Ventilation volume as a stimulus to spontaneous ventilation after prolonged artificial ventilation

Smith, Alison C.; Spalding, J. M. K.; Watson, W. E.

doi:10.1113/jphysiol.1962.sp006830

Cited by 27 publications

(17 citation statements)

References 10 publications

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“…As the level of pCO2 rises during the experiment, so a ventilatory response occurs and the ventilation increases during the rebreathing periods. It has been shown that hyperventilation may cause the central respiratory mechanisms to habituate to a new level of ventilation even when the pCO2 is prevented from falling [Smith et al, 1961]. In our experiments, a short period of severe isocapnic hyperventilation did not displace the breath holding-CO2 response curve, which suggests that the pattern of breathing has little effect on a subsequent breath hold.…”

Section: Discussioncontrasting

confidence: 40%

Mechanical and Chemical Control of Breath Holding

Godfrey

Campbell

1969

Exp Physiol

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A method is described for the study of breath holding in which the breath holds are separated by rebreathing to enable accurate control of pCO2; its theoretical basis is discussed.At the end of a breath hold, rebreathing a mixture such that the pCO2 continues to rise, nevertheless permits the breath hold to be resumed. The number of breaths during the rebreathing is unimportant and a single breath permits as long a resumed breath hold as five breaths.Healthy adult males held their breath at residual volume. The relationship between breath holding time and pCO2 at the start or end of a breath hold was found to be linear; the higher the pCO2 the shorter the breath holding time. The relationship was unaffected by ten minutes of isocapnic hyperventilation.These findings imply that the duration of breath holding is directly related to PCO2 but is unaffected by the previous mechanical pattern of breathing.MOST of the factors of importance in determining the breaking point of breath holding have been known for many years. Hill and Flack [1908] noted that if oxygen was breathed beforehand rather than air, the breath holding time was longer. They also noted that the alveolar pCO2 (hereafter referred to as pCO2) was higher at breaking point after breath holding on oxygen; this was presumably due to the longer duration of breath holding.In the same paper they reported that their subjects could rebreathe expired air from a bag for some two to four times as long as their maximum breath holding time on air. They thus demonstrated that ventilation of the lungs allowed the subject to tolerate a greater hypoxia and greater hypercapnia than occurred at the breaking point of breath holding. This finding, now some sixty years old, suggests that some form of interaction of chemicall and mechanical stimuli occurs during breath holding. Subsequent studies defined the roles of oxygen, CO2 and lung volume more clearly [Douglas and Haldane, 1909;Klocke and Rahn, 1959;Muxworthy, 1951] and the whole subject has been reviewed by Mithoefer [1964]. The relationship between rebreathing and breath holding was further explored by Fowler [1954]. He found that after subjects had reached the breaking point of a breath hold, a few breaths of a gas mixture which did not improve their blood gases allowed them to perform a second, shorter breath hold, and subsequently a third. He did not attempt to determine the number of breaths necessary to allow the second (or third) breath hold of the series.

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Section: Discussioncontrasting

confidence: 40%

Mechanical and Chemical Control of Breath Holding

Godfrey

Campbell

1969

Exp Physiol

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“…Smith et al (181,182) found that in partially paralyzed individuals, altered ventilation or ventilatory pattern imposed by a respirator tended to perpetuate itself when the respirator was discontinued. This was demonstrable when the PCO, was kept constant by varying the dead space of the respiratory support circuit, but the greatest persistence of ventilation occurred when hypocapnia was allowed to develop.…”

Section: Role Of Hypocapniu and Hyperventilationmentioning

confidence: 99%

Ventilatory Control at High Altitude

Weil

1986

Comprehensive Physiology

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FIG. 2. Oxygen-tension (P4) cascade at low and high altitude.At high altitude, fall in P, for each step from tracheal or inspired air to venous circulation is decreased. One of the greatest decreases is that from inspired to alveolar air, which largely reflects increased ventilation at high altitude. [Adapted from Hurtado (105).] CHAPTER 21: VENTILATORY CONTROL AT HIGH ALTITUDE 705 /Y lr pace, pace, FIG. 3. Contrast of acid-base and oxygenation effects on ventilatory response to CO2. Acid-base alterations shift curve position (intercept) with little or no change in slope, whereas changes in O2 tension (P ) mainly influence the slope. P b , , arterial partial pressure of'%oz.

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“…1, 2). This is due to the part played by ventilation volume in spontaneous ventilation in these circumstances (Smith et al 1962); the presence of the horizontal portion of the curve does not alter the position of the steep part. The change in V/pCO2 curves which occurs within a few hours may take the form of either a lateral shift or a change in slope.…”

Section: Discussionmentioning

confidence: 94%

“…which is less than the upper-airway dead space eliminated by the tracheotomy. Details of the artificial ventilation and of the methods of C02 AFTER ARTIFICIAL VENTILATION 33 measuring ventilation volume (V) and end-tidal pCO2 during artificial and spontaneous ventilation have already been described (Smith, Spalding & Watson, 1962). All gas volumes are expressed at ambient temperature and pressure, and saturated with water vapour.…”

Section: Methodsmentioning

confidence: 99%