The Effect of Body Mass Index on Presentation of COVID-19 amongst Heart Transplant Recipients: A Multi-Institutional Study

Purpose

Characteristics and outcomes of heart transplant (HT) recipients who contract coronavirus (SARS-CoV-2) have been poorly described. The current study was undertaken to better understand the risk obesity may pose in this patient population

Methods

A prospectively-maintained Trans-CoV-VAD Registry containing HT recipients at 11 participating institutions who presented with SARS-CoV-2 were reviewed. Presenting characteristics, hospitalization rates, ventilator & intensive care unit usage, and mortality were queried. Patients were grouped by body mass index (BMI) into obese (BMI≥30 k/m²) and non-obese cohorts (BMI<30 kg/m²). Comparisons between groups were made utilizing chi-squared, Fisher's exact, and Mann-Whitney U-tests. Multivariable logistic regression models were utilized

Results

Across all centers, 85 HT recipients who tested positive for SARS-CoV-2 were identified, of whom 26 (31%) were obese. Median time from HT to diagnosis was 4.6 (1.8-13.8) years. No differences in age (57 vs 60 p 0.85) or female gender (31% vs 24% p 0.5) were noted between obese and non-obese patients. On presentation, obese patients were more symptomatic with higher rates of cough (76% vs 48% p 0.02), dyspnea (62% vs 41% p 0.09), diarrhea (60% vs 35% p 0.03), and headache (35% vs 14% p 0.03). No differences in rates of admission (62% vs 64% p 0.8), ICU presentation (44% vs 35% p 0.6) or need for mechanical ventilation were noted (38% vs 22% p 0.2). More secondary infections were noted amongst obese patients (32% vs 13% p 0.04). On follow-up, mortality was similar between groups (12% vs 9% p 0.7). On multivariable modeling, BMI was not associated with increased adjusted odds of hospital/ICU admission or mechanical ventilation (p>0.10)

Conclusion

Acute presentations of SARS-CoV-2 amongst HT recipients carry significantly higher mortality over the general population. Obesity appears to impact presenting symptoms and secondary infections, but does not strongly impact ICU requirements or mortality

Predicting progressive hepatic fibrosis stage on subsequent liver biopsy in chronic hepatitis C virus infection

Retrospective cross-sectional studies indicate that 20% with chronic hepatitis C virus (HCV) infection become cirrhotic within 20 years. Known risk factors for advanced hepatic fibrosis include age at time of infection, male sex, excess alcohol consumption and cytokine polymorphisms. Prospective study to assess and identify factors predictive of change in hepatic fibrosis stage in chronic HCV infection by interval protocol liver biopsy was performed. One hundred and five patients with paired liver biopsy specimens separated by a mean 41 months were recruited from a cohort of 823 HCV carriers. Five per cent developed worsening hepatic fibrosis by more than two stages. In 43% there was no change in fibrosis stage. Excessive alcohol intake currently (P = 0.037) or previously (P = 0.07) predicted progression. In contrast, always having a normal alanine transaminase (P = 0.038) and always being negative in serum for HCV RNA (P =0.067) predicted no progression. Three models were developed to predict outcome. Progressive fibrosis was predicted by baseline fibrosis (P = 0.018), steatosis (P = 0.02) and age (P = 0.017). The rate of progressive fibrosis was predicted by baseline fibrosis (P = 0.0002), steatosis (P =0.039) and lobular inflammation (P = 0.09). Fibrosis stage on the second biopsy was predicted by baseline fibrosis alone (P = 0.01). The rate of progression varies widely. Alcohol misuse is an important co-factor. Progressive fibrosis can be predicted at first liver biopsy, where baseline fibrosis is most critical, allowing targeted therapy for those with early disease and a significant risk of progression.

Review article: chemotherapy for pancreatic cancer

Pancreatic cancer is a common, highly lethal disease that is rising in incidence. Chemotherapy based on 5-fluorouracil (5-FU) has been shown to prolong survival in advanced pancreatic cancer. Gemcitabine improves major symptoms and survival outcomes compared with bolus 5-FU. Many novel small molecules are being widely and actively researched. These compounds are based on classical mechanisms of action as well as biological therapies targeting novel cellular survival pathways, and include fluoropyrimidines, nucleoside cytidine analogues, platinum analogues, topoisomerase-inhibitors, antimicrotubule agents, proteasome inhibitors, vitamin D analogues, arachidonic acid pathway inhibitors, histone deacytylator inhibitors, farnesyltransferase inhibitors and epidermal growth factor receptor therapies. Adjuvant chemotherapy has also demonstrated the best survival outcomes following resection compared to other adjuvant or neo-adjuvant strategies such as radiation-based treatments. These benefits are superimposed on the dramatic increase in resectability rates and reduction in post-operative mortality achieved by centralisation of treatment in high-volume speciality centres. Newer 'small-molecule' drugs as well as the latest 'large-molecule' biological agents hold considerable promise for the future. Real advances are anticipated over the next five years but are dependent on large randomised controlled trials for success.

Stress in UK intensive care unit doctors

BACKGROUND

Doctors have long been considered at risk of occupational stress.

METHODS

A postal survey of all members of the Intensive Care Society using validated instruments.

RESULTS

Eight-five per cent of members returned questionnaires and 70% were eligible for the study. Twenty-nine per cent were suffering General Health Questionnaire-12 (GHQ-12) identified distress and 12% Symptom Checklist-Depression (SCL-D) defined depression. There were no significant age or sex differences between staff suffering distress or depression and those who did not. Dissatisfaction with career correlated highly with both distress and depression (P<0.01). Twenty doctors (3%) were bothered by suicidal thoughts. The most stressful aspects of work were bed allocation, being over-stretched, effect of hours of work and stress on personal/family life, and compromising standards when resources are short. Logistic regression revealed mental health problems were predicted by five stressors: 'lack of recognition of one's own contribution by others'; 'too much responsibility at times'; 'effect of stress on personal/family life'; 'keeping up to date with knowledge'; and 'making the right decision alone'.

CONCLUSIONS

Nearly one in three ICU doctors appeared distressed (GHQ), and one in 10 depressed (SCL-D); this is no greater than that reported in other specialities. Perceived stressors reveal some key areas of concern for the employer and the specialty.

Neonatal bone mass: influence of parental birthweight, maternal smoking, body composition, and activity during pregnancy

Evidence is accumulating that intrauterine growth and development may influence an individual's risk of osteoporosis in later adult life. To examine maternal and paternal influences on intrauterine skeletal growth, we used dual-energy X-ray absorptiometry to measure the neonatal bone mineral content (BMC) and bone mineral density (BMD) of 145 infants born at term. Independently of the infant's duration of gestation at birth, the birthweights of both parents and the height of the father were positively correlated with neonatal whole body BMC. Women who smoked during pregnancy had infants with a lower whole body BMC and BMD; overall, there was a 7.1-g (11%) average difference between whole body BMC of infants whose mothers did and did not smoke during pregnancy (p = 0.005). Women with thinner triceps skinfold thicknesses (reflecting lower fat stores) and those who reported a faster walking pace and more frequent vigorous activity in late pregnancy also tended to have infants with a lower BMC and BMD (p values for BMC; 0.02, 0.03, and 0.05, respectively). Maternal thinness and faster walking pace but not maternal smoking or parental birthweight also were associated with lower bone mineral apparent density (BMAD). The influences on skeletal growth and mineralization were independent of placental weight, a marker of the placental capacity to deliver nutrients to the fetus. These observations point to a combination of genetic and intrauterine environmental influences on prenatal skeletal development and suggest that environmental modulation, even at this early stage of life, may reduce the risk of osteoporosis in adulthood.

Further evidence for an association between non-insulin-dependent diabetes mellitus and chronic hepatitis C virus infection

Non-insulin-dependent diabetes mellitus (NIDDM) may be associated with chronic hepatitis C virus (HCV) infection. This was studied further in two parts. First, 1,151 patients with HCV-related cirrhosis and 181 patients with hepatitis B virus (HBV)-related cirrhosis, well matched for age, sex, and severity of cirrhosis, were reviewed retrospectively. The prevalence of diabetes mellitus was higher in HCV-related cirrhosis (23.6%) than in HBV-related cirrhosis (9.4%; odds ratio [OR], 2.78; 95% confidence interval [CI], 1.6-4.79; P =.0002). The prevalence of diabetes mellitus was associated closely with the Child-Pugh score (OR, 3.83; 95% CI, 2. 38-6.17; P <.0001) and increasing age (OR, 1.02; 95% CI, 1.00-1.03; P =.0117). Second, 235 patients with biopsy confirmed chronic HBV or HCV underwent an oral glucose tolerance test. Only 1 of 70 patients with chronic viral hepatitis without cirrhosis was diabetic. However, 31 of 127 patients with HCV-related cirrhosis (24.4%) were diabetic compared with 3 of 38 patients with HBV-related cirrhosis (7.9%, P =.0477). The major variables associated with NIDDM were cirrhosis (OR, 14.39; 95% CI, 1.91-108; P =.0096) and male sex (OR, 4.64; 95% CI, 1. 32-16.18; P =.0161). Fasting insulin levels in 30 patients with HCV-related cirrhosis and diabetes mellitus were elevated significantly, which was consistent with insulin resistance. However, acute insulin responsiveness was reduced in all patients with HCV infection and diabetes suggesting concomitant B-cell dysfunction. This study confirms an association between HCV and NIDDM.

Immune responses to exercise in children treated for cancer

BACKGROUND

Children treated for cancer commonly benefit physiologically from moderate aerobic training, but it is less clear if impairment of the immune system secondary to chemotherapy reduces the immunological tolerance of exercise relative to normal children.

METHODS

EXPERIMENTAL DESIGN

a case series.

SETTING

hospital laboratory.

PARTICIPANTS

six children aged 13-14 yr, successfully treated for acute lymphoblastic leukaemia and other types of neoplasms, were compared with 11 normal volunteer children.

INTERVENTIONS

three of the sample underwent 12 weeks training at 70-85% of maximal heart rate; the remaining three provided initial and final test data only.

MEASURES

mood state (Piers-Harris test), anthropometric data, maximal oxygen intake, response to 30 min exercise challenges at anaerobic threshold, and standard immune measures (differential count, cytolytic activity, and mitogen-induced lymphocyte proliferation) at rest, during and following submaximal exercise.

RESULTS

A low maximal oxygen intake, excess of body fat, and high anxiety scores all improved with training. Children who were still receiving chemotherapy showed low resting CD3+, CD4+, CD8+, CD19+ and CD25+ counts and reduced PHA-induced proliferation. Acute exercise and training caused further impairment of immune responses, although changes remained insufficient to cause concern for health.

CONCLUSIONS

Exercise therapy is beneficial following treatment of cancer, but should be prescribed individually, with a careful monitoring of immune responses.

Immune responses to training: how critical is training volume?

BACKGROUND

If the volume of training undertaken is sufficient to induce a negative energy balance, the anticipated benefit of an enhanced immune response may be reduced or lost.

METHODS

33 sedentary but healthy male volunteers aged 19-29 years, recruited from the university community. A peak oxygen intake measurement (cycle ergometer) and a 60-min exercise challenge at 60% of aerobic power were performed before and after 12 wk of treatment. Total leukocytes, subsets, CD3+, CD4+, CD8+, CD16+, CD19+, and CD25+ counts (FACScan), cytolytic activity (51Cr release) and cell proliferation (PHA and PWM) were measured, with subjects assigned arbitrarily to one of three groups: light training (18 subjects, aerobic exercise at 70-85% HRmax 3 times/wk), moderate training (9 subjects, similar programme 4-5 times/wk) and control (6 subjects).

RESULTS

Groups were initially well-matched in physical and physiological terms. Training increased aerobic power (8%, light, 21% moderate training), with a loss of body mass and fat in the moderate training group. Controls showed no changes. Resting CD16+ counts increased by 27% (light training) and CD16+ CD56+ counts by 21% (moderate training), with less post-exercise suppression of counts than at recruitment. Light training also decreased CD3+ and CD4+ counts without changing the CD4+/CD8+ ratio. Moderate training decreased resting CD19+ count.

CONCLUSIONS

From the viewpoint of immune function, the optimal training regimen is of low volume. Moderate training sufficient to induce a negative energy balance yields a smaller increase in numbers of non-MHC-restricted cytotoxic cells, and carries the negative consequence of diminished B cell counts.

The school health fair: an elementary choice

School is a place where children work, play and learn. It is also a place where they can first develop an awareness of quality of life and its health components. With the current emphasis on health as a resource for living, emphasizing social and personal resources as well as physical capacity, the school community offers an important opportunity for the development of life skills to help children make informed health decisions.

Arrest of endotoxin-induced hypotension by transforming growth factor beta1

Septic shock is a cytokine-mediated process typically caused by a severe underlying infection. Toxins generated by the infecting organism trigger a cascade of events leading to hypotension, to multiple organ system failure, and frequently to death. Beyond supportive care, no effective therapy is available for the treatment of septic shock. Nitric oxide (NO) is a potent vasodilator generated late in the sepsis pathway leading to hypotension; therefore, NO represents a potential target for therapy. We have previously demonstrated that transforming growth factor (TGF) beta1 inhibits inducible NO synthase (iNOS) mRNA and NO production in vascular smooth muscle cells after its induction by cytokines critical in the sepsis cascade. Thus, we hypothesized that TGF-beta1 may inhibit iNOS gene expression in vivo and be beneficial in the treatment of septic shock. In a conscious rat model of septic shock produced by Salmonella typhosa lipopolysaccharide (LPS), TGF-beta1 markedly reduced iNOS mRNA and protein levels in several organs. In contrast, TGF-beta1 did not decrease endothelium-derived constitutive NOS mRNA in organs of rats receiving LPS. We also performed studies in anesthetized rats to evaluate the effect of TGF-beta1 on the hemodynamic compromise of septic shock; after an initial 25% decrease in mean arterial pressure, TGF-beta1 arrested LPS-induced hypotension and decreased mortality. A decrease in iNOS mRNA and protein levels in vascular smooth muscle cells was demonstrated by in situ hybridization and NADPH diaphorase staining in rats treated with TGF-beta1. Thus these studies suggest that TGF-beta1 inhibits iNOS in vivo and that TGF-beta1 may be of future benefit in the therapy of septic shock.

The hypothalamic-pituitary-adrenal axis in obesity

The hypothalamic-pituitary-adrenal (HPA) axis normally maintains the concentration of cortisol within a narrow range with a diurnal variation characterized by higher cortisol concentrations in the morning and reduced levels in the evening. Excessive or deficient secretion of cortisol is associated with pathologic changes. Obesity has been linked with age, sex and racial alterations in the functioning of the HPA axis which are reviewed. The possible relationship of altered HPA axis activity with the long-term complications of obesity are considered.

Increased airway responsiveness to inhaled methacholine in a rat model of chronic bronchitis

Chronic exposure of rats to high concentrations of SO2 gas causes pathologic changes in airway similar to those seen in human chronic bronchitis. The purpose of this study was to examine the pulmonary mechanical correlates of these changes and to quantify the extent of mucous hypersecretion by measuring changes in mucous glycoproteins. Female Sprague-Dawley rats were exposed to 250 ppm SO2 gas, 5 h/d, 5 d/wk, for a period of 4 wk. Control rats were exposed to air only. On the day after the last SO2 exposure, rats were anesthetized, instrumented for the measurement of pulmonary resistance (RL) and dynamic compliance (Cdyn), and ventilated. Chronic SO2 exposure caused a small but significant increase in RL and decrease in Cdyn. Airway responsiveness to inhaled aerosolized methacholine was increased in SO2-exposed rats, as indicated by approximately 6.6- and 4.6-fold decreases respectively, in the doses of inhaled methacholine required to double RL or decrease Cdyn to 50% of baseline. SO2 exposure had no effect on the contractile response of the trachea measured in vitro. Tracheae and lungs from SO2-exposed animals exhibited 140 and 535% increases in measured neutral mucous glycoproteins, respectively, and 33 and 37% increases in acid glycoproteins. Our results indicate that this animal model of chronic bronchitis mimics the mucous hypersecretion, airway obstruction, and increased airway responsiveness observed in human bronchitis and may allow us to begin to probe their mechanistic basis.

Acute exercise and immune function. Relationship between lymphocyte activity and changes in subset counts

Twenty-one young male subjects exercised on a cycle ergometer for 60 min at 60% of VO2max. Blood samples collected every 30 min throughout exercise and continuing to 120 min recovery served for the immunological tests. Exercise induced biphasic changes in the various leucocyte subsets. There was a granulocytosis, lymphocytosis and monocytosis during exercise, and a further granulocytosis and a slight monocytosis, but a lymphocytopenia during recovery. All lymphocyte subsets (CD3+, CD19+, CD4+, CD8+, and CD16+ cells) increased in number during exercise, were decreased 30 min after exercise, and had not returned to baseline levels by 120 min of recovery. The apparent lymphocyte responsiveness to the mitogens phytohaemagglutinin (PHA) and pokeweed mitogen (PWM) declined significantly during exercise, returning to normal by 120 min of recovery. The natural killer (NK) activity rose markedly during exercise, but decreased to almost half the pre-exercise level at 30 and 60 min of recovery, returning to baseline levels after 120 min of recovery. Functional capability correlated well with the percentage of each major responder subset in the assay, suggesting that the in vitro lymphocyte PHA- and PWM-responsiveness and the NK activity did not change significantly on a per cell basis. The analysis of lymphocyte marker antigen density revealed that the CD3+, CD4+, CD8+ and CD19+ lymphocytes mobilized into the circulation during exercise did not express the respective CD3, CD4, CD8 and CD19 molecules as strongly as did the subsets circulating at rest, whereas the expression of the CD16 antigen on CD16+ lymphocytes remained unchanged.

An unusual genotype in an Ashkenazi Jewish patient with Tay-Sachs disease

The Ashkenazi Jewish population is enriched for carriers of a fatal form of Tay-Sachs disease, a recessive inherited disorder caused by mutations in the alpha-chain of the lysosomal enzyme beta-hexosaminidase A. Approximately 20% of the Ashkenazi carriers harbor a splice junction defect while about 78% bear a 4 base pair (bp) insertion. However, the Ashkenazi Jewish patient used in the original description of the 4 bp insertion carried this lesion in only 1 allele and was negative for the splice junction mutation. We cloned the insertion negative allele and by sequence analysis of the exons found a point mutation in exon 11 that results in substitution of Trp392 with a premature termination codon. Nine Ashkenazi Jewish carriers that tested negative for the major and minor mutations as well as for a lesion causing an adult form of Tay-Sachs disease did not carry the base change defect, suggesting that it may be a recent and/or rare mutation. This finding also indicates that screening the Ashkenazi population solely by recombinant DNA methods for the splice junction, 4 bp insertion, and adult mutations may result in occasional false negatives.

Airway luminal liquid. Sources and role as an amplifier of bronchoconstriction

The release of mediators from inflammatory cells into the airway lumen can initiate a series of events leading to airway obstruction, particularly smooth muscle contraction and alteration of endothelial and epithelial permeability leading to mucosal edema and subsequent influx of liquid into the airway lumen. In this report we briefly review the effects of several inflammatory mediators, including eicosanoids, platelet-activating factor, and histamine, as well as the effects of plasma proteins and tachykinins that may be secondarily released because of the presence of inflammatory mediators on endothelial and epithelial permeability. We then consider physical mechanisms whereby the resulting airway luminal liquid could amplify the response of an airway previously constricted because of smooth muscle contraction. Specifically, liquid in the interstices between epithelial projections that are formed during muscular contraction could amplify the degree of luminal compromise by (1) further decreasing luminal cross-sectional area by occupying space, and (2) providing an additional source of inward recoil because of the surface tension of the air-liquid interface.

Polymerase chain reaction-generated heteroduplexes from Ashkenazi Tay-Sachs carriers with an insertion mutation can be detected on agarose gels

Images

A gel electrophoretic assay for detecting the insertion defect in Ashkenazi Jewish carriers of Tay-Sachs disease

A simple, rapid, nonradioactive assay for detecting the 4-bp insertion defect found in the beta-hexosaminidase alpha-chain gene of 70% of the Ashkenazi Jewish carriers of Tay-Sachs disease is described. In this assay, DNA derived from such carriers serves as a template for the polymerase chain reaction. Following amplification of a 159-bp fragment of exon 11 inclusive of the insertion, a portion of the product is subjected to electrophoresis in a 4% NuSieve agarose minigel. Visualization of the DNA with ethidium bromide demonstrates that heterozygote carriers for the defect display two distinct bands. In contrast, DNA from carriers of the splice junction defect, a mutation found in 30% of the Ashkenazi Jewish carriers of Tay-Sachs disease, displays only one band.

Effect of endogenous prostaglandins on acetylcholine release from dog trachealis muscle

We used a radioenzymatic technique to measure effects of the prostaglandin synthesis inhibitor indomethacin and of exogenous prostaglandin E2 (PGE2) and prostaglandin I2 (PGI2) on acetylcholine (ACh) efflux from canine tracheal smooth muscle (TSM) during sustained electrical field stimulation (EFS; 2 Hz, 2 ms pulse duration, 50 V for 15 min). ACh efflux from indomethacin (INDO, 10(-6) M)-pretreated and control TSM increased with consecutive stimulations. However, efflux of ACh was greater in INDO-treated than control muscles. INDO increased the tension produced by TSM in response to EFS. Neither PGE2 (10(-8) M) nor PGI2 (10(-6) M) had any effect on ACh efflux from INDO-pretreated TSM during the first of three periods of EFS. However, PGI2 and PGE2 prevented the progressive increase in ACh efflux observed on subsequent stimulations. PGE2 but not PGI2 decreased contractions of TSM caused by EFS. Our results demonstrate that endogenous prostaglandins, probably PGE2, do inhibit EFS-evoked ACh release from canine TSM in vitro, but suggest that these prostaglandins modulate EFS-evoked contractions predominantly by postsynaptic mechanisms.

NMR Studies of Simple Molecules on Metal Surfaces

In recent years, improvements in the sensitivity of nuclear magnetic resonance have made it possible to detect progressively smaller numbers of nuclei. Experiments and studies previously thought to be impractical can now be undertaken, for example, the study of phenomena at surfaces. Nuclear magnetic resonance has been applied to study simple molecules (carbon monoxide, acetylene, and ethylene) adsorbed on metal surfaces (ruthenium, rhodium, palladium, osmium, iridium, and platinum). The metals, in the form of clusters 10 to 50 angstroms in diameter, supported on alumina, are typical of real catalysts. The experiments provide information about the bonding of the molecules to the metal, the structures the molecules assume after adsorption, the motion of molecules on the surface, the breakup of molecules induced by heating, and the products of such breakup.

Tachyphylaxis to inhaled aerosolized histamine in anesthetized dogs

Three consecutive dose-response curves to inhaled aerosolized histamine, separated by 1-h intervals, were obtained in 20 anesthetized mongrel dogs. In general, successive histamine dose-response curves shifted progressively rightward. Changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in response to low concentrations of histamine were reproducible, but responses to high concentrations (sufficient to at least double RL or decrease Cdyn by at least 30%) decreased on successive dose-response curves. The concentration of histamine required to double RL increased significantly (P less than 0.05) from 1.01 mg/ml on the first to 1.62 and 2.02 mg/ml on the second and third dose-response curves. In contrast, consecutive methacholine dose-response curves were not significantly different. Indomethacin pretreatment (5 mg/kg iv) prevented histamine tachyphylaxis, whereas atropine (4 mg iv) did not. However, indomethacin did not alter base-line pulmonary mechanics or histamine responsiveness as measured on the first dose-response curve. We conclude that tachyphylaxis to inhaled aerosolized histamine occurs in anesthetized dogs. Our results are consistent with an important role for endogenous prostaglandins in modulating the airway responses to repeated histamine exposures.

Mechanisms of histamine-induced contraction of canine airway smooth muscle

We studied the effects of atropine (10(-10) to 10(-6) M), tetrodotoxin (TTX) (10(-6) g/ml), and neostigmine (10(-7) M) on the histamine dose-response curve of canine tracheal smooth muscle (TSM) in vitro. Pretreatment with atropine or TTX reduced base-line tension in some TSM samples, whereas neostigmine invariably caused contraction of TSM. All concentrations of atropine reduced the maximum isometric tension produced by histamine (Tmax). With 10(-6), 10(-8), and 10(-10) M atropine, Tmax was 57, 74, and 88%, respectively, of its value in paired control samples. Atropine, 10(-9) to 10(-6) M, increased the concentration of histamine which produced 20% of Tmax, whereas 10(-6) M also increased the concentration required to produce 50% of Tmax. TTX reduced tension produced by low concentrations of histamine but had no effect at higher concentrations. Neostigmine shifted the histamine dose-response curve and caused greater tension for any given histamine concentration; Tmax increased by 30% (P less than 0.05). Our data are consistent with spontaneous release of acetylcholine from cholinergic nerves in the airway tissue and suggest that histamine either accelerates this release or interacts supra-additively with the acetylcholine at the smooth muscle.

Effect of continuous positive airway pressure on respiratory mechanics and pattern of breathing in induced asthma

We studied the effects of continuous positive airway pressure (CPAP) in 8 asthmatic subjects in whom bronchospasm was induced by aerosolized histamine. The CPAP (12.0 +/- 0.9 cm H2O) increased functional residual capacity by only 0.27 +/- 0.12 L, raised the minimal pleural pressure (Ppl) during inspiration from -32.3 +/- 2.6 cm H2O to -22.8 +/- 2.3 cm H2O (p less than 0.01), and decreased the swings in transdiaphragmatic pressure (Pdi) from 35.1 +/- 2.4 cm H2O to 29.6 +/- 3.7 cm H2O (p less than 0.05). Although ventilation (VE) increased, the inspiratory work per liter of VE fell significantly. More importantly, the pressure-time product for the inspiratory muscles (integral of Ppl.dl) measured over 60 s, fell from 830 +/- 111 to 573 +/- 41 cm H2O.s (p less than 0.05), whereas that for the diaphragm (integral of Pdi.dt) fell from 690 +/- 91 to 497 +/- 74 cm H2O.s (p less than 0.05). We conclude that in induced asthma, CPAP reduces the load on the inspiratory muscles, improving their efficiency and decreasing the energy cost of their action. Our results justify further investigation into the role of CPAP in the treatment of respiratory failure caused by severe bronchial asthma.

Reassessment of body plethysmographic technique for the measurement of thoracic gas volume in asthmatics

We measured thoracic gas volume (Vtg) by the body plethysmographic technique in 4 normal subjects and in 9 asthmatics during remission and after bronchoconstriction induced with inhaled aerosolized histamine. Changes in both mouth (Pm) and esophageal pressure (Pes) were used to approximate changes in alveolar pressure (Palv), and both Vtg(m) and Vtg)(es) were computed. Because small changes in lung recoil occur during panting, delta Pes exceeds delta Pm, leading to a value of Vtg(m) that is slightly greater than Vtg(es). Indeed, in the normal subjects, Vtg(m) was significantly greater than Vtg(es), and the observed percentage error (E) between them (2.8%) corresponded with the expected value. In the asthmatics, during marked bronchoconstriction, there was an increased tendency for Vtg(m) to exceed Vtg(es), E averaging 12.2% and being greater than the predicted error. In some asthmatics, changes in volume led changes in Pm; the phase angle between volume and Pm averaged 6.3 degrees and was significantly greater than that between volume and Pes (1.7 degrees). In 3 asthmatics, increases in TLC(m) were not accompanied by similar changes in TLC(es). Our data are consistent with the hypothesis that when a compliant upper airway is coupled with a high airway resistance during panting against an occluded airway, transmission of changes in alveolar pressure to the mouth is incomplete. The resulting underestimation of delta Palv by delta Pm leads to artifactual increases in TLC.

The role of respiratory muscles in the hyperinflation of bronchial asthma

To examine the mechanism of hyperinflation in bronchial asthma we studied lung and chest wall mechanics in 7 asymptomatic patients in whom progressive bronchoconstriction was induced by doubling the amount of inhaled aerosolized histamine. An increase in pulmonary resistance (RL) from 2.5 +/- 0.3 cmH2O . 1-1 . s (mean, +/- 1 SE) to 12.3 +/- 0.9 cmH2 was associated with a linear increase in functional residual capacity (FRC) up to 74.7 +/- 1.7% of control total lung capacity (TLCc). The mean regression coefficient was 2.3% TLCc . cmH2O-1 . 1 . s-1. At each level of hyperinflation the most positive expiratory pleural pressures measured during spontaneous breathing were generally less than the predicted chest wall relaxation pressures, indicating persistent inspiratory muscle contraction throughout expiration. This was predominantly due to inspiratory intercostal and accessory muscle activity, because measurements of transdiaphragmatic pressure indicated complete diaphragmatic relaxation early in expiration. Recruitment of abdominal muscles during expiration, inferred from measurements of gastric pressure (Pg) and abdominal antero-posterior (A-P) diameter, was progressively more apparent with increasing bronchoconstriction. We concluded that the increase in FRC in induced asthma is substantially influenced by persistent inspiratory intercostal and accessory muscle activity during expiration. Concomitant abdominal muscle recruitment results in a chest wall configuration that tends to optimize diaphragmatic function.

Zinc therapy of depressed cellular immunity in acrodermatitis enteropathica. Its correction

A child with hypogammaglobulinemia and intractable diarrhea underwent parenteral alimentation for five months. A clinical syndrome of acrodermatitis enteropathica subsequently developed associated with a depression in thymus-dependent lymphocyte (T cell) numbers, abnormal T-cell mitogen-induced blast transformation, and anergy to skin test antigens. Plasma zinc levels were found to be abnormally low. Zinc therapy resulted in dramatic resolution of the clinical manifestations of acrodermatitis enteropathica. Cell-mediated immune function was also restored to normal, suggesting an important role for zinc and possibly other trace metals in cellular immune responses.

Scleroderma, eosinophilia, and diffuse fasciitis

Skin induration without internal organ involvement, blood and tissue eosinophilla, and fascilitis are features of diffuse fascilitis. However, cellular infiltrates (lymphocytes, plasma cells, and eosinophils) may also be present in the dermis, fat, and muscle. Blood eosinophilia (mild and transient) and skin eosinophilia were observed in about 20% of patients with systemic and localized scleroderma.