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Determination of Auto-PEEP During Spontaneous and Controlled Ventilation by Monitoring Changes in End-Expiratory Thoracic Gas Volume

1989; Elsevier BV; Volume: 96; Issue: 3 Linguagem: Inglês

10.1378/chest.96.3.613

1931-3543

Richard A. Hoffman, Patti Ershowsky, Bruce P. Krieger,

Obstructive Sleep Apnea Research

Auto-PEEP, or PEEPi, occurs when alveolar pressure fails to decrease to zero at the end of exhalation. While PEEPi can be measured in paralyzed or apneic patients by occlusion of the ventilator expiratory valve at end-exhalation (PEEPi-OC), this may not be possible in patients with spontaneous respiratory efforts. When adjusting the ventilator PEEP valve, FRC increases only after PEEP, has been exceeded. In both mechanically ventilated and spontaneously breathing patients, changes in FRC are mirrored by changes in end-expiratory TCV as measured with RIP set in the DC mode. We compared PEEPi as measured by RIP to PEEPi-OC in 20 patients receiving mechanical ventilator support. Noninvasive measurement of changes in end-expiratory TGV by RIP is a convenient alternative method to estimate PEEPi in both controlled, assisted, and spontaneously ventilating patients. Auto-PEEP, or PEEPi, occurs when alveolar pressure fails to decrease to zero at the end of exhalation. While PEEPi can be measured in paralyzed or apneic patients by occlusion of the ventilator expiratory valve at end-exhalation (PEEPi-OC), this may not be possible in patients with spontaneous respiratory efforts. When adjusting the ventilator PEEP valve, FRC increases only after PEEP, has been exceeded. In both mechanically ventilated and spontaneously breathing patients, changes in FRC are mirrored by changes in end-expiratory TCV as measured with RIP set in the DC mode. We compared PEEPi as measured by RIP to PEEPi-OC in 20 patients receiving mechanical ventilator support. Noninvasive measurement of changes in end-expiratory TGV by RIP is a convenient alternative method to estimate PEEPi in both controlled, assisted, and spontaneously ventilating patients. PEEP, Auto-PEEP, and WaterfallsCHESTVol. 96Issue 3PreviewNormally, the lung volume at end-expiration generally approximates the relaxation volume of the respiratory system, ie, the lung volume determined by the static balance between the opposing elastic recoil of the lung and chest wall.1 However, in patients with airflow limitation, the end-expiratory volume may no longer be determined by an equilibrium between static forces. Instead, end-expiratory lung volume may exceed predicted functional residual capacity (FRC), because the rate of lung emptying is slowed and expiration is interrupted by the next inspiratory effort before the patient has exhaled to the static relaxation volume. Full-Text PDF