Respiratory adaptations to dead space loading during maximal incremental exercise

1991 ◽  
Vol 70 (1) ◽  
pp. 55-62 ◽  
Author(s):  
C. McParland ◽  
J. Mink ◽  
C. G. Gallagher
Keyword(s):  
Tidal Volume ◽  
Carotid Body ◽  
Dead Space ◽  
Breathing Pattern ◽  
Normal Subjects ◽  
Time Profile ◽  
Incremental Exercise ◽  
Respiratory Frequency ◽  
Heavy Exercise ◽  
Ventilatory Capacity

We examined the effects of dead space (VD) loading on breathing pattern during maximal incremental exercise in eight normal subjects. Addition of external VD was associated with a significant increase in tidal volume (VT) and decrease in respiratory frequency (f) at moderate and high levels of ventilation (VI); at a VI of 120 l/min, VT and f with added VD were 3.31 +/- 0.33 liters and 36.7 +/- 6.7 breaths/min, respectively, compared with 2.90 +/- 0.29 liters and 41.8 +/- 7.3 breaths/min without added VD. Because breathing pattern does not change with CO2 inhalation during heavy exercise (Gallagher et al. J. Appl. Physiol. 63: 238–244, 1987), the breathing pattern response to added VD is probably a consequence of alteration in the PCO2 time profile, possibly sensed by the carotid body and/or airway-pulmonary chemoreceptors. The increase in VT during heavy exercise with VD loading indicates that the tachypneic breathing pattern of heavy exercise is not due to mechanical limitation of maximum ventilatory capacity at high levels of VT.

Carotid chemoreceptors and respiratory adaptations to dead space loading during incremental exercise

1993 ◽  
Vol 75 (3) ◽  
pp. 1378-1384 ◽  
Author(s):  
N. C. Syabbalo ◽  
T. Zintel ◽  
R. Watts ◽  
C. G. Gallagher
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Breathing Pattern ◽  
Bicycle Ergometer ◽  
Incremental Exercise ◽  
Exercise Tests ◽  
Carotid Chemoreceptors ◽  
The Difference ◽  
Air Control ◽  
And Control

Dead space (VD) loading has been shown to cause an increase in tidal volume and a decrease in respiratory frequency at moderate to high levels of ventilation (VI) during exercise (J. Appl. Physiol. 70: 55–62, 1991). This study examined the role of carotid chemoreceptors (CC) in the breathing pattern response to added VD during maximal incremental exercise; we used hyperoxia to silence the CC. Nine healthy subjects exercised on a bicycle ergometer on 4 different days while inspiring air with VD (AVD) and without VD [air control (AC)] and while inspiring 100% O2 with VD (O2VD) and without VD (O2C). Equipment resistance for VD and control studies was identical, and the exercise tests were done in a randomized order. At a matched level of VI equivalent to 75% VI at the end of the AC experiments (102 l/min), the breathing pattern in the AVD and O2VD tests was significantly deeper and slower (P < 0.05) than that in the AC and O2C tests. The difference in tidal volume between AVD and AC tests (delta = 0.26 +/- 0.16 liter) was not significantly different from that between O2VD and O2C tests (delta = 0.23 +/- 0.23 liter). The breathing pattern was the same in the AC and O2C tests. It is concluded that the altered breathing pattern with VD loading is not mediated by the CC.

Effort sensation, chemoresponsiveness, and breathing pattern during inspiratory resistive loading

1992 ◽  
Vol 73 (2) ◽  
pp. 440-445 ◽  
Author(s):  
J. E. Clague ◽  
J. Carter ◽  
M. G. Pearson ◽  
P. M. Calverley
Keyword(s):  
Tidal Volume ◽  
Breathing Pattern ◽  
Free Breathing ◽  
Normal Subjects ◽  
Inspiratory Effort ◽  
Sustained Load ◽  
Resistive Loading ◽  
End Tidal ◽  
Few Data ◽  
Normal Men

Although inspiratory resistive loading (IRL) reduces the ventilatory response to CO2 (VE/PCO2) and increases the sensation of inspiratory effort (IES), there are few data about the converse situation: whether CO2 responsiveness influences sustained load compensation and whether awareness of respiratory effort modifies this behavior. We studied 12 normal men during CO2 rebreathing while free breathing and with a 10-cmH2O.l-1.s IRL and compared these data with 5 min of resting breathing with and without the IRL. Breathing pattern, end-tidal PCO2, IES, and mouth occlusion pressure (P0.1) were recorded. Free-breathing VE/PCO2 was inversely related to an index of effort perception (IES/VE; r = -0.63, P less than 0.05), and the reduction in VE/PCO2 produced by IRL was related to the initial free-breathing VE/PCO2 (r = 0.87, P less than 0.01). IRL produced variable increases in inspiratory duration (TI), IES, and P0.1 at rest, and the change in tidal volume correlated with both VE/PCO2 (r = 0.63, P less than 0.05) and IES/VE (r = -0.69, P less than 0.05), this latter index also predicting the changes in TI with loading (r = -0.83, P less than 0.01). These data suggest that in normal subjects perception of inspiratory effort can modify free-breathing CO2 responsiveness and is as important as CO2 sensitivity in determining the response to short-term resistive loading. Individuals with good perception choose a small-tidal volume and short-TI breathing pattern during loading, possibly to minimize the discomfort of breathing.

Ventilatory effects and interactions with change in PaO2 in awake goats

1991 ◽  
Vol 71 (4) ◽  
pp. 1254-1260 ◽  
Author(s):  
L. Daristotle ◽  
M. J. Engwall ◽  
W. Z. Niu ◽  
G. E. Bisgard
Keyword(s):  
Tidal Volume ◽  
Carotid Body ◽  
Ventilatory Response ◽  
Respiratory Frequency ◽  
Systemic Hypoxia ◽  
Ventilatory Effects ◽  
Arterial Po2

We utilized selective carotid body (CB) perfusion while changing inspired O2 fraction in arterial isocapnia to characterize the non-CB chemoreceptor ventilatory response to changes in arterial PO2 (PaO2) in awake goats and to define the effect of varying levels of CB PO2 on this response. Systemic hyperoxia (PaO2 greater than 400 Torr) significantly increased inspired ventilation (VI) and tidal volume (VT) in goats during CB normoxia, and systemic hypoxia (PaO2 = 29 Torr) significantly increased VI and respiratory frequency in these goats. CB hypoxia (CB PO2 = 34 Torr) in systemic normoxia significantly increased VI, VT, and VT/TI; the ventilatory effects of CB hypoxia were not significantly altered by varying systemic PaO2. We conclude that ventilation is stimulated by systemic hypoxia and hyperoxia in CB normoxia and that this ventilatory response to changes in systemic O2 affects the CB O2 response in an additive manner.

Relationship between Cr and breathing pattern in mechanically ventilated patients

1994 ◽  
Vol 77 (6) ◽  
pp. 2703-2708 ◽  
Author(s):  
H. Burnet ◽  
M. Bascou-Bussac ◽  
C. Martin ◽  
Y. Jammes
Keyword(s):  
Linear Regression ◽  
Tidal Volume ◽  
Multiple Linear Regression ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Respiratory Frequency ◽  
Upper Airways ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Ventilated Patients

In mechanically ventilated patients the natural gas-conditioning process of the upper airways is bypassed by the use of an endotracheal tube or a tracheostomy. We hypothesized that under these conditions the breathing pattern may greatly influence the convective respiratory heat loss (Cr). Cr values were computed from minute ventilation (VE) and inspiratory and expiratory gas temperatures, which were measured in six patients under mechanical ventilation for the management of cranial trauma. In each patient the effects of 11–20 different breathing patterns were investigated. Relationships between Cr and VE and between combined tidal volume and respiratory frequency were obtained by simple and multiple linear regression methods, respectively. Comparison of the standard errors of estimate indicated that multiple linear regression gives the best fit. Thus, Cr was highly dependent on the breathing pattern and was not related only to VE. For the same VE value, Cr was higher when VE was achieved with high tidal volume and low respiratory frequency. These data are consistent with previous studies in which thermal exchanges through the upper airways were taxed by hyperventilation of frigid air.

Breathing pattern of kittens during hypoxia

1984 ◽  
Vol 56 (1) ◽  
pp. 12-17 ◽  
Author(s):  
C. E. Blanco ◽  
M. A. Hanson ◽  
P. Johnson ◽  
H. Rigatto
Keyword(s):  
Arterial Pressure ◽  
Tidal Volume ◽  
Breathing Pattern ◽  
Esophageal Pressure ◽  
Central Mechanism ◽  
Respiratory Frequency ◽  
Low Frequencies ◽  
Pentobarbital Sodium

In 19 pentobarbital sodium-anesthetized kittens aged 5–34 days, inspired O2 was reduced from 21 to 6–512%. Respiratory frequency (f) and tidal volume (VT) increased within 30 s. Over 5 min f fell to about 60% below control; VT usually fell but remained above control. Arterial pressure fell in 80% of trials, sometimes before f fell. Arterial CO2 was below control, but raising inspired CO2 to keep expired CO2 at control did not prevent the fall in f and VT. The relation between VT and esophageal pressure or diaphragm electromyogram (EMG) did not change consistently, nor was the ratio of high to low frequencies in the diaphragm EMG altered. Carotid chemoreceptor discharge increased within 15 s, and at 5 min it was much above control. We conclude that the change in the breathing pattern in hypoxia is probably due to the activation of a central mechanism.

Mechanical efficiency of breathing

1960 ◽  
Vol 15 (3) ◽  
pp. 359-362 ◽  
Author(s):  
G. Milic-Emili ◽  
J. M. Petit
Keyword(s):  
Oxygen Consumption ◽  
Tidal Volume ◽  
Dead Space ◽  
Energy Cost ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Mechanical Efficiency ◽  
Mechanical Work ◽  
Closed Circuit ◽  
Simultaneous Measurements

Simultaneous measurements of mechanical work and energy cost of breathing were performed on four normal subjects with ventilation increased by adding dead space. Mechanical work was obtained from simultaneous records of endoesophageal pressure and tidal volume. The associated energy cost was estimated by measuring oxygen consumption of respiratory muscles by means of a closed-circuit spirometer. In all subjects studied and over the range of ventilations involved (ca. 30–110 l/min.), the mechanical efficiency of breathing was found to be in the order of 0.19–0.25. Submitted on July 6, 1959

Alveolar gas exchange during exercise: a single-breath analysis

1984 ◽  
Vol 57 (6) ◽  
pp. 1704-1709 ◽  
Author(s):  
C. J. Allen ◽  
N. L. Jones ◽  
K. J. Killian
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Heavy Exercise ◽  
Single Breath ◽  
Arterial Blood ◽  
Co2 Output ◽  
Dead Space Volume ◽  
Airway Dead Space ◽  
Male Subjects ◽  
Alveolar Gas Exchange

Changes in expired alveolar O2 and CO2 were measured breath-by-breath in six healthy male subjects (mean age 30 yr, mean weight 80 kg) at rest, 600 kpm/min, and 1,200 kpm/min. Changes were expressed in relation to expired volume (liters) and time (s) and separated into an initial dead-space component using the Fowler method applied to expired CO2 and O2, and alveolar slope. The alveolar slopes with respect to time (dPACO2, dPAO2, Torr/s) increased in relation to CO2 output (VCO2, 1/min, STPD) and O2 intake (VO2, 1/min, STPD) but were reduced by increasing tidal volume (VT, liters, BTPS): dPACO2 = 2.7 + 4.6(VCO2) - 1.9(VT) (r = 0.97); and dPAO2 = 2.3 + 5.5(VO2) - 1.9(VT) (r = 0.96). From the alveolar slopes, tidal volume, and airway dead-space volume, mean expired alveolar PO2 and PCO2 (PAO2, PACO2) were calculated. There was no change in arterialized capillary PCO2 (PaCO2) between rest (38.9 +/- 0.66 Torr) and heavy exercise (38.2 +/- 2.18 Torr), but mean PACO2 rose from 36.7 +/- 0.55 to 40.8 +/- 1.67 Torr during heavy exercise. There was no change in arterialized capillary (mean = 84.3 +/- 0.7 Torr) or alveolar (mean = 107.2 +/- 1.03 Torr) PO2. Exercise increases the fluctuations in alveolar gas composition leading to discrepancies between the PCO2 in mean alveolar gas and arterial blood to an extent that is dependent on VCO2 and VT.

Estimated vs Actual Values for Dead Space/Tidal Volume Ratios During Incremental Exercise in Patients Evaluated for Dyspnea

CHEST Journal ◽  
1994 ◽  
Vol 106 (1) ◽  
pp. 131-136 ◽  
Author(s):  
Mark I. Zimmerman ◽  
Albert Miller ◽  
Lee K. Brown ◽  
Anand Bhuptani ◽  
Mark F. Sloane ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Incremental Exercise

Restraining hamsters alters their breathing pattern

1991 ◽  
Vol 70 (3) ◽  
pp. 1271-1276 ◽  
Author(s):  
T. D. Sweeney ◽  
D. E. Leith ◽  
J. D. Brain
Keyword(s):  
Muscle Strength ◽  
Exercise Training ◽  
Tidal Volume ◽  
Adult Male ◽  
Breathing Pattern ◽  
Minute Volume ◽  
Respiratory Frequency ◽  
Prior Exercise ◽  
Sedentary Group ◽  
Inhaled Aerosols

Does the restraint required for head or nose-only exposure of rodents to inhaled aerosols or gases alter their breathing pattern? And does prior exercise training, which may increase muscle strength, affect this response to restraint? To answer those questions, we measured breathing pattern in 11 adult male hamsters while they were either 1) free to move in small cages or 2) closely restrained in head-out cones. The measurements were repeated after hamsters spent 6 wk either sedentary in standard cages or in cages with exercise wheels. Hamsters were placed in a plethysmograph to measure respiratory frequency (f) and tidal volume (VT). Their product is minute volume (V). When restrained, f and V were 1.9 and 1.7 times, respectively, greater than when hamsters were free, but VT did not change. After 6 wk, the sedentary group responded differently to restraint; f increased 3-fold, VT decreased by one-half, and V increased 1.6-fold. Exercised hamsters increased f 2.3-fold and decreased VT by one-third; V increased by 1.5-fold. In inhalation studies, changes in breathing pattern would significantly influence the amount of material inhaled, the fraction retained, and thus the amount and distribution of material deposited in the lungs.

Bolus technique for assessing distribution of inspired gas during tidal breathing

1988 ◽  
Vol 64 (2) ◽  
pp. 681-688
Author(s):  
K. I. Arita ◽  
S. M. Lewis ◽  
C. Mittman
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Path Length ◽  
Normal Subjects ◽  
Tidal Breathing ◽  
Physiological Mechanisms ◽  
Kinetics Of

The washout of an insoluble tracer from the lung may be represented by a model with two ventilatory compartments representing poorly and better-ventilated regions. Using boli of a second insoluble gas delivered at a given point during inspirations of a multibreath washout test, the proportions of labeled inspired ventilation reaching the poorly and well-ventilated regions may be determined by analyzing the kinetics of the exhaled tracer. We studied eight normal subjects breathing through large-bore solenoid valves controlled to maintain tidal volume at 600 or 900 ml. Boli consisting of 15 ml of 80% He-20% O2 were delivered over 75 ms; this labeled approximately 125 ml of inspired gas. Boli were delivered after 50 ml had been inspired to mark early inspiration and after 300 ml had been inspired to mark midinspiration. Using 900-ml tidal breaths, late inspiration was marked by boli delivered at 600 ml. Subjects were studied in the seated and the supine positions. In both positions, significantly more of the early breath went to the poorly ventilated compartment. Several possible physiological mechanisms, singly or in combination, could account for these observations, but differences in dead space path length are most likely involved.

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