Unplanned endotracheal extubation in the intensive care unit.

STUDY OBJECTIVE: To identify the frequency, outcome, and factors associated with unplanned endotracheal extubation (UE) in the intensive care unit (ICU). DESIGN: Prospective study. SETTING: An urban, university trauma-surgical ICU. PATIENTS: 96 intubated ICU patients who underwent 101 episodes of UE. INTERVENTIONS: Patient, nursing, respiratory, and demographic factors associated with UE and patient outcome were determined for one year. Results were presented to nursing staff. The incidence of UE as a function of the total number of ventilator days was determined for one year post nursing education. ENDPOINTS: Patients with UE were identified. Patients with reintubation were followed until final extubation. MEASUREMENTS AND MAIN RESULTS: 85% of UE were self-extubations and 15% were accidental. Self-extubations occurred with equal frequency during all three nursing shifts in alert or agitated patients who were not being weaned. Accidental extubations occurred during the day shift in less alert patients and were associated with transport procedures and the use of rotary beds. Overall, 57% of patients were reintubated and most reintubations were in the first hour. Difficulty with reintubation was common, and one patient who could not be reintubated died. There were significantly fewer UE per ventilator day after nursing education. CONCLUSIONS: Patients should be observed closely after unplanned extubation, although many may not require reintubation. Reintubation can be quite difficult, necessitating highly skilled airway management. Attention to associated risk factors may decrease the incidence of both accidental and self-extubation.

Head turning in brain death.

Criteria for determination of brain death in adults have been defined. Spinal cord reflexes may persist after brain death. We present the case of a brain dead patient who had a complex spinal automatism resulting in head shaking and arm extension. The report reviews guidelines for the diagnosis of brain death and discusses complex spinal cord reflexes in brain dead patients.

Clinical performance of a blood gas monitor: a prospective, multicenter trial.

OBJECTIVE: To prospectively assess the clinical performance of a fluorescent optode-based blood gas monitoring system that is designed to perform arterial pH, PCO2, and PO2 measurements as frequently as clinically required without violating the integrity of the arterial catheter tubing system or permanently removing blood from the patient. DESIGN: A prospective, multicenter study to compare modern blood gas analyzer measurements with the coinciding measurements of the blood gas monitoring system. SETTING: Four intensive care units (ICUs) in academic centers with varying patient populations, blood gas measurement routines, and blood gas laboratory facilities. PATIENTS: Adult ICU patients (n = 117), with appropriately functioning radial arterial catheters in place, who were assessed as likely to require multiple arterial blood gas measurements for > or = 2 days. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 117 patients had 1,341 concurrent blood gas analyzer and monitor measurements of arterial pH, PCO2, and PO2 over a 1- to 4-day period. The range of values were 7.14 to 7.64 for arterial pH, 19 to 98 torr (2.5 to 13.0 kPa) for PaCO2, and 38 to 413 torr (5.1 to 54.9 kPa) for PaO2. Linear regression analysis of the optode-based monitor compared with the electrode-based blood gas analyzer demonstrated r2 values of .85 for pH, .92 for PCO2, and .94 for PO2. Comparative statistical analyses for bias (mean difference between analyzer and monitor) and precision (standard deviation of the mean difference [+/- SD] between analyzer and monitor) were respectively:-0.004 and +/- 0.027 for pH; -0.8 torr (-0.11 kPa) and +/- 2.4 torr (0.32 kPa) for PCO2; -2.2 torr (-0.31 kPa) and +/- 8.7 torr (1.2 kPa) for PO2. CONCLUSIONS: Clinical performance of this fluorescent, optode-based blood gas monitoring system demonstrates stability, consistency, and accuracy comparable to modern blood gas analyzers. This system withstood the normal abuse and rigors of clinical conditions common to the ICU while reliably performing in critically ill patients for up to 80 hrs. Use of the device did not significantly alter the function or longevity normally expected from a 20-gauge radial artery catheter. We submit that this blood gas monitoring system can replace the use of blood gas analyzers for ICU patients with indwelling arterial catheters.

Adaptation of pressure support ventilation to increasing ventilatory demand during experimental airway obstruction and acute lung injury.

OBJECTIVE: To estimate the changes in the relative amount of ventilatory assistance offered by inspiratory pressure support during changing ventilatory demand with external airway obstruction and with oleic acid-induced acute lung injury. DESIGN: Prospective, controlled, crossover study. SETTING: Experimental laboratory in a university anesthesiology department. SUBJECTS: Eight dogs anesthetized with pentobarbital. INTERVENTIONS: An external resistor was placed in the breathing circuit to produce increased resistance to breathing. Acute lung injury was produced with oleic acid. Ventilatory demand was increased by increasing the CO2 concentration in inspired gas to produce an increase of 20 torr (2.7 kPa) in end-tidal CO2 tension. During airway obstruction, pressure support was adjusted to reduce the inspiratory decrease in intrathoracic pressure to the level present during unobstructed breathing. During acute lung injury, pressure support was applied to reduce the maximum negative deflection of intrathoracic pressure by 50%. MEASUREMENTS AND MAIN RESULTS: The ventilator effort was estimated by calculating the pressure-time integral of proximal airway pressure; the spontaneous ventilatory effort was estimated in a similar manner from esophageal pressure. The pressure support averaged 10 +/- 3 cm H2O during airway obstruction and 7 +/- 2 cm H2O during lung injury. The CO2 challenge effected an average increase in mean minute ventilation of 78% during airway obstruction (p < .001) and 120% during acute lung injury (p < .01). The augmentation of minute ventilation was accomplished by increasing the ventilatory rate and the transpulmonary pressure while inspiratory time remained unchanged. The pressure-time integrals measured using both airway (p < .001) and esophageal pressure (p < .01) increased significantly during each CO2 challenge, reflecting an increase in the contribution of both the ventilator and the animal to the required breathing effort. Significant decreases in the relative magnitude of the ventilator effort both during airway obstruction (p < .05) and during lung injury (p < .01) indicated that the increase in the spontaneous effort was predominant over the increase in mechanical ventilatory support. CONCLUSIONS: A ventilatory rate-dependent adaptation of pressure support to increased ventilatory demand occurs in an experimental setting both during airway obstruction and lung injury. The results of this study confirm an advantage of breath-to-breath inspiratory pressure support over techniques designed to supply a predetermined mechanical minute volume.

Concurrent bacterial lung infection in patients with AIDS, PCP, and respiratory failure.

STUDY OBJECTIVES: To determine and compare the incidence of concurrent bacterial lung infection in intubated and nonintubated patients with the acquired immunodeficiency syndrome (AIDS) and Pneumocystis carinii pneumonia (PCP) requiring medical intensive care unit (MICU) admission for support of their respiratory function. DESIGN: Retrospective review of medical records. SETTING: A large university hospital and AIDS treatment center. PATIENTS: All AIDS/PCP patients admitted to the MICU for support of oxygenation and/or ventilation between 1985 and 1989. Survival was defined as discharge from the hospital; nonsurvival was defined as death any time during the hospitalization. Patients with acute spinal cord injury (SCI) were used as controls to determine the incidence of nosocomial pneumonia in ICU patients of similar age without AIDS. MEASUREMENTS AND RESULTS: Twenty-nine AIDS/PCP patients met study criteria; eight (28 percent) were survivors and 21 (72 percent) were nonsurvivors. There was no significant difference in duration of intubation or duration of ICU stay between survivors and nonsurvivors with or without intubation. The incidence of bacterial concurrent lung infection (CLI) in AIDS/PCP patients overall was 7 percent and in intubated AIDS/PCP patients it was 10 percent. There was no statistically significant difference in the incidence of bacterial CLI between the survivors and nonsurvivors or between intubated and nonintubated patients with AIDS/PCP. The incidence of nosocomial pneumonia in SCI overall was 17 percent and in intubated SCI patients it was 30 percent. CONCLUSIONS: The incidence of bacterial lung infections in our retrospective study of AIDS patients with PCP is remarkably less than in the general ICU population with respiratory failure and in our control patients with SCI, although the differences did not attain statistical significance. This finding may be related to antimicrobial therapy directed against P carinii. Endotracheal intubation in patients with AIDS and PCP, who were undergoing appropriate antimicrobial therapy, did not result in a significantly higher incidence of bacterial lung infections than in those who were not intubated. There was no significant difference in the incidence of bacterial lung infections between those AIDS/PCP patients who survived episodes of severe respiratory failure and those who did not. Endotracheal intubation should not be delayed or withheld from this patient population due to concerns of pulmonary bacterial superinfection.

The technique of inverse ratio ventilation. Steps to improve oxygenation and decrease dead space ventilation.

Inverse ratio ventilation (IRV) differs from other ventilatory techniques in that it employs a prolonged inspiratory time. In theory, pressure-control IRV allows you to maintain ventilation and oxygenation with lower peak airway and end-expiratory pressures; this may reduce the potential for lung damage secondary to shearing forces. Consider pressure-control IRV for patients with acute lung disease characterized by low lung compliance, diffuse microatelectasis, and increased intrapulmonary shunting. Currently, the chief limitation of this technique is that the patient cannot breathe spontaneously during its use. The best inspiratory to expiratory ratio is the shortest inspiratory time that improves oxygenation with minimal hemodynamic compromise; depression of cardiac output will negate any potential improvement in arterial oxygenation.

Airway pressure release ventilation during acute lung injury: a prospective multicenter trial.

OBJECTIVE: To evaluate the feasibility of airway pressure release ventilation (APRV) in providing ventilatory support to patients with acute lung injury of diverse etiology and mild-to-moderate severity. DESIGN: Prospective, multicenter, nonrandomized crossover trial. SETTING: ICUs in six major referral hospitals. PATIENTS: Fifty adult patients with respiratory failure requiring mechanical ventilation and positive end-expiratory airway pressure. INTERVENTIONS: After optimization of continuous positive airway pressure (CPAP), conventional ventilation and APRV were administered sequentially for 30 mins. During APRV, the CPAP level and airway pressure release level were adjusted to prevent hypoxemia, while the degree of ventilatory support was adjusted by altering the frequency of pressure release. MEASUREMENTS AND MAIN RESULTS: Circulatory and ventilatory pressures, arterial blood gases and pH, heart rate, and respiratory rate were measured. Alveolar ventilation was augmented adequately in 47 of 50 patients by APRV. Adjustment of APRV required an increase in mean CPAP from 13 +/- 3 (SD) to 21 +/- 9 cm H2O and a release pressure of 6 +/- 5 cm H2O. This airway pressure pattern produced a mean airway pressure comparable to that pressure achieved during conventional ventilation. Failure of APRV in three patients could be attributed to an inadequate level of CPAP or an inadequate APRV rate. While maintaining oxygenation of arterial blood and circulatory function, APRV allowed a substantial (55 +/- 17%; p less than .0001) reduction in peak airway pressure compared with conventional positive pressure ventilation adjusted to deliver a comparable or lower level of ventilatory support. CONCLUSIONS: APRV is a feasible alternative to conventional mechanical ventilation for augmentation of alveolar ventilation in patients with acute lung injury of mild-to-moderate severity.

Airway pressure release ventilation in severe acute respiratory failure.

Airway pressure release ventilation (APRV), a new ventilatory support technique, was compared with conventional intermittent positive-pressure ventilation plus PEEP (CPPV) in 18 patients with severe acute respiratory failure. Patients were initially stabilized on CPPV and then switched to APRV. The APRV provided effective ventilatory support in 17 of 18 patients; APRV achieved similar levels of alveolar ventilation as CPPV (for APRV, mean PaCO2 = 45.0 +/- 6.2 mm Hg; vs for CPPV, mean PaCO2 = 43.3 +/- 5.7 mm Hg), with significantly lower mean maximum airway pressures (38.9 +/- 10.1 cm H2O vs 64.6 +/- 15.4 cm H2O; p = 0.0001) and mean VT (0.79 +/- 0.11 L vs 1.05 +/- 0.15 L; p = 0.0002). No significant differences in mean airway pressure, end-expiratory pressure, FIO2, ventilator rate, arterial blood gas levels, and hemodynamic function were noted between APRV and CPPV.

Intensive care unit patients with acquired immunodeficiency syndrome and Pneumocystis carinii pneumonia: suggested predictors of hospital outcome.

OBJECTIVE: To define our ICU experience with AIDS patients, Pneumocystis carinii pneumonia, and respiratory failure, and to delineate factors predictive of hospital survival. DESIGN: A retrospective study in which logistic regression analysis was applied to data obtained during the first 144 hrs of ICU admission. SETTING: A university hospital medical ICU associated with a national AIDS treatment center. PATIENTS: Twenty-seven male patients with AIDS, P. carinii pneumonia, and respiratory failure who desired full supportive and resuscitative care. MEASUREMENTS AND MAIN RESULTS: Of 27 patients who met study criteria, 19 (70%) were nonsurvivors and eight (30%) were survivors. The relative risk of death was 2.2 times greater in patients who exhibited the combination of pH less than 7.35 and a base deficit greater than 4 mEq/L, at any time in their ICU course, than in patients who did not (95% confidence interval = 1.01, 4.81). Furthermore, the relative risk of death was 3.7 times greater in patients who required positive end-expiratory pressure greater than 10 cm H2O after 96 hrs of ICU care than in those patients who did not (95% confidence interval = 1.09, 12.33). Indices of oxygen transfer, severity of chest radiograph abnormalities, concurrent lung infections, and most laboratory studies on hospital admission were not different between the two groups nor predictive of hospital survival. CONCLUSIONS: When dealing with AIDS/P. carinii pneumonia/ICU patients, it is not possible to distinguish who will survive to hospital discharge based on information routinely available before ICU admission. Those patients with the greatest chance of survival demonstrate a significant decrease in the required level of respiratory support within the first 4 days of ICU care. The presence of a metabolic acidemia (pH less than 7.35 and base deficit greater than 4 mEq/L), at any time during the ICU course, is a poor prognostic sign. We suggest that such objective variables should be included in the development of any new outcome predictor model for this group of ICU patients.

Combined nasal intermittent positive-pressure ventilation and rocking bed in chronic respiratory insufficiency. Nocturnal ventilatory support of a disabled person at home.

The use of intermittent positive-pressure ventilation via nasal mask with a rocking bed provided the necessary ventilatory support for a person with quadriplegia living at home. This option was required to maintain an independent life-style of choice. The combination of techniques and the linkage of devices demonstrated an effective use of simple available technology for respiratory care at home and the adaptation of the respiratory prescription to the total needs of each person: medical, social, and financial. The further use of nasal mask ventilation in selected cases is encouraged by clinical research protocol.

Preliminary evaluation of an intra-arterial blood gas system in dogs and humans.

The reliability and accuracy of an intra-arterial fluorescent optode system to measure continuously pHa, PaCO2, and PaO2 were evaluated in a dog model and in a group of critically ill patients. Six hundred sixty-three arterial blood gas (ABG) samples were analyzed for pHa, PaCO2, and PaO2 in the dog studies. The intra-arterial blood gas system (IBGS) indicated a steady state in 420 instances for pH, 359 instances for PaCO2, and 256 instances for PaO2. Comparison of these ABG and IBGS values by linear regression analysis revealed r = .97 for pHa, .95 for PaCO2, and .96 for PaO2. The mean +/- SD of the difference between ABG and IBGS was -0.02 +/- 0.03 for pHa, 1.05 +/- 3.8 for PaCO2, and -17 +/- 13 for PaO2. Nonsteady states were correctly identified by the IBGS in every instance. Comparisons between 79 temporally matched ABG and IBGS values, exclusive of in vivo calibration samples, in 12 critically ill patients revealed r = .97 for pHa, .96 for PaCO2, and .99 for PaO2. The difference was 0.002 +/- 0.02 for pHa, 0.44 +/- 2.97 for PaCO2, and -1.22 +/- 9.34 for PaO2. We conclude that it is possible to measure continuously pHa, PaCO2, and PaO2 with the IBGS in critically ill patients for periods from 3 to 25.5 h while maintaining the ability to monitor BP and withdraw blood samples from the arterial cannula. Agreement between the two techniques is within clinically acceptable ranges for pHa and PaCO2, whereas PaO2 measurement by the IBGS requires further refinement.(ABSTRACT TRUNCATED AT 250 WORDS)

Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients.

Measurement of intrapulmonary shunting (Qsp/Qt), a widely used method for monitoring disturbances of pulmonary oxygen transfer in critically ill patients, involves calculation of arterial and mixed venous oxygen contents. In circumstances where mixed venous blood samples are not readily available, oxygen tension-based indices such as the alveolar to arterial oxygen tension differences (P[A-a]O2), arterial oxygen tension to alveolar oxygen tension ratio (PaO2/PAO2), PaO2 to FIO2 ratio (PaO2/FIO2) and respiratory index (RI) are widely utilized to reflect Qsp/Qt. Oxygen content-based indices such as the estimated shunt are not as widely utilized as the oxygen tension indices. In 75 critically ill patients in whom a pulmonary artery catheter was being utilized to augment clinical care, comparisons were made between Qsp/Qt and P(A-a)O2, PaO2/PAO2, PaO2/FIO2, RI, and estimated shunt to determine which index best reflected Qsp/Qt. Correlations between Qsp/Qt and estimated shunt were good (r = .94) and poor for the P(A-a)O2 (r = .62), PaO2/PAO2 (r = .72), PaO2/FIO2 (r = .71), and RI (r = .74). We conclude that there are no real substitutes for venous oxygen contents in critically ill patients. When pulmonary artery blood is not available for analysis, oxygen tension-based indices are unreliable reflectors of Qsp/Qt while the estimated shunt, an oxygen content-based index, provides a more reliable reflection of Qsp/Qt.

Authoritative medical direction can assure cost-beneficial bronchial hygiene therapy.

A bronchial hygiene (BH) program for non-Intensive Care Unit (ICU) patients in which regimens are determined by respiratory therapy evaluators is described. The medical director of Respiratory Care was given control of orders by the medical staff and assumed responsibility for the evaluators' decisions. Patterns of BH utilization were analyzed for 24 months and were compared with BH utilization patterns in a preceding similar program in which orders were controlled by primary care physicians. Extra-ICU BH therapy (BHT) decreased by 61 percent and neither morbidity nor mortality was undesirably affected. Cost savings exceeded $250,000 per year. Authoritative medical direction of such a program results in cost-beneficial utilization of BHT, provides an excellent guide for resident physicians to learn appropriate utilization of such therapy, provides for quality assurance and medical necessity documentation, and is well accepted by the medical staff.

Perioperative complications of elective tracheostomy in critically ill patients.

This study was designed to examine prospectively the incidence of perioperative complications associated with elective tracheostomy in critically ill patients. An experienced surgeon and anesthesiologist participated in every tracheostomy procedure. In 81 procedures, there was no loss of airway control for greater than 20 sec, no airway obstruction, no blood loss exceeding 50 ml, and no aspiration. One patient (1.2%) had cardiovascular instability. During the next 48 h, two patients (2.4%) required wound packing to control hemorrhage but did not require blood transfusion and two patients (2.4%) had evidence of supraclavicular subcutaneous emphysema that was physiologically inconsequential. There was no perioperative mortality or major morbidity associated with the tracheostomy procedure. We conclude that, under controlled conditions, elective tracheostomy can be performed safely in critically ill patients.