Hyperventilation and finger exercise increase venous-arterial Pco2 and pH differences.
BACKGROUND
Since the invention of the pulse oximeter, physicians often or even routinely perform venous blood gas analysis (VBGA). However, it has not been generally agreed that the application of VBGA is practically meaningful in routine clinical situations such as in an ED.


METHODS
We measured venous-arterial Pco(2) difference ((v-a)Pco(2)) and arterial-venous pH difference ((a-v)pH), and analyzed the physiological factors that affect these differences in healthy volunteers and hyperventilation patients.


RESULTS
In healthy volunteers, both (v-a)Pco(2) and (a-v)pH increased during finger exercise or hyperventilation in an intensity-dependent manner. Doppler echography indicated that increases in (v-a)Pco(2) and (a-v)pH during hyperventilation are induced by reduction of peripheral blood flow. Approximately 40% of patients with untreated respiratory alkalosis were found to be incorrectly diagnosed if based only on VBGA.


CONCLUSIONS
It must be noted that VBGA may lead to overestimation of acidosis and to underestimation of respiratory alkalosis when extremities muscles are active or patients are hyperventilating. Physicians should keep these limitations in mind when conducting VBGA.
Umeda
Akira
A
Department of Respiratory Medicine, Ohtawara Red Cross Hospital, Tochigi, Japan. aumeda@hf.catv.ne.jp
Kawasaki
Kazuteru
K
Abe
Tadashi
T
Watanabe
Maki
M
Ishizaka
Akitoshi
A
Okada
Yasumasa
Y
D000138:Acidosis / Q000097:blood / Q000175:diagnosis; D000293:Adolescent; D000328:Adult; D000368:Aged; D000472:Alkalosis, Respiratory / Q000097:blood / Q000175:diagnosis*; D001784:Blood Gas Analysis / Q000379:methods*; D003951:Diagnostic Errors; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006985:Hyperventilation / Q000097:blood*; D008297:Male; D008875:Middle Aged; D055815:Young Adult