Mean Inspiratory Flow Research Articles

Predicting parameters of airway dynamics generated from inspiratory and expiratory plethysmographic airway loops, differentiating subtypes of chronic obstructive diseases

BackgroundThe plethysmographic shift volume–flow loop (sRaw-loop) measured during tidal breathing allows the determination of several lung function parameters such as the effective specific airway resistance (sReff), calculated from the ratio...

Metabolic and ventilatory changes during postural change from the supine position to the reclining position in bedridden older patients.

The prevention of pneumonia in bedridden older patients is important, and its recurrence in these patients is a relevant issue. Patients who are bedridden and inactive, and have dysphagia are considered to be at risk for pneumonia. Efforts to reduce the bedridden state and low activity may be necessary to reduce the risk of developing pneumonia in bedridden older patients. This study aimed to clarify the effects of postural change from the supine position to the reclining position on metabolic and ventilatory parameters and on safety in bedridden older patients. Using a breath gas analyzer and other tools, we assessed the following 3 positions: lying on the back (supine), resting in the Fowler position (Fowler), and resting in an 80° recline wheelchair (80°). Measurements were oxygen uptake, carbon dioxide output, gas exchange ratio, tidal volume (VT), minute volume, respiratory rate, inspiratory time, expiratory time, total respiratory time, mean inspiratory flow, metabolic equivalents, end-expiratory oxygen, and end-expiratory carbon dioxide as well as various vital signs. The study analysis included 19 bedridden participants. The change in oxygen uptake driven by changing the posture from the supine position to the Fowler position was as small as 10.8 mL/minute. VT significantly increased from the supine position (398.4 ± 111.2 mL) to the Fowler position (426.9 ± 106.8 mL) (P = .037) and then showed a decreasing trend in the 80° position (416.8 ± 92.5 mL). For bedridden older patients, sitting in a wheelchair is a very low-impact physical activity, similar to that in normal people. The VT of bedridden older patients was maximal in the Fowler position, and the ventilatory volume did not increase with an increasing reclining angle, unlike that in normal people. These findings suggest that appropriate reclining postures in clinical situations can promote an increase in the ventilatory rate in bedridden older patients.

Sevoflurane and Hypercapnia Blunt the Physiological Variability of Spontaneous Breathing: A Comparative Interventional Study.

Background: Although spontaneous breathing is known to exhibit substantial physiological fluctuation that contributes to alveolar recruitment, changes in the variability of the respiratory pattern following inhalation of carbon dioxide (CO2) and volatile anesthetics have not been characterized. Therefore, we aimed at comparing the indices of breathing variability under wakefulness, sleep, hypercapnia and sedative and anesthetic concentrations of sevoflurane. Methods: Spontaneous breathing pattern was recorded on two consecutive days in six rabbits using open whole-body plethysmography under wakefulness and spontaneous sleep and following inhalation of 5% CO2, 2% sevoflurane (0.5 MAC) and 4% (1 MAC) sevoflurane. Tidal volume (VT), respiratory rate (RR), minute ventilation (MV), inspiratory time (TI) and mean inspiratory flow (VT/TI) were calculated from the pressure fluctuations in the plethysmograph. Means and coefficients of variation were calculated for each measured variable. Autoregressive model fitting was applied to estimate the relative contributions of random, correlated, and oscillatory behavior to the total variance. Results: Physiological sleep decreased MV by lowering RR without affecting VT. Hypercapnia increased MV by elevating VT. Sedative and anesthetic concentrations of sevoflurane increased VT but decreased MV due to a decrease in RR. Compared to the awake stage, CO2 had no effect on VT/TI while sevoflurane depressed significantly the mean inspiratory flow. Compared to wakefulness, the variability in VT, RR, MV, TI and VT/TI were not affected by sleep but were all significantly decreased by CO2 and sevoflurane. The variance of TI originating from correlated behavior was significantly decreased by both concentrations of sevoflurane compared to the awake and asleep conditions. Conclusions: The variability of spontaneous breathing during physiological sleep and sevoflurane-induced anesthesia differed fundamentally, with the volatile agent diminishing markedly the fluctuations in respiratory volume, inspiratory airflow and breathing frequency. These findings may suggest the increased risk of lung derecruitment during procedures under sevoflurane in which spontaneous breathing is maintained.

Feasibility of non-invasive respiratory drive and breathing pattern evaluation using CPAP in COVID-19 patients.

PurposeIncreased respiratory drive and respiratory effort are major features of acute hypoxemic respiratory failure (AHRF) and might help to predict the need for intubation. We aimed to explore the feasibility of a non-invasive respiratory drive evaluation and describe how these parameters may help to predict the need for intubation.Materials and methodsWe conducted a prospective observational study. All consecutive patients with COVID-19-related AHRF requiring high-flow nasal cannula (HFNC) were screened for inclusion. Physiologic data (including: occlusion pressure (P0.1), tidal volume (Vt), inspiratory time (Ti), peak and mean inspiratory flow (Vt/Ti)) were collected during a short continuous positive airway pressure (CPAP) session. Measurements were repeated once, 12–24 h later.ResultsMeasurements were completed in 31 patients after the screening of 45 patients (70%). P0.1 was high (4.4 [2.7–5.1]), but it was not significantly higher in patients who were intubated. The Vt (p = .006), Vt/Ti (p = .019), minute ventilation (p = .006), and Ti/Ttot (p = .003) were higher among intubated patients compared to non-intubated patients. Intubated patients had a significant increase in their diaphragm thickening fraction, Vt, and Vt/Ti over time.ConclusionsNon-invasive assessment of respiratory drive was feasible in patients with AHRF and showed an increased P0.1, although it was not predictive of intubation.

Role of raphe magnus 5-HT1A receptor in increased ventilatory responses induced by intermittent hypoxia in rats

BackgroundIntermittent hypoxia induces increased ventilatory responses in a 5-HT-dependent manner. This study aimed to explore that effect of raphe magnus serotonin 1A receptor (5-HT1A) receptor on the increased ventilatory responses induced by intermittent hypoxia.MethodsStereotaxic surgery was performed in adult male rats, and acute and chronic intermittent hypoxia models were established after recovery from surgery. The experimental group received microinjections of 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) into the raphe magnus nucleus (RMg). Meanwhile, the control group received microinjections of artificial cerebrospinal fluid instead of 8-OH-DPAT. Ventilatory responses were compared among the different groups of oxygen status. 5-HT expressions in the RMg region were assessed by immunohistochemistry after chronic intermittent hypoxia.ResultsCompared with the normoxia group, the acute intermittent hypoxia group exhibited higher ventilatory responses (e.g., shorter inspiratory time and higher tidal volume, frequency of breathing, minute ventilation, and mean inspiratory flow) (P < 0.05). 8-OH-DPAT microinjection partly weakened these changes in the acute intermittent hypoxia group. Further, compared with the acute intermittent hypoxia group, rats in chronic intermittent hypoxia group exhibited higher measures of ventilatory responses after 1 day of intermittent hypoxia (P < 0.05). These effects peaked after 3 days of intermittent hypoxia treatment and then decreased gradually. Moreover, these changes were diminished in the experimental group. 5-HT expression in the RMg region increased after chronic intermittent hypoxia, which was consistent with the changing trend of ventilatory responses. While activation of the 5-HT1A receptor in the RMg region alleviated this phenomenon.ConclusionsThe results indicate that RMg 5-HT1A receptor, via changing the expression level of 5-HT in the RMg region, is involved in the modulation of the increased ventilatory responses induced by intermittent hypoxia.

Prediction and types of dead-space fraction during exercise in male chronic obstructive pulmonary disease patients.

A high dead space (VD) to tidal volume (VT) ratio during peak exercise (VD/VTpeak) is a sensitive and consistent marker of gas exchange abnormalities; therefore, it is important in patients with chronic obstructive pulmonary disease (COPD). However, it is necessary to use invasive methods to obtain VD/VTpeak, as noninvasive methods, such as end-tidal PCO2 (PETCO2peak) and PETCO2 adjusted with Jones’ equation (PJCO2peak) at peak exercise, have been reported to be inconsistent with arterial PCO2 at peak exercise (PaCO2peak). Hence, this study aimed to generate prediction equations for VD/VTpeak using statistical techniques, and to use PETCO2peak and PJCO2peak to calculate the corresponding VD/VTpeaks (i.e., VD/VTpeakETVD/VTpeakJ).A total of 46 male subjects diagnosed with COPD who underwent incremental cardiopulmonary exercise tests with PaCO2 measured via arterial catheterization were enrolled. Demographic data, blood laboratory tests, functional daily activities, chest radiography, two-dimensional echocardiography, and lung function tests were assessed.In multivariate analysis, diffusing capacity, vital capacity, mean inspiratory tidal flow, heart rate, and oxygen pulse at peak exercise were selected with a predictive power of 0.74. There were no significant differences in the PCO2peak values and the corresponding VD/VTpeak values across the three types (both p = NS).In subjects with COPD, VD/VTpeak can be estimated using statistical methods and the PETCO2peak and PJCO2peak. These methods may have similar predictive power and thus can be used in clinical practice.

Performance of Different Low-Flow Oxygen Delivery Systems.

The delivery of a high and consistent [Formula: see text] is imperative to treat acute hypoxemia. The objective of this study was to analyze the effective inspired oxygen concentration delivered by different low-flow oxygen therapy systems challenged with different oxygen flows and respiratory patterns in an experimental lung model. An adult lung model ventilated in volume control mode simulated different respiratory patterns to obtain mean inspiratory flow of 22.5, 30.0, 37.5, or 45.0 L/min. The oxygen concentration sampled inside the lung model by nasal cannula, simple face mask, non-rebreather mask, and double-trunk mask above nasal cannula tested at oxygen flows of 10, 12.5, and 15 L/min was quantified. The 3 masks were sealed tight onto the model's airway opening. They were also tested with standardized leaks to determine their clinical performance. All oxygen delivery systems delivered higher oxygen concentration with increasing oxygen flows, regardless of the respiratory pattern. Within each device, the increase in inspiratory flow decreased oxygen concentration when using nasal cannula (P = .03), the simple face mask (P = .03), but not the non-rebreather mask (P = .051) nor the double-trunk mask (P = .13). In sealed condition, the double-trunk mask outperformed the non-rebreather mask and simple face mask (P < .001); mean oxygen concentration was 84.2%, 68.5%, and 60.8%, respectively. Leaks amplified oxygen concentration differences between the double-trunk mask and the other masks as the oxygen delivery decreased by 4.6% with simple face mask (95% CI 3.1-6.1%, P < .001), 7.8% with non-rebreather mask (95% CI 6.3-9.3%, P < .001), and 2.5% with double-trunk mask (95% CI 1-4%, P = .002). With leaks, the oxygen concentration provided by the simple face mask and the non-rebreather mask was similar (P = .15). Lung oxygen concentration values delivered by the double-trunk mask were higher than those obtained with other oxygen delivery systems, especially when leaks were present.

Different Inspiratory Flow Waveform during Volume-Controlled Ventilation in ARDS Patients.

The most used types of mechanical ventilation are volume- and pressure-controlled ventilation, respectively characterized by a square and a decelerating flow waveform. Nowadays, the clinical utility of different inspiratory flow waveforms remains unclear. The aim of this study was to assess the effects of four different inspiratory flow waveforms in ARDS patients. Twenty-eight ARDS patients (PaO2/FiO2 182 ± 40 and PEEP 11.3 ± 2.5 cmH2O) were ventilated in volume-controlled ventilation with four inspiratory flow waveforms: square (SQ), decelerating (DE), sinusoidal (SIN), and trunk descending (TDE). After 30 min in each condition, partitioned respiratory mechanics and gas exchange were collected. The inspiratory peak flow was higher in the DE waveform compared to the other three waveforms, and in SIN compared to the SQ and TDE waveforms, respectively. The mean inspiratory flow was higher in the DE and SIN waveforms compared with TDE and SQ. The inspiratory peak pressure was higher in the SIN and SQ compared to the TDE waveform. Partitioned elastance was similar in the four groups; mechanical power was lower in the TDE waveform, while PaCO2 in DE. No major effect on oxygenation was found. The explored flow waveforms did not provide relevant changes in oxygenation and respiratory mechanics.

P-NE015. Acute effects of respiratory muscle stretching on ventilatory patterns and respiratory muscle activity

Introduction . Respiratory muscle stretching is useful in reducing chest wall rigidity, consequently increasing chest wall expansion and improving ventilatory patterns. There are few reports that have examined the effects of these techniques in relation to both minute ventilation and inspiratory muscle activities. The purpose of this study was to evaluate the acute effects of respiratory muscle stretching on ventilatory patterns and respiratory muscle activities in healthy persons. Methods . Ten healthy young men participated in the experiment. Subjects were placed in the Fowler’s position. The stretching of both bilateral neck and pectoralis major muscles by a physical therapist was performed throughout the expiratory phase, allowing inspiratory muscles to reach their maximum length during the relaxation time. Two sets of 10 consecutive stretches were performed for each muscle, with a 30 s interval between the series. The ventilatory pattern and inspiratory muscle activities (both sternocleidomastoid and external intercostal muscles) were evaluated through spirometry and electromyography before and immediately after each intervention. Both measurements were taken while the subject breathed at a rate of 30 times per minute. Muscle discharges were quantified using the root mean square to analyze the changes in the contraction levels. The study was performed according to the guidelines set by the Ethics Committee of Aomori University of Health and Welfare. All participants signed an informed consent form. Results . Respiratory muscle stretching promoted a significant acute increase in maximum voluntary ventilation, mean inspiratory flow, and inspiratory muscle activities during tachypnea compared with the control group. Conclusion . Acute effects of respiratory muscle stretching suggested increased respiratory muscle activities and/or improved expansion of ventilatory functions.

Effects of Ketamine on Respiration and Components of the Respiratory Cycle after Extremity Trauma and Severe Conscious Hemorrhage

Background Ketamine is currently recommended for analgesic use on the battlefield for Soldiers with severe hemorrhage and compromised respiration. However, few controlled studies have been conducted to support such use. Hence, we conducted the following study to determine effects of an intravascular analgesic dose of ketamine on respiratory responses to trauma and a 55 % hemorrhage (T+Hem) in conscious rats. We hypothesized that ketamine would have no adverse effects on respiration under such experimental conditions. Methods Rats were randomly assigned to one of two experimental groups: 1) T + Hem given 0.9% saline (Veh; n=8); or 2) T + Hem given 5 mg/kg ketamine in saline (0.5 mg/100 μl; Ket, n=7). All rats (male; ~ 350grams) were surgically implanted with a carotid catheter. After 24 hours, rats were anesthetized briefly (10 min) to undergo trauma (crushing of the right gastrocnemius and semimembranosus muscles for 30 sec with forceps) and fibula fracture. Rats were allowed to awaken, and 90 min later were placed in a whole body plethysmography chamber. Rats then underwent a conscious hemorrhage (~55% of blood volume during 25 min) via the indwelling carotid catheter. At the end of hemorrhage, Veh or Ket was injected via the carotid catheter. Respiratory measures were collected over 1 min intervals and analyzed via Data Sciences International FinePointe software. Primary respiratory measures were respiration rate (RR; breaths/min), tidal volume (TV; ml), and minute volume (MV; ml/min; RR x TV). TV and MV were normalized by body weight. To further characterize respiration, components of the respiratory cycle were evaluated: Inspiratory time (Ti, sec), time spent inhaling during in each breath; Expiratory time (Te; sec), time spent exhaling during each breath); Peak inspiratory flow (Pif, ml/sec), estimated maximum inspiratory flow that occurs in one breath; Mean inspiratory flow (Mif, equal to VT/Ti; ml/sec); Peak expiratory flow (Pef, ml/sec), estimated maximum expiratory flow that occurs in one breath. Rats were observed for 75 min after injection. Data were analyzed via multiway analysis of variance (ANOVA) for repeated measures using the Statistical Analysis System. Results After injection, Veh was associated with gradually declining (P <.05) levels of RR, MV, Pif, Pef, and Mif. Te gradually increased (P ≤ 0.045) after Veh, whereas TV and Ti were stable during the ensuring 75 min period. Compared with Veh: 1) Ket had no effects on RR, TV, Ti, Te, and Mif; and 2) Ket transiently and modestly (P≤ 0.046) decreased MV, Pif, and Pef at specific time points after injection. Conclusions Our results suggest that the Ket-associated decreases in MV resulted primarily from decreased Pif and Pef. It is extremely important that pain medications administered on the battlefield not depress respiration responses during hemorrhage. In our animal model of trauma and hemorrhage, a loss of 55% blood volume produced significant respiratory depression; however, Ket did not meaningfully exacerbate these responses. These results support the use of Ket in wounded Soldiers with severe hemorrhage and compromised respiration.

The Effect of Different Interfaces on the Aerosol Delivery with Vibrating Mesh Nebulizer During Noninvasive Positive Pressure Ventilation

Background: The effect of different interfaces on the aerosol delivery with vibrating mesh nebulizer during noninvasive positive pressure ventilation (NIV) is not clear. Materials and Methods: Noninvasive ventilator and four interfaces were connected to IngMar ASL 5000 lung simulator. Meanwhile, the vibrating mesh nebulizer was connected to a ventilator circuit to simulate the nebulization during noninvasive ventilation. The nebulizer position was placed at proximal position (near the mask) and distal position (15 cm away from the mask); the inspiratory positive airway pressure (IPAP) and the expiratory positive airway pressure (EPAP) were set to 16/4, 16/8, 20/4, and 20/8 cmH2O, respectively. The aerosol was collected through a disposable filter placed between the simulated lung and the mask, after which the aerosol delivery was calculated. Meanwhile, we recorded the inspiratory tidal volume and the mean inspiratory flow. Results: The aerosol delivery varied between 1.7% ± 0.0% and 21.1% ± 1.1%. Only when EPAP was set to 4 cmH2O, the statistical difference in aerosol delivery was observed between the two types of interface, and between different leak port locations (p < 0.01; p = 0.04, respectively). When IPAP/EPAP was set to 16/4 and 20/4 cmH2O, respectively, at different nebulizer positions, there was a statistical difference between the interface with the same type but different leak port locations and between the interface with same leak port location but different inner volumes (all p < 0.01). Also, there was a correlation between the aerosol delivery and interface volume (p < 0.01, R2 = 0.55; p < 0.01, R2 = 0.51, respectively), and between aerosol delivery and the intentional leak of interfaces (p < 0.01, R2 = 0.59; p < 0.01, R2 = 0.48, respectively). When EPAP was set to 4 and 8 cmH2O, respectively, the aerosol delivery of nebulizer distal position was significantly higher than that of proximal position (12.2% ± 5.0% vs. 9.1% ± 4.1%, p < 0.05; 2.5% ± 0. 5% vs. 2.1% ± 0.3%, p < 0.01, respectively). Conclusion: Interfaces have a significant effect on aerosol delivery during NIV. The interfaces with different inner volumes, intentional leak, and leak port location may all have an effect on aerosol delivery. The addition of a 15 cm tube between the nebulizer and the mask significantly increases the aerosol delivery.

Determinants of response to hypercapnia and to progressive and transient hypoxia in obstructive sleep apnea patients.

The knowledge regarding the control of breathing during wakefulness in patients affected by obstructive sleep apnea (OSAS) is still challenging. The aim of this study is firstly to analyze hypoxic and hypercapnic ventilatory response in OSA patients in comparison to controls and secondly, to investigate correlations between chemosensivity and both lung function tests, such as arterial blood gas analysis and spirometric parameters, and clinical characteristics, such as age and BMI. Seventeen never treated OSA patients (16M; 53±13.2 years; BMI=34.5±8.1; AHI=45±14.7) underwent nocturnal cardiopulmonary monitoring test, complete lung function tests (spirometry, lung volumes and arterial blood gas analysis on room air). Read's rebreathing test was used to evaluate hypercapnic ventilatory response (HVR<inf>CO2</inf>); hypoxic ventilatory response (HVR<inf>O2</inf>) was studied through progressive and transient methods. The response was expressed in terms of slope of linear regression for HVR<inf>CO2</inf> and of hyperbolic curve for HVR<inf>O2</inf> between minute ventilation (VE) or mean inspiratory flow (VT/Ti) and PetCO<inf>2</inf> or PetO<inf>2</inf>. The OSA group showed increased transient, but not progressive, HVR<inf>O2</inf> and a lower HVR<inf>CO2</inf>. A lower HVR<inf>CO2</inf> was predicted by greater values of BMI (P<0.01). Progressive HVR<inf>O2</inf> increased with age and lower FEV<inf>1</inf>/VC, while transient HVR<inf>O2</inf> (P<0.05) was inversely correlated with the nocturnal lowest SaO<inf>2</inf> (P<0.01). Nocturnal intermittent hypoxic stimuli increases daytime glomic reactivity to transient hypoxia, while BMI is the main independent determinants of the bulbar response to hypercapnia in normocapnic OSAS patients.

Initial setting of high-flow nasal oxygen post extubation based on mean inspiratory flow during a spontaneous breathing trial.

High flow nasal cannula (HFNC) is commonly used post-extubation in intensive care (ICU). Patients' comfort during HFNC is affected by flow rate. The study aims to describe the relationship between pre-extubation inspiratory flow requirements and the post-extubation flow rates on HFNC that maximises patient's comfort. This was an observational, retrospective study conducted in a university-affiliated ICU. We included patients extubated following successful spontaneous breathing trial (SBT). During the SBT we recorded variables including inspiratory flow. Patients who passed the SBT were extubated onto HFNC. HFNC was titrated from 20L/min and increased in steps of 10L/min, up to 60L/min. At each step, patient's level of comfort was assessed. Fraction of inspired oxygen was titrated to maintain oxygen saturation 92-97%. Nineteen participants were enrolled in the study. There was a significant positive correlation between mean inspiratory flow pre-extubation and the flow setting on HFNC which achieved the best comfort post-extubation (r2 0.88; p<0.001). Overall, greatest comfort was observed for HFNC flows between 30 and 40L/min but with individual variability. Measuring mean inspiratory flow during an SBT allows for individualised setting of HFNC flow rate immediately post-extubation and achieves the greatest comfort and interface tolerance.

Triaging of respiratory protective equipment on the assumed risk of SARS-CoV-2 aerosol exposure in patient-facing healthcare workers delivering secondary care: a rapid review

ObjectivesIn patient-facing healthcare workers delivering secondary care, what is the evidence behind UK Government personal protective equipment (PPE) guidance on surgical masks versus respirators for SARS-CoV-2 protection?DesignTwo independent reviewers performed...

CYCLOOXYGENASE MECHANISMS IN THE REGULATION OF RESPIRATORY EFFECTS OF TUMOR NECROSIS FACTOR

Introduction. It is known that the systemic level of the major pro-inflammatory cytokine increases in many respiratory diseases such as asthma, COPD and sleep apnea [1, 2]. The lung ventilation changes and the pathological types of breathing are typical in these diseases. By the reason, the research of the respiratory effects of cytokine is actual. The aim of this study was to compare the respiratory effects of tumor necrosis factor - α (TNF-α) before and after pretreatment with diclofenac, a nonspecific cyclooxygenase (COX) inhibitor. Materials and methods. Тhe experiments were performed in tracheostomized anaesthetized with urethane rats. A respiratory flow head connected to a pneumotachometer (AD Instruments ML141 Spirometer, Dunedin, New Zealand) was used to measure peak airflow and respiratory rate. The hypoxic ventilatory response was measured by using rebreathing with hypoxic gas mixture before and after the tail vein injection of TNF-α (10 μg/rat). In order to determine the role of the cyclooxygenase pathway in the ventilatory effects of TNF-α, introperitoneal administration of diclofenac, a nonspecific COX inhibitor, was used (0.5 mg/rat). Results and discussion. We have shown that the increase in level of TNF-α in blood increased the parameters of respiration such as minute ventilation (by 40%), tidal volume (by 18%), and the mean inspiratory flow (by 33%). The slope of the hypoxic ventilatory response decreased from 6.06 ± 0.91 to 3.48 ± 0.38 ml/min-1 mmHg-1 (by 40%) 40 min after administration of TNF-α (p &lt; 0.05), the slope of tidal volume and mean inspiratory flow also decreased (by 27%) (p &lt; 0.05). After pretreatment with diclofenac, the influence of TNF-α on breathing was dampened, as no significant changes were observed. Conclusion. We concluded that the elevation of inflammatory cytokine level in blood intensifies ventilation during the resting breathing that may be associated with increased central inspiratory activity. At the same time TNF-α reduces the chemoreflex sensitivity to hypoxia, thereby worsening the compensatory capabilities of the respiratory system. Thus, the results of our study suggest participation of inflammatory cytokines in mechanisms of central breathing control and chemoreception. Diclofenac pretreatment eliminated the respiratory effects of TNF-α. The data indicate that the ability of TNF-α to enhance basal ventilation and to reduce the ventilatory hypoxic response is mediated by the COX pathway.

PARTICIPATION OF INOS IN THE EFFECT OF IL-1β ON LUNG VENTILATION AND HYPOXIC CHEMORECEPTION

With systemic inflammation, hypoxia, and an increase in the respiratory, a significant increase in the systemic level of pro-inflammatory cytokines is observed. Recently we demonstrated that elevated IL-1β level in blood reduces the ventilatory response to hypoxia. The aim of the present study was to examine the hypothesis that the respiratory effect of IL-1β may be mediating the NO-dependent mechanisms.The experiments were performed on anaesthetized rats. We studied the effects of intravenous administration of cytokine during inhibition of iNO-synthase. In order to we used aminoguanidine bicarbonate - specific inhibitor of iNOS, which was injected in the tail vein for 30 minutes before the administration of cytokine. During the hypoxic rebreathing experiments, was found that the increase of IL-1β level in blood weakens the respiratory response to hypoxia. The ventilatory, tidal volume and mean inspiratory flow responses decreased by 29%, 31% and 53% respectively. INO-synthase inhibitor pretreatment eliminated these respiratory effects of IL-1β. Thus the data indicate that the ability of IL-1β to reduce the ventilatory hypoxic response is mediated by the NO-dependent pathway.

Performance Comparison of N95 and P100 Filtering Facepiece Respirators with Presence of Artificial Leakage

National Institute for Occupational Safety and Health-approved P100 filtering facepiece respirators (FFRs) have a higher filter efficiency compared to the N95 filters. However, the former typically produce higher flow resistance (Rf). Consequently, when faceseal leakage is present, the proportion of leakage airflow for P100 FFRs may exceed that of N95s, resulting in a higher total inward leakage (TIL) of the P100. In this manikin-based study, the performance of two pairs of N95 and P100 FFRs (N95-A versus P100-A; N95-B versus P100-B) were compared under five sealing conditions (fully sealed and partially sealed with one, two, or three leaks of 0.8-mm, and one 2-mm leak). Sodium chloride particles (CMD ~45 nm) were used as the challenge aerosol. Respirators were tested under three constant flows (15, 50, and 85 L/min) and three cyclic flows (mean inspiratory flow = 15, 50, and 85 L/min). Both filter penetration (Pfilter) and TIL were determined. The Rf under constant flows was recorded. Based on Pfilter, TIL, and Rf, the quality factor (qf) was calculated to compare the overall performance of N95 and P100 FFRs. For a fully sealed condition, the Pfilter was much lower for the P100 FFRs than for the N95 FFRs. When small leaks were inserted (0.8-mm and 2 × 0.8-mm), the TIL was higher for the P100 FFRs than for the N95 FFRs under the lowest tested flow (15 L/min), while for greater leaks (3 × 0.8-mm and 2-mm), the TIL of the P100 FFRs was always higher regardless of the flow. The Rf of P100 FFRs was measured twice as high as the N95. The qf values were also found higher for the N95 FFRs than for the P100 FFRs regardless of leak size and breathing flow. With the presence of artificial leakage, a P100 FFR with high-flow-resistance may not be as protective as a low-flow-resistance N95 FFR. This finding suggests that future efforts should be directed to reducing the breathing resistance when designing P100 FFRs.

Sustained maximal inspiration has similar effects compared to incentive spirometers

PurposeTo compare the effects of flow incentive spirometer (FIS), volume incentive spirometer (VIS), and sustained maximal inspiration exercise (SMI) on breathing pattern, chest wall motion, and thoracoabdominal asynchrony. MethodsSixteen healthy adults aged 27.63 ± 5.26 years were evaluated by optoelectronic plethysmography in the supine position with trunk inclination of 45° during quiet breathing and during exercise performance. ResultsIn the comparisons among exercises, VIS promoted a significantly higher inspiratory time and lower mean inspiratory flow compared with FIS. The rating of perceived exertion according to the Borg Scale was significantly higher after the performance of FIS compared with VIS. Regarding asynchrony, none of the exercises caused changes in thoracoabdominal synchrony between the rib cage and abdomen. However, both devices significantly reduced the asynchrony between the pulmonary and abdominal rib cage compared with quiet breathing. ConclusionSMI exercise was equivalent to incentive spirometers and may be an interesting alternative for clinical use in cases in which it is not possible to acquire the devices.

Focal ischemic stroke leads to lung injury and reduces alveolar macrophage phagocytic capability in rats

BackgroundIschemic stroke causes brain inflammation, which we postulate may result in lung damage. Several studies have focused on stroke-induced immunosuppression and lung infection; however, the possibility that strokes may trigger lung inflammation has been overlooked. We hypothesized that even focal ischemic stroke might induce acute systemic and pulmonary inflammation, thus altering respiratory parameters, lung tissue integrity, and alveolar macrophage behavior.MethodsForty-eight Wistar rats were randomly assigned to ischemic stroke (Stroke) or sham surgery (Sham). Lung function, histology, and inflammation in the lung, brain, bronchoalveolar lavage fluid (BALF), and circulating plasma were evaluated at 24 h. In vitro, alveolar macrophages from naïve rats (unstimulated) were exposed to serum or BALF from Sham or Stroke animals to elucidate possible mechanisms underlying alterations in alveolar macrophage phagocytic capability. Alveolar macrophages and epithelial and endothelial cells of Sham and Stroke animals were also isolated for evaluation of mRNA expression of interleukin (IL)-6 and tumor necrosis factor (TNF)-α.ResultsTwenty-four hours following ischemic stroke, the tidal volume, expiratory time, and mean inspiratory flow were increased. Compared to Sham animals, the respiratory rate and duty cycle during spontaneous breathing were reduced, but this did not affect lung mechanics during mechanical ventilation. Lungs from Stroke animals showed clear evidence of increased diffuse alveolar damage, pulmonary edema, and inflammation markers. This was associated with an increase in ultrastructural damage, as evidenced by injury to type 2 pneumocytes and endothelial cells, cellular infiltration, and enlarged basement membrane thickness. Protein levels of proinflammatory mediators were documented in the lung, brain, and plasma (TNF-α and IL-6) and in BALF (TNF-α). The phagocytic ability of macrophages was significantly reduced. Unstimulated macrophages isolated from naïve rats only upregulated expression of TNF-α and IL-6 following exposure to serum from Stroke rats. Exposure to BALF from Stroke or Sham animals did not change alveolar macrophage behavior, or gene expression of TNF-α and IL-6. IL-6 expression was increased in macrophages and endothelial cells from Stroke animals.ConclusionsIn rats, focal ischemic stroke is associated with brain–lung crosstalk, leading to increased pulmonary damage and inflammation, as well as reduced alveolar macrophage phagocytic capability, which seems to be promoted by systemic inflammation.

Inspiratory muscle weakness contributes to exertional dyspnea in chronic thromboembolic pulmonary hypertension.

Determination of potentially-reversible factors contributing to exertional dyspnea remains an unmet clinical need in chronic thromboembolic pulmonary hypertension (CTEPH). Therefore, we aimed to evaluate the influence of inspiratory muscle weakness (IMW) on exercise capacity and dyspnea during effort in patients with CTEPH. We performed a prospective cross-sectional study that included thirty-nine consecutive patients with CTEPH (48 ± 15 yrs, 61% female) confirmed by right heart catheterization that underwent an incremental cardiopulmonary exercise test, 6-minute walk test and maximum inspiratory pressure (MIP) measurement. MIP < 70%pred was found in 46% of patients. On a multiple linear regression analysis, MIP was independently associated with 6MWD and . Patients with MIP < 70% presented greater than those with MIP ≥ 70%. Additionally, they also presented stronger sensations of dyspnea throughout exercise, even when adjusted for ventilation. At rest and at different levels of exercise, mean inspiratory flow (VT/TI) was significantly higher in patients with MIP < 70%. In conclusion, IMW is associated with a rapid increase of dyspnea, higher inspiratory load and poor exercise capacity in patients with CTEPH.