Feasibility of home delivery of pemetrexed in patients with advanced non-squamous non-small cell lung cancer.

OBJECTIVES: To evaluate the feasibility and adherence to home delivery (HD) of pemetrexed maintenance treatment in patients with advanced non-squamous non-small cell lung cancer (nsqNSCLC). MATERIALS AND METHODS: Exploratory, prospective, single-arm, Phase II study in advanced nsqNSCLC patients, with an Eastern Cooperative Oncology Group (ECOG) performance status of 0/1 that did not progress after 4 first-line induction cycles of a platinum doublet. The first cycle of pemetrexed (500mg/m(2)) was hospital administered, further cycles were HD until progressive disease or discontinuation. Feasibility was assessed by the adherence rate to HD (probability of reversion to hospital administration or treatment discontinuation due to HD) as primary endpoint, and by health-related quality-of-life (HRQoL: EQ-5D, lung cancer symptom scale [LCSS]), satisfaction with HD, overall survival (OS), and safety. RESULTS: 52 patients (UK & Sweden) received a median of 4 (range 1-19) pemetrexed maintenance cycles. Adherence rate up to Cycle 6 was 98.0% (95% confidence interval [CI]: 86.4%, 99.7%). All but 2 patients remained on HD. 1 patient discontinued after Cycle 1 (patient decision), and 1 after Cycle 6 (non-compliance with oral dexamethasone). 87% (33/38) of the patients preferred home to hospital treatment and in 90% (28/31) of cases, physicians were satisfied with distant management of patients. During HD Cycles 2-4 mean change from baseline ranged from 3.0 to 7.7 for EQ-5D visual analog scale. The 6-month OS rate was 73% (95% CI: 58%, 83%). 1 patient had an HD-related adverse event (device-related infection, Grade 2) and 1 patient died after Cycle 1, before HD, due to a possibly drug-related atypical pneumonia. CONCLUSION: HD of pemetrexed maintenance treatment in patients with advanced nsqNSCLC was feasible, safe, and preferred by patients, while maintaining HRQoL. Physicians were satisfied with distant patient management.

Comparison of 1- and 2-year screening intervals for women undergoing screening mammography.

We compared the long-term impact of 1- and 2-year screening mammography intervals using prognostic, screening, and outcome information for women aged 50-74 years obtained from the Screening Mammography Program of British Columbia in two time periods, prior to 1997 (policy of annual mammography) and after 1997 (biennial mammography). Survival was estimated for both periods using a prognostic model and the expected rate of interval and screen-detected cancers. The likelihood of a screen-detected cancer with annual screening was 2.32 per thousand screens and with biennial screening was 3.32 per thousand screens. The prognostic profile of screen-detected cancers was better than that of interval cancers. Among both screen-detected and interval cancers, the prognostic profiles with annual and biennial screening were similar. The estimated breast cancer-specific survival rates for women undergoing annual and biennial screening mammography were 95.2 and 94.6% at 5 years, and 90.4 and 89.2% at 10 years, respectively. Annual compared to biennial mammography was associated with a 1.2% increase in the estimated 10-year breast cancer-specific survival for women aged 50-74 years, diagnosed with invasive breast cancer after screening programme attendance.

The effect of deep inspiration breath-hold on tumour oxygenation.

AIM: To investigate the influence of deep inspiration breath-hold on the oxygen tension of in-vivo tumours measured using an Eppendorf pO2 histograph. MATERIALS AND METHODS: Patients with accessible primary or metastatic tumours > or = 2 cm diameter were entered into a protocol measuring tumour oxygenation with an Eppendorf pO2 histograph during normal breathing (NB) and deep inspiration breath-hold (DIBH). Change in oxygen tension was assessed using the Wilcoxon Signed Ranks test. RESULTS: Thirty patients were entered in to this protocol. The median maximum tumour dimension was 4 cm. The median of the median pO2 of these tumours was 18 mmHg. Tumours were assessed during NB and DIBH. Oxygen tension measurements along 1-3 pairs of tracks per tumour (median of 2) were obtained. The median number of measurements per track was 30 for NB and 29 for DIBH (range 17-59). In six tumours, the values during NB were significantly higher than during DIBH, whereas, for six other tumours, the relationship was the opposite; for the remaining 18 patients, no significant difference was observed. CONCLUSION: These data show heterogeneity of tumour oxygenation seen with in-situ tumours both at baseline and as a result of DIBH. No systematic change in the Eppendorf pO2 measurements was seen as a result of DIBH; however, the individual tumour responses to DIBH varied dramatically.

A randomised trial of cranberry versus apple juice in the management of urinary symptoms during external beam radiation therapy for prostate cancer.

AIMS: The aim of the study was to assess whether the oral intake of cranberry juice cocktail compared with apple juice was associated with a significant difference in urinary symptoms experienced during radical external beam radiation therapy (EBRT) for prostate carcinoma. MATERIALS AND METHODS: One hundred and twelve men with prostate cancer were randomised to either 354 ml cranberry juice or apple juice a day. Stratification was based on a history of a previous transurethral resection of prostate (TURP yes/no) and baseline International Prostate Symptom Score (IPSS < 6 or > or = 6) of urinary symptoms. RESULTS: The maximum IPSS (MRT) and the maximum change in IPSS from baseline (DRT) are used to report the results. We analysed the effects of juice allocation on DRT and MRT using analysis of covariates (ANCOVA). We observed no significant difference for DRT (P = 0.39) or MRT (P = 0.76) related to the consumption of cranberry compared with apple juice. However, we found a significant relationship between the history of a previous TURP and both DRT (P = 0.01) and MRT (P = 0.01). The history of a previous TURP was associated with lower values for both end points. Baseline IPSS was significant for DRT (P = 0.004) and MRT (P < or = 0.001). We found a significant relationship between the baseline IPSS < 6 or > or = 6 cut point on MRT (P < or = 0.001) but not on DRT (P = 0.43). The use of neoadjuvant hormones had no significant effect on DRT (P = 0.64) or MRT (P = 0.76). The use of additional symptomatic medication during the study was not significantly different between the two arms. CONCLUSIONS: This study shows no significant difference in the urinary symptoms experienced during EBRT related to the consumption of cranberry juice compared with apple juice.

Prognostic significance of the number of axillary lymph nodes removed in patients with node-negative breast cancer.

PURPOSE: The objective of the study was to evaluate the association between the number of lymph nodes removed at axillary dissection and recurrence and survival for patients with node-negative invasive breast cancer. PATIENTS AND METHODS: Subjects were 2,278 women with pathologically node-negative invasive breast cancer, diagnosed from 1989 to 1993 in British Columbia, Canada. Women aged > or = 90 years, with pure in-situ, bilateral invasive breast cancer or T4, N1, N2, or M1 stage, or who had axillary radiation were excluded. Two groups were defined for analysis: node-negative with no systemic therapy (n = 1,468) and node-negative with systemic therapy (n = 810). Median follow-up was 7.5 years. Prognostic variables assessed were age at diagnosis, tumor size, tumor grade, invasion of lymphatics, veins, or nerves, estrogen receptor status, and number of nodes removed. RESULTS: For patients not receiving systemic therapy, regional relapse was significantly increased with smaller numbers of nodes removed (P =.03). There was a trend toward shorter overall survival with fewer nodes removed (P =.06). Node-negative patients who received systemic therapy did not have a higher regional relapse rate or shorter overall survival when fewer nodes were recovered. CONCLUSION: Recovery of a small number of negative lymph nodes at axillary dissection likely understages patients and leads to undertreatment, resulting in an increased regional relapse rate and poorer survival. The use of systemic therapy may overcome this effect. The number of nodes removed, in conjunction with other prognostic factors, may be useful in selecting node-negative patients for systemic therapy.

Ten years of breast screening in the Screening Mammography Program of British Columbia, 1988-97.

OBJECTIVES: To evaluate 10 years outcomes of the Screening Mammography Program of British Columbia (SMPBC) and determine if breast screening targets were being achieved among women aged 40-80+ years. SETTING: Organised breast screening programme in British Columbia, Canada. METHODS: Rates of participation, abnormal referral, cancer detection, and interval cancer were calculated for asymptomatic women receiving an SMPBC mammography from 1988-97. RESULTS: 895,849 screening mammographies were provided to 335,433 women. 51.3% of women were age 50-69 years. Abnormalities were identified on 57,454 screens (6.4%) from which 3304 cancers were detected. Abnormal call rates were higher on first (9.8%), compared with subsequent screens (4.4%) and declined with age: 7.7% at age < 40 to 5.4% for age 70-79 years. Cancer detection rates were higher on first (5.0 per 1000) compared with subsequent screens (2.8 per 1000) and increased smoothly with age from 1.4 to 8.2 per 1000 from age < 40 to age 80 years and older. Twenty per cent of cancers were non-invasive. The median size of invasive cancers was 14 mm and 81% had no axillary lymph node metastases. The 12 month interval cancer rate was 0.6 per 1000 and did not vary significantly with age or screening history. The prevalence to expected incidence ratio was 3.1 for women age 50-79 years. CONCLUSION: Across a broad range of ages, surrogate indices of screening mammography success have been achieved in a population based, North American, organised breast cancer screening programme.

The human bone marrow response to acute air pollution caused by forest fires.

Atmospheric pollution increases cardiopulmonary morbidity and mortality by unexplained mechanisms. Phagocytosis of fine particles (PM(10)) by rabbit alveolar macrophages elevates white blood cells (WBC) by releasing precursors from the bone marrow and this could contribute to the pathogenesis of cardiopulmonary disease. The present study examined the association between acute air pollution caused by biomass burning and peripheral WBC counts in humans. Serial measurements of the WBC count made during the 1997 Southeast Asian Smoke-haze (Sep 29, Oct 27) were compared with a period after the haze cleared (Nov 21, Dec 5) using peripheral blood PMN band cells to monitor marrow release. The results showed that indices of atmospheric pollution were significantly associated with elevated band neutrophil counts expressed as a percentage of total polymorphonuclear leukocytes (PMN), with maximal association on zero and 1 lag day for PM(10) and 3, and 4 lag days for SO(2) (p value < 0.000). We conclude that atmospheric pollution caused by biomass burning is associated with elevated circulating band cell counts in humans because of the increased release of PMN precursors from the marrow. We speculate that this response contributes to the pathogenesis of the cardiorespiratory morbidity associated with acute air pollution.

Spiral computed tomography is comparable to angiography for the diagnosis of pulmonary embolism.

The use of spiral computed tomography (CT) for the diagnosis of pulmonary embolism has been compared to angiography, the current gold standard. However, the accuracy of pulmonary angiography has never been evaluated against an independent gold standard. The aim of this study was to compare contrast-enhanced spiral CT to pulmonary angiography for the detection of subsegmental-sized pulmonary emboli by using a methacrylate cast of porcine pulmonary vessels as an independent gold standard. We studied 16 anesthetized, juvenile pigs and injected colored methacrylate beads (3.8 mm, small; 4.2 mm, large) via the jugular vein. After embolization spiral CT (3 mm and 1 mm collimation), and pulmonary angiography were performed. Pigs were killed and the pulmonary arterial tree was cast using methacrylate. Spiral CT and angiography were interpreted independently by two radiologists. Sensitivity and 95% confidence intervals for 3 mm and 1 mm collimation CT and angiography, respectively, were: 82% (73 to 88%), 87% (79 to 93%), 87% (79 to 93%) (p = 0.42). Positive predictive values and 95% confidence intervals for 3 mm and 1 mm collimation CT and angiography, respectively, were: 94% (86 to 94%), 81% (73 to 88%), and 88% (80 to 93%). There was no difference between spiral CT and angiography for detection of subsegmental-sized pulmonary emboli. We conclude that spiral CT is comparable to angiography for detection of pulmonary emboli.

Carvedilol improves functional class in patients with severe left ventricular dysfunction referred for heart transplantation.

PURPOSE: Limited options are available to improve the functional class of patients awaiting cardiac transplantation. We assessed the effect of carvedilol on New York Heart Association (NYHA) class, heart rate (HR), blood pressure (BP), jugular venous pressure (JVP), electrolytes and renal function in patients with markedly decreased left ventricular (LV) function referred for cardiac transplantation assessment. METHODS: Sixty-one patients (age = 52 +/- 12 yr, EF = 23 +/- 7%, VO2 max = 16 +/- 5 mL/kg/min) referred to the cardiac transplant clinic were reviewed before and after the addition of carvedilol (starting dose 3.125 mg twice daily to target dose of 25 mg twice daily) to usual heart-failure therapy. Over a 1-yr period, at each visit prior to initiation, at baseline initiation visit and at each follow-up visit, NYHA class, BP, HR, JVP, electrolytes, and renal function were obtained. Statistical analysis was performed using random effects regression approach. A multiple logistic regression analysis was performed on 52/61 patients to determine possible associations between NYHA improvement and the following patient characteristics: sex, etiology of cardiomyopathy, initial NYHA class, and dose of carvedilol. RESULTS: Three patients died (2 after stopping carvedilol) and 3 were transplanted. Median follow-up was 100 d. Sixteen patients reached the target dose after a mean of 137 d (2.75 visits). Estimated time-to-target dose is 8 months (5.6 visits). BP tended to increase (p = 0.07 for change in trend) with no change in JVP, electrolytes or renal function. HR decreased 6 +/- 3 b.p.m. (p = 0.03). Of 14 patients NYHA class I/II at baseline, none were class III/IV at last follow-up visit. Of 47 patients NYHA class III/IV at baseline, 25 were class I/II, and 22 were class III/IV at last follow-up (p < 0.001). Multiple logistic regression analysis did not demonstrate any factor predictive of subsequent NYHA class improvement. CONCLUSIONS: Despite less than target doses in most patients, a favorable effect of carvedilol on functional class in patients with severe congestive heart failure (CHF) referred for transplant was observed. Those with good functional status remained stable and those with poor functional status improved or remained stable. No baseline patient characteristic predicted improvement. The shortage of donor organ requires optimal use of medical regimens which may improve functional class while awaiting transplantation and which may delay the necessity for heart transplantation. Therefore, addition of carvedilol to usual medical therapy may be beneficial even in patients with severe LV dysfunction and poor NYHA classification.

Effect of contrast media on coronary vascular resistance: contrast-induced coronary vasodilation.

STUDY OBJECTIVES: To determine if the vasodilatory response to the intracoronary injection of ionic and nonionic contrast media in intact pigs is dependent on nitric oxide (NO). The mechanisms responsible for inducing the increase in coronary blood flow in response to the intracoronary injection of contrast media during angiography are still not entirely understood. There is evidence to suggest that the response could be partially mediated by NO. PARTICIPANTS: We studied 14 anesthetized, open-chested pigs receiving ventilation. MEASUREMENTS AND RESULTS: Changes in coronary blood flow and coronary vascular resistance were measured in response to the coronary artery injection of saline solution (0.5 mol/L, isosmolar with plasma) and three different contrast agents: meglumine sodium ioxaglate (Hexabrix; Mallinckrodt Medical; Point-Claire, Quebec, Canada), a low osmolar ionic contrast agent; iohexol (Omnipaque 300; Sanofi Winthrop; Markham, Ontario, Canada), a nonionic contrast agent; and diatrizoate meglumine 66%, diatrizoate sodium 10% (MD-76; Mallinckrodt Medical), an ionic contrast agent. Measurements were made during three experimental conditions: the coronary artery infusion of (1) saline solution, control; (2) L-nitro-arginine (LNNA; 10(-3) mol/L and 10(-2) mol/L), a competitive inhibitor of NO synthase; and (3)L-arginine 10(-1) mol/L, a substrate for NO synthase. The infusion of LNNA produced an increase in baseline coronary vascular resistance (p < 0.001), but it did not attenuate the vasodilatory response to the infusion of the contrast agents. Both the high and low osmolar ionic and nonionic contrast media caused a decrease in baseline coronary vascular resistance. For all three conditions, MD-76, which has the highest osmolality, produced the greatest decrease in coronary vascular resistance. CONCLUSION: The vasodilatory response of the coronary vasculature to contrast agents is directly related to osmolality and is not mediated by NO.

Myopathy following mechanical ventilation for acute severe asthma: the role of muscle relaxants and corticosteroids.

BACKGROUND: Acute myopathy following mechanical ventilation for near-fatal asthma (NFA) has been described recently, and some researchers have suggested that this complication is related to the use of neuromuscular blocking agents (NMBAs) and corticosteroids (CSs). OBJECTIVES: To determine the incidence of acute myopathy in a group of patients and to examine the most important predictors of its development. DESIGN AND METHODS: A retrospective cohort study over a 10-year period (1985 to 1995) of all asthma patients who received mechanical ventilation at two centers in Vancouver (designated center 1 and center 2). RESULTS: In center 1, there were 58 patients who had 64 episodes of NFA, and in center 2, there were 28 patients who had 30 episodes. NMBAs were used in 30 of 86 admissions for acute severe asthma (35%). The mean (+/- SD) duration of muscle paralysis was 3.1+/-2.3 days. A total of 9 patients (10.4%) developed significant myopathy. The incidence of myopathy was 9 of 30 (30%) among patients who received NMBAs. In a multiple logistic regression model, the development of myopathy was only significantly associated with the duration of muscle relaxation. The odds ratio for the development of myopathy increased by 2.1 (95% confidence interval, 1.4 to 3.2) with each additional day of muscle relaxation. The dose and the type of the CS were not significantly associated with the myopathy in the multiple logistic regression analysis. CONCLUSION: Our study showed that there is a high incidence of acute myopathy when NMBAs are used for NFA. The incidence of myopathy increases with each additional day of muscle relaxation.

The use of milrinone in pre-transplant assessment of patients with congestive heart failure and pulmonary hypertension.

BACKGROUND: Pulmonary hypertension in patients with congestive heart failure (CHF) is a risk factor for increased mortality after orthotopic cardiac transplantation. Reversibility of elevated pulmonary vascular resistance (PVR) by pharmacologic agents predicts improved outcomes. Milrinone, a phosphodiesterase inhibitor with vasodilating and positive inotropic properties, has been shown to lower PVR in one previous study. However, no study has documented outcomes after cardiac transplantation in patients in whom reversibility of pulmonary hypertension was demonstrated after administration of milrinone. METHODS: We retrospectively reviewed 19 patients with CHF and pulmonary hypertension defined as PVR > or = 3 Wood units, PVRI (pulmonary vascular resistance index) > or = 4 resistance units, or TPG (transpulmonary gradient = mean pulmonary artery pressure--mean capillary wedge pressure) > or = 12 mmHg being assessed for cardiac transplantation. A sub-group of 14 patients with severe pulmonary hypertension defined as PVR > or = 4, PVRI > or = 6 and TPG > or = 15 was also examined. Milrinone was administered as a bolus (50 ug/kg) and hemodynamic parameters were measured at 5, 10 and 15 minutes. Six patients received cardiac transplants. RESULTS: Administration of milrinone significantly lowered PVR, PVRI, mean pulmonary artery pressure (PAM)(all p = 0.002) and pulmonary capillary wedge pressure (PCWP)(p = 0.006). Cardiac output (CO) increased significantly (p = 0.001). TPG did not change (p = 0.33). In patients with severe pulmonary hypertension, the magnitude of these changes was greater. In addition, TPG was significantly lowered (p = 0.02). CONCLUSION: Milrinone lowered PVR by decreasing PAM and increasing CO significantly. In addition, PCWP was significantly lowered. These finding confirm both vasodilatory and inotropic effects of milrinone. Patients with severe pulmonary hypertension had more pronounced effects. There were no deaths in the group of patients proceeding to cardiac transplantation. Our study demonstrates the efficacy of milrinone in lowering PVR as well as suggesting safety in use in patients undergoing cardiac transplantation.

Nitric oxide reduces the sequestration of polymorphonuclear leukocytes in lung by changing deformability and CD18 expression.

Nitric oxide (NO) influences polymorphonuclear leukocytes (PMN)-endothelial cell interactions. The aim of this study was to evaluate this effect in the lung and investigate this mechanism. PMN sequestration in the lung was evaluated in vivo after the infusion of complement fragments. Rabbits (n = 9) that inhaled 40 ppm of NO were compared with control rabbits (n = 9) over a 2-h period following infusion of complement fragments. Circulating PMN counts immediately decreased after infusion of complement fragments in both groups followed by a recovery to baseline. This recovery was maintained in the NO-treated group compared with the control rabbits (p < 0.05). NO reduced PMN sequestration in the lung measured by both arteriovenous PMN difference across the lung (p < 0.01) and the myeloperoxidase (MPO) content of the lung tissue (p < 0.01). NO had no effect on the complement fragments-induced PMN release from the bone marrow. In vitro studies showed that NO partially inhibited F-actin assembly (p < 0.01) reduced the change in deformability (p < 0.05) and inhibited CD18 upregulation (p < 0.05) but had no effect on the L-selectin shedding of PMN stimulated by complement fragments. We conclude that NO reduces the sequestration of activated PMN by reducing deformability change via inhibition of F-actin assembly and inhibiting the upregulation of CD18.

A quantification of the lung surface area in emphysema using computed tomography.

Quantitative analysis of computed tomography (CT) has been combined with a stereologically based histologic analysis of lung structure to assess regional lung inflation and the structural features of the lung parenchyma. In this study, CT measurements of lung inflation were compared with histologic estimates of surface area in order to develop prediction equations that allow lung surface to volume ratio and surface area to be predicted from an analysis of the CT scan. The results show that mild emphysema is associated with an increase in lung volume and a reduction in surface to volume ratio, whereas surface area and tissue weight were only decreased in severe disease. The CT predicted surface to volume ratio correlated with histology, and both predicted and measured surface areas correlated with the diffusing capacity. We conclude that this CT analysis can be used to monitor the progression of emphysematous lung destruction in individual patients, and to assess the impact of both surgical and medical treatments for emphysema.

Mechanisms, management, and outcome of failure of delivery of coronary stents.

In a single-center experience, initial failure of attempted stent delivery was relatively infrequent (2.7%) but was associated with increased need for urgent coronary bypass surgery. Delivery failure was more likely with coiled stents and dislodgment from the delivery balloon was more likely with hand-mounted or radiolucent stents.

Mechanical properties of lung parenchyma during bronchoconstriction.

Interdependence between airways and the lung parenchyma is thought to be a major mechanism preventing excessive airway narrowing during bronchoconstriction. Because the elastance of the lung increases during bronchoconstriction, the lung's tethering force could also increase, further attenuating bronchoconstriction. We hypothesized that the bulk (kappa) and shear moduli (mu) of the lung increase similarly during bronchoconstriction. To test this hypothesis, we excised rabbit lungs and measured the lung volume, pulmonary elastance, kappa, and mu at transpulmonary pressures of 4, 6, 8, 12, and 16 cmH2O using pressure-volume curves, slow oscillations of the lung, and an indentation test. Bronchoconstriction was induced by nebulizing carbachol by using small tidal-volume ventilation to prevent hyperinflation. The measurement of kappa and mu was repeated after carbachol treatment. After carbachol treatment, the increase in kappa was significantly greater than that in mu. The estimated value for mu was approximately 0.5 x transpulmonary pressure both before and after carbachol treatment. These data suggest that the tethering effect of the lung parenchyma, which serves to attenuate bronchoconstriction, is not significantly increased during carbachol administration unless there is hyperinflation.

Glucocorticoid-induced granulocytosis: contribution of marrow release and demargination of intravascular granulocytes.

BACKGROUND: Glucocorticoid-induced granulocytosis has been attributed to enhanced release of polymorphonuclear leukocytes (PMNs) from bone marrow, delayed apoptosis, and reduced egress of PMNs into tissues. This study was designed to determine the relative contributions of PMNs released from the bone marrow and those entering the circulation from the marginated pool to the granulocytosis produced by a single dose of dexamethasone (2.0 mg/kg) in rabbits. METHODS AND RESULTS: PMN transit through the mitotic and postmitotic pools of the bone marrow and rate of release of PMNs into the circulation were measured by use of the thymidine analogue 5'-bromo-2'-deoxyuridine (BrdU) to pulse-label PMNs in the bone marrow. The shift of PMNs from the marginated to the circulating pool was measured with BrdU-labeled PMNs transferred from donor rabbits to recipients before dexamethasone was delivered. The data show that dexamethasone increased bone marrow release of PMNs and shortened their transit time through the postmitotic pool (P<0.001) but not the mitotic pool of the bone marrow (P>0.05). Dexamethasone slowed the clearance of BrdU-labeled PMNs from the circulation (P<0.05) and lengthened their disappearance (half-life) from the circulation compared with control (half-life, 4.95 versus 9. 45 hours). At 6 hours after dexamethasone, bone marrow release contributed approximately 10%, mobilization from the marginated pool approximately 61%, and a lengthened half-life in the circulation approximately 29% to the glucocorticoid-induced granulocytosis. CONCLUSIONS: We conclude that a single dose of dexamethasone causes a granulocytosis primarily by a shift of PMNs from the marginated to the circulating pool, with a minor contribution from marrow release.

Mechanism of methacholine dose-response plateaus in normal subjects.

Normal subjects develop plateaus on dose-response curves produced from inhalation challenge tests with bronchoconstricting agonists. These plateaus occur after only mild degrees of airway narrowing despite the fact that, if unloaded, maximally activated airway smooth muscle (ASM) should be able to cause airway closure. Plateaus may develop because, despite maximal activation, the muscle load provided by lung parenchymal recoil and tidal swings in airway transmural pressure are sufficient to prevent further ASM shortening. Alternatively, progressive ASM activation may occur throughout the plateau, but progressive hyperinflation and/or parenchymal stiffening could increase parenchymal load and attenuate further airway narrowing. In the first case, maximal ASM activation causes the plateau and in the second case the plateau is caused by progressive activation balanced by progressive loading. To test which of these mechanisms is responsible for the plateau, we measured pulmonary resistance (RL) and the maximal, minimal, and mean pulmonary elastic recoil pressure (PELmax, PELmin, and PELmean) during tidal breathing throughout methacholine challenge in 10 normal subjects. PELmean served as our measure of ASM afterload. Subjects swallowed an esophageal balloon and inhaled doubling concentrations of methacholine (1 to 256 mg/ml). RL was measured after each dose, as was PEL. All subjects developed a plateau on the dose-response curve defined by < 25% change in RL over three successive doses. During the RL plateau, there was no significant further increase in PELmean, i.e., PELmean also plateaued. These data are consistent with the hypothesis that maximal activation of ASM is balanced by an equal afterload at the maximal dose-response plateau. Airway hyperresponsiveness could result from a failure of afterload to attenuate muscle shortening after maximal activation.

Longitudinal analyses for magnetic resonance imaging outcomes in multiple sclerosis clinical trials.

A basic feature of many clinical trials is the collection of longitudinal data on individual patients. Analysis of such data is often based on summaries over time. This allows use of standards methods to assess treatment effects but sacrifices information on patterns over time as well as potential greater efficiency of analysis. The purpose of this paper is to illustrate the utility of the generalized estimating equations (GEE) approach to the analysis of longitudinal binary, count, and continuous responses for the frequent magnetic resonance imaging (MRI) substudy of the 3-year pivotal trial of interferon beta-1 b in relapsing-remitting multiple sclerosis.