Elin Tollefsen

Amyotrophic lateral sclerosis: gender differences in the use of mechanical ventilation

Background and purpose:  Invasive and non‐invasive mechanical ventilation are therapeutic options in patients with amyotrophic lateral sclerosis (ALS). Related to known national ALS incidence figures, the study aims to examine gender aspects versus physiological data in patients with ALS commencing mechanical ventilation.

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.

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.

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.