scholarly journals The principle of upper airway unidirectional flow facilitates breathing in humans

2008 ◽  
Vol 105 (3) ◽  
pp. 854-858 ◽  
Author(s):  
Yandong Jiang ◽  
Yafen Liang ◽  
Robert M. Kacmarek
Keyword(s):  
Respiratory Distress ◽  
Tidal Volume ◽  
Dead Space ◽  
Breathing Pattern ◽  
Heat Removal ◽  
Upper Airway ◽  
Random Order ◽  
Water Evaporation ◽  
Breathing Patterns ◽  
Anatomical Dead Space

Upper airway unidirectional breathing, nose in and mouth out, is used by panting dogs to facilitate heat removal via water evaporation from the respiratory system. Why some humans instinctively employ the same breathing pattern during respiratory distress is still open to question. We hypothesized that 1) humans unconsciously perform unidirectional breathing because it improves breathing efficiency, 2) such an improvement is achieved by bypassing upper airway dead space, and 3) the magnitude of the improvement is inversely proportional to the tidal volume. Four breathing patterns were performed in random order in 10 healthy volunteers first with normal breathing effort, then with variable tidal volumes: mouth in and mouth out (MMB); nose in and nose out (NNB); nose in and mouth out (NMB); and mouth in and nose out (MNB). We found that unidirectional breathing bypasses anatomical dead space and improves breathing efficiency. At tidal volumes of ∼380 ml, the functional anatomical dead space during NMB (81 ± 31 ml) or MNB (101 ± 20 ml) was significantly lower than that during MMB (148 ± 15 ml) or NNB (130 ± 13 ml) (all P < 0.001), and the breathing efficiency obtained with NMB (78 ± 9%) or MNB (73 ± 6%) was significantly higher than that with MMB (61 ± 6%) or NNB (66 ± 3%) (all P < 0.001). The improvement in breathing efficiency increased as tidal volume decreased. Unidirectional breathing results in a significant reduction in functional anatomical dead space and improvement in breathing efficiency. We suggest this may be the reason that such a breathing pattern is preferred during respiratory distress.

Normoxic and hypoxic breathing pattern in newborn grey seals

1989 ◽  
Vol 67 (2) ◽  
pp. 483-487 ◽  
Author(s):  
Jacopo P. Mortola ◽  
Clement Lanthier
Keyword(s):  
Tidal Volume ◽  
Breathing Pattern ◽  
Halichoerus Grypus ◽  
Breathing Rate ◽  
Allometric Relationships ◽  
Breathing Patterns ◽  
Hypoxic Conditions ◽  
Regulation Of Breathing ◽  
Expiratory Flow

We studied the breathing patterns of three newborn grey seals (Halichoerus grypus) at 2 – 3 days of age under normoxic and hypoxic conditions with the barometric technique, which does not require the animal to be restrained. Normoxic tidal volume was deeper and breathing rate slower than expected for newborns of this size on the basis of previously published allometric relationships. In addition, two characteristics were readily apparent: (i) occasional sudden long apneas, often exceeding 30 s in duration, and (ii) consistent brief interruptions of expiratory flow. Neither aspect is common in terrestrial newborns of this age, but both have been previously observed in adult seals. During hypoxia (10 min of 15% O2 and 10 min of 10% O2), ventilation increased markedly and steadily, at variance with what occurs in newborns of other species, indicating a precocial development of the regulation of breathing. This latter result also suggests that the blunted response to hypoxia previously reported in adult seals may be acquired postnatally with diving experience.

Effect of respiratory apparatus on respiration

1984 ◽  
Vol 57 (2) ◽  
pp. 475-480 ◽  
Author(s):  
C. Weissman ◽  
J. Askanazi ◽  
J. Milic-Emili ◽  
J. M. Kinney
Keyword(s):  
Tidal Volume ◽  
Duty Cycle ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Inspiratory Flow ◽  
Percentage Increase ◽  
Breathing Patterns ◽  
Normal Volunteers ◽  
Abdominal Operation ◽  
Respiratory Apparatus

A mouthpiece plus noseclip (MP & NC) is frequently used in performing measurements of breathing patterns. Although the effects the apparatus exerts on breathing patterns have been studied, the mechanism of the changes it causes remains unclear. The current study examines the effects on respiratory patterns of a standard (17-mm-diam) MP & NC during room air (RA) breathing and the administration of 2 and 4% CO2 in normal volunteers and in patients 2–4 days after abdominal operation. When compared with values obtained with a noninvasive canopy system, the MP & NC induced increases in minute ventilation (VE), tidal volume (VT), and mean inspiratory flow (VT/TI), but not frequency (f) or inspiratory duty cycle, during both RA and CO2 administration. The percentage increase in VE, VT, and VT/TI caused by the MP & NC decreased as the concentration of CO2 increased. During RA breathing, the application of noseclip alone resulted in a decrease in f and an increase in VT, but VE and VT/TI were unchanged. The changes were attenuated during the administration of 2 and 4% CO2. Reducing the diameter of the mouthpiece to 9 mm abolished the alterations in breathing pattern observed with the larger (17-mm) diameter MP.

scholarly journals Nasal high flow reduces minute ventilation during sleep through a decrease of carbon dioxide rebreathing

2019 ◽  
Vol 126 (4) ◽  
pp. 863-869 ◽  
Author(s):  
Maximilian Pinkham ◽  
Russel Burgess ◽  
Toby Mündel ◽  
Stanislav Tatkov
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Tidal Volume ◽  
Respiratory Rate ◽  
Dead Space ◽  
Minute Ventilation ◽  
Control Ventilation ◽  
High Flow ◽  
Carbon Dioxide Rebreathing ◽  
Anatomical Dead Space

Nasal high flow (NHF) is an emerging therapy for respiratory support, but knowledge of the mechanisms and applications is limited. It was previously observed that NHF reduces the tidal volume but does not affect the respiratory rate during sleep. The authors hypothesized that the decrease in tidal volume during NHF is due to a reduction in carbon dioxide (CO2) rebreathing from dead space. In nine healthy males, ventilation was measured during sleep using calibrated respiratory inductance plethysmography (RIP). Carbogen gas mixture was entrained into 30 l/min of NHF to obtain three levels of inspired CO2: 0.04% (room air), 1%, and 3%. NHF with room air reduced tidal volume by 81 ml, SD 25 ( P < 0.0001) from a baseline of 415 ml, SD 114, but did not change respiratory rate; tissue CO2 and O2 remained stable, indicating that gas exchange had been maintained. CO2 entrainment increased tidal volume close to baseline with 1% CO2 and greater than baseline with 3% CO2 by 155 ml, SD 79 ( P = 0.0004), without affecting the respiratory rate. It was calculated that 30 l/min of NHF reduced the rebreathing of CO2 from anatomical dead space by 45%, which is equivalent to the 20% reduction in tidal volume that was observed. The study proves that the reduction in tidal volume in response to NHF during sleep is due to the reduced rebreathing of CO2. Entrainment of CO2 into the NHF can be used to control ventilation during sleep. NEW & NOTEWORTHY The findings in healthy volunteers during sleep show that nasal high flow (NHF) with a rate of 30 l/min reduces the rebreathing of CO2 from anatomical dead space by 45%, resulting in a reduced minute ventilation, while gas exchange is maintained. Entrainment of CO2 into the NHF can be used to control ventilation during sleep.

Coordination of swallowing and respiration in unconscious subjects

1991 ◽  
Vol 70 (3) ◽  
pp. 988-993 ◽  
Author(s):  
T. Nishino ◽  
K. Hiraga
Keyword(s):  
General Anesthesia ◽  
Tidal Volume ◽  
Endotracheal Tube ◽  
Breathing Pattern ◽  
Recovery Period ◽  
Respiratory Frequency ◽  
Breathing Patterns ◽  
Expiratory Phase ◽  
Unconscious Patients

We investigated the coordination of swallowing and breathing in 11 unconscious patients with an endotracheal tube in place during the recovery period from general anesthesia. Swallows occurred during both the inspiratory and expiratory phases with no preponderant occurrence during either phase. When a swallow occurred during inspiration, the inspiration was interrupted immediately and was followed by expiration, but the durations of both inspiration and expiration were progressively increased as the time from the onset of inspiration to the onset of swallowing was progressively delayed. A swallow coinciding with the expiratory phase progressively prolonged the duration of the expiration that had been interrupted as the timing of swallowing was progressively delayed. Repeated swallows invariably and in a predictable manner caused changes in the breathing pattern. Thus when the frequency of regularly repeated swallows was relatively high, the breathing pattern was characterized by regular, shallow, and rapid breaths. When the frequency of regularly repeated swallows was relatively low, the breathing pattern was characterized by regular, deep, and slow breaths. When the frequency of repeated swallows was irregular, the breathing patterns were characterized by inconsistent changes in tidal volume and respiratory frequency. Our results indicate that, in unconscious subjects, some mechanisms integrating respiration and swallowing are operative and responsible for changes in breathing patterns during swallowing.

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.

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

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.

Human breathing patterns on mouthpiece or face mask during air, CO2, or low O2

1982 ◽  
Vol 53 (5) ◽  
pp. 1281-1290 ◽  
Author(s):  
J. A. Hirsch ◽  
B. Bishop
Keyword(s):  
Steady State ◽  
Tidal Volume ◽  
Elevated Co2 ◽  
Breathing Pattern ◽  
Face Mask ◽  
Simple Consequence ◽  
Breathing Patterns ◽  
Oral Breathing ◽  
Ventilatory Responses ◽  
Breathing Apparatus

Steady-state breathing patterns on mouthpiece and noseclip (MP) and face mask (MASK) during air and chemostimulated breathing were obtained from pneumotachometer flow. On air, all 10 subjects decreased frequency (f) and increased tidal volume (VT) on MP relative to that on MASK without changing ventilation (VE), mean inspiratory flow (VT/TI), or mean expiratory flow (VT/TE). On elevated CO2 and low O2, MP exaggerated the increase in VE, f, and VT/TE due to profoundly shortened TE. On elevated CO2, MASK exaggerated VT increase with little change in f. Increased VE and VT/TI were thus due to increased VT. During low O2 on MASK, both VT and f increased. During isocapnia, shortened TE accounted for increased f; during hypocapnia, increased f was related primarily to shortened TI. Thus the choice of a mouthpiece or face mask differentially alters breathing pattern on air and all components of ventilatory responses to chemostimuli. In addition, breathing apparatus effects are not a simple consequence of a shift from oronasal to oral breathing, since a noseclip under the mask did not change breathing pattern from that on mask alone.

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