Relation between respiratory neural output and tidal volume

We recently described a model for the relation between respiratory neural and mechanical outputs (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 963–1001, 1981). In this communication we utilize the model to address the following questions. 1) How sensitive is tidal volume (VT) to shape and timing of respiratory neural output (N)? 2) How effective are shape and timing characteristics of N in load compensation? 3) For a given VT, what is the most economical shape and timing of N? Using different values of passive respiratory mechanics, we generated the VT profiles associated with theoretical N waveforms having different shape and timing parameters. We found that 1) with normal mechanics VT is moderately sensitive to inspiratory time (TI) but not to shape of N, whereas with high resistance and short TI, VT is very sensitive to shape and timing; 2) changes in shape, within the physiological range, can serve as potent load-compensatory mechanisms; and 3) for a given VT, the most economical (lowest mean pressure) N pattern is one with a very short TI and a rising phase that is convex to time axis. This holds true even with high resistance.

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Diaphragm and lung afferents contribute to inspiratory load compensation in awake ponies

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.3.1330 ◽

1994 ◽

Vol 76 (3) ◽

pp. 1330-1339 ◽

Cited By ~ 14

Author(s):

H. V. Forster ◽

T. F. Lowry ◽

L. G. Pan ◽

B. K. Erickson ◽

M. J. Korducki ◽

...

Keyword(s):

Tidal Volume ◽

Treadmill Exercise ◽

Minute Ventilation ◽

Inspiratory Time ◽

Arterial Pco2 ◽

Load Compensation ◽

Expiratory Time ◽

Inspiratory Load

We determined the effect of pulmonary vagal (hilar nerve) denervation (HND) and diaphragm deafferentation (DD) on inspiratory load compensation. We studied awake intact (I; n = 10), DD (n = 5), HND (n = 4), and DD+HND (n = 7) ponies at rest and during mild (1.8 mph, 5% grade) and moderate (1.8 mph, 15% grade) treadmill exercise before, during, and after resistance of the inspiratory circuit was increased from approximately 1.5 to approximately 20 cmH2O.l–1.s. During the first loaded breath in I ponies at rest, inspiratory time (TI) increased, expiratory time decreased, and inspiratory drive increased. There were minimal changes after the first breath, and inspiratory minute ventilation (VI) and arterial PCO2 did not change (P > 0.10) from control values. On the first loaded breath during exercise, TI increased but inspiratory drive either did not change or decreased from control values. TI and drive increased after the first breath, but the increases were insufficient to maintain VI and arterial PCO2 at control levels. First-breath load compensation remained after DD, HND, and DD+HND, but after DD+HND tidal volume and VI were compensated 5–10% less (P < 0.05) than in I ponies. In all groups inspiratory drive, tidal volume, and VI were markedly augmented on the first breath after loading was terminated with a gradual return toward control. We conclude that diaphragm and pulmonary afferents contribute to but are not essential for inspiratory load compensation in awake ponies.

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Biologically Variable Ventilation Improves Oxygenation and Respiratory Mechanics during One-lung Ventilation

Anesthesiology ◽

10.1097/00000542-200607000-00017 ◽

2006 ◽

Vol 105 (1) ◽

pp. 91-97 ◽

Cited By ~ 26

Author(s):

Michael C. McMullen ◽

Linda G. Girling ◽

M Ruth Graham ◽

W Alan C. Mutch

Keyword(s):

Tidal Volume ◽

Respiratory Mechanics ◽

Lung Ventilation ◽

Group Effect ◽

Shunt Fraction ◽

Static Compliance ◽

One Lung Ventilation ◽

Time Interaction ◽

Variable Ventilation ◽

Dead Space Ventilation

Background Hypoxemia is common during one-lung ventilation (OLV). Atelectasis contributes to the problem. Biologically variable ventilation (BVV), using microprocessors to reinstitute physiologic variability to respiratory rate and tidal volume, has been shown to be advantageous over conventional monotonous control mode ventilation (CMV) in improving oxygenation during the period of lung reinflation after OLV in an experimental model. Here, using a porcine model, the authors compared BVV with CMV during OLV to assess gas exchange and respiratory mechanics. Methods Eight pigs (25-30 kg) were studied in each of two groups. After induction of anesthesia-tidal volume 12 ml/kg with CMV and surgical intervention-tidal volume was reduced to 9 ml/kg. OLV was initiated with an endobronchial blocker, and the animals were randomly allocated to either continue CMV or switch to BVV for 90 min. After OLV, a recruitment maneuver was undertaken, and both lungs were ventilated for a further 60 min. At predetermined intervals, hemodynamics, respiratory gases (arterial, venous, and end-tidal samples) and mechanics (airway pressures, static and dynamic compliances) were measured. Derived indices (pulmonary vascular resistance, shunt fraction, and dead space ventilation) were calculated. Results By 15 min of OLV, arterial oxygen tension was greater in the BVV group (group x time interaction, P = 0.003), and shunt fraction was lower with BVV from 30 to 90 min (group effect, P = 0.0004). From 60 to 90 min, arterial carbon dioxide tension was lower with BVV (group x time interaction, P = 0.0001) and dead space ventilation was less from 60 to 90 min (group x time interaction, P = 0.0001). Static compliance was greater by 60 min of BVV and remained greater during return to ventilation of both lungs (group effect, P = 0.0001). Conclusions In this model of OLV, BVV resulted in superior gas exchange and respiratory mechanics when compared with CMV. Improved static compliance persisted with restoration of two-lung ventilation.

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Effect of the Ti/Te ratio on mean intratracheal pressure in high-frequency oscillatory ventilation

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.5.1520 ◽

1998 ◽

Vol 84 (5) ◽

pp. 1520-1527 ◽

Cited By ~ 16

Author(s):

Ulrich Thome ◽

Frank Pohlandt

Keyword(s):

High Frequency ◽

Airway Pressure ◽

High Frequency Oscillatory Ventilation ◽

Inspiratory Time ◽

Mean Airway Pressure ◽

Air Trapping ◽

Oscillatory Ventilation ◽

Mean Pressure ◽

Oscillation Frequencies ◽

High Frequency Oscillatory

In high-frequency oscillatory ventilation (HFOV), an adequate mean airway pressure is crucial for successful ventilation and optimal gas exchange, but air trapping cannot be detected by the usual measurement at the y piece. Intratracheal pressures produced by the high-frequency oscillators HFV-Infantstar (IS), Babylog 8000 (BL), and the SensorMedics 3100A (SM) [the latter with either 30% (SM30) or 50% (SM50) inspiratory time] were investigated in four anesthetized tracheotomized female piglets that were 1 day old and weighed 1.6–1.9 kg (mean 1.76 kg). The endotracheal tube was repeatedly clamped while the piglets were ventilated with an oscillation frequency of 10 Hz, and the airway pressure distal of the clamp was recorded as a measure of average intrapulmonary pressure during oscillation. Clamping resulted in a significant decrease of mean airway pressure when the piglets were ventilated with SM30(−0.86 cmH2O), BL (−0.66 cmH2O), and IS (−0.71 cmH2O), but airway pressure increased by a mean of 0.76 cmH2O with SM50. Intratracheal pressure, when measured by a catheter pressure transducer at various oscillation frequencies, was lower than at the y piece by 0.4–0.9 cmH2O (SM30), 0.3–3 cmH2O (BL), and 1–4.7 cmH2O (IS) but was 0.4–0.7 cmH2O higher with SM50. We conclude that the inspiratory-to-expiratory time (Ti/Te) ratio influences the intratracheal and intrapulmonary pressures in HFOV and may sustain a mean pressure gradient between the y piece and the trachea. A Ti/Te ratio < 1:1 may be useful to avoid air trapping when HFOV is used.

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Abstract 13216: Initial Survey of Respiratory Mechanics During Prehospital Bag Ventilation

Circulation ◽

10.1161/circ.144.suppl_2.13216 ◽

2021 ◽

Vol 144 (Suppl_2) ◽

Author(s):

Betty Y Yang ◽

Jennifer E Blackwood ◽

Jenny Shin ◽

Sally Guan ◽

Mengqi Gao ◽

...

Keyword(s):

Tidal Volume ◽

Respiratory Mechanics ◽

Predicted Body Weight ◽

Convenience Sample ◽

Measuring Device ◽

Respiratory Parameters ◽

Initial Survey ◽

Post Intubation ◽

End Tidal ◽

The Relationship

Introduction: Respiratory mechanics, such as tidal volume and inspiratory pressures, affect outcome in hospitalized patients with respiratory failure. The ability to accurately measure respiratory mechanics in the prehospital setting is limited, thus the relationship between prehospital respiratory mechanics and clinical outcome is not well understood. In this feasibility study, we examined respiratory mechanics of bag-valve mask (BVM) ventilation by emergency medical services (EMS) using a novel in-line measuring device during a period when agencies switched from larger to smaller ventilation bags. Methods: This prospective cohort study included a convenience sample of adult patients who received BVM ventilation by EMS, from August 2018 to January 2020, in Bellevue, Washington. The airway monitoring device was applied by paramedics after intubation to passively record in black box mode, until termination of efforts or hospital arrival. Respiratory parameters included tidal volume, airway pressure, flow rates, end-tidal carbon dioxide, and respiratory rate. Prehospital agencies transitioned from large (1500 mL) to small (1000 mL) ventilation bags during the study period. Results: 7371 post-intubation breaths were measured in 54 patients, 32 treated for out-of-hospital cardiac arrest (OHCA) and 22 treated for non-arrest conditions, primarily respiratory etiology. EMS ventilated 19 patients with a small bag and 35 patients with a large bag. Ventilation with a smaller bag was characterized by less variability in tidal volumes and higher proportion of breaths delivered within 4-10 mL/kg of predicted body weight (Figure) (p<0.05). Conclusions: Respiratory mechanics can be measured in EMS patients receiving BVM ventilation following intubation. Ventilation with a smaller bag might reduce variation in tidal volume, but further study is needed. These data provide the first evaluation of respiratory mechanics during manual ventilation provided by EMS.

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Response to Acute Hypercapnia in the Parents of Victims of Sudden Infant Death Syndrome

PEDIATRICS ◽

10.1542/peds.73.5.652 ◽

1984 ◽

Vol 73 (5) ◽

pp. 652-655

Author(s):

Jonathan M. Couriel ◽

Anthony Olinsky

Keyword(s):

Tidal Volume ◽

Sudden Infant Death Syndrome ◽

Infant Death ◽

Cycle Time ◽

Ventilatory Response ◽

Minute Ventilation ◽

Sudden Infant Death ◽

Respiratory Cycle ◽

Sudden Infant ◽

Inspiratory Time

The ventilatory response to acute hypercapnia was studied in 68 parents of victims of sudden infant death syndrome and 56 control subjects. Tidal volume, inspiratory time, and total respiratory cycle time were measured before and immediately after a vital capacity breath of 13% CO2 in oxygen. Instantaneous minute ventilation, mean inspiratory flow (tidal volume/inspiratory time), and respiratory timing (inspiratory time/total respiratory cycle time) were calculated. Both groups of subjects showed a marked increase in tidal volume (48.4% ± 26.5%), instantaneous minute ventilation (56% ± 35%), and tidal volume/inspiratory time (56.8% ± 33.5%) after inhalation of the test gas, with little change in inspiratory time/total respiratory cycle time. There were no significant differences between the two groups for ventilation before or after inhalation of the test gas. The ventilatory response to acute hypercapnia is mediated by the peripheral chemoreceptors. These results suggest that an inherited abnormality of peripheral chemoreceptor function is unlikely to be a factor leading to sudden infant death syndrome.

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Influence of volume dependency and timing of airway occlusions on the Hering-Breuer reflex in infants

Journal of Applied Physiology ◽

10.1152/jappl.1998.85.6.2033 ◽

1998 ◽

Vol 85 (6) ◽

pp. 2033-2039 ◽

Cited By ~ 20

Author(s):

Patricia S. Rabbette ◽

Janet Stocks

Keyword(s):

Respiratory Mechanics ◽

Newborn Infants ◽

Tidal Range ◽

First Year ◽

Similar Response ◽

Inspiratory Time ◽

Tidal Breathing ◽

Age Related ◽

The Difference ◽

First Year Of Life

Both end-inspiratory (EIO) and end-expiratory (EEO) airway occlusions are used to calculate the strength of the Hering-Breuer inflation reflex (HBIR) in infants. However, the influence of the timing of such occlusions is unknown, as is the extent to which changes in volume within and above the tidal range affect this reflex. The purpose of this study was to compare both techniques and to evaluate the volume dependency of the HBIR in healthy, sleeping infants up to 1 yr of age. The strength of the HBIR was expressed as the ratio of expiratory or inspiratory time during EIO or EEO, respectively, to that recorded during spontaneous breathing, i.e., as the “inhibitory ratio” (IR). Paired measurements of the EIO and EEO in 26 naturally sleeping newborn and 15 lightly sedated infants at ∼1 yr showed no statistically significant differences in the IR according to technique: mean (95% CI) of the difference (EIO − EEO) being −0.02 (−0.17, 0.13) during the first week of life and 0.04 (−0.14, 0.22) at 1 yr. During tidal breathing, a volume threshold of ∼4 ml/kg was required to evoke the HBIR. Marked volume and age dependency were observed. In newborn infants, occlusions at ∼10 ml/kg during sighs always resulted in an IR > 4, whereas a similar response was only evoked at 25 ml/kg in older infants. Age-related changes in the volume threshold may reflect maturational changes in the control of breathing and respiratory mechanics throughout the first year of life.

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Effects Of High And Low Tidal Volume Ventilation On Respiratory Mechanics And Systemic Inflammation In Canine Acute Lung Injury

10.1164/ajrccm-conference.2012.185.1_meetingabstracts.a2046 ◽

2012 ◽

Author(s):

David W. Kaczka ◽

Jacob Herrmann ◽

Michael T. Crow ◽

Brett A. Simon

Keyword(s):

Acute Lung Injury ◽

Lung Injury ◽

Tidal Volume ◽

Systemic Inflammation ◽

Respiratory Mechanics ◽

Low Tidal Volume ◽

Low Tidal Volume Ventilation ◽

Volume Ventilation

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Load compensation and respiratory muscle function during sleep

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.4.1221 ◽

1992 ◽

Vol 72 (4) ◽

pp. 1221-1234 ◽

Cited By ~ 40

Author(s):

K. G. Henke ◽

M. S. Badr ◽

J. B. Skatrud ◽

J. A. Dempsey

Keyword(s):

Eye Movement ◽

Chest Wall ◽

Muscle Activity ◽

Respiratory Muscle ◽

Airway Resistance ◽

Upper Airway ◽

Rapid Eye Movement Sleep ◽

Compensatory Mechanisms ◽

Ventilatory Control ◽

Load Compensation

The sleeping state places unique demands on the ventilatory control system. The sleep-induced increase in airway resistance, the loss of consciousness, and the need to maintain the sleeping state without frequent arousals require the presence of complex compensatory mechanisms. The increase in upper airway resistance during sleep represents the major effect of sleep on ventilatory control. This occurs because of a loss of muscle activity, which narrows the airway and also makes it more susceptible to collapse in response to the intraluminal pressure generated by other inspiratory muscles. The magnitude and timing of the drive to upper airway vs. other inspiratory pump muscles determine the level of resistance and can lead to inspiratory flow limitation and complete upper airway occlusion. The fall in ventilation with this mechanical load is not prevented, as it is in the awake state, because of the absence of immediate compensatory responses during sleep. However, during sleep, compensatory mechanisms are activated that tend to return ventilation toward control levels if the load is maintained. Upper airway protective reflexes, intrinsic properties of the chest wall, muscle length-compensating reflexes, and most importantly chemoresponsiveness of both upper airway and inspiratory pump muscles are all present during sleep to minimize the adverse effect of loading on ventilation. In non-rapid-eye-movement sleep, the high mechanical impedance combined with incomplete load compensation causes an increase in arterial PCO2 and augmented respiratory muscle activity. Phasic rapid-eye-movement sleep, however, interferes further with effective load compensation, primarily by its selective inhibitory effects on the phasic activation of postural muscles of the chest wall. The level and pattern of ventilation during sleep in health and disease states represent a compromise toward the ideal goal, which is to achieve maximum load compensation and meet the demand for chemical homeostasis while maintaining sleep state.

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Interactive effects of CO2 and upper airway negative pressure on breathing pattern

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.1.229 ◽

1987 ◽

Vol 63 (1) ◽

pp. 229-237 ◽

Cited By ~ 5

Author(s):

E. van Lunteren

Keyword(s):

Tidal Volume ◽

Respiratory Rate ◽

Negative Pressure ◽

Upper Airway ◽

Interactive Effects ◽

Inspiratory Time ◽

Diaphragm Electrical Activity ◽

Wide Range ◽

Inspiratory Activity ◽

The Relationship

The interactive effects of upper airway negative pressure and hypercapnia on the pattern of breathing were assessed in pentobarbital-anesthetized cats. At any given level of pressure in the upper airway, hypercapnia increased respiratory rate, reduced inspiratory time, and augmented tidal volume, inspiratory airflow, and the peak and rate of rise of diaphragm electrical activity. Conversely, at any given level of CO2, upper airway negative pressure decreased respiratory rate, prolonged inspiratory time, and depressed inspiratory airflow and diaphragm electromyogram (EMG) rate of rise. Application of negative pressure to the upper airway shifted the relationship between tidal volume and inspiratory time upward and rightward. The relationship between inspiratory and expiratory times, however, was linearly correlated over a wide range of chemical drives and levels of upper airway pressure. These results suggest that in the anesthetized cat upper airway negative pressure afferent inputs 1) interact in an additive fashion with hypercapnia to alter the pattern of breathing, 2) interact multiplicatively with CO2 to influence mean inspiratory airflow and diaphragm EMG rate of rise, 3) depress the generation of central inspiratory activity, 4) increase the time-dependent volume threshold for inspiratory termination, and 5) affect the ratio between inspiratory and expiratory times in a similar manner as alterations in PCO2.

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