Pulmonary mechanisms and work of breathing at maximal ventilation and raised air pressure

1981 ◽  
Vol 50 (4) ◽  
pp. 747-753 ◽  
Author(s):  
C. M. Hesser ◽  
D. Linnarsson ◽  
L. Fagraeus
Keyword(s):  
Maximal Exercise ◽  
Work Of Breathing ◽  
Pulmonary Ventilation ◽  
Transpulmonary Pressure ◽  
Air Pressure ◽  
Lung Volumes ◽  
Gas Density ◽  
Peak Flows ◽  
Inspiratory Muscles ◽  
Exercise Ventilation

Pulmonary ventilation (V) and the interrelationships of airflow, transpulmonary pressure, and lung volume during inspiration and expiration were studied in eight healthy subjects who performed maximal exercise (MEx; 140% VO2 max), 15-s maximal voluntary ventilation (MVV), and forced inspiratory and expiratory vital capacity (FVC) maneuvers at 1, 3, and 6 ATA. Maximal exercise ventilation and MVV amounted to 149 +/- 7 (mean +/- SE) and 193 +/- 9 l . min-1, respectively, at 1 ATA and were both reduced by approximately 37% at 3 ATA and by 50% at 6 ATA. Expiratory peak flows during MEx and MVV were equal to the maximal flows obtained during FVC at comparable lung volumes, whereas inspiratory peak flows during MEx were 20% less than the FVC flows. Despite a sixfold increase in gas density, the rate of mechanical work of breathing decreased when the pressure was raised to 6 ATA, during MEx from 8 +/- 1 to 6 +/- 1 W, and during MVV from 28 +/- 5 to 18 +/- 3 W. With increasing gas density there was a shift of lung volumes in the inspiratory direction with consequent reductions of inspiratory-to-expiratory flow ratios. We conclude that depletion of energy stores in the inspiratory muscles contributed to limiting V during MEx at raised air pressure.

Hypoxic ventilatory response and arterial desaturation during heavy work

1989 ◽  
Vol 67 (3) ◽  
pp. 1119-1124 ◽  
Author(s):  
S. R. Hopkins ◽  
D. C. McKenzie
Keyword(s):  
Maximal Exercise ◽  
Ventilatory Response ◽  
Pulmonary Ventilation ◽  
Ideal Gas ◽  
Respiratory Drive ◽  
O2 Uptake ◽  
Arterial Blood ◽  
Arterial Desaturation ◽  
Exercise Ventilation ◽  
Arterial O2 Saturation

Arterial desaturation in athletes during intense exercise has been reported by several authors, yet the etiology of this phenomenon remains obscure. Inadequate pulmonary ventilation, due to a blunted respiratory drive, has been implicated as a factor. To investigate the relationship between the ventilatory response to hypoxia, exercise ventilation, and arterial desaturation, 12 healthy male subjects [age, 23.8 +/- 3.6 yr; height, 181.6 +/- 5.6 cm; weight, 73.7 +/- 6.2 kg; and maximal O2 uptake (VO2max), 63.0 +/- 2.2 ml.kg-1 min-1] performed a 5-min treadmill test at 100% of VO2max, during which arterial blood samples and ventilatory data were collected every 15 s. Alveolar PO2 (PAO2) was determined using the ideal gas equation. On a separate occasion the ventilatory response to isocapnic hypoxia was measured. Arterial PO2 decreased by an average of 29 Torr during the test, associated with arterial desaturation [arterial O2 saturation (SaO2) 92.0%]. PAO2 was maintained; however, alveolar-arterial gas pressure difference increased progressively to greater than 40 Torr. Minimal hypocapnia was observed, despite marked metabolic acidosis. There was no significant correlation observed between hypoxic drives and ventilation-to-O2 uptake ratio or SaO2 (r = 0.1 and 0.06, respectively, P = NS). These data support the conclusions that hypoxic drives are not related to maximal exercise ventilation or to the development of arterial desaturation during maximal exercise.

Diaphragmatic perfusion heterogeneity during exercise with inspiratory resistive breathing

1990 ◽  
Vol 68 (5) ◽  
pp. 2177-2181 ◽  
Author(s):  
M. Manohar
Keyword(s):  
Blood Flow ◽  
Exercise Capacity ◽  
Vascular Resistance ◽  
Maximal Exercise ◽  
Perfusion Pressure ◽  
Work Of Breathing ◽  
Regional Distribution ◽  
Resistive Breathing ◽  
Exercise Induced

Regional distribution of diaphragmatic blood flow (Q; 15-microns-diam radionuclide-labeled microspheres) was studied in normal (n = 7) and laryngeal hemiplegic (LH; n = 7) ponies to determine whether the added stress of inspiratory resistive breathing during maximal exercise may cause 1) redistribution of diaphragmatic Q and 2) crural diaphragmatic Q to exceed that in maximally exercising normal ponies. LH-induced augmentation of already high exertional work of breathing resulted in diminished locomotor exercise capacity so that maximal exercise in LH ponies occurred at 25 km/h compared with 32 km/h for normal ponies. The costal and crural regions received similar Q in both groups at rest. However, exercise-induced increments in perfusion were significantly greater in the costal region of the diaphragm. At 25 km/h, costal diaphragmatic perfusion was 154 and 143% of the crural diaphragmatic Q in normal and LH ponies. At 32 km/h, Q in costal diaphragm of normal ponies was 136% of that in the crural region. Costal and crural diaphragmatic Q in LH ponies exercised at 25 km/h exceeded that for normal ponies but was similar to the latter during exercise at 32 km/h. Perfusion pressure for the three conditions was also similar. It is concluded that diaphragmatic perfusion heterogeneity in exercising ponies was preserved during the added stress of inspiratory resistive breathing. It was also demonstrated that vascular resistance in the crural and costal regions of the diaphragm in maximally exercised LH ponies remained similar to that in maximally exercising normal ponies.

scholarly journals Thoracic weighting of restrained subjects during exhaustion recovery causes loss of lung reserve volume in a model of police arrest

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mark Campbell ◽  
Roslyn Dakin ◽  
Symon Stowe ◽  
Kira Burton ◽  
Brianna Raven ◽  
...  
Keyword(s):  
Electrical Impedance ◽  
Human Subjects ◽  
Work Of Breathing ◽  
High Sensitivity ◽  
Abdominal Muscle ◽  
Combined Effects ◽  
Impedance Tomography ◽  
Head Restraint ◽  
Inspiratory Muscles ◽  
Life Threatening

AbstractRestraint asphyxia has been proposed as a mechanism for some arrest-related deaths that occur during or shortly after a suspect is taken into custody. Our analysis of the literature found that prone positioning, weight applied to the back, recovery after simulated pursuit, and restraint position have led to restrictive, but non life-threatening respiratory changes when tested in subsets. However, the combined effects of all four parameters have not been tested together in a single study. We hypothesized that a complete protocol with high-sensitivity instrumentation could improve our understanding of breathing physiology during weighted restraint. We designed an electrical impedance tomography (EIT)-based protocol for this purpose and measured the 3D distribution of ventilation within the thorax. Here, we present the results from a study on 17 human subjects that revealed FRC declines during weighted restrained recovery from exercise for subjects in the restraint postures, but not the control posture. These prolonged FRC declines were consistent with abdominal muscle recruitment to assist the inspiratory muscles, suggesting that subjects in restraint postures have increased work of breathing compared to controls. Upon removal of the weighted load, lung reserve volumes gradually increased for the hands-behind-the-head restraint posture but continued to decrease for subjects in the hands-behind-the-back restraint posture. We discuss the possible role this increased work of breathing may play in restraint asphyxia.

scholarly journals Sex differences in the intensity and qualitative dimensions of exertional dyspnea in physically active young adults

2015 ◽  
Vol 119 (9) ◽  
pp. 998-1006 ◽  
Author(s):  
Julia M. Cory ◽  
Michele R. Schaeffer ◽  
Sabrina S. Wilkie ◽  
Andrew H. Ramsook ◽  
Joseph H. Puyat ◽  
...  
Keyword(s):  
Sex Differences ◽  
Maximal Exercise ◽  
Peak Exercise ◽  
Breathing Patterns ◽  
Work Effort ◽  
Exertional Dyspnea ◽  
Lung Volumes ◽  
Physically Active ◽  
Shallow Breathing ◽  
Active Adults

Understanding sex differences in the qualitative dimensions of exertional dyspnea may provide insight into why women are more affected by this symptom than men. This study explored the evolution of the qualitative dimensions of dyspnea in 70 healthy, young, physically active adults (35 M and 35 F). Participants rated the intensity of their breathing discomfort (Borg 0-10 scale) and selected phrases that best described their breathing from a standardized list (work/effort, unsatisfied inspiration, and unsatisfied expiration) throughout each stage of a symptom-limited incremental-cycle exercise test. Following exercise, participants selected phrases that described their breathing at maximal exercise from a list of 15 standardized phrases. Intensity of breathing discomfort was significantly higher in women for a given ventilation, but differences disappeared when ventilation was expressed as a percentage of maximum voluntary ventilation. The dominant qualitative descriptor in both sexes throughout exercise was increased work/effort of breathing. At peak exercise, women were significantly more likely to select the following phrases: “my breathing feels shallow,” “I cannot get enough air in,” “I cannot take a deep breath in,” and “my breath does not go in all the way.” Women adopted a more rapid and shallow breathing pattern and had significantly higher end-inspiratory lung volumes relative to total lung capacity throughout exercise relative to men. These findings suggest that men and women do not differ in their perceived quality of dyspnea during submaximal exercise, but subjective differences appear at maximal exercise and may be related, at least in part, to underlying sex differences in breathing patterns and operating lung volumes during exercise.

Nonlinear increases in diffusing capacity during exercise by seated and supine subjects

1981 ◽  
Vol 51 (4) ◽  
pp. 858-863 ◽  
Author(s):  
D. L. Stokes ◽  
N. R. MacIntyre ◽  
J. A. Nadel
Keyword(s):  
Carbon Monoxide ◽  
Oxygen Consumption ◽  
Healthy Subjects ◽  
Vital Capacity ◽  
Maximal Exercise ◽  
Sitting Position ◽  
Diffusing Capacity ◽  
Heavy Exercise ◽  
Lung Volumes ◽  
Rate Of Increase

To study the effects of exercise on pulmonary diffusing capacity, we measured the lungs' diffusing capacity for carbon monoxide (DLCO) during exhalation from 30 to 45% exhaled vital capacity in eight healthy subjects at rest and during exercise while both sitting and supine. We found that DLCO at these lung volumes in resting subjects was 26.3 +/- 3.2% (mean +/- SE) higher in the supine than in the sitting position (P less than 0.001). We also found that, in both positions, DLCO at these lung volumes increased significantly (P less than 0.001) with increasing exercise and approached similar values at maximal exercise. The pattern of increase in DLCO with an increase in oxygen consumption in both positions was curvilinear in that the rate of increase in DLCO during mild exercise was greater than the rate of increase in DLCO during heavy exercise (P = 0.02). Furthermore, in the supine position during exercise, it appeared that DLCO reached a physiological maximum.

Lung Volumes, Pulmonary Ventilation, and Hypoxia Following Rapid Decompression to 60,000 ft (18,288 m)

2013 ◽  
Vol 84 (6) ◽  
pp. 551-559
Author(s):  
Desmond M. Connolly ◽  
Timothy J. D’Oyly ◽  
Amanda S. McGown ◽  
Vivienne M. Lee
Keyword(s):  
Pulmonary Ventilation ◽  
Lung Volumes ◽  
Rapid Decompression

Inflection point on transpulmonary pressure-volume curves and closing volume

1975 ◽  
Vol 38 (2) ◽  
pp. 228-235 ◽  
Author(s):  
M. Demedts ◽  
J. Clement ◽  
D. C. Stanescu ◽  
K. P. van de Woestijne
Keyword(s):  
Inflection Point ◽  
Vital Capacity ◽  
Transpulmonary Pressure ◽  
Bronchial Obstruction ◽  
Closing Volume ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Space Effect ◽  
Washout Curves

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express “airway closure,” their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

High lung volume increases stress failure in pulmonary capillaries

1992 ◽  
Vol 73 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Z. Fu ◽  
M. L. Costello ◽  
K. Tsukimoto ◽  
R. Prediletto ◽  
A. R. Elliott ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Lung Volume ◽  
Autologous Blood ◽  
Physiological Mechanism ◽  
Transpulmonary Pressure ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Pulmonary Capillaries ◽  
Scanning Electron

We previously showed that when pulmonary capillaries in anesthetized rabbits are exposed to a transmural pressure (Ptm) of approximately 40 mmHg, stress failure of the walls occurs with disruption of the capillary endothelium, alveolar epithelium, or sometimes all layers. The present study was designed to test whether stress failure occurred more frequently at high than at low lung volumes for the same Ptm. Lungs of anesthetized rabbits were inflated to a transpulmonary pressure of 20 cmH2O, perfused with autologous blood at 32.5 or 2.5 cmH2O Ptm, and fixed by intravascular perfusion. Samples were examined by both transmission and scanning electron microscopy. The results were compared with those of a previous study in which the lung was inflated to a transpulmonary pressure of 5 cmH2O. There was a large increase in the frequency of stress failure of the capillary walls at the higher lung volume. For example, at 32.5 cmH2O Ptm, the number of endothelial breaks per millimeter cell lining was 7.1 +/- 2.2 at the high lung volume compared with 0.7 +/- 0.4 at the low lung volume. The corresponding values for epithelium were 8.5 +/- 1.6 and 0.9 +/- 0.6. Both differences were significant (P less than 0.05). At 52.5 cmH2O Ptm, the results for endothelium were 20.7 +/- 7.6 (high volume) and 7.1 +/- 2.1 (low volume), and the corresponding results for epithelium were 32.8 +/- 11.9 and 11.4 +/- 3.7. At 32.5 cmH2O Ptm, the thickness of the blood-gas barrier was greater at the higher lung volume, consistent with the development of more interstitial edema. Ballooning of the epithelium caused by accumulation of edema fluid between the epithelial cell and its basement membrane was seen at 32.5 and 52.5 cmH2O Ptm. At high lung volume, the breaks tended to be narrower and fewer were oriented perpendicular to the axis of the pulmonary capillaries than at low lung volumes. Transmission and scanning electron microscopy measurements agreed well. Our findings provide a physiological mechanism for other studies showing increased capillary permeability at high states of lung inflation.

scholarly journals Variations in exercise ventilation in hypoxia will affect oxygen uptake

2020 ◽  
Vol 107 (3) ◽  
pp. 431-443
Author(s):  
J.A. Loeppky ◽  
R.M. Salgado ◽  
A.C. Sheard ◽  
D.O. Kuethe ◽  
C.M. Mermier
Keyword(s):  
Individual Variation ◽  
Ambient Pressure ◽  
Work Of Breathing ◽  
Linear Equations ◽  
Mechanical Efficiency ◽  
Individual Response ◽  
Hypoxic Ventilatory Response ◽  
Gross Efficiency ◽  
Exercise Ventilation ◽  
Progressive Exercise

AbstractReports of VO2 response differences between normoxia and hypoxia during incremental exercise do not agree. In this study VO2 and VE were obtained from 15-s averages at identical work rates during continuous incremental cycle exercise in 8 subjects under ambient pressure (633 mmHg ≈1,600 m) and during duplicate tests in acute hypobaric hypoxia (455 mmHg ≈4,350 m), ranging from 49 to 100% of VO2 peak in hypoxia and 42–87% of VO2 peak in normoxia. The average VO2 was 96 mL/min (619 mL) lower at 455 mmHg (n.s. P = 0.15) during ramp exercises. Individual response points were better described by polynomial than linear equations (mL/min/W). The VE was greater in hypoxia, with marked individual variation in the differences which correlated significantly and directly with the VO2 difference between 455 mmHg and 633 mmHg (P = 0.002), likely related to work of breathing (Wb). The greater VE at 455 mmHg resulted from a greater breathing frequency. When a subject's hypoxic ventilatory response is high, the extra work of breathing reduces mechanical efficiency (E). Mean ∆E calculated from individual linear slopes was 27.7 and 30.3% at 633 and 455 mmHg, respectively (n.s.). Gross efficiency (GE) calculated from mean VO2 and work rate and correcting for Wb from a VE–VO2 relationship reported previously, gave corresponding values of 20.6 and 21.8 (P = 0.05). Individual variation in VE among individuals overshadows average trends, as also apparent from other reports comparing hypoxia and normoxia during progressive exercise and must be considered in such studies.

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