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Respiratory Physiology & Neurobiology Oct 2011Phrenic motoneurons are located in the cervical spinal cord and innervate the diaphragm muscle, the main inspiratory muscle in mammals. Similar to other skeletal... (Comparative Study)
Comparative Study Review
Phrenic motoneurons are located in the cervical spinal cord and innervate the diaphragm muscle, the main inspiratory muscle in mammals. Similar to other skeletal muscles, phrenic motoneurons and diaphragm muscle fibers form motor units which are the final element of neuromotor control. In addition to their role in sustaining ventilation, phrenic motor units are active in other non-ventilatory behaviors important for airway clearance such as coughing or sneezing. Diaphragm muscle fibers comprise all fiber types and are commonly classified based on expression of contractile proteins including myosin heavy chain isoforms. Although there are differences in contractile and fatigue properties across motor units, there is a matching of properties for the motor neuron and muscle fibers within a motor unit. Motor units are generally recruited in order such that fatigue-resistant motor units are recruited earlier and more often than more fatigable motor units. Thus, in sustaining ventilation, fatigue-resistant motor units are likely required. Based on a series of studies in cats, hamsters and rats, an orderly model of motor unit recruitment was proposed that takes into consideration the maximum forces generated by single type-identified diaphragm muscle fibers as well as the proportion of the different motor unit types. Using this model, eupnea can be accomplished by activation of only slow-twitch diaphragm motor units and only a subset of fast-twitch, fatigue-resistant units. Activation of fast-twitch fatigable motor units only becomes necessary when accomplishing tasks that require greater force generation by the diaphragm muscle, e.g., sneezing and coughing.
Topics: Animals; Diaphragm; Humans; Phrenic Nerve; Pulmonary Ventilation; Recruitment, Neurophysiological
PubMed: 21763470
DOI: 10.1016/j.resp.2011.06.028 -
Cleveland Clinic Journal of Medicine Jun 2005Various neurologic diseases such as multiple sclerosis and Parkinson disease can cause pulmonary complications. Pulmonary disorders often manifest late in a... (Review)
Review
Various neurologic diseases such as multiple sclerosis and Parkinson disease can cause pulmonary complications. Pulmonary disorders often manifest late in a neuromuscular disease, but occasionally a respiratory problem may be the first sign. Often the first signs are sleep disturbances and nocturnal desaturation. Although the diseases are diverse, common principles apply in their management.
Topics: Humans; Nervous System Diseases; Pulmonary Ventilation; Respiration Disorders; Respiratory Function Tests
PubMed: 16018292
DOI: 10.3949/ccjm.72.6.511 -
Journal of Applied Physiology... Apr 2023We analyzed the fractal dimension (Df) of lung gas and blood distribution imaged with synchrotron radiation K-edge subtraction (KES), in six anesthetized adult New...
We analyzed the fractal dimension (Df) of lung gas and blood distribution imaged with synchrotron radiation K-edge subtraction (KES), in six anesthetized adult New Zealand White rabbits. KES imaging was performed in upright position during stable Xe gas (64% in O) inhalation and iodine infusion (Iomeron, 350 mg/mL), respectively, at baseline and after induced bronchoconstriction by aerosolized methacholine (125 mg/mL, 90 s) and bronchodilator (salbutamol, 10 mg/mL, 90 s) inhalation, at two axial image levels. Lung Xe and iodine images were segmented, and maps of regional lung gas and blood fractions were computed. The Df of lung gas (Df) and blood (Df) distribution was computed based on a log-log plot of variation coefficient as a function of region volume. Df decreased significantly during bronchoconstriction ( < 0.0001), and remained low after salbutamol. Df depended on the axial image level ( < 0.0001), but did not change with bronchoconstriction. Df was significantly associated with arterial [Formula: see text] ( = 0.67, = 0.002), and negatively associated with [Formula: see text] ( = -0.62, = 0.006), respiratory resistance ( = -0.58, = 0.011), and elastance ( = -0.55, = 0.023). These data demonstrate the reduced Df of gas distribution during acute bronchoconstriction, and the association of this parameter with physiologically meaningful variables. This finding suggests a decreased complexity and space-filling properties of lung ventilation during bronchoconstriction, and could serve as a functional imaging biomarker in obstructive airway diseases. Here, we used an energy-subtractive imaging technique to assess the fractal dimension (Df) of lung gas and blood distribution and the effect of acute bronchoconstriction. We found that Df of gas significantly decreases in bronchoconstriction. Conversely, Df of blood exhibits gravity-dependent changes only, and is not affected by acute bronchoconstriction. Our data show that the fractal dimension of lung gas detects the emergence of clustered rather than scattered loss of ventilatory units during bronchoconstriction.
Topics: Animals; Rabbits; Bronchoconstriction; Asthma; Synchrotrons; Fractals; Pulmonary Ventilation; Lung; Albuterol; Iodine
PubMed: 36927142
DOI: 10.1152/japplphysiol.00051.2023 -
Proceedings of the American Thoracic... Dec 2009There is now conclusive evidence that, as a group, subjects with asthma have lower levels of lung function as compared with their peers and that a significant proportion... (Review)
Review
There is now conclusive evidence that, as a group, subjects with asthma have lower levels of lung function as compared with their peers and that a significant proportion of subjects with persistent asthma are at risk of developing non-fully reversible airflow limitation, the clinical hallmark of chronic obstructive pulmonary disease. Although at the population level the most conspicuous form of airflow limitation in asthma seems to be that of subjects who wheeze during the first years of life and whose symptoms persist into adult life, asthma-related lung deficits can be related to both acquired deficits in growth of lung function in childhood and steeper decline of lung function in adult life. These trajectories of lung function are likely to differ across subgroups of individuals with asthma, suggesting that different windows of opportunity may exist to modify the natural course of the disease before irreversible deficits are established. These observations indicate the importance of identifying biomarkers that can be used to target children and adults with asthma at increased risk for airflow limitation and determining whether pharmacological interventions can protect these patients from the development of chronic obstructive pulmonary disease.
Topics: Adult; Asthma; Child; Humans; Lung; Pulmonary Disease, Chronic Obstructive; Pulmonary Ventilation
PubMed: 20008881
DOI: 10.1513/pats.200908-085DP -
PloS One 2015The aims of this study were to investigate the effects of manganese (Mn) dust exposure on lung functions and evaluate the potential synergistic effect between smoking...
PURPOSE
The aims of this study were to investigate the effects of manganese (Mn) dust exposure on lung functions and evaluate the potential synergistic effect between smoking and Mn dust exposure among refinery workers.
METHODS
A retrospective study including 1658 workers in a ferromanganese refinery was conducted, with subjects who were from the Guangxi manganese-exposed workers healthy cohort (GXMEWHC). Based on the Mn manganese cumulative exposure index (Mn-CEI), all subjects were divided into the low exposure group (n = 682) and the high exposure group (n = 976). A pulmonary function test was performed using an electronic spirometer, including the values and percentages of FVC, FEV1, FEV1/FVC, MMEF, PEFR, MVV, respectively.
RESULTS
No significant effect of Mn dust exposure on the pulmonary function was found in the female workers (all p>0.05). However, there was an obvious decrease in the male workers in the high exposure group compared with those in the low exposure group (FVC -60 ml, FEV1 -120 ml, MMEF -260 ml/s, MVV -5.06 L, all p<0.05). In the high exposure group, the reduction in FVC% predicted, MMEF and MMEF% predicted was 1.0%, 210 mL/s, and 4.9%, respectively. In particular, among the exposed subjects smokers had a statistically significant decrease in lung function compared with non-smokers and the reduction in FVC% predicted, MMEF and MMEF% predicted was 1.0%, 210 mL/s, and 4.9%, respectively (p<0.05). Partial correlation analysis showed that there was also negative correlation between Mn-CEI and decreased changes in MMEF (r = -0.159, p = 0.018) and also MMEF% predicted (r = -0.163, p = 0.015).
CONCLUSIONS
Mn dust can impair the pulmonary ventilation function of male workers but not females, and individual smoking habits and manganese exposure had a synergistic effect on the lung function decrease.
Topics: Adult; Analysis of Variance; China; Cohort Studies; Dust; Female; Humans; Male; Manganese; Metallurgy; Occupational Exposure; Pulmonary Ventilation; Respiratory Function Tests; Retrospective Studies; Sex Factors; Smoking; Spirometry; Surveys and Questionnaires
PubMed: 25664879
DOI: 10.1371/journal.pone.0116558 -
Critical Care (London, England) 2009Electrical impedance tomography (EIT) can be used to measure impedance changes related to the thoracic content of air and blood. Few studies, however, have utilised EIT...
INTRODUCTION
Electrical impedance tomography (EIT) can be used to measure impedance changes related to the thoracic content of air and blood. Few studies, however, have utilised EIT to make concurrent measurements of ventilation and perfusion. This experimental study was performed to investigate the feasibility of EIT to describe ventilation/perfusion (V/Q) matching after acute changes of pulmonary perfusion and aeration.
METHODS
Six mechanically ventilated, anaesthetised pigs in the supine position were studied at baseline, after inflation of a balloon in the inferior caval vein (Binfl) to reduce cardiac output and after an increased positive end-expiratory pressure (PEEP) of 20 cmH2O (PEEP20) to increase pulmonary aeration. EIT measurements were performed at the mid-thoracic level to measure the amplitude of impedance changes related to ventilation (ZV) and perfusion (ZQ), both globally and in four defined regions of interest (ROI) extending from the ventral to dorsal distance.
RESULTS
A largely parallel distribution of ZV and ZQ in all four ROIs during baseline conditions corresponded to a bell-shaped frequency distribution of ZV/ZQ ratios with only moderate scatter. Binfl and PEEP20 with unchanged tidal volumes significantly increased the mismatch of regional ZV and ZQ, the scatter of ZV/ZQ ratios and the heterogeneity of the ZV/ZQ frequency distribution. Significant positive and negative correlations were demonstrated between fractional alveolar dead space (r2 = 0.63 [regression coefficient]) and venous admixture (r2 = 0.48), respectively, and the global ZV/ZQ ratio.
CONCLUSIONS
EIT may be used to monitor the distribution of pulmonary ventilation and perfusion making detailed studies of V/Q matching possible.
Topics: Animals; Electric Impedance; Feasibility Studies; Models, Animal; Perfusion; Pulmonary Ventilation; Swine; Tomography; Treatment Outcome
PubMed: 19265527
DOI: 10.1186/cc7741 -
Respiratory Research Aug 2021Inhaled epoprostenol (iEPO) has been shown to reduce pulmonary artery pressure and improve oxygenation. iEPO is mainly delivered via a syringe pump with feed tubing... (Comparative Study)
Comparative Study
BACKGROUND
Inhaled epoprostenol (iEPO) has been shown to reduce pulmonary artery pressure and improve oxygenation. iEPO is mainly delivered via a syringe pump with feed tubing connected to a vibrating mesh nebulizer with high or low formulation concentration delivery.
METHODS
An in vitro study and a two-period retrospective case-control study were implemented. The in vitro study compared iEPO delivery via invasive ventilation at low concentrations of 7.5, and 15 mcg/mL and high concentration at 30 mcg/mL, to deliver the ordered dose of 30 and 50 ng/kg/min for three clinical scenarios with predicted body weight of 50, 70 and 90 kg. While in the clinical study, adult patients receiving iEPO via invasive ventilation to treat refractory hypoxemia, pulmonary hypertension, or right ventricular failure were included. 80 patients received low concentration iEPO at multiple concentrations (2.5, 7.5, and 15 mcg/mL, depending on the ordered dose) from 2015 to 2017, while 84 patients received high concentration iEPO at 30 mcg/mL from 2018 to 2019.
RESULTS
In the in vitro study, there were no significant differences in aerosol deposition between high vs low concentrations of iEPO at a dose of 50 ng/kg/min. In the clinical study, age, gender, ethnicity, and indications for iEPO were similar between high and low concentration groups. After 30-120 min of iEPO administration, both delivery strategies significantly improved oxygenation in hypoxemic patients and reduced mean pulmonary arterial pressure (mPAP) for patients with pulmonary hypertension. However, no significant differences of the incremental changes were found between two delivery groups. Compared to low concentration, high concentration delivery group had better adherence to the iEPO weaning protocol (96% vs 71%, p < 0.001), fewer iEPO syringes utilized per patient (5 [3, 10] vs 12 [6, 22], p = 0.001), and shorter duration of invasive ventilation (6 [3, 12] vs 9 [5, 18] days, p = 0.028). Intensive care unit length of stay and mortality were similar between two groups.
CONCLUSION
Compared to low concentration delivery of iEPO, high concentration iEPO via a vibrating mesh nebulizer maintained clinical benefits and increased clinician compliance with an iEPO weaning protocol, required less medication preparation time, and shortened duration of invasive ventilation.
Topics: Administration, Inhalation; Adult; Aged; Antihypertensive Agents; Case-Control Studies; Dose-Response Relationship, Drug; Epoprostenol; Female; Humans; Intubation, Intratracheal; Male; Middle Aged; Nebulizers and Vaporizers; Pulmonary Ventilation; Reagent Kits, Diagnostic; Retrospective Studies
PubMed: 34419068
DOI: 10.1186/s12931-021-01827-4 -
Experimental Physiology Jun 2019What is the central question of this study? To what extent are the mechanical-ventilatory responses to upper-body exercise influenced by task-specific locomotor... (Randomized Controlled Trial)
Randomized Controlled Trial
NEW FINDINGS
What is the central question of this study? To what extent are the mechanical-ventilatory responses to upper-body exercise influenced by task-specific locomotor mechanics? What is the main finding and its importance? When compared with lower-body exercise performed at similar ventilations, upper-body exercise was characterized by tidal volume constraint, dynamic lung hyperinflation and an increased propensity towards neuromechanical uncoupling of the respiratory system. Importantly, these responses were independent of respiratory dysfunction and flow limitation. Thus, the mechanical ventilatory responses to upper-body exercise are attributable, in part, to task-specific locomotor mechanics (i.e. non-respiratory loading of the thorax).
ABSTRACT
The aim of this study was to determine the extent to which the mechanical ventilatory responses to upper-body exercise are influenced by task-specific locomotor mechanics. Eight healthy men (mean ± SD: age, 24 ± 5 years; mass, 74 ± 11 kg; and stature, 1.79 ± 0.07 m) completed two maximal exercise tests, on separate days, comprising 4 min stepwise increments of 15 W during upper-body exercise (arm-cranking) or 30 W during lower-body exercise (leg-cycling). The tests were repeated at work rates calculated to elicit 20, 40, 60, 80 and 100% of the peak ventilation achieved during arm-cranking ( ). Exercise measures included pulmonary ventilation and gas exchange, oesophageal pressure-derived indices of respiratory mechanics, operating lung volumes and expiratory flow limitation. Subjects exhibited normal resting pulmonary function. Arm-crank exercise elicited significantly lower peak values for work rate, O uptake, CO output, minute ventilation and tidal volume (p < 0.05). At matched ventilations, arm-crank exercise restricted tidal volume expansion relative to leg-cycling exercise at 60% (1.74 ± 0.61 versus 2.27 ± 0.68 l, p < 0.001), 80% (2.07 ± 0.70 versus 2.52 ± 0.67 l, p < 0.001) and 100% (1.97 ± 0.85 versus 2.55 ± 0.72 l, p = 0.002). Despite minimal evidence of expiratory flow limitation, expiratory reserve volume was significantly higher during arm-cranking versus leg-cycling exercise at 100% (39 ± 8 versus 29 ± 8% of vital capacity, p = 0.002). At any given ventilation, arm-cranking elicited greater inspiratory effort (oesophageal pressure) relative to thoracic displacement (tidal volume). Arm-cranking exercise is sufficient to provoke respiratory mechanical derangements (restricted tidal volume expansion, dynamic hyperinflation and neuromechanical uncoupling) in subjects with normal pulmonary function and expiratory flow reserve. These responses are likely to be attributable to task-specific locomotor mechanics (i.e. non-respiratory loading of the thorax).
Topics: Adult; Exercise; Exercise Test; Humans; Lung; Male; Oxygen Consumption; Pulmonary Ventilation; Respiratory Function Tests; Young Adult
PubMed: 30919515
DOI: 10.1113/EP087648 -
Scientific Reports Oct 2021The roles of endothelial nitric oxide synthase (eNOS) in the ventilatory responses during and after a hypercapnic gas challenge (HCC, 5% CO, 21% O, 74% N) were assessed...
The roles of endothelial nitric oxide synthase (eNOS) in the ventilatory responses during and after a hypercapnic gas challenge (HCC, 5% CO, 21% O, 74% N) were assessed in freely-moving female and male wild-type (WT) C57BL6 mice and eNOS knock-out (eNOS-/-) mice of C57BL6 background using whole body plethysmography. HCC elicited an array of ventilatory responses that were similar in male and female WT mice, such as increases in breathing frequency (with falls in inspiratory and expiratory times), and increases in tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives. eNOS-/- male mice had smaller increases in minute ventilation, peak inspiratory flow and inspiratory drive, and smaller decreases in inspiratory time than WT males. Ventilatory responses in female eNOS-/- mice were similar to those in female WT mice. The ventilatory excitatory phase upon return to room-air was similar in both male and female WT mice. However, the post-HCC increases in frequency of breathing (with decreases in inspiratory times), and increases in tidal volume, minute ventilation, inspiratory drive (i.e., tidal volume/inspiratory time) and expiratory drive (i.e., tidal volume/expiratory time), and peak inspiratory and expiratory flows in male eNOS-/- mice were smaller than in male WT mice. In contrast, the post-HCC responses in female eNOS-/- mice were equal to those of the female WT mice. These findings provide the first evidence that the loss of eNOS affects the ventilatory responses during and after HCC in male C57BL6 mice, whereas female C57BL6 mice can compensate for the loss of eNOS, at least in respect to triggering ventilatory responses to HCC.
Topics: Animals; Female; Hypercapnia; Hypoxia; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide Synthase Type III; Pulmonary Ventilation; Respiration; Respiratory Insufficiency; Tidal Volume
PubMed: 34663876
DOI: 10.1038/s41598-021-99922-5 -
The Journal of Physiology Aug 2004This study was designed to test the hypothesis that the frequency response of the systems controlling the motor activity of breathing and walking in quadrupeds is...
This study was designed to test the hypothesis that the frequency response of the systems controlling the motor activity of breathing and walking in quadrupeds is compatible with the idea that supra-spinal locomotor centres could proportionally drive locomotion and ventilation. The locomotor and the breath-by-breath ventilatory and gas exchange (CO2 output (VCO2) and O2 uptake (VO2)) responses were studied in five sheep spontaneously walking on a treadmill. The speed of the treadmill was changed in a sinusoidal pattern of various periods (from 10 to 1 minute) and in a step-like manner. The frequency and amplitude of the limb movements, oscillating at the same period as the treadmill speed changes, had a constant gain with no phase lag (determined by Fourier analysis) regardless the periods of oscillations. In marked contrast, when the periods of speed oscillations decreased, the amplitude (peak-to-mean) of minute ventilation (VE) oscillations decreased sharply and significantly (from 6.1 +/- 0.4 l min(-1) to 1.9 +/- 0.2 l min(-1)) and the phase lag between ventilation and treadmill speed oscillations increased (to 105 +/- 25 degrees during the 1 min oscillation periods). VE response followed VCO2 very closely. The drop in VE amplitude ratio was proportional to that in VCO2 (from 149 +/- 48 ml min(-1) to 38 +/- 5 ml min(-1)) with a slightly longer phase lag for ventilation than for VCO2. These results show that beyond the onset period of a locomotor activity, the amplitude and phase lag of the VE response depends on the period of the walking speed oscillations, tracking the gas exchange rate, regardless of the amplitude of the motor act of walking. Locomotion thus appears unlikely to cause a simple parallel and proportional increase in ventilation in walking sheep.
Topics: Animals; Biological Clocks; Female; Locomotion; Pulmonary Ventilation; Sheep; Walking
PubMed: 15235099
DOI: 10.1113/jphysiol.2003.057729