Comparative accuracies of a finger blood pressure monitor and an oscillometric blood pressure monitor

A noninvasive blood pressure monitor (Finapres) that uses the methodology of Peaz to continuously display the arterial waveform from the finger has been introduced recently. The Finapres monitor overestimated systolic pressure by 5.8±11.9 mm Hg, while the Dinamap monitor underestimated systolic pressure by –6.9±9.2 mm Hg (P=0.003). Dinamap mean and diastolic pressure biases were less than 2 mm Hg, while the Finapres biases for these variables were significantly greater (7.7±10.0 and 8.2±9.8 mm Hg, respectively). There was no difference in systolic or mean pressure precision between the two devices (approximately 10 mm Hg), but the diastolic precision of the Dinamap unit was superior to that of the Finapres. While in most patients the Finapres monitor provided continuous blood pressure data equivalent to the data from the radial artery, marked bias (>15 mm Hg) was exhibited in 2 patients for all three pressure variables. Despite this bias, blood pressure changes were tracked closely in these 2 patients. We conclude that, in its current form, the Finapres monitor cannot be relied upon independently to accurately measure blood pressure in patients undergoing general anesthesia. Since the Dinamap monitor measures mean pressure reliably and accurately, we suggest that mean blood pressure values between the Finapres and Dinamap monitors be compared to guide one in interpreting Finapres data.Supported in part by a grant from Ohmeda Company, Boulder, CO.Presented in part at the annual meeting of the American Society of Anesthesiologists, New Orleans, October 1989.     

Performance of erroneously filled sevoflurane,enflurane and other agent-specific vaporizers

Objective. Erroneous filling of an agent-specific anesthesia vaporizer may result in concentration and potency outputs that are very different from those expected from the concentration dial setting. Enflurane and sevoflurane have relatively similar saturated vapor pressures (SVPs 175 mmHg and 160 mmHg, respectively, at 20°C) and potencies (MACS 1.68% and 2%, respectively). We derived an equation to relate the vapor concentration output of an agent-specific vaporizer to the gas inflow splitting ratio (SR) created by the vaporizer and the SVP of the potent inhaled agent.Methods. To test the validity of this equation, we filled an Enfluratec 4 enflurane vaporizer with sevoflurane and a Penlon PPV Sigma sevoflurane vaporizer with enflurane and compared the vapor concentration outputs with our predictions.Results. The equation accurately predicted the vapor concentration outputs of the erroneously filled enflurane and sevoflurane vaporizers. The potency (MAC) output of the erroneously filled Enfluratec 4 vaporizer decreased by 22%–33%, and that of the Penlon PPV Sigma sevoflurane vaporizer increased by 21%–31% from those expected from the concentration dial settings.Conclusion. When an agent-specific variable bypass vaporizer is erroneously filled, the vapor concentration outputs can be predicted from the splitting ratio created by setting the vaporizer concentration dial and the SVP of the agent.     

Auscultatory mean blood pressure

This study examined the relationship between direct mean arterial blood pressure and cuff pressure for the maximum acoustic index calculated from the Korotkoff sounds in the dog. The acoustic index was computed by summing the squares of amplitudes in each Korotkoff sound complex, thereby providing a measure of acoustic energy content. Mean arterial pressure was compared with cuff pressure for the maximum acoustic index. Ten mongrel dogs were fitted with appropriately sized blood-pressure cuffs containing a microphone mounted inside the bladder and positioned over the brachial artery. The Korotkoff sounds, cuff pressure, and direct arterial pressure were recorded over a range of mean arterial pressures (23 to 155 mm Hg), achieved by manipulating the depth of anesthesia with halothane. It was found that cuff pressure at the maximum acoustic index overestimated mean arterial blood pressure by a mean of 14% (range, -8 to + 30%). Supported by grant HL31089 from the National Heart, Lung, and Blood Institute and sponsored in part by the Kendall Company, Barrington, IL.     

Methods to produce calibration mixtures for anesthetic gas monitors and how to perform volumetric calculations on anesthetic gases

A simple procedure for making calibration mixtures of oxygen and the anesthetic gases isoflurane, enflurane, and halothane is described. One to ten grams of the anesthetic substance is evaporated in a closed, 11,361-cc glass bottle filled with oxygen gas at atmospheric pressure. The carefully mixed gas is used to calibrate anesthetic gas monitors. By comparison of calculated and measured volumetric results it is shown that at atmospheric conditions the volumetric behavior of anesthetic gas mixtures can be described with reasonable accuracy using the ideal gas law. A procedure is described for calculating the deviation from ideal gas behavior in cases in which this is needed.     

Methods to produce calibration mixtures for anesthetic gas monitors and how to perform volumetric calculations on anesthetic gases

A simple procedure for making calibration mixtures of oxygen and the anesthetic gases isoflurane, enflurane, and halothane is described. One to ten grams of the anesthetic substance is evaporated in a closed, 11,361-cc glass bottle filled with oxygen gas at atmospheric pressure. The carefully mixed gas is used to calibrate anesthetic gas monitors. By comparison of calculated and measured volumetric results it is shown that at atmospheric conditions the volumetric behavior of anesthetic gas mixtures can be described with reasonable accuracy using the ideal gas law. A procedure is described for calculating the deviation from ideal gas behavior in cases in which this is needed.     

Noninvasive Doppler blood pressure monitoring in the monoplace hyperbaric chamber

We describe a noninvasive method of monitoring blood pressure in the monoplace hyperbaric chamber. A standard blood pressure cuff was placed on the patient's arm. A Doppler probe, linked to an ultrasonic Doppler flow detector outside the chamber, was secured over the patient's radial artery. Cuff inflation tubing and the Doppler probe wires were passed into the chamber by modifying a standard disposable hyperbaric intravenous pass-through. Blood pressure readings were determined by inflating and slowly deflating the cuff from outside the chamber while observing the sphygmomanometer within the chamber and listening for the first audible flow signal from the Doppler detector, corresponding to the systolic blood pressure. To minimize the risk of fire in the oxygen-filled monoplace hyperbaric chamber, the patient, Doppler detector, and chamber were grounded. Doppler readings obtained from nine normal subjects whose arterial pressures were being measured with indwelling radial arterial catheters (approved as part of another study by the hospital's Investigational Review Board) compare closely with the subject's blood pressures measured with this noninvasive method: 114±7.6 mm Hg (mean±1 SD) compared to 112±8.1 mm Hg, respectively (n=92 measurements in 8 subjects). We conclude that this noninvasive method of monitoring blood pressure within the monoplace hyperbaric chamber is accurate and suitable for monoplace clinical purposes.This study was supported by a grant from the Deseret Foundation of the LDS Hospital, Salt Lake City, UT.We wish to thank the subjects who volunteered for this investigation, and we appreciate the help of Pam Evans, RRT, and the rest of the hyperbaric staff who assisted in the data collection.     

Comparative effects of cuff size and tightness of fit on accuracy of blood pressure measurements

To determine the effect of snugness of cuff wrap on the accuracy of blood pressure (BP) measurements, we performed two studies on 6 healthy volunteers. In both studies, control values were obtained from the right upper arm with cuffs of appropriate size and snug fit. Study 1 had two phases. In the first, cuffs of appropriate size were wrapped snugly around the upper left arm of seated subjects. The effects of two other degrees of cuff snugness on the measurement of BP were evaluated by placing a filled 250-mL intravenous fluid bag between the cuff and arm over the triceps, measuring BP, then draining the same bag of half its contents and then all of its contents without rewrapping the cuff (loose, very loose fit), each time measuring BP. The second phase of study 1 was identical in procedure, except that the cuffs used on the left arm were one size too small. In study 2, the experimental cuffs were placed just above the right ankle. To alter the signal-to-noise ratio, BP was raised or lowered: the standing position elevated mean BP by an average of 90 mm Hg, and elevation of the legs decreased mean BP by an average of 43 mm Hg. In study 1, we found that appropriately sized cuffs, whether wrapped tightly or loosely, gave correct BP readings. Cuffs snugly wrapped, but too small for the subject, gave high BP readings, on the average by approximately 10 mm Hg. Loose wrapping of small cuffs gave variable results in individual subjects that exaggerated systolic BP from 2 to 80 mm Hg. In study 2, elevating the legs or standing decreased or increased BP consistently. Loose wrapping of appropriately sized cuffs around the ankles of the subjects had no additional significant effect on BP.     

A quantitative evaluation of the Hewlett-Packard 78354A noninvasive blood pressure meter

Oscillometrically determined brachial artery pressures were compared with simultaneous contralateral radial intraarterial pressures in 19 anesthetized adult cardiac surgical patients throughout their surgical procedures, interrupted only by nonpulsatile, low-pressure, low-flow cardiopulmonary bypass. Radial intraarterial pressure values ranged widely for systolic (55 to 207 torr), mean (43 to 141 torr), and diastolic (26 to 106 torr). Both error specification methods proposed by the Association for the Advancement of Medical Instrumentation were used and compared. As expected, error method 1 gave consistently lower mean errors, smaller error standard deviations, and higher correlation coefficients than did error method 2. The errors during time periods immediately before and after cardiopulmonary bypass were compared with those from more quiescent times. Higher mean errors, larger error standard deviations, and lower correlation and regression coefficients were found during those time periods surrounding cardiopulmonary bypass. In general, mean errors were lowest for systolic pressure, followed by mean and diastolic pressures in that order, whereas error standard deviations were smallest for mean pressure, followed by systolic and diastolic pressures. Correlation and regression coefficients were highest for systolic pressure, followed by mean and diastolic pressures. In summary, the oscillometric method provides convenient and reproducible estimates of radial intraarterial pressure during most clinical situations, typically with better accuracy than the auscultatory Korotkoff method. The accuracy and reproducibility are diminished during those periods immediately surrounding cardiopulmonary bypass, perhaps due to direct surgical manipulation of the heart with its attendant rapid changes in cardiac output and blood pressure.     

Pulse oximetry and finger blood pressure measurement during open-heart surgery

Pulse oximeter arterial hemoglobin oxygen saturation (SpO₂) and finger arterial pressure (FINAP) were continuously monitored before, during, and after cardiopulmonary bypass in 15 male patients. SpO₂ was monitored simultaneously with two pulse oximeters, a Nellcor N-100 and an Ohmeda Biox III. The readings obtained from the two pulse oximeters were compared with arterial blood measurements obtained using a CO-oximeter. FINAP was monitored by a prototype device (Finapres) based on the Peaz volume-clamp method. FINAP was correlated with intraarterial pressure (IAP). Both pulse oximeters functioned well before cardiopulmonary bypass. The correlations with CO-oximeter values were 0.927 for the N-100 and 0.921 for the Biox III. Immediately after the onset of cardiopulmonary bypass, the N-100 pulse oximeter stopped displaying values. The Biox III pulse oximeter continued to display values during the cardiopulmonary bypass period; the correlation with CO-oximeter values was 0.813. After cardiopulmonary bypass, the N-100 began displaying values in 2 to 10 minutes. After cardiopulmonary bypass the correlation with CO-oximeter values was 0.792 for the N-100 and 0.828 for the Biox III pulse oximeter. The Finapres finger blood pressure device functioned well in 13 of 15 patients before cardiopulmonary bypass. The mean bias ± precision of FINAP-IAP for mean pressure was 8.3±10.2 mm Hg (SD) and the correlation coefficient was 0.814. During cardiopulmonary bypass, the Finapres device functioned well in 10 of 15 patients. The mean bias precision of FINAP-IAP, for mean pressure in these 10 patients was 6.6±8.7 mm Hg and the correlation coefficient was 0.902. Immediately after cardiopulmonary bypass, the Finapres functioned well in 11 of 15 patients. The mean bias ± precision of FINAP-IAP for mean pressure was 8.6±14.1 mm Hg and the correlation coefficient was 0.533. This study documented that devices for continuous noninvasive monitoring can usually function well under the extreme conditions seen during open-heart surgery. Pulse oximeters may find a place in the monitoring of patients during open-heart surgery, although they cannot totally replace the invasive techniques. Under the conditions of diminished pulsatile peripheral blood flow we observed some differences between the two pulse oximeters.     

Accuracy of four indirect methods of blood pressure measurement,with hemodynamic correlations

In 38 adults undergoing cardiac surgery, 4 indirect blood pressure techniques were compared with brachial arterial blood pressure at predetermined intervals before and after cardiopulmonary bypass. Indirect blood pressure measurement techniques included automated oscillometry, manual auscultation, visual onset of oscillation (flicker) and return-to-flow methods. Hemodynamic measurements or calculations included heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect and intraarterial blood pressure values were compared by simple linear regression by patient and measurement period. Measurement errors (arterial minus indirect blood pressure) were calculated, and stepwise regression assessed the relationship between measurement error and heart rate, cardiac index, stroke volume index, and systemic vascular resistance index. Indirect to intraarterial blood pressure correlation coefficients varied over time, with the strongest correlations often occurring at the first and last measurement periods (preinduction and 60 minutes after cardiopulmonary bypass), particularly for systolic blood pressure. Within-patient correlations between indirect and arterial blood pressure varied widely—they were consistently high or low in some patients. In other patients, correlations were especially weak with a particular indirect blood pressure method for systolic, mean, or diastolic blood pressure; in some cases indirect blood pressure was inadequate for clinical diagnosis of acute blood pressure changes or trends. The mean correlations between indirect and direct blood pressure values were, for systolic blood pressure: 0.69 for oscillometry, 0.77 for auscultation, 0.73 for flicker, and 0.74 for return-to-flow; for mean blood pressure: 0.70 for oscillometry and 0.73 for auscultation; and for diastolic blood pressure: 0.73 for oscillometry and 0.69 for auscultation. The mean measurement errors (arterial minus indirect values) for the individual indirect blood pressure methods were, for systolic: 0 mm Hg for oscillometry, 9 mm Hg for auscultation, -5 mm Hg for flicker, 7 mm Hg for return-to-flow; for mean: -6 mm Hg for oscillometry, and -3 mm Hg for auscultation; and for diastolic: -9 mm Hg for oscillometry and -8 mm Hg for auscultation. Mean measurement error for systolic blood pressure was thus least with automated oscillometry and greatest with manual auscultation, while standard deviations ranging from 9 to 15 mm Hg confirmed the highly variable nature of single indirect blood pressure measurements. Except for oscillometric diastolic blood pressure, a combination of systemic hemodynamics (heart rate, stroke volume index, systemic vascular resistance index, and cardiac index) correlated with each indirect blood pressure measurement error, which suggests that particular numeric ranges of these variables minimize measurement error. This study demonstrates that striking variability occurs in the relationship between indirect and arterial blood pressure measurements, and that the systemic hemodynamic state influences accuracy of indirect blood pressure measurements. When the reproducibility of repeated indirect blood pressure measurements appears unsatisfactory or inconsistent with other clinical observations, clinicians may find that an alternative indirect blood pressure method is a better choice. Of the methods tested, no single indirect blood pressure technique showed precision superior to the others, but two methods yielded data only for systolic pressure. These findings lend support to intraarterial blood pressure measurement in conditions of hemodynamic variability, and suggest the theoretical benefits of continuous indirect blood pressure measurements. Annual meeting of the American Society of Anesthesiologists, New Orleans, LA, Oct 1984.     

Algorithm to identify components of arterial blood pressure signals during use of an intra-aortic balloon pump

Existing bedside cardiovascular monitors often inaccurately measure arterial blood pressure during intra-aortic balloon pump (IABP) assist. We have developed an algorithm that correctly identifies features of arterial pressure waveforms in the presence of IABP. The algorithm is adaptive, functions in real-time, and uses information from the electrocardiographic (ECG) and arterial blood pressure signals to extract features and numeric values from the arterial blood pressure waveform. In its current form, it requires reliable ECG beat detection and was not intended to operate under conditions of extremely poor balloon timing. The algorithm was evaluated by an expert (P.F-C.) on a limited data set, which consisted of 12 1-minute epochs of data recorded from 6 intensive care unit patients. A criterion for selection of patients was that the ECG beat detector could detect ECG beats correctly from the waveforms. The overall sensitivity and positive predictivity for beat detection were 94.04% and 100%, respectively. For feature identification, the overall sensitivity was greater than 89%, positive predictivity was 100%, and the false-positive rate was 0%. The performance measures may be biased by the criteria for patient selection. This approach to identifying waveform features during IABP improves the accuracy of measurements. The utility of using 2 sources of information to improve measurement accuracy has been demonstrated and should be applicable to other physiologic signal-processing applications.     

Self-tuning adaptive control of induced hypotension in humans: A comparison of isoflurane and sodium nitroprusside

Induced hypotension is commonly used during surgery to decrease arterial pressure. Sodium nitroprusside and isoflurane are well-known hypotensive agents. The use of self-tuning adaptive control of induced hypotension was assessed with the use of sodium nitroprusside and isoflurane as hypotensive agents. Nineteen surgical patients were studied during closed-loop control of hypotension induced with sodium nitroprusside. This group of patients was compared with 10 similar patients in whom infusions of sodium nitroprusside were controlled manually by an anesthesiologist. Although the results of the two studies varied, no conclusion could be drawn regarding the superiority of cither manual or closed-loop control. When manual versus automatic control of isoflurane-induced hypotension was assessed in a similar fashion, the two methods of induction were found to be comparable.     

Recognition of mixed anesthetic agents by mass spectrometer during anesthesia

Anesthetic agents are sometimes added to the wrong vaporizer on an anesthesia machine. As a result, the vaporizer may deliver a mixture of anesthetic agents at concentrations inappropriate for use on a patient. However, untoward clinical complications related to vaporizers can be prevented with a time-shared mass spectrometer. This device accurately and rapidly indicates the gases and gas concentrations present in a vaporizer.     

Oxygen uptake and mean blood pressure as indicators of induced hyperthermia

This dog study was designed to identify which of two measurements (oxygen consumption, mean blood pressure) tracked the onset of hyperthermia as reflected by rectal temperature. The animals were anesthetized, paralyzed, and mechanically ventilated. Hyperthermia was induced with 2,4-dinitrophenol (5 mg/kg) injected intravenously in 5 dogs. It was found that the best and earliest predictor of approaching hyperthermia was the increase in oxygen consumption, which increased 10% in 1.72 min. Mean blood pressure was an insensitive indicator of approaching hyperthermia. Rectal temperature, not surprisingly, was found to be a late and undependable early indicator of developing hyperthermia, requiring about 15 minutes to exhibit a definite increase. It is concluded that among these indicators, monitoring oxygen consumption (ml/min) is the most reliable way to identify a metabolic change such as incipient hyperthermia.     

Evaluation of a continuous noninvasive blood pressure monitor in obstetric patients undergoing spinal anesthesia

A noninvasive blood pressure monitor (Finapres) that continuously displays the arterial waveform using the Penaz methodology has recently been introduced into clinical practice. We compared this device with an automated oscillometric blood pressure monitor (Dinamap 1846SX) in 20 patients during spinal anesthesia for nonemergency cesarean section according to a procedure suggested by the Association for the Advancement of Medical Instrumentation. After administration of the spinal anesthetic, the Finapres monitor produced systolic, mean, and diastolic pressure measurements greater than those of the Dinamap monitor (6.6±12.5, 3.3±10.4, and 7.2±9.8 mm Hg, respectively). In most patients, the Finapres measurements were similar to those determined by the Dinamap; however, in 4 patients, mean systolic differences were greater than 20 mm Hg. These patients did not differ from the others in age, height, weight, or baseline blood pressure, and the pressure values recorded by the Finapres monitor were substantially higher than those measured by auscultation in the labor room. In 30% of the patients, the offset between Dinamap and Finapres blood pressure measurements changed markedly over the course of the surgical procedure. The Finapres monitor occasionally stopped working and had to be restarted. In 1 patient (not included in this analysis), the Dinamap monitor was unable to determine the blood pressure due to patient shivering; this did not appear to interfere with the Finapres. We conclude that the Finapres monitor does not consistently provide blood pressure information equivalent to that of the Dinamap in obstetric patients undergoing spinal anesthesia. When the Finapres monitor is used, pressure measurements should be verified periodically by using an auscultatory or oscillometric blood pressure methodology to rule out the presence of large differences, particularly in systolic pressure. The extreme systolic blood pressure discrepancies noted in 20% of the patients studied warrant further evaluation.     

Does measurement of systolic blood pressure with a pulse oximeter correlate with conventional methods?

The pulse oximeter is commonly used in the operating room. We evaluated the use of a pulse oximeter to monitor systolic blood pressure in 20 healthy volunteers and 42 anesthetized patients. We compared the pulse oximeter method of measuring systolic blood pressure with the cuff methods using Korotkoff sounds and Doppler ultrasound as well as with direct pressure measurement through an intraarterial cannula. Systolic blood pressure values obtained by pulse oximeter correlated well with values obtained by other conventional methods. The best correlation was found with Doppler ultrasound (r = 0.996) and the worst with arterial cannulation (r = 0.880). We conclude that this method can be used intraoperatively to measure systolic blood pressure.     

Tissue hypoxia distal to a Peñaz finger blood pressure cuff

The Peñaz finger method to measure blood pressure uses a finger cuff in which the pressure level fluctuates in the vicinity of the mean arterial pressure level and thereby interferes with the circulation of blood to and from the fingertip. We measured capillary blood gases and saturation of hemoglobin in the finger during Peñaz finger blood pressure (PFBP) monitoring to assess the degree to which it impairs circulation in the fingertip. Within 2.5 minutes after initiating PFBP monitoring, capillary oxygen tension (Po₂) had decreased significantly, from about 71 mm Hg to between 49 and 58 mm Hg for up to 50 minutes. These changes were quite different from those occurring when an occlusive tourniquet was applied around the finger. Within 10 minutes of tourniquet application, acidosis (pH 7.25), hypercapnia (carbon dioxide tension, 59.0 mm Hg), and hypoxemia (Po₂, 29 mm Hg) resulted. Within 30 seconds of releasing the PFBP cuff, capillary blood gas values were back to normal. Interspersing 30-second rest periods every 5 minutes during 35 minutes of PFBP monitoring actually decreased capillary oxygen values compared with monitoring without such rest periods. A finger pulse oximeter distal to the PFBP cuff showed desaturation from an average of 97% to 93.7%, with much variability. However, desaturation was statistically significant within 1 minute of application of the PFBP cuff. Within 1 minute the finger volume increased an average of 0.05 ml. After 1 minute the volumes varied widely and, on the average, returned to normal despite continued PFBP monitoring.     

Laboratory evaluation of the vital signs (ICOR) piezoelectric anesthetic agent analyzer

The Vital Signs (ICOR) anesthetic agent analyzer, which measures anesthetic vapor concentration by a piezoelectric crystal technique, was evaluated by using standard-calibration gases to measure the accuracy, response time, gas interference, and water vapor dependence of the analyzer. The accuracy for the measurement of vapor concentration was better than 0.08 vol%. The reproducibility of repeated measures averaged 0.003 vol%. The offsets caused by other gases were 0.02 vol% for water vapor, 0.08 vol% for 70% nitrous oxide, and less than 0.01 vol% for oxygen and carbon dioxide. Response time (10 to 90%) was 475 ms. The agent analyzer may be well suited for monitoring volatile agent concentrations during anesthesia.     

Laboratory evaluation of the vital signs (ICOR) piezoelectric anesthetic agent analyzer

The Vital Signs (ICOR) anesthetic agent analyzer, which measures anesthetic vapor concentration by a piezoelectric crystal technique, was evaluated by using standard-calibration gases to measure the accuracy, response time, gas interference, and water vapor dependence of the analyzer. The accuracy for the measurement of vapor concentration was better than 0.08 vol%. The reproducibility of repeated measures averaged 0.003 vol%. The offsets caused by other gases were 0.02 vol% for water vapor, 0.08 vol% for 70% nitrous oxide, and less than 0.01 vol% for oxygen and carbon dioxide. Response time (10 to 90%) was 475 ms. The agent analyzer may be well suited for monitoring volatile agent concentrations during anesthesia.     

A widely unappreciated cause of failure of an automatic noninvasive blood pressure monitor

Many anesthesiologists have come to depend on automatic noninvasive blood pressure monitoring to obtain blood pressure (BP) readings. A case is presented in which, during a critical phase of the anesthetic, an automatic noninvasive blood pressure (ANIBP) device not only failed to provide meaningful clinical data but, in fact, gave an error message that was misleading. At the time of the message, the patient was noted to be in ventricular trigeminy at a rate of 92 beats/min. It appears that the repetitive beat-to-beat fall in blood pressure due to the dysrhythmia “fooled” the automatic non-invasive blood pressure device's software algorithm into believing that there was an air leak in the system. Thus, in addition to pointing out an unappreciated and potentially troubling device-related critical event, the present case demonstrates the importance of good human factors design for medical devices used in the critical care setting. In particular, the issue is raised of how medical devices should deal with uncertain or potentially misleading data. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of Navy, the Department of Defense, nor the US Government.