Ikaite nucleation at 35 °C challenges the use of glendonite as a paleotemperature indicator.

Glendonites have been found worldwide in marine sediments from the Neoproterozoic Era to the Quaternary Period. The precursor of glendonite, ikaite (CaCO3 · 6H2O), is metastable and has only been observed in nature at temperatures <7 °C. Therefore, glendonites in the sedimentary record are commonly used as paleotemperature indicators. However, several laboratory experiments have shown that the mineral can nucleate at temperatures>7 °C. Here we investigate the nucleation range for ikaite as a function of temperature and pH. We found that ikaite precipitated at temperatures of at least 35 °C at pH 9.3 -10.3 from a mixture of natural seawater and sodium carbonate rich solution. At pH 9.3, we observed pseudomorphic replacement of ikaite by porous calcite during the duration of the experiment (c. 5 hours). These results imply that ikaite can form at relatively high temperatures but will then be rapidly replaced by a calcite pseudomorph. This finding challenges the use of glendonites as paleotemperature indicators.

Diagnostic accuracy of simple tools in monitoring patients with chronic hypoventilation treated with non-invasive ventilation; a prospective cross-sectional study.

OBJECTIVES: To evaluate the sensitivity and specificity of a screening test panel for nocturnal hypoventilation (NH) and other sleep related respiratory events during monitoring of patients with chronic hypercapnic respiratory failure (CRF) treated with NIV. METHODS: We performed a prospective study at Oslo University Hospital. Eligible for inclusion were consecutive adults with CRF due to neuromuscular diseases or chest wall disorders treated with NIV scheduled for a follow-up visit. All patients underwent the screening test panel (clinical evaluation, daytime arterial blood gas (ABG), nocturnal pulse oximetry (SpO2) and data from ventilator software) and the reference tests; sleep polygraphy and nocturnal transcutaneous CO2. RESULTS: Of 67 patients included, NH was confirmed in 23-50 according to the 3 definitions used for NH, apnea-hypopnea index (AHIpolygraphy) ≥ 10 was confirmed in 16 and patient-ventilator asynchrony (PVA) ≥ 10% of total recording time in 14. Sensitivity of the combined screening test panel for NH was 87% (95% confidence interval 66-97), 84% (66-95) and 80% (66-90), for abnormal AHIpolygraphy 91% (59-100) and for PVA 71% (42-92). Sensitivity for NH of SpO2 was 48% (27-69), 39% (22-58) and 38% (24-53) and of daytime ABG 74% (52-90), 74% (55-88) and 68% (53-80). Sensitivity and specificity of AHIsoftware for AHIpolygraphy ≥ 10 was 93% (68-100) and 92% (81-98) respectively. DISCUSSION: In patients treated with long term NIV, screening test panel, nocturnal SpO2 and daytime ABG all failed to accurately detect NH, underlining the importance of nocturnal monitoring of CO2. AHIsoftware accurately identified obstructive events and can be used to modify NIV settings. TRIAL REGISTRATION: N° NCT01845233.

Sleep related respiratory events during non-invasive ventilation of patients with chronic hypoventilation.

BACKGROUND: Non-invasive ventilation (NIV) is increasingly used in the treatment of patients with chronic hypercapnic respiratory failure (CRF). Residual sleep related respiratory events under NIV such as obstructive or central apnea/hypopnea (AH), or patient-ventilator asynchrony (PVA), may compromise treatment efficacy and/or comfort. AIMS OF STUDY: 1/to quantify the frequency and describe the types of both AH and PVA in a large group of stable patients with CRF during night-time NIV; 2/to analyze the influence of these events on overnight pulse oximetry and transcutaneous CO2 and 3/to assess interrater agreement in identifying and quantifying AH and PVA. METHODS: We quantified AH and PVA by performing sleep polygraphy in 67 patients during elective follow-up visits. Traces were scored by two trained physicians. RESULTS: Residual AH were frequent: 34% of the patients had an AH Index >5/hour, with obstructive hypopnea being the most frequent event. In addition, 21% of the patients had PVA >10% of total recording time. No correlation was found between respiratory events and overnight hypercapnia. The intraclass correlation coefficients for scoring AHI and time with PVA were 0.97 (0.94-0.98) and 0.85 (0.75-0.91) respectively. CONCLUSIONS: Residual respiratory events are common in patients treated with long term NIV for chronic hypercapnic respiratory failure and can be scored with a very high interobserver agreement. However, these events were not associated with persistent nocturnal hypercapnia; thus, their clinical relevance has yet to be clarified. CLINICALTRIALS.GOV REGISTRATION N°: NCT01845233.

Validity of transcutaneous PCO2 in monitoring chronic hypoventilation treated with non-invasive ventilation.

BACKGROUND: Non-invasive ventilation (NIV) is an efficient treatment for patients with chronic hypercapnic respiratory failure (CRF), but requires regular monitoring to detect both diurnal and nocturnal residual hypercapnia. The present study was designed to determine 1) whether transcutaneous PCO2 (PtcCO2) is a valid tool for monitoring PaCO2 in this group of patients, and 2) if overnight instrumental drift of the PtcCO2 sensor is clinically significant. METHODS: Sixty-seven patients with CRF on long term NIV were included. Arterial blood gases (ABG) were sampled from the radial artery during PtcCO2 measurement. PtcCO2 was recorded 2 min after ABG sampling. Instrumental drift was tested by measuring a gas of known CO2 concentration after auto-calibration of the sensor in the evening, and on the following morning. FINDINGS: PaCO2 values ranged from 3.97 kPa to 9.0 kPa. Thirty-six (53%) patients were hypercapnic. Correlation between PaCO2 and PtcCO2 was highly significant (r(2) = 0.9, p < 0.0001), Bias (d) and SD of bias (s) were 0.23 kPa and 0.28 kPa respectively, with a minor underestimation of PaCO2. Limits of agreement (d ± 2s) were; -0.32; 0.79 kPa. None of the paired values of PaCO2/PtcCO2 had a difference exceeding 1 kPa. The mean drift of PtcCO2 was 0.14 ± 0.54 kPa/8 h (p = 0.04; 95% CI: 0.01-0.27). INTERPRETATION: With the device tested, in stable patients under NIV-treatment for CRF, PtcCO2 accurately reflects PaCO2. PtcCO2 can be used to monitor CO2 overnight during NIV without any clinically significant drift. TRIAL REGISTRATION N°: NCT01845233.

Respiratory complications associated with spinal cord injury.

BACKGROUND: Respiratory complications are the most common cause of acute and long-term morbidity and mortality in patients with spinal cord injury. MATERIAL AND METHODS: The article is based on a non-systematic search in PubMed and the authors' clinical experience in treatment and follow-up of respiratory complications in patients with spinal cord injury. RESULTS: The extent of respiratory complications is dependent on the level of spinal cord injury and the degree of motor completeness. In acute spinal cord injury, 80 % of patients may suffer from respiratory complications. Long-term follow-up indicates that respiratory complications are the most common cause of death in these patients. The most common respiratory complications are atelectasis, pneumonia and respiratory failure. Prevention of respiratory complications must be initiated immediately, independent of the level of spinal cord injury. The question of mechanical ventilation in the acute setting, and also during long-term follow-up must be addressed, along with aggressive secretion management. Patients with spinal cord injury have a high prevalence of sleep apnea that may influence their quality of life and rehabilitation. INTERPRETATION: Respiratory complications are common in patients with spinal cord injury. These patients need a multidisciplinary approach. All disciplines involved must obtain knowledge of respiratory complications in the acute phase and in the longer term, to ensure patients are referred for necessary pulmonary review and follow-up.

Allergy: a systemic disease? The HUNT and Young-HUNT study, Norway.

A systemic nature of allergic diseases has been hypothesized. As part of this discussion, we studied if adolescent allergic wheeze and increasing combinations of allergic organ involvements (lung, nose and skin) would also increase the reporting of other health problems (headache, muscle pain and abdominal pain). In addition, we studied if parental asthma was associated with adolescent clustering of allergic expressions and if parental asthma with additional health problems (headache or muscle pain) was associated with adolescent reporting allergy in combination with headache, muscle pain and abdominal pain. Adolescents 13-19 yr (n = 8817, 89%) participated in the Young-HUNT study, Norway, 1995-97. Parental data on asthma were eligible in n = 5620. Health and lifestyle were measured by questionnaires and interviews. Associations with additional health problems were significantly strengthened with combinations of wheeze and other allergic expressions. Odds Ratio for associations 'wheeze only', 'wheeze and rhinitis' and 'wheeze, rhinitis and eczema' were for headache 2.1, 3.4 and 3.7; for muscle pain 2.8, 3.2 and 4.9; for abdominal pain 3.6, 4.0 and 4.9. All p for trend were <0.010. Similar results were obtained when studying allergic wheeze; p for trend <0.001. Parental asthma was associated with clustering of adolescent allergic expressions, and parental asthma with headache or muscle pain was significantly associated with reported allergy combined with similar health problems in their offspring. The results indicate that allergy may be expressed beyond organs commonly viewed as part of an allergic disease, and hence may support a hypothesis of a systemic nature of allergic diseases.

Adolescents with wheeze have increased risk of additional health problems. The Young-HUNT study, Norway.

OBJECTIVE: To explore the hypothesis of an association between current wheeze and other health problems in adolescence and to investigate any sex differences. METHODS: N=8817 adolescents aged 13-19 years completed a self-administered questionnaire including questions on health and lifestyle in Norway (1995-1997). RESULTS: All subjective health problems were significantly more prevalent in current wheezers compared to non-wheezers (frequent headache: girls 18% vs. 9%, boys 8% vs. 3%; frequent neck and shoulder pain: girls 10% vs. 5%, boys 6% vs. 2%; frequent joint and muscle pain: girls 6% vs. 2%, boys 6% vs. 2%; and frequent abdominal pain: girls 10% vs. 3%, boys 3% vs.1%). In both sexes, adjusted for covariates, current wheezers had statistically significant increased risk of reporting frequent headache (girls OR=2.0, boys OR=2.9), frequent neck and shoulder pain (girls OR=1.9, boys OR=3.3), frequent joint and muscle pain (girls OR=2.7, boys OR=3.5) and frequent abdominal pain (girls OR=2.7, boys OR=2.0). CONCLUSIONS: Current adolescent wheezers reported more additional health problems compared to non-wheezers. Even if girls reported more symptoms in general, the associations were stronger in boys. The findings are important for the clinical approach to teenage wheezers and should increase doctors' awareness of coexistence of other health complaints in these patients.

Female gender is associated with higher incidence and more stable respiratory symptoms during adolescence.

Childhood asthma and wheeze is more common among boys than girls, while the opposite is found in adults. The main objective was to study the incidence and the course of wheeze and asthma during adolescence with focus on gender differences. In addition, we explored associations between lifestyle factors at baseline and wheeze at follow-up. A total of 2399 adolescents answered validated questionnaires on respiratory symptoms and lifestyle in 1995-1997 (13-15 years) and at follow-up in 2000-2001 (17-19 years). The risk of reporting wheeze and asthma at follow-up was greater in girls compared to boys among subjects reporting no respiratory symptoms at baseline; Relative risk: 1.4 and 2.4, respectively. More girls than boys reported current wheeze at follow-up, both among those with current wheeze (girls 60%, boys 48%) and previous wheeze (girls 33%, boys 28%) at baseline. In girls, development of current wheeze was significantly associated with current smoking (OR=2.8) and stable current wheeze was significantly associated with overweight (OR=2.4). Similar associations were not significant in boys. More girls than boys developed wheeze, had stable wheeze or had relapse of previous symptoms during the four year follow-up. The impact of smoking and overweight may put girls at a higher risk of respiratory symptoms than boys. Awareness of the gender difference in respiratory symptoms is important for diagnosis and preventive strategies during adolescence.

Adolescent respiratory symptoms--girls are at risk: the Young-HUNT study, Norway.

The objective was to study sex differences in adolescence regarding prevalence of asthma and current wheeze and to explore the association between respiratory symptoms and hereditary, lifestyle and socioeconomic factors. Young-HUNT included data comprehensive questionnaire on health, disease, lifestyle and social factors from 8817 teenagers 13-19 years conducted in 1995/97 (89% response rate). Questionnaire on respiratory symptoms was based on the International Study of Asthma and Allergy in Childhood (ISAAC). In age groups 13-16 and 17-19 years, current wheeze was reported by 29.0% and 33.5% among girls and 20.4% and 22.1% among boys, whilst the corresponding figures for asthma were 8.5% and 12.2% among girls and 7.1% and 7.0% among boys. Both wheeze and asthma were significantly more prevalent and increased with age in girls compared to boys. Heredity was associated with asthma, but the association was strongest between parents and children of the same sex. Environmental smoking was associated with asthma and wheeze in girls only. Girls reported more asthma and wheeze in association with overweight compared to boys. Girls reported more wheeze and asthma than boys and seemed more susceptible to risk factors such as environmental smoking and overweight than boys. Moreover, girls with mothers having asthma were more likely to be diagnosed as asthmatics themselves.