Impact of obesity on pulmonary function: current understanding and knowledge gaps.

PURPOSE OF REVIEW: Obesity is an increasing world-wide public health concern. Obesity both causes respiratory symptoms and contributes to many cardiorespiratory diseases. The effects of obesity on commonly used lung function tests are reviewed. RECENT FINDINGS: The effects of obesity on lung function are attributed both to mechanical factors and to complex metabolic effects that contribute to a pro-inflammatory state. The effects of obesity on lung function correlate with BMI and correlate even better when the distribution of excess adipose tissue is taken into account, with central obesity associated with more prominent abnormalities. Obesity is associated with marked decreases in expiratory reserve volume and functional residual capacity. Total lung capacity, residual volume, and spirometry are less affected by obesity and are generally within the normal range except with severe obesity. Obesity decreases total respiratory system compliance primarily because of decreased lung compliance, with only mild effects on chest wall compliance. Obesity is associated with impaired gas transfer with decreases in oxygenation and varied but usually mild effects on diffusing capacity for carbon monoxide, while the carbon monoxide transfer coefficient is often increased. SUMMARY: Obesity has significant effects on lung function. The relative contribution of the mechanical effects of obesity and the production of inflammatory cytokines by adipose tissue on lung function needs further study.

The asthma-obesity relationship: underlying mechanisms and treatment implications.

PURPOSE OF REVIEW: Obesity is a worldwide epidemic with a prevalence that has tripled in the last two decades. Worldwide, more than 1.5 billion adults are overweight and more than 500 million obese. Obesity has been suggested to be a risk factor for the development of more difficult-to-control asthma. Although the mechanisms underlying the asthma-obesity relationship are not fully understood, several possible explanations have been put forward. These will be reviewed in this manuscript as well as the implications for the treatment of overweight and obese asthma patients. RECENT FINDINGS: Insulin resistance is a possible factor contributing to the asthma-obesity relationship and the effect is independent of other components of the metabolic syndrome such as hypertriglyceridemia, hypertension, hyperglycemia, and systemic inflammation. Obesity has important effects on airway geometry, by especially reducing expiratory reserve volume causing obese asthmatics to breathe at low lung volumes. Furthermore, obesity affects the type of inflammation in asthma and is associated with reduced inhaled corticosteroids treatment responsiveness. SUMMARY: Obesity induces the development of asthma with a difficult-to-control phenotype. Treatment targeting insulin resistance may be beneficial in obese asthma patients, especially when they have concomitant diabetes. Systemic corticosteroids should be avoided as much as possible as they are not very effective in obese asthma and associated with side-effects like diabetes, weight gain, and osteoporosis.

Cardiovascular and respiratory effects of the neoprene wetsuit in non-immersed divers.

A neoprene wetsuit is widely used to reduce thermal dispersion during diving. Recent observations have pointed out that elastic recoil of the wetsuit might have significant compressive effects, able to affect water and electrolyte homeostasis during both dry and immersed conditions. The aim of this study was to evaluate the possible cardiovascular and respiratory effects of the neoprene wetsuit in dry conditions in a sample of experienced divers. Twenty-four (24) healthy divers were evaluated by Doppler-echocardiography and by spirometry in basal conditions and while wearing a full neoprene wetsuit. During wetsuit conditions, we observed a significant decrease in heart rate (-5%; p ⟨ 0.05) and cardiac output (-12%; p ⟨ 0.05), and a significant increase in total peripheral resistances (15%; p ⟨ 0.05). Moreover, a significant reduction of right ventricular early diastolic filling was observed (-15%; p ⟨ 0.05). As concerns pulmonary function, a significant reduction of vital capacity (-2%; p ⟨ 0.001) and expiratory reserve volume (-25%; p ⟨ 0.001), and a significant increase of inspiratory capacity (9%; p ⟨ 0.001) and tidal volume (25%; p ⟨ 0.05) were observed. These data support the hypothesis that neoprene elastic recoil, possibly due to a compression exerted on chest, might affect systemic circulation (decreasing cardiac output and impairing right ventricular filling) and respiratory function.

What can impulse oscillometry and pulmonary function testing tell us about obstructive sleep apnea: a case-control observational study?

PURPOSE: This study aims to determine whether functional residual capacity (FRC) in obese patients with obstructive sleep apnea (OSA) decreases more than in patients without OSA because of decreased outward recoil from chest wall mass loading as well as increased lung inward recoil. METHODS: Subjects who were overweight and obese to various degrees with normal spirometric values underwent overnight polysomnography to determine the presence or absence of OSA and were labeled as cases or controls. Lung volume and respiratory mechanical properties were measured by plethysmograph and impulse oscillometry, respectively. RESULTS: A total of 76 men and 31 women were diagnosed with OSA (cases); 64 men and 33 women without OSA were confirmed as controls. Expiratory reserve volume and FRC were significantly decreased in cases compared with controls. Respiratory impedance and resistance at 5 Hz were significantly higher in cases than in controls, although reactance at low frequencies was significantly lower in cases than in controls. Reactance at 5 Hz (Xrs5) was found to be independently highly correlated with the severity of OSA as defined by the Apnea-Hypopnea Index and was significantly correlated with FRC. CONCLUSIONS: FRC is significantly decreased in overweight or obese patients with OSA compared with those without OSA, which may be attributed to an increase in lung elastic recoil. The stronger correlation between Xrs5 and OSA severity might indicate upper airway stenosis, and abnormally increased lung elastic recoil may contribute to OSA.

OPTIMUM LEVEL OF POSITIVE END-EXPIRATORY PRESSURE IN ACUTE RESPIRATORY DISTRESS SYNDROME CAUSED BY INFLUENZA A(H1NI)PDM09: BALANCE BETWEEN MAXIMAL END-EXPIRATORY VOLUME AND MINIMAL ALVEOLAR OVERDISTENSION.

THE AIM: to determine optimum level ofpositive end-expiratory pressure (PEEP) according to balance between maxi- mal end-expiratory lung volume (EEL V)(more than predicted) and minimal decrease in exhaled carbon dioxide volume (VCO) and then to develop the algorithm of gas exchange correction based on prognostic values of EEL K; alveolar recruitability, PA/FiO2, static compliance (C,,,) and VCO2. MATERIALS AND METHODS: 27 mechanically ventilatedpatients with acute respiratory distress syndrome (ARDS) caused by influenza A (HINJ)pdm09 in Moscow Municipal Clinics ICU's from January to March 2016 were included in the trial. At the beginning of the study patients had the following characteristic: duration offlu symptoms 5 (3-10) days, p.0/FiO2 120 (70-50) mmHg. SOFA 7 (5-9), body mass index 30.1 (26.4-33.8) kg/m², static compliance of respiratory system 35 (30-40) ml/mbar: Under sedation and paralysis we measured EELV, C VCO and end-tidal carbon dioxide concentration (EtCO) (for CO2 measurements we fixed short-term values after 2 min after PEEP level change) at PEEP 8, 11,13,15,18, 20 mbar consequently, and incase of good recruitability, at 22 and 24 mbar. After analyses of obtained data we determined PEEP value in which increase in EELV was maximal (more than predicted) and depression of VCO2 was less than 20%, change in mean blood pressure and heart rate were both less than 20% (measured at PEEP 8 mbar). After that we set thus determined level of PEEP and didn't change it for 5 days. RESULTS: Comparision of predicted and measured EELV revealed two typical points of alveloar recruiment: the first at PEEP 11-15 mbar, the second at PEEP 20-22 mbar. EELV measured at PEEP 18 mbar appeared to be higher than predicted at PEEP 8 mbar by 400 ml (approx.), which was the sign of alveolar recruitment-1536 (1020-1845) ml vs 1955 (1360-2320) ml, p=0,001, Friedman test). we didn't found significant changes of VCO2 when increased PEEP in the range from 8 to 15 mbar (p>0.05, Friedman test). PEEP increase from 15 to 18 mbar and more lead to decrease in VCO2 (from 212 (171-256) ml/min to 200 (153-227) ml/min, p<0,0001, Friedman test, which was the sign of overdistension. Next decrease of VCO2 was observed at PEEP increase from 22 to 24 mbar (from 203 (174-251 ml/min) to 185 (182-257) ml/min, p=0.0025, Friedman test). Adjusted PEEP value according to balance between recruitment and overdistension was higher than the one initially set (16(15-18) mbar vs 12(7-15) mbar, p <0.0001). We observed increase of SpO2 from 93 (87-96) to 97(95-100)% (p<0.0001 followed by decrease in inspiratory oxygen fraction from 60(40-80) to 50(40-60)%(p<0.0001). Low EELV VCO2 and VCO2/EtCO2 at PEEP 8 mbar has low predictive value for death (AUROC 0,547, 0706 and 0.596, respectively).Absolute EELV value at PEEP 18 and 20 mbar were poor predictors of mortality (AUROC 0.61 and 0.65 respectively) Alveolar recruit ability was measured by subtraction of EELV at PEEP 20 and at PEEP II mbar - value below 575 ml was a good predictor of death (sensitivity 75%, specificity 88%, AUROC 0.81). Lowering of VCO2 at PEEP 20 mbar to less than 207 ml/min was a marker of alveolar overdistension and associated with poor prognosis (sensitivity 83%, specificity 88%, AUROC 0,89). C has poor predictive value at PEEP 8 and 20 mbar (AUROC 0,58 and 0,74 respectively. Conclusion: PEEP adjustment in ARDS due to influenza A (H1N1) pdm09 in accordance with balance between recruitment and overdistension (based on EELV and VCO measurements) can improve gas exchange, probably, not leading to right ventricular failure. This value of "balanced" PEEP is in the range between 15 and 18 mbar: Low lung recruitabiilty is associated with poor prognosis. Measurements of EELV and VCO2 at PEEP 8 and 20 mbar can be used to make a decision on whether to keep "high" PEEP level or switch to extracorporeal membrane oxygenation in patient with ARDS due to influenza A (N1H1).

Endurance exercise performance in acute hypoxia is influenced by expiratory flow limitation.

PURPOSE: We sought to determine if expiratory flow limitation influences intensive aerobic exercise performance in mild hypoxia. METHODS: Fourteen trained male cyclists were separated into flow-limited (FL, n = 7) and non-FL (n = 7) groups based on the extent of expiratory flow limitation exhibited during maximal exercise in normoxia. Participants performed two self-paced 5-km cycling time trials, one in normoxic (F IO2 = 0.21) and one in mild hypoxic (F IO2 = 0.17) conditions in a randomized, balanced order with the subjects blinded to composition of the inspirate. Percent change from normoxia to hypoxia in average power output (%ΔP TT) and time to completion (%ΔT TT) were used to assess performance. RESULTS: Hypoxia resulted in a significant decline in estimated arterial O2 saturation and decrements in performance in both groups, although FL had a significantly smaller %ΔP TT (-4.0 ± 0.5 vs. -9.0 ± 1.8 %) and %ΔT TT (1.3 ± 0.3 vs. 3.7 ± 0.9 %) compared to non-FL. At the 5th km of the time trial, minute ventilation did not change from normoxia to hypoxia in FL (3.4 ± 3.1 %) or non-FL (2.3 ± 3.7 %), but only the non-FL reported a significantly increased dyspnea rating in hypoxia compared to normoxia (~9 %). Non-FL athletes did not utilize their ventilatory reserve to defend arterial oxygen saturation in hypoxia, which may have been due to an increased measure of dyspnea in the hypoxic trial. CONCLUSION: FL athletes experience less hypoxia-related aerobic exercise performance impairment as compared to non-FL athletes, despite having less ventilatory reserve.

Does locomotor training improve pulmonary function in patients with spinal cord injury?

OBJECTIVES: The aim of this study was to compare the effects of a locomotor training (LT) combined rehabilitation program with a rehabilitation-only program on pulmonary function in spinal cord injury (SCI) patients by investigating spirometric analyses of the patients. SETTING: Rehabilitation center in Ankara, Turkey. METHODS: Fifty-two patients (40 male, 12 female) with SCI enrolled in the study. The subjects were divided into two groups: the first group (group A) received both LT and a rehabilitation program and the second group (group B) received only the rehabilitation program for 4 weeks. The LT program was prescribed as three 30-min sessions per week. Pulmonary function was evaluated spirometrically in both groups before and after the rehabilitation program. RESULTS: The spirometric values of the SCI patients, including forced vital capacity, forced expiratory volume in 1 second, forced expiratory flow rate and vital capacity (VC) and VC%, increased significantly with LT in the first group (all P<0.05). Maximum voluntary ventilation values increased significantly in both groups (both P<0.05). CONCLUSION: These findings suggest that LT is effective for improving pulmonary function in SCI patients. We also highlight the useful effects of LT, which are likely the result of erect posture, gait and neuroplastic changes that prevent potential complications in SCI patients.

Lung recruitment and endotracheal suction in ventilated preterm infants measured with electrical impedance tomography.

AIMS: Although suctioning is a standard airway maintenance procedure, there are significant associated risks, such as loss of lung volume due to high negative suction pressures. This study aims to assess the extent and duration of change in end-expiratory level (EEL) resulting from endotracheal tube (ETT) suction and to examine the relationship between EEL and regional lung ventilation in ventilated preterm infants with respiratory distress syndrome. METHODS: A prospective observational clinical study of the effect of ETT suction on 20 non-muscle-relaxed preterm infants with respiratory distress syndrome (RDS) on conventional mechanical ventilation was conducted in a neonatal intensive care unit. Ventilation distribution was measured with regional impedance amplitudes and EEL using electrical impedance tomography. RESULTS: ETT suction resulted in a significant increase in EEL post-suction (P < 0.01). Regionally, anterior EEL decreased and posterior EEL increased post-suction, suggesting heterogeneity. Tidal volume was significantly lower in volume-guarantee ventilation compared with pressure-controlled ventilation (P = 0.04). CONCLUSIONS: ETT suction in non-muscle-relaxed and ventilated preterm infants with RDS results in significant lung volume increase that is maintained for at least 90 min. Regional differences in distribution of ventilation with ETT suction suggest that the behaviour of the lung is heterogeneous in nature.

Garment fit and protection from sustained +Gz acceleration with 'full-coverage' anti-G trousers.

INTRODUCTION: Garment fit may influence the effectiveness with which Full-Coverage Anti-G Trousers (FCAGT) transmit pressure to the skin surface, and hence provide protection from sustained +Gz acceleration. A search of the available literature, however, did not reveal any prior work quantifying this effect. METHODS: Three related studies were performed. In Study I, using a mannequin, garment-to-surface pressure transmission ratios were measured at various locations under normally fitted (NF) and loosely fitted (LF) FCAGT. In Study II, garment pressure-volume ratios and lung volumes were measured at +1 Gz in six men wearing FCAGT in three conditions: NF, LF, or NF with inflatable socks at 13 kPa differential pressure (NF+SOCKS). In Study III, relaxed +Gz tolerance (RGT) and ratings of perceived exertion (RPE) at +7, +8, and +9 Gz were measured in eight men wearing FCAGT in four experimental conditions: NF; LF; abdomen LF, legs NF; or abdomen NF, legs LF. RESULTS: LF did not affect pressure transmission over the lower limbs or lower abdomen, but transmission over the upper abdomen was significantly compromised. Lung volumes were reduced with FCAGT inflation, but LF was associated with greater expiratory reserve volumes and increased FCAGT volume. Under +Gz acceleration, LF over the abdomen (with or without lower limb LF) decreased RGT and increased RPE, but not with lower limb LF when abdominal fit was normal. DISCUSSION: Care should be taken to achieve and maintain a snug FCAGT fit, especially of the abdominal portion of the FCAGT, to ensure optimal anti-G protection during sustained acceleration.

Intragastric balloon for the treatment of obesity: evaluation of pulmonary function over a 3-month period.

BACKGROUND: Obesity has become a global epidemic in the 21st century, and the placement of an intragastric balloon (IB) is a therapeutic modality used to treat it. Our objectives for this study were to evaluate changes in lung function resulting from IB use and to correlate the pattern of body fat distribution with changes in lung function. METHODS: This was an interventional study with 30 overweight and obese patients with metabolic syndrome. All of the subjects underwent anthropometric measurements, assessment of their body fat distribution pattern by dual-energy X-ray absorptiometry, and pulmonary function testing before implantation of the IB. RESULTS: During the initial evaluations, the main pulmonary function abnormalities observed were decreased expiratory reserve volume (ERV), decreased total lung capacity (TLC), and increased diffusing capacity of carbon monoxide (DL(CO)), which occurred in 56.7, 40, and 23.3 % of patients, respectively. We observed a statistically significant positive correlation between the DL(CO) and the percentage of trunk fat mass (ρ = 0.42; p < 0.01). Three months after placement of the IB, there was a significant reduction in the body mass index (p < 0.0001) and the maximal inspiratory pressure (p < 0.009). We also observed a significant increase in the forced vital capacity (p < 0.0001), TLC (p < 0.001), and ERV (p < 0.0001). CONCLUSIONS: Weight loss as a result of IB causes increased static lung volumes and decreased inspiratory muscle strength. Additionally, being overweight and obese is related to increased DL(CO), especially in individuals with truncal obesity.

Regional ventilation distribution in the first 6 months of life.

Electrical impedance tomography (EIT) has been used to study regional ventilation distribution in neonatal and paediatric lung disease; however, little information has been obtained in healthy newborns and infants. Data on regional ventilation distribution and regional filling characteristics were obtained using EIT in the neonatal period, at 3 and 6 months of age, in spontaneously breathing infants during non-rapid eye movement sleep. Regional ventilation distribution was described using regional end-expiratory and end-inspiratory impedance amplitudes, and geometric centre of ventilation. Regional filling characteristics were described with the phase lag or lead of the regional impedance change in comparison to global impedance change. 32 infants were measured in the supine position. Regional impedance amplitudes increased with age but regional ventilation distribution remained unchanged in all infants at any age, with the dependent (posterior) lung always better ventilated. Regional filling characteristics showed that the dependent lung filled during inspiration before the nondependent lung during all follow-up measurements. Regional ventilation distribution and regional filling characteristics remained unchanged over the first 6 months of life, and the results obtained on regional ventilation distribution are very similar to those in adult subjects.

Generalized anxiety disorder is associated with reduced lung function in the Vietnam Experience Study.

BACKGROUND: There is no clear consensus in the few studies to have explored the relationship between major mental health disorders and lung function. The present study examined the cross-sectional associations of generalized anxiety disorder (GAD) and major depressive disorder (MDD) with lung function in a large study of male US veterans. METHODS: Participants (N = 4256) were drawn from the Vietnam Experience Study. From military files, telephone interviews, and a medical examination, anthropometric, sociodemographic, and health data were collected. One-year prevalence of GAD and MDD was determined using DSM-III criteria. Forced expiratory volume in 1 second was measured by spirometry. RESULTS: In models that adjusted for age and height, both GAD (p < .001) and MDD (p = .004) were associated with lower forced expiratory volume in 1 second. In models additionally adjusting for weight, place of service, ethnicity, marriage, smoking, alcohol consumption, income, education, and major illness, GAD was still associated with poorer lung function (p = .01), whereas MDD was not (p = .18). CONCLUSIONS: Depression has very much been the focus of studies on mental health and physical health status. The current findings suggest that future research should perhaps pay equal attention to GAD.

End-expiratory lung volume and ventilation distribution with different continuous positive airway pressure systems in volunteers.

BACKGROUND: Continuous positive airway pressure (CPAP) has been shown to improve oxygenation and a number of different CPAP systems are available. The aim of this study was to assess lung volume and ventilation distribution using three different CPAP techniques. METHODS: A high-flow CPAP system (HF-CPAP), an ejector-driven system (E-CPAP) and CPAP using a Servo 300 ventilator (V-CPAP) were randomly applied at 0, 5 and 10 cmH2O in 14 volunteers. End-expiratory lung volume (EELV) was measured by N2 dilution at baseline; changes in EELV and tidal volume distribution were assessed by electric impedance tomography. RESULTS: Higher end-expiratory and mean airway pressures were found using the E-CPAP vs. the HF-CPAP and the V-CPAP system (P<0.01). EELV increased markedly from baseline, 0 cmH2O, with increased CPAP levels: 1110±380, 1620±520 and 1130±350 ml for HF-, E- and V-CPAP, respectively, at 10 cmH2O. A larger fraction of the increase in EELV occurred for all systems in ventral compared with dorsal regions (P<0.01). In contrast, tidal ventilation was increasingly directed toward dorsal regions with increasing CPAP levels (P<0.01). The increase in EELV as well as the tidal volume redistribution were more pronounced with the E-CPAP system as compared with both the HF-CPAP and the V-CPAP systems (P<0.05) at 10 cmH2O. CONCLUSION: EELV increased more in ventral regions with increasing CPAP levels, independent of systems, leading to a redistribution of tidal ventilation toward dorsal regions. Different CPAP systems resulted in different airway pressure profiles, which may result in different lung volume expansion and tidal volume distribution.

Prolonged slow expiration technique in infants: effects on tidal volume, peak expiratory flow, and expiratory reserve volume.

BACKGROUND: Prolonged slow expiration (PSE) is a physiotherapy technique often applied in infants to reduce pulmonary obstruction and clear secretions, but there have been few studies of PSE's effects on the respiratory system. OBJECTIVE: To describe PSE's effects on respiratory mechanics in infants. METHODS: We conducted a cross-sectional study with 18 infants who had histories of recurrent wheezing. The infants were sedated for lung-function testing, which was followed by PSE. The PSE consisted of 3 sequences of prolonged manual thoraco-abdominal compressions during the expiratory phase. We measured peak expiratory flow (PEF), tidal volume (V(T)), and the frequency of sighs during and immediately after PSE. We described the exhaled volume during PSE as a fraction of expiratory reserve volume (%ERV). We quantified ERV with the raised-volume rapid-thoracic-compression technique. RESULTS: The cohort's mean age was 32.2 weeks, and they had an average of 4.8 previous wheezing episodes. During PSE there was significant V(T) reduction (80 ± 17 mL vs 49 ± 11 mL, P < .001), no significant change in PEF (149 ± 32 mL/s vs 150 ± 32 mL/s, P = .54), and more frequent sighs (40% vs 5%, P = .03), compared to immediately after PSE. The exhaled volume increased in each PSE sequence (32 ± 18% of ERV, 41 ± 24% of ERV, and 53 ± 20% of ERV, P = .03). CONCLUSIONS: It was possible to confirm and quantify that PSE deflates the lung to ERV. PSE caused no changes in PEF, induced sigh breaths, and decreased V(T), which is probably the main mechanical feature for mucus clearance.

Intraoperative recruitment maneuver reverses detrimental pneumoperitoneum-induced respiratory effects in healthy weight and obese patients undergoing laparoscopy.

BACKGROUND: Pulmonary function is impaired during pneumoperitoneum mainly as a result of atelectasis formation. We studied the effects of 10 cm H2O of positive end-expiratory pressure (PEEP) and PEEP followed by a recruitment maneuver (PEEP+RM) on end-expiratory lung volume (EELV), oxygenation and respiratory mechanics in patients undergoing laparoscopic surgery. METHODS: Sixty consecutive adult patients (30 obese, 30 healthy weight) in reverse Trendelenburg position were prospectively studied. EELV, static elastance of the respiratory system, dead space, and gas exchange were measured before and after pneumoperitoneum insufflation with zero end-expiratory pressure, with PEEP alone, and with PEEP+RM. Results are presented as mean ± SD. RESULTS: Pneumoperitoneum reduced EELV (healthy weight, 1195 ± 405 vs. 1724 ± 774 ml; obese, 751 ± 258 vs. 886 ± 284 ml) and worsened static elastance and dead space in both groups (in all P < 0.01 vs. zero-end expiratory pressure before pneumoperitoneum) whereas oxygenation was unaffected. PEEP increased EELV (healthy weight, 570 ml, P < 0.01; obese, 364 ml, P < 0.01) with no effect on oxygenation. Compared with PEEP alone, EELV and static elastance were further improved after RM in both groups (P < 0.05), as was oxygenation (P < 0.01). In all patients, RM-induced change in EELV was 16% (P = 0.04). These improvements were maintained 30 min after RM. RM-induced changes in EELV correlated with change in oxygenation (r = 0.42, P < 0.01). CONCLUSION: RM combined with 10 cm H2O of PEEP improved EELV, respiratory mechanics, and oxygenation during pneumoperitoneum whereas PEEP alone did not.

Expiratory volumetric MDCT evaluation of air trapping in pediatric patients with and without tracheomalacia.

OBJECTIVE: The purpose of this study was to use paired inspiratory-expiratory volumetric MDCT to compare the frequency, severity, and pattern of air trapping in pediatric patients with tracheomalacia with the findings in children without tracheomalacia. MATERIALS AND METHODS: The study group consisted of 15 consecutively registered pediatric patients (younger than 18 years) who had tracheomalacia, defined as 50% or greater reduction in tracheal cross-sectional luminal area between end inspiration and end expiration, diagnosed with MDCT and confirmed with bronchoscopy. The comparison group consisted of 15 consecutively registered pediatric patients without evidence of tracheomalacia at MDCT and bronchoscopy. Two blinded pediatric radiologists working in consensus interpreted the randomly viewed end-expiratory thin-section CT images of both groups of children for the presence, severity, and pattern of air trapping at three anatomic levels (upper, middle, and lower lung zones). The severity of air trapping was graded visually on a 5-point scale. The total air trapping scores, obtained by summing the values for the three anatomic levels for the study and comparison groups, were compared by Wilcoxon's rank sum test. The pattern of air trapping was categorized as lobular, segmental, lobar, diffuse, or mixed, and the patterns in the two study groups were compared by Pearson's chi-square test. RESULTS: The study cohort with tracheomalacia consisted of 15 patients (10 boys, five girls; mean age, 2.4 +/- 2.8 years; range, 1 month-11.8 years). The comparison group without tracheomalacia consisted of 15 patients (nine boys, six girls; mean age, 2.7 +/- 2.4 years; range, 1 month-8.1 years). Air trapping was identified in all 15 patients with tracheomalacia (median score, 5.0; range, 3-11) and in 10 of 15 children (67%) in the comparison group (median score, 3.0; range, 1-4). The median total air trapping score was significantly higher in the study cohort than in the comparison group (p = 0.002), but there were no significant differences in the air trapping patterns between the study groups (p = 0.53). CONCLUSION: Pediatric patients with tracheomalacia have a higher frequency and greater severity of air trapping than do children without tracheomalacia.

Ventilatory support during whole-body row training improves oxygen uptake efficiency in patients with high-level spinal cord injury: A pilot study.

High-level spinal cord injury (SCI) is characterized by profound respiratory compromise. One consequence is a limitation of whole-body exercise-based rehabilitation, reducing its cardioprotective effect. We investigated the use of ventilatory support during training on cardiorespiratory response to exercise. Nine subjects with high-level SCI (T3-C4) were included in this double-blind sham-controlled study. All had training adaptations plateauing for more than 6 months before enrolling in the study. After performing baseline assessment, participants were randomly assigned to continue training with non-invasive ventilation (NIV: n = 6: IPAP = 20 ± 2, EPAP: 3 cmH2O) or sham (n = 3: IPAP = 5, EPAP: 3 cmH2O) for 3 months and performed again maximal exercise tests. We compared the oxygen uptake efficiency slope (OUES, the rate of increases in VO2 in relation to increasing VE) before and after training. Training with NIV increased OUES both compared to baseline (4.1 ± 1.1 vs. 3.4 ± 1.0, i.e. +20 ± 12%, p < 0.05) and Sham (p = 0.01), representing an increase in ability to uptake oxygen for a given ventilation. This result was sustained without NIV during the test, suggesting improved cardiopulmonary reserve. Best responders were the youngest whose characteristics were very similar to sham participants. In addition, NIV tended to increase weekly rowing distance by 24% (p = 0.09, versus 10% in sham). Our results are very suggestive of a positive effect of ventilatory support during whole-body exercise in high-level SCI. Training adaptations found are of great importance since this sub-population of patients have the greatest need for exercise-based cardio-protection.

Increasing ventilator surge capacity in COVID 19 pandemic: design, manufacture and in vitro-in vivo testing in anaesthetized healthy pigs of a rapid prototyped mechanical ventilator.

OBJECTIVE: The advent of new technologies has made it possible to explore alternative ventilator manufacturing to meet the worldwide shortfall for mechanical ventilators especially in pandemics. We describe a method using rapid prototyping technologies to create an electro-mechanical ventilator in a cost effective, timely manner and provide results of testing using an in vitro-in vivo testing model. RESULTS: Rapid prototyping technologies (3D printing and 2D cutting) were used to create a modular ventilator. The artificial manual breathing unit (AMBU) bag connected to wall oxygen source using a flow meter was used as air reservoir. Controlled variables include respiratory rate, tidal volume and inspiratory: expiratory (I:E) ratio. In vitro testing and In vivo testing in the pig model demonstrated comparable mechanical efficiency of the test ventilator to that of standard ventilator but showed the material limits of 3D printed gears. Improved gear design resulted in better ventilator durability whilst reducing manufacturing time (< 2-h). The entire cost of manufacture of ventilator was estimated at 300 Australian dollars. A cost-effective novel rapid prototyped ventilator for use in patients with respiratory failure was developed in < 2-h and was effective in anesthetized, healthy pig model.

Airway dilator muscle activity and lung volume during stable breathing in obstructive sleep apnea.

STUDY OBJECTIVES: Many patients with obstructive sleep apnea (OSA) have spontaneous periods of stable flow limited breathing during sleep without respiratory events or arousals. In addition, OSA is often more severe during REM than NREM and more severe during stage 2 than slow wave sleep (SWS). The physiological mechanisms for these observations are unknown. Thus we aimed to determine whether the activity of two upper airway dilator muscles (genioglossus and tensor palatini) or end-expiratory lung volume (EELV) differ between (1) spontaneously occurring stable and cyclical breathing and (2) different sleep stages in OSA. DESIGN: Physiologic observation. SETTING: Sleep physiology laboratory. STUDY PARTICIPANTS: 15 OSA patients with documented periods of spontaneous stable breathing. INTERVENTION: Subjects were instrumented with intramuscular electrodes for genioglossus and tensor palatini electromyograms (EMG(GG) and EMG(TP)), chest and abdominal magnetometers (EELV measurement), an epiglottic pressure catheter (respiratory effort), and a mask and pneumotachograph (airflow/ventilation). Patients slept supine overnight without CPAP. MEASUREMENTS AND RESULTS: Peak and Tonic EMG(GG) were significantly lower during cyclical (85.4 +/- 2.7 and 94.6 +/- 4.7 % total activity) than stable breathing (109.4 +/- 0.4 and 103 +/- 0.8% total activity, respectively). During respiratory events in REM, tonic EMG(GG) activity was lower than during respiratory events in stage 2 (71.9 +/- 5.1 and 119.6 +/- 5.6% total activity). EMG(GG) did not differ between stable stage 2 and stable SWS (98.9 +/- 3.2 versus 109.7 +/- 4.4% total activity), nor did EMG(TP) or EELV differ in any breathing condition/sleep stage. CONCLUSIONS: Increased genioglossus muscle tone is associated with spontaneous periods of stable flow limited breathing in the OSA subjects studied. Reductions in genioglossus activity during REM may explain the higher severity of OSA in that stage. Increased lung volume and tensor palatini activity do not appear to be major mechanisms enabling spontaneous stable flow limited breathing periods.

Comparison of energy expenditure, economy, and pedometer counts between normal weight and overweight or obese women during a walking and jogging activity.

This study compared energy expenditure (EE), economy of movement, and pedometer counts between normal weight and overweight or obese women during a treadmill walking and jogging activity. Participants were 13 normal weight (BMI 22.2 +/- 2.0 kg m(-2)) and 13 overweight or obese (BMI 27.2 +/- 2.1 kg m(-2)) women and all were non-smokers, not regularly active, and able to run 1.609 km continuously at 2.23 m s(-1). Each participant reported to the laboratory on three separate days within a 1-week period. During the first visit, tests for resting metabolic rate via indirect calorimetry, anthropometric measures, and VO(2)max were completed. On the subsequent two visits, participants were randomized to perform either a 1.609-km walk at 1.34 m s(-1) or a 1.609-km jog at 2.23 m s(-1). During each physical activity trial, all participants wore a pedometer to assess steps taken. EE during the 1.609-km walk was 280 +/- 29 kJ for the normal weight and 356 +/- 42 kJ for the overweight/obese women and during the 1.609-km jog was 393 +/- 46 kJ for the normal weight and 490 +/- 59 kJ for the overweight/obese women. In both trials, EE was statistically greater in the overweight/obese women. Economy of movement was not statistically different between the normal weight and overweight/obese women during the walk or jog. In both groups, pedometer counts were lower during the jog than the walk (P < 0.05). These data indicate significant differences in EE between normal weight and overweight/obese women during both a walking and jogging activity.