Edgar Delgado

Low levels of nitric oxide as contaminant in hospital compressed air: physiologic significance?

OBJECTIVES To determine whether the levels of nitric oxide found in hospital compressed air have a clinically relevant effect on oxygenation in intubated patients with normal lungs. DESIGN Prospective study. SETTING Cardiothoracic and surgical intensive care unit in a university hospital. PATIENTS Twelve postoperative patients receiving mechanical ventilation. INTERVENTIONS Pure nitrogen and oxygen were substituted for hospital compressed air as a source of blending for correct FIO2. MEASUREMENTS AND MAIN RESULTS Hemodynamics and PaO2 were measured in nitrogen and oxygen used for blending oxygen during stable FIO2 levels. Inhaled nitric oxide was measured with a nitric oxide-chemiluminescence detector. There was no clinically relevant change in systemic hemodynamics. However, the PaO2 decreased significantly when nitrogen was used for blending. Inhaled nitric oxide levels varied from 2 to 550 parts per billion during use of hospital compressed air; no nitric oxide was detectable during use of nitrogen. CONCLUSIONS The low concentration of nitric oxide in hospital compressed air improves oxygenation in patients with normal lungs receiving mechanical ventilation.

Improved Outcomes With Routine Respiratory Therapist Evaluation of Non-Intensive-Care-Unit Surgery Patients

BACKGROUND Respiratory therapist (RT) driven protocols decrease ventilator days and resource utilization in the intensive care unit (ICU). Protocols have been studied in non-ICU settings, but their effect on mortality has been incompletely studied. METHODS In our neurosurgery step-down, trauma/surgery step-down, and trauma/surgery general units we initiated an RT-driven evaluate-and-treat protocol that included a standardized, quantitative, RT-driven patient-assessment scale and protocolized interventions. Before and after initiation of the protocol we collected data on non-ICU patients at risk for pulmonary complications. RESULTS The patient groups before (n = 2,230) and after (n = 2,805) protocol initiation were well matched in age, sex, Charlson score, and admitting service. Most of the patients, whether assessed by a physician or an RT, were deemed to have low risk of pulmonary complications and did not require any respiratory treatments. The number of respiratory treatments increased after protocol initiation, but the patients who received respiratory treatments after protocol initiation had shorter ICU stay and hospital stay, and lower total hospital costs than those who received respiratory treatments before protocol initiation. There was a nonsignificant trend toward lower mortality after protocol initiation. CONCLUSIONS Our RT-evaluate-and-treat protocol for non-ICU surgery patients was associated with more patients receiving respiratory treatments but decreased ICU and hospital stay and lower total hospital costs. Routine RT-driven assessment of non-ICU patients may reduce pulmonary complications in high-risk patients.

Auto-positive end-expiratory pressure during tracheal gas insufflation : Testing a hypothetical model

ObjectiveThe major benefit of tracheal gas insufflation (TGI) is an increase in CO2 elimination efficiency by removal of CO2 from the anatomical deadspace. In conjunction with mechanical ventilation, TGI may also alter variables that affect CO2 elimination, such as minute ventilation and peak airway pressure (peak Paw) and cause the development of auto–positive end-expiratory pressure (auto-PEEP). We tested the hypothesis that TGI-induced auto-PEEP alters ventilatory variables. We predicted that TGI-induced auto-PEEP offsets the beneficial effects of TGI on CO2 elimination and that keeping total PEEP (ventilator PEEP + auto-PEEP) constant enhances the CO2 elimination efficiency afforded by TGI. DesignProspective study of two series of patients with acute respiratory distress syndrome receiving mechanical ventilation. SettingIntensive care units at a university medical center. PatientsEach series consisted of eight sequential hypercapnic patients. InterventionsIn series 1, we examined the effect of continuous TGI at 0 and 10 L/min on Paco2, without compensating for the development of auto-PEEP. In series 2, we examined this same effect of continuous TGI while reducing ventilator PEEP to keep total PEEP constant. TGI-induced auto-PEEP was calculated based on dynamic compliance measurements during zero TGI flow conditions (&Dgr;V/&Dgr;P) after averaging the two baseline values for peak Paw and tidal volume and assuming compliance did not change between the zero TGI and TGI flow conditions (&Dgr;VTGI/&Dgr;PTGI). Measurements and Main ResultsIn series 1, total PEEP increased from 13.2 ± 3.2 cm H2O to 17.8 ± 3.5 cm H2O without compensation for auto-PEEP (p = .01). Paco2 decreased (p = .03) from 56.2 ± 10.6 mm Hg (zero TGI) to 52.9 ± 9.3 mm Hg (TGI at 10 L/min), a 6% decrement. In series 2, total PEEP was unchanged (p = NS). Paco2 decreased (p = .03) from 59.5 ± 10.4 mm Hg (zero TGI) to 52.2 ± 8.3 mm Hg (TGI at 10 L/min), a 12% decrement. There was no significant change in Pao2; there were no untoward hemodynamic effects in either series. ConclusionsThese data are consistent with the hypothesis that mechanical ventilation + TGI causes an increase in auto-PEEP that can blunt CO2 elimination. In addition to the ventilator modifications necessary to keep ventilatory variables constant when TGI is used, it is also necessary to reduce ventilator PEEP to keep total PEEP constant and further enhance CO2 elimination efficiency.

The effect of tracheal gas insufflation on gas exchange efficiency.

Transtracheal gas insufflation (TGI) improves gas exchange efficiency, but is associated with hyperinflation, and usually requires ventilator adjustment to compensate for the increased gas flow. Although bidirectional TGI (Bi-TGI) minimizes hyperinflation, it does not preclude the need to reduce tidal volumes to prevent hyperinflation. A flow-compensation system was developed by Respironics (Murrysville, PA) to match TGI flows; however, neither that nor the efficacy of Bi-TGI have been tested in vivo. We tested the hypotheses that flow compensation allows for a constant minute ventilation; Bi-TGI produces less hyperinflation than does unidirectional TGI (Uni-TGI), and endotracheal tube size influences the degree of hyperinflation during TGI. Seven anesthetized intact dogs were studied during positive-pressure ventilation using the Respironics flow compensation system. Measurements were made during steady-state conditions at constant and measured levels of CO2 production. Gas exchange efficiency (assessed by expired gas analysis for dead space) and hyperinflation (measured as an increase in pleural pressure) were compared during Bi- and Uni-TGI and for endotracheal tube sizes varying from 7 to 10F. Bi- and Uni-TGI could be delivered at constant minute ventilation without adjusting ventilatory setting when the flow compensation circuit was present. Uni-TGI produced more hyperinflation than did Bi-TGI with all sizes of endotracheal tube, and hyperinflation was universally present as tube size decreased to 7.5F. We conclude that this new flow compensation system allows for the delivery of TGI without the need for adjustments to the ventilator settings, and that Bi-TGI produces less hyperinflation than does Uni-TGI, even with small diameter endotracheal tubes.

Equipment, Medications, and Supplies for a Medical Emergency Team Response

To mount an effective emergency response, medication and equipment resources must be available, reliable, and organized in a way to make them easily usable. Staff must be trained adequately so that they know what their resources are and how to manage them. Standardizing the equipment and medications contributes to a safe system by improving a number of logistic issues, including staff training, performance, error reduction, equipment maintenance and replacement after a crisis, and finally the institution’s ability to revise medication and equipment resources for crises. We believe that improving efficiency and reliability can reduce delays and errors, and contribute to the primary goal of improving patient outcomes following a crisis event.