American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Jan 1995
Comparative StudyThe effect of mechanical ventilation on oxygen consumption in critically ill patients.
We measured oxygen consumption (VO2) during spontaneous breathing with continuous positive airway pressure (CPAP), assist control ventilation (AC), and control ventilation during muscle relaxation (AC-MR) in eight patients undergoing resuscitation from cardiopulmonary failure. VO2 decreased in all eight patients between CPAP and AC-MR; mean VO2 (255 +/- 92 ml/min) on CPAP exceeded that on AC-MR (209 +/- 79 ml/min) (p < 0.005). Compared with CPAP, AC without MR reduced VO2 in five of eight patients and mean VO2 (227 +/- 59 ml/min) tended to decrease (p = 0.14); clinical examination did not distinguish patients requiring MR to reduce VO2 further. ⋯ Both VO2resp and the mechanical work performed by the ventilator on the respiratory system were increased to about five times the efficiencies reported for normal patients, but VO2resp did not correlate with the mechanical work because of a wide range of respiratory muscle efficiencies. These efficiencies are less than those reported in normal patients, which may reflect the effect of sepsis, acidemia, hypoxia, or other conditions in these patients. We conclude that mechanical ventilation with muscle relaxation reduces VO2 by more than 20%; beyond stabilizing pulmonary gas exchange, these interventions preserve limited O2 delivery (QO2) for other vital organs.
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Am. J. Respir. Crit. Care Med. · Jan 1995
Comparative StudyPatient-ventilator interaction during synchronized intermittent mandatory ventilation. Effects of flow triggering.
Synchronized intermittent mandatory ventilation (SIMV) intermixes assisted and spontaneous breaths. Its ability as a weaning technique has been questioned on the basis that patients show little adaptation to ventilator assistance. We studied inspiratory effort and patient-ventilator interaction at different levels (SIMV, 100, 50, and 0%) of flow-triggered SIMV versus pressure-triggered SIMV in patients during the weaning period. ⋯ During pressure-triggered SIMV PTP/b and PTP/min were identical for mandatory and spontaneous breaths, whereas during flow-triggered SIMV PTP/b and PTP/min were significantly lower for mandatory than for spontaneous breaths. This difference was greatest when flow triggering and constant pressure ventilation were associated. These data show that flow triggering reduces inspiratory effort during both mandatory and spontaneous SIMV breaths and obtains a better patient-ventilator interaction.
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Am. J. Respir. Crit. Care Med. · Jan 1995
Comparative Studyvon Willebrand factor antigen levels are not predictive for the adult respiratory distress syndrome.
In patients with nonpulmonary sepsis, von Willebrand factor antigen (vWF:Ag or Factor VIIR:Ag) levels have been reported to be predictive for the development of the adult respiratory distress syndrome (ARDS). We addressed the ability to generalize these results by measuring serial Factor vWF:Ag levels in 96 patients at risk for the development of ARDS. Patients with sepsis, pancreatitis, hypertransfusion, witnessed aspiration of gastric contents, abdominal trauma, chest trauma, and multiple fractures were studied. ⋯ In the sepsis group, the best value for vWF:Ag above which patients would actually develop ARDS was 399%, resulting in a 70% sensitivity and a 47% specificity. For the non-sepsis patients, the optimal value was 273%, yielding a sensitivity of 64% and a specificity of 52%. We conclude that measuring vWF:Ag levels are not helpful in predicting the progression to ARDS in multiple at-risk patients.
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Am. J. Respir. Crit. Care Med. · Jan 1995
Randomized Controlled Trial Comparative Study Clinical TrialMandibular advancement splint: an appliance to treat snoring and obstructive sleep apnea.
Snoring and obstructive sleep apnea (OSA) are related to narrowing of the upper airway. A mandibular advancement splint (MAS) could improve both conditions by increasing oropharyngeal and hypopharyngeal dimensions. The effects of a MAS on snoring and OSA was evaluated 3.5 +/- 2.1 (mean +/- SD) mo after issue in 57 subjects with habitual loud snoring, 39 of whom had an apnea-hypopnea index (AHI) > or = 10. ⋯ Using the MAS significantly improved OSA: AHI decreased from 32.2 +/- 28.5 to 17.5 +/- 22.7 (p < 0.01) and arousal index decreased from 31.4 +/- 20.6 to 19.0 +/- 14.6 (p < 0.01). AHI decreased to < 20 with the MAS in 12 of 17 subjects where untreated AHI was between 20 and 60, and in 2 of 9 subjects where untreated AHI was > 60. Forty-five patients continued to use the MAS regularly.(ABSTRACT TRUNCATED AT 250 WORDS)