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Robinson FE, Shykoff BE, Warkander DE. Components of aircraft life support systems interact with each other and the user. Front Physiol 2022; 13:969167. [PMID: 36225306 PMCID: PMC9548541 DOI: 10.3389/fphys.2022.969167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 08/15/2022] [Indexed: 11/23/2022] Open
Abstract
The life support system in a tactical aircraft provides necessary supplemental oxygen to the aircrew. However, interactions among its various components may generate unexpected breathing loads. We focus here on the interactions between a regulator and breathing mask commonly used together in the U.S. Navy, the CRU-103 regulator and MBU 23/P mask, and some effects of the interactions on the user. The data reported were collected during a larger research effort examining potential physiological and cognitive effects of low regulator inlet pressures. Seventeen participants completed a series of tasks under mild exercise while breathing 40% O2 (balance N2) from an MBU-23/P mask supplied by a CRU-103 regulator with supply pressures 10, 6, 4, and 2 psig (CRU-103 specifications are for inlet pressures from 5 to 120 psig). Variables measured included flow to the mask and pressures at the regulator supply, in the hose to the mask, and in the mask. In addition to restricting inspiratory flow, low inlet pressure to the CRU-103 caused a counterintuitive overshoot in gas delivery pressure at end-inspiration, a mean increase of 1.5 cm H2O between the 10- and 2 psig conditions. The added pressure to the exhalation valve increased the expiratory threshold, the pressure to start expiratory flow, by approximately 2 cm H2O, increasing the effort needed to exhale.
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Affiliation(s)
- F. Eric Robinson
- Naval Aerospace Medical Research Laboratory, Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Dayton, OH, United States
- *Correspondence: F. Eric Robinson,
| | - Barbara E. Shykoff
- Naval Aerospace Medical Research Laboratory, Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Dayton, OH, United States
- Oak Ridge Institute for Science and Engineering, Oak Ridge, TN, United States
| | - Dan E. Warkander
- Naval Aerospace Medical Research Laboratory, Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Dayton, OH, United States
- Oak Ridge Institute for Science and Engineering, Oak Ridge, TN, United States
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Wu W, Zhang X, Lin L, Ou Y, Li X, Guan L, Guo B, Zhou L, Chen R. Transdiaphragmatic pressure and neural respiratory drive measured during inspiratory muscle training in stable patients with chronic obstructive pulmonary disease. Int J Chron Obstruct Pulmon Dis 2017; 12:773-781. [PMID: 28280321 PMCID: PMC5338837 DOI: 10.2147/copd.s126354] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
PURPOSE Inspiratory muscle training (IMT) is a rehabilitation therapy for stable patients with COPD. However, its therapeutic effect remains undefined due to the unclear nature of diaphragmatic mobilization during IMT. Diaphragmatic mobilization, represented by transdiaphragmatic pressure (Pdi), and neural respiratory drive, expressed as the corrected root mean square (RMS) of the diaphragmatic electromyogram (EMGdi), both provide vital information to select the proper IMT device and loads in COPD, therefore contributing to the curative effect of IMT. Pdi and RMS of EMGdi (RMSdi%) were measured and compared during inspiratory resistive training and threshold load training in stable patients with COPD. PATIENTS AND METHODS Pdi and neural respiratory drive were measured continuously during inspiratory resistive training and threshold load training in 12 stable patients with COPD (forced expiratory volume in 1 s ± SD was 26.1%±10.2% predicted). RESULTS Pdi was significantly higher during high-intensity threshold load training (91.46±17.24 cmH2O) than during inspiratory resistive training (27.24±6.13 cmH2O) in stable patients with COPD, with P<0.01 for each. Significant difference was also found in RMSdi% between high-intensity threshold load training and inspiratory resistive training (69.98%±16.78% vs 17.26%±14.65%, P<0.01). CONCLUSION We concluded that threshold load training shows greater mobilization of Pdi and neural respiratory drive than inspiratory resistive training in stable patients with COPD.
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Affiliation(s)
- Weiliang Wu
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Xianming Zhang
- Department of Respiratory Medicine, The First Affiliated Hospital of Guizhou Medical University, Guizhou, People’s Republic of China
| | - Lin Lin
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Yonger Ou
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Xiaoying Li
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Lili Guan
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Bingpeng Guo
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Luqian Zhou
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
| | - Rongchang Chen
- State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou
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Soilemezi E, Koco E, Tsimpos C, Tsagourias M, Savvidou S, Matamis D. Effects of continuous positive airway pressure on diaphragmatic kinetics and breathing pattern in healthy individuals. Respirology 2016; 21:1262-9. [DOI: 10.1111/resp.12823] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 03/15/2016] [Accepted: 03/18/2016] [Indexed: 01/16/2023]
Affiliation(s)
| | - Entela Koco
- Papageorgiou General Hospital; Thessaloniki Greece
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4
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Cough variant asthma: lessons learned from deep inspirations. Lung 2011; 190:17-22. [PMID: 22139550 DOI: 10.1007/s00408-011-9348-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 11/09/2011] [Indexed: 10/15/2022]
Abstract
The pathophysiology of cough variant asthma is poorly understood. In particular, the mechanisms that cause different symptoms in typical asthma (in which wheeze predominates) compared with cough variant asthma (in which cough predominates) have not been determined. Traditional explanations include higher wheezing thresholds, differences in cough sensitivity, and/or differences in small airway function. Recent studies using high-dose methacholine challenge testing suggest that altered small-airway function plays a role. Preservation or loss of the bronchoprotective effect of a deep inspiration may be a fundamental pathophysiologic difference between asthma, cough variant asthma, methacholine-induced cough with normal sensitivity, and eosinophilic bronchitis.
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5
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The respiratory muscles in eucapnic obesity: Their role in dyspnea. Respir Med 2009; 103:1276-85. [DOI: 10.1016/j.rmed.2009.03.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 02/27/2009] [Accepted: 03/20/2009] [Indexed: 11/20/2022]
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6
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Luo Y, Qiu Z, Wu H, Steier J, Jolley C, Zhong N, Moxham J, Polkey M. Neural drive during continuous positive airway pressure (CPAP) and pressure relief CPAP. Sleep Med 2009; 10:731-8. [DOI: 10.1016/j.sleep.2008.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Revised: 06/07/2008] [Accepted: 06/09/2008] [Indexed: 10/21/2022]
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7
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Chirakalwasan N, Shim C, Appel D. Continuous positive airway pressure as a treatment modality for orthopnea in a patient with chronic obstructive pulmonary disease and extreme obesity undergoing left superficial femoral thrombectomy. J Cardiothorac Vasc Anesth 2008; 23:522-5. [PMID: 18834835 DOI: 10.1053/j.jvca.2008.05.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2008] [Indexed: 11/11/2022]
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8
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Nobre MEP, Lopes F, Cordeiro L, Marinho PEM, Silva TNS, Amorim C, Cahalin LP, Dornelas de Andrade A. Inspiratory muscle endurance testing: pulmonary ventilation and electromyographic analysis. Respir Physiol Neurobiol 2006; 155:41-8. [PMID: 16713403 DOI: 10.1016/j.resp.2006.04.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 04/01/2006] [Accepted: 04/07/2006] [Indexed: 11/19/2022]
Abstract
This study analyzed regional pulmonary ventilation and electromyographic (EMG) activity of the respiratory muscles during an inspiratory muscle endurance (IME) test in 10 young women. Radioaerosol (99mTc-DTPA) was generated using a jet nebulizer connected to a linear inspiratory loading system. The lung scintigraphic analysis showed an increase in the radioaerosol deposition using loads of 20 and 30 cmH(2)O (p<0.01). The vertical gradient showed a larger radioaerosol deposition in the medium third of the lungs during the control period (p<0.001). There were larger amounts of radioaerosol deposition in the medium third when compared with the upper and lower third at 30 cmH(2)O (p<0.001). The horizontal gradient showed a larger deposition in the intermediate and central segments during all phases (p<0.00). Electromyographic activity from the muscles of the lower rib cage increased with loads of 20 and 30 cmH(2)O (p<0.03). There was an increase in deposition of radioaerosol when the load increased (r=0.584, p=0.000 for the left lung and r=0.609, p=0.000 for right lung). These findings suggest that during the IME test, EMG activity in the muscles of the lower rib cage increase during progressive respiratory workloads is associated with a greater radioaerosol deposition in the medium third and intermediate and central segments of the lungs.
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Lotti P, Gigliotti F, Tesi F, Stendardi L, Grazzini M, Duranti R, Scano G. Respiratory muscles and dyspnea in obese nonsmoking subjects. Lung 2006; 183:311-23. [PMID: 16389724 DOI: 10.1007/s00408-005-2544-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
To our knowledge no data have been reported on the contribution to acute increase in dyspnea by the respiratory muscles in obese nonsmoking subjects. To better focus on this topic, we studied seven obese subjects and an age-matched normal control group, assessing baseline pulmonary function, breathing pattern, esophageal pressure (Pes), and gastric (Pga) and transdiaphragmatic (Pdi) pressures. Pes was also recorded during a sniff maneuver (Pessn). During a hypercapnic rebreathing test we recorded inspiratory swing in Pes (Pessw), expiratory changes in Pga, and inspiratory swings in Pdi (Pdisw). Change in inspiratory capacity was considered the mirror image of end-expiratory lung volume (EELV). Dyspnea was assessed by a modified Borg scale. Under control conditions, patients exhibited a reduced expiratory reserve volume and intrinsic positive end-expiratory pressure (PEEPi). At the end of hypercapnic stimulation, compared with controls our obese subjects exhibited greater respiratory frequency (Rf), shorter expiratory time, greater Pessw, and lower Pdisw. Increases in EELV and PEEPi were found in the obese subjects but not in controls. Changes in Borg correlated with changes in PETCO2, VE, Pessw (%Pessn), and Pdisw to a greater extent in patients than in controls. Stepwise regression analysis indicated the amount of variability in Borg that was predicted by both Pdisw (r2 = 0.31, p < 0.0004), and Pessw (%Pessn) (r2 = 0.09, p < 0.005) in controls, and by Pessw (%Pessn) (r2 = 0.40, p < 0.00001) in obese subjects. We conclude that the rib cage muscles contributed to dyspnea to a greater extent in this subset of obese subjects.
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Affiliation(s)
- Pamela Lotti
- Department of Internal Medicine, Section of Clinical Immunology, Allergology and Respiratory Diseases, University of Florence, Firenze, Italy
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Eves ND, Jones RL, Petersen SR. The Influence of the Self-Contained Breathing Apparatus (SCBA) on Ventilatory Function and Maximal Exercise. ACTA ACUST UNITED AC 2005; 30:507-19. [PMID: 16293900 DOI: 10.1139/h05-137] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our previous work showed that breathing low density gases during exercise with the self-contained breathing apparatus (SCBA) improves maximal ventilation (VE) and maximal oxygen consumption [Formula: see text] This suggests that the SCBA limits exercise by adding a resistive load to breathing. In this study we compared [Formula: see text] with and without the various components comprising the SCBA to determine their impact on [Formula: see text] Twelve males performed 4 randomly ordered incremental exercise tests to exhaustion on a treadmill: (1) low-resistance breathing valve only (CON); (2) full SCBA (SCBA); (3) SCBA regulator only (REG); and (4) carrying the cylinder and harness assembly but breathing through a low-resistance breathing valve (PACK). Compared to CON, [Formula: see text] was reduced to a similar extent in the SCBA and REG trials (14.9% and 13.1%, respectively). The PACK condition also reduced [Formula: see text] but to a lesser extent (4.8 ± 5.3%). At [Formula: see text][Formula: see text] was decreased and expiratory mouth pressure and external breathing resistance (BR) were increased in both the SCBA and REG trials. There was a significant correlation between the change in maximal [Formula: see text] and [Formula: see text] with the SCBA. The results show that the SCBA reduces [Formula: see text] by limiting [Formula: see text] secondary to the increased BR of the SCBA regulator. Key words: ventilation, breathing resistance, expiratory flow limitation, [Formula: see text]
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Affiliation(s)
- Neil D Eves
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta T6G 2H9, Canada
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11
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Hours S, Lejaille M, Pozzi D, Falaize L, Zerah-Lancner F, Raphael JC, Lofaso F. Perceived inspiratory difficulty in neuromuscular patients with primary muscle disorders. Neuromuscul Disord 2004; 14:289-96. [PMID: 15099586 DOI: 10.1016/j.nmd.2004.01.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 01/05/2004] [Accepted: 01/30/2004] [Indexed: 10/26/2022]
Abstract
Intensity of perceived inspiratory difficulty was investigated in 17 patients with severe respiratory insufficiency due to muscle disease, compared with healthy matched controls. Subjects breathed through a threshold valve generating a constant inspiratory negative pressure proportional to their maximal inspiratory pressure. Four load levels ranging from 10 to 40% of the maximal inspiratory pressure were applied in random order. Patients had significantly less perceived inspiratory difficulty than controls at each load level expressed as a percentage of maximal inspiratory pressure P < 0.001. However, when the load was expressed as the absolute value, the slope of the Borg scale score versus mouth pressure was similar in the two groups (P = 0.11). The ventilatory pattern remained unchanged in each group as the load increased. We conclude that in patients with myopathy, loads leading to respiratory muscle fatigue (40% of maximal inspiratory pressure) may fail to produce perceived inspiratory difficulty.
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Affiliation(s)
- Sandrine Hours
- Services de Réanimation Médicale, Physiologie-Explorations Fonctionnelles, et Centre d'Innovation Technologique Hôpital Raymond Poincaré, AP-HP, 92380 Garches, France
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12
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Weiner P, Beckerman M, Berar-Yanay N, Magadle R. The perception of dyspnea after bronchoconstriction and bronchodilation in patients with asthma. Respir Med 2003; 97:1120-5. [PMID: 14561019 DOI: 10.1016/s0954-6111(03)00161-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND It is well documented that the perception of dyspnea (POD), subjectively reported by patients, is an important index used to guide treatment. The severity of dyspnea following methacholine-induced bronchoconstriction and added mechanical loads is increasing in popular. No formal attention has been addressed to the reduction in dyspnea following bronchodilators. STUDY OBJECTIVE To investigate if the magnitude of dyspnea perceived by a subject is independent on the direction (e.g., bronchoconstriction or bronchodilation) of the change in airway resistance. METHODS The POD was measured in 26 mild moderate asthmatic patients following bronchodilation, using beta2-agonists, and following bronchoconstriction, induced by methacholine challenge, to almost the same magnitude. RESULTS The increase in forced expiratory volume in 1 s (FEV1), 30 min after the inhalation of beta2-agonist (mean +/- SEM 22.3 +/- 0.8%), was associated with a statistically significant decrease (P < 0.005) in the POD. The mean decrease in FEV1 following methacoline challenge, was 23 +/- 0.7% and was followed by a statistically significant increase (P < 0.005) in the POD. The magnitude of the decrease in the POD following albuterol was almost identical to the magnitude of the increase in the POD following methacholine. CONCLUSIONS In stable mild-moderate asthmatic patients, the changes in the magnitude of dyspnea, perceived by a subject, is independent on the direction of the change in the FEV1.
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Affiliation(s)
- Paltiel Weiner
- Department of Medicine A, Hillel Yaffe Medical Center, Hadera, Israel.
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13
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Shore SA, Moore PE. Effects of cytokines on contractile and dilator responses of airway smooth muscle. Clin Exp Pharmacol Physiol 2002; 29:859-66. [PMID: 12207563 DOI: 10.1046/j.1440-1681.2002.03756.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Increased bronchoconstrictor responses to contractile agonists and decreased dilator responses to beta-adrenoceptor agonists are characteristics of human asthma. One explanation for these features of asthma is that cytokines released in the asthmatic airway have direct effects on airway smooth muscle cells that alter their phenotype. 2. The present review summarizes data indicating that inflammatory cytokines, such as interleukin (IL)-1 beta and tumour necrosis factor-alpha, T helper (h) 1 cytokines, such as interferon-gamma, and Th2 cytokines, such as IL-13 and IL-5, have the capacity to enhance contractile responses and/or decrease relaxant responses of airway smooth muscle. These effects are observed in smooth muscle from human airways and airway smooth muscle of other species. 3. Understanding the mechanistic basis for the effects of these cytokines may prove to be an important step in improving the efficacy of beta-adrenoceptor agonists for the treatment of asthma.
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Affiliation(s)
- Stephanie A Shore
- Physiology Program, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
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Lougheed MD, Flannery J, Webb KA, O'Donnell DE. Respiratory sensation and ventilatory mechanics during induced bronchoconstriction in spontaneously breathing low cervical quadriplegia. Am J Respir Crit Care Med 2002; 166:370-6. [PMID: 12153973 DOI: 10.1164/rccm.2109003] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Intensity of dyspnea during induced bronchoconstriction in asthma is strongly related to the reduction in inspiratory capacity (IC) as a result of dynamic hyperinflation. To determine the role of rib cage and intercostal muscle afferents in symptom perception during bronchoconstriction, we measured the relationship between dyspnea intensity and IC during induced bronchoconstriction in six subjects with complete C4-C7 quadriplegia who did not require assisted ventilation. Spirometry, lung volumes, breathing pattern, esophageal pressure (Pes), and dyspnea intensity (Borg Scale) were measured during high-dose methacholine bronchoprovocation up to 256 mg/ml or a maximum change (Delta) in FEV(1) of 50%. Contemporaneous control data from subjects with asthma (n = 12) who had completed the same protocol were used for comparison. At maximum response in quadriplegia, FEV(1) decreased by 1.42 +/- 0.18 L (62 +/- 4%predicted) (mean +/- SEM), and IC decreased by 0.89 +/- 0.12 L (30 +/- 4%predicted). Dyspnea at maximum response was rated "moderate" to "severe": Borg 3.6 +/- 0.3. The predominant qualitative respiratory sensations were inspiratory difficulty and unsatisfied inspiration. The best correlate of dyspnea (Borg) was DeltaIC(%predicted) (p < 0.0005), whereas changes in FEV(1), Pes-derived measurements and breathing pattern did not contribute further to the strength of this relationship. Dyspnea intensity, quality, and changes in spirometry and lung volumes at maximum response were similar to those reported previously in asthma. The relationship between dyspnea intensity and DeltaIC(%predicted) was linear and consistent across groups. We conclude that the quality and intensity of dyspnea during methacholine-induced bronchoconstriction and dynamic hyperinflation was not altered by extensive chest wall deafferentation.
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Affiliation(s)
- M Diane Lougheed
- Respiratory Investigation Unit, Department of Medicine, Queen's University, 102 Stuart Street, Kingston, Ontario, K7L 2V6 Canada.
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15
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Iandelli I, Aliverti A, Kayser B, Dellacà R, Cala SJ, Duranti R, Kelly S, Scano G, Sliwinski P, Yan S, Macklem PT, Pedotti A. Determinants of exercise performance in normal men with externally imposed expiratory flow limitation. J Appl Physiol (1985) 2002; 92:1943-52. [PMID: 11960944 DOI: 10.1152/japplphysiol.00393.2000] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at approximately 1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W(max)) and the difference (Delta) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (VL). From Campbell diagrams, we measured alveolar (PA) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W(di)). Four subjects hyperinflated and two did not. EFL limited performance equally to 65% W(max) with Borg = 9-10 in both. At EFL W(max), inspiratory time (TI) was 0.66s +/- 0.08, expiratory time (TE) 2.12 +/- 0.26 s, Pmus approximately 40 cmH2O and DeltaVL-DeltaVm = 488.7 +/- 74.1 ml. From PA and VL, we calculated compressed gas volume (VC) = 163.0 +/- 4.6 ml. The difference, DeltaVL-DeltaVm-VC (estimated blood volume shift) was 326 ml +/- 66 or 7.2 ml/cmH2O PA. The high Pmus and long TE mimicked a Valsalva maneuver from which the short TI did not allow recovery. Multiple stepwise linear regression revealed that the difference between C and EFL Pmus accounted for 70.3% of the variance in DeltaBorg. DeltaW(di) added 12.5%. We conclude that high expiratory pressures cause severe dyspnea and the possibility of adverse circulatory events, both of which would impair exercise performance.
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Yang M, Hogan SP, Henry PJ, Matthaei KI, McKenzie AN, Young IG, Rothenberg ME, Foster PS. Interleukin-13 mediates airways hyperreactivity through the IL-4 receptor-alpha chain and STAT-6 independently of IL-5 and eotaxin. Am J Respir Cell Mol Biol 2001; 25:522-30. [PMID: 11694459 DOI: 10.1165/ajrcmb.25.4.4620] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Interleukin (IL)-13 is a central mediator of the processes underlying the induction of airways hyperreactivity (AHR) in the allergic lung. However, the mechanisms by which IL-13 induces AHR and the associated role of inflammatory infiltrates as effector cells has not been fully elucidated. In this investigation, we show that intratracheal administration of IL-13 induces AHR in the presence and absence of inflammation. The initial AHR response (peak, 6 to 24 h; preinflammatory phase [PIP]) was dissociated from inflammation (eosinophilia) and mucus hypersecretion but was critically regulated by signaling through the IL-4 receptor alpha chain (IL-4Ralpha) and signal transducers and activators of transcription (STAT)-6. The second response (> 24 h, inflammatory phase [IP]) was characterized by an amplified AHR, eosinophil accumulation, and mucus hypersecretion. These features of the IP were not observed in IL-4Ralpha- or STAT-6-deficient mice. To determine the role of eosinophils in the induction of IP AHR and mucus hypersecretion, we administered IL-13 to IL-5-, eotaxin-, and IL-5/eotaxin- deficient mice. IL-13-mediated eosinophil accumulation was significantly attenuated (but not ablated) in IL-5-, eotaxin-, or IL-5/eotaxin-deficient mice. However, IL-13-induced AHR and mucus secretion occurred independently of IL-5 and/or eotaxin. These findings demonstrate that IL-13 can induce AHR independently of these eosinophil regulatory cytokines and mucus hypersecretion. Furthermore, IL-13-induced AHR, eosinophilia, and mucus production are critically dependent on the IL-4Ralpha chain and STAT-6.
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Affiliation(s)
- M Yang
- Division of Biochemistry and Molecular Biology, The John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia
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Gutteridge JM, Quinlan GJ, Evans TW. The iron paradox of heart and lungs and its implications for acute lung injury. Free Radic Res 2001; 34:439-43. [PMID: 11378527 DOI: 10.1080/10715760100300381] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Iron is an essential requirement for the growth, development, and long term survival of most aerobic organisms. When control over safe iron sequestration is lost or compromised, leading to the release of low molecular mass forms of iron, the heart appears to be particularly sensitive to iron toxicity with cardiomyopathies often developing as a consequence. Iron toxicity, leading to iron-overload, is often treated in humans with the iron chelator desferrioxamine mesylate. Such treatment regimens designed to protect the heart can, however, often lead to lung injury and, in fact, several compounds with known iron chelating properties can induce severe lung dysfunction and injury. Based on these clinical observations and our recent laboratory data, we propose that the lungs actively accumulate reactive forms of iron for use in cellular growth and proliferation, and for the oxidative destruction of microbes, whereas the heart responds in the opposite way by actively removing iron which it finds extremely toxic.
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Affiliation(s)
- J M Gutteridge
- Oxygen Chemistry Laboratory, Directorate of Anaesthesia and Critical Care, Royal Brompton and Harefield NHS Trust, Sydney Street, London, SW3 6NP, UK
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Supinski G, Nethery D, Stofan D, DiMarco A. Extracellular calcium modulates generation of reactive oxygen species by the contracting diaphragm. J Appl Physiol (1985) 1999; 87:2177-85. [PMID: 10601165 DOI: 10.1152/jappl.1999.87.6.2177] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies have indicated that free radicals may play an important role in the development of muscle dysfunction in many pathophysiological conditions. Because the degree of muscle dysfunction observed in some of these conditions appears to be both free radical dependent and modulated by extracellular calcium concentrations, we thought that there may be a link between these two phenomena; i.e., the propensity of a muscle to generate free radicals may be dependent on extracellular calcium concentrations. For this reason, we compared formation of reactive oxygen species (ROS; i.e., free radicals) by electrically stimulated rat diaphragms (trains of 20-Hz stimuli for 10 min, train rate 0.25 trains/s) incubated in organ baths filled with physiological solutions containing low (1 mM), normal (2.5 mM), or high (5 mM) calcium levels. Generation of ROS was assessed by measuring the conversion of hydroethidine to ethidium. We found ROS generation with contraction varied with the extracellular calcium level, with low ROS production (3.18 +/- 0.40 ng ethidium/mg tissue) for low-calcium studies and with much higher ROS generation for normal-calcium (18. 90 +/- 2.70 ng/mg) or high-calcium (19.30 +/- 4.50 ng/mg) studies (P < 0.001). Control, noncontracting diaphragms (in 2.5 mM calcium) had little ROS production (3.40 +/- 0.80 ng/mg; P < 0.001). To further investigate this issue, we added nimodipine (20 microM), an L-type calcium channel blocker, to contracting diaphragms (2.5 mM calcium bath) and found that nimodipine also suppressed ROS formation (2.56 +/- 0.85 ng ethidium/mg tissue). These data indicate that ROS generation by the contracting diaphragm is strongly influenced by extracellular calcium concentrations and may be dependent on calcium transport through L-type calcium channels.
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Affiliation(s)
- G Supinski
- Pulmonary Division, Department of Medicine, Case Western Reserve University and MetroHealth Medical Center, Cleveland, Ohio 44109, USA
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Yan S. Sensation of inspiratory difficulty during inspiratory threshold and hyperinflationary loadings. Effect of inspiratory muscle strength. Am J Respir Crit Care Med 1999; 160:1544-9. [PMID: 10556118 DOI: 10.1164/ajrccm.160.5.9901017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Dynamic hyperinflation loads the inspiratory muscles by increasing end-expiratory lung volume (EELV) and imposing intrinsic positive end-expiratory pressure (PEEPi), the latter behaving as an inspiratory threshold load (ITL). The aim of the current study was to examine how induced-inspiratory muscle fatigue affects the independent effects of the imposed ITL and increasing operating lung volume on the perceived inspiratory difficulty. Dynamic hyperinflation in healthy subjects was induced by positive end-expiratory pressure (PEEP). Increasing operating lung volume alone (without PEEPi) and increasing ITL alone (without change in EELV) were induced by continuous positive airway pressure (CPAP) and external ITL, respectively. Inspiratory difficulty was quantified by the modified Borg scale and analyzed by step forward multiple regression, using the imposed ITL, EELV, and end-inspiratory lung volume (EILV) as independent variables. When fresh, the first entered variable was the imposed ITL (r(2), 0.38). Adding EILV into the model increased r(2) to 0.67. After fatigue, the first entered variable became EILV (r(2), 0.50) and the second selected variable was the imposed ITL, which increased r(2) to 0.66. EELV was insignificant under both conditions. The coefficient of EILV increased significantly from 0.039 +/- 0.005 to 0.092 +/- 0.012 (% inspiratory capacity(-)(1)) after fatigue run (p < 0.001), whereas that of the imposed ITL did not change. It is concluded that in the experimental conditions studied, inspiratory muscle fatigue increased the importance of lung volume over that of inspiratory threshold load in determining the perceived inspiratory difficulty.
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Affiliation(s)
- S Yan
- Meakins-Christie Laboratories, McGill University, Montreal Chest Institute, Royal Victoria Hospital, Montreal, Quebec, Canada
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