ISSN:
1432-1238
Keywords:
Oxygen consumption
;
Ventilation, mechanical
;
Ventilator weaning
;
Post-operative period
;
Chronic obstructive pulmonary disease
;
Work of breathing
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Objective We investigated the effects of continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) on the oxygen cost of breathing ( $$\dot V$$ O2resp) for different states of pulmonary function. Additionally $$\dot V$$ O2resp was measured during spontaneous breathing. Design This was done in a controlled and prospective study. Ventilatory modes were applied randomly. Setting Measurements were performed in a quiet room on volunteers (VOL) and inpatients treated for chronic obstructive pulmonary disease (COPD). Post-operative patients after aortocoronary bypass surgery (ACB) were studied on the cardio-thoracic intensive care unit just before and after extubation. Patients Healthy volunteers (n=14), postoperative patients after aorto-coronary bypass surgery (n=15) and patients with COPD (n=9), xFEV1 47.7%) were the objects of study. Interventions Demand flow CPAP (5 mbar) and PSV (7 mbar, PEEP 5 mbar), using the Hamilton Veolar ventilator, were investigated in comparison to spontaneous breathing. Measurements and results $$\dot V$$ O2 measured by a Datex Deltatrac metabolic monitor. $$\dot V$$ O2resp was calculated by subtraction of total oxygen uptake $$\dot V$$ O2tot) in controlled mode ventilation (CMV) from that in the respective spontaneous breathing mode. For VOL and COPD patients who were not intubated, a CPAP facemask connected to a short 7.5 mm tube was used as connection to the ventilator. Breathing spontaneously under a canopy system VOL showed a VO2resp of 4.5±4.0% compared to 9.2±3.5% for ACB and 15.4±7.7% for COPD. CPAP changed the VO2resp to 7.8±3.9%, 12.0±4.0% and 9.1±3.6% respectively. PSV reduced the $$\dot V$$ O2resp to 7.9±3.8% in ACB and 7.7±5.5% in COPD. Conclusions This investigation confirms findings that postoperative patients have a mild increase in $$\dot V$$ O2resp. COPD exhibit the highest increase in VO2resp. Tracheal tubes, masks and CPAP on a demand flow apparatus increases $$\dot V$$ O2resp in volunteers and postoperative patients after cardiac surgery. The same amount of CPAP in contrary reduces $$\dot V$$ O2resp in patients with COPD. Pressure support ventilation can offset the additional $$\dot V$$ O2resp induced by CPAP but at the same level does not further reduce $$\dot V$$ O2resp in COPD patients.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01701474
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