Changes In Thoracic Volume Research Articles

Age-related changes in chest geometry during cardiopulmonary resuscitation.

We studied alterations of chest geometry during conventional cardiopulmonary resuscitation in anesthetized immature swine. Pulsatile force was applied to the sternum in increments to determine the effects of increasing compression on chest geometry and intrathoracic vascular pressures. In 2-wk- and 1-mo-old piglets, permanent changes in chest shape developed due to incomplete recoil of the chest along the anteroposterior axis, and large intrathoracic vascular pressures were generated. In 3-mo-old animals, permanent chest deformity did not develop, and large intrathoracic vascular pressures were not produced. We propose a theoretical model of the chest as an elliptic cylinder. Pulsatile displacement along the minor axis of an ellipse produces a greater decrease in cross-sectional area than displacement of a circular cross section. As thoracic cross section became less circular due to deformity, greater changes in thoracic volume, and hence pressure, were produced. With extreme deformity at high force, pulsatile displacement became limited, diminishing pressure generation. We conclude that changes in chest geometry are important in producing intrathoracic intravascular pressure during conventional cardiopulmonary resuscitation in piglets.

Effect of raised thoracic pressure and volume on 99mTc-DTPA clearance in humans.

Although positive airway pressure is often used to treat acute pulmonary edema, the effects on epithelial solute flux are not well known. We measured independently the effect of 1) positive pressure and 2) voluntary hyperinflation on the clearance of inhaled technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) in six nonsmokers and six smokers. Lung volumes were monitored by inductance plethysmography. Each subject was studied in four situations: 1) low end-expiratory volume (LO-), 2) low volume plus 9 cmH2O continuous positive airway pressure (LO+), 3) high end-expiratory volume (HI-), and 4) high volume plus continuous positive airway pressure (HI+). The clearance half time of 99mTc-DTPA for the nonsmokers decreased from 64.8 +/- 7.0 min (mean +/- SE) at LO- to 23.2 +/- 5.3 min at HI- (P less than 0.05). Positive pressure had no synergistic effect. The mean clearance half time for the smokers was faster than nonsmokers at base line but unaffected by similar changes in thoracic volume and pressure. We conclude that, in nonsmokers, positive airway pressure increases 99mTc-DTPA clearance primarily through an increase in lung volume and that smokers are immune to these effects.

Assessment of Time-Volume and Flow-Volume Components of Forced Vital Capacity: Measurement with Spirometry, Body Plethysmography and Respiratory Inductive Plethysmography in Nonsmokers and Smokers

The purpose of this investigation was to assess the effectiveness of the time-volume and flow-volume components of the forced vital capacity measured by simultaneous spirometry, respiratory inductive plethysmography, and body plethysmography in detecting small airway disease. Spirometry measured the exit of gas from the lungs, whereas body plethysmography measured both the exit of gas and alveolar gas compression. Respiratory inductive plethysmography, which reflected change in thoracic volume, provided semi-quantitative data f both gas exit and alveolar gas compression which generally lay between spirometry and body plethysmography. In nine nonsmokers and 12 smokers (six with small airway disease as defined by abnormal closing volumes and alveolar uniformity), analysis of forced vital capacity revealed that the only test which differentiated nonsmokers from smokers was the higher spirometric estimation of maximum expiratory flow measured at 25 percent VC in nonsmokers. Combining flow measure at the mouth with volume referenced to change in alveolar gas volume as measured by body or respiratory inductive plethysmography did not differentiate nonsmokers from smokers. Moment analysis performed of forced vital capacity with all of the three devices did not distinguish nonsmokers from smokers. The data in this study and a review of other investigations indicate that the time-volume and flow-volume components of the forced vital capacity on air breathing are not very sensitive in detecting early lung disease in smokers.

1703 Onset of respiration after delivery by Caesarean section and the vagina

Our previous work has shown that babies born by C section requiring resuscitation rarely achieve a functional residual capacity (FRC) immediately, unlike those born by vaginal delivery. As these differences could be due either to asphyxia or the mode of delivery, we have measured the first spontaneous breath in 21 babies born vaginally, measuring intrathoracic pressure with a micro pressure transducer on a 6fg catheter, and thoracic volume change on a pneumotachograph, from the time the baby's head was delivered on the perineum until regular respiration had commenced. We compared the results with data obtained on 12 babies born by C section, commencing measurements as soon as the baby's head was delivered through the uterine incision. Those delivered vaginally experienced prolonged squeeze of up to 237cm H2O, compared to a transient pressure of 113cm H2O on passage through the uterine scar. Inspiratory pressures and volumes were similar for the two groups, but only five of those born by C section had an FRC after the first breath, compared to 20 of the 21 vaginal deliveries. Opening pressures were rarely seen in either group. We conclude that passage down the birth canal does aid lung expansion at birth.

Computer determination of thoracic gas volume using plethysmographic "thoracic flow".

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume

A New Method for Measuring Static Compliance in Infants and Young Children

1. A new method for measuring static compliance, which does not require general anaesthesia or a leak-free airway, is described for infants and young children. 2. Thoracic volume changes produced by static inflation pressures are measured by a respiratory jacket, and results compare well with those obtained by the syringe-inflation method. 3. This method can be used in the intensive care of sick infants, where it allows a new approach to the investigation of lung mechanics.

The supply of oxygen to the active flight muscles of some large beetles.

ABSTRACT Measurements of the wing-beat frequency, wing-stroke amplitude and stroke plane and of abdominal ventilation have been made during the tethered flight of twenty-six species of beetles belonging to five families, mainly in Uganda. Abdominal ventilation is weak or absent in all species of Cerambycidae, Elateridae and Anthribidae examined in flight. The tracheal system in these families is characterized by the complete absence of air sacs, and in larger species by the presence of four giant trunks running through the metathorax between spiracles 2 and 3 and forming the primary supply to the flight muscles. Abdominal ventilation is strong during the flight of all species over o·6 g. in weight of the Scarabaeidae and Buprestidae which were examined. Their tracheal systems contain an abundance of air sacs while giant trunks are absent. Measurements of the thoracic volume changes which accompany each wing beat show that the amount of air which can be pumped in this way increases in larger Cerambycidae per second per gram as compared with small species. Large Cerambycidae pump more per gram than Scarabaeidae of comparable size. During the flight of the cerambycid Petrognatha the thoracic pump exchanges 540 μ1. air/sec./g. Its action is mainly on the compressible secondary tracheae. In a wind speed of 5 m./sec. 1050 μ1. air/sec./g. are driven through the four giant trunks, entering through spiracle 2 and leaving from spiracle 3. The trunks are stout-walled and probably unaffected by the thoracic pump.

Fluid volume redistribution and thoracic volume changes during recumbency.

Continuous measurements of change in center of gravity, thoracic and abdominal girths and extremity volume over a 30-minute period of recumbency were recorded in 20 normal young adults. Vital capacity, expiratory reserve volume and residual volumes were recorded at the beginning and end of the period. No significant differences between the initial and final vital capacities or residual volumes were observed. Expiratory reserve volume decreased and correlated positively with the measured change in torque. Abdominal and thoracic end expiratory circumferences both increased. Four young adults, normal except for congenital or traumatic absence of the lower extremities, were examined in the same manner. In these subjects the change in center of gravity was minimal and the thoracic circumference did not increase. The pattern of lung volume changes during recumbency was similar to normal subjects. It is concluded that during recumbency the lower extremities contribute blood to the thoracic pool and this is manifested as an increase in thoracic girth, but without decrease in total lung volume. The diaphragm assumes a more expiratory position and is partially responsible for the change in expiratory reserve volume. Submitted on August 4, 1958