Biomedical subjects

Jay A Johannigman

Publications and source records attributed to Jay A Johannigman.

11 recordsLinked to original sources

PubMed2005

Disaster preparedness: it's all about me.

An individual's preparation to manage an incident involving chemical, biologic, radiologic, nuclear, or explosive events requires a thorough and prepared understanding of the nature of these events. The purpose of this article is to discuss the preparation required to successfully manage the field and pre-hospital phases of a mass casualty event involving intentional weapons. The range of available response teams as well as the role of the United States military is discussed, including recent innovative educational programs initiated to meet this need.

Disaster Planning↗

PubMed2005

The role of repeat angiography in the management of pelvic fractures.

BACKGROUND: Angiographic embolization has emerged as the treatment modality of choice for bleeding pelvic fractures. The purpose of this study is to identify potential indicators for ongoing pelvic hemorrhage despite initial therapeutic or non-diagnostic angiography. METHODS: The trauma registry of a Level I trauma center was used to identify patients with pelvic fractures between January 2000 and June 2002. Records were reviewed for demographics, severity of injury, hemodynamic status, initial and subsequent base deficit, blood and fluid requirements, length of stay, and mortality. Statistical analysis was performed using Student's t test, and univariate and multivariate analysis, significance was assigned to p < or = 0.05. RESULTS: During the study period, 678 patients had pelvic fractures. Angiography was performed in 31 (4.6%) of these patients. Arterial hemorrhage was diagnosed initially on 16 (51.6%) patients requiring embolization. Three (18.8%) of these embolized patients required repeat angiography and embolization due to ongoing pelvic hemorrhage. Of the initial 15 patients with negative angiograms, five (33.3%) had repeat angiograms due to continued hypotension and acidosis. Four (80.0%) of these five patients were found to have arterial hemorrhage requiring embolization. Of the seven (22.6%) patients requiring repeat angiography for control of ongoing pelvic hemorrhage, three independent factors were predictive: continued or recurrent hypotension (SBP < 90), absence of intra-abdominal injury, and persistent base deficit of 10 for greater than 6 hours. The presence of all three independent predictors was associated with a 97% probability of pelvic bleeding (p = 0.001). CONCLUSION: Angiographic embolization is highly effective in controlling arterial bleeding associated with pelvic fractures. However, repeat angiography should be performed in patients with pelvic fractures with ongoing evidence of hemorrhage demonstrated by persistent base deficit and hypotension once other potential sources of bleeding have been excluded.

Acidosis↗

PubMed2005

The role of ventilator graphics when setting dual-control modes.

Dual-control ventilation modes were introduced with the goal of combining the advantages of volume-control ventilation (constant minute ventilation) and pressure-control ventilation (rapid, variable flow). Dual-control ventilation modes have gained popularity despite little evidence to support routine use. The individual operation and response of the dual-control modes must be understood by the clinician to allow safe and effective use. Graphic displays of pressure, volume, and flow can aid the clinician in detecting inappropriate use of dual-control modes and adjusting settings accordingly. Inspecting the waveforms will lead clinicians to the realization that dual-control does not guarantee a set tidal volume and that variability in delivered tidal volume is greater with dual-control than with pressure control. These realizations have important implications for low-tidal volume strategies.

Data Display↗

PubMed2004

The measurement of energy expenditure.

Proper nutrition support depends upon the clinician's ability to estimate the patient's energy expenditure. The accuracy of estimation is inversely proportional to the severity of the patient's illness. This fact has spurred academic and industry groups to pursue the measurement of energy expenditure. Harris and Benedict used indirect calorimetry to develop their now-famous equation nearly 100 years ago. The concept of indirect calorimetry is simple; if you know the concentration of inspired gases and expired gases, along with the flow, you can determine the amount of a gas consumed or produced. The complexity and expense of indirect calorimeters suggest that this simple concept is technically challenging. Because we desire to know the energy expenditure of the most critically ill patients, indirect calorimetry is further confounded by the presence of oxygen and mechanical ventilation. This paper will discuss the myriad of variables and obstacles that complicate the measurement of energy expenditure and will suggest methods to avoid or overcome them.

Journal Article↗

PubMed2004

What is the evidence base for the newer ventilation modes?

New ventilation modes are introduced as answers to current clinical conundrums but also as marketing tools. Rarely is a mode introduced with sound evidence from bench, animal, and patient testing. The industry cannot support the extensive testing required to demonstrate the superiority of a new mode or technique. Instead, clinicians often rely on their own experience and the results of small observational trials that show positive effects on surrogate variables such as oxygenation and work of breathing or less tangible variables such as patient comfort. This report reviews the newer ventilation modes and attempts to find the evidence among the claims and confusion.

Evidence-Based Medicine↗

PubMed2003

Influence of low tidal volumes on gas exchange in acute respiratory distress syndrome and the role of recruitment maneuvers.

UNLABELLED: BACKGROUND Use of a low tidal volume (V(T)) strategy in the treatment of acute respiratory distress syndrome can lead to a decrease in oxygenation. This study evaluated the safety and efficacy of a recruitment maneuver (RM) in this setting. METHODS: Twelve patients with acute respiratory distress syndrome were studied within 48 hours of diagnosis. Baseline gas exchange, hemodynamics, and respiratory mechanics were determined and patients were placed on a V(T) of 6 mL/kg. Measurements were repeated and an RM of 30 cm H20 for 40 seconds was performed. Measurements were repeated at 30 minutes and 2 hours post-RM. RESULTS: Decreasing V(T) resulted in a decrease in arterial oxygenation (from 91 +/- 9 mm Hg to 75 +/- 9 mm Hg, p < 0.01), an increase in shunt (from 19 +/- 3.7% to 23 +/- 5%, p < 0.01), and a decrease in lung compliance (from 37 mL/cm H2O to 33 mL/cm H2O, < 0.05). At 30 minutes post-RM, oxygenation improved to 99 +/- 16 mm Hg, shunt decreased to 17 +/- 3%, and lung compliance improved to 39 mL/cm H2O (p < 0.05). Two hours later, oxygenation fell (86 +/- 12 mm Hg), shunt increased (20 +/- 3%), and compliance diminished (36 mL/cm H2O). There were no hemodynamic or barotraumatic complications. CONCLUSION: An RM transiently improves gas exchange during low V(T)ventilation. RMs are well tolerated and no hemodynamic consequences were seen.

Accidents, Traffic↗

PubMed2002

Transport ventilators.

Today there are a number of automatic resuscitators and simple and complex transport ventilators on the market. The user must consider the purpose of the device, the patient population to be ventilated and the capabilities of the individual devices before purchasing a transport ventilator.

Critical Illness↗

PubMed2002

Pelvic fracture in the elderly is associated with increased mortality.

OBJECTIVE: The elderly population is currently the fastest growing sector in America. The purpose of this study was to examine the age-related outcome in patients after blunt pelvic injury. METHODS: All patients admitted with a pelvic fracture during a 5-year period were identified from the trauma registry. Data retrieval included: demographics, shock (BP < 90 mm Hg) on admission, injury severity score (ISS), abbreviated injury score (AIS) for head, chest, and abdomen, intensive care unit (ICU) length of stay (LOS), hospital LOS, and mortality. All pelvic fracture patterns were classified. Patient data were then stratified by age for comparison: young (< 55 years) and elderly (> or = 55 years). Statistical analysis was performed using the Student t test, Wilcoxon rank-sum test, multiple logistic regression analysis, and chi-square test with significance set at P <.05. RESULTS: Three hundred five patients sustained a pelvic fracture (young [n = 248, 81.3%]; elderly [n = 57, 18.7%]). The only predictor of mortality was age. The 2 groups differed by gender (elderly = 54.4% females; young = 62.5% males) but not frequency of shock, ISS, or AIS for head, chest, and abdomen. Motor vehicle collision was the most common mechanism of injury (elderly = 68.4%; young = 73.8%). Lateral compression was the most common fracture pattern in both groups (elderly = 54.4%; young = 45.6%). There was no difference in transfusion (elderly = 2.5 +/- 0.7 vs young = 2.0 +/- 0.3; ns) but the elderly group was more frequently admitted to the ICU (elderly = 61.4% vs young = 46.8%; P =.065). Significantly more of the elderly group had a diagnosis of cardiovascular disease (43.9% vs 10.1%, P <.001) and diabetes mellitus (10.5% vs 2.4%, P <.014). Mortality was significantly greater in the elderly group (12.3% vs 2.3%). CONCLUSION: Elderly patients sustaining a pelvic fracture were more likely to have a lateral compression fracture pattern, longer hospital LOS, and die despite aggressive resuscitation. This difference in outcome should help trauma surgeons recognize that the elderly patient sustaining a pelvic fracture is at increased risk of death.

Adult↗

PubMed2002

Closed-loop mechanical ventilation.

Closed-loop mechanical ventilation encompasses a plethora of techniques, ranging from the very simple to the relatively complex. In the simplest form, closed-loop ventilation is the control of one output variable of the mechanical ventilator based on the measurement of an input variable. An example would be pressure support ventilation, in which flow (output) is constantly changing to maintain pressure (input) constant throughout inspiration. More complex forms of closed-loop ventilation involve measurement of multiple inputs (eg, compliance, oxygen saturation, respiratory rate) to control multiple outputs (eg, ventilator frequency, airway pressure, tidal volume). The latter type of control more closely mimics the ventilatory control and response of human physiology. This review discusses both currently available closed-loop ventilation techniques and those only available outside the United States, along with some cutting-edge techniques that have only limited use. The operation, theoretical advantages, and limitations of each technique are reviewed. When available, the literature supporting or refuting each technique will be reviewed, but, unfortunately, little has been published on certain techniques.

Algorithms↗

PubMed2002

Imposed work of breathing during ventilator failure.

INTRODUCTION: Ventilators possess an anti-asphyxia valve that allows spontaneous breathing of ambient air during ventilator failure. This study examined the imposed work of breathing and pressure-time product of 8 critical care and 9 portable ventilators, using a laboratory simulation of spontaneous breathing during ventilator failure. METHODS: A test lung was modified to simulate spontaneous breathing with a tidal volume of 0.5 L and peak inspiratory flow of 60 L/min. A pneumotachograph and pressure tap were placed at the proximal airway between the breathing circuit and endotracheal tube. Flow was derived from the pressure drop across the pneumotachograph. Signals were amplified, integrated, and saved to a spreadsheet program, and imposed work of breathing and pressure-time product were calculated. Also measured were the inspiratory pressure required to open the anti-asphyxia valve (cracking pressure), time to cracking pressure, maximum negative inspiratory pressure, and time to maximum negative inspiratory pressure. RESULTS: For the critical care ventilators the mean +/- SD imposed work of breathing ranged from 213.07 +/- 3.53 to 890.63 +/- 0.88 mJ/L and the pressure-time product ranged from 2.67 +/- 0.01 to 13.37 +/- 0.01 cm H(2)O x s/L. For the portable ventilators the mean +/- SD imposed work of breathing ranged from 361.37 +/- 1.22 to 969.60 +/- 22.70 mJ/L and the pressure-time product ranged from 4.52 +/- 0.01 to 16.70 +/- 0.37 cm H(2)O x s/L. CONCLUSIONS: Spontaneous breathing during ventilator failure may impose work approximating the physiologic work of breathing. This imposed work may prevent effective breathing through the anti-asphyxia valve during mechanical ventilator failure due to electrical failure. These results reinforce the need to properly monitor mechanically ventilated patients and to have in place sufficient back-up power supplies and a method of manual ventilation.

Equipment Design↗

PubMed2002

Battery duration of portable ventilators: effects of control variable, positive end-expiratory pressure, and inspired oxygen concentration.

INTRODUCTION: Portable ventilators require battery power during transport or when alternating current is unavailable. Manufacturers report battery duration at nominal ventilator settings. METHODS: We studied the effects of control variable (pressure control vs volume control), positive end-expiratory pressure (PEEP), and fraction of inspired oxygen (F(IO)(2)) on the battery duration of 8 portable ventilators: Achieva, HT50, iVent201, LTV1000, TBird Advanced Ventilator System (AVS), Avian, Uni-Vent 750, and Uni-Vent 754. Each ventilator was set to ventilate a test lung at a rate of 10 breaths/min, tidal volume of 750 mL, and inspiratory time of 1.5 s, with volume-controlled ventilation and then pressure-controlled ventilation (PCV), if available. F(IO)(2) was set at 0.21 and then 1.0. PEEP was set at 0, 10, and then 20 cm H(2)O. Test lung compliance and resistance were set at 20 mL/cm H(2)O and 5 cm H(2)O/L/s, respectively. Five trials were performed with each portable ventilator, with each combination of settings. Time to low-battery alarm, battery-empty alarm, and failure to ventilate the test lung were recorded. Portable ventilator performance during the trials was determined by continuous recording of tidal volume. RESULTS: The battery duration of pneumatically driven portable ventilators is longer than that of electrically driven portable ventilators. The battery duration of pneumatically driven portable ventilators is minimally affected by ventilator settings. The battery duration of electrically driven portable ventilators is shortened by use of PCV, increasing PEEP, and increasing F(IO)(2). Compared to zero PEEP, PEEP of 20 cm H(2)O reduced battery duration with HT50 (40%), LTV1000 (37%), TBird AVS (34%), and Achieva (15%). Compared to volume-controlled ventilation, PCV reduced battery duration with the LTV1000 (48%) and TBird AVS (18%). Compared to F(IO)(2) of 1.0, F(IO)(2) of 0.21 reduced battery duration with the Uni-Vent 754 (37%). Compared to F(IO)(2) of 0.21, F(IO)(2) of 1.0 reduced battery duration with the LTV1000 (17%) and TBird AVS (15%). The iVent201 was unable to deliver the set tidal volume with PCV and 20 cm H(2)O PEEP. Low-battery alarms functioned properly on all the ventilators. CONCLUSIONS: Battery duration differs greatly among the portable ventilators tested. Clinicians must be aware that portable ventilator battery duration is affected by control settings, lung impedance characteristics, and portable ventilator characteristics. Battery duration may be shorter than that reported in the operator's manual for each portable ventilator tested.

Electric Power Supplies↗