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

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 Semi-Aquatic Turtle, Pseudemys Scripta

1986 ◽  
Vol 125 (1) ◽  
pp. 137-155 ◽  
Author(s):  
Timothy Z. Vitalis ◽  
William K. Milsom
Keyword(s):  
Body Wall ◽  
Striated Muscle ◽  
Work Of Breathing ◽  
Body Cavity ◽  
The Body ◽  
Mechanical Work ◽  
Pulmonary Mechanics ◽  
Pump Frequency ◽  
Elastic Forces ◽  
Pseudemys Scripta

Measurements of pulmonary mechanics on anaesthetized specimens of the aquatic turtle Pseudemys scripta (Schoepff) indicate that the static pulmonary mechanics of the total respiratory system are determined primarily by the mechanics of the body wall rather than those of the lungs. This is also true under the dynamic conditions of pump ventilation at low pump frequencies. As pump frequency increases, the work required to inflate the multicameral lungs of the turtle begins to contribute an increasing portion to the total mechanical work required to produce each breath as measured from pressure volume loops. The rise in the work performed on the lungs results from an increase in the non-elastic, flow-resistive forces which must be overcome during ventilation. The primary bronchus to each lung is the most likely site of flow resistance. There is also a small elastic component to the work required to ventilate the lungs associated with movement of the intrapulmonary septa and the striated muscle surrounding the lungs. The contribution of the work required to distend the body cavity as a percentage of the total mechanical work required to generate each breath remains relatively unchanged with increasing ventilation frequency, indicating that the majority of the forces to be overcome in the body wall are elastic in nature. For a constant rate of minute pump ventilation, as frequency increases, the work done per minute to overcome elastic forces decreases, while that done to overcome non-elastic forces begins to rise. These opposing trends produce an optimum combination of pump volume and frequency at which the rate of mechanical work is minimum.

Ventilatory response to hypoxia in unanesthetized newborn kittens

1988 ◽  
Vol 64 (6) ◽  
pp. 2544-2551 ◽  
Author(s):  
H. Rigatto ◽  
C. Wiebe ◽  
C. Rigatto ◽  
D. S. Lee ◽  
D. Cates
Keyword(s):  
Tidal Volume ◽  
Chest Wall ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Respiratory Frequency ◽  
Quiet Sleep ◽  
Newborn Kitten ◽  
Peripheral Mechanism ◽  
Flow Through ◽  
Ventilatory Response To Hypoxia

We studied the ventilatory response to hypoxia in 11 unanesthetized newborn kittens (n = 54) between 2 and 36 days of age by use of a flow-through system. During quiet sleep, with a decrease in inspired O2 fraction from 21 to 10%, minute ventilation increased from 0.828 +/- 0.029 to 1.166 +/- 0.047 l.min-1.kg-1 (P less than 0.001) and then decreased to 0.929 +/- 0.043 by 10 min of hypoxia. The late decrease in ventilation during hypoxia was related to a decrease in tidal volume (P less than 0.001). Respiratory frequency increased from 47 +/- 1 to 56 +/- 2 breaths/min, and integrated diaphragmatic activity increased from 14.9 +/- 0.9 to 20.2 +/- 1.4 arbitrary units; both remained elevated during hypoxia (P less than 0.001). Younger kittens (less than 10 days) had a greater decrease in ventilation than older kittens. These results suggest that the late decrease in ventilation during hypoxia in the newborn kitten is not central but is due to a peripheral mechanism located in the lungs or respiratory pump and affecting tidal volume primarily. We speculate that either pulmonary bronchoconstriction or mechanical uncoupling of diaphragm and chest wall may be involved.

scholarly journals The influence of the post-pulmonary septum and submersion on the pulmonary mechanics of Trachemys scripta (Cryptodira: Emydidae)

2021 ◽  
Author(s):  
Ray Brasil Bueno de Souza ◽  
Wilfried Klein
Keyword(s):  
Hydrostatic Pressure ◽  
Respiratory System ◽  
Intact Animal ◽  
Work Of Breathing ◽  
Dynamic Compliance ◽  
Body Cavity ◽  
Trachemys Scripta ◽  
Pulmonary Mechanics ◽  
Static Compliance ◽  
Breathing Mechanics

The respiratory system of chelonians needs to function within a mostly solid carapace, with ventilation depending on movements of the flanks. When submerged, inspiration has to work against a hydrostatic pressure and we examined breathing mechanics in Trachemys scripta while underwater. Furthermore, the respiratory system of T. scripta possesses a well-developed post-pulmonary septum (PPS), and we investigated its role on breathing mechanics of lungs with and without their PPS attached. Static compliance was significantly increased in submerged animals and in animals with and without their PPS, while the removal of the PPS did not result in a significantly different static compliance. Dynamic compliance was significantly affected by changes in volume and frequency in every treatment, with submergence significantly decreasing dynamic compliance. The presence of the PPS significantly increased dynamic compliance. Submersion did not alter significantly work per ventilation, but caused minute work of breathing to be much greater at any frequency and ventilation level analyzed. Lungs with or without their PPS did not show significantly different work per ventilation when compared to intact animal. Our results demonstrate that submersion results in significantly altered breathing mechanics, increasing minute work of breathing greatly. The PPS was shown to maintain a constant volume within the animal's body cavity, wherein the lungs can be ventilated more easily, highlighting the importance of this coelomic subdivision in the chelonian body cavity.

Influence of global inspiratory muscle fatigue on breathing during exercise

1996 ◽  
Vol 80 (4) ◽  
pp. 1270-1278 ◽  
Author(s):  
P. Sliwinski ◽  
S. Yan ◽  
A. P. Gauthier ◽  
P. T. Macklem
Keyword(s):  
Tidal Volume ◽  
Muscle Fatigue ◽  
Minute Ventilation ◽  
Inspiratory Muscle ◽  
Abdominal Muscles ◽  
Maximal Power Output ◽  
Lung Inflation ◽  
Rib Cage ◽  
Inspiratory Muscles ◽  
Inspiratory Muscle Fatigue

We evaluated the effect of global inspiratory muscle fatigue (GF) on respiratory muscle control during exercise at 30, 60, and 90% of maximal power output in normal subjects. Fatigue was induced by breathing against a high inspiratory resistance until exhaustion. Esophageal and gastric pressures, anteroposterior displacement of the rib cage and abdomen, breathing pattern, and perceived breathlessness were measured. Induction of GF had no effect on the ventilatory parameters during mild and moderate exercise. It altered, however, ventilatory response to heavy exercise by increasing breathing frequency and minute ventilation, with minor changes in tidal volume. This was accompanied by an increase in perceived breathlessness. GF significantly increased both the tonic and phasic activities of abdominal muscles that allowed 1) the diaphragm to maintain its function while developing less pressure, 2) the same tidal volume with lesser shortening of the rib cage inspiratory muscles, and 3) relaxation of the abdominal muscles to contribute to lung inflation. The increased work performed by the abdominal muscles may, however, lead to a reduction in their strength. GF may impair exercise performance in some healthy subjects that is probably not related to excessive breathlessness or other ventilatory factors. We conclude that the respiratory system is remarkably adaptable in maintaining ventilation during exercise even with impaired inspiratory muscle contractility.

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.

Influence of CO2 on upper airway muscles and chest wall/diaphragm corticomotor responses assessed by transcranial magnetic stimulation in awake healthy subjects

2012 ◽  
Vol 112 (5) ◽  
pp. 798-805 ◽  
Author(s):  
Jean-Christian Borel ◽  
Cesar Augusto Melo-Silva ◽  
Simon Gakwaya ◽  
Frédéric Sériès
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Tidal Volume ◽  
Chest Wall ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Minute Ventilation ◽  
Motor Evoked Potential ◽  
Upper Airway ◽  
Random Order ◽  
Respiratory Drive

Rationale: functional interaction between upper airway (UA) dilator muscles and the diaphragm is crucial in the maintenance of UA patency. This interaction could be altered by increasing respiratory drive. The aim of our study was to compare the effects of hypercapnic stimulation on diaphragm and genioglossus corticomotor responses to transcranial magnetic stimulation (TMS). Methods: 10 self-reported healthy men (32 ± 9 yr; body mass index = 24 ± 3 kg/m−2) breathed, in random order, room air or 5% and then 7% FiCO2, both balanced with pure O2. Assessments included ventilatory variables, isoflow UA resistance (at 300 ml/s), measurement of lower chest wall/diaphragm (LCW/diaphragm), and genioglossus motor threshold (MT) and motor-evoked potential (MEP) characteristics. TMS twitches were applied during early inspiration and end expiration at stimulation intensity 30% above LCW/diaphragm and genioglossus MT. Results: compared with room air, CO2 inhalation significantly augmented minute ventilation, maximal inspiratory flow, tidal volume, and tidal volume/respiratory time ratio. UA resistance was unchanged with CO2 inhalation. During 7% CO2 breathing, LCW/diaphragm MT decreased by 9.6 ± 10.1% whereas genioglossus MT increased by 7.2 ± 9%. CO2-induced ventilatory stimulation led to elevation of LCW/diaphragm MEP amplitudes during inspiration but not during expiration. LCW/diaphragm MEP latencies remained unaltered both during inspiration and expiration. Genioglossus MEP latencies and amplitudes were unchanged with CO2. Conclusion: in awake, healthy subjects, CO2-induced hyperventilation is associated with heightened LCW/diaphragm corticomotor activation without modulating genioglossus MEP responses. This imbalance may promote UA instability during increased respiratory drive.

scholarly journals The Interrelationship Between Pulmonary Mechanics and the Spontaneous Breathing Pattern in the Tokay Lizard, Gekko Gecko

1984 ◽  
Vol 113 (1) ◽  
pp. 203-214 ◽  
Author(s):  
WILLIAM K. MILSOM
Keyword(s):  
Tidal Volume ◽  
Spontaneous Breathing ◽  
Breathing Pattern ◽  
Pulmonary Ventilation ◽  
Periodic Breathing ◽  
Breath Holding ◽  
Pulmonary Mechanics ◽  
Respiratory Drive ◽  
Breathing Patterns ◽  
Gekko Gecko

The normal breathing pattern of the Tokay gecko (Gekko gecko) consists of single breaths or bursts of a few breaths separated by periods of breath holding. Increases in pulmonary ventilation that accompany rises in body temperature are caused by increases in respiratory frequency due to shortening of the periods of breath holding. Tidal volume and breath duration remain relatively constant. Measurements of the mechanical work associated with spontaneous breathing yielded values that were similar to those calculated for breaths of the same size and duration based on work curves generated during pump ventilation of anaesthetized animals. In this species, the pattern of periodic breathing and the ventilatory responses to changes in respiratory drive correspond with predictions of optimal breathing patterns based on calculations of the mechanical cost of ventilation. Bilateral vagotomy drastically alters the breathing pattern producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of the breath duration. These alterations greatly increase the mechanical cost of ventilation. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal afferent control and which serves to minimize the cost of breathing.

Pulmonary mechanisms of the normal ferret

1981 ◽  
Vol 50 (4) ◽  
pp. 799-804 ◽  
Author(s):  
R. L. Boyd ◽  
J. A. Mangos
Keyword(s):  
Chest Wall ◽  
Vital Capacity ◽  
Minute Ventilation ◽  
Dynamic Compliance ◽  
Specific Conductance ◽  
Pulmonary Mechanics ◽  
Nasal Breathing ◽  
Lung Capacity ◽  
Esophageal Balloon ◽  
Residual Capacity

Pulmonary mechanics were measured in normal anesthetized male Fitch ferrets (200-360 g). In eight transorally intubated ferrets, pressure-volume (PV) curves for the lung and chest wall were obtained with an esophageal balloon and body plethysmograph. The lung volumes and capacities expressed as a percentage of the total lung capacity (mean, 49.8 ml) were: vital capacity, 84.7%; inspiratory capacity, 63.7%; inspiratory reserve volume, 58.2%; functional residual capacity, 33.8%; expiratory reserve volume, 16.8%; residual volume, 15.3%; and tidal volume, 8.0%. The compliance of the lung (2.93 ml . cmH2O-1), chest wall (22.42 ml . cmH2O-1) and respiratory system (2.55 ml . cmH2O-1) were determined from the PV curves. The dynamic compliance (1.6 ml . cmH2O-1), pulmonary resistance (0.024 cmH2O . ml-1 . s), frequency of breathing (43.5 breaths . min-1), and minute ventilation (195 ml . min-1) were measured during spontaneous breathing. In a second group of 10 ferrets the total airway resistance (0.116 cmH2O . ml-1 . s) and specific conductance (0.915 ml . s-1 . cmH2O . ml-1) were measured during spontaneous nasal breathing. In general the pulmonary mechanics of the ferret were similar to those of the rabbit and dog, when the data were normalized for lung volume.

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