Ventilatory efficiency measured during sub-maximal cardiopulmonary exercise testing predicts postoperative outcomes following heart transplantation.

Cardiopulmonary exercise testing is commonly used to evaluate patients for heart transplantation. We assessed the utility of ventilatory efficiency (VE/VCO2 ) to predict perioperative outcomes following heart transplantation. We retrospectively reviewed all patients undergoing cardiopulmonary exercise testing prior to heart transplantation at our center. Spearman's coefficient showed a correlation between VE/VCO2 and ICU free days in the first 30-days post-transplant (R = -.37, p < .01). A VE /VCO2 cut-off >35 was associated with significantly lower median ICU-free days (23.0 vs. 27 days; p < .01) and a higher likelihood of postoperative morbidity (OR = 5.64, 95% CI = 1.75-18.16; p < .01). Multiple regression analysis controlling for peak oxygen consumption and right heart catheter parameters showed VE/VCO2 >35 is independently associated with lower ICU-free days (p < .01) and postoperative morbidity (p = .02). Peak oxygen consumption <15 mL/min/kg was not associated with higher ICU or hospital-free days. VE/VCO2 >35 independently predicts early postoperative morbidity in patients undergoing heart transplantation.

Exercise induced bronchodilation: a phenomenon more common, greater magnitude and more prolonged in older adults than in adolescents.

OBJECTIVE: There are few studies in clinically healthy subjects describing and quantifying exercise-induced bronchodilation (EIBd). This study aimed to describe and compare the magnitude and time course changes in post-exercise forced expired volume at the first second (FEV1) in healthy adolescents, younger adults, and older adults. METHODS: Adolescent (n = 73, aged 10-17 years), younger adult (n = 35, aged 18-25 years), and older adult (n = 25, aged 35-66 years) subjects with normal spirometry z-scores completed a maximal cardiopulmonary exercise test using the standardized exponential exercise test protocol on a cycle ergometer performed at stable temperature and humidity. Spirometry was performed pre-exercise and at 1-, 3-, 5-, and 10-minutes post-exercise to determine the percentage change in FEV1 compared to baseline. EIBd was defined as a ≥ 5% increase in post-exercise FEV1. RESULTS: Increases in FEV1 at one-minute post-exercise were observed in the adolescents (1.3%) and young adults (6.0%) with FEV1 returning to baseline after ten minutes. Compared to the adolescents, the older adults showed significantly greater and sustained increases in FEV1 at 1-, 3-, 5-, and 10-minutes post-exercise (6.4, 4.6, 4.7, and 3.8%, p < 0.05). At 1-minute post exercise a significantly greater proportion of younger adults (54%, p < 0.01) and older adults (64%, p < 0.01) demonstrated EIBd compared to the adolescent group (15%). CONCLUSION: Healthy older adults had a higher prevalence, greater magnitude and more prolonged EIBd compared to healthy adolescent and young adult subjects.

Ethnicity, socioeconomic status and the severity and course of non-cystic fibrosis bronchiectasis.

BACKGROUND AND AIMS: This study evaluated whether there are ethnic factors which affect the severity and progression of bronchiectasis in our adult multi-ethnic population in Auckland, New Zealand. METHODS: Clinical records were reviewed from patients attending the outpatient facilities of our institution between 2007 and 2010. Data collected included demographics, clinical features, smoking status, self-reported ethnicity, socioeconomic status (NZDep), pulmonary function and sputum microbiology. RESULTS: A total of 437 patients was identified: median age 65 years, 66% female, mean forced expiratory volume in the first second (FEV1 ) 62.4% predicted, and 10.5% of patients had recurrent growth of Pseudomonas aeruginosa. Patients of Maori and Pacific ethnicity were overrepresented compared to the institution population catchment and had more severe impairment of lung function: mean % predicted FEV1 for Pacific 52.0, Maori 58.6, European 68.6, Asian 64.2 (P < 0.0001). This was independent of socioeconomic status. However, no overall decline was seen in serial lung function measurements, either across the whole cohort or in any particular ethnic group. CONCLUSIONS: Patients of Maori and Pacific ethnicity are both overrepresented and have more severe bronchiectasis in this cohort, independent of socioeconomic status. Ethnicity did not predict decline in pulmonary function. Further studies into genetic predisposition to bronchiectasis in Maori or Pacific people may be warranted.

A description of sleep behaviour in healthy late pregnancy, and the accuracy of self-reports.

BACKGROUND: The importance of maternal sleep and its contribution to maternal and fetal health during pregnancy is increasingly being recognised. However, the ability to accurately recall sleep practices during pregnancy has been questioned. The aim of this study is to test the accuracy of recall of normal sleep practices in late pregnancy. METHODS: Thirty healthy women between 35 and 38 weeks of gestation underwent level III respiratory polysomnography (PSG) with infrared digital video recordings in their own homes. Data regarding sleep positions, number of times getting out of bed during the night and respiratory measures were collected. A sleep questionnaire was administered the morning after the recorded sleep. Continuous data were assessed using Spearman's Rho and Bland-Altman. Cohen's Kappa was used to assess recall in the categorical variables. RESULTS: Two-thirds of participants went to sleep on their left side. There was good agreement in sleep onset position between video and questionnaire data (Kappa 0.52), however the there was poor agreement on position on wakening (Kappa 0.24). The number of times getting out of bed during the night was accurately recalled (Kappa 0.65). Twenty five out of 30 participants snored as recorded by PSG. Questionnaire data was inaccurate for this measure. Bland-Altman plots demonstrated acceptable agreement between video and questionnaire data for estimated sleep duration, but not the time taken to fall asleep (sleep latency). One participant had mild obstructive sleep apnoea and another probable high upper airways resistance. CONCLUSIONS: Sleep onset position, sleep duration and the number of times getting out of bed during the night were accurately recalled, but sleep latency and sleep position on waking were not. This study identifies the sleep variables that can be accurately obtained by questionnaire and those that cannot.

Validation of thoracic impedance cardiography by echocardiography in healthy late pregnancy.

BACKGROUND: Assessment of stroke volume (SV) is often necessary in clinical and research settings. The clinically established method for SV assessment in pregnancy is echocardiography, but given its limitations, it is not always an appropriate measurement tool. Thoracic impedance cardiography (ICG) allows continuous, non-invasive SV assessment. However, SV determination relies on assumptions regarding the thoracic shape that may mean the algorithm is not valid in pregnancy. The available data regarding the validity of ICG against an established reference standard using modern SV algorithms are both limited and conflicting. We aimed to test the validity of ICG in a clinically realistic setting in late pregnancy using echocardiography. METHODS: Twenty-nine women in late pregnancy underwent standard echocardiography assessments with simultaneous ICG measurement. Agreement between devices was tested using Bland-Altman analysis. RESULTS: Bland-Altman analysis of the relationship between ICG and echocardiography demonstrated that the 95% limits of agreement exceeded acceptable or expected ranges. Measures of maternal and fetal anthropometry do not account for the lack of agreement. CONCLUSIONS: Absolute values of SV as determined by ICG are not valid in pregnancy. Further work is required to examine the ability of ICG to assess relative changes in maternal haemodynamics in late pregnancy.

Improved ventilatory response during exercise over time after concussion: A case report.

This case study reports the exercise ventilatory responses of a 17-year-old female who sustained a traumatic brain injury (TBI) which resulted in loss of consciousness. Subsequently, she suffered from post-concussion syndrome accompanied by orthostatic and exercise intolerance. A cardiopulmonary exercise test (CPET) was performed 2 years post-TBI. The results demonstrated significant hypoventilation with elevated PetCO2 and ventilatory equivalents, progressive desaturation, and pre-syncope symptoms limiting exercise capacity. A repeat CPET 4 years post-TBI demonstrated a similar exercise capacity limited by pre-syncope symptoms. However, there was a marked improvement in the ventilatory response, with appropriate ventilation, PetCO2, and ventilatory equivalents, and only minor desaturation near peak exercise. Hypoventilation during exercise has been reported in subjects with post-concussion syndrome; however, with time the exercise ventilatory response can potentially normalize as observed in this subject.

Novel application of Poincaré analysis to detect and quantify exercise oscillatory ventilation.

Objective.Exercise oscillatory ventilation (EOV) is frequently observed in individuals with cardiac disease. Assessment of EOV relies on pattern recognition and this subjectivity and lack of quantification limits the widespread clinical use of EOV as a prognostic marker. Poincaré analysis quantifies the short (SD1) and long-term (SD2) variability of a signal and may provide an alternative means to identify and quantify unstable exercise breathing patterns. This study aimed to determine if Poincaré analysis can distinguish between the breathing patterns of healthy control subjects and individuals being assessed for heart transplantation with and without EOV.Approach.Thirty-nine subjects performed a cardiopulmonary exercise test as part of heart transplant assessment and were subjectively classified into two groups according to the presence of EOV: non-EOV (n = 19) and EOV (n = 20). The control group (n = 24) consisted of healthy adults. Poincaré analysis (SD1 and SD2) was performed for minute ventilation (V̇E) and tidal volume (VT) normalized to forced vital capacity (V̇EnandV̇Tn), and breathing frequency (BF) for breath-by-breath data over the 10-15 ml · min-1 · kg-1V̇O2range.Main results.Poincaré analysis showed similar exercise ventilatory responses between the non-EOV and control group. BF was found to discriminate between subjects with stable and unstable ventilation. BF SD1 was significantly higher in the EOV group compared to the non-EOV (7.9 versus 4.6,p < 0.01) and control (7.9 versus 4.2,p < 0.01) groups. The EOV group had significantly greater BF SD2 compared to the non-EOV (5.7 versus 3.5,p < 0.01) and control (5.7 versus 3.5,p < 0.01) groups.Significance.We demonstrated that this novel application of Poincaré analysis can objectively distinguish and quantify unstable from stable breathing patterns during exercise. In subjects being assessed for heart transplantation the presence of EOV is associated with greater BF variability. Poincaré analysis provides an objective measure to identify and quantify EOV.Summary at a glance.As EOV may indicate abnormal ventilatory control, there is a need for an objective measure to identify and quantify unstable from stable ventilation during exercise. We developed a method of quantifying BF variation by the application of Poincaré analysis and demonstrated higher than normal variability of BF in subjects being assessed for heart transplantation who demonstrated EOV.

Quantifying tidal expiratory flow limitation using a vector-based analysis technique.

Objective. Tidal expiratory flow limitation (EFLT) is commonly identified by tidal breaths exceeding the forced vital capacity (FVC) loop. This technique, known as the Hyatt method, is limited by the difficulties in defining the FVC and tidal flow-volume (TV) loops. The vector-based analysis (VBA) technique described and piloted in this manuscript identifies and quantifies EFLTas tidal breaths that conform to the contour of the FVC loop.Approach. The FVC and TV loops are interpolated to generate uniformly spaced plots. VBA is performed to determine the smallest vector difference between each point on the FVC and TV curves, termed the flow reserve vector (FRV). From the FVC point yielding the lowest FRV, the tangential angles of the FVC and TV segments are recorded. If the TV and FVC loops become parallel, the difference between the tangential angles tends towards zero. We infer EFLTas parallel TV and FVC segments where the FRV is < 0.1 and the tangential angle is within ±18 degrees for ≥5% of TV. EFLTis quantified by the percent of TV loop fulfilling these criteria. We compared the presence and degree of EFLTat rest and during peak exercise using the Hyatt method and our VBA technique in 25 healthy subjects and 20 subjects with moderate-severe airflow obstruction.Main results. Compared to the Hyatt method, our VBA technique reported a significantly lower degree of EFLTin healthy subjects during peak exercise, and in obstructed subjects at rest and during peak exercise. In contrast to the Hyatt method, our VBA technique re-classified five subjects (one in the healthy group and four in the obstructed group) as demonstrating EFLT.Significance.Our VBA technique provides an alternative approach to determine and quantify EFLTwhich may reduce the overestimation of the degree EFLTand more accurately identify subjects experiencing EFLT.

Complex valve disease: pre-surgical functional capacity evaluation using peak oxygen consumption.

BACKGROUND AND AIM OF THE STUDY: Complex heart valve disease constitutes both mixed and multiple valve pathologies that coexist in a single heart. The chronicity of complex valve disease results in a slow decline in functional capacity. Currently, very few data exist relating to chronic complex valve disease. The clinical assessment of exertional dyspnea (NYHA class) is central to the decision to operate and predict a prognosis. Dyspnea causes significant functional limitations. Peak oxygen consumption (peak VO2) is the 'gold standard' of objectively measuring functional aerobic capacity, and is an important predictor of prognosis. The onset of dyspnea is the most common indication for valve surgery. The study aim, in patients with complex valve disease, was to: (i) objectively assess functional aerobic capacity using peak VO2; and (ii) compare the differences between NYHA classes I and II in relation to body composition, echocardiographic severity, and functional capacity METHODS: A total of 45 patients with complex valve disease, who had been referred for the timing of surgery, was evaluated. The control group comprised 15 healthy subjects. All patients underwent a clinical assessment (to determine NYHA class), echocardiography and cardiopulmonary testing (peak VO2). RESULTS: Patients with complex valve disease achieved significantly lower peak VO2 values than controls (16 +/- 5.9 versus 31.4 +/- 5.9 ml/kg/min; p = 0.0001). The peak VO2 (percentage predicted) was significantly different between asymptomatic (NYHA class I) patients (70.9 +/- 20%) and symptomatic (NYHA class II) patients (55.1 +/- 21%; p = 0.003), with an overlap between classes. There was no significant difference in the echocardiographic severity of the valve lesions between NYHA classes. In a multivariable regression analysis, the peak VO2 and VEN/VCO2 slope were powerful predictors of poor outcome (Hazards ratio 2.15, 5.62; p <0.05). CONCLUSION: Patients with complex valve disease show significant functional capacity impairment, which may be difficult to detect from their clinical presentation. Consequently, peak VO2 measurements are required for the objective evaluation of functional capacity. The detection of a decline in peak VO2 will improve the timing of valve replacement and repair, and avoid adverse outcomes.

Effect of surfactant deficiency and surfactant replacement on airway patency in the piglet lung.

We investigated the effect of surfactant deficiency on airway patency and the effectiveness of surfactant replacement as either an instilled liquid bolus, a non-hygroscopic aerosol or a hygroscopic aerosol. Small airway patency was assessed in isolated piglet lungs by passing a continuous flow of gas though a cannulated airway. Occlusion was assessed by measuring increases in pressure in the cannula that resulted from airway obstruction. In surfactant-deficient conditions the amount of airway closure increased approximately three-fold. However, administration of exogenous surfactant as an instilled liquid bolus, non-hygroscopic aerosol or a hygroscopic aerosol decreased airway closure such that it was statistically similar to that recorded prior to induction of surfactant deficiency, although the instilled and hygroscopic aerosol surfactant both appeared superior to the non-hygroscopic aerosol. These experiments showed that pulmonary surfactant does have a role in maintaining airway patency and that airway closure induced by surfactant deficiency could be reduced by administration of surfactant in any of the aforementioned forms.

In Vivo Confocal Microscopy of Corneal Nerves: An Ocular Biomarker for Peripheral and Cardiac Autonomic Neuropathy in Type 1 Diabetes Mellitus.

PURPOSE: We investigated the relationship between corneal subbasal nerve (SBN) plexus density, corneal sensitivity, and peripheral and cardiac autonomic neuropathy in patients with type 1 diabetes mellitus. METHODS: We recruited 53 patients with type 1 diabetes mellitus and 40 normal control participants. Corneal in vivo confocal microscopy (IVCM) and sensitivity testing were performed on one eye of each subject. Autonomic function testing was done and an overall neuropathy score obtained from a combination of a symptomatic neuropathy score, clinical assessment, biothesiometry, and nerve conduction tests. RESULTS: The corneal SBN density (P < 0.001) and corneal sensitivity (P < 0.001) were significantly lower in subjects with diabetes compared to controls. A modest negative correlation between total neuropathy score and SBN density was observed (r = -0.33, P = 0.01). A negative correlation between corneal sensitivity and expiration/inspiration component of the autonomic nerve analysis (ANS-EI) also was noted (r = -0.36, P = 0.008). Corneal SBN density was abnormal in 50% of diabetic subjects classified as "Normal" by the clinical and electrophysiological based tests of total neuropathy score. CONCLUSIONS: The correlation of corneal SBN density with total neuropathy score suggests that reduced corneal nerve density reflects peripheral neuropathy in diabetes. Corneal SBN changes precede other clinical and electrophysiology tests of neuropathy supporting a possible role for corneal IVCM and corneal sensitivity testing as surrogate markers in the assessment of diabetic peripheral and cardiac autonomic neuropathy.