Operational medicine experience integrated into a military internal medicine residency curriculum.

The optimal training of physicians should prepare them for the environment in which they will practice. During the past several years, the practice of internal medicine has shifted from a focus on the inpatient setting to one that includes an emphasis on the ambulatory clinic. Military internists must be further prepared to practice medicine with forward units, at field hospitals, and in other operational settings. Community-based teaching programs that reflect present and future practice are increasingly recognized as essential, yet details on the structure and implementation of such programs, especially those designed to teach field and operational medicine, are lacking. The Internal Medicine Residency Program at Walter Reed Army Medical Center has developed and implemented an operational medicine curriculum that includes a field medical training exercise. The program is driven by the residents and chief resident and requires little additional funding. Resident research continues to increase, morale remains high, and the first class to complete the 3-year operational curriculum achieved a 100% pass rate on the American Board of Internal Medicine certification examination. We describe our 3-year experience of implementing this program, with an emphasis on curriculum design and execution, qualitative assessment, and initial lessons learned.

Operational experiences during medical residency: perspectives from the Walter Reed Army Medical Center Department of Medicine.

The preparation of military primary care physicians for practice in operational environments has taken on greater importance during the past decade. The Department of Defense military-unique curriculum identifies the elements that should be incorporated into residency training programs to accomplish comprehensive training in operational matters. We describe efforts to integrate the military-unique curriculum into internal medicine residency, including obstacles encountered, so that other programs may learn from our experience.

Prevalence of pulmonary disorders in patients with newly diagnosed rheumatoid arthritis.

Our objective was to determine the prevalence of airway hyperreactivity (AHR) in patients with newly diagnosed rheumatoid arthritis (RA) who had received no disease-modifying antirheumatic drugs (DMARDs) and to characterise the spectrum of lung diseases identifiable in these patients at the time of presentation. Eighteen consecutive patients with newly diagnosed RA referred to our medical centre's rheumatology clinic over 2 years underwent pulmonary evaluation with arterial blood gas analysis, chest radiographs, spirometry before and after bronchodilator medication, and body plethysmography. They returned on subsequent days in random order for methacholine inhalation challenge (MIC) and eucapnic voluntary hyperventilation (EVH) as bronchoprovocation techniques. One patient had severe obstructive disease at presentation and therefore did not undergo bronchoprovocation. We found a wide variety of pulmonary abnormalities, including two patients with hypoxia (12%), two with obstruction (12%), three with restriction (18%) and four with AHR (23%). The data also suggest a strong association between pulmonary diseases in RA and cigarette smoking. Although no single characteristic lung disease such as AHR was identified in patients presenting with RA, the association between lung disease and cigarette smoking is striking and underscores the need to emphasise smoking cessation in this patient population.

The American College of Physicians' Resident Abstract Competition: success of U.S. military trainees.

Research is a central aspect of internal medicine (IM) training, and accreditation organizations require that residency programs show that their residents participate in scholarly activity. To better understand the research productivity and the quality of research conducted by military IM trainees, we reviewed the records of the American College of Physicians' Resident Abstract Competition from 1995 to 1997. This national competition is prestigious, blindly judged, and highly selective. We found that although military residents account for less than 2% of all U.S. and Canadian IM trainees, they author more than 11% of the abstracts selected for presentation (p < 0.001). We conclude that military IM residents are disproportionately represented compared with their civilian peers in an objective, national competitive forum. This is consistent with the higher scores on in-service examinations and higher board-certification pass rates for military IM residents.

Diagnosing and monitoring the clinical course of chronic obstructive pulmonary disease.

COPD is an extremely common, chronic disorder characterized by a reduction in airflow after the administration of an inhaled bronchodilator as measured by the FEV1. The diagnosis is suspected in patients with a history of several decades of cigarette smoking who present with nonspecific respiratory symptoms. The diagnosis is established by simple forced expiratory spirometry. Baseline evaluation usually includes a chest radiograph and some assessment of functional capacity, either by history or with some form of exercise testing. In patients whose initial FEV1 is more severely reduced or who have significant dyspnea, an arterial blood gas is indicated at baseline. Dyspnea, hypoxemia, or hypercarbia that is out of proportion to the measured FEV1, at either presentation or follow-up, should prompt a thorough evaluation for complicating conditions. There are important roles in health care delivery and chronic disease management strategies for RCPs, primary care providers, and specialty trained pulmonary physicians. The need for repeated, extensive, or expensive testing will be largely driven by patients symptoms but disease monitoring with periodic assessments of dyspnea, functional capacity, and spirometry can be performed without great expense.

Do-not-resuscitate decisions in the medical ICU: comparing physician and nurse opinions.

STUDY OBJECTIVE: To determine how soon after admission to a medical ICU physicians and nurses decide that attempts at resuscitation are inappropriate and how frequently physicians and nurses disagree about do-not-resuscitate (DNR) decisions. DESIGN: Prospective, opinion survey of care providers. SETTING: Ten-bed adult medical ICU in a university-affiliated tertiary care referral hospital. PATIENTS: Consecutive adult medical ICU admissions. INTERVENTIONS: Over 10 months, physicians and nurses were surveyed independently every day regarding their opinions about DNR issues on each patient in the ICU. MEASUREMENTS: ICU day when DNR order was deemed appropriate by either physicians or nurses. RESULTS: Of 368 consecutive admissions, 84 (23%) patients were designated DNR during their ICU stay. In 6 of these 84 cases (7%), the responsible nurse did not agree that DNR orders were appropriate. In the remaining 78 patients designated DNR, the median time for physicians to recommend DNR (median, 1 day; range, 0 to 22 days) was not significantly different from the median time for nurses (median, 1 day; range, 0 to 13 days); (p=0.45). For the 284 patients not designated DNR, physicians and nurses both believed DNR was appropriate in 14 cases (5%), but a DNR order was not written five times (2%) because there was not time to do so and nine times (3%) because patient or family did not concur. Physicians and nurses disagreed about a DNR recommendation in 33 of the 284 patients not designated DNR (12%). Physicians were more likely to believe that DNR was appropriate than were nurses (p<0.0005), with physicians alone recommending DNR 29 times (10%) and nurses alone favoring DNR in four cases (1%). CONCLUSIONS: At our institution, recognition of DNR appropriateness by nurses and physicians occurs over a similar time frame. However, physicians are more likely to recommend DNR in cases of disagreement between nurses and physicians.

Arm span-height relationships in patients referred for spirometry.

Arm span has been proposed as a surrogate for standing height in the prediction of lung volumes in patients with thoracic deformities or who are unable to stand. The relationship between arm span and height has previously been reported as either a fixed ratio unaffected by age or as a regression equation in which the ratio varies as a function of age. We studied the relationship between standing height, arm span, race, sex, and age in 202 patients (ages 20 to 88 yrs) referred for screening spirometry. Multiple linear regression analysis found arm span, race, sex, and age to be predictive of standing height (r2 = 0.8659, p < 0.0001). Subgroup analysis revealed that age was a significant factor among males of either race, but not among females of either race. Fixed arm span to height ratios were also calculated for each group and may be used to estimate standing height with reasonable accuracy except at extremes of stature.

Eucapnic voluntary hyperventilation as a bronchoprovocation technique: development of a standarized dosing schedule in asthmatics.

A variety of dosing schedules have been reported for the hyperventilation method of broncho-provocation testing. To evaluate the effect of challenge technique on the bronchoconstrictive response, we had 16 subjects perform eucapnic voluntary hyperventilation (EVH) with dry, room temperature gas using four different dosing schedules. The hyperventilation challenge dosages included the following: (1) a target minute ventilation (VE) of 20 x FEV1 for 6 min; (2) a target VE of 15 x FEV1 for 12 min; (3) an interrupted challenge with a target VE of 30 x FEV1 for 2 min repeated 3 times; and (4) a target VE of 30 x FEV1 for 6 min. Challenges 2, 3, and 4 gave identical absolute ventilatory challenges (identical factor FEV1 x minutes) but at different VE dosages or time. Challenges 1 and 4 were of identical length, but different target VE. The mean postchallenge fall in FEV1 was 16.6 +/- 10.9%, 11.0 +/- 8.1%, 19.6 +/- 9.9%, and 26.7 +/- 11.3% for challenges 1, 2, 3, and 4, respectively. The response to an identical EVH challenge (FEV1 x 30 for 6 min) was reproducible when performed on separate days. We conclude that the challenge technique used for hyperventilation testing will have a significant impact on the bronchoconstrictive response and must be taken into account when interpreting study results. Tests may be quantitatively comparable over a narrow range of challenge time and VE. We recommend that a 6-min uninterrupted EVH challenge using dry, room temperature gas at a target VE of 30 x FEV1 be adopted as the "standard" challenge.

Pulse oximetry correction for smoking exposure.

Pulse oximetry oxygen saturation (SpO2) does not distinguish carboxyhemoglobin (COHb) from oxyhemoglobin (O2Hb), giving a false impression of the apparent degree of oxyhemoglobin saturation in smokers who have elevated levels of COHb. We questioned whether accounting for smoking exposure history could improve description of pulse oximetry by correcting for COHb levels. We evaluated smoking history and %SpO2 as predictors of %O2Hb and %COHb by CO-oximetry of arterial blood in 18 actively smoking and 18 age-matched nonsmoking patients in a clinical pilot study. The difference between %SpO2 and %O2Hb was significantly greater (p < 0.001) in the smokers (5.6 +/- 3.1) than the nonsmokers (2.1 +/- 2.1). This difference correlated with %COHb (rp = 0.789; p < 0.001) and the smoking exposure score (SES, rp = 0.621; p < 0.001), a six-point index we developed based on whether patients were active smokers, refrained from smoking prior to testing, or were exposed to passive smoking in the home or workplace. The following formula summarizes the correction: %O2Hb = 0.882[%SpO2] - 0.968[SES] + 9.245 (rp = 0.841; SES = 2.478; p < 0.001). This pilot study suggests that smoking exposure history correlates with COHb levels and that correction for smoking exposure improves the accuracy of pulse oximetry.

Effect of upright and supine posture on hypoxemia during air transport.

BACKGROUND: Change in body position can cause hypoxemia at sea level in patients with lung diseases. Because of concern for the added risk of hypoxemia during air transport, we investigated the effect of body position on arterial oxygen partial pressure (PaO2) in individuals with lung disease under conditions of hypobaric hypoxia. METHOD: The study groups consisted of 8 patients with chronic obstructive lung disease, 4 patients with interstitial lung disease, and 6 healthy subjects. We obtained samples from radial artery catheters at sea level (SL) and altitude (ALT) simulation of 8000 ft (2438 m) in a hypobaric chamber in supine and upright postures. RESULTS: Altitude exposure did not result in a significant change in mean supine minus mean upright PaO2 (dPaO2); however, some individuals had large changes at SL. Moreover, the variance for dPaO2 was significantly smaller at ALT compared to SL with all groups combined (F test, p < 0.05). We found no correlation between dPaO2 at SL vs. ALT (p = 0.293; r = 0.262; n = 18). At both SL and ALT, dPaCO2 correlated negatively with dpH. At SL, dPaO2 did not correlate with either dPaCO2 or dpH; at ALT dPaO2 correlated with dpH (p < 0.05) and correlated negatively with dPaCO2 (p < 0.01). CONCLUSION: We conclude that significantly less postural variation in PaO2 occurs at moderate ALT compared to SL. In our patients with diffuse bilateral pulmonary disease, postural change did not contribute significantly to hypoxemia experienced at ALT. We infer that greater ventilatory response to hypoxemia at ALT in either posture may explain this finding.

Interpretation of eucapnic voluntary hyperventilation in the diagnosis of asthma.

Eucapnic voluntary hyperventilation (EVH) of dry gas is a physiologic bronchoprovocation challenge useful in the diagnosis of asthma. To determine the best parameter and threshold for diagnosis and the proper timing of postchallenge measurements, we reviewed 120 challenges, comparing the decrement from baseline in FVC, FEV1, mean forced expiratory flow during the middle half of the FVC (FEF25-75%), and peak expiratory flow rate (PEFR) each at 0, 5, 10, and 20 min postchallenge. After adjustment to a standard minute ventilation of 30 times the baseline FEV1 for 6 min, the mean response by 90 mild asthmatics differed from 30 normal subjects in all four parameters (p < 0.0001). In asthmatics, maximum decline from baseline (mean +/- SEM) was as follows: FVC, 12.1 +/- 1.2%; FEV1, 19.7 +/- 1.7%; FEF 25-75%, 33.5 +/- 2.5%; and PEFR, 29.0 +/- 1.9%. Normal subjects had a maximum fall as follows: FVC, 2.9 +/- 0.7%; FEV1, 3.8 +/- 0.7%; FEF25-75%, 11.8 +/- 2.0%; and PEFR, 11.5 +/- 1.0%. Based on comparison of receiver operator characteristic curves, FEV1 was more accurate than FEF25-75% and equivalent to FVC and PEFR. A threshold of 10% change or greater in FEV1 had a specificity of 90%, with a sensitivity of 63.3%. A threshold of 15% or greater had a specificity of 100%, with a sensitivity of 53.3%. The FEV1 fell by 10% or more in 55 of 90 asthmatics at 5 or 10 min after hyperventilation. Measurements at 0 or 20 min added two additional positive responses. We conclude that in the proper clinical setting, subjects whose FEV1 declines by 10% or more at 5 or 10 min after EVH should be diagnosed as having asthma.

The refractory period after eucapnic voluntary hyperventilation challenge and its effect on challenge technique.

To evaluate whether there is a refractory period (RP) after hyperventilation challenge, we compared the bronchoconstrictive response to repetitive eucapnic voluntary hyperventilation challenge with dry, room temperature air (EVH). The serial challenges were identical with 11 known asthmatics hyperventilating for 6 min at a target minute ventilation of 30 times their FEV1 measured before either challenge. There was a significant difference between the mean postchallenge fall in FEV1 to the initial EVH challenge (27.4 +/- 9.8%) and the response to the second EVH challenge (16.1 +/- 5.9%) (p = 0.0001), indicating refractoriness. We then evaluated whether 6 min of uninterrupted EVH challenge gives a similar bronchospastic response to that which results from an equivalent (by total minute ventilation) interrupted challenge of 2 min of EVH repeated three times. The mean post-challenge fall in FEV1 in response to this interrupted challenge was 18.9 +/- 10.6%, which was significantly different from the 27.4% fall in response to 6 consecutive minutes of EVH (p = 0.036). This study demonstrates that there is a refractory period after repeated EVH challenges and this refractoriness affects the response to interrupted, or dosed, EVH challenge.

The preflight evaluation. A comparison of the hypoxia inhalation test with hypobaric exposure.

STUDY OBJECTIVES: We sought to compare arterial oxygen partial pressure (PaO2) relationships between a 15.1% hypoxia inhalation test (HIT) at sea level and a hypobaric chamber exposure equivalent to 2,438 m (8,000 feet) of altitude above sea level in patients with chronic obstructive pulmonary disease (COPD) and healthy subjects. DESIGN: Comparison of physiologic variables before and during intervention. SETTING: A referral-based pulmonary disease clinic at a US Army medical center in a metropolitan area. SUBJECTS: The study included three groups: group 1, 15 patients, 3 women and 12 men, with COPD (forced expiratory volume in the first second [FEV1, mean +/- SD], 41 +/- 14% of predicted); group 2, 9 healthy men; and group 3, 18 men with COPD (FEV1, 31 +/- 10% of predicted) previously reported in detail. INTERVENTIONS: We evaluated each group at sea level followed by one of two different types of hypoxic exposures. Group 1 received exposure to 15.1% oxygen at sea level, the HIT. Groups 2 and 3 received hypobaric chamber exposure equivalent to 2,438 m (8,000 feet) above sea level. MEASUREMENTS AND MAIN RESULTS: For all three groups combined, the arterial oxygen tension at sea level (PaO2SL) explained significant variability in PaO2 during hypoxic exposure according to the following formula: PaO2 during exposure = 0.417 (PaO2SL)] + 17.802 (n = 42; r = 0.756; p < 0.001). Neither the type of hypoxic exposure (HIT vs hypobaric), status as patient vs control, sex, nor age explained significant variability in PaO2 during hypoxia exposure after inclusion of PaO2SL as a covariate in analysis of variance. Subsequent analysis revealed that forced expiratory spirometric variables FEV1 and FEV1 to FVC ratio served as second order covariates with PaO2SL to improve description of PaO2 during hypoxia exposure for the combined samples (n = 42; p < 0.05). Analysis of residuals from regression analysis revealed approximately normal distribution. CONCLUSIONS: The PaO2 relationships did not differ between the 15.1% HIT at sea level and hypobaric exposures of 2,438 m (8,000 feet) above sea level. Normal subjects and patients with COPD formed a single relationship. The present study extends descriptive models to a larger range of subjects. Regression models have definable accuracy in predicting PaO2 during hypoxia exposure that increases with inclusion of spirometric variables.

Impact of using stated instead of measured height upon screening spirometry.

This study examined the impact of using stated height instead of measured height on predicted normal values and clinical interpretation of screening spirometry in an outpatient referral population. In a prospective fashion, we evaluated 210 patients, 20 to 89 yr of age, referred for spirometry to our pulmonary function laboratory by obtaining both stated height (HTs) and measured height (HTm). The mean difference between stated and measured height progressively increased with age, from 0.80 cm (20 to 29 yr; p = 0.01) to 5.70 cm (80 to 89 yr; p < 0.001). For men and women, use of HTs instead of HTm produced a mean difference for all ages in computing predicted FEV1 and FVC values of 3.9 and 4.3%, respectively. This effect was more prominent in the older age groups (80 to 89 yr, n = 30); mean differences were 11.0% (211 ml) and 11.7% (303 ml), respectively. Use of HTs instead of HTm altered the detection of restriction by reduced FVC in 17 patients and the detection of obstruction by reduced FEV1/FVC ratio in four patients. Use of HTs altered the clinical assessment of severity by FEV1 in 15 of 108 (13.9%) obstructed patients and altered the assessment of severity by FVC in 11 of 32 (34.4%) restricted patients, with older patients more frequently affected than younger patients. We conclude that the use of stated height instead of measured height in the performance of screening spirometry can have significant impact on the calculation of predicted normal values. These discrepancies can potentially influence the clinical interpretation of screening spirometry, affecting the detection of abnormality and the assessment of severity of disease, particularly among older patients.

Sarcoidosis complicated by chylothorax.

Chylothorax is a rare complication of sarcoidosis; only one well-documented case has been described previously. Before chylothorax is diagnosed in a patient with sarcoidosis, infection and malignancy need to be aggressively excluded as possible diagnoses. We report the case of a 34-year-old black woman with sarcoidosis confirmed by lung, pleural, and mediastinal lymph node biopsies whose clinical course was complicated by chylothorax. Oral corticosteroid treatment resulted in prompt resolution of the chylothorax.

Refractory period during provocation with eucapnic hyperventilation and methacholine.

Eucapnic voluntary hyperventilation (EVH) and methacholine inhalation challenge (MIC) both cause bronchoconstriction in asthmatics. A refractory period, or time when the response to bronchoprovocation in a series of challenges is diminished, has been found after hyperventilation or exercise but not after MIC. We investigated whether EVH or MIC blunted the response to the other test. Sixteen asthmatics were studied on 2 d, taking both tests each day. They were randomized to either EVH or MIC first on Day 1, then the opposite order on Day 2, 6 to 14 d apart. After EVH as a first test, the mean decline in FEV1 from baseline was 18.66 +/- 4.76% (mean +/- SEM), but when EVH followed MIC, the response to EVH was reduced by 30%, to a decline in FEV1 of only 13.02 +/- 3.75% (p = 0.0026). During MIC, the mean provocation dose to cause 20% decrease in FEV1 (PD20) given as the initial challenge was 54.77 +/- 21.60 breath units, compared with 46.94 +/- 19.55 breath units when MIC followed EVH (p = 0.54). However, the subset of patients most sensitive to methacholine (PD20 < 0.1 breath unit) had changes suggestive of a refractory period after EVH, with a mean increase in the PD20 from 0.06 +/- 0.01 to 3.35 +/- 1.43 (p = 0.069). Our data show that MIC attenuates the response to subsequent challenge with EVH. Conversely, EVH may only affect subsequent MIC in those most sensitive to methacholine.

Eucapnic voluntary hyperventilation as a bronchoprovocation technique. Comparison with methacholine inhalation in asthmatics.

Methacholine inhalation challenge (MIC) is probably the most widely used and best standardized test for nonspecific bronchoprovocation challenge (BPC). There has been increasing interest in developing "physical" stimuli such as eucapnic voluntary hyperventilation (EVH) with dry gas to assess airway hyperreactivity (AHR), because of inherent problems with using a pharmacologic agent in epidemiologic surveys. To our knowledge, no studies exist that compare MIC with EVH in known asthmatics. We conducted a prospective, randomized, crossover trial with a group of subjects (n = 16) who met the American Thoracic Society definition of asthma with these objectives: (1) to compare the sensitivity of EVH with MIC; (2) to compare the quantitative response of one test with the response to the other challenge; and (3) to correlate the response of both tests with symptoms, serum IgE levels, and serum eosinophil counts. We found that (1) EVH was positive in 75 percent of cases and MIC was positive in 81 percent of cases; one subject reacted to EVH but not to MIC and vice-versa. (2) The quantitative response to one test correlated with the response to the other test (r = -0.60, p = 0.01). (3) There was a correlation between severity of asthma symptoms and the response to EVH (r = 0.62; p = 0.01), but not to MIC. (4) Response to MIC (log PD20), but not EVH, correlated with serum IgE level (r = -0.53, p = 0.04). We suggest that EVH may be used for the initial assessment of AHR in the evaluation of asthma. Eucapnic voluntary hyperventilation is a sensitive measure of AHR and it correlates well with symptoms. Furthermore, though these points were not addressed in our study, it is more physiologic than MIC, and it is easy and less expensive to perform.

Use of do-not-resuscitate orders in an intensive care setting.

STUDY OBJECTIVES: Do-not-resuscitate (DNR) orders have been espoused for the enhancement of patient autonomy, avoidance of futile medical intervention, and cost containment. Outcomes of cardiopulmonary resuscitation (CPR) in the intensive care setting have been dismal, with few patients surviving to discharge. This study compares patients who died in medical and surgical ICUs in a DNR status with those who died after attempted CPR. DESIGN: Retrospective chart review of all patients who died in the medical and surgical ICU in a 2-year period. MEASUREMENTS AND RESULTS: A total of 195 cases were reviewed during the specified time period; 108 patients had undergone attempted resuscitation, and 87 patients died in a DNR status. There were no significant differences when preadmission disability, source of admission, location (medical ICU vs surgical ICU), chronic medical conditions, acute diagnosis, sex, and weight were considered. Patients who were designated "DNR" were significantly older than patients who underwent CPR (mean age, 65.7 years vs 58.9 years; p = 0.005). The DNR-designated patients were in general more severely ill as measured with the APACHE II system (mean score, 23.5 vs 20.7; p = 0.004), which was accounted for primarily by greater alterations in level of consciousness as measured with the Glascow Coma scale (mean score, 10.0 vs 12.1; p = 0.001). CONCLUSIONS: Among patients dying in the medical and surgical ICUs in the authors' institution, only age and level of consciousness discriminated patients who died in a DNR status from those who died after attempted CPR.

Water loss without heat flux in exercise-induced bronchospasm.

We identified inspired gas conditions that result in no net respiratory heat loss, an isenthalpic condition, but induce a mucosal loss of water. Inspired gas at 37 degrees C with 47 mm Hg water vapor pressure, 56 degrees C with 38 mm Hg; and 78 degrees C with 27 mm Hg has the same heat content as fully saturated air at body temperature. In four normal subjects hyperventilating at a minute ventilation of 30 times their FEV1 for 6 min, expired temperatures at the mouth averaged 39 degrees, 43 degrees, and 43 degrees C for the three conditions. Retrotracheal esophageal temperatures did not fall in any subject, thereby demonstrating the absence of significant airway cooling. Nine subjects with exercise-induced bronchospasm were tested under the same conditions. Baseline functions showed an FEV1 of 85 +/- 10% of predicted (mean +/- SD), FVC, 98 +/- 13% of predicted, and FEV1/FVC, 79 +/- 4% of predicted. The asthmatic subjects demonstrated postchallenge mean falls in FEV1 of 3.4%, 6.2%, and 10.1% for the three conditions, with bronchospasm increasing as the temperature of the inspired air increased (p = 0.001). The amount of respiratory water lost from the respiratory mucosa significantly correlated with the resultant bronchospastic response as measured by the fall in FEV1 (p = 0.017), but the net respiratory heat lost did not significantly correlate (p = 0.113). This study demonstrates that bronchospasm can be induced without significant respiratory heat loss or airway cooling and suggests that it is proportional to the amount of water lost from mucosal surfaces.