Noninvasive Intracranial Cerebral Flow Velocity Evaluation in the Emergency Department by Emergency Physicians

Transcranial Doppler (TCD) is an accepted modality for the evaluation of cerebral blood flow velocities. OBJECTIVES: The purpose of this study was to test the feasibility of bedside TCD measurement in the emergency department (ED) with critically ill, intubated patients. METHODS: A prospective convenience sample of patients presenting to a university hospital over a two-month period underwent TCD evaluation of the middle cerebral artery. Intubated patients with head trauma and any patient requiring tracheal intubation were eligible. A 2-MHz Doppler probe was positioned over the temporal bone to acquire blood flow velocities. An emergency medicine resident and research assistant obtained measurements. Continuous TCD tracings were recorded on a video cassette recorder tape for quality assurance review and data collection. Vital signs and therapeutic interventions were also recorded. Flow velocities were measured in cm/s; the peak Resistance Index (RI) was calculated for each patient. RESULTS: A total of 30 patients were enrolled in the study. Adequate tracings were obtained in 25 patients (83%) without a disruption of resuscitation. Tracings could not be obtained in five patients; they were listed as TCD failures. However, in two of these patients, adequate flow velocity tracings were obtained after resuscitation. Four patients were evaluated during tracheal intubation. One patient was monitored successfully during cardiopulmonary resuscitation. The median time required for data acquisition was 1.9 minutes. The mean highest RI for those who expired was 0.84. For those who survived, the mean highest RI was 0.52. The difference of 0.32 was statistically significant (p = 0.04). CONCLUSIONS: Noninvasive blood flow velocity monitoring of the middle cerebral artery using TCD is feasible in the ED when performed at the bedside on intubated patients with traumatic brain injury and others during tracheal intubation and resuscitation.     

Metabolic and hemodynamic responses to concurrent voluntary arm crank and electrical stimulation leg cycle exercise in quadriplegics.

This study determined the metabolic and hemodynamic responses in eight spinal cord injured (SCI) quadriplegics (C5-C8/T1) performing subpeak arm crank exercise (ACE) alone, subpeak functional electrical stimulation leg cycle exercise (FES-LCE) alone, and subpeak FES-LCE concurrent with subpeak ACE (hybrid exercise). Subjects completed 10 minutes of each exercise mode during which steady-state oxygen uptake (VO2), pulmonary ventilation (VE), heart rate (HR), cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), arteriovenous oxygen difference (a-v O2 diff), and total peripheral resistance (TPR) were determined. Although mean VO2 for both ACE alone and FES-LCE alone was matched at 0.66 l/mi, individualized power outputs ranged from 0-30 W (mean = 19.4 +/- 1.3) and 0-12.2 W (mean = 2.3 +/- 0.6), respectively. Hybrid exercise elicited significantly higher VO2 (by 54 percent), VE (by 39-53 percent), HR (by 19-33 percent), and CO (by 33-47 percent), and significantly lower TPR (by 21-34 percent) than ACE or FES-LCE performed alone (P less than or equal to 0.05). Stroke volume was similar between hybrid exercise and FES-LCE alone, and these two exercise modes evoked a significantly higher SV (by 41-56 percent) than during ACE alone. These data clearly demonstrate that hybrid exercise creates a higher aerobic metabolic demand and cardiac-volume load in SCI quadriplegics than either subpeak levels of ACE or FES-LCE performed separately. Therefore, hybrid exercise may provide more advantageous central cardiovascular training effects in quadriplegics than either ACE or FES-LCE alone.     

Aerobic power of competitive paraplegic road racers.

The purpose of this study was to determine peak aerobic power and associated physiological responses in highly competitive spinal cord injured (SCI) paraplegic road racers. Seven (6 male and one female) active paraplegic (lesions T4-T12) road racers and 9 healthy untrained able-bodied males performed continuous graded arm crank ergometer tests to exhaustion for determinations of peak power output (PO), oxygen uptake (VO2), pulmonary ventilation (VE), heart rate (HR), and respiratory exchange ratio (RER). Compared to able-bodied subjects, male paraplegic road racers elicited significantly (p less than or equal to .05) higher mean (+/- SD) peak levels of PO (141.6 +/- 8.8 vs 111.4 +/- 27.7 W), absolute VO2 (2.72 +/- .52 vs 2.22 +/- .381/min), and VO2 per unit of body weight (43.06 +/- 7.4 vs 30.33 +/- 4.3 ml/kg/min). Although peak HR (180.3 +/- 9.5 vs 173.2 +/- 8.5 bpm) and VE (92.8 +/- 17.2 vs 74.6 +/- 20.3 l/min) tended to be higher for male paraplegic road racers than able-bodied subjects, the differences were not statistically significant. The female paraplegic road racer achieved the highest peak levels of PO (119 W) and VO2 (1.99 l/min; 38.0 ml/kg/min) reported to date for wheelchair-dependent women. These data suggest that intense physical training via wheelchair propulsion can markedly enhance upper body cardiovascular fitness in SCI paraplegics. However, the correlational analysis between 10 km time and peak VO2 was nonsignificant (p greater than .05) indicating that factors other than peak upper body aerobic power may influence wheelchair road racing performance.     

Respiratory rates in emergency department patients

The respiratory rate is a sensitive and nonspecific indicator of respiratory dysfunction. Establishing a "normal" respiratory rate has mainly been arbitrary. This study evaluated "normal" respiratory rates in 110 emergency department patients. The mean respiratory rate was 20.1 (+/- 4.0). Women had a more rapid respiratory rate 20.9 (+/- 3.9) than men 19.4 (+/- 4.0) (p less than .04). Smokers had a higher respiratory rate 20.5 (+/- 4.0) than nonsmokers 19.3 (+/- 4.0), but this was not statistically significant (P = 0.124). It was also noted that the respiratory rate measured by the nurse was almost always different from that measured by the medical student (P less than 0.0001). Based on a review of the literature concerning what constitutes a "normal" respiratory rate, we conclude that the "normal" respiratory rate may be higher than that suggested in the medical literature.     

Analysis of resistance to gas flow in nine adult ventilator circuits

We measured the resistance in nine complete ventilator circuits, partial circuits and 7, 8, and 9 mm ID endotracheal tubes at flow rates of 20 to 120 liters per minute. We found a statistically significant (p less than 0.01) increase in resistive pressure with increases in flow rate, as the diameter of the ETT decreased, and as each component of the ventilator circuit was added to the ETT. There was a curvilinear increase in resistive pressure to increase in flow rate. However, when resistances were computed, the Bennett cascade "circuit" created higher resistance at 20 lpm than at flow rates up to 120 lpm. The Bennett cascade humidifier added the greatest resistive pressure, 3.5 to 8.5 cm H2O, the Engstrom Edith, 0.5 to 6.5 cm H2O, and the Conchapak added the least, 0.0 to 2.5 cm H2O at flow rates of 20 to 120 lpm. After all the components of the ventilator circuit were attached to the ETTs, there was approximately a 97 to 450 percent increase in resistive pressure compared to the resistive pressure created by the ETTs alone.     

Real-time PCR method for the quantitative analysis of human T-cell receptor gamma and beta gene rearrangements

Analyzing the status of T-cell receptor (TCR) gene rearrangements has been an essential part of deciphering the stages of thymocyte development, understanding the β vs. γδ lineage decision, and characterizing T-cell leukemias. Methods such as PCR and quantitative Southern blotting provide useful information, but also have significant shortcomings such as lack of quantitation in the case of PCR and technical challenges in the case of Southern blotting. Here we describe a real-time PCR method that overcomes many of these shortcomings. This new method shows comparable results for the fraction of unrearranged TCRγ and TCRβ genes in human thymocytes and peripheral blood T cells as Southern blotting, and has the advantages of being simple to perform, highly quantitative, and requiring nanogram quantities of DNA. We also describe a real-time PCR method to quantitate T-cell receptor excision circles formed during TCRβ rearrangements.