Effect of Synchronized Intermittent Mandatory Ventilation on Respiratory Workload in Infants after Cardiac Surgery

2001 ◽  
Vol 95 (4) ◽  
pp. 881-888 ◽  
Author(s):  
Hideaki Imanaka ◽  
Masaji Nishimura ◽  
Hiroshi Miyano ◽  
Hideki Uemura ◽  
Toshikatsu Yagihara
Keyword(s):  
Cardiac Surgery ◽  
Tidal Volume ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Esophageal Pressure ◽  
Intermittent Mandatory Ventilation ◽  
Negative Deflection ◽  
Arterial Blood ◽  
Pressure Time ◽  
Post Cardiac Surgery

Background Synchronized intermittent mandatory ventilation (SIMV) is commonly used in infants and adults. However, few investigations have examined how SIMV reduces respiratory workload in infants. The authors evaluated how infants' changing respiratory patterns when reducing SIMV rate increased respiratory load. The authors also investigated whether SIMV reduces infant respiratory workload in proportion to the rate of mandatory breaths and which rate of SIMV provides respiratory workloads similar to those after tracheal extubation. Methods When 11 post-cardiac surgery infants aged 2-11 months were to be weaned with SIMV, the authors randomly applied five levels of mandatory breathing: 0, 5, 10, 15, and 20 breaths/min. All patients underwent ventilation with SIMV mode: pressure control ventilation, 16 cm H2O; inspiratory time, 0.8 s; triggering sensitivity, 0.6 l/min; and positive endexpiratory pressure, 3 cm H2O. After establishing steady-state conditions at each SIMV rate, arterial blood gases were analyzed, and esophageal pressure, airway pressure, and airflow were measured. Inspiratory work of breathing, pressure-time products, and the negative deflection of esophageal pressure were calculated separately for assisted breaths, for spontaneous breaths, and for total breaths per minute. Measurements were repeated after extubation. Results As the SIMV rate decreased, although minute ventilation and arterial carbon dioxide tension were maintained at constant values, spontaneous breathing rate and tidal volume increased. Work of breathing, pressure-time products, and negative deflection of esophageal pressure increased as the SIMV rate decreased. Work of breathing and pressure-time products after extubation were intermediate between those at a SIMV rate of 5 breaths/min and those at 0 breaths/min. Conclusion When the load to breathing was increased progressively by decreasing the SIMV rate in post-cardiac surgery infants, tidal volume and spontaneous respiratory rate both increased. In addition, work of breathing and pressure-time products were increased depending on the SIMV rate.

Effect of Patient-triggered Ventilation on Respiratory Workload in Infants after Cardiac Surgery

2000 ◽  
Vol 93 (5) ◽  
pp. 1238-1244 ◽  
Author(s):  
Muneyuki Takeuchi ◽  
Hideaki Imanaka ◽  
Hiroshi Miyano ◽  
Keiji Kumon ◽  
Masaji Nishimura
Keyword(s):  
Cardiac Surgery ◽  
Work Of Breathing ◽  
Control Level ◽  
Pressure Control ◽  
Control Mode ◽  
Carbon Dioxide Partial Pressure ◽  
Negative Deflection ◽  
Arterial Blood ◽  
Patient Triggered Ventilation ◽  
Post Cardiac Surgery

Background Patient-triggered ventilation (PTV) is commonly used in adults to avoid dyssynchrony between patient and ventilator. However, few investigations have examined the effects of PTV in infants. Our objective was to determine if pressure-control PTV reduces infants' respiratory workloads in proportion to the level of pressure control. We also explored which level of pressure control provided respiratory workloads similar to those after the extubation of the trachea. Methods When seven post-cardiac surgery infants, aged 1 to 11 months, were to be weaned with the pressure-control PTV, we randomly applied five levels of pressure control: 0, 4, 8, 12, and 16 cm H2O. All patients were ventilated with assist-control mode, triggering sensitivity of 1 l/min, and positive end-expiratory pressure of 3 cm H2O. After establishing steady state conditions at each level of pressure control, arterial blood gases were analyzed and esophageal pressure (Pes), airway pressure, and airflow were measured. Inspiratory work of breathing (WOB) was calculated using a Campbell diagram. A modified pressure-time product (PTPmod) and the negative deflection of Pes were calculated from the Pes tracing below the baseline. The measurement was repeated after extubation. Results Pressure-control PTV supported every spontaneous breath. By decreasing the level of pressure control, respiratory rate increased, tidal volume decreased, and as a result, minute ventilation and arterial carbon dioxide partial pressure were maintained stable. The WOB, PTPmod, and negative deflection of Pes increased as pressure control level was decreased. The WOB and PTPmod at 4 cm H2O pressure control and 0 cm H2O pressure control and after extubation were significantly greater than those at the pressure control of 16, 12, and 8 cm H2O (P < 0.05). The WOB and PTPmod were almost equivalent after extubation and at 4 cm H2O pressure control. Conclusions Work of breathing and PTPmod were changed according to the pressure control level in post-cardiac surgery infants. PTV may be feasible in infants as well as in adults.

scholarly journals Respiratory muscle work compromises leg blood flow during maximal exercise

1997 ◽  
Vol 82 (5) ◽  
pp. 1573-1583 ◽  
Author(s):  
Craig A. Harms ◽  
Mark A. Babcock ◽  
Steven R. McClaran ◽  
David F. Pegelow ◽  
Glenn A. Nickele ◽  
...  
Keyword(s):  
Blood Flow ◽  
Respiratory Muscle ◽  
Maximal Exercise ◽  
Minute Ventilation ◽  
Muscle Blood Flow ◽  
Work Of Breathing ◽  
Esophageal Pressure ◽  
Leg Blood Flow ◽  
Muscle Work ◽  
Arterial Blood

Harms, Craig A., Mark A. Babcock, Steven R. McClaran, David F. Pegelow, Glenn A. Nickele, William B. Nelson, and Jerome A. Dempsey.Respiratory muscle work compromises leg blood flow during maximal exercise. J. Appl. Physiol.82(5): 1573–1583, 1997.—We hypothesized that during exercise at maximal O2 consumption (V˙o 2 max), high demand for respiratory muscle blood flow (Q˙) would elicit locomotor muscle vasoconstriction and compromise limb Q˙. Seven male cyclists (V˙o 2 max 64 ± 6 ml ⋅ kg−1 ⋅ min−1) each completed 14 exercise bouts of 2.5-min duration atV˙o 2 max on a cycle ergometer during two testing sessions. Inspiratory muscle work was either 1) reduced via a proportional-assist ventilator, 2) increased via graded resistive loads, or 3) was not manipulated (control). Arterial (brachial) and venous (femoral) blood samples, arterial blood pressure, leg Q˙ (Q˙legs; thermodilution), esophageal pressure, and O2 consumption (V˙o 2) were measured. Within each subject and across all subjects, at constant maximal work rate, significant correlations existed ( r = 0.74–0.90; P < 0.05) between work of breathing (Wb) and Q˙legs (inverse), leg vascular resistance (LVR), and leg V˙o 2(V˙o 2 legs; inverse), and between LVR and norepinephrine spillover. Mean arterial pressure did not change with changes in Wb nor did tidal volume or minute ventilation. For a ±50% change from control in Wb,Q˙legs changed 2 l/min or 11% of control, LVR changed 13% of control, and O2extraction did not change; thusV˙o 2 legschanged 0.4 l/min or 10% of control. TotalV˙o 2 max was unchanged with loading but fell 9.3% with unloading; thusV˙o 2 legsas a percentage of totalV˙o 2 max was 81% in control, increased to 89% with respiratory muscle unloading, and decreased to 71% with respiratory muscle loading. We conclude that Wb normally incurred during maximal exercise causes vasoconstriction in locomotor muscles and compromises locomotor muscle perfusion andV˙o 2.

scholarly journals Awake prone position reduces work of breathing in patients with COVID-19 ARDS supported by CPAP

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Davide Chiumello ◽  
Elena Chiodaroli ◽  
Silvia Coppola ◽  
Simone Cappio Borlino ◽  
Claudia Granata ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Prone Position ◽  
Supine Position ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Invasive Mechanical Ventilation ◽  
Transpulmonary Pressure ◽  
Esophageal Pressure ◽  
Pressure Time ◽  
Pressure Swing

Abstract Background The use of awake prone position concomitant to non-invasive mechanical ventilation in acute respiratory distress syndrome (ARDS) secondary to COVID-19 has shown to improve gas exchange, whereas its effect on the work of breathing remain unclear. The objective of this study was to evaluate the effects of awake prone position during helmet continuous positive airway pressure (CPAP) ventilation on inspiratory effort, gas exchange and comfort of breathing. Methods Forty consecutive patients presenting with ARDS due to COVID-19 were prospectively enrolled. Gas exchange, esophageal pressure swing (ΔPes), dynamic transpulmonary pressure (dTPP), modified pressure time product (mPTP), work of breathing (WOB) and comfort of breathing, were recorded on supine position and after 3 h on prone position. Results The median applied PEEP with helmet CPAP was 10 [8–10] cmH2O. The PaO2/FiO2 was higher in prone compared to supine position (Supine: 166 [136–224] mmHg, Prone: 314 [232–398] mmHg, p < 0.001). Respiratory rate and minute ventilation decreased from supine to prone position from 20 [17–24] to 17 [15–19] b/min (p < 0.001) and from 8.6 [7.3–10.6] to 7.7 [6.6–8.6] L/min (p < 0.001), respectively. Prone position did not reduce ΔPes (Supine: − 7 [− 9 to − 5] cmH2O, Prone: − 6 [− 9 to − 5] cmH2O, p = 0.31) and dTPP (Supine: 17 [14–19] cmH2O, Prone: 16 [14–18] cmH2O, p = 0.34). Conversely, mPTP and WOB decreased from 152 [104–197] to 118 [90–150] cmH2O/min (p < 0.001) and from 146 [120–185] to 114 [95–151] cmH2O L/min (p < 0.001), respectively. Twenty-six (65%) patients experienced a reduction in WOB of more than 10%. The overall sensation of dyspnea was lower in prone position (p = 0.005). Conclusions Awake prone position with helmet CPAP enables a reduction in the work of breathing and an improvement in oxygenation in COVID-19-associated ARDS.

Ontogeny of respiratory control and pulmonary mechanics in newborn rabbits

1985 ◽  
Vol 59 (5) ◽  
pp. 1477-1486 ◽  
Author(s):  
M. M. Grunstein ◽  
D. T. Tanaka
Keyword(s):  
Mechanical Properties ◽  
Tidal Volume ◽  
Respiratory System ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Relative Volume ◽  
Respiratory Pattern ◽  
Pulmonary Mechanics ◽  
Volume Loss ◽  
Age Related

Maturation of the respiratory pattern and the active and passive mechanical properties of the respiratory system were assessed in 19 tracheotomized rabbits (postnatal age range: 1–26 days) placed in a body plethysmograph. With maturation both minute ventilation and tidal volume significantly increased, whereas respiratory frequency decreased. When normalized for body weight (kg) both the passive (Rrs X kg) and active (R'rs X kg) resistances of the respiratory system significantly increased with age, whereas the corresponding passive (Crs X kg-1) and active (C'rs X kg-1) compliances significantly decreased. At any given age R'rs X kg only slightly exceeded Rrs X kg, whereas C'rs X kg-1 was significantly lower than Crs X kg-1. Moreover, the maturational increases in Rrs X kg and R'rs X kg exceeded the corresponding decreases in Crs X kg-1 and C'rs X kg-1, resulting in significant age-related increases in both the passive (tau rs) and active (tau'rs) time constants of the respiratory system. Due to the age-related increases in tau'rs, producing a delayed volume response to any given inspiratory driving pressure, the relative volume loss obtained at any time during inspiration was greater in the maturing rabbit. On the other hand, because of concomitant compensatory changes in respiratory pattern, evidenced by increases in inspiratory duration with age, the end-inspiratory tidal volume loss in the maturing animal was maintained generally less than 10% at all postnatal ages. Thus maturational changes in respiratory pattern appear coupled to changes in the active mechanical properties of the respiratory system. The latter coupling serves to optimize the transduction of inspiratory pressure into volume change in a manner consistent with establishing the minimum inspiratory work of breathing during postnatal development.

scholarly journals Pulmonary Mechanics and the Work of Breathing in the Lizard, Gekko Gecko

1984 ◽  
Vol 113 (1) ◽  
pp. 187-202 ◽  
Author(s):  
WILLIAM K. MILSOM ◽  
TIMOTHY Z. VITALIS
Keyword(s):  
Tidal Volume ◽  
Chest Wall ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Body Cavity ◽  
The Body ◽  
Pulmonary Mechanics ◽  
Lung Inflation ◽  
Gekko Gecko ◽  
Tokay Gecko

Measurements of pulmonary mechanics made on anaesthetized specimens of the Tokay gecko Gekkogecko (Linné), indicate that both static and dynamic pulmonary mechanics are dominated by the mechanics of the body cavity and chest wall. The lungs are relatively large and compliant and offer little resistance to air flow at any of the ventilation frequencies (f) used in this study. The body wall is relatively stiff and becomes less compliant with increasing ventilation frequency and with increasing tidal volume (VT) at the higher frequencies. The vast majority of the work performed in breathing is used to overcome elastic forces in the chest wall resisting lung inflation. This work increases exponentially with increases in volume. As a consequence, in terms of total ventilation, the most economic breathing pattern is a high frequency, low tidal volume pattern in which changes in minute ventilation (VE) are most economically produced solely by changes in f. Because reductions in tidal volume drastically reduce alveolar ventilation volume while dead space remains constant, the same arguments do not apply to alveolar minute ventilation (VA). In terms of alveolar minute ventilation, there is an optimum combination of f and VT for each level of VA, with changes in VA being most economically produced by almost equal changes in both f and VT

Measurement of Pressure–Time Product during Spontaneous Assisted Breathing by Rapid Interrupter Technique

2007 ◽  
Vol 106 (3) ◽  
pp. 484-490 ◽  
Author(s):  
Giacomo Bellani ◽  
Nicolò Patroniti ◽  
Dieter Weismann ◽  
Lucia Galbiati ◽  
Francesco Curto ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Pressure Support ◽  
Work Of Breathing ◽  
Ventilatory Support ◽  
Respiratory Muscles ◽  
Esophageal Pressure ◽  
Assisted Ventilation ◽  
Reliable Estimate ◽  
Pressure Time ◽  
Pressure Time Product

Background Measuring the work of breathing of patients undergoing spontaneous assisted ventilation can be useful to monitor and titrate ventilatory support. The aim of this study was to obtain measurements of the pressure generated by the respiratory muscles (PMUSC) and the derived pressure-time product (PTP; a good indicator of the metabolic work of breathing), performing the rapid interrupter technique with a commercial ventilator. Methods A Draeger Evita 4 ventilator (Draeger Medical, Lubeck, Germany) was controlled by a personal computer to rapidly interrupt the airway flow at different times and volumes of the respiratory cycle during pressure-support ventilation. From the airway pressure tracing after the occlusion, the authors estimated the alveolar pressure and PMUSC; the integration of PMUSC values over the inspiratory time yields the measurement of PTP. Esophageal pressure measurements were used as a reference. After a bench study of the valves' performance, the authors performed 11 measurement sequences in eight patients. Results The closure times for the inspiratory and expiratory valves were 74 +/- 10 and 61 +/- 13 ms, respectively. The interrupter technique provided a reliable estimate of PMUSC (PMUSC, occl = 1.00 . PMUSC, pes + 0.19; r = 0.88; 95% confidence interval for agreement, +5.49/-5.32 cm H2O). PTPoccl tightly correlated with PTPpes (PTPoccl = 0.95 . PTPpes + 0.13; r = 0.96; 95% confidence interval, 1.94/-1.61 cm H2O . s). Conclusion The rapid interrupter technique can be performed by means of a commercial ventilator, providing reliable measurement of PMUSC and PTP.

The Effect of Temperature and Hypoxia Hypercapnia on the Respiratory Pattern of the Unrestrained Lizard, Pogona Vitticeps

1995 ◽  
Vol 43 (2) ◽  
pp. 165 ◽  
Author(s):  
S Crafter ◽  
MI Soldini ◽  
CB Daniels ◽  
AW Smits
Keyword(s):  
Tidal Volume ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Average Frequency ◽  
Respiratory Pattern ◽  
Effect Of Temperature ◽  
Breath Holding ◽  
Breathing Patterns ◽  
Pogona Vitticeps ◽  
Lower Temperature

The effect of altering body temperature and the oxygen and carbon dioxide composition of inspired air on the respiratory pattern of the unrestrained lizard Pogona vitticeps was determined using pneumotachometry that did not require restraining the animal. P. vitticeps demonstrated a typical reptilian breathing pattern of groups of breaths separated by periods of breath-holding. Respiratory patterns were measured at 18 degrees C and at 37 degrees C. Minute ventilation decreased at the lower temperature as a result of a decrease in average frequency. Tidal volume was temperature independent. The change in average frequency resulted from both a decrease in the instantaneous inspiratory time and an increase in the time spent in a non-ventilatory period. As a result, the work of breathing was less at 18 degrees C than at 37 degrees C. With the exception of tidal volume, breathing patterns were independent of changes to the composition of inspired air. At both 18 degrees C and 37 degrees C, inspiring a 5% CO2/13% O-2/82% N-2 gas mixture increased tidal volume but did not increase minute ventilation.

scholarly journals Increased respiratory neural drive and work of breathing in exercise-induced laryngeal obstruction

2018 ◽  
Vol 124 (2) ◽  
pp. 356-363 ◽  
Author(s):  
Emil S. Walsted ◽  
Azmy Faisal ◽  
Caroline J. Jolley ◽  
Laura L. Swanton ◽  
Matthew J. Pavitt ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Respiratory Mechanics ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Neural Drive ◽  
Exertional Dyspnea ◽  
Laryngeal Obstruction ◽  
Laryngeal Closure ◽  
Endoscopic Video ◽  
Exercise Induced

Exercise-induced laryngeal obstruction (EILO), a phenomenon in which the larynx closes inappropriately during physical activity, is a prevalent cause of exertional dyspnea in young individuals. The physiological ventilatory impact of EILO and its relationship to dyspnea are poorly understood. The objective of this study was to evaluate exercise-related changes in laryngeal aperture on ventilation, pulmonary mechanics, and respiratory neural drive. We prospectively evaluated 12 subjects (6 with EILO and 6 healthy age- and gender-matched controls). Subjects underwent baseline spirometry and a symptom-limited incremental exercise test with simultaneous and synchronized recording of endoscopic video and gastric, esophageal, and transdiaphragmatic pressures, diaphragm electromyography, and respiratory airflow. The EILO and control groups had similar peak work rates and minute ventilation (V̇e) (work rate: 227 ± 35 vs. 237 ± 35 W; V̇e: 103 ± 20 vs. 98 ± 23 l/min; P > 0.05). At submaximal work rates (140–240 W), subjects with EILO demonstrated increased work of breathing ( P < 0.05) and respiratory neural drive ( P < 0.05), developing in close temporal association with onset of endoscopic evidence of laryngeal closure ( P < 0.05). Unexpectedly, a ventilatory increase ( P < 0.05), driven by augmented tidal volume ( P < 0.05), was seen in subjects with EILO before the onset of laryngeal closure; there were however no differences in dyspnea intensity between groups. Using simultaneous measurements of respiratory mechanics and diaphragm electromyography with endoscopic video, we demonstrate, for the first time, increased work of breathing and respiratory neural drive in association with the development of EILO. Future detailed investigations are now needed to understand the role of upper airway closure in causing exertional dyspnea and exercise limitation. NEW & NOTEWORTHY Exercise-induced laryngeal obstruction is a prevalent cause of exertional dyspnea in young individuals; yet, how laryngeal closure affects breathing is unknown. In this study we synchronized endoscopic video with respiratory physiological measurements, thus providing the first detailed commensurate assessment of respiratory mechanics and neural drive in relation to laryngeal closure. Laryngeal closure was associated with increased work of breathing and respiratory neural drive preceded by an augmented tidal volume and a rise in minute ventilation.

scholarly journals Ventilatory baroreflex sensitivity in humans is not modulated by chemoreflex activation

2011 ◽  
Vol 300 (4) ◽  
pp. H1492-H1500 ◽  
Author(s):  
Julian M. Stewart ◽  
Eileen Rivera ◽  
Debbie A. Clarke ◽  
Ila L. Baugham ◽  
Anthony J. Ocon ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Tidal Volume ◽  
Healthy Subjects ◽  
Baroreflex Sensitivity ◽  
Minute Ventilation ◽  
Peripheral Resistance ◽  
Operating Point ◽  
Intravenous Bolus ◽  
Experimental Animals ◽  
Arterial Blood

Increasing arterial blood pressure (AP) decreases ventilation, whereas decreasing AP increases ventilation in experimental animals. To determine whether a “ventilatory baroreflex” exists in humans, we studied 12 healthy subjects aged 18–26 yr. Subjects underwent baroreflex unloading and reloading using intravenous bolus sodium nitroprusside (SNP) followed by phenylephrine (“Oxford maneuver”) during the following “gas conditions:” room air, hypoxia (10% oxygen)-eucapnia, and 30% oxygen-hypercapnia to 55–60 Torr. Mean AP (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), expiratory minute ventilation (VE), respiratory rate (RR), and tidal volume were measured. After achieving a stable baseline for gas conditions, we performed the Oxford maneuver. VE increased from 8.8 ± 1.3 l/min in room air to 14.6 ± 0.8 l/min during hypoxia and to 20.1 ± 2.4 l/min during hypercapnia, primarily by increasing tidal volume. VE doubled during SNP. CO increased from 4.9 ± .3 l/min in room air to 6.1 ± .6 l/min during hypoxia and 6.4 ± .4 l/min during hypercapnia with decreased TPR. HR increased for hypoxia and hypercapnia. Sigmoidal ventilatory baroreflex curves of VE versus MAP were prepared for each subject and each gas condition. Averaged curves for a given gas condition were obtained by averaging fits over all subjects. There were no significant differences in the average fitted slopes for different gas conditions, although the operating point varied with gas conditions. We conclude that rapid baroreflex unloading during the Oxford maneuver is a potent ventilatory stimulus in healthy volunteers. Tidal volume is primarily increased. Ventilatory baroreflex sensitivity is unaffected by chemoreflex activation, although the operating point is shifted with hypoxia and hypercapnia.

Sex differences in the resistive and elastic work of breathing during exercise in endurance-trained athletes

2009 ◽  
Vol 297 (1) ◽  
pp. R166-R175 ◽  
Author(s):  
Jordan A. Guenette ◽  
Jordan S. Querido ◽  
Neil D. Eves ◽  
Romeo Chua ◽  
A. William Sheel
Keyword(s):  
Sex Differences ◽  
Body Mass ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Esophageal Pressure ◽  
Work Rate ◽  
Mass Ratio ◽  
Volume Data ◽  
Exercising Women ◽  
Body Mass Ratio

It is not known whether the high total work of breathing (WOB) in exercising women is higher due to differences in the resistive or elastic WOB. Accordingly, the purpose of this study was to determine which factors contribute to the higher total WOB during exercise in women. We performed a comprehensive analysis of previous data from 16 endurance-trained subjects (8 men and 8 women) that underwent a progressive cycle exercise test to exhaustion. Esophageal pressure, lung volumes, and ventilatory parameters were continuously monitored throughout exercise. Modified Campbell diagrams were used to partition the esophageal-pressure volume data into inspiratory and expiratory resistive and elastic components at 50, 75, 100 l/min and maximal ventilations and also at three standardized submaximal work rates (3.0, 3.5, and 4.0 W/kg). The total WOB was also compared between sexes at relative submaximal ventilations (25, 50, and 75% of maximal ventilation). The inspiratory resistive WOB at 50, 75, and 100 l/min was 67, 89, and 109% higher in women, respectively ( P < 0.05). The expiratory resistive WOB was 131% higher in women at 75 l/min ( P < 0.05) with no differences at 50 or 100 l/min. There were no significant sex differences in the inspiratory or expiratory elastic WOB across any absolute minute ventilation. However, the total WOB was 120, 60, 50, and 45% higher in men at 25, 50, 75, and 100% of maximal exercise ventilation, respectively ( P < 0.05). This was due in large part to their much higher tidal volumes and thus higher inspiratory elastic WOB. When standardized for a given work rate to body mass ratio, the total WOB was significantly higher in women at 3.5 W/kg (239 ± 31 vs. 173 ± 12 J/min, P < 0.05) and 4 W/kg (387 ± 53 vs. 243 ± 36 J/min, P < 0.05), and this was due exclusively to a significantly higher inspiratory and expiratory resistive WOB rather than differences in the elastic WOB. The higher total WOB in women at absolute ventilations and for a given work rate to body mass ratio is due to a substantially higher resistive WOB, and this is likely due to smaller female airways relative to males and a breathing pattern that favors a higher breathing frequency.

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