , and 12 reached 100%. Before and after
2
ETCO , SaO , and initial vital signs are listed in Table 2. Of
pressure. However, more recent literature indicates CO levels
2
2
2
note, only six (5%) patients had ETCO values > 45 mmHg,
perhaps signifying hypoventillation, and all these moved toward
normal values in final reading. Forty-four (38%) patients had
below 20 mmHg may reduce cerebral perfusion, increase hy-
poxia, and cause neurologic insult. Capnography allows the
2
flight team to maintain ETCO at optimal levels. We also can
2
ETCO values < 25 mmHg, perhaps signifying hyperventilation
or shock/hypotension. Thirty-two (73%) of these patients
moved toward normal levels. Of the 12 who did not, two were
adjust portable vent settings to accommodate patients with
pulmonary compromise, providing for optimal ventilation.
2
6-9
Outside of direct visualization of the ET passing through the
vocal cords and radiography to confirm placement, establishing
and maintaining a clear and secure airway undeniably is the
most difficult challenge. Capnography has presented itself as a
valuable and reliable tool time and again for this application.
After being taught to recognize normal and abnormal capno-
profoundly hypotensive and had a decrease in ETCO , and an
2
additional three had significant tachycardia (HR > 150).
We compared initial ETCO with normal initial SpO values,
2
2
reflecting patients who were receiving adequate oxygen but at
too fast or too slow a rate or with inadequate tidal volumes.
28
Air Medical Journal 20:5
Smith
