Alteration by hyperoxia of ventilatory dynamics during sinusoidal work

1980 ◽  
Vol 48 (6) ◽  
pp. 1083-1091 ◽  
Author(s):  
R. Casaburi ◽  
R. W. Stremel ◽  
B. J. Whipp ◽  
W. L. Beaver ◽  
K. Wasserman
Keyword(s):  
Gas Exchange ◽  
Work Load ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Phase Lag ◽  
Ventilatory Responses ◽  
Load Tests ◽  
The Mean ◽  
End Tidal ◽  
End Tidal Co2

The effects of hyperoxia on ventilatory and gas exchange dynamics were studied utilizing sinusoidal work rate forcings. Five subjects exercised on 14 occasions on a cycle ergometer for 30 min with a sinusoidally varying work load. Tests were performed at seven frequencies of work load during air or 100% O2 inspiration. From the breath-by-breath responses to these tests, dynamic characteristics were analyzed by extracting the mean level, amplitude of oscillation, and phase lag for each six variables with digital computer techniques. Calculation of the time constant (tau) of the ventilatory responses demonstrated that ventilatory kinetics were slower during hyperoxia than during normoxia (P less than 0.025; avg 1.56 and 1.13 min, respectively). Further, for identical work rate fluctuations, end-tidal CO2 tension fluctuations were increased by hyperpoxia. Ventilation during hyperoxia is slower to respond to variations in the level of metabolically produced CO2, presumably because hyperoxia attenuates carotid body output; the arterial CO2 tension is consequently less tightly regulated.

Ventilatory and gas exchange responses to cycling with sinusoidally varying pedal rate

1978 ◽  
Vol 44 (1) ◽  
pp. 97-103 ◽  
Author(s):  
R. Casaburi ◽  
B. J. Whipp ◽  
K. Wasserman ◽  
S. N. Koyal
Keyword(s):  
Carbon Dioxide ◽  
Minute Ventilation ◽  
Small Variation ◽  
Work Load ◽  
Cycle Ergometer ◽  
Carbon Dioxide Tension ◽  
Ventilatory Responses ◽  
Constant Work Rate ◽  
Co2 Flow ◽  
End Tidal

To investigate factors controlling ventilation under conditions where the applied work load remains constant, but where hypothesized proprioceptive influences would be expected to vary, five subjects exercised at a constant work rate of 50 W on a cycle ergometer at pedaling rates which varied sinusoidally between 40 and 80 rpm. Each subject exercised continuously for 30 min at each of five sinusoidal periods. Minute ventilation (VE), carbon dioxide output (VCO2), oxygen uptake (VO2), and heart rate were computed breath-by-breath and amplitude and phase relations were extracted. We observed small fluctuations in VCO2 and VO2 engendered by varying metabolic requirements of moving the legs at varying rates. VE fluctuations were closely in phase with VCO2 and the amplitudes of the fluctuations were highly significantly correlated (r = 0.83, P less than 0.001); consequently end-tidal carbon dioxide tension fluctuations were small. Variation of pedaling rate, therefore, did not produce a ventilatory response independent of the effect of VCO2. The ventilatory responses to these forcings are inconsistent with an appreciable role for neurally mediated influences from the exercising limbs and provide further evidence that the exercise hyperpnea is linked to CO2 flow to the central circulation.

Various Uses of Laryngeal Mask Airway during Tracheal Surgery

2021 ◽  
Author(s):  
Ali Celik ◽  
Muhammet Sayan ◽  
Aykut Kankoc ◽  
Ismail Tombul ◽  
Ismail Cüneyt Kurul ◽  
...  
Keyword(s):  
Postoperative Complications ◽  
Laryngeal Mask Airway ◽  
Tracheal Stenosis ◽  
Laryngeal Mask ◽  
Tracheal Resection ◽  
Tracheal Surgery ◽  
The Mean ◽  
End Tidal ◽  
End Tidal Co2

Abstract Background The use of laryngeal mask airway (LMA) ventilation in surgeries to be performed in upper tracheal stenosis has been reported in the case series. However, there is no generally accepted standardized approach for the use of LMA. In this study, LMA usage areas and advantages of trachea surgery were examined. Methods The records of 21 patients who underwent tracheal surgery using LMA ventilation between March 2016 and May 2020 were evaluated retrospectively. The patient data were analyzed according to age, gender, mean follow-up time, surgical indication, mean tracheal resection length, anastomosis duration, mean oxygen saturation, mean end-tidal CO2 levels, and postoperative complications. Results Four patients were female and 17 were male, their median age was 43 (11–72 range) and the mean follow-up time was 17.6 months. The most common surgical indication was postintubation tracheal stenosis. The mean tracheal resection length was 26.6 mm and the mean anastomosis duration was 11.3 minutes. The mean pulse oximetry and mean end-tidal CO2 during laryngeal mask ventilation was 97.6% ± 2.1 and 38.1 ± 2.8 mm Hg, respectively. Postoperative complications were higher in patients with comorbidities. Conclusion LMA-assisted tracheal surgery is a method that can be used safely as a standard technique in the surgery of benign and malignant diseases of both the upper and lower airway performed on pediatric patients, patients with tracheostomy, and suitable patients with tracheoesophageal fistula.

The Ventilatory Effects of Doxapram in Normal Man

1983 ◽  
Vol 65 (1) ◽  
pp. 65-69 ◽  
Author(s):  
P. M. A. Calverley ◽  
R. H. Robson ◽  
P. K. Wraith ◽  
L. F. Prescott ◽  
D. C. Flenley
Keyword(s):  
Oxygen Uptake ◽  
Ventilatory Response ◽  
Co2 Production ◽  
Central Action ◽  
Ventilatory Responses ◽  
Ventilatory Effects ◽  
Normal Man ◽  
End Tidal ◽  
End Tidal Co2 ◽  
Ventilatory Response To Co2

1. To determine the mode of action of doxapram in man we have measured ventilation, oxygen uptake, CO2 production, hypoxic and hypercapnic ventilatory responses in six healthy men before and during intravenous infusion to maintain a constant plasma level. 2. Doxapram changed neither resting oxygen uptake nor CO2 production but produced a substantial increase in resting ventilation at both levels of end-tidal CO2 studied. 3. Doxapram increased the ventilatory response to isocapnic hypoxia from − 0.8 ± 0.4 litre min−1 (%Sao2)−1 to −1.63 ± 0.9 litres min−1 (%Sao2)−1. This was similar to the increase in hypoxic sensitivity which resulted from raising the end-tidal CO2 by 0.5 kPa without adding doxapram. 4. The slope of the ventilatory response to rebreathing CO2 rose from 11.6 ± 5.3 litres min−1 kPa−1 to 20,4 ± 9.8 litres min−1 kPa−1 during doxapram infusion. 5. The marked increase in the ventilatory response to CO2 implies that doxapram has a central action, but the potentiation of the hypoxic drive also suggests that the drug acts on peripheral chemoreceptors, or upon their central connections, at therapeutic concentrations in normal unanaesthetized subjects.

Relative contributions of hypocarbia and hyperpnea as mechanisms in postexercise asthma

1977 ◽  
Vol 42 (1) ◽  
pp. 22-27 ◽  
Author(s):  
E. R. McFadden ◽  
D. R. Stearns ◽  
R. H. Ingram ◽  
D. E. Leith
Keyword(s):  
Systematic Study ◽  
Dose Response ◽  
Pulmonary Mechanics ◽  
Partial Rebreathing ◽  
The Mean ◽  
Per Se ◽  
Exercise Induced ◽  
End Tidal ◽  
End Tidal Co2

The purpose of this investigation was to assess the relative contributions of hyperpnea and hypocapnia in the induction of postexercise asthma. To achieve these ends, eight young asthmatics were exercised on a treadmill while minute ventilations (VE) and end-tidal CO2 (PET CO2) tensions were continuously recorded. The subjects were then restudied using a partial rebreathing technique that allowed separation of minute and alveolar ventilations so that independent evaluations could be made of the relative effects of bulk airflow on pulmonary mechanics as well as a systematic study of hypocapnia in a dose-response fashion. Sustained hyperpnea with VEidentical to those recorded during exercise was totally without effect when the mean PET CO2 was isocapnic or lowered to approximately 30 Torr. Reduction in PETCO2 to 21.3 +/-0.9 Torr brought about significant changes in mechanics, but in every variable measured, exercise produced the greatest alterations and did so at PETCO2 values that had no effect when studied in a controlled fashion. Consequently, neither high VE per se, nor hypocapnia can be considered as the mechanisms underlying exercise induced asthma.

Breath-by-breath respiratory timing and volume control during periodic breathing

1989 ◽  
Vol 257 (3) ◽  
pp. R653-R660
Author(s):  
D. W. Carley ◽  
C. Maayan ◽  
J. Grimes ◽  
D. C. Shannon
Keyword(s):  
Cross Correlation ◽  
Minute Ventilation ◽  
Periodic Breathing ◽  
Respiratory Pattern ◽  
Volume Control ◽  
Cycle Duration ◽  
Rapid Eye Movement Sleep ◽  
The Mean ◽  
End Tidal ◽  
End Tidal Co2

We examined the control of respiratory pattern during non-rapid-eye-movement sleep-related periodic breathing (PB) in adults, with and without hypoxia. We analyzed 186 cycles of PB from 18 epochs occurring in eight subjects; the mean (+/- SD) cycle duration was 30.8 +/- 8.4 s. Significant oscillations occurred in inspired tidal volume (VT), inspiratory duration (TI), mean inspired flow, inspired minute ventilation, and expiratory duration (TE) (P less than 0.005). For each epoch of PB, moving cross-correlation (MCC) functions were employed to describe the time-dependent intervariable relationships between 1) TI vs. TE, 2) VT vs. TE, and 3) VT vs. breath duration (TT) as synchronization, a strong and consistent intervariable correlation; relative coordination (RC), a weaker interaction characterized by an unstable MCC function oscillating at a subharmonic of the PB frequency; or as independence, with no statistical evidence of interaction. Fourteen epochs showed RC between TI and TE, 11 and 12 of which also showed RC between VT and TE, and VT and TT, respectively. In 4 epochs negative synchronization was exhibited by all three variable pairs. In no case were the oscillations between any pair of variables independent. The modes of coupling between variables were not correlated to O2 saturation, end-tidal CO2 levels, or inspired O2 level. We conclude that during sleep-related PB a nonrandom but weak coupling usually exists between TI and TE, VT and TE, and VT and TT.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of quiet sleep on resting and CO2-stimulated breathing in humans

1981 ◽  
Vol 50 (4) ◽  
pp. 724-730 ◽  
Author(s):  
B. Gothe ◽  
M. D. Altose ◽  
M. D. Goldman ◽  
N. S. Cherniack
Keyword(s):  
Partial Pressure ◽  
Tidal Volume ◽  
Quiet Sleep ◽  
Rib Cage ◽  
Co2 Partial Pressure ◽  
Ventilatory Responses ◽  
Quantitative Measurements ◽  
End Tidal ◽  
End Tidal Co2 ◽  
Different Levels

We examined the effects of different levels of inspired CO2 on ventilation and the pattern of breathing in healthy adults during the awake and the stage II quiet-sleep states. During both states, subjects were studied supine with their heads enclosed in a canopy. Tidal volume (VT) was determined from quantitative measurements of abdominal and rib cage excursions with magnetometers. Inspired CO2 was raised by blending CO2-enriched gas into the airflow, which continuously flushed the canopy. During sleep, while room air was breathed, VT decreased significantly from 410 to 360 ml, and respiratory rate also fell from 17 to 16 breaths/min. As a consequence, ventilation was significantly reduced from 6.5 to 5.8 l/min, and end-tidal CO2 partial pressure (PCO2) rose from 39.1 to 42.5 Torr. Ventilatory responses to CO2 were reduced, on the average, during sleep to 79% of waking levels. The change in average inspiratory flow produced by CO2 was also less during sleep. Waking and sleeping ventilatory responses to CO2 correlated inversely with the rise in end-tidal PCO2 when room air was breathed during sleep. At all levels of VT, the rib cage contribution to VT was greater during quiet sleep than during wakefulness. These findings suggest that quiet sleep, in addition to depressing ventilation and the response to CO2 alters the manner in which VT is attained by rib cage and abdominal displacements.

Kinetics of gas exchange and ventilation in transitions from rest or prior exercise

1977 ◽  
Vol 43 (4) ◽  
pp. 704-708 ◽  
Author(s):  
L. B. Diamond ◽  
R. Casaburi ◽  
K. Wasserman ◽  
B. J. Whipp
Keyword(s):  
Normal Subjects ◽  
Cycle Ergometer ◽  
Work Rate ◽  
Prior Exercise ◽  
Exercise Hyperpnea ◽  
The Mean ◽  
Highly Correlated ◽  
Co2 Flow ◽  
Kinetics Of ◽  
High Work

Seven normal subjects each performed three transitions to a subanaerobic threshold work rate on a cycle ergometer: 1) from rest, 2) from a low work rate (both at 60 rpm), and 3) from a low work rate at 40 rpm to the high work rate at 80 rpm. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) were computed breath-by-breath and response kinetics extracted. The mean half-times of VO2, VCO2, and VE were 32, 44, and 49 s, respectively, and were not appreciably affected by the prior exercise or by variation of pedal rate. The kinetics of VE was highly correlated with VCO2 (r = 0.94), with VCO2 leading VE, providing further description of the relation of the exercise hyperpnea to CO2 flow to the lungs.

Ventilatory responses to dead space and CO2 breathing under inspiratory resistive load

1995 ◽  
Vol 78 (2) ◽  
pp. 555-561 ◽  
Author(s):  
D. A. Sidney ◽  
C. S. Poon
Keyword(s):  
Breathing Pattern ◽  
Human Subjects ◽  
Minute Ventilation ◽  
Resistive Load ◽  
Healthy Human ◽  
Ventilatory Responses ◽  
Ventilatory Pattern ◽  
Volume Relationship ◽  
The Mean ◽  
End Tidal

To investigate how breathing is controlled during CO2 stimulation, steady-state ventilatory responses to rebreathing through a tube (DS) and inspiring a fixed PCO2 (INH) were compared in healthy human subjects. Tests were performed in hyperoxia with (IRL) and without (NL) an inspiratory resistive load (15 cmH2O.l–1.s at 1 l/s). The mean slope of the minute ventilation (VE)-end-tidal PCO2 relationship was significantly higher in DS-IRL than in INH-IRL [1.86 +/- 0.67 (SD) vs. 1.40 +/- 0.32 l.min-1.Torr-1, P < 0.01], and it was significantly different between INH-NL and INH-IRL (1.64 +/- 0.41 vs. 1.40 +/- 0.32 l.min-1.Torr-1, P < 0.05) but not between DS-NL and DS-IRL (1.85 +/- 0.72 vs. 1.86 +/- 0.67 l.min-1.Torr-1). The slope of the VE-tidal volume relationship was significantly lower in DS-NL than in INH-NL (19.6 +/- 3.8 vs. 21.2 +/- 5.1 min-1, P < 0.05), but other comparisons in breathing pattern between NL and IRL and between DS and INH failed to reach significance. We concluded that 1) alterations in alveolar PCO2 temporal profile by DS could induce changes in VE-end-tidal PCO2 sensitivity and ventilatory pattern, 2) these changes may be modified by increased mechanical impairment resulting from IRL, and 3) carotid chemoreceptor mediation is not necessary for the observed effects of DS.

BICYCLE ERGOMETER MEASUREMENT OF MAXIMAL OXYGEN UPTAKE IN CHILDREN

1967 ◽  
Vol 45 (6) ◽  
pp. 937-946 ◽  
Author(s):  
Gordon R. Cumming ◽  
Werner Friesen
Keyword(s):  
Oxygen Uptake ◽  
Pulse Rate ◽  
Maximal Oxygen Uptake ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Cycle Ergometer ◽  
Uptake Curve ◽  
Exercise Tests ◽  
Straight Line ◽  
The Mean

Seven to 15 maximal exercise tests on a cycle ergometer were done on twenty boys, 11 to 15 years of age, until the work load was sufficiently high that it could not be sustained for 3 min. The mean maximal pulse rate was 202 beats/min, and the mean maximal oxygen uptake was 53.8 ml/kg per min. A plateau of the oxygen uptake curve occurred in only 7 of the 20 subjects, whereas the pulse rate reached a plateau in 13 subjects. On the basis of the pulse rate – work load straight line relationship for submaximal exercise, the intensity of the load that the subjects were able to complete was such that a mean predicted pulse rate of 247 beats/min would have resulted. This information can be utilized to obtain maximal oxygen uptake from a single test in children.

Respiratory dead space and arterial to end-tidal CO2 tension difference in anesthetized man

1960 ◽  
Vol 15 (3) ◽  
pp. 383-389 ◽  
Author(s):  
J. F. Nunn ◽  
D. W. Hill
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
Artificial Respiration ◽  
Physiological Dead Space ◽  
Anatomical Dead Space ◽  
The Subject ◽  
The Mean ◽  
The Difference ◽  
End Tidal ◽  
End Tidal Co2

Observations were made during both spontaneous and artificial respiration on 12 fit patients anesthetized for routine surgical procedures. Above a tidal volume of 350 ml (BTPS), the anatomical dead space was close to the predicted normal value for the subject. Below 350 ml, it was reduced in proportion to the tidal volume. The physiological dead space (below the carina) approximated to 0.3 times the tidal volume for tidal volumes between 163 and 652 ml (BTPS). Throughout the range the physiological dead space was considerably in excess of the anatomical dead space measured simultaneously. The difference (alveolar dead space) varied from 15 to 231 ml, being roughly proportional to the tidal volume. The mean arterial to end-tidal CO2 tension difference was 4.6 (S.D. ±2.5) mm Hg and not related to tidal volume or arterial CO2 tension. None of the findings appeared to depend on whether the respiration was spontaneous or artificial. Submitted on September 25, 1959

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