To assess physiologic effects of continuous positive airway pressure (CPAP) and positive end-expiratory pressure (PEEP) during noninvasive pressure support ventilation (PSV) in patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), we measured in seven patients the breathing pattern, lung mechanics, diaphragmatic effort (PTPdi), and arterial blood gases under four conditions: (1) spontaneous breathing (SB); (2) CPAP; (3) PSV of 10 cm H 2O; and (4) PSV plus PEEP (PEEP+PSV). CPAP and PEEP were set between 80 and 90% of dynamic intrinsic PEEP (PEEPi(dyn)) measured during SB and PSV, respectively. PEEPi(dyn) was obtained (1) from the decrease in pleural pressure (ΔPpl) preceding inspiration, and (2) subtracting the fall in gastric pressure (ΔPga) caused by relaxation of the abdominal muscles from the ΔPpl decrease. Abdominal muscle activity made PEEPi(dyn) overestimated in almost all instances (p <0.0001). PSV increased minute ventilation, improved gas exchange, and decreased PTPdi. PEEP added to PSV, likewise CPAP compared with SB, further significantly decreased the diaphragmatic effort (PTPdi went from 322 ± 111 to 203 ± 63 cm H 2O · s) by counterbalancing PEEPi(dyn), which went from 5.4 ± 4.0 to 3.1 ± 2.3 cm H 2O. These data support the use of low levels of PEEP (80 to 90% of PEEPi(dyn)) to treat acute exacerbation of COPD by means of mask PSV.
|Number of pages||8|
|Journal||American Journal of Respiratory and Critical Care Medicine|
|Publication status||Published - May 1994|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine