CHEMORECEPTOR REFLEXES IN THE NEWBORN INFANT: EFFECT OF COOLING ON THE RESPONSE TO HYPOXIA

PEDIATRICS ◽  
1966 ◽  
Vol 37 (4) ◽  
pp. 556-564 ◽  
Author(s):  
Eliana Ceruti
Keyword(s):  
Heart Rate ◽  
Newborn Infant ◽  
Environmental Temperature ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Term Infants ◽  
Ambient Temperatures ◽  
Thermal Environments ◽  
Warm Environment ◽  
Cool Environment

1. The effect of brief exposures to warm and cool environments on the newborn infant's response to hypoxia was studied in 14 healthy full-term infants. 2. In all infants studied in a cool environment minute ventilation was significantly higher while breathing 21% O2. 3. During the first week of life, hypoxia (12% O2) induced a transient hyperventilation in babies studied in a warm environment. This response was not seen when the infants were in a cool environment. The ventilatory response was the same even when the PACOACO2 was maintained constant and elevated. A decrease in ventilation and return to control levels after 21% O2 was reinstituted, occurred at both thermal environments. 4. PACOACO2 decreased during hypoxia, at both ambient temperatures. 5. Heart rate increased significantly during hypoxia and was not affected by the environmental temperature or age. 6. The ventilatory response to 3% CO2 inhalation was unaffected by temperature or age. 7. After the first week of life, a sustained hyperventilation during hypoxia occurred at both ambient temperatures.

Control of ventilation in elite synchronized swimmers

1987 ◽  
Vol 63 (3) ◽  
pp. 1019-1024 ◽  
Author(s):  
R. L. Bjurstrom ◽  
R. B. Schoene
Keyword(s):  
Heart Rate ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Mean Value ◽  
Heart Rate Change ◽  
Breath Holding ◽  
Breath Hold ◽  
Lung Volumes ◽  
Co2 Partial Pressure ◽  
Control Of Ventilation

Synchronized swimmers perform strenuous underwater exercise during prolonged breath holds. To investigate the role of the control of ventilation and lung volumes in these athletes, we studied the 10 members of the National Synchronized Swim Team including an olympic gold medalist and 10 age-matched controls. We evaluated static pulmonary function, hypoxic and hypercapnic ventilatory drives, and normoxic and hyperoxic breath holding. Synchronized swimmers had an increased total lung capacity and vital capacity compared with controls (P less than 0.005). The hypoxic ventilatory response (expressed as the hyperbolic shape parameter A) was lower in the synchronized swimmers than controls with a mean value of 29.2 +/- 2.6 (SE) and 65.6 +/- 7.1, respectively (P less than 0.001). The hypercapnic ventilatory response [expressed as S, minute ventilation (1/min)/alveolar CO2 partial pressure (Torr)] was no different between synchronized swimmers and controls. Breath-hold duration during normoxia was greater in the synchronized swimmers, with a mean value of 108.6 +/- 4.8 (SE) vs. 68.03 +/- 8.1 s in the controls (P less than 0.001). No difference was seen in hyperoxic breath-hold times between groups. During breath holding synchronized swimmers demonstrated marked apneic bradycardia expressed as either absolute or heart rate change from basal heart rate as opposed to the controls, in whom heart rate increased during breath holds. Therefore the results show that elite synchronized swimmers have increased lung volumes, blunted hypoxic ventilatory responses, and a marked apneic bradycardia that may provide physiological characteristics that offer a competitive advantage for championship performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of oxygen inhalation on cold thresholds

1963 ◽  
Vol 18 (6) ◽  
pp. 1057-1060
Author(s):  
D. M. MacCanon ◽  
J. Resnik
Keyword(s):  
Environmental Temperature ◽  
Oxygen Effect ◽  
Cold Sensation ◽  
Variable Intensity ◽  
Ambient Temperatures ◽  
Oxygen Breathing ◽  
Oxygen Inhalation ◽  
Cold Source ◽  
Cool Environment ◽  
Effect Of Oxygen

The effect of oxygen inhalation on cutaneous thresholds for cold sensation was determined by exposing a 50-cm2 area on the chest to a radiant cold source of variable intensity for 2-sec intervals in 11 healthy 23- to 26-yr-old nude subjects at two ambient temperatures. Oxygen breathing produced a similar significant increase in cold thresholds in both cool (22.4–26.5 C) and warm (36.6–39.3 C) environments. Observations at warm ambient temperatures substantiate the oxygen effect independent of suspected reflex vasoconstriction in the cool environment. environmental temperature Submitted on March 18, 1963

The adaptation of energy utilization in the laying hen to warm and cool ambient temperatures

1972 ◽  
Vol 79 (2) ◽  
pp. 363-369 ◽  
Author(s):  
R. H. Davis ◽  
O. E. M. Hassan ◽  
A. H. Sykes
Keyword(s):  
Body Weight ◽  
Energy Intake ◽  
Heat Production ◽  
Egg Production ◽  
Energy Utilization ◽  
Ambient Temperatures ◽  
Warm Environment ◽  
Cool Environment ◽  
High Level ◽  
Energy Balances

SUMMARYTwo experiments have been performed to study the acclimatization of laying hens to cool or warm environmental temperature, using the comparative slaughter procedure to measure energy utilization. In the first experiment the energy balances over a 3-week period at either 10 or 35 °C were compared; in the second experiment a comparison was made of the energy balances over six consecutive weekly periods at similar cool and warm temperatures.The first experiment confirmed that production could be maintained (88%) in the warm environment even though food intake was markedly reduced (95 and 63 g/day at 10 and 35 °C respectively). In both environments a loss of body weight indicated, that energy intake was insufficient to meet demands for at least part of the period.During the first week of the second experiment there was a small loss of body weight in the cool environment and food consumption was slightly depressed. The results for energy intake, egg production and heat production suggest that acclimatization was complete after 1 week. In the warm environment egg production fell initially (62%) but returned to a high level (86%) during the second week. However, energy intake, body weight and heat production did not reach steady levels until the fourth week. Comparing the first 3 weeks with the subsequent 3 weeks the daily ME consumption was 137 and 161 kcal/kg¾ and the daily heat production was 126 and 116 kcal/kg¾. Similar, although less marked differences were observed in the cool environment. These results therefore emphasize the need to allow adequate time for acclimatization to the environment in studies of energy metabolism.

Responses to Exercise in Normobaric Hypoxia: Comparison of Elite and Recreational Ski Mountaineers

2014 ◽  
Vol 9 (6) ◽  
pp. 978-984 ◽  
Author(s):  
Raphael Faiss ◽  
Claudia von Orelli ◽  
Olivier Dériaz ◽  
Grégoire P. Millet
Keyword(s):  
Heart Rate ◽  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Hypobaric Hypoxia ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Normobaric Hypoxia ◽  
Hypoxic Ventilatory Response ◽  
Treadmill Test ◽  
National Team

Purpose:Hypoxia is known to reduce maximal oxygen uptake (VO2max) more in trained than in untrained subjects in several lowland sports. Ski mountaineering is practiced mainly at altitude, so elite ski mountaineers spend significantly longer training duration at altitude than their lower-level counterparts. Since acclimatization in hypobaric hypoxia is effective, the authors hypothesized that elite ski mountaineers would exhibit a VO2max decrement in hypoxia similar to that of recreational ski mountaineers.Methods:Eleven elite (E, Swiss national team) and 12 recreational (R) ski mountaineers completed an incremental treadmill test to exhaustion in normobaric hypoxia (H, 3000 m, FIO2 14.6% ± 0.1%) and in normoxia (N, 485 m, FIO2 20.9% ± 0.0%). Pulse oxygen saturation in blood (SpO2), VO2max, minute ventilation, and heart rate were recorded.Results:At rest, hypoxic ventilatory response was higher (P < .05) in E than in R (1.4 ± 1.9 vs 0.3 ± 0.6 L · min−1 · kg−1). At maximal intensity, SpO2 was significantly lower (P < .01) in E than in R, both in N (91.1% ± 3.3% vs 94.3% ± 2.3%) and in H (76.4% ± 5.4% vs 82.3% ± 3.5%). In both groups, SpO2 was lower (P < .01) in H. Between N and H, VO2max decreased to a greater extent (P < .05) in E than in R (–18% and –12%, P < .01). In E only, the VO2max decrement was significantly correlated with the SpO2 decrement (r = .74, P < .01) but also with VO2max measured in N (r = .64, P < .05).Conclusion:Despite a probable better acclimatization to altitude, VO2max was more reduced in E than in R ski mountaineers, confirming previous results observed in lowlander E athletes.

Intracisternal DIDS enhances ventilatory response to rebreathing CO2 in rats

1988 ◽  
Vol 65 (4) ◽  
pp. 1611-1616 ◽  
Author(s):  
J. M. Adams ◽  
N. L. Johnson
Keyword(s):  
Heart Rate ◽  
Cerebrospinal Fluid ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Ventral Surface ◽  
Anion Transport ◽  
Disulfonic Acid ◽  
Respiratory Response ◽  
Transport Inhibitor ◽  
Ventilation Response

In 11 anesthetized rats, we tested the hypothesis that carrier-mediated anion transport in part determines the medullary chemoreceptor response to acute hypercapnia by infusing the transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in mock cerebrospinal fluid (CSF) into the cisterna magna. In five additional rats with sham CSF infusion, we found no effect of mock CSF on the response to rebreathing CO2. Dye infused into the cistern stained the putative chemoreceptor areas on the ventral surface of the medulla. DIDS, at 10 to 1,000 nM, increased the respiratory response to CO2 in a dose-related manner but had no effect on arterial pressure or heart rate. At 1,000 nM, the hypercapnic minute ventilation response was almost doubled because of both volume and rate of breathing. We conclude that the net effect of anion transport is to mitigate the stimulus to the medullary chemoreceptors during acute hypercapnia.

Effects of environmental temperature on the venodilatory response to nitroglycerin

1991 ◽  
Vol 71 (5) ◽  
pp. 1843-1847
Author(s):  
J. A. Gascho ◽  
D. Gehman ◽  
R. Brandt
Keyword(s):  
Vascular Resistance ◽  
Environmental Temperature ◽  
Forearm Blood Flow ◽  
Venous Pressure ◽  
Young Male ◽  
Warm Environment ◽  
Cool Environment ◽  
Venous Distensibility ◽  
Venous Volume ◽  
Forearm Vascular Resistance

The venodilatory response to nitroglycerin (0.8 mg sublingually) was measured in 10 healthy young male volunteers in a cool [24.3 +/- 0.6 degrees C skin temperature (Tsk)] and a warm environment (34.7 +/- 0.2 degrees C Tsk). Nitroglycerin caused mean arterial pressure to fall and heart rate to rise in both the cool (105 +/- 2 to 96 +/- 3 mmHg; 55 +/- 3 to 62 +/- 3 beats/min) and the warm environment (87 +/- 3 to 81 +/- 3 mmHg; 66 +/- 4 to 75 +/- 3 beats/min), but the fall in pressure was greater in the cool than in the warm environment. Forearm blood flow was reduced and forearm vascular resistance elevated in the cool (117 +/- 19 units; 1.15 +/- 0.08 ml.100 cc arm-1.min-1) compared with the warm environment (15 +/- 3 units; 8.60 +/- 1.89 ml.100 cc arm-1.min-1). Nitroglycerin caused forearm vascular resistance to fall in the cool but had no effect in the warm environment. Venous distensibility (increase in venous volume per 30-mmHg increase in venous pressure) was twice as great in the warm as in the cool environment (3.90 +/- 0.27 vs. 1.88 +/- 0.23 ml/100 cc arm). However, the venodilatory effect of nitroglycerin was similar in the cool and warm environments (0.79 +/- 0.10 vs. 0.67 +/- 0.13 ml/100 cc arm, respectively). Arterioles are not dilated by nitroglycerin in the warmer environment, but the venodilatory effect of nitroglycerin is quantitatively similar in the two environments.

Effects of temperature on ventilatory response to hypercapnia in newborn mice heterozygous for transcription factor Phox2b

2007 ◽  
Vol 293 (5) ◽  
pp. R2027-R2035 ◽  
Author(s):  
N. Ramanantsoa ◽  
V. Vaubourg ◽  
B. Matrot ◽  
G. Vardon ◽  
S. Dauger ◽  
...  
Keyword(s):  
Heart Rate ◽  
Transcription Factor ◽  
Temperature Regulation ◽  
Ventilatory Response ◽  
Whole Body ◽  
Wild Type ◽  
Newborn Mice ◽  
Phox2b Gene ◽  
Ambient Temperatures ◽  
Hypercapnic Ventilatory Response

Congenital central hypoventilation syndrome (CCHS) is a rare disease with variable severity, generally present from birth and chiefly characterized by impaired chemosensitivity to hypercapnia. The main cause of CCHS is a mutation in the PHOX2B gene, which encodes a transcription factor involved in the development of autonomic medullary reflex pathways. Temperature regulation is abnormal in many patients with CCHS. Here, we examined whether ambient temperature influenced CO2 sensitivity in a mouse model of CCHS. A weak response to CO2 at thermoneutrality (32°C) was noted previously in 2-day-old mice with an invalidated Phox2b allele ( Phox2b+/−), compared with wild-type littermates. We exposed Phox2b+/− pups to 8% CO2 at three ambient temperatures (TAs): 29°C, 32°C, and 35°C. We measured breathing variables and heart rate (HR) noninvasively using a novel whole body flow plethysmograph equipped with contact electrodes. Body temperature and baseline breathing increased similarly with TA in mutant and wild-type pups. The hypercapnic ventilatory response increased linearly with TA in both groups, while remaining smaller in mutant than in wild-type pups at all TAs. The differences between the absolute increases in ventilation in mutant and wild-type pups become more pronounced as temperature increased above 29°C. The ventilatory abnormalities in mutant pups were not associated with significant impairments of heart rate control. In both mutant and wild-type pups, baseline HR increased with TA. In conclusion, TA strongly influenced the hypercapnic ventilatory response in Phox2b+/− mutant mice. These findings suggest that abnormal temperature regulation may contribute to the severity of respiratory impairments in CCHS patients.

CHEMORECEPTOR REFLEXES IN THE NEWBORN INFANT: EFFECT OF CO2 ON THE VENTILATORY RESPONSE TO HYPOXIA

PEDIATRICS ◽  
1970 ◽  
Vol 45 (2) ◽  
pp. 206-215
Author(s):  
June P. Brady ◽  
P. M. Dunn
Keyword(s):  
Newborn Infant ◽  
Ventilatory Response ◽  
Depressant Effect ◽  
Term Infants ◽  
Stimulant Effect ◽  
Co2 Levels ◽  
Ventilatory Response To Hypoxia

In the newborn infant, hypoxia has an initial stimulant but secondary depressant effect on breathing. To find out whether CO2 would augment this response, eight healthy term infants (6 hr to 11 days) were made hypoxic (Pao2, 60 mm Hg) at three different CO2 levels on 13 occasions. Ventilation was unaffected by 0.2% CO2 in air (Pao2, 110 mm Hg) and increased 6% with 0.2% CO2 plus hypoxia; with 2.3% CO2 there was a 43% increase in breathing at a Pao2 of 110 mm Hg and a 52% increase with hypoxia; with 4.4% CO2 there was a 151% increase at a Pao2 of 110 mm Hg and a 179% increase with hypoxia. This additional hyperventilation was poorly sustained, except in the 11-day-old infant, and breathing tended to decrease during the second and third minutes of hypoxia. In six additional infants, a small but significant decrease in capillary pH occurred with 4.4% CO2 plus hypoxia. Our findings suggest that CO2 does augment the initial stimulant effect of hypoxia in the newborn infant, but this is not sustained. The failure to maintain hyperventilation with hypoxia conveys no apparent benefit to the newborn infant.

Naloxone reduces decrease in ventilation induced by hypoxia in newborn infants

1984 ◽  
Vol 56 (6) ◽  
pp. 1507-1511 ◽  
Author(s):  
C. De Boeck ◽  
P. Van Reempts ◽  
H. Rigatto ◽  
V. Chernick
Keyword(s):  
Newborn Infant ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Newborn Infants ◽  
Periodic Breathing ◽  
Endogenous Opiates ◽  
Fractional Concentration ◽  
Ventilatory Pattern ◽  
Breathing Room ◽  
Sustained Increase

The mechanism responsible for the decrease in ventilation during breathing of low fractional concentration of inspired O2 in the newborn infant is poorly understood. The present study tested the hypothesis that endogenous opiates account for this ventilatory decrease. Eleven healthy newborn infants breathed 15% O2, balance N2 for 5 min following an injection of saline and following an injection of naloxone. Neither injection caused a change in minute ventilation (VE) or ventilatory pattern when the infants were breathing room air. However, the decreased ventilation during hypoxia following naloxone was significantly less than that following saline. VE dropped about 14% following saline but only about 4% following naloxone. However, the adult ventilatory response to hypoxemia, i.e., a relatively sustained increase in VE, was not attained. Naloxone had no influence on the occurrence of periodic breathing during hypoxemia. Thus in the healthy full-term newborn infant, endogenous opiates account only for a part of the decreased ventilation during hypoxemia.

Transient ventilatory response to CO2 as a function of sleep state in full-term infants

1983 ◽  
Vol 54 (6) ◽  
pp. 1482-1488 ◽  
Author(s):  
J. V. Anderson ◽  
R. J. Martin ◽  
E. F. Abboud ◽  
I. Z. Dyme ◽  
E. N. Bruce
Keyword(s):  
Steady State ◽  
Ventilatory Response ◽  
Minute Ventilation ◽  
Full Term ◽  
Initial Increase ◽  
Sleep State ◽  
Term Infants ◽  
Co2 Partial Pressure ◽  
End Tidal ◽  
Ventilatory Response To Co2

The influence of sleep state on the transient (i.e., initial 60 s) and steady-state ventilatory responses to 2% CO2 inhalation was studied in 19 healthy full-term infants. A nasal mask pneumotachometer was used to measure ventilation and end-tidal CO2 partial pressure (PCO2) and enabled abrupt changes in the inspired gas concentration to be made. The magnitude of the change in minute ventilation for both the transient and steady-state responses to CO2 was not statistically different between active (AS) and quiet (QS) sleep. Nonetheless the greater variability in minute ventilation during AS compared with QS continued throughout the period of CO2 inhalation and was associated with a more variable change in ventilation in the individual infants during AS. There was a greater increase in end-tidal PCO2 over the first 60 s during AS (3.3 +/- 0.3 vs. 2.6 +/- 0.2 Torr, in AS and QS, respectively, P less than 0.03). This may indicate a smaller initial increase in alveolar ventilation, relative to CO2 delivery to the lungs, in response to CO2 inhalation during AS. Asynchronous chest wall movements were more common during AS than QS (P less than 0.005) and did not change with CO2. The inconsistent transient ventilatory response to CO2 during AS compared with QS may be important in the behavior of infants to spontaneous episodes of hypercapnia occurring during AS.

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