Mask Continuous Positive Airway Pressure Increases Diaphragm Thickening Fraction in Healthy Subjects.

INTRODUCTION: The most widespread treatment for obstructive sleep apnoea and obesity hypoventilation syndrome is continuous positive airway pressure (CPAP). The addition of inspiratory support is a potential alternative. This is a physiological study to determine the effect of CPAP and inspiratory support pressure on respiratory effort measured by diaphragm thickening fraction (DTF) in healthy volunteers. METHODS: DTF was measured in spontaneously breathing, healthy volunteers during 4 phases: (I) without connection to a ventilator, (II) on a ventilator without any applied pressures, (III) with a CPAP of 5 cmH2O, and (IV) with an additional inspiratory support pressure of 5 cmH2O. RESULTS: Twenty-nine individuals agreed to participate. DTF was similar during the first two phases (32 ± 13% and 35 ± 22%). A considerable increase in DTF to 51 ± 21% was noted in phase III. The introduction of inspiratory support pressure during phase IV led to a reduction in DTF back to 36 ± 23% (p < 0.001). Tidal volume and minute ventilation were both slightly higher in phase IV compared to phase III. CONCLUSION: CPAP without inspiratory support pressure increases respiratory effort measured by DTF in healthy subjects. Further research is required to investigate this phenomenon in a clinical setting.

Costs of Weaning Failure: A Prospective, Multicentre, Controlled, Non-Randomised, Interventional Study on Economic Implications for the German Health Care System.

BACKGROUND: Intensive care patients with respiratory failure often need invasive mechanical ventilation (IMV). With increasing population age and multimorbidity, the number of patients who cannot be weaned from IMV rises as well. Up to 85% of these patients have no access to a certified weaning centre. Their medical care is associated with impaired quality of life and high costs for the German health care system. OBJECTIVES: This study examined the weaning outcome of patients in certified weaning centres after a primarily unsuccessful weaning attempt in order to calculate saving expenses compared to patients on long-term IMV in an outpatient setting. METHODS: In this multicentre, controlled, non-randomised, interventional, prospective study, 61 patients (16 from out-of-hospital long-term IMV, 49 from other hospitals) were referred to a certified weaning centre for a second weaning phase. The incurred costs after 1 year of the latter were compared to insurance claim data of patients who were discharged from an acute hospital stay to receive IMV in an outpatient setting. RESULTS: In the intervention group, 50 patients (82%) could be completely weaned or partially weaned using non-invasive ventilation, thus not needing IMV any longer. The costs per patient for weaning and out-of-hospital care in the intervention group were EUR 114,877.08, and the costs in the comparison cohort were EUR 234,442.62. CONCLUSIONS: Early transfer to a certified weaning centre can increase weaning success and reduce total costs by approximately EUR 120,000 per patient in the first year. Given the existing structural prerequisites in Germany, every patient should have access to a weaning centre before being transferred to long-term IMV, from a medical and health economical point of view.

Causes and Risk Factors for Absenteeism among Medical Staff in German Specialized Lung Clinics during the COVID Pandemic.

BACKGROUND: Staff shortages pose a major challenge to the health system. OBJECTIVES: The objective of this study was to clarify the role of different causative factors we investigated on staff absenteeism during the COVID pandemic. METHODS: The prospective multicentre cohort study assessed the private and professional impact of the pandemic on health care workers (HCWs) using a specially developed questionnaire. HCWs from 7 specialist lung clinics throughout Germany were surveyed from December 1 to December 23, 2021. The current analysis addresses pandemic-related absenteeism. RESULTS: 1,134 HCW (55% female; 18.4% male, 26.3% not willing to provide information on age or gender) participated. 72.8% had received at least one vaccination dose at the time of the survey, and 9.4% reported a COVID infection. Of those with positive tests, 98% reported home quarantine for median (IQR) 14 (12-17) days; 10.3% of those who ultimately tested negative also reported quarantine periods of 14 (7-14) days. 32.2% of vaccinated respondents reported absenteeism due to vaccine reactions of 2 (1-3) days. Overall, 37% (n = 420) of HCW reported pandemic-related absenteeism, with 3,524 total days of absenteeism, of which 2,828 were due to illness/quarantine and 696 to vaccination effects. Independent risk factors for COVID-related absenteeism ≥5 days included already having COVID, but also concern about long-term effects of COVID (OR 1,782, p = 0.014); risk factors for vaccine-related absenteeism ≥2 days included concerns of late effects of vaccination (OR 2.2, 95% CI: 1.4-3.1, p < 0.000). CONCLUSION: Staff shortages due to quarantine or infections and vaccine reactogenicity have put a strain on German respiratory specialists. The fact that staff concerns also contributed to absenteeism may be helpful in managing future pandemic events to minimize staff absenteeism.

Prevention of invasive ventilation (PRiVENT)-a prospective, mixed-methods interventional, multicentre study with a parallel comparison group: study protocol.

BACKGROUND: Invasive mechanical ventilation (IMV) is a standard therapy for intensive care patients with respiratory failure. With increasing population age and multimorbidity, the number of patients who cannot be weaned from IMV increases, resulting in impaired quality of life and high costs. In addition, human resources are tied up in the care of these patients. METHODS: The PRiVENT intervention is a prospective, mixed-methods interventional, multicentre study with a parallel comparison group selected from insurance claims data of the health insurer Allgemeine Ortskrankenkasse Baden-Württemberg (AOK-BW) conducted in Baden-Württemberg, Germany, over 24 months. Four weaning centres supervise 40 intensive care units (ICUs), that are responsible for patient recruitment. The primary outcome, successful weaning from IMV, will be evaluated using a mixed logistic regression model. Secondary outcomes will be evaluated using mixed regression models. DISCUSSION: The overall objective of the PRiVENT project is the evaluation of strategies to prevent long-term IMV. Additional objectives aim to improve weaning expertise in and cooperation with the adjacent Intensive Care Units. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov (NCT05260853).

Multiple breath washout testing in adults with pulmonary disease and healthy controls - can fewer measurements eventually be more?

BACKGROUND: Multiple breath washout (MBW) became a valuable research tool assessing ventilation heterogeneity. However, routine clinical application still faces several challenges. Deriving MBW parameters from three technically acceptable measurements according to current recommendations prolongs test times. We therefore aimed to evaluate reporting only duplicate measurements in healthy adults and pulmonary disease. METHODS: One hundred and fifty-three subjects prospectively underwent conventional lung function testing and closed-circuit SF6-MBW. Three technically acceptable MBW-measurements were obtained in 103 subjects. RESULTS: Lung clearance index (LCI) differed significantly among 19 controls (7.4 ± 0.8), 19 patients with sarcoidosis (8.1 ± 1.2), 32 with bronchial asthma (9.2 ± 1.9) and 33 with COPD (10.8 ± 2.2, p < 0.001). Within-test repeatability was high (coefficient of variation between 2.5% in controls and 3.6% in COPD) and remained unchanged when only including the first two measurements. Likewise, LCI remained stable with mean absolute changes ranging from 0.9 ± 0.8% in controls to 1.5 ± 0.9% in COPD (p = 0.1). Mean test time reduction differed significantly between groups reaching 200 s in COPD (p = 0.01). CONCLUSIONS: Duplicate SF6-MBW-measurements are sufficient in adult patients with pulmonary disease and healthy controls. LCI values and intra-test repeatability are not affected reducing total test time statistically significant. Our findings have the potential to further facilitate application of MBW in research and clinical routine. TRIAL REGISTRATION: NCT03176745 , June 2, 2017 retrospectively registered.

Non-invasive measurement of hemodynamic response to postural stress using inert gas rebreathing.

In postural stress, an increased preload volume leads to higher stroke volume (SV) according to the Frank-Starling law of the heart. The present study aimed to evaluate the hemodynamic response to postural stress using non-invasive inert gas rebreathing (IGR) in patients with normal as well as impaired left ventricular function. Hemodynamic measurements were performed in 91 patients undergoing cardiac magnetic resonance imaging (CMR). Mean cardiac output and SV determined by IGR were 4.4±1.3 l/min and 60±19 ml in the upright position, which increased significantly to 5.0±1.2 l/min and 75±23 ml in the supine position (P<0.01). Left ventricular systolic function was normal [ejection fraction (EF) ≥55%] in 42 patients as determined by CMR. In 21 patients, EF was mildly abnormal (45-54%), in 16 patients moderately abnormal (30-44%) and in 12 patients severely abnormal (<30%). An overall trend for a lower percentage change in SV (%ΔSV) was indicated with increasing impairment of ejection fraction. In patients with abnormal EF in comparison to those with normal EF, the %ΔSV was significantly lower (13% vs. 22%; P=0.03). Non-invasive measurement of cardiac function using IGR during postural changes may be feasible and detected significant difference in %ΔSV in patients with normal and impaired EF according to the Frank-Starling law of the heart. Several clinical scenarios including cases of heart rhythm disturbances or pulmonary or congenital heart disease are worthy of further investigation.

Small Airway Disease in Pulmonary Hypertension-Additional Diagnostic Value of Multiple Breath Washout and Impulse Oscillometry.

Airways obstruction is frequent in patients with pulmonary hypertension (PH). Small airway disease (SAD) was identified as a major contributor to resistance and symptoms. However, it is easily missed using current diagnostic approaches. We aimed to evaluate more elaborate diagnostic tests such as impulse oscillometry (IOS) and SF6-multiple-breath-washout (MBW) for the assessment of SAD in PH. Twenty-five PH patients undergoing body-plethysmography, IOS and MBW testing were prospectively included and equally matched to pulmonary healthy and non-healthy controls. Lung clearance index (LCI) and acinar ventilation heterogeneity (Sacin) differed significantly between PH, healthy and non-healthy controls. Likewise, differences were found for all IOS parameters between PH and healthy, but not non-healthy controls. Transfer factor corrected for ventilated alveolar volume (TLCO/VA), frequency dependency of resistance (D5-20), resonance frequency (Fres) and Sacin allowed complete differentiation between PH and healthy controls (AUC (area under the curve) = 1.0). Likewise, PH patients were separated from non-healthy controls (AUC 0.762) by D5-20, LCI and conductive ventilation heterogeneity (Scond). Maximal expiratory flow (MEF) values were not associated with additional diagnostic values. MBW and IOS are feasible in PH patients both providing additional information. This can be used to discriminate PH from healthy and non-healthy controls. Therefore, further research targeting SAD in PH and evaluation of therapeutic implications is justified.

Influence of electrode positioning on accuracy and reproducibility of electrical velocimetry cardiac output measurements.

Electrical velocimetry (EV) is one of the most recent adaptions of impedance cardiography. Previous studies yielded diverging results identifying several factors negatively influencing accuracy. Although electrode arrangement is suspected to be an influencing factor for impedance cardiography in general, no data for EV is available. We aimed to prospectively assess the influence of electrode position on the accuracy and reproducibility of cardiac output (CO) measurements obtained by EV. Two pairs of standard electrocardiographic electrodes were placed at predefined positions of the thorax in 81 patients. The inter-electrode gap was varied between either 5 or 15 cm by caudal movement of the lowest electrode. Measurements were averaged over 20 s and performed twice at each electrode position. Reference values were determined using cardiac magnetic resonance imaging (CMR). Mean bias was 1.2 ± 1.6 l min(-1) (percentage error 22 ± 28%) between COCMR and COEV at the 5 cm gap significantly improving to 0.5 ± 1.6 l min(-1) (8 ± 28%) when increasing the gap (p < 0.0001). The mean difference between repeated measurements was 0.0 ± 0.3 l min(-1) for the 5 cm and 0.1 ± 0.3 l min(-1) for the 15 cm gap, respectively (p = 0.3). The accuracy of EV can be significantly improved when increasing the lower inter-electrode gap still exceeding the Critchley and Critchley recommendations. Therefore, absolute values should not be used interchangeably in clinical routine. As the reproducibility was not negatively affected, serial hemodynamic measurements can be reliably acquired in stable patients when the electrode position remains unchanged.