scholarly journals Mechanical Analysis of Spontaneous Breathing in the Semi-Aquatic Turtle, Pseudemys Scripta

1986 ◽  
Vol 125 (1) ◽  
pp. 157-171 ◽  
Author(s):  
Timothy Z. Vitalis ◽  
William K. Milsom
Keyword(s):  
Tidal Volume ◽  
Breathing Pattern ◽  
Work Of Breathing ◽  
Pulmonary Ventilation ◽  
Periodic Breathing ◽  
Adaptive Strategy ◽  
Breath Holding ◽  
Breath Hold ◽  
Breathing Frequency ◽  
Pseudemys Scripta

The normal breathing pattern of Pseudemys scripta (Schoepff) consists of a continuous burst of breaths separated by a variable period of breath holding. Under normoxic conditions, tidal volume was 6.9 ml kg−1 and the number of breaths was 1.9 min−1. Increases in pulmonary ventilation upon stimulation by hypercapnia (3% CO2) or hypoxia (4% O2) are caused primarily by increases in the number of breaths per minute due to a shortening of the breath-hold period. Tidal volume and breath duration remain unchanged. The instantaneous breathing frequency (f' = 60/Ttot) of 35 ± 2min−1 corresponds to continuous pump frequencies that minimize the rate of the mechanical work of breathing in anaesthetized turtles. This indicates that turtles breathe at a combination of tidal volume and f' that minimizes the power required to ventilate the lungs. To increase ventilation, the breath hold is shortened and more breaths are taken at this optimal combination. Bilateral vagotomy drastically alters the breathing pattern, producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of breath duration while total ventilation remains unchanged. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal control and which serves to minimize the cost of breathing.

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.

Effect of Microaerosol Inhalation on the Pattern of Breathing

1975 ◽  
Vol 84 (3) ◽  
pp. 344-349 ◽  
Author(s):  
Clarence T. Sasaki ◽  
Andrew Newman ◽  
Tadashi Akitaya ◽  
John A. Kirchner
Keyword(s):  
Airway Obstruction ◽  
Tidal Volume ◽  
Breathing Pattern ◽  
Work Of Breathing ◽  
Supraglottic Larynx

The nose and supraglottic larynx appear to play significant roles in the modification of the breathing pattern in response to a nonirritating solution delivered as a microaerosol. Slower breathing, reflexly produced by such a method, might benefit partial airway obstruction by reducing turbulence and, therefore, the work of breathing without altering tidal volume.

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.

Effects of pursed-lips breathing and expiratory resistive loading in healthy subjects

1996 ◽  
Vol 80 (5) ◽  
pp. 1772-1784 ◽  
Author(s):  
J. A. Spahija ◽  
A. Grassino
Keyword(s):  
Tidal Volume ◽  
Lung Volume ◽  
Healthy Subjects ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Abdominal Muscle ◽  
Breathing Frequency ◽  
Muscle Recruitment ◽  
Rib Cage ◽  
Resistive Loading

To examine the effect of pursed-lips breathing (PLB) on breathing pattern and respiratory mechanics, we studied 11 healthy subjects breathing with and without PLB at rest and during steady-state bicycle exercise. Six of these subjects took part in a second study, which compared the effects of PLB to expiratory resistive loading (ERL). PLB was found to prolong expiratory and total breath durations and to promote a slower and deeper breathing pattern. During exercise, the compensatory increase that occurred in tidal volume was not sufficient to counter the reduction in breathing frequency, causing minute ventilation to be reduced. Although ERL similarly caused minute ventilation and breathing frequency to be decreased, unlike PLB, it produced no change in tidal volume and prolonged expiratory and total breath durations to a lesser extent. PLB and ERL increased the expiratory resistance to a comparable degree, also increasing the expiratory resistive work of breathing and promoting greater expiratory rib cage and abdominal muscle recruitment in response to the expiratory loads. End-expiratory lung volume, which was determined from inspiratory capacity maneuvers, was not altered by PLB; however, with ERL it was increased by 0.20 and 0.24 liter during rest and exercise, respectively. Inspiratory muscle recruitment patterns were not altered by PLB at rest, although small increases in the relative contribution of the rib cage/accessory muscles in conjunction with abdominal muscle relaxation occurred during exercise. Similar trends were observed with ERL. We conclude that, although ERL and PLB induce comparable respiratory muscle recruitment responses, they are not equivalent with respect to breathing pattern changes and effect on end-expiratory lung volume.

Respiratory sinus arrhythmia in humans: how breathing pattern modulates heart rate

1981 ◽  
Vol 241 (4) ◽  
pp. H620-H629 ◽  
Author(s):  
J. A. Hirsch ◽  
B. Bishop
Keyword(s):  
Heart Rate ◽  
Tidal Volume ◽  
Respiratory Sinus Arrhythmia ◽  
Spontaneous Breathing ◽  
Low Frequency ◽  
Corner Frequency ◽  
Breath Hold ◽  
Breathing Frequency ◽  
Quiet Breathing ◽  
Sinus Arrhythmia

The relationship of respiratory sinus arrhythmia amplitude (RSA) to tidal volume and breathing frequency was quantified during voluntarily controlled tidal volume and breathing frequency and spontaneous quiet breathing. Seventeen seated subjects breathed via mouthpiece and nose-clip, maintaining constant tidal volumes at each of several breathing frequencies. Inspiratory breath hold was zero frequency. Log RSA was plotted vs. log frequency for each tidal volume. The large stable RSA for frequencies less than 6 cycles/min was called low-frequency intercept (LFI, 20 +/- 5 beats/min). Low-frequency intercept was inversely proportional to a subject's age only to 35 yr. At higher breathing frequencies above a characteristic corner frequency (fC, 7.2 +/- 1.5 cycles/min) RSA decreased with constant slope (roll-off; 21 +/- 3.4 dB/decade). The RSA-volume relationship was linear permitting normalization of RSA-frequency curves for tidal volume to yield one curve. Spontaneous breathing data points fell on this curve. Voluntarily coupling of heart rate to breathing frequency in integer ratios reduced breath-by-breath variability of RSA without changing mean RSA. In conclusion, low-frequency intercept, corner frequency, and roll-off characterize an individual's RSA-frequency relationship during both voluntarily controlled and spontaneous breathing.

Breathing pattern in hypoxic exposures of varying duration

1987 ◽  
Vol 62 (2) ◽  
pp. 640-645 ◽  
Author(s):  
P. R. Bender ◽  
J. V. Weil ◽  
J. T. Reeves ◽  
L. G. Moore
Keyword(s):  
Tidal Volume ◽  
Sea Level ◽  
Hypobaric Hypoxia ◽  
Breathing Pattern ◽  
Prolonged Exposure ◽  
Breathing Frequency ◽  
Using Data

The relative contributions of breathing frequency and tidal volume to the increase in ventilation during acute or prolonged exposure to hypoxia is uncertain. We examined the changes in breathing pattern during hypoxic exposures lasting minutes, hours, and days using data from previous studies. Increased tidal volume accounted for the increased ventilation during 7–10 and 30 min of isocapnic and poikilocapnic (no CO2 added) hypoxic exposures as well as during 7 h of poikilocapnic hypobaric hypoxia (4,800 m). Tidal volume was also a greater overall contributor than frequency to increased ventilation in sea-level residents during 3 days of isocapnic hypobaric hypoxia (4,100–4,600 m) and in Denver (1,600 m) residents during 5 days on Pikes Peak (4,300 m). In sea-level residents during 3 days of poikilocapnic hypobaric hypoxia (3,600–4,300 m) and during 7–8 days on Pikes Peak, increased frequency accounted for the rise in ventilation. Tidal volume thus contributed more than frequency to increasing ventilation during brief hypoxia, whereas the contribution of frequency was increased in prolonged hypoxia involving a 4,300-m altitude ascent and hypocapnia.

Respiratory correlates of muscle sympathetic nerve activity in heart failure

1998 ◽  
Vol 95 (3) ◽  
pp. 277-285 ◽  
Author(s):  
Matthew T. NAUGHTON ◽  
John S. FLORAS ◽  
M. Atiar RAHMAN ◽  
Munir JAMAL ◽  
T. Douglas BRADLEY
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Continuous Positive Airway Pressure ◽  
Tidal Volume ◽  
Spontaneous Breathing ◽  
Airway Pressure ◽  
Breathing Pattern ◽  
Positive Airway Pressure ◽  
Left Ventricular Ejection ◽  
Breathing Frequency

1.Sympathetic activation in congestive heart failure indicates a poor prognosis. Haemodynamic correlates of increased sympathetic nerve traffic to muscle (MSNA) and to the heart have been well characterized, but these account for only 50 to 60% of the variance in sympathetic activity between patients. 2.In healthy subjects, breathing pattern modulates MSNA and positive airway pressure consistently increases MSNA. However, in patients with heart failure, the influence of spontaneous breathing pattern and of short-term application of nasal continuous positive airway pressure on MSNA have not been described. 3.Spontaneous breathing frequency, tidal volume, end-expiratory lung volume, Pco2 and MSNA were recorded, along with blood pressure, heart rate and stroke volume in 14 men with congestive heart failure of idiopathic or ischaemic origin (left ventricular ejection fraction < 35%). Measurements were made during baseline rest, followed by 45 ;min of either nasal continuous positive airway pressure applied at 10 ;cmH2O (n = 9), or spontaneous breathing, in the absence of nasal continuous positive airway pressure (time control; n = 6). 4.At baseline, there was a significant positive correlation between MSNA burst frequency and breathing frequency (r = 0.758, P = 0.001), and an inverse correlation between MSNA burst incidence and tidal volume (r = -0.705, P = 0.005). These relationships were independent of left ventricular ejection fraction, stroke volume or cardiac output. 5.Nasal continuous positive airway pressure increased end-expiratory lung volume, but had no effect on breathing frequency, tidal volume or MSNA. 6.In patients with congestive heart failure, there is a significant independent and previously unrecognized correlation between spontaneous breathing pattern and MSNA; patients with rapid shallow breathing exhibit the highest degree of sympathetic activation. In distinct contrast to healthy subjects, the short-term application of nasal continuous positive airway pressure at 10 ;cmH2O does not increase MSNA in congestive heart failure.

Influence of exercise and CO2 on breathing pattern of normal man

1979 ◽  
Vol 47 (1) ◽  
pp. 192-196 ◽  
Author(s):  
J. Askanazi ◽  
J. Milic-Emili ◽  
J. R. Broell ◽  
A. I. Hyman ◽  
J. M. Kinney
Keyword(s):  
Tidal Volume ◽  
Duty Cycle ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Inspiratory Flow ◽  
Breathing Frequency ◽  
Inspiratory Time ◽  
Noninvasive Measurements ◽  
Normal Man

Ventilatory patterns during rest, CO2 inhalation (2, 3, and 4%) and three levels of exercise were analyzed in supine men using a canopy system for noninvasive measurements. Changes in tidal volume (VT) and breathing frequency (f) with equal increases in minute ventilation (VE) differed significantly during exercise and CO2 inhalation. Increases in VE during exercise was accompanied by increases in VT and f. During CO2 inhalation, the change in frequency was less than during exercise. However, when analyzed in terms of inspiratory flow (VT/TI) and inspiratory duty cycle (TI/Ttot), the response to both stimuli was similar. With increases to twice control VE both TI/Ttot and VT/VI increased. Thereafter only VTTI increased with increasing VE. At rest, inspiratory time on a breath by breath basis increased minimally with VT, while changes in inspiratory flow accounted for the variability in VT. These two respiratory stimulants appear to increase ventilation through different mechanisms when analyzed in terms of VT and f. However, changes in inspiratory flow and duty cycle are similar in both.

Mechanical work of breathing during exercise in trained and untrained subjects

1962 ◽  
Vol 17 (1) ◽  
pp. 43-46 ◽  
Author(s):  
G. Milic-Emili ◽  
J. M. Petit ◽  
R. Deroanne
Keyword(s):  
Oxygen Uptake ◽  
Tidal Volume ◽  
Work Of Breathing ◽  
Pulmonary Ventilation ◽  
Esophageal Pressure ◽  
Bicycle Ergometer ◽  
Mechanical Work ◽  
Trained Subjects

The mechanical work of breathing was measured from simultaneous records of esophageal pressure and tidal volume on seven well trained and seven untrained subjects exercising on a bicycle ergometer. At any given value of pulmonary ventilation, mechanical work of breathing was found to be the same for untrained and trained subjects. At any given value of oxygen uptake, pulmonary ventilation and, accordingly, mechanical work of breathing were found to be smaller in trained than in untrained individuals. Submitted on June 9, 1961

The role of vagal afferent information and hypercapnia in control of the breathing pattern in chelonia

1980 ◽  
Vol 87 (1) ◽  
pp. 53-63 ◽  
Author(s):  
W. K. Milsom ◽  
D. R. Jones
Keyword(s):  
Tidal Volume ◽  
Gas Flow ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Respiratory Frequency ◽  
Breath Holding ◽  
Large Variability ◽  
Flow Rates ◽  
Afferent Information

The normal breathing pattern of the turtle, Chrysemys picta (Schneider), consists of periods of continuous breathing interspersed with periods of breath holding. During each ventilatory period respiratory frequency and tidal volume are controlled independently. There is a large variability in inspiratory and expiratory gas-flow rates yet tidal volumes are maintained within narrow limits by adjustments of the lengths of the active inspiratory and expiratory intervals. Lung volume information carried within the vagus nerve is responsible for the careful regulation of tidal volume as well as for modulation of the air flow rates and lowering of the threshold of the mechanism initiating expiration following breath holding. Increases in pulmonary minute ventilation during hypercapnia are caused by increases in respiratory frequency due solely to a shortening of the periods of breath holding. There is some increase in tidal volume but the breath length remains constant and thus the frequency of breathing within each ventilatory period also remains constant. After vagotomy, changes in minute ventilation due to hypercapnia stem primarily from changes in tidal volume while changes in respiratory frequency are greatly reduced.

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