Importance of inspiratory flow rate in the cough response to citric acid inhalation in normal subjects

1990 ◽  
Vol 78 (5) ◽  
pp. 521-525 ◽  
Author(s):  
Manuel J. Barros ◽  
Stefano J. Zammattio ◽  
P. John Rees
Keyword(s):  
Citric Acid ◽  
Flow Rate ◽  
Geometric Mean ◽  
Normal Subjects ◽  
Forced Expiratory Volume ◽  
Inspiratory Flow ◽  
Inspiratory Flow Rate ◽  
Flow Rates ◽  
Cough Response ◽  
The Mean

1. The cough response to inhalation of citric acid is produced mainly by irritation of the larynx and trachea. Variations in the inspiratory flow rate might lead to changes in deposition of the drug, and consequently in the cough threshold. 2. We have studied the effect of three different inspiratory flow rates in 11 normal, non-smoking subjects (nine males, aged 23–39 years), who inhaled nebulized citric acid (2.5–640 mg/l). The test finished when a cough. was produced at each inhalation (cough threshold) or the maximum concentration was reached. 3. The inspiratory flow rate was limited with a fixed resistance and displayed on a screen so that the subjects could reach a constant inspiratory flow rate of 50, 100 and 150 l/min with a submaximal inspiratory effort. 4. The mean (sd) inspiratory flow rates achieved were 51.4 (5.3), 86.2 (16.6) and 134.4 (22.9) l/min. Baseline forced expiratory volume in 1 s and functional vital capacity were not different on the 3 study days. 5. The cough threshold (geometric mean and 95% confidence intervals) was 21 (9–54) mg/l at an inspiratory flow rate of 50 l/min and 43 (13–141) mg/l at 150 l/min (P <0.05). The amount of drug tolerated by the subjects before the cough threshold was achieved was 5.2 (2.0–13.8) mg at an inspiratory flow rate of 50 l/min and 11.6 (3.4–39.8) mg at 150 l/min (P <0.05). The number of coughs per inhalation was 1.6 (1.1–2.0) at an inspiratory flow rate of 50 l/min and 1.1 (0.7–1.5) at 150 l/min (P <0.05). 6. We conclude that lower inspiratory flow rates were associated with a greater cough stimulus in the citric acid challenge procedure used in this study. This may be related to increased laryngeal deposition. The inspiratory flow rate is a variable which should be controlled in the performance of cough challenges with citric acid.

Effect of changes in inspiratory flow rate on cough responses to inhaled capsaicin

1991 ◽  
Vol 81 (s25) ◽  
pp. 539-542 ◽  
Author(s):  
M. J. Barros ◽  
S. L. Zammattio ◽  
P. J. Rees
Keyword(s):  
Citric Acid ◽  
Confidence Interval ◽  
Flow Rate ◽  
Negative Relationship ◽  
Random Order ◽  
Inspiratory Flow ◽  
Inspiratory Flow Rate ◽  
Flow Rates ◽  
Cough Response ◽  
The Difference

1. Twelve non-smoking subjects inhaled capsaicin at three different inspiratory flow rates: 50, 100 and 150 litres/min. Capsaicin was delivered by a breath-actuated dosimeter; inhalations consisted of 0.21–13.6 nmol of capsaicin in doubling amounts given in random order. 2. The mean number of coughs per challenge decreased with increasing inspiratory flow rate. The difference in cough numbers were significant: 7.7 (95% confidence interval 2.5–12.8) for 50 versus 100 litres/min and 10.9 (95% confidence interval 5.0–16.9) for 100 versus 150 litres/min. 3. On a separate day, a cough threshold was measured by giving increasing doses of citric acid that were inhaled at 50 litres/min. There was a positive correlation between the sensitivity to capsaicin and the cough threshold to citric acid (r = 0.69, P = 0.01), and also between the cough latencies (r = 0.67, P = 0.02). 4. The negative relationship between the cough response and the inspiratory flow rate may be caused by increased laryngeal deposition at lower inspiratory flow rates. 5. These results are compatible with a similar anatomical distribution of cough receptors for capsaicin and citric acid. 6. These results suggest that changes in inspiratory flow rate may affect the results of cough challenges.

Influence of inspiratory flow rate and frequency on O2 cost of resistive breathing in humans

1988 ◽  
Vol 65 (2) ◽  
pp. 760-766 ◽  
Author(s):  
D. S. Dodd ◽  
P. W. Collett ◽  
L. A. Engel
Keyword(s):  
Flow Rate ◽  
Duty Cycle ◽  
Normal Subjects ◽  
Work Rate ◽  
Inspiratory Flow ◽  
Inspiratory Flow Rate ◽  
Contraction Frequency ◽  
Mouth Pressure ◽  
Resistive Breathing ◽  
Residual Capacity

We examined the combined effect of an increase in inspiratory flow rate and frequency on the O2 cost of inspiratory resistive breathing (VO2 resp). In each of three to six pairs of runs we measured VO2 resp in six normal subjects breathing through an inspiratory resistance with a constant tidal volume (VT). One of each pair of runs was performed at an inspiratory muscle contraction frequency of approximately 10/min and the other at approximately 30/min. Inspiratory mouth pressure was 45 +/- 2% (SE) of maximum at the lower contraction frequency and 43 +/- 2% at the higher frequency. Duty cycle (the ratio of contraction time to total cycle time) was constant at 0.51 +/- 0.01. However, during the higher frequency runs, two of every three contractions were against an occluded airway. Because VT and duty cycle were kept constant, mean inspiratory flow rate increased with frequency. Careful selection of appropriate parameters allowed the pairs of runs to be matched both for work rate and pressure-time product. The VO2 resp did not increase, despite approximately threefold increases in both inspiratory flow rate and contraction frequency. On the contrary, there was a trend toward lower values for VO2 resp during the higher frequency runs. Because these were performed at a slightly lower mean lung volume, a second study was designed to measure the VO2 resp of generating the same inspiratory pressure (45% maximum static inspiratory mouth pressure at functional residual capacity) at the same frequency but at two different lung volumes. This was achieved with a negligibly small work rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic hypoxia on breathing and EMGs of respiratory muscles in awake ponies

1992 ◽  
Vol 72 (2) ◽  
pp. 739-747 ◽  
Author(s):  
D. R. Brown ◽  
H. V. Forster ◽  
T. F. Lowry ◽  
M. A. Forster ◽  
A. L. Forster ◽  
...  
Keyword(s):  
Flow Rate ◽  
Chronic Hypoxia ◽  
Pulmonary Ventilation ◽  
Inspiratory Flow ◽  
Transversus Abdominis ◽  
Inspiratory Flow Rate ◽  
Arterial Pco2 ◽  
Arterial Blood ◽  
The Mean ◽  
Arterial Po2

Breathing, diaphragmatic and transversus abdominis electromyograms (EMGdi and EMGta, respectively), and arterial blood gases were studied during normoxia (arterial PO2 = 95 Torr) and 48 h of hypoxia (arterial PO2 = 40–50 Torr) in intact (n = 11) and carotid body-denervated (CBD, n = 9) awake ponies. In intact ponies, arterial PCO2 was 7, 5, 9, and 11 Torr below control (P less than 0.01) at 1 and 10 min and 5 and 24–48 h of hypoxia, respectively. In CBD ponies, arterial PCO2 was 3–4 Torr below control (P less than 0.01) at 4, 5, 6, and 24 h of hypoxia. In intact ponies, pulmonary ventilation, mean inspiratory flow rate, and rate of rise of EMGdi and EMGta changed in a multi-phasic fashion during hypoxia; each reached a maximum during the 1st h (P less than 0.05), declined between 1 and 5 h (P less than 0.05), and increased between 5 and 24–48 h of hypoxia. As a result of the increased drive to the diaphragm, the mean EMGdi was above control throughout hypoxia (P less than 0.05). In contrast, as a result of a sustained reduction in duration of the EMGta, the mean EMGta was below control for most of the hypoxic period. In CBD ponies, pulmonary ventilation and mean inspiratory flow rate did not change during chronic hypoxia (P greater than 0.10). In these ponies, the rate of rise of the EMGdi was less than control (P less than 0.05) for most of the hypoxic period, which resulted in the mean EMGdi to also be less than control (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of inspiratory flow rate and volume on digit tip skin and ulnar artery vasoconstrictor responses in healthy adults

2005 ◽  
Vol 69 (1-2) ◽  
pp. 95-100 ◽  
Author(s):  
Einar Wilder-Smith ◽  
Linda Liu ◽  
Khin Thein Ma Ma ◽  
Benjamin K.C. Ong
Keyword(s):  
Flow Rate ◽  
Ulnar Artery ◽  
Inspiratory Flow ◽  
Healthy Adults ◽  
Inspiratory Flow Rate ◽  
Relationship Of

scholarly journals Efficacy of Pressure Support in Compensating for Apparatus Work

1993 ◽  
Vol 21 (1) ◽  
pp. 67-71 ◽  
Author(s):  
A. D. Bersten ◽  
A. J. Rutten ◽  
A. E. Vedig
Keyword(s):  
Endotracheal Tube ◽  
Flow Rate ◽  
Pressure Support ◽  
Work Of Breathing ◽  
Inspiratory Flow ◽  
Inspiratory Flow Rate ◽  
Respiratory Muscle Fatigue ◽  
Tube Size ◽  
Endotracheal Tubes ◽  
Endotracheal Tube Size

Breathing through an endotracheal tube, connector, and ventilator demand valve imposes an added load on the respiratory muscles. As respiratory muscle fatigue is thought to be a frequent cause of ventilator dependence, we sought to examine the efficacy of five different ventilators in reducing this imposed work through the application of pressure support ventilation. Using a model of spontaneous breathing, we examined the apparatus work imposed by the Servo 900-C, Puritan Bennett 7200a, Engstrom Erica, Drager EV-A or Hamilton Veolar ventilators, a size 7.0 and 8.0 mm endotracheal tube, and inspiratory flow rates of 40 and 60 l/min. Pressure support of 0, 5, 10, 15, 20 and 30 cm H2O was tested at each experimental condition. Apparatus work was greater with increased inspiratory flow rate and decreased endotracheal tube size, and was lowest for the Servo 900-C and Puritan Bennett 7200a ventilators. Apparatus work fell in a curvilinear fashion when pressure support was applied, with no major difference noted between the five ventilators tested. At an inspiratory flow rate of 40 l/min, a pressure support of 5 and 8 cm H2O compensated for apparatus work through size 8.0 and 7.0 endotracheal tubes and the Servo 900-C and Puritan Bennett 7200a ventilators. However, the maximum negative pressure was greater for the Servo 900-C. The added work of breathing through endotracheal tubes and ventilator demand valves may be compensated for by the application of pressure support. The level of pressure support required depends on inspiratory flow rate, endotracheal tube size, and type of ventilator.

Renal Function in Unanaesthetized River Lampreys (Lampetra FluviatilisL.): Effects of Anaesthesia, Temperature and Environmental Salinity

1983 ◽  
Vol 105 (1) ◽  
pp. 351-362 ◽  
Author(s):  
A. J. MCVICAR ◽  
J. C. RANKIN
Keyword(s):  
Renal Function ◽  
Flow Rate ◽  
Ventilation Rate ◽  
Urine Flow ◽  
The Body ◽  
Urine Flow Rate ◽  
Flow Rates ◽  
Gill Ventilation ◽  
Daily Excretion ◽  
The Mean

1. Improved estimates of urine flow rates of lampreys in various salinities were obtained by the collection of urine for periods of up to 48 h from minimally-stressed, unanaesthetized fish, following catheterization of the urinogenital papilla. 2. The mean urine flow rate of freshwater lampreys was 200.7 ±14.3 ml kg−1 day−1. 3. Urine flow in freshwater lampreys was correlated with spontaneous changes in gill ventilation rate. MS222 anaesthesia reduced both ventilation and urine flow rates, but pronounced effects were only observed at concentrations greater than those needed to induce light anaesthesia (50–55 mg 1−1). Urine flow rate in unanaesthetized fish was extremely sensitive to rapid (6°Ch−1) changes in temperature and Q10 (6–16°C) was approximately 5. 4. Urine flow rate decreased rapidly as the osmotic difference between the body fluids and environment approached zero, and the rate of flow in 30% seawater lampreys was only 7.6% that of freshwater fish. 5. There was no evidence for an effect of environmental calcium concentration on branchial osmotic permeability. 6. Extensive tubular reabsorption of ions occurred in freshwater lampreys. The total daily excretion rate of sodium ions generally decreased in salinities hyperosmotic to the plasma, indicating enhanced reabsorption, but secretion of magnesium and sulphate ions was greatly increased. Urine osmolarity was significantly increased in lampreys in hyperosmotic salinities. 7. Present data compare favourably with data obtained previously from anaesthetized animals, indicating that renal function in lampreys is not significantly impaired by light MS222 anaesthesia.

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