Methacholine challenge testing in Reserve Officer Training Corps cadets.

STUDY OBJECTIVE: To determine the prevalence of positive results for methacholine challenge tests in asymptomatic Reserve Officer Training Corps (ROTC) cadets with no history of asthma. DESIGN: Prospective, blinded cohort comparison study. SETTING: Pulmonary diseases clinic in a US Army tertiary-care medical center. PATIENTS: One hundred three college students who were undergoing a physical examination before entering active duty. Group 1 subjects, 58 men and 5 women with an average age of 22.7 years, had no symptoms or personal history of asthma. Group 2 patients, 34 men and 6 women with an average age of 22.2 years, had a history or recent suggestive symptoms of asthma. INTERVENTIONS: Methacholine challenge testing using concentrations of 0.025, 0.25, 2.5, 10, and 25 mg/mL for a total dose of 188 inhalation units or until FEV(1) had declined by 20%. RESULTS: Group 2 had significantly more patients with positive results for methacholine challenge tests or reversible airflow obstruction at baseline (23 of 40 patients [57.5%]) than group 1 (8 of 63 patients [12.7%]; p < 0.05). The cadets in group 1 with positive results for methacholine challenge tests reacted with a 20% decline in FEV(1) at the following concentrations: 25 mg/mL (188 IU), 2 patients; 10 mg/mL (64 IU), 4 patients; and 2.5 mg/mL (13.8 IU), 2 patients. Using values calculated for the provocative concentration of a substance causing a 20% fall in FEV(1) and the new American Thoracic Society criteria, four patients would have borderline bronchial hyperresponsiveness (4 to 16 mg/mL) and three patients (4.8%) would have mild bronchial hyperresponsiveness (1 to 4 mg/mL). CONCLUSIONS: Asymptomatic US Army ROTC cadets with no history of asthma have possible false-positive responses to methacholine at concentrations > 0.25 mg/mL.

The use of pulmonary function testing in piloting, air travel, mountain climbing, and diving.

Millions of people engage in occupational or leisure activities at high altitude or at variable depths below sea level. This article presents an overview of the utility of pulmonary function testing in evaluating complications and other consequences of exposure to high and low pressure environments. The authors review recent literature concerning expected changes in pulmonary function with hyperbaric and hypobaric exposures. The article provides guidance for clinicians evaluating mountain climbers, pilots, aircrew members, airline passengers and deep sea divers.

Vascular rings of the thoracic aorta in adults.

Vascular rings have been well documented to cause respiratory and gastrointestinal symptoms in infants and children. Few reports document symptomatic vascular rings in adults, and most have emphasized dysphagia as the predominant symptom. We present the case of a 36-year-old white male with a double aortic arch and progressive dyspnea on exertion. This led us to review previous reports of vascular rings in adults. Criteria for review consisted of anatomically complete vascular rings of the aortic arch in adults age 18 years or older. We identified 25 prior cases for review and included our recent patient. The most common vascular ring anomalies in our review of adults is double aortic arch (n = 12; 46%) followed by right aortic arch with aberrant left subclavian artery and ligamentum arteriosum (n = 8; 30%). Of 24 patients (66%), 16 were symptomatic. Reported symptoms involving the respiratory tract (n = 10 of 24; 42%) included dyspnea on exertion (n = 5), bronchitis (n = 2), recurrent pneumonia, stridor, and unspecified respiratory ailment (n = 1 each). Dysphagia was less common, occurring in eight patients (33%). Previously proposed mechanisms for respiratory tract symptoms include tracheomalacia, static or dynamic compression of the airways, intravascular volume infusion, and aspiration. We also propose exercise-induced dilatation of the aortic arch and age-dependent changes in thoracic compliance as potential mechanisms of dyspnea.

Improvement in hypoxemia at 4600 meters of simulated altitude with carbohydrate ingestion.

BACKGROUND: Carbohydrate ingestion increases the relative production of carbon dioxide which results in an increase in ventilation in normal individuals. An increase in ventilation at altitude can result in improvement of altitude-induced hypoxemia. HYPOTHESIS: Carbohydrate ingestion will increase the arterial blood oxygen tension and oxyhemoglobin saturation during acute high altitude simulation. METHODS: There were 15 healthy volunteers, aged 18-33 yr, who were given a 4 kcal x kg(-1) oral carbohydrate beverage administered 2.5 h into an exposure to 15,000 ft (4600 m) of simulated altitude (5.5 h after the last meal). Altitude was simulated by having subjects breath a 12% oxygen/balance nitrogen mixture while remaining at sea level. Arterial blood gas samples were drawn at baseline and at regular intervals up to 210 min after carbohydrate ingestion. Subjects were evaluated for AMS by use of the Environmental Symptoms Questionnaire (ESQ) and a weighted average of cerebral symptom score (AMS-C). RESULTS: Baseline PaO2 increased significantly (p < 0.01) from 43.0 +/- 3.0 mmHg at 4600 m before carbohydrate ingestion to 46.8 +/- 6.2 mmHg at 60 min after carbohydrate ingestion. Arterial oxygen saturation rose significantly (p < 0.01) from a baseline of 79.5% +/- 5.1 to 83.8% +/- 6.42 at 60 min. CONCLUSIONS: Carbohydrate consumption significantly increased oxygen tension and oxyhemoglobin saturation in arterial blood of normal subjects during simulated altitude. Effects reached statistical significance across all subjects at 60 min. There was no significant difference in arterial oxygen levels or arterial oxygen saturation in subjects who developed AMS vs. those who did not develop AMS.

Bronchial mucormycosis with progressive air trapping.

A previously healthy 70-year-old woman developed fever, cough, and exertional dyspnea. Her symptoms progressed over a 2-month period despite treatment by her primary care physician with 2 courses of oral antibiotics and the addition of prednisone. Hypoxemia and the finding of hyperglycemia with mild ketoacidosis led to hospital admission. Serial chest radiographs demonstrated diffuse heterogeneous pulmonary opacities and progressive air trapping in the right lower lobe. Fiberoptic bronchoscopy revealed a deep penetrating ulcer with exposed bronchial cartilage of the bronchus intermedius and dynamic airway obstruction with complete closure during expiration. Biopsy of the ulcer revealed Rhizopus arrhizus. Respiratory failure stabilized with the patient on conventional mechanical ventilation and receiving amphotericin B. Before surgery could be performed, Pseudomonas aeruginosa pneumonia and septic shock developed, and the patient died.

Delayed traumatic hemothorax on ticlopidine and aspirin for coronary stent.

A 64-year-old man presented with worsening dyspnea on exertion and hemothorax of the left chest 7 days after discharge from the hospital on ticlopidine and aspirin after coronary stent placement to his left circumflex artery. He had suffered traumatic rib fractures to the seventh, eighth, and ninth left ribs 28 days before this presentation and 21 days before starting the ticlopidine. Results of chest radiography at discharge 7 days earlier while on aspirin and after brief IV heparin had been negative except for minimal atelectasis and rib fractures barely visible on posteroanterior view. The delayed hemothorax had lowered the peripheral blood hematocrit to 23% and required tube thoracostomy drainage and blood transfusion. The delayed traumatic hemothorax in this case occurred on treatment with ticlopidine and did not recur with continuation of aspirin alone.

Lung function during moderate hypobaric hypoxia in normal subjects and patients with chronic obstructive pulmonary disease.

BACKGROUND: We sought to describe changes in spirometric variables and lung volume subdivisions in healthy subjects and patients with chronic obstructive pulmonary disease (COPD) during moderate acute hypobaric hypoxia as occurs during air travel. We further questioned whether changes in lung function may associate with reduced maximum ventilation or worsened arterial blood gases. METHODS: Ambulatory patients with COPD and healthy adults comprised the study populations (n = 27). We obtained baseline measurements of spirometry, lung volumes and arterial blood gases from each subject at sea level and repeated measurements during altitude exposure to 8000 ft (2438 m) above sea level in a man-rated hypobaric chamber. RESULTS: Six COPD patients and three healthy subjects had declines in FVC during altitude exposure greater than the 95% confidence interval (CI) for expected within day variability (p < 0.05). Average forced vital capacity (FVC) declined by 0.123 +/- 0.254 L (mean +/- SD; 95% CI = -0.255, -0.020; p < 0.05) for all subjects combined. The magnitude of decline in FVC did not differ between groups (p > 0.05) and correlated with increasing residual volume (r = -0.455; <0.05). Change in maximum voluntary ventilation (MVV) in the COPD patients equaled -1.244 +/- 4.797 L x min(-1) (95% CI = -3.71, 1.22; p = 0.301). Decline in maximum voluntary ventilation (MVV) in the COPD patients correlated with decreased FVC (r = 0.630) and increased RV (r = -0.546; p < 0.05). Changes in spirometric variables for patients and controls did not explain significant variability in the arterial blood gas variables PaO2, PaCO2 or pH at altitude. CONCLUSIONS: We observed a decline in forced vital capacity in some COPD patients and normal subjects greater than expected for within day variability. Spirometric changes correlated with changes in reduced maximum voluntary ventilation in the patients but not with changes in resting arterial blood gases.

Multiple organ toxicity from addition of erythromycin to long-term lovastatin therapy.

A patient who had taken lovastatin for 7 years received erythromycin before dental procedures. Multiple organ toxicity developed, manifested as rhabdomyolysis, acute renal failure, pancreatitis, ileus, livedo reticularis, and elevated aminotransferase values, without liver injury. No previous reports have identified multiple organ injury of this magnitude. A computer literature search identified only three other reported instances of erythromycin and lovastatin interaction. Manifestations in these previous cases consisted of rhabdomyolysis in all three, as well as elevated aminotransferase values and acute renal failure in two cases. In all the cases, the clinical presentation of organ toxicity occurred after the cessation of erythromycin therapy between day 1 and day 5. Advanced age and chronic renal insufficiency were identified as potential risk factors for drug interaction. Health care professionals should be aware of the potential interaction between these two commonly prescribed drugs, which can mimic sepsis.

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.

Bedside videoscopic placement of feeding tubes: development of fiberoptics through the tube.

OBJECTIVE: Transpyloric small intestine feeding tube placement can be difficult and tedious. Currently accepted techniques are associated with disadvantages and risk. The purpose of this study is to describe the development of a new technique: bedside videoscopic placement using fiberoptics through the tube. DESIGN: Prospective, descriptive case study. SETTING: Intensive care unit in a teaching hospital. PATIENTS: Subjects were divided into two groups: a) group 1: eight healthy volunteers (seven male, one female); b) group 2: nine critically ill patients (six male, three female; eight of these patients were intubated). INTERVENTIONS: Standard 12-Fr (4.0-mm) feeding tubes (n = 19) were placed. Two patients from group 2 had feeding tubes placed on two separate occasions. The feeding tubes were inserted by the oral (n = 8) or nasal (n = 11) route under direct vision, using a 6.7-Fr (2.2-mm) fiberoptic scope through the feeding tube. MEASUREMENTS AND MAIN RESULTS: We visualized enteric structures clearly through the feeding tube in all subjects and patients. Based on visual landmarks, we advanced the feeding tube through the pylorus and into the duodenum in all individuals. Transpyloric tube placement was confirmed videoscopically (n = 19) and radiographically (n = 18). In three subjects from group 1, the feeding tube entered the first part of the duodenum, while, in the remainder of the subjects, the tube passed into or beyond the second portion of the duodenum. In eight (73%) of 11 attempts on the nine critically ill patients from group 2, the feeding tubes were advanced to the distal duodenum or jejunum. The time required for placement in group 2 ranged from 2 to 43 mins (mean 18 +/- 12 [SD]). The feeding tubes remained in place 10 +/- 4 days and patients met their estimated caloric needs within 24 hrs. Residual volumes of nutrition in the small bowel were < 5 mL. There were no documented episodes of aspiration. CONCLUSION: This new technique has the potential for rapid, accurate, and safe feeding tube placement in patients requiring nutritional support.

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.

Sulfasalazine pulmonary toxicity in ulcerative colitis mimicking clinical features of Wegener's granulomatosis.

The centrally accentuated antineutrophil cytoplasmic antibody test (c-ANCA) is widely regarded as a sensitive and specific marker for Wegener's granulomatosis (WG). There are increasing reports, however, of false-positive c-ANCAs, usually in the setting of other vasculidities. We report a case of a 27-year-old man with ulcerative colitis who developed pulmonary symptoms, peripheral nodular lung infiltrates, and an elevated c-ANCA suggesting WG. Chest CT and open lung biopsy specimens were consistent with WG. The symptoms and pulmonary infiltrates resolved after discontinuation of sulfasalazine therapy. The c-ANCA remained elevated due to the occurrence of false-positive values in ulcerative colitis. We conclude sulfasalazine toxicity can mimic clinical aspects of WG and that c-ANCA testing should be interpreted with caution in patients with ulcerative colitis.

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.

Does hemodilution exist? Effects of saline infusion on hematologic parameters in euvolemic subjects.

The effects of intravenous fluids on hematocrit are debated. We sought to determine whether maintenance or bolus fluid therapy causes a significant change in the hematocrit and other hematologic parameters included in the complete blood count. Nine subjects completed a randomized three-period crossover designed trial in which they were given no fluid, maintenance fluid, or a bolus of fluid followed by maintenance fluid. We measured complete blood counts at baseline, 1 hour, 4 hours, and 8 hours. In the bolus fluid trial, the hemoglobin and hematocrit values (mean +/- SEM) decreased by a maximum of 1.5 +/- 0.1 g/dL and 4.1 +/- 0.3% at 1 hour. There was no difference in hemoglobin or hematocrit during the no fluid or maintenance fluid treatments. No significant changes occurred in white blood cell or platelet counts. We demonstrated that maintenance fluid infusions do not significantly after the complete blood count. Saline bolus is associated with a significant decrease in hemoglobin and hematocrit, but these parameters trend toward baseline over time.

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.