Potential Diaphragm Muscle Weakness-related Dyspnea Persists Two Years after COVID-19 and Could Be Improved by Inspiratory Muscle Training: Results of an Observational and an Interventional Trial.

RATIONALE: Diaphragm muscle weakness might underly persistent exertional dyspnea despite normal lung/cardiac function in individuals previously hospitalized for acute COVID-19 illness. OBJECTIVES: Firstly, to determine the persistence and pathophysiological nature of diaphragm muscle weakness and its association with exertional dyspnea two years after hospitalization for COVID-19, and secondly to investigate the impact of inspiratory muscle training (IMT) on diaphragm and inspiratory muscle weakness and exertional dyspnea in individuals with long COVID. METHODS: ~2 years after hospitalization for COVID-19, 30 individuals (11 female, median age 58 [interquartile range (IQR) 51-63] years) underwent comprehensive (invasive) respiratory muscle assessment and evaluation of dyspnea. Eighteen with persistent diaphragm muscle weakness and exertional dyspnea were randomized to 6 weeks of IMT or sham training; assessments were repeated immediately after and 6 weeks after IMT completion. The primary endpoint was change in inspiratory muscle fatiguability immediately after IMT. RESULTS: At median 31 [IQR 23-32] months after hospitalization, 21/30 individuals reported relevant persistent exertional dyspnea. Diaphragm muscle weakness on exertion and reduced diaphragm cortical activation were potentially related to exertional dyspnea. Compared with sham control, IMT improved diaphragm and inspiratory muscle function (sniff transdiaphragmatic pressure 83 [IQR 75-91] vs. 100 [IQR 81-113] cmH2O; p=0.02), inspiratory muscle fatiguability (time to task failure 365 [IQR 284-701] vs. 983 [IQR 551-1494] sec; p=0.05), diaphragm voluntary activation index (79 [IQR 63-92] vs 89 [IQR 75-94]%; p=0.03), and dyspnea (Borg score 7 [IQR 5.5-8] vs. 6 [IQR 4-7]; p=0.03); improvements persisted for 6 weeks after IMT completion. CONCLUSIONS: This study is the first to identify a potential treatment for persisting exertional dyspnea in long COVID, and provide a possible pathophysiological explanation for the treatment benefit. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

[Non-invasive Mechanical Ventilation in Acute Respiratory Failure. Clinical Practice Guidelines - on behalf of the German Society of Pneumology and Ventilatory Medicine]. / S2k-Leitlinie Nichtinvasive Beatmung als Therapie der akuten respiratorischen Insuffizienz.

The guideline update outlines the advantages as well as the limitations of NIV in the treatment of acute respiratory failure in daily clinical practice and in different indications.Non-invasive ventilation (NIV) has a high value in therapy of hypercapnic acute respiratory failure, as it significantly reduces the length of ICU stay and hospitalization as well as mortality.Patients with cardiopulmonary edema and acute respiratory failure should be treated with continuous positive airway pressure (CPAP) and oxygen in addition to necessary cardiological interventions. This should be done already prehospital and in the emergency department.In case of other forms of acute hypoxaemic respiratory failure with only mild or moderately disturbed gas exchange (PaO2/FiO2 > 150 mmHg) there is no significant advantage or disadvantage compared to high flow nasal oxygen (HFNO). In severe forms of ARDS NIV is associated with high rates of treatment failure and mortality, especially in cases with NIV-failure and delayed intubation.NIV should be used for preoxygenation before intubation. In patients at risk, NIV is recommended to reduce extubation failure. In the weaning process from invasive ventilation NIV essentially reduces the risk of reintubation in hypercapnic patients. NIV is regarded useful within palliative care for reduction of dyspnea and improving quality of life, but here in concurrence to HFNO, which is regarded as more comfortable. Meanwhile NIV is also recommended in prehospital setting, especially in hypercapnic respiratory failure and pulmonary edema.With appropriate monitoring in an intensive care unit NIV can also be successfully applied in pediatric patients with acute respiratory insufficiency.

Early Detection of Lung Cancer Using Small RNAs.

INTRODUCTION: Lung cancer remains the deadliest cancer in the world, and lung cancer survival is heavily dependent on tumor stage at the time of detection. Low-dose computed tomography screening can reduce mortality; however, annual screening is limited by low adherence in the United States of America and still not broadly implemented in Europe. As a result, less than 10% of lung cancers are detected through existing programs. Thus, there is a great need for additional screening tests, such as a blood test, that could be deployed in the primary care setting. METHODS: We prospectively recruited 1384 individuals meeting the National Lung Screening Trial demographic eligibility criteria for lung cancer and collected stabilized whole blood to enable the pipetting-free collection of material, thus minimizing preanalytical noise. Ultra-deep small RNA sequencing (20 million reads per sample) was performed with the addition of a method to remove highly abundant erythroid RNAs, and thus open bandwidth for the detection of less abundant species originating from the plasma or the immune cellular compartment. We used 100 random data splits to train and evaluate an ensemble of logistic regression classifiers using small RNA expression of 943 individuals, discovered an 18-small RNA feature consensus signature (miLung), and validated this signature in an independent cohort (441 individuals). Blood cell sorting and tumor tissue sequencing were performed to deconvolve small RNAs into their source of origin. RESULTS: We generated diagnostic models and report a median receiver-operating characteristic area under the curve of 0.86 (95% confidence interval [CI]: 0.84-0.86) in the discovery cohort and generalized performance of 0.83 in the validation cohort. Diagnostic performance increased in a stage-dependent manner ranging from 0.73 (95% CI: 0.71-0.76) for stage I to 0.90 (95% CI: 0.89-0.90) for stage IV in the discovery cohort and from 0.76 to 0.86 in the validation cohort. We identified a tumor-shed, plasma-bound ribosomal RNA fragment of the L1 stalk as a dominant predictor of lung cancer. The fragment is decreased after surgery with curative intent. In additional experiments, results of dried blood spot collection and sequencing revealed that small RNA analysis could potentially be conducted through home sampling. CONCLUSIONS: These data suggest the potential of a small RNA-based blood test as a viable alternative to low-dose computed tomography screening for early detection of smoking-associated lung cancer.

Model-Based Estimation of Inspiratory Effort Using Surface EMG.

OBJECTIVE: The quantification of inspiratory patient effort in assisted mechanical ventilation is essential for the adjustment of ventilatory assistance and for assessing patient-ventilator interaction. The inspiratory effort is usually measured via the respiratory muscle pressure (P mus) derived from esophageal pressure (P es) measurements. As yet, no reliable non-invasive and unobtrusive alternatives exist to continuously quantify P mus. METHODS: We propose a model-based approach to estimate P mus non-invasively during assisted ventilation using surface electromyographic (sEMG) measurements. The method combines the sEMG and ventilator signals to determine the lung elastance and resistance as well as the neuromechanical coupling of the respiratory muscles via a novel regression technique. Using the equation of motion, an estimate for P mus can then be calculated directly from the lung mechanical parameters and the pneumatic ventilator signals. RESULTS: The method was applied to data recorded from a total of 43 ventilated patients and validated against P es-derived P mus. Patient effort was quantified via the P mus pressure-time-product (PTP). The sEMG-derived PTP estimated using the proposed method was highly correlated to P es-derived PTP ([Formula: see text]), and the breath-wise deviation between the two quantities was [Formula: see text]. CONCLUSION: The estimated, sEMG-derived P mus is closely related to the P es-based reference and allows to reliably quantify inspiratory effort. SIGNIFICANCE: The proposed technique provides a valuable tool for physicians to assess patients undergoing assisted mechanical ventilation and, thus, may support clinical decision making.

[The Difficult Airway with Tracheostomy - Manufacturing of an Individualized Tracheal Tube with Modern Imaging and 3D Printing]. / Der schwierige Atemweg mit Tracheostoma.

Case discussion of a 51-year-old female patient with ventilator dependency due to Charcot-Marie-Tooth-Hoffmann syndrome (HMSN I) and cervical spinal fusion with complex tracheal canula management. Following 16 years of noninvasive ventilation due to chronic hypercapnic failure with 24 hour dependency on the ventilator, an elective surgical tracheostomy and switch to invasive ventilation was carried out. Because of severe cervical scoliosis, common tracheal canulae could not provide an adequate fit. With development of a 3D model according to the CT scans of the patient, an individualized tracheal tube was customized that provided excellent ventilatory results and the ability to speak during invasive ventilation.

Surface EMG-based quantification of inspiratory effort: a quantitative comparison with Pes.

BACKGROUND: Inspiratory patient effort under assisted mechanical ventilation is an important quantity for assessing patient-ventilator interaction and recognizing over and under assistance. An established clinical standard is respiratory muscle pressure [Formula: see text], derived from esophageal pressure ([Formula: see text]), which requires the correct placement and calibration of an esophageal balloon catheter. Surface electromyography (sEMG) of the respiratory muscles represents a promising and straightforward alternative technique, enabling non-invasive monitoring of patient activity. METHODS: A prospective observational study was conducted with patients under assisted mechanical ventilation, who were scheduled for elective bronchoscopy. Airway flow and pressure, esophageal/gastric pressures and sEMG of the diaphragm and intercostal muscles were recorded at four levels of pressure support ventilation. Patient efforts were quantified via the [Formula: see text]-time product ([Formula: see text]), the transdiaphragmatic pressure-time product ([Formula: see text]) and the EMG-time products (ETP) of the two sEMG channels. To improve the signal-to-noise ratio, a method for automatically selecting the more informative of the sEMG channels was investigated. Correlation between ETP and [Formula: see text] was assessed by determining a neuromechanical conversion factor [Formula: see text] between the two quantities. Moreover, it was investigated whether this scalar can be reliably determined from airway pressure during occlusion maneuvers, thus allowing to quantify inspiratory effort based solely on sEMG measurements. RESULTS: In total, 62 patients with heterogeneous pulmonary diseases were enrolled in the study, 43 of which were included in the data analysis. The ETP of the two sEMG channels was well correlated with [Formula: see text] ([Formula: see text] and [Formula: see text] for diaphragm and intercostal recordings, respectively). The proposed automatic channel selection method improved correlation with [Formula: see text] ([Formula: see text]). The neuromechanical conversion factor obtained by fitting ETP to [Formula: see text] varied widely between patients ([Formula: see text]) and was highly correlated with the scalar determined during occlusions ([Formula: see text], [Formula: see text]). The occlusion-based method for deriving [Formula: see text] from ETP showed a breath-wise deviation to [Formula: see text] of [Formula: see text] across all datasets. CONCLUSION: These results support the use of surface electromyography as a non-invasive alternative for monitoring breath-by-breath inspiratory effort of patients under assisted mechanical ventilation.

German National Guideline for Treating Chronic Respiratory Failure with Invasive and Non-Invasive Ventilation: Revised Edition 2017 - Part 1.

Today, invasive and non-invasive home mechanical ventilation have become a well-established treatment option. Consequently, in 2010, the German Respiratory Society (Deutsche Gesellschaft für Pneumologie und Beatmungsmedizin, DGP) has leadingly published the Guidelines on "Non-Invasive and Invasive Mechanical Ventilation for Treatment of Chronic Respiratory Failure." However, continuing technical evolutions, new scientific insights, and health care developments require an extensive revision of the Guidelines. For this reason, the updated Guidelines are now published. Thereby, the existing chapters, namely technical issues, organizational structures in Germany, qualification criteria, disease-specific recommendations including special features in pediatrics as well as ethical aspects and palliative care, have been updated according to the current literature and the health care developments in Germany. New chapters added to the Guidelines include the topics of home mechanical ventilation in paraplegic patients and in those with failure of prolonged weaning. In the current Guidelines, different societies as well as professional and expert associations have been involved when compared to the 2010 Guidelines. Importantly, disease-specific aspects are now covered by the German Interdisciplinary Society of Home Mechanical Ventilation (DIGAB). In addition, societies and associations directly involved in the care of patients receiving home mechanical ventilation have been included in the current process. Importantly, associations responsible for decisions on costs in the health care system and patient organizations have now been involved.

German National Guideline for Treating Chronic Respiratory Failure with Invasive and Non-Invasive Ventilation - Revised Edition 2017: Part 2.

Today, invasive and non-invasive home mechanical ventilation have become a well-established treatment option. Consequently, in 2010, the German Respiratory Society (DGP) has leadingly published the guidelines on "Non-Invasive and Invasive Mechanical Ventilation for Treatment of Chronic Respiratory Failure." However, continuing technical evolutions, new scientific insights, and health care developments require an extensive revision of the guidelines. For this reason, the updated guidelines are now published. Thereby, the existing chapters, namely technical issues, organizational structures in Germany, qualification criteria, disease-specific recommendations including special features in pediatrics as well as ethical aspects and palliative care, have been updated according to the current literature and the health care developments in Germany. New chapters added to the guidelines include the topics of home mechanical ventilation in paraplegic patients and in those with failure of prolonged weaning. In the current guidelines, different societies as well as professional and expert associations have been involved when compared to the 2010 guidelines. Importantly, disease-specific aspects are now covered by the German Interdisciplinary Society of Home Mechanical Ventilation (DIGAB). In addition, societies and associations directly involved in the care of patients receiving home mechanical ventilation have been included in the current process. Importantly, associations responsible for decisions on costs in the health care system and patient organizations have now been involved.

Activation of respiratory muscles during respiratory muscle training.

It is unknown which respiratory muscles are mainly activated by respiratory muscle training. This study evaluated Inspiratory Pressure Threshold Loading (IPTL), Inspiratory Flow Resistive Loading (IFRL) and Voluntary Isocapnic Hyperpnea (VIH) with regard to electromyographic (EMG) activation of the sternocleidomastoid muscle (SCM), parasternal muscles (PARA) and the diaphragm (DIA) in randomized order. Surface EMG were analyzed at the end of each training session and normalized using the peak EMG recorded during maximum inspiratory maneuvers (Sniff nasal pressure: SnPna, maximal inspiratory mouth occlusion pressure: PImax). 41 healthy participants were included. Maximal activation was achieved for SCM by SnPna; the PImax activated predominantly PARA and DIA. Activations of SCM and PARA were higher in IPTL and VIH than for IFRL (p<0.05). DIA was higher applying IPTL compared to IFRL or VIH (p<0.05). IPTL, IFRL and VIH differ in activation of inspiratory respiratory muscles. Whereas all methods mainly stimulate accessory respiratory muscles, diaphragm activation was predominant in IPTL.

Resting limb muscle perfusion during inspiratory muscle loading in hypoxia and normoxia.

INTRODUCTION: Fatiguing of respiratory muscles reduces peripheral muscle perfusion. Further, acute hypoxia enhances respiratory muscle fatigue. This study investigated the effects of inspiratory muscle loading (IML) on resting locomotor muscle perfusion in hypoxia compared to normoxia. METHODS: Ten subjects completed two study days of fatiguing IML (blinded, randomized) in normobaric hypoxia (targeted oxygen saturation 80%) and normoxia, respectively. Contrast-enhanced ultrasound (CEUS) of the gastrocnemius muscle and popliteal doppler ultrasonography were used to monitor muscle perfusion. Based on CEUS and monitored cardiac output, perfusion surrogate parameters (CLPaer and CLPap) were established. RESULTS: Muscle perfusion declines early during IML in normoxia (CLPaer: -54±25%, p<0.01; CLPap: -58±32%, p<0.01) and hypoxia (CLPaer: -43±23%, p<0.01; CLPap: -41±20%, p<0.01). Hypoxia compared to normoxia increased cardiac output before (+23±19%, p<0.01 ANOVA) and during (+22±20%, p<0.01 ANOVA) IML, while local muscle perfusion during IML remained unchanged (CLPaer: p=0.41 ANOVA; CLPap: p=0.29 ANOVA). CONCLUSION: Acute hypoxia compared to normoxia does not affect locomotor muscle perfusion during fatiguing IML.

[Near-Drowning with Good Outcome after ECMO-Therapy and Therapeutic Hypothermia Despite 20 Minutes of Anoxia and 16 Hours of Hypoxia]. / Überleben mit guter Neurologie nach Beinahe-Ertrinken durch ECMO-Therapie und therapeutischer Hypothermie trotz 20-minütiger Anoxie und 16-stündiger Hypoxie.

Introduction Drowning with submersion over 10 minutes is associated with a high mortality. Here, we present a case, in which a good neurological outcome was achieved after interdisciplinary, intensive care therapy despite submersion of 20 minutes followed by 16 hours of hypoxia. History A 19 year old man drowned in fresh-water. After 20 minutes submersion he was localized and salvaged from 8 meters depth and primarily resuscitated successfully after 10 minutes. Within the next hour, there condition worsened by respiratory deterioration due to a massive capillary leak syndrome in addition to a disseminated intravascular coagulation. Treatment This made implantation of a veno-venous ECMO (extracorporeal membrane oxygenation) therapy necessary. Despite intensive care medicine including extracorporeal therapy a sufficient oxygenation (arterial pO2 > 60 mmHg) was reached only 16 hours after the drowning. Clinical Course During this time the patient was treated with a mild therapeutic hypothermia for cerebral protection. Despite the prolonged hypoxia, ECMO could be removed five days after the drowning and the patient was extubated after another five days without significant neurological deficits. Conclusion Despite submersion of 20 minutes followed by prolonged hypoxia, a good neurological outcome could be achieved in our patient. This case suggests, that tolerance of hypoxia is possibly underestimated after drowning.

Activation of respiratory muscles during weaning from mechanical ventilation.

PURPOSE: Respiratory muscle dysfunction is a key component of weaning failure. Balancing respiratory muscle loading and unloading by applying different ventilation modes along with spontaneous breathing episodes are established weaning strategies. However, the effects of body positioning on the respiratory muscles during weaning remains unclear. MATERIALS AND METHODS: This study aimed at assessing respiratory drive by surface electromyography (EMG) of the diaphragm (EMGdia) and parasternal muscles (EMGpara) in tracheotomized patients during prolonged weaning in 3 randomized body positions-supine, 30° semirecumbent, and 80° sitting-during mechanical ventilation and spontaneous breathing. RESULTS: Nine patients were included for analysis. Cardiorespiratory parameters (heart rate, blood pressure, arterial oxygen saturation, dyspnea) did not change under each condition (all P>.05). EMGpara and EMGdia did not change under mechanical ventilation (both P>.05). EMGdia changed under spontaneous breathing from supine to sitting (0.45±0.26 vs 0.32±0.19; P=.012) and between semirecumbent to sitting (0.41±0.23 vs 0.32±0.19; P=.039), whereas EMGpara did not change. CONCLUSIONS: This is the first study to show that body positioning influences respiratory drive to the diaphragm in tracheotomized patients with prolonged weaning from mechanical ventilation during unassisted breathing. Sitting position reduces respiratory drive compared with semirecumbent and supine positioning and might therefore be favored during spontaneous breathing trials.

The Severe Respiratory Insufficiency Questionnaire for Subjects With COPD With Long-Term Oxygen Therapy.

BACKGROUND: Respiratory insufficiency in COPD may present as hypoxic and/or hypercapnic respiratory failure treated with long-term oxygen therapy (LTOT) and/or noninvasive ventilation (NIV) with LTOT. The Severe Respiratory Insufficiency Questionnaire (SRI) is a tool for the assessment of health-related quality of life (HRQOL) in subjects receiving NIV. However, it remains unclear whether the SRI is also capable of assessing and discriminating HRQOL in subjects receiving LTOT. METHODS: Stable subjects with COPD receiving LTOT or NIV + LTOT (NIV) were prospectively recruited and completed the SRI, lung function tests, and blood gases. Confirmatory factor analysis for construct validity and internal consistency reliability were calculated. RESULTS: One hundred fifty-five subjects were included (113 LTOT, 42 NIV). The Cronbach α coefficient of the 7 subscales ranged between 0.69 and 0.89 (LTOT) and between 0.79 and 0.93 (NIV), respectively. In both groups, confirmatory factor analysis revealed a one-factor model for the SRI summary scale; in 5 subscales, one- or 2-factor models could be established. Group differences in the SRI subsets were all P <.05 (except for physical functioning) with higher scores in subjects receiving NIV. CONCLUSIONS: The SRI showed high reliability and validity in subjects with COPD receiving LTOT. Subjects receiving LTOT had lower SRI scores, indicating a poorer HRQOL compared with subjects with established NIV and LTOT.

Diaphragmatic fatigue during inspiratory muscle loading in normoxia and hypoxia.

INTRODUCTION: Diaphragmatic fatigue (DF) occurs during strenuous loading of respiratory muscles (e.g., heavy-intensity whole-body exercise, normocapnic hyperpnea, inspiratory resistive breathing). DF develops early on during normoxia, without further decline toward task failure; however, its progression during inspiratory muscle loading in during hypoxia remains unclear. Therefore, the present study used volume-corrected transdiaphragmatic pressures during supramaximal magnetic phrenic nerve stimulation (Pdi,twc) to investigate the effect of hypoxia on the progression of diaphragmatic fatigue during inspiratory muscle loading. METHODS: Seventeen subjects completed two standardized rounds of inspiratory muscle loading (blinded, randomized) under the following conditions: (i) normoxia, and (ii) normobaric hypoxia (SpO2 80%), with Pdi,twc assessment every 45 s. RESULTS: In fatiguers (i.e., Pdi,twc reduction >10%, n=10), biometric approximation during normoxia is best represented by Pdi,twc=4.06+0.83 exp(-0.19 × x), in contrast to Pdi,twc=4.38-(0.05 × x) during hypoxia. CONCLUSION: Progression of diaphragmatic fatigue during inspiratory muscle loading assessed by Pdi,tw differs between normoxia and normobaric hypoxia: in the former, Pdi,tw follows an exponential decay, whereas during hypoxia, Pdi,tw follows a linear decline.

Walking with Non-Invasive Ventilation Does Not Prevent Exercise-Induced Hypoxaemia in Stable Hypercapnic COPD Patients.

BACKGROUND: Non-invasive positive pressure ventilation (NPPV) in addition to supplemental oxygen improves arterial oxygenation, walking distance and dyspnea when applied during exercise in stable hypercapnic COPD patients. The aim of the current study was to investigate whether NPPV without supplemental oxygen is capable of preventing severe exercise-induced hypoxemia in these patients when applied during walking. METHODS AND RESULTS: 15 stable hypercapnic COPD patients (FEV1 29.9 ± 15.9%) performed two 6-minute walk tests (6MWT) with a rollator in a randomized cross-over design: using either supplemental oxygen (2.4 ± 0.7 L/min) or NPPV (inspiratory/expiratory positive airway pressure of 28.2 ± 2.8 / 5.5 ± 1.5 mbar) without supplemental oxygen. RESULTS: 10 patients were able to complete both 6MWT. 6MWT with supplemental oxygen resulted in no changes for PO2 (pre: 67.3 ± 11.2 mmHg vs. post: 65.6 ± 12.0 mmHg, p = 0.72) whereas PCO2 increased (pre: 50.9 ± 8.1 mmHg vs. post: 54.3 ± 10.0 mmHg (p < 0.03). During 6MWT with NPPV PO2 significantly decreased from 66.8 ± 7.2 mmHg to 55.5 ± 10.6 mmHg (p < 0.02) whereas no changes occurred in PCO2 (pre: 50.6 ± 7.5 mmHg vs. post: 53.0 ± 7.1 mmHg; p = 0.17). Walking distance tended to be lower in 6MWT with NPPV compared to 6MWT with supplemental oxygen alone (318 ± 160 m vs. 377 ± 108 m; p = 0.08). CONCLUSION: The use of NPPV during walking without the application of supplemental oxygen does not prevent exercise-induced hypoxemia in patients with stable hypercapnic COPD.

Assessing respiratory function depends on mechanical characteristics of balloon catheters.

BACKGROUND: Respiratory muscle function and lung and chest wall mechanics are reliably assessed by esophageal and gastric balloon catheters. The aim of this in vitro bench study was to assess the mechanical properties of commercially available balloon catheters using an experimental model with 3 defined compliances (27, 54, 90 mL/cm H2O). METHODS: Six catheters were investigated in 4 conditions: (1) balloon pressure during initial inflation, (2) static pressure measurements at different filling volumes, (3) estimation of set compliances in the experimental lung model at different levels of superimposed pressure, and (4) elastic balloon properties after 16 h of inflation. RESULTS: 5/6 catheters showed initial pressure artifacts resulting from material adhesion. All static pressure measurements could be performed with an error < 1 cm H2O. Balloon overfilling resulted in larger errors in 4/6 catheters. Compliance determined from pressure measurements via the catheters differed by < 5% from that determined from direct pressure measurements. Sixteen hours of inflation resulted in a broader working range, that is, overfilling effects occurred at higher filling volumes. CONCLUSIONS: The reliability of pressure measurements and estimation of the lung model's compliance in the tested catheters are high. Filling volume appears to be critical for precise pressure measurement and compliance estimation. At first use, adhesion of the balloon material might prevent reliable pressure measurement.

Modified ventilatory response characteristics to exercise in breath-hold divers.

Specific adjustments to repeated extreme apnea are not fully known and understood. While a blunted ventilatory chemosensitivity to CO2 is described for elite breath-hold divers (BHDs) at rest, it is unclear whether specific adaptations affect their response to dynamic exercise. Eight elite BHDs with a previously validated decrease in CO2 chemosensitivity, 8 scuba divers (SCDs), and 8 matched control subjects were included in a study where markers of ventilatory response, Fowler's dead space, partial pressure of carbon dioxide (pCO2), and blood lactate concentrations during cycle exercise were measured. Maximal power output did not differ between the groups, but lactate threshold (θL) appeared at a significantly lowered respiratory compensation point (RCP) and at a higher VO2 for the BHDs. End-tidal (petCO2) and estimated arterial pCO2 (paCO2) were significantly higher in BHDs at θL, the RCP, and maximum exhaustion. BHDs showed a significantly (P < .01) slower breathing pattern in relation to a given tidal volume at a specific work rate. In summary, BHDs presented signs of a metabolic shift from aerobic to anaerobic energy supply, decreased chemosensitivity during exercise, and a distinct ventilatory-response pattern during cycle exercise that differs from SCDs and controls.

The combination of exercise and respiratory training improves respiratory muscle function in pulmonary hypertension.

PURPOSE: Increased dyspnea and reduced exercise capacity in pulmonary arterial hypertension (PAH) can be partly attributed to impaired respiratory muscle function. This prospective study was designed to assess the impact of exercise and respiratory training on respiratory muscle strength and 6-min walking distance (6MWD) in PAH patients. METHODS: Patients with invasively confirmed PAH underwent 3 weeks of in-hospital exercise and respiratory training, which was continued at home for another 12 weeks. Medication remained constant during the study period. Blinded observers assessed efficacy parameters at baseline (I) and after 3 (II) and 15 weeks (III). Respiratory muscle function was assessed by twitch mouth pressure (TwPmo) during nonvolitional supramaximal magnetic phrenic nerve stimulation. RESULTS: Seven PAH patients (4 women; mean pulmonary artery pressure 45 ± 11 mmHg, median WHO functional class 3.1 ± 0.4, idiopathic/associated PAH n = 5/2) were included. The training program was feasible and well tolerated by all patients with excellent compliance. TwPmo was I: 0.86 ± 0.37 kPa, II: 1.04 ± 0.29 kPa, and III: 1.27 ± 0.44 kPa, respectively. 6MWD was I: 417 ± 51 m, II: 509 ± 39 m, and III: 498 ± 39 m, respectively. Both TwPmo (+0.41 ± 0.34 kPa, +56 ± 39 %) and 6MWD (+81 ± 30 m, +20 ± 9 %) increased significantly in the period between baseline and the final assessment (pairwise comparison: p = 0.012/<0.001; RM-ANOVA considering I, II, III: p = 0.037/<0.001). CONCLUSIONS: Exercise and respiratory training as an adjunct to medical therapy may be effective in patients with PAH to improve respiratory muscle strength and exercise capacity. Future, randomized, controlled trials should be carried out to further investigate these findings.