Endobronchial cryobiopsy may shorten the time to cancer diagnosis: a retrospective study.

Endobronchial cryobiopsy from visualised intraluminal tumour lesions may decrease the rate of diagnostic failure and shorten the time to diagnosis https://bit.ly/3NkyJ98.

Hyperoxemia post thoracic surgery - Does it matter?

Introduction: Post-operative oxygen therapy is used to prevent hypoxemia and surgical site infection. However, with improvements of anesthesia techniques, post-operative hypoxemia incidence is declining and the benefits of oxygen on surgical site infection have been questioned. Moreover, hyperoxemia might have adverse effects on the pulmonary and cardiovascular systems. We hypothesized hyperoxemia post thoracic surgery is associated with post-operative pulmonary and cardiovascular complications. Methods: Consecutive lung resection patients were included in this post-hoc analysis. Post-operative pulmonary and cardiovascular complications were prospectively assessed during the first 30 post-operative days, or hospital stay. Arterial blood gases were analyzed at 1, 6 and 12 h after surgery. Hyperoxemia was defined as arterial partial pressure of oxygen (PaO2)>100 mmHg. Patients with hyperoxemia duration in at least two adjacent time points were considered as hyperoxemic. Student t-test, Mann-Whitney U test and two-tailed Fisher exact test were used for group comparison. P values < 0.05 were considered statistically significant. Results: Three hundred sixty-three consecutive patients were included in this post-hoc analysis. Two hundred five patients (57%), were considered hyperoxemic and included in the hyperoxemia group. Patients in the hyperoxemia group had significantly higher PaO2 at 1, 6 and 12 h after surgery (p < 0.05). Otherwise, there was no significant difference in age, sex, comorbidities, pulmonary function tests parameters, lung surgery procedure, incidence of post-operative pulmonary and cardiovascular complications, intensive care unit and hospital length of stay and 30-day mortality. Conclusion: Hyperoxemia after lung resection surgery is common and not associated with post-operative complications or 30-day mortality.

The risk of post-operative pulmonary complications in lung resection candidates with normal forced expiratory volume in 1 s and diffusing capacity of the lung for carbon monoxide: a prospective multicentre study.

Introduction: According to the guidelines for preoperative assessment of lung resection candidates, patients with normal forced expiratory volume in 1 s (FEV1) and diffusing capacity of the lung for carbon monoxide (D LCO) are at low risk for post-operative pulmonary complications (PPC). However, PPC affect hospital length of stay and related healthcare costs. We aimed to assess risk of PPC for lung resection candidates with normal FEV1 and D LCO (>80% predicted) and identify factors associated with PPC. Methods: 398 patients were prospectively studied at two centres between 2017 and 2021. PPC were recorded from the first 30 post-operative days. Subgroups of patients with and without PPC were compared and factors with significant difference were analysed by uni- and multivariate logistic regression. Results: 188 subjects had normal FEV1 and D LCO. Of these, 17 patients (9%) developed PPC. Patients with PPC had significantly lower pressure of end-tidal carbon dioxide (P ETCO2 ) at rest (27.7 versus 29.9; p=0.033) and higher ventilatory efficiency (V'E/V'CO2 ) slope (31.1 versus 28; p=0.016) compared to those without PPC. Multivariate models showed association between resting P ETCO2 (OR 0.872; p=0.035) and V'E/V'CO2 slope (OR 1.116; p=0.03) and PPC. In both models, thoracotomy was strongly associated with PPC (OR 6.419; p=0.005 and OR 5.884; p=0.007, respectively). Peak oxygen consumption failed to predict PPC (p=0.917). Conclusions: Resting P ETCO2 adds incremental information for risk prediction of PPC in patients with normal FEV1 and D LCO. We propose resting P ETCO2 be an additional parameter to FEV1 and D LCO for preoperative risk stratification.

Prediction of Postoperative Complications: Ventilatory Efficiency and Rest End-tidal Carbon Dioxide.

BACKGROUND: Cardiopulmonary exercise testing parameters including ventilatory efficiency (VE/VCO2 slope) are used for risk assessment of lung resection candidates. However, many patients are unable or unwilling to undergo exercise. VE/VCO2 slope is closely related to the partial pressure of end-tidal carbon dioxide (PETCO2). We hypothesized PETCO2 at rest predicts postoperative pulmonary complications. METHODS: Consecutive lung resection candidates were included in this prospective multicenter study. Postoperative respiratory complications were assessed from the first 30 postoperative days or from the hospital stay. Student t test or Mann-Whitney U test was used for comparison. Multivariate stepwise logistic regression analysis was used to analyze association with the development of postoperative pulmonary complications. The De Long test was used to compare area under the curve (AUC). Data are summarized as median (interquartile range). RESULTS: Three hundred fifty-three patients were analyzed, of which 59 (17%) developed postoperative pulmonary complications. PETCO2 at rest was significantly lower (27 [24-30] vs 29 [26-32] mm Hg; P < .01) and VE/VCO2 slope during exercise significantly higher (35 [30-40] vs 29 [25-33]; P < .01) in patients who developed postoperative pulmonary complications. Both rest PETCO2 with odds ratio 0.90 (95% confidence interval [CI] 0.83-0.97); P = .01 and VE/VCO2 slope with odds ratio 1.10 (95% CI 1.05-1.16); P < .01 were independently associated with postoperative pulmonary complications by multivariate stepwise logistic regression analysis. There was no significant difference between AUC of both models (rest PETCO2: AUC = 0.79 (95% CI 0.74-0.85); VE/VCO2 slope: AUC = 0.81 (95% CI 0.75-0.86); P = .48). CONCLUSIONS: PETCO2 at rest has similar prognostic utility as VE/VCO2 slope, suggesting rest PETCO2 may be used for postoperative pulmonary complications prediction in lung resection candidates.

Ventilatory efficiency is superior to peak oxygen uptake for prediction of lung resection cardiovascular complications.

INTRODUCTION: Ventilatory efficiency (VE/VCO2 slope) has been shown superior to peak oxygen consumption (VO2) for prediction of post-operative pulmonary complications in patients undergoing thoracotomy. VE/VCO2 slope is determined by ventilatory drive and ventilation/perfusion mismatch whereas VO2 is related to cardiac output and arteriovenous oxygen difference. We hypothesized pre-operative VO2 predicts post-operative cardiovascular complications in patients undergoing lung resection. METHODS: Lung resection candidates from a published study were evaluated by post-hoc analysis. All of the patients underwent preoperative cardiopulmonary exercise testing. Post-operative cardiovascular complications were assessed during the first 30 post-operative days or hospital stay. One-way analysis of variance or the Kruskal-Wallis test, and multivariate logistic regression were used for statistical analysis and data summarized as median (IQR). RESULTS: Of 353 subjects, 30 (9%) developed pulmonary complications only (excluded from further analysis), while 78 subjects (22%) developed cardiovascular complications and were divided into two groups for analysis: cardiovascular only (n = 49) and cardiovascular with pulmonary complications (n = 29). Compared to patients without complications (n = 245), peak VO2 was significantly lower in the cardiovascular with pulmonary complications group [19.9 ml/kg/min (16.5-25) vs. 16.3 ml/kg/min (15-20.3); P<0.01] but not in the cardiovascular only complications group [19.9 ml/kg/min (16.5-25) vs 19.0 ml/kg/min (16-23.1); P = 0.18]. In contrast, VE/VCO2 slope was significantly higher in both cardiovascular only [29 (25-33) vs. 31 (27-37); P = 0.05] and cardiovascular with pulmonary complication groups [29 (25-33) vs. 37 (34-42); P<0.01)]. Logistic regression analysis showed VE/VCO2 slope [OR = 1.06; 95%CI (1.01-1.11); P = 0.01; AUC = 0.74], but not peak VO2 to be independently associated with post-operative cardiovascular complications. CONCLUSION: VE/VCO2 slope is superior to peak VO2 for prediction of post-operative cardiovascular complications in lung resection candidates.

Cerebral air embolism complicating transbronchial lung biopsy: A case report.

BACKGROUND: In this case report we describe an extremely rare case of cerebral air embolism following transbronchial lung biopsy (TBLB). Only a few cases of this rare complication were described previously. Every bronchologist should recognize this severe adverse event. Prompt recognition of this complication is mandatory in order to initiate supportive measures and consider hyperbaric oxygen therapy. CASE SUMMARY: In this case report we describe an extremely rare case of cerebral air embolism following TBLB. Only a few cases of this rare complication were described previously. Our patient had an incidental finding of lung tumour and pulmonary emphysema. Cerebral air embolism developed during bronchoscopy procedure, immediately after the third trans-bronchial lung biopsy sample and caused cerebral ischaemia of the right hemisphere and severe left-sided hemiplegia. Despite timely initiation of hyperbaric oxygen therapy hemiplegia didn´t resolve and the patient died several weeks later. Cerebral air embolism is an extremely rare complication of TBLB. This condition should be considered in case the patient remains unresponsive or presents with acute neurological symptoms in the post-intervention period since early recognition, diagnosis and hyperbaric oxygen therapy initiation are key factors determining the patient´s outcome. CONCLUSION: Within this report, we conclude that air/gas embolism is an extremely rare complication after TBLB, which should be considered in case the patient remains unresponsive or presents with acute neurological symptoms in the post-intervention period after bronchoscopy. The current gold standard for diagnosis is computed tomography scan of the head. After recognition of this complication we suggest immediate hyperbaric oxygen therapy, if available.

Extracorporeal Membrane Oxygenation Use in Thoracic Surgery.

This narrative review is focused on the application of extracorporeal membrane oxygenation (ECMO) in thoracic surgery, exclusive of lung transplantation. Although the use of ECMO in this indication is still rare, it allows surgery to be performed in patients where conventional ventilation is not feasible-especially in single lung patients, sleeve lobectomy or pneumonectomy and tracheal or carinal reconstructions. Comparisons with other techniques, various ECMO configurations, the management of anticoagulation, anesthesia, hypoxemia during surgery and the use of ECMO in case of postoperative respiratory failure are reviewed and supported by two cases of perioperative ECMO use, and an overview of published case series.

Mitigation of Exercise Oscillatory Ventilation Score by Cardiac Resynchronization Therapy.

BACKGROUND: Exercise oscillatory ventilation (EOV) is a consequence of ventilatory control system instability and is commonly observed in patients with advanced heart failure (HF); it is associated with adverse prognosis. The goal of this study was to evaluate the effects of cardiac resynchronization therapy (CRT) on oscillatory ventilation as quantified by a proposed EOV score. METHODS AND RESULTS: Consecutive patients with HF (N = 35) who underwent clinically indicated CRT, cardiopulmonary exercise testing and carbon dioxide (CO2) chemosensitivity by rebreathe before and 4-6 months after CRT were included in this post hoc analysis. With CRT, EOV scores improved in 22 patients (63%). In these patients, left ventricular ejection fraction, left atrial volume, brain natriuretic peptide concentration, and CO2 chemosensitivity significantly improved after CRT (P < 0.05). Furthermore, minute ventilation per unit CO2 production significantly decreased, and end-tidal CO2 increased at rest and at peak exercise post-CRT. Multiple regression analysis showed only the change of CO2 chemosensitivity to be significantly associated with the improvement of the EOV score (b = 0.64; F = 11.3; P = 0.004). In the group without EOV score improvement (n = 13), though left ventricular ejection fraction significantly increased with CRT (P = 0.015), no significant changes in ventilation or gas exchange were observed. CONCLUSION: The EOV score was mitigated by CRT and was associated with decreased CO2 chemosensitivity.

Poor ventilatory efficiency during exercise may predict prolonged air leak after pulmonary lobectomy.

Poor ventilatory efficiency, defined as the increase in minute ventilation relative to carbon dioxide production during exercise (VE/VCO2 slope), may be associated with dynamic hyperinflation and thereby promote the development of prolonged air leak (PAL) after lung resection. Consecutive lung lobectomy candidates (n = 96) were recruited for this prospective two-centre study. All subjects underwent pulmonary function tests and cardiopulmonary exercise testing prior to surgery. PAL was defined as the presence of air leaks from the chest tube on the 5th postoperative day and developed in 28 (29%) subjects. Subjects with PAL were not different in terms of age, sex, American Society of Anesthesiologists class, type of surgery (thoracotomy/video-assisted thoracoscopic surgery) and site of surgery (right/left lung; upper/lower lobes). Subjects with PAL had more frequent pleural adhesions (50% vs 21%; P = 0.006) and steeper VE/VCO2 slope (35 ± 7 vs 30 ± 5; P = 0.001). Stepwise logistic regression showed that only the presence of pleural adhesions [odds ratio (OR) 3.9, 95% confidence interval (CI) 1.4-10.9; P = 0.008] and VE/VCO2 slope (OR 1.1, 95% CI 1.0-1.2; P = 0.003) were independently associated with PAL (AUC 0.74, 95% CI 0.62-0.86). We conclude that a high VE/VCO2 slope during exercise may be helpful in identifying patients at greater risk for the development of PAL after lung lobectomy. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov identifier: NCT03498352.

Pulmonary Limitations in Heart Failure.

The heart and lungs are intimately linked. Hence, impaired function of one organ may lead to changes in the other. Accordingly, heart failure is associated with airway obstruction, loss of lung volume, impaired gas exchange, and abnormal ventilatory control. Cardiopulmonary exercise testing is an excellent tool for evaluation of gas exchange and ventilatory control. Indeed, many parameters routinely measured during cardiopulmonary exercise testing, including the level of minute ventilation per unit of carbon dioxide production and the presence of exercise oscillatory ventilation, have been found to be strongly associated with prognosis in patients with heart failure.

Cardiopulmonary exercise testing for identification of patients with hyperventilation syndrome.

INTRODUCTION: Measurement of ventilatory efficiency, defined as minute ventilation per unit carbon dioxide production (VE/VCO2), by cardiopulmonary exercise testing (CPET) has been proposed as a screen for hyperventilation syndrome (HVS). However, increased VE/VCO2 may be associated with other disorders which need to be distinguished from HVS. A more specific marker of HVS by CPET would be clinically useful. We hypothesized ventilatory control during exercise is abnormal in patients with HVS. METHODS: Patients who underwent CPET from years 2015 through 2017 were retrospectively identified and formed the study group. HVS was defined as dyspnea with respiratory alkalosis (pH >7.45) at peak exercise with absence of acute or chronic respiratory, heart or psychiatric disease. Healthy patients were selected as controls. For comparison the Student t-test or Mann-Whitney U test were used. Data are summarized as mean ± SD or median (IQR); p<0.05 was considered significant. RESULTS: Twenty-nine patients with HVS were identified and 29 control subjects were selected. At rest, end-tidal carbon dioxide (PETCO2) was 27 mmHg (25-30) for HVS patients vs. 30 mmHg (28-32); in controls (p = 0.05). At peak exercise PETCO2 was also significantly lower (27 ± 4 mmHg vs. 35 ± 4 mmHg; p<0.01) and VE/VCO2 higher ((38 (35-43) vs. 31 (27-34); p<0.01)) in patients with HVS. In contrast to controls, there were minimal changes of PETCO2 (0.50 ± 5.26 mmHg vs. 6.2 ± 4.6 mmHg; p<0.01) and VE/VCO2 ((0.17 (-4.24-6.02) vs. -6.6 (-11.4-(-2.8)); p<0.01)) during exercise in patients with HVS. The absence of VE/VCO2 and PETCO2 change during exercise was specific for HVS (83% and 93%, respectively). CONCLUSION: Absence of VE/VCO2 and PETCO2 change during exercise may identify patients with HVS.

Transbronchial biopsy from the upper pulmonary lobes is associated with increased risk of pneumothorax - a retrospective study.

BACKGROUND: Pneumothorax (PTX) is one of the most common complications of transbronchial biopsy (TBB). Previous research suggests that upper pulmonary lobe TBB may be associated with increased risk of PTX development. The aim of this study was to compare the risk of PTX after TBB performed from different pulmonary lobes. METHODS: All bronchoscopic records from the period January 1st, 2015 - December 31st, 2017 (from the Department of Respiratory Diseases, University Hospital Brno, Czech Republic) were retrospectively analyzed. Of the 3542 bronchoscopic records, 796 patients underwent TBB and were further analyzed. Basic demographic data, TBB procedure-related factors, smoking history and radiological features were analyzed. Furthermore, in patients who developed PTX, PTX onset, PTX symptoms, distribution of the abnormal radiological findings and duration of hospitalization were also analyzed. RESULTS: Patients who developed PTX had significantly lower body mass index (BMI) and more than 4 samples taken during procedure (all p < 0.05). TBB performed from the left upper pulmonary lobe was associated with a significant risk of PTX development (OR 2.27; 95% CI 1.18-4.35; p = 0.02). On the contrary, TBB performed from the right lower lobe was associated with a significant reduction of risk of developing PTX (OR 0.47; 95% CI 0.22-0.98; p = 0.04). Logistic regression analysis showed BMI (OR 1.08; 95% CI 1.02-1.16; p = 0.01), left upper lobe as sampling site (OR 2.15; 95% CI 1.13-4.11; p = 0.02) and more than 4 samples taken (OR 1.91; 95% CI 1.04-3.49; p = 0.04) to be significantly associated with PTX development. CONCLUSIONS: We conclude that TBB from the left upper pulmonary lobe is associated with significantly increased risk of post-procedural PTX. The right lower pulmonary lobe seems to be the safest sampling site to perform TBB. In patients with diffuse-type pulmonary disease, TBB should be performed preferably from the right lower lobe in order to decrease the risk of post-procedural PTX.

Ventilatory Efficiency Identifies Patients Prone to Hypoxemia During One-Lung Ventilation.

OBJECTIVES: One-lung ventilation (OLV) may be complicated by hypoxemia. Ventilatory efficiency, defined as the ratio of minute ventilation to carbon dioxide output (VE/VCO2), is increased with ventilation/perfusion mismatch and pulmonary artery hypertension, both of which may be associated with hypoxemia. Hence, the authors hypothesized increased VE/VCO2 will predict hypoxemia during OLV. DESIGN: Prospective observational study. SETTING: Single-center, university, tertiary care hospital. PARTICIPANTS: The study comprised 50 consecutive lung resection candidates. INTERVENTIONS: All patients underwent cardiopulmonary exercise testing before surgery. Patients who required inspired oxygen fraction (FiO2) ≥0.7 to maintain arterial oxygen (O2) saturation >90% after 30 minutes of OLV were considered to be hypoxemic. The Student t or Mann-Whitney U test were used for comparison of patients who became hypoxemic and those who did not. Multiple regression analysis adjusted for age, sex, and body mass index was used to evaluate which parameters were associated with the VE/VCO2 slope. Data are summarized as mean ± standard deviation. MEASUREMENTS AND MAIN RESULTS: Twenty-four patients (48%) developed hypoxemia. There was no significant difference in age, sex, and body mass index between hypoxemic and nonhypoxemic patients. However, patients with hypoxemia had a significantly higher VE/VCO2 slope (30 ± 5 v 27 ± 4; p = 0.04) with exercise and lower partial pressure of oxygen/FiO2 (129 ± 92 v 168 ± 88; p = 0.01), higher mean positive end-expiratory pressure (6.6 ± 1.5 v 5.6 ± 0.9 cmH2O; p = 0.02), and lower mean pulse oximetry O2 saturation/FiO2 index (127 ± 20 v 174 ± 17; p < 0.01) during OLV. Multiple regression showed VE/VCO2 to be independently associated with the mean pulse oximetry O2 saturation/FiO2 index (b = -0.28; F = 3.1; p = 0.05). CONCLUSIONS: An increased VE/VCO2 slope may predict hypoxemia development in patients who undergo OLV.

Low leptin concentration may identify heart failure patients with central sleep apnea.

Low leptin concentration has been shown to be associated with central sleep apnea in heart failure patients. We hypothesized that low leptin concentration predicts central sleep apnea. Consecutive ambulatory New York Heart Association (NYHA) classes I-IV heart failure patients were studied prospectively, including measurement of serum leptin, echocardiography and polysomnography. Sleep apnea was defined by type (central/mixed/obstructive) and by apnea-hypopnea index ≥5 by polysomnography. Subjects were divided into four groups by polysomnography: (1) central sleep apnea, (2) mixed apnea, (3) no apnea and (4) obstructive sleep apnea. Fifty-six subjects were included. Eighteen subjects were diagnosed with central sleep apnea, 15 with mixed apnea, 12 with obstructive apnea and 11 with no sleep apnea. Leptin concentration was significantly lower in central sleep apnea compared to obstructive apnea (8 ± 10.7 ng mL-1 versus 19.7 ± 14.7 ng mL-1 , P Ë‚ 0.01) or no sleep apnea (8 ± 10.7 ng mL-1 versus 17.1 ± 8.4 ng mL-1 , P Ë‚ 0.01). Logistic regression showed leptin to be associated independently with central sleep apnea [odds ratio (OR): 0.19; 95% confidence interval (CI): 0.06-0.62; area under the curve (AUC): 0.80, P < 0.01]. For the detection of central sleep apnea, a cut-off value for leptin concentration 5 ng mL-1 yielded a sensitivity of 50% and specificity of 89%. In conclusion, a low leptin concentration may have utility for the screening of heart failure patients for central sleep apnea.

Increased microcirculatory heterogeneity in patients with obstructive sleep apnea.

INTRODUCTION: Obstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and has been associated with major cardiovascular comorbidities. We hypothesized that the microcirculation is impaired in patients with OSA and that the magnitude of impairment correlates to OSA severity. METHODS: Subjects were consecutive patients scheduled for routine diagnostic polysomnography (PSG). OSA was defined by paradoxical rib cage movements together with abdominal excursions and by the apnea-hypopnea index (AHI) (events/hour; no apnea AHI<5; mild apnea 5≤AHI<15; moderate apnea 15≤AHI<30; severe apnea AHI ≥30). Sidestream darkfield imaging was used to assess the sublingual microcirculation. Recordings of sublingual microcirculation (5 random sites) were performed before and after overnight PSG. Data are summarized as mean (±SD); p values <0.05 were considered statistically significant. RESULTS: Thirty-three consecutive patients were included. OSA was diagnosed in 16 subjects (4 moderate, 12 severe). There was no significant difference in microcirculation between subjects with moderate OSA and without OSA. However, compared to subjects without OSA, subjects with severe OSA (AHI≥30) showed a significant decrease of microvascular flow index (-0.07±0.17 vs. 0.08±0.14; p = 0.02) and increase of microvascular flow index heterogeneity (0.06±0.15 vs. -0.06±0.11; p = 0.02) overnight. Multiple regression analysis (adjusted for age and gender) showed both decrease of flow and increase of flow heterogeneity associated with AHI (b = -0.41; F = 1.8; p = 0.04 and b = 0.43; F = 1.9; p = 0.03, respectively). CONCLUSION: Acute overnight microcirculatory changes are observed in subjects with severe OSA characterized by decreased flow and increased flow heterogeneity.

Is it intestinal tuberculosis again? Case report.

This case report focuses on an immigrant admitted to the Department of Respiratory Diseases, University Hospital Brno due to suspicion of relapsing intestinal tuberculosis. The patient presented with fever, night sweat, weight loss, diarrhea, and a history of several tuberculosis attacks in the last few years. None of the examinations confirmed the presence of active tuberculosis but raised suspicion of hematological malignancy. Pancytopenia was present in the peripheral blood. However, bone marrow examination and flowcytometry excluded the presence of a hematological malignancy. The results pointed to the possibility of vitamin B12 or folate deficiency that were both confirmed consequently by serum biochemical tests. Cobalamin and folate deficiency were caused by short bowel syndrome that developed after a major intestinal resection that the patient underwent in his past. Combined treatment including vitamins, pancreatic enzymes substitution, antidiarrhoics and spasmolytics was administered. The general health status of the patient improved rapidly with restitution of hematopoiesis, weight gain, and a decrease by 80% in daily number of stools. Clinical appearance of intestinal tuberculosis, short bowel syndrome and of cobalamin and folate deficiency as well as pathophysiology, diagnosis and treatment of these uncommon or even rare diseases are discussed in this case report.Key words: intestinal tuberculosis - pancytopenia - short bowel syndrome - vitamin B12 deficiency.

Respiratory induced heart rate variability during slow mechanical ventilation : Marker to exclude brain death patients.

BACKGROUND: Respiratory induced heart rate variability (rHRV) was analysed in mechanically ventilated patients during two levels of sedation and brain death. Our aim was to determine whether rHRV can distinguish between different levels of sedation and especially between brain death and sedated patients. METHODS: In this study 30 critically ill and 23 brain death patients were included and four respiratory rates of 15, 12, 8 and 6 breaths per minute, each lasting 5 min were used. Two sedation levels, basal and deep, were performed in the critically ill patients. Heart rate and blood pressure changes induced by ventilation were subsequently detected and analysed. RESULTS: Significant differences were found in rHRV and rHRV adjusted for tidal volume (rHRV/VT) between critically ill and brain death patients during slow breathing at 6 or 8 breaths per minute. The rHRV at 6 breaths per minute was below 15 ms in all brain death subjects except one. The rHRV/VT was lower than 25 ms/l at both 6 and 8 breaths per minute in all brain death patients and simultaneously at 75% of non-brain death patients was higher (specificity 1, sensitivity 0.24). Differences in rHRV and rHRV/VTs between basal and deep sedation were not significant. CONCLUSIONS: The main clinical benefit of the study is the finding that rHRV and rHRV/VT during 6 and 8 breaths per minute can differentiate between critically ill and brain death patients. An rHRV/VT exceeding 25 ms/l reliably excludes brain death.

Sex differences in leptin modulate ventilation in heart failure.

BACKGROUND: Leptin modulates ventilation and circulating levels are higher in normal women than men. OBJECTIVES: The aim of this study was to compare exercise ventilation and gas exchange in men and women with heart failure (HF) and their relation to circulating leptin concentration. METHODS: Consecutive HF patients were studied by cardiopulmonary exercise testing and assay of circulating leptin concentration. RESULTS: Fifty-seven men and 20 women were similar with respect to age, BMI, NYHA class, left ventricular ejection fraction, and peak oxygen consumption (all p > 0.05). Leptin concentration was lower (10.3 ± 10 vs. 25.3 ± 16 ng/mL; p < 0.01) and peak exercise ventilatory efficiency (VE/VCO2) was higher (43 ± 10 vs. 36 ± 5; p < 0.01) in men. Leptin concentration was associated with peak exercise VE/VCO2 (b = -0.35; F = 5.6; p = 0.02). CONCLUSION: Men have significantly lower circulating leptin concentration and increased ventilatory drive during exercise than women with comparable HF. In men with HF, lower leptin concentration may account for an increased ventilatory drive.

The utility of perioperative polygraphy in the diagnosis of obstructive sleep apnea.

OBJECTIVE/BACKGROUND: Obstructive sleep apnea (OSA) is highly prevalent and often undiagnosed in surgical patients. The aim of this study was to compare polygraphy (PG) performed on sedated patients during surgery to overnight polysomnography (PSG). It was hypothesized that perioperative PG may be used to diagnose OSA. PATIENTS/METHODS: Overnight PSG was performed three days prior to surgery. For surgery, spinal anesthesia and sedation with propofol infusion were used. Sedation depth was monitored by the Bispectral index and maintained for all patients (target level 75). Echocardiography studies were available in three patients, and all were diagnosed with diastolic dysfunction. Relatively high prevalence of CSA in patients with diastolic dysfunction has been previously reported. During surgery, PG recording (Embletta) was performed. Sleep apnea was defined by the type (central/obstructive apnea ≥50%) and by the apnea-hypopnea index (AHI) (events/hour: AHI < 5 no apnea; 5 ≤ AHI < 15 mild apnea; 15 ≤ AHI < 30 moderate apnea; AHI ≥30 severe apnea). Bland-Altman plots were used for analysis, and 2 × 2 decision statistics were calculated for several cut-off values of the AHI. Data were shown as bias with limits of agreement (bias±1.96 standard deviations). RESULTS: Nineteen subjects were studied: nine (47%) were diagnosed with obstructive, seven (37%) with central sleep apnea, and three (16%) with no sleep apnea by overnight PSG. Perioperative PG bias was 12 (-37; 61) for AHI; 6 (-25; 37) for obstructive apnea; 0 (-4; 4) for central apnea, and 6 (-31; 43) for hypopnea. For the detection of OSA, a PG cut-off value of AHI 5 yielded 89% sensitivity and 60% specificity, AHI 15 yielded 86% sensitivity and 67% specificity, and AHI 30 yielded 100% sensitivity and 71% specificity. CONCLUSION: Wide limits of agreement preclude perioperative PG to be used as a diagnostic method; however, it may be useful to screen sedated surgical patients for OSA.

Resting End-Tidal Carbon Dioxide Predicts Respiratory Complications in Patients Undergoing Thoracic Surgical Procedures.

BACKGROUND: Ventilatory efficiency (V˙e/V˙co2 slope [minute ventilation to carbon dioxide output slope]) has been shown to predict morbidity and mortality in lung resection candidates. Patients with increased V˙e/V˙co2 during exercise also exhibit an increased V˙e/V˙co2 ratio and a decreased end-tidal CO2 at rest. This study hypothesized that ventilatory values at rest predict respiratory complications and death in patients undergoing thoracic surgical procedures. METHODS: Inclusion criteria for this retrospective, multicenter study were thoracotomy and cardiopulmonary exercise testing as part of routine preoperative assessment. Respiratory complications were assessed from the medical records (from the hospital stay or from the first 30 postoperative days). For comparisons, Student's t test or the Mann-Whitney U test was used. Logistic regression and receiver operating characteristic analyses were performed for evaluation of measurements associated with respiratory complications. Data are summarized as mean ± SD; p <0.05 is considered significant. RESULTS: Seventy-six subjects were studied. Postoperatively, respiratory complications developed in 56 (74%) patients. Patients with postoperative respiratory complications had significantly lower resting tidal volume (0.8 ± 0.3 vs 0.9 ± 0.3L; p = 0.03), lower rest end-tidal CO2 (28.1 ± 4.3vs 31.5 ± 4.2 mm Hg; p < 0.01), higher resting V˙e/V˙co2 ratio (45.1 ± 7.1 vs 41.0 ± 6.4; p = 0.02), and higher V˙e/V˙co2 slope (34.9 ± 6.4 vs 31.2 ± 4.3; p = 0.01). Logistic regression (age and sex adjusted) showed resting end-tidal CO2 to be the best predictor of respiratory complications (odds ratio: 1.21; 95% confidence interval: 1.06 to 1.39; area under the curve: 0.77; p = 0.01). CONCLUSIONS: Resting end-tidal CO2 may identify patients at increased risk for postoperative respiratory complications of thoracic surgical procedures.