Am. J. Respir. Crit. Care Med., Vol 149, No. 6, Jun 1994, 1614-1618.
Hemodynamic effects of nasal and face mask continuous positive airway pressure
PK Montner, ER Greene, GH Murata, DM Stark, M Timms and TW Chick
University of New Mexico, Albuquerque.
Studies of the hemodynamic effects of nasal continuous positive airway
pressure (n-CPAP) in normal subjects have had conflicting results. The
largest study (n = 19) found no effect of up to 15 cm H2O on heart rate
(HR), cardiac stroke volume (SV), or cardiac index. We hypothesized that
n-CPAP, by increasing intrathoracic pressure, should decrease SV and
cardiac output (CO) in a dose-dependent fashion in normal subjects. We also
hypothesized that mouth position, i.e., open or closed, could affect
intrathoracic pressure and thus SV and CO. Six normal subjects were tested
with four levels of CPAP (5, 10, 15, and 20 cm H2O) under three mask
conditions-face mask and nasal mask with the mouth open (mo) or with the
mouth closed (mc). Noninvasive pulsed Doppler measurements of SV and HR
were made under each condition. N-CPAP (mc) and face mask CPAP (f-CPAP)
resulted in significant dose-dependent decreases of SV-24 +/- 5 ml (21%)
and 33 +/- 5 ml (28%), respectively--from baseline to 20 cm H2O (p <
0.05). HR were unchanged and CO significantly decreased with n-CPAP(mc) and
with f-CPAP, 1.6 +/- 0.38 L/min (23%) and 2.29 +/- 0.54 L/min (31%),
respectively, from baseline to 20 cm H2O (p < 0.05). Esophageal pressure
measurements verified increasing intrathoracic pressure with increasing
levels of f-CPAP and n-CPAP (mc) but not with n-CPAP (mo). In conclusion,
n-CPAP (mc) and f-CPAP resulted in significant and similar dose-dependent
decreases in SV and CO.
