Pulmonary function tests in standing ponies: reproducibility and effect of vagal blockade.
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Arterial blood gas tensions, pulmonary mechanics, and lung volumes were measured in 4 sedated ponies every hour for 6 hours and in 5 ponies 4 times at 2-month intervals to assess the short- and long-term reproducibility of pulmonary function measurements. Variability in blood gas tensions was small over the short- and long-term measurement periods, whereas the variability in total respiratory resistance and functional residual capacity was small over the short term but larger over the long term. The variability in tidal volume, minute ventilation, respiratory rate, and dynamic and quasistatic compliance was relatively large over the short and long term. When data from 5 ponies were pooled, significant change did not occur in any of the variables over a 6-month period. Vagal blockade increased tidal volume and decreased respiratory rate and total respiratory resistance, but arterial blood gas tensions, minute ventilation, dynamic compliance, quasistatic compliance, functional residual capacity, and lung and thoracic cage pressure-volume curves were unaffected. Total respiratory resistance decreased with increasing lung volume, with the vagus intact. After vagal blockade, the decrease in total respiratory resistance with lung volume was minimal. Dynamic compliance was frequency independent over a range of 15 to 60 breaths/min-1, suggesting that measurable inhomogeneity of peripheral time constants did not exist in our clinically normal ponies.Keywords:
Pulmonary compliance
Respiratory minute volume
Respiratory physiology
Respiratory Rate
Arterial blood
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Abstract To learn if increasing inspiratory time would improve pulmonary function in mechanically ventilated babies with chronic lung disease, we measured lung mechanics and alveolar ventilation at three inspiratory times: 0.4, 0.6, and 0.8 s. Nine babies were studied. Their mean birth weight was 875 g (range, 570–1,100 g), gestational age 27 (24–34) weeks, and age 7 (4–12) weeks. Their mean oxygen requirement was 40% (29–53), ventilator rate 33/min (20–40), and mean airway pressure 8 (5–10) cmH 2 O. Ventilator rate was kept constant; therefore expiratory time decreased and mean airway pressure and I:E ratio increased at longer inspiratory times. At 0.6 s and 0.8 s, when compared to 0.4 s, significant increases occurred in tidal volume (10.4, 10.1, and 8.4 mL/kg, respectively), dynamic lung compliance (0.68, 0.68, and 0.53 mL/cmH 2 O/kg, respectively), and alveolar ventilation (6.0, 6.3, and 4.7 mL/kg/breath, respectively). Airway resistance, anatomical dead space to tidal volume ratio, and functional residual capacity were similar at the three inspiratory times. Our findings suggest that an inspiratory time ⩾0.6 s (compared to 0.4 s) increases the effectiveness of mechanical ventilation for babies with chronic lung disease.
Mean airway pressure
Peak inspiratory pressure
Pulmonary compliance
Artificial ventilation
Respiratory minute volume
Respiratory physiology
Bronchopulmonary Dysplasia
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We investigated the effects of prone position on functional residual capacity (FRC), the mechanical properties (compliance and resistance) of the total respiratory system, lung and chest wall, and the gas exchange in 10 anesthetized and paralyzed obese (body mass index more than 30 kg/m2) patients, undergoing elective surgery.We used the esophageal balloon technique together with rapid airway occlusions during constant inspiratory flow to partition the mechanics of the respiratory system into its pulmonary and chest wall components. FRC was measured by the helium dilution technique. Measurements were taken in the supine position and after 15-30 min of prone position maintaining the same respiratory pattern (tidal volume 12 mL/kg ideal body weight, respiratory rate 14 breaths/min, fraction of inspired oxygen [FIO2] 0.4). We found that FRC and lung compliance significantly (P < 0.01) increased from the supine to prone position (0.894 +/- 0.327 L vs 1.980 +/- 0.856 L and 91.4 +/- 55.2 mL/cm H2 O vs 109.6 +/- 52.4 mL/cm H2 O, respectively). On the contrary, the prone position reduced chest wall compliance (199.5 +/- 58.7 mL/cm H2 O vs 160.5 +/- 45.4 mL/cm H2 O, P < 0.01), thus total respiratory system compliance did not change. Resistance of the total respiratory system, lung, and chest wall were not modified on turning the patients prone. The increase in FRC and lung compliance was paralleled by a significant (P < 0.01) improvement of PaO2 from supine to prone position (130 +/- 31 vs 181 +/- 28 mm Hg, P < 0.01), while PaCO2 was unchanged. We conclude that, in anesthetized and paralyzed obese subjects, the prone position improves pulmonary function, increasing FRC, lung compliance, and oxygenation. (Anesth Analg 1996;83:578-83)
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Prone position
Pulmonary compliance
Respiratory physiology
Respiratory minute volume
Respiratory Rate
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The purpose of this study was to demonstrate that ventilation of rabbit lungs (whose mechanics are similar to those of human infants) at rapid rates will lead to large alterations in tracheal airway pressures, tidal volume, and functional residual capacity (FRC) with only minor changes in arterial blood gases. Thirteen rabbits were ventilated at rates of 30, 60, 90, and 120 breaths per minutes (BPM) with pressures of 17/2 cm H2O. Tracheal peak inspiratory pressure (PIP) was always lower than ventilator PIP and decreased to 11 ± 1 cm H2O at 120 BPM. Positive end-expiratory pressure (PEEP) in the trachea was always greater than 2 cm H2O and increased with rate (3.5 cm H2O at 120 BPM). Tidal volume decreased as rates were increased such that rates above 60 BPM resulted in insignificant changes in minute ventilation and arterial blood gases. However, the FRC increased from 16 (30 BPM) to 25 ml/kg (120 BPM), a 56% increase, suggesting large increases in end-expiratory alveolar pressure. We conclude that rapid-rate ventilation (> 60 BPM) of healthy rabbits results in significant increases in both tracheal PEEP and FRC without significantly affecting arterial blood gases. The increased tracheal PEEP and FRC are manifestations of inadvertent PEEP. The increased FRC without concomitant increase in PaO2 implicates alveolar overdistention. We speculate that rapid-rate ventilation of human infants having lung mechanics similar to rabbits, will also result in inadvertent PEEP and alveolar overdistention.
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Objective To study the development of pulmonary function of healthy children between 1-48 months. Methods A total of 295 healthy children at ages of 1-48 months were classified into 7 groups according to their age, i.e., 1-2 months, 3-4 months, 5-7 months, 8-12 months, 13-24 months, 25-36 months, and 37- 48 months. Pediatric pulmonary function laboratory type 2600 (Sensor Medics Corporation USA) was used to detect tidal flow volume curve, which can partially replace the maximum expiratory flow volume curve and reflect airway ventilation function. Passive expiratory flow volume technique was used to examine respiratory system static compliance and total airway resistance. Open nitrogen washout method was used to measure functional residual capacity. Results The values of tidal, peak tidal expiratory flow, and respiratory system static compliance functional residual capacity increased with the increasing age and were significantly different among the 7 groups. However, respiratory rate and total airway resistance decreased with the increased age. The value of each parameter of tidal flow volume curve was stable during 1-48 months. Conclusions This study displayed the developmental characteristics of pulmonary function of healthy children at ages of 1-48 months, which is useful to observe the changes of pulmonary function in respiratory diseases.
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Abstract The known effects of drugs from a variety of pharmacologic/therapeutic classes on the respiratory system and worldwide regulatory requirements support the need for conducting respiratory evaluations in safety pharmacology. The objective of these studies is to evaluate the potential for drugs to cause secondary pharmacologic or toxicologic effects that influence respiratory function. Changes in respiratory function can result either from alterations in the pumping apparatus that controls the pattern of pulmonary ventilation or from changes in the mechanical properties of the lung that determine the transpulmonary pressures (work) required for lung inflation and deflation. Defects in the pumping apparatus are classified as hypo‐ or hyperventilation syndromes and are evaluated by examining ventilatory parameters in a conscious animal model. The ventilatory parameters include respiratory rate, tidal volume, minute volume, peak (or mean) inspiratory flow, peak (or mean) expiratory flow, and fractional inspiratory time. Defects in mechanical properties of the lung are classified as obstructive or restrictive disorders and can be evaluated in animal models by performing flow‐volume and pressure‐volume maneuvers, respectively. The parameters used to detect airway obstruction include peak expiratory flow, forced expiratory flow at 25 and 75% of forced vital capacity, and a timed forced expiratory volume, while the parameters used to detect lung restriction include total lung capacity, inspiratory capacity, functional residual capacity, and compliance. Measurement of dynamic lung resistance and compliance, obtained continuously during tidal breathing, is an alternative method for evaluating obstructive and restrictive disorders, respectively, and is used when the response to drug treatment is expected to be immediate (within minutes post‐dose). The species used in the safety pharmacology studies conducted in our laboratory are the same as those used in toxicology studies since pharmacokinetic and toxicologic/pathologic data are available in these species. These data can be used to help select test measurement intervals and doses and to aid in the interpretation of functional change. The techniques and procedures for measuring respiratory function parameters are well established in guinea pigs, rats, and dogs.
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Pulmonary compliance
Respiratory minute volume
Respiratory physiology
Respiratory Rate
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Summary 1. Respiratory volume changes and intra‐esophageal pressure changes have been simultaneously recorded beginning before or during the first breaths in 18 infants. 2. Respiratory adaptive changes for successful extra‐uterine existence occur rapidly. Some of the features are summarized below. 3. The average air exchange in the first 20 seconds after the first breaths is 2–3 times the resting minute volume observed later in the neonatal period. 4. A residual volume is established in some infants beginning with the first breath. In others this was not recorded and evidence is presented which suggests it may occur prior to the first breath. 5. The total pressure change of the first breath ranged from 40–100 cm O. In succeeding breaths this decreased. Typical pressure‐volume diagrams (“respiratory loops”) are illustrated and their possible significance discussed. 6. During the first few breaths the lung compliance was one‐fifth to one‐third and the pulmonary flow resistance 24 times that found in older neonates.
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Arterial blood gas tensions, pulmonary mechanics, and lung volumes were measured in 4 sedated ponies every hour for 6 hours and in 5 ponies 4 times at 2-month intervals to assess the short- and long-term reproducibility of pulmonary function measurements. Variability in blood gas tensions was small over the short- and long-term measurement periods, whereas the variability in total respiratory resistance and functional residual capacity was small over the short term but larger over the long term. The variability in tidal volume, minute ventilation, respiratory rate, and dynamic and quasistatic compliance was relatively large over the short and long term. When data from 5 ponies were pooled, significant change did not occur in any of the variables over a 6-month period. Vagal blockade increased tidal volume and decreased respiratory rate and total respiratory resistance, but arterial blood gas tensions, minute ventilation, dynamic compliance, quasistatic compliance, functional residual capacity, and lung and thoracic cage pressure-volume curves were unaffected. Total respiratory resistance decreased with increasing lung volume, with the vagus intact. After vagal blockade, the decrease in total respiratory resistance with lung volume was minimal. Dynamic compliance was frequency independent over a range of 15 to 60 breaths/min-1, suggesting that measurable inhomogeneity of peripheral time constants did not exist in our clinically normal ponies.
Pulmonary compliance
Respiratory minute volume
Respiratory physiology
Respiratory Rate
Arterial blood
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The obese Zucker rat, an autosomally genetic model of obesity, represents a good model of relatively early onset human obesity. Although factors associated with the control of metabolism and thermoregulation have been studied extensively in these animals, pulmonary mechanics and ventilation have not been documented and form the basis of this investigation. Studies were carried out in 16 obese and 18 lean female littermates (698 +/- 79 versus 304 +/- 24 g, p < 0.001). Pulmonary function, including lung volumes and respiratory system compliance, was evaluated in supine anesthetized animals. With the exception of residual volume, all other lung volumes, including function residual capacity, total lung capacity, expiratory reserve volume, and inspiratory capacity, were significantly reduced (p < 0.05 or better) in the obese phenotype compared with volumes in the lean littermates. Pressure-volume relationships of the intact respiratory system and the excised lung were also determined. Although lung compliance was similar between the phenotypes, respiratory system compliance was significantly lower (0.85 +/- 0.06 versus 0.67 +/- 0.09 ml/cm H2O, p < 0.01) in the obese rats. Oxygen consumption and ventilatory parameters (including respiratory rate, tidal volume, minute ventilation, inspiratory time, and expiratory time) were similar between phenotypes breathing room air, and the minute ventilation in response to hypoxia was similar in both groups. In marked contrast, obese animals exhibited a blunted ventilatory response to hypercapnia (221 +/- 38 versus 135 +/- 44 ml/min, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Supine position
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Work of breathing
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To study the effects of anesthesia on respiratory function of the neonate, the authors investigated the effect of breathing 100% oxygen and of breathing oxygen plus 0.75 MAC halothane on functional residual capacity, lung and airway resistance, expired minute volume, work of breathing, lung compliance, and blood gases and pH in nine 5-8-day-old, 4.6-7.7-kg lambs. Breathing 100% oxygen increased PaO2 but had no effect on PaCO2, minute ventilation, or lung mechanics. Three-fourths MAC halothane depressed minute ventilation 34% +/- 13% (P less than 0.05) and increased PaCO2 50% +/- 5% (P less than 0.05). Lung and airway resistance increased 59% +/- 26% (P less than 0.05); work of breathing decreased (P less than 0.05); and lung compliance was unchanged. Functional residual capacity was reduced 32% +/- 6% (P less than 0.05), which may be due to loss of diaphragm and intercostal muscle function and to an inability to take deep breaths. The authors conclude that 0.75 MAC halothane significantly impairs the pulmonary function of lambs who breathe spontaneously. Similar changes in human infants could account for the hypoxemia and hypercarbia that often are seen during anesthesia.
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Hypercarbia
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