Cardiac responses to pressor challenges in congenital central hypoventilation syndrome

Summary Question of the Study   Congenital central hypoventilation syndrome (CCHS) subjects exhibit diminished respiratory-related heart rate variation in addition to defining characteristics of CO₂ insensitivity and reduced ventilatory drive during sleep. Loss of cardiovascular and breathing coupling may diminish blood pressure influences on breathing; such influences may be determined by evaluating cardiorespiratory responses to different pressor challenges.
Patients and Methods   Ten children with CCHS and 10 age- and gender-matched controls were subjected to a forehead cold pressor challenge and to Valsalva maneuvers. Heart and respiratory rates and variability during 30-s baseline and 120-s challenge periods were assessed with scatterplot displays and by analysis of variance procedures.
Results   Cold pressor challenges enhanced breathing efforts and increased respiratory-related heart rate variation in controls but not in CCHS patients, while lower frequency heart rate variability increased in both controls and CCHS subjects. Heart rate variation resulting from voluntary expiratory efforts was present but slightly reduced in CCHS. Respiratory and cardiac rate trends differed in control and CCHS cases.
Conclusions   More-rapidly changing heart rate variation from spontaneous or reflexively-induced sources is diminished in CCHS but remains intact from voluntary expiratory ­efforts, as does slower variation. Loss of reflexive influences on breathing from blood pressure changes may attenuate a source of respiratory drive.     

House dust mite allergen avoidance and self-management in allergic patients with asthma: randomised controlled trial

BACKGROUND: The efficacy of bed covers that are impermeable to house dust mites has been disputed. AIM: The aim of the present study was to investigate whether the combination of 'house dust mite impermeable' covers and a self-management plan, based on peak flow values and symptoms, leads to reduced use of inhaled corticosteroids (ICS) than self-management alone. DESIGN OF STUDY: Prospective, randomised, double blind, placebo-controlled trial. SETTING: Primary care in a south-eastern region of the Netherlands. METHOD: Asthma patients aged between 16 and 60 years with a house dust mite allergy requiring ICS were randomised to intervention and placebo groups. They were trained to use a self-management plan based on peak flow and symptoms. After a 3-month training period, the intervention commenced using house dust mite impermeable and placebo bed covers. The follow-up period was 2 years. Primary outcome was the use of ICS; secondary outcomes were peak expiratory flow parameters, asthma control, and symptoms. RESULTS: One hundred and twenty-six patients started the intervention with house dust mite impermeable or placebo bed covers. After 1 and 2 years, significant differences in allergen exposure were found between the intervention and control groups (P<0.001). No significant difference between the intervention and control groups was found in the dose of ICS (P = 0.08), morning peak flow (P = 0.52), peak flow variability (P = 0.36), dyspnoea (P = 0.46), wheezing (P = 0.77), or coughing (P = 0.41). There was no difference in asthma control between the intervention and control groups. CONCLUSION: House dust mite impermeable bed covers combined with self-management do not lead to reduced use of ICS compared with self-management alone.     

Hemin levels in culture medium of Porphyromonas (Bacteroides) gingivalis regulate both hemin binding and trypsinlike protease production.

Washed cells and Sarkosyl-insoluble outer membrane preparations of the black-pigmented bacteroides Porphyromonas gingivalis W50 bound hemin. The amount of hemin removed from a buffered solution by both cells and outer membranes was significantly larger if bacteria had been grown in broths supplemented with 5 mg of hemin per liter rather than none. Conversely, cells grown without supplemental hemin bound relatively little. However, all preparations bound some hemin. In addition, hemin regulated the production of significantly higher levels of trypsinlike protease by P. gingivalis W50. The nonpigmented variant, W50 BE1, showed no such responses to the levels of hemin in the growth medium.     

Attitudes of subjects at risk and their relatives towards genetic counselling in Huntington''s chorea.

Ninety-two patients suffering from Huntington's chorea (HC) and their spouses, and 91 subjects with an affected parent and their spouses, living in three counties of industrial South Wales, have been studied regarding their knowledge of their inheritance of the disorder. Particular attention was paid to its influence on their attitudes towards child-bearing, telling their children of the risks, and predictive tests. Only 12% of the patients were known to have received professional advice before completing their families, in contrast to 68% of the sample at risk. It is estimated that 82% of the patients and 60% of the subjects at risk had, or might have, restricted their family size had they known in time. The majority found genetic counselling helpful, but did not necessarily wish to alter their child-bearing plans in consequence. It was clear that information provided by the family alone was usually inadequate and that this applied to the present generation at risk as well as to previous generations. It was concluded that the burden of telling children the risks is too great for most parents and that professional help is needed. The long term impact of genetic counselling on the incidence of the disease is impossible to assess without continued monitoring, but preliminary results are encouraging. Attitudes towards a predictive test reflected much conflict: although 56% overall wished to take one, only 40% of those who were parents wished to know if they were at risk of passing the gene on to their children. Few subjects reported severe social stress on learning of their genetic risks, but about one in four reported experiencing significant anxiety.     

Cardiac and respiratory patterns in normal infants and victims of the sudden infant death syndrome

Victims of the sudden infant death syndrome (SIDS) have higher overall heart rates prior to death than do control infants (1). The objective of this study was to partition these heart rate differences by state and to identify any state-dependent differences in heart rate variability and respiratory rate and variability. Twenty-two recordings of electrocardiogram (ECG) and respiration from 16 infants who subsequently died of SIDS were compared with 66 recordings of age-matched control infants. Median cardiac and respiratory rate and variability were computed for each sleep state in each recording, and one-way analysis of variance tests were performed for each variable for infants less than 1 month and for infants greater than 1 month of age. Heart rate was higher in SIDS victims less than 1 month of age than in age-matched controls during all sleep-waking states. SIDS victims greater than 1 month showed higher heart rates during rapid eye movement sleep only. Heart rate variability was also diminished during waking in victims less than 1 month, but much of this difference could be attributed to increased heart rate. These results suggest that, as a group, SIDS victims differ physiologically from control infants and that these differences may be especially prominent during particular sleep-waking states.