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.

Exertional dyspnea and operating lung volumes in asthma.

Dyspnea has been reported to be a main contributor to exercise avoidance in asthma. While traditional markers of ventilation do not explain the heightened dyspnea during exercise in patients with asthma, this study proposed that exertional dyspnea in asthma was due to high-operating lung volumes, which may be improved with a short-acting ß2-agonist. On two separate days, 16 patients with asthma and 16 controls completed a lung function test and incremental exercise tests to exhaustion. On one of the days (order randomized), 400 µg salbutamol was administered before exercise. Inspiratory capacity (IC), inspiratory reserve volume (IRV), and dyspnea (modified Borg scale) were evaluated throughout exercise. Compared with controls, patients with asthma reported greater dyspnea at the same absolute submaximal workloads. Furthermore, patients with asthma demonstrated altered breathing responses to exercise, characterized by reduced IC and IRV throughout exercise compared with controls. The reduced IRV was associated with increased dyspnea in patients with asthma. Salbutamol did not affect dyspnea or operating lung volumes in either group. The increased perception of dyspnea during incremental exercise in patients with asthma appears to be secondary to a reduction in IRV, which is unaffected by an inhaled ß2-agonist. NEW & NOTEWORTHY Increased exertional dyspnea in asthma appears to be due to high operating lung volumes and is not affected by salbutamol.

Treatment effect of idebenone on inspiratory function in patients with Duchenne muscular dystrophy.

Assessment of dynamic inspiratory function may provide valuable information about the degree and progression of pulmonary involvement in patients with Duchenne muscular dystrophy (DMD). The aims of this study were to characterize inspiratory function and to assess the efficacy of idebenone on this pulmonary function outcome in a large and well-characterized cohort of 10-18 year-old DMD patients not taking glucocorticoid steroids (GCs) enrolled in the phase 3 randomized controlled DELOS trial. We evaluated the effect of idebenone on the highest flow generated during an inspiratory FVC maneuver (maximum inspiratory flow; V'I,max(FVC)) and the ratio between the largest inspiratory flow during tidal breathing (tidal inspiratory flow; V'I,max(t)) and the V'I,max(FVC). The fraction of the maximum flow that is not used during tidal breathing has been termed inspiratory flow reserve (IFR). DMD patients in both treatment groups of DELOS (idebenone, n = 31; placebo: n = 33) had comparable and abnormally low V'I,max(FVC) at baseline. During the study period, V'I,max(FVC) further declined by -0.29 L/sec in patients on placebo (95%CI: -0.51, -0.08; P = 0.008 at week 52), whereas it remained stable in patients on idebenone (change from baseline to week 52: 0.01 L/sec; 95%CI: -0.22, 0.24; P = 0.950). The between-group difference favoring idebenone was 0.27 L/sec (P = 0.043) at week 26 and 0.30 L/sec (P = 0.061) at week 52. In addition, during the study period, IFR improved by 2.8% in patients receiving idebenone and worsened by -3.0% among patients on placebo (between-group difference 5.8% at week 52; P = 0.040). Although the clinical interpretation of these data is currently limited due to the scarcity of routine clinical practice experience with dynamic inspiratory function outcomes in DMD, these findings from a randomized controlled study nevertheless suggest that idebenone preserved inspiratory muscle function as assessed by V'I,max(FVC) and IFR in patients with DMD. Pediatr Pulmonol. 2017;52:508-515. © 2016 The Authors. Pediatric Pulmonology Published by Wiley Periodicals, Inc.

Abdominal Muscle Activity during Mechanical Ventilation Increases Lung Injury in Severe Acute Respiratory Distress Syndrome.

OBJECTIVE: It has proved that muscle paralysis was more protective for injured lung in severe acute respiratory distress syndrome (ARDS), but the precise mechanism is not clear. The purpose of this study was to test the hypothesis that abdominal muscle activity during mechanically ventilation increases lung injury in severe ARDS. METHODS: Eighteen male Beagles were studied under mechanical ventilation with anesthesia. Severe ARDS was induced by repetitive oleic acid infusion. After lung injury, Beagles were randomly assigned into spontaneous breathing group (BIPAPSB) and abdominal muscle paralysis group (BIPAPAP). All groups were ventilated with BIPAP model for 8h, and the high pressure titrated to reached a tidal volume of 6ml/kg, the low pressure was set at 10 cmH2O, with I:E ratio 1:1, and respiratory rate adjusted to a PaCO2 of 35-60 mmHg. Six Beagles without ventilator support comprised the control group. Respiratory variables, end-expiratory volume (EELV) and gas exchange were assessed during mechanical ventilation. The levels of Interleukin (IL)-6, IL-8 in lung tissue and plasma were measured by qRT-PCR and ELISA respectively. Lung injury scores were determined at end of the experiment. RESULTS: For the comparable ventilator setting, as compared with BIPAPSB group, the BIPAPAP group presented higher EELV (427±47 vs. 366±38 ml) and oxygenation index (293±36 vs. 226±31 mmHg), lower levels of IL-6(216.6±48.0 vs. 297.5±71.2 pg/ml) and IL-8(246.8±78.2 vs. 357.5±69.3 pg/ml) in plasma, and lower express levels of IL-6 mRNA (15.0±3.8 vs. 21.2±3.7) and IL-8 mRNA (18.9±6.8 vs. 29.5±7.9) in lung tissues. In addition, less lung histopathology injury were revealed in the BIPAPAP group (22.5±2.0 vs. 25.2±2.1). CONCLUSION: Abdominal muscle activity during mechanically ventilation is one of the injurious factors in severe ARDS, so abdominal muscle paralysis might be an effective strategy to minimize ventilator-induce lung injury.

APPLICATION OF LAPAROSCOPIC LIFTING SYSTEMS IN PATIENTS WITH HIGH CARDIORESPIRATORY RISK.

Intra-abdominal hypertension during laparoscopic operations increased the risk of complications from cardiovascular and respiratory systems. An application of laparolifting systems allowed doctors to avoid changes of pneumoperitoneum, although it was associated with technical difficulties in operation performance. The authors used a test in order to determine cardiorespiratory reserve in preoperative period. The reserve was characterized by decrease of stroke volume of the heart against the background of intra-abdominal hypertension. There was noted a reliable increase of complication rate in these patients in case of application of standard laparoscopic operation compared with operation using lifting systems.

Work of Breathing into Snow in the Presence versus Absence of an Artificial Air Pocket Affects Hypoxia and Hypercapnia of a Victim Covered with Avalanche Snow: A Randomized Double Blind Crossover Study.

Presence of an air pocket and its size play an important role in survival of victims buried in the avalanche snow. Even small air pockets facilitate breathing. We hypothesize that the size of the air pocket significantly affects the airflow resistance and work of breathing. The aims of the study are (1) to investigate the effect of the presence of an air pocket on gas exchange and work of breathing in subjects breathing into the simulated avalanche snow and (2) to test whether it is possible to breathe with no air pocket. The prospective interventional double-blinded study involved 12 male volunteers, from which 10 completed the whole protocol. Each volunteer underwent two phases of the experiment in a random order: phase "AP"--breathing into the snow with a one-liter air pocket, and phase "NP"--breathing into the snow with no air pocket. Physiological parameters, fractions of oxygen and carbon dioxide in the airways and work of breathing expressed as pressure-time product were recorded continuously. The main finding of the study is that it is possible to breath in the avalanche snow even with no air pocket (0 L volume), but breathing under this condition is associated with significantly increased work of breathing. The significant differences were initially observed for end-tidal values of the respiratory gases (EtO2 and EtCO2) and peripheral oxygen saturation (SpO2) between AP and NP phases, whereas significant differences in inspiratory fractions occurred much later (for FIO2) or never (for FICO2). The limiting factor in no air pocket conditions is excessive increase in work of breathing that induces increase in metabolism accompanied by higher oxygen consumption and carbon dioxide production. The presence of even a small air pocket reduces significantly the work of breathing.

Correlated variability in the breathing pattern and end-expiratory lung volumes in conscious humans.

In order to characterize the variability and correlation properties of spontaneous breathing in humans, the breathing pattern of 16 seated healthy subjects was studied during 40 min of quiet breathing using opto-electronic plethysmography, a contactless technology that measures total and compartmental chest wall volumes without interfering with the subjects breathing. From these signals, tidal volume (VT), respiratory time (TTOT) and the other breathing pattern parameters were computed breath-by-breath together with the end-expiratory total and compartmental (pulmonary rib cage and abdomen) chest wall volume changes. The correlation properties of these variables were quantified by detrended fluctuation analysis, computing the scaling exponenta. VT, TTOT and the other breathing pattern variables showed α values between 0.60 (for minute ventilation) to 0.71 (for respiratory rate), all significantly lower than the ones obtained for end-expiratory volumes, that ranged between 1.05 (for rib cage) and 1.13 (for abdomen) with no significant differences between compartments. The much stronger long-range correlations of the end expiratory volumes were interpreted by a neuromechanical network model consisting of five neuron groups in the brain respiratory center coupled with the mechanical properties of the respiratory system modeled as a simple Kelvin body. The model-based α for VT is 0.57, similar to the experimental data. While the α for TTOT was slightly lower than the experimental values, the model correctly predicted α for end-expiratory lung volumes (1.045). In conclusion, we propose that the correlations in the timing and amplitude of the physiological variables originate from the brain with the exception of end-expiratory lung volume, which shows the strongest correlations largely due to the contribution of the viscoelastic properties of the tissues. This cycle-by-cycle variability may have a significant impact on the functioning of adherent cells in the respiratory system.

Differences in the peak cough flow among stroke patients with and without dysphagia.

Coughing is an important protective mechanism for keeping the airway clear, and adequate voluntary coughing reduces the risk of aspiration in patients with deglutition disorders. The purpose of this study was to compare the peak cough flow (PCF) of stroke patients with and without dysphagia and to identify the physical and respiratory determinants of PCF.Using a spirometer, we measured and compared the PCFs of 10 stroke patients with dysphagia (SPD), 20 stroke patients without dysphagia (SP) and 10 gender and age matched healthy controls (HC) recruited by using a notice at a clinic and in newspapers. The PCF of the SPD (mean ± SD, 160.1 ± 68.7 l/min) was significantly lower than that of the SP and HC (297.2 ± 114.2 l/min and 462.0 ± 84.4 l/min, respectively; one-way ANOVA, Scheffe's test, P < 0.05). The vital capacity (VC) and inspiratory reserve volume (IRV) of the SPD were lower than those of the HC. Stepwise multivariate regression analysis revealed that IRV and ambulation function (Functional Ambulation Categories, FAC) contributed 50% and 17% to the variance of PCF (P < 0.05), respectively. It is suggested that respiratory function, especially IRV, is important for maintaining PCF in SPD.

Impact of a rehabilitation program on dyspnea intensity and quality in patients with chronic obstructive pulmonary disease.

BACKGROUND: It has yet to be determined whether the language of dyspnea responds to pulmonary rehabilitation programs (PRP). OBJECTIVE: We tested the hypothesis that PRP affect both the intensity and quality of exercise-induced dyspnea in patients with chronic obstructive pulmonary disease (COPD). METHODS: We studied 49 patients equipped with a portable telemetric spiroergometry device during the 6-min walking test before and 4 weeks after PRP. In a first screening visit, appropriate verbal descriptors of dyspnea were chosen that patients were familiar with during daily living activities. Tidal volume, respiratory frequency, inspiratory capacity, inspiratory reserve volume (IRV) and dyspnea intensity were evaluated by a modified Borg scale every minute during the test. RESULTS: Qualitative descriptors of dyspnea were defined by three different sets of cluster descriptors (a-c) at the end of the exercise test, before and after PRP: a - work/effort (W/E); b - inspiratory difficulty (ID) and chest tightness (CT), and c - W/E, ID and/or CT. The three language subgroups exhibited similar lung function at baseline, and similar rating of dyspnea and ventilatory changes during exercise. The rehabilitation program shifted the Borg-IRV relationship (less Borg at any given IRV) towards the right without modifying the set of descriptors in most patients. CONCLUSIONS: Rehabilitation programs allowed patients to tolerate a greater amount of restrictive dynamic ventilatory defect by modifying the intensity, but not necessarily the quality of dyspnea.

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.

Effect of hormone replacement on exercise cardiopulmonary reserve and recovery performance in subclinical hypothyroidism.

Subclinical hypothyroidism (SH) patients present cardiopulmonary, vascular and muscle dysfunction, but there is no consensus about the benefits of levothyroxine (L-T4) intervention on cardiopulmonary performance during exercise. The aim of the present study was to investigate the effects of L-T4 on cardiopulmonary exercise reserve and recovery in SH patients. Twenty-three SH women, 44 (40-50) years old, were submitted to two ergospirometry tests, with an interval of 6 months of normalization of thyroid-stimulating hormone (TSH) levels (L-T4 replacement group) or simple observation (TSH = 6.90 µIU/mL; L-T4 = 1.02 ng/dL). Patients with TSH >10 µIU/mL were excluded from the study to assure that they would receive treatment in this later stage of SH. Twenty 30- to 57-year-old women with no thyroid dysfunction (TSH = 1.38 µIU/mL; L-T4 = 1.18 ng/dL) were also evaluated. At baseline, lower values of gas exchange ratio reserve (0.24 vs 0.30; P < 0.05) were found for SH patients. The treated group presented greater variation than the untreated group for pulmonary ventilation reserve (20.45 to 21.60 L/min; median variation = 5.2 vs 25.09 to 22.45 L/min; median variation = -4.75, respectively) and for gas exchange ratio reserve (0.19 to 0.27; median variation = 0.06 vs 0.28 to 0.18; median variation = -0.08, respectively). There were no relevant differences in cardiopulmonary recovery for either group at baseline or after follow-up. In the sample studied, L-T4 replacement improved exercise cardiopulmonary reserve, but no modification was found in recovery performance after exercise during this period of analysis.

Effect of hormone replacement on exercise cardiopulmonary reserve and recovery performance in subclinical hypothyroidism

Subclinical hypothyroidism (SH) patients present cardiopulmonary, vascular and muscle dysfunction, but there is no consensus about the benefits of levothyroxine (L-T4) intervention on cardiopulmonary performance during exercise. The aim of the present study was to investigate the effects of L-T4 on cardiopulmonary exercise reserve and recovery in SH patients. Twenty-three SH women, 44 (40-50) years old, were submitted to two ergospirometry tests, with an interval of 6 months of normalization of thyroid-stimulating hormone (TSH) levels (L-T4 replacement group) or simple observation (TSH = 6.90 μIU/mL; L-T4 = 1.02 ng/dL). Patients with TSH >10 μIU/mL were excluded from the study to assure that they would receive treatment in this later stage of SH. Twenty 30- to 57-year-old women with no thyroid dysfunction (TSH = 1.38 μIU/mL; L-T4 = 1.18 ng/dL) were also evaluated. At baseline, lower values of gas exchange ratio reserve (0.24 vs 0.30; P < 0.05) were found for SH patients. The treated group presented greater variation than the untreated group for pulmonary ventilation reserve (20.45 to 21.60 L/min; median variation = 5.2 vs 25.09 to 22.45 L/min; median variation = -4.75, respectively) and for gas exchange ratio reserve (0.19 to 0.27; median variation = 0.06 vs 0.28 to 0.18; median variation = -0.08, respectively). There were no relevant differences in cardiopulmonary recovery for either group at baseline or after follow-up. In the sample studied, L-T4 replacement improved exercise cardiopulmonary reserve, but no modification was found in recovery performance after exercise during this period of analysis.

Respiratory muscle strength in pregnancy.

BACKGROUND: Muscle respiratory strength studies during pregnancy are very scarce. The aim of this paper is to describe maximum inspiratory (PImax) and expiratory (PEmax) mean pressure values in women during their first pregnancy and to determine the relationship between the anthropometric, morphologic and physiologic variables of these pressures. METHODS: One hundred and twenty women (120) primigravidas were studied from the 5th to 40th gestational week, ages ranging from 20 to 29 years old, euthrophic and with low risk pregnancies. RESULTS: PImax and PEmax mean values were 88.5 ± 16.52 cmH(2)O and 99.76 ± 18.19 cmH(2)O respectively. There was no association between gestational age and PImax (r = -0.06; p = 0.49) or PEmax (r = -0.11; p = 0.22). There was also no difference between PImax and PEmax during pregnancy trimesters and no correlation between pregnancy age and the pressures in each trimester. Height was the only anthropometric variable indicating a significant PImax (r = 0.20; p = 0.02) association. Fundal uterus height and inter-recti abdominis distance were not associated to respiratory pressure values. PEmax is not associated with the group of predictor variables (p = 0.127) and PImax demonstrated an independent association with height and dyspnea during physical exertion reflected by the following equation: PImax = 0.6 + 57.9 height - 1.68 dyspnea under effort. The present study suggests that inspiratory and expiratory maximum pressure values are not altered during different stages of pregnancy, however longitudinal studies are needed to assess changes over time.

Natural orifice transluminal endoscopic surgery: cardiopulmonary safety of transesophageal mediastinoscopy.

BACKGROUND AND STUDY AIMS: Physiological reactions during natural orifice transluminal endoscopic surgery (NOTES) mediastinoscopy may lead to cardiorespiratory depression. The aim of the current study was to assess cardiopulmonary changes during transesophageal mediastinoscopy in an acute porcine model. METHODS: Transesophageal mediastinoscopy was performed under general anesthesia in eight female pigs with a bodyweight of 39 +/- 6 kg. Mediastinal access was achieved via a submucosal tunnel. The cardiac index and global end-diastolic volume index (reflecting preload) were measured every 3 minutes by transpulmonary thermodilution. The following parameters were also recorded: mediastinal pressure, heart rate, mean arterial pressure, systemic vascular resistance index (SVRI; reflecting afterload), peak inspiratory pressure, pH, pCO (2), and pO (2). RESULTS: In three animals, small tears in the parietal pleura resulted in tension pneumothoraces. The associated cardioplumonary deterioration was fatal in one pig. The other two pigs recovered after decompression with a chest tube. In the remaining five animals there were only mild hemodynamic and respiratory changes during mediastinoscopy. There was a significant ( P = 0.005) but minor transient fall in cardiac index, which correlated with a small rise in SVRI (r = - 0.857, P < 0.001). In the pigs with uncomplicated mediastinoscopy, on-demand insufflation via the endoscope resulted in median mediastinal pressures of 4.5 mm Hg (range 2.3 - 10.2 mm Hg). Overall, mediastinal and thoracic structures could be identified without difficulty via the transesophageal approach. CONCLUSIONS: NOTES mediastinoscopy carries a substantial risk of inadvertent development of a pneumothorax. Otherwise, it leads to negligible hemodynamic and pulmonary changes. In conclusion, close monitoring for the presence of a pneumothorax during NOTES mediastinoscopy appears to be mandatory.

Dynamic hyperinflation during daily activities: does COPD global initiative for chronic obstructive lung disease stage matter?

BACKGROUND: One of the contributors to exercise limitation in COPD is dynamic hyperinflation. Although dynamic hyperinflation appears to occur during several exercise protocols in COPD and seems to increase with increasing disease severity, it is unknown whether dynamic hyperinflation occurs at different severity stages according to the Global initiative for chronic Obstructive Lung Disease (GOLD) in daily life. The present study, therefore, aimed to compare dynamic hyperinflation between COPD GOLD stages II-IV during daily activities. METHODS: Thirty-two clinically stable patients with COPD GOLD II (n = 10), III (n = 12), and IV (n = 10) participated in this study. Respiratory physiology during a daily activity was measured at patients' homes with Oxycon Mobile. Inspiratory capacity maneuvers were performed at rest, at 2-min intervals during the activity, and at the end of the activity. Change in inspiratory capacity is commonly used to reflect change in end-expiratory lung volume (DeltaEELV) and, therefore, dynamic hyperinflation. The combination of static and dynamic hyperinflation was reflected by inspiratory reserve volume (IRV) during the activity. RESULTS: Overall, increase in EELV occurred in GOLD II-IV without significant difference between the groups. There was a tendency for a smaller DeltaEELV in GOLD IV. DeltaEELV was inversely related to static hyperinflation. IRV during the daily activity was related to the level of airflow obstruction. CONCLUSIONS: Dynamic hyperinflation occurs independent of GOLD stage during real-life daily activities. The combination of static and dynamic hyperinflation, however, increases with increasing airflow obstruction.

Performance during constant workrate cycling exercise in women with COPD and hyperinflation.

We aimed to characterize gender differences in exercise endurance, operating lung volumes and symptoms limitation during exercise in patients with COPD. Ninety-three women and 93 men with COPD matched for age and disease severity were evaluated during symptom-limited constant-work rate cycle exercise at 75% of peak capacity. Breathing pattern, inspiratory capacity, dyspnoea and leg discomfort Borg scores were recorded during exercise. Endurance time was shorter in women compared to men. Inspiratory capacity decreased at a similar rate during exercise in women and men (0.71 vs. 0.81 ml x s(- 1) for women and men respectively, p = 0.47) despite lower ventilation at end-exercise in women. At end-exercise, women showed lower inspiratory reserve volume (p < 0.005). Dyspnoea responses during exercise occurred with a steep rise near end-exercise, when inspiratory reserve volume approached a critical value, at 10% of total lung capacity, this onset of dyspnoea acceleration occurred earlier in women (p < 0.0001). At the same relative exercise intensity, women with COPD had lower endurance time than men. Compared to men, women with COPD were disadvantaged during exercise as they reached a critical inspiratory reserve volume earlier, leading to a steep increase in dyspnoea and to exercise termination.

Effects of depth and chest volume on cardiac function during breath-hold diving.

Cardiac response to breath-hold diving in human beings is primarily characterized by the reduction of both heart rate and stroke volume. By underwater Doppler-echocardiography we observed a "restrictive/constrictive" left ventricular filling pattern compatible with the idea of chest squeeze and heart compression during diving. We hypothesized that underwater re-expansion of the chest would release heart constriction and normalize cardiac function. To this aim, 10 healthy male subjects (age 34.2 +/- 10.4) were evaluated by Doppler-echocardiography during breath-hold immersion at a depth of 10 m, before and after a single maximal inspiration from a SCUBA device. During the same session, all subjects were also studied at surface (full-body immersion) and at 5-m depth in order to better characterize the relationship of echo-Doppler pattern with depth. In comparison to surface immersion, 5-m deep diving was sufficient to reduce cardiac output (P = 0.042) and increase transmitral E-peak velocity (P < 0.001). These changes remained unaltered at a 10-m depth. Chest expansion at 10 m decreased left ventricular end-systolic volume (P = 0.024) and increased left ventricular stroke volume (P = 0.024). In addition, it decreased transmitral E-peak velocity (P = 0.012) and increased deceleration time of E-peak (P = 0.021). In conclusion the diving response, already evident during shallow diving (5 m) did not progress during deeper dives (10 m). The rapid improvement in systolic and diastolic function observed after lung volume expansion is congruous with the idea of a constrictive effect on the heart exerted by chest squeeze.

A new breath-holding test may noninvasively reveal early lung abnormalities caused by smoking and/or obesity.

BACKGROUND: Smoking and obesity are leading global causes of death. The aim of the present study was to develop a test to detect early lung abnormalities caused by smoking and/or obesity and to elucidate the underlying mechanisms and major contributory factors. METHODS: One hundred twenty-nine healthy adults, 20 to 40 years of age, with normal spirometry findings, were divided into the following five groups: 38 healthy subjects (15 female subjects); 46 smokers (5 female smokers); 18 overweight nonsmokers (2 female nonsmokers; normal body mass index [BMI], >or= 25 kg/m(2); range, 25.0 to 37.2 kg/m(2)); 19 overweight smokers (1 female smoker; BMI range, 25.2 to 33.5 kg/m(2)); and 8 ex-smokers (BMI range, 20.8 to 24.1 kg/m(2)). A modified pulse oximeter was employed for measuring the fall in pulse oximetric saturation caused by 20-s breath-holding (dSpo(2)) at resting end expiration in the sitting posture. RESULTS: In healthy subjects, dSpo(2) had no significant correlation with age (r(2) = 0.009; p = 0.66). In smokers, dSpo(2) correlated with both the number of pack-years (r(2) = 0.590; p < 0.001) and closing volume (CV)/vital capacity (VC) ratio (r(2) = 0.573; p < 0.001). In overweight nonsmokers, dSpo(2) increased significantly with BMI alone (r(2) = 0.667; p < 0.001). In overweight smokers, the largest increase in the mean dSpo(2) was observed. Multiple linear regression analysis suggested that BMI and CV/VC are the two major contributing factors determining dSpo(2) during breath-holding. In young former smokers, no significant increase in the mean dSpo(2) was observed (p = 0.77) a mean (+/- SD) duration of 5.2 +/- 2.9 years after the cessation of smoking. No significant difference in dSpo(2) was observed between men and women. CONCLUSIONS: A new test that measures oxygen saturation during breath-holding reveals early lung abnormalities in subjects who either smoke or are overweight, especially if these factors are combined. Peripheral airway abnormalities and/or lung volume reduction may play roles in the greater desaturation.

The effects of flexible bronchoscopy on mechanical ventilation in a pediatric lung model.

BACKGROUND: Flexible bronchoscopy performed through endotracheal tubes (ETTs) in children receiving mechanical ventilation can significantly impact ventilation, but the magnitude of this impact has not been established. We used a lung model to simulate mechanical ventilation in a range of child sizes in order to determine how the insertion of pediatric flexible bronchoscopes into ETTs alters ventilatory parameters, especially tidal volume (Vt) and peak inspiratory pressure (PIP), in both healthy and diseased lungs. METHODS: We simulated five child sizes based on weight, and evaluated 22 bronchoscope/ETT combinations, first in pressure control (PC) ventilation mode and then in volume control (VC) ventilation mode. The combinations ranged from the 2.2-mm (bronchoscope outer diameter)/3.0-mm (ETT inner diameter) to 5.0-mm bronchoscope/8.0-mm ETT. The primary outcome measures were decrease in Vt after bronchoscope insertion during PC ventilation and increase in PIP during VC ventilation. RESULTS: In the PC ventilator mode, Vt decreased by > 50% with nine of the combinations, while during VC ventilation, PIP increased by >or= 20 cm H(2)O with seven combinations. The 2.2-mm bronchoscope/3.0-mm ETT, 2.8-mm bronchoscope/5.0-mm ETT, and 3.6-mm bronchoscope/5.0-mm ETT combinations severely impaired ventilation, while the 3.6-mm bronchoscope/4.5-mm ETT, 5.0-mm bronchoscope/6.5-mm ETT, and 5.0-mm bronchoscope/7.0-mm ETT combinations were incompatible with adequate ventilation. CONCLUSIONS: The insertion of bronchoscopes into ETTs can lead to clinically relevant decreases in Vt when in the PC ventilator mode and large increases in PIP during VC ventilation. The minimum bronchoscope/ETT diameter difference required to maintain adequate ventilation increases with child size.

Methadone-induced respiratory depression in the neonatal guinea pig.

Respiratory depression, the most serious side-effect of opioid treatment, is well documented for morphine, the most commonly used opioid in neonatal care. Less is known about methadone, a clinically relevant opioid analgesic, especially during neonatal development. This study was undertaken to determine the neonatal respiratory effects of methadone. We hypothesize that methadone is equipotent to morphine, compared to our previous morphine results in the same animal model, but has a much longer duration of action, due to its longer elimination half-life. Neonatal guinea pigs (3-14 days old) randomly received a single subcutaneous dose of methadone or saline. Using a non-invasive plethysmographic method, we measured ventilatory and metabolic parameters before injection and at intervals for 32 hr after injection while pups breathed "room air" or 5% CO(2) gas mixtures. Methadone-induced depression of ventilation was most evident during 5% CO(2) challenge. The onset of drug effects was within 15 min for all ages and doses, but the duration of action decreased with age. While the depth of methadone-induced respiratory depression did not depend on pup age, the control of breathing was different in 3-day-old pups, where inspiratory time increased fourfold; twice that of older pups. We conclude that methadone induces a naloxone reversible respiratory depression in guinea pig neonates and, in the very young, causes an abnormal breathing pattern due to changes in respiratory timing. Methadone is more potent than morphine with respect to neonatal respiratory depression, but surprisingly, the duration of methadone action was not longer than morphine.