Influence of FIO2 on PaCO2 during noninvasive ventilation in patients with COPD.
BACKGROUND
The administration of a high FIO2 to COPD patients breathing spontaneously may result in hypercapnia, due to reversal of preexisting regional hypoxic pulmonary vasoconstriction, resulting in a greater dead space. Arterial blood gas trends have not been reported in these patients. In a 31-bed medical ICU in a teaching hospital we prospectively investigated the response of 17 CO2-retaining COPD patients, after acute respiratory crisis stabilization with noninvasive ventilation, to an FIO2 of 1.0 for 40 min, after having been noninvasively ventilated with an FIO2 of ≤ 0.50 for 40 min.


RESULTS
The mean ± SD baseline findings were: PaO2 101.4 ± 21.7 mm Hg, PaCO2 52.6 ± 10.4 mm Hg, breathing frequency 17.8 ± 3.7 breaths/min, tidal volume 601 ± 8 mL, and Glasgow coma score of 14.8 ± 0.3. PaO2 significantly increased (P < .001) when FIO2 was increased to 1.0, but there was no significant change in PaCO2, breathing frequency, tidal volume, or Glasgow coma score.


CONCLUSIONS
During noninvasive ventilation with an FIO2 sufficient to maintain a normal PaO2, a further increase in FIO2 did not increase PaCO2 in our CO2-retaining COPD patients.
Intensive Care Unit, Moinhos de Vento Hospital, Porto Alegre, Rio Grande do Sul, Brazil.
Augusto
A
Savi
Juçara
J
Gasparetto Maccari
Túlio
T
Frederico Tonietto
Ana Carolina
AC
Peçanha Antonio
Roselaine
R
Pinheiro de Oliveira
Marcelo
M
de Mello Rieder
Evelyn Cristina
EC
Zignani
Émerson
É
Boschi da Silva
Cassiano
C
Teixeira
D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000209:etiology; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D063087:Noninvasive Ventilation; D010100:Oxygen / Q000008:administration & dosage*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000503:physiopathology / Q000628:therapy; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D013990:Tidal Volume
D002245:Carbon Dioxide; D010100:Oxygen
PaCO2; PaO2; carbon dioxide; hypercapnia; noninvasive ventilation; obstructive lung disease; oxygen