Part Of Expiration Research Articles

Analysis of pressure-time and flow-time curve in ventilator

To better understand the significance of the pressure-time curve and flow-time curve from the perspective of PB840 ventilator working principle. (1) Mechanical principle: flow supply valves (air valve and oxygen valve) and exhalation valve in PB840 ventilator were controlled to achieve the ventilation target (volume or pressure) by the central processing unit according to the monitoring data from pressure sensors (P1 at the supply side, P2 at the exhalation side) and flow sensors (Q1 at the air side, Q2 at the oxygen side, Q3 at the exhalation side). (2) The essence of curve: each point means a value of pressure or flow at a certain time measured by the sensors or calculated by the system. (3) The respiratory process could be divided into inspiratory part, expiratory part, and the connection part from expiratory to inspiratory. The air running state and the respiratory mechanics relationship at the three parts could be inferred according to the form of curves. (1) Inspiratory process: at volume-controlled and constant flow ventilation: there should be a relationship "Pc-Pa = XR" between alveolar pressure (Pa) and circuit pressure (Pc) according to Ohm law. So, the Pc curve (pressure-time curve) could indirectly reflect the Pa curve with the flow (X) and resistance (R) being constant. At pressure-set ventilation: it is the goal of ventilator to maintain the Pc at the target level. So, the stability of the target pressure line in pressure-time curve reflects the matching ability of the flow supply valves and the exhalation valve. (2) Expiratory process: it could be divided into pre-expiratory [without basic flow (Ba) or bias flow (Bi)] and post-expiratory (with Ba or Bi), where Ba or Bi is equal to "Q1+Q2". So, the mathematical function are "X(t) = Q3t" in pre-part, and "X(t) = Q3t-(Q1t+Q2t)" in post-part. The relationship between pressure and flow at peak expiratory flow point: it could be found that there is an obvious time span and area formation under the curve from 0 to peak point (Fpeak) after stretching the abscissa axis of flow-time curve. It means that some gas have been discharged from the lung when it arrives at the peak point. So, the alveolar pressure should be lower than the platform pressure at the point (Pplat). The circuit pressure is significantly higher than positive end expiratory pressure (PEEP) at the point in the stretching axis diagram. So, it means that the formula "RE = (Pplat-PEEP)/Fpeak" to calculate the expiratory resistance (E) is unreasonable in the angle of Ohm law. (3) The process from exhalation to inspiratory: according to the difference of the starting point of the conversion, it could be divided into two cases: one is that the inspiratory started from the ending of exhalation. Here, the inhaling starting point is lying in the abscissa axis. The other is that the inspiratory started before the ending of exhalation (with endogenous positive end expiratory pressure). Here, the starting point is lying below the abscissa axis, and the slope of the following curve is obviously larger than the slope of natural expiratory curve. According to the difference of results from the starting point to the end of the inhalation triggering effort, it could be divided into two cases: one is that it reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis until an effective air supply is triggered. The other is that it could not reach the trigger point. Here, the expiratory curve extends upward from or below the horizontal axis, but then runs downward (meaning exhaling). It is helpful to analyze the ventilation state, ventilation failure, and the causes of man-machine confrontation with understanding the ventilation principle and the air route map of the ventilator.

Bifurcation of the respiratory response to lung inflation in anesthetized dogs

Numerous studies have demonstrated the effect of lung volume on prolongation of duration of expiration (TE) with limited understanding of the TE shortening and termination of expiration as observed in newborn. In 14 dogs, the effects of varied onset of lung inflation during expiration on the TE were evaluated. When lung inflation was applied in the first part of expiration (20–60% of TE) TE was lengthened. However, in the second portion (60–80% of TE) of expiration, lung inflation either terminated or prolonged TE; whereas in the last portion of expiration (80–90% of TE), lung inflation tended to terminate expiration prematurely. The effects were abolished after bilateral vagotomy. We postulate that prolongation of TE relates to the Breuer-Hering inflation reflex, which increases the time needed for a passive expiration; whereas the ability to shorten TE could relate to Head’s paradoxical reflex acting to initiate inspiration or to activate inspiratory motor activity to brake expiratory flow as occurs in the newborn.

How Respiratory Muscle Training Affects Breathing in Individuals with Spinal Cord Injury

There are an estimated 10,000 to 12,000 spinal cord injuries (SCI) every year in the United States. Besides motor and sensory functional deficits, respiratory insufficiency is also common in individuals with SCI due to paralysis, muscle weakness and/or spastic contractions of the muscles involved in respiration. Pulmonary diseases such as pneumonia and restrictive lung disease are the number one reason for death in individuals with SCI. The aim of the study was to see how respiratory muscle training (RMT) affected the pulmonary function measured with spirometry tests. The outcomes were the forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) and surface electromyography (sEMG). The results showed that both the FVC and FEV1 improved significantly after RMT. Individuals with SCI showed significantly lower sEMG activities recorded from intercostal, diaphragm, rectus abdominis and oblique during expiratory part of spirometry test. The training increased sEMG activity during both inspiration and expiration parts of the test, and this improvement was higher in thoracic SCI compared to cervical SCI.

Prevalence and correlates of a 'knee' pattern on the maximal expiratory flow-volume loop in young adults.

Visual inspection of the maximal flow-volume curve is an important step in interpreting spirometry. Many young people have a convex inflection or 'knee' on the expiratory part of the loop. This is thought to be a normal variant, but this view is based on theoretical grounds, and the epidemiology of the knee pattern has never been reported. Flow-volume loops from an unselected birth cohort of 1037 individuals at ages 18, 26, 32 and 38 years were visually inspected for a knee pattern. Associations with asthma diagnoses, smoking history, body mass index (BMI) and spirometry were assessed. The knee pattern was found in approximately two thirds of men and women at age 18. The prevalence decreased with age, but it was more likely to persist in women. The knee was more common after bronchodilator and was associated with higher forced expiratory volume in 1 s/forced vital capacity ratios and mid-expiratory flow rates. There was no association with smoking, except for an inverse correlation in men at age 18. No association was found with BMI. Women with asthma were less likely to have a knee at both ages 18 and 38, whereas men with asthma showed an inverse association at age 18. A knee is a very common pattern on flow-volume loop in young adults. In accordance with theoretical predictions, the prevalence of the knee declines with age, but it is more likely to persist in women. It is associated with less airflow obstruction and is less common in people with asthma.

MECHANICAL PROPERTIES OF LUNGS IN PATIENTS PROGRESSING MUSCULAR DYSTROPHY VARIOUS SEVERITY OF THE DISEASE

Results of research of biomechanics of breathing at patients with progressing muscular dystrophy (PMD) and their interpretation are unique. Compared indicators of ventilating function of lungs and indicators of mechanics of breathing at 31 patients with PMD to 1–2 extent of motive frustration and 17 patients with 3–4 extent of motive frustration. In both groups of sick MVL and OFV-1 are lowered to the same extent, bronchial resistance isn’t increased. In the 2nd group the reserve volume of an expiratory is reduced for the account decrease in force of respiratory muscles is decreased. Elastic draft of lungs is reduced, the coefficient of functional activity of lungs is increased. At spontaneous breath the tensile properties of lungs are lowered, increased elastic fraction of work of breathing. The general nonelastic resistance of lungs is on the average equally increased in both groups at the expense of increase of tissue friction. At 12 sick PMD the abnormal respiratory loop came to light: completely I was absent at 8 patients and at 4 there was no inspiratory or expiratory part of a loop. Changes of indicators of mechanics of breath are the in generally functionally, and are considered as manifestation of compensatory strengthening of function of an intra pulmonary source of mechanical energy.

Antiasthmatic versus Surgical Treatment—How Important Is the Precise Analysis of Spirometry?

Objective. Carcinoids are low-grade, slow growing malignant tumors in the bronchi usually producing symptoms secondary to bronchial obstruction. We describe a case of 25-year-old woman who was initially diagnosed with asthma. Method. Case report. Results. Because of exacerbation and unresponsiveness to proper asthma treatment she was referred to spirometry, which showed low values of forced expiratory volume in 1 second. The shape of inspiratory limb of flow volume curve suggested an obstruction in the main bronchus or in the trachea. Further bronchoscopy revealed a tumor of the right main bronchus with characteristic histological features for carcinoid. Conclusions. Both the inspiratory curve and the expiratory part of the flow-volume loop should be evaluated in patients being evaluated for asthma. If there are changes in the shape of the inspiratory limb suggesting an obstruction, CT and/or bronchoscopy should be considered.

Simulation of Lung Function Evolution After Heart-Lung Transplantation Using a Numerical Model

A morphometry-based computational model for expiratory flow in humans was used to study the unusual configuration of the maximum expiratory flow-volume (MEFV) curve associated with alterations in lung function after heart-lung transplantation (HLT). The postoperative MEFV curve showed a peak, followed by a gently sloping plateau over the midvolume range, ending in a knee where the flow suddenly fell, instead of the usual observed uniform decrease in expiratory flow. We have tested several hypotheses about the relationship between the pattern of changes in the configuration of the MEFV curve and pathological changes in the airway mechanics through computer simulations. Principally, effects of lung denervation and airway obstruction, associated with the development of bronchiolitis obliterans in the lung periphery, have been investigated. The calculated curves are similar in appearance to the measured postoperative flow-volume curves and confirm reliability of the earlier hypotheses. We conclude that the plateau-knee configuration of the MEFV curve can result from flow limitation in one of the first airway generations, that this flow limitation coupled with an increase in peripheral airway resistance results in plateau shortening, and that flows exceeding predicted values during the second part of expiration may be produced by lung denervation. Additionally our results demonstrate that airways larger than the transitional and respiratory bronchioles can be involved in pulmonary function deterioration observed in patients affected with obliterative bronchiolitis. Our findings indicate that the computational model, based on a symmetrical dichotomous branching structure of the bronchial tree, along with pathological data, can be employed to evaluate the effects of heterogeneous changes in the lung periphery. Index Terms-Airway mechanics, forced expiration, lung transplantation, mathematical modeling, maximal expiratory flow-volume curve.

Three cases of breathing system malfunction

Three cases of breathing system malfunction

Three cases of breathing system malfunction

Three cases of breathing system malfunction

Repeatability of Inspiratory Capacity During Incremental Exercise in Patients With Severe COPD

Estimating lung volume using inspiratory capacity (IC) maneuvers is a useful way of tracking dynamic hyperinflation. An understanding of the repeatability of the IC in a clinical setting is important when evaluating an individual's response to a therapeutic intervention that might influence lung volume. This is the first study to determine the repeatability of serial IC measurements of patients with severe COPD undergoing incremental exercise testing in a clinical setting. Ten patients with severe COPD, inexperienced in exercise testing, cycled with power increased until they reached symptom limitation. Flow was measured at the mouth using a pneumotachograph. IC maneuvers were performed at 1-min to 3-min intervals. Subjects repeated the exercise test 2 days later. Three methods of calculating IC from flow have been described previously. To determine which method provided the best repeatability, we calculated the following: (1) IC calculated by the integration of inspired flow from the start to the end of the IC maneuver (ICINSP); (2) IC calculated from the difference between the drift-corrected peak inspiratory volume (total lung capacity [TLC]) and the drift-corrected end-expiratory lung volume (EELV) of the six breaths that preceded the IC prompt (ICREG); and (3) IC calculated, after correction of the expiratory part of the signal, as the difference between the mean EELV of the six breaths that preceded the IC prompt and the peak inspiratory volume (ICRATIO). Each individual's IC response was expressed as a function of exercise time and of ventilation. There was a significant (p < 0.05) decrease in the expired volume of the breath before the IC maneuver (0.11 +/- 0.26 L) [mean +/- SD]. ICINSP (1.78 +/- 0.88 L) was significantly less than the IC calculated using the other two methods (ICREG, 1.88 +/- 0.89 L; ICRATIO, 1.86 +/- 0.87 L). ICRATIO improved the repeatability of the serial IC measures by as much as 60% over ICINSP and ICREG. Calculating IC as the difference between EELV and TLC was unaffected by unsatisfactory technique, such as a change in breathing pattern immediately before the maneuver. Adjusting expiratory flow based on premaneuver inspiratory to expiratory volume ratio before estimating EELV improved the repeatability coefficient of the IC.

The pressure at the lower inflexion point has no relation to airway collapse in surfactant-treated premature lambs.

The lower inflexion point (LIP) on the inspiratory part of the pressure-volume (PV) loop has been suggested to be related to the pressure at which air spaces collapse. Our hypothesis is that airway collapse might instead be assessed from the upper inflexion point on the expiratory part of the PV-loop (UIPexp), where lung volume starts to decrease significantly. We therefore examined whether there was a relation between LIP and UIPexp in premature surfactant-treated lambs. Ten lambs, at 119-141 days of gestational age, were delivered by cesarean section and given 200 mg/kg modified natural porcine surfactant before the first breath. The lambs were then connected to a ventilator and PV-loops using airway pressures of 0-35-0 (ZEEP-loop) and 5-35-5 cmH2O (PEEP-loop) were obtained after lung recruitment at 15, 60 and 120 min after birth. From the loops, LIP, UIPexp, upper inflexion point of the inspiratory part of the loop (UIP insp), inspiratory capacity (IC) as well as inspiratory and expiratory maximal compliance of the respiratory system (Crs(insp) and Crs(exp)) were calculated. The ZEEP-loop showed a substantial hysteresis with a distinct LIP at 19+/-2 cmH2O (mean+/-SD), which was different (P<0.001) from UIPexp (9+/-2 cmH2O). The pressures at LIP and UIPexp were unrelated (r2=0.06). UIPinsp was located at 28+/-2 cmH2O. Crs(insp) was 2.1+/-0.6 ml x cmH2O(-1) x kg(-1), which was lower (P<0.001) than Crs(exp) (2.8+/-0.6 ml x cmH2O(-1) x kg(-1)). IC was 26+/-6 ml/kg. The PEEP-loop had a minimal hysteresis with an expiratory part coinciding with that of the ZEEP-loop. In surfactant-treated premature lambs the pressures at LIP and UIPexp are not related, showing that LIP does not indicate the pressure at which airways collapse.

Frequency and Correlates of the Saw-Tooth Pattern of Flow-Volume Curves in an Epidemiological Survey

The object of this report was to assess the possibility of identifying saw-tooth patterns on flow-volume curves in men aged 28 to 58 years. We studied the frequency of these patterns and their relationships with two indirect signs of UAO increase in FEV1/PEF and FEF50%/FIF50% ratios--as well as with clinical and functional data. Twenty-six of the 360 subjects surveyed, ie, 7.2 percent, had flow oscillations in the inspiratory and/or expiratory part of flow-volume curves, corresponding to the definition of the saw-tooth pattern. We observed significant relationships between the saw-tooth pattern and the mean FEV1/PEF ratio. In 97 subjects, the proportion of those with saw-tooth patterns was 13.4 percent, and the mean FEF50%/FIF50% ratio was 1.53 in those with the pattern vs 1.07 in those without it. These results show that the saw-tooth pattern was not rare in these men.

Expiratory flushing of airways: a method to reduce deadspace ventilation

A jet of fresh gas entering the trachea during the last part of expiration, expiratory flushing of airways (EFA), may during mechanical ventilation bring the fresh gas interface into the trachea to reduce deadspace. EFA, delivered in a variety of modes, was tested in healthy dogs. EFA allowed tidal volume, peak and mean airway pressure to be reduced by about 25%. EFA was administered in the form of pulses with frequencies 2-8 Hz, and as a continuous flow. The mode was of little importance. EFA was found to be efficient and should be clinically tested.

Breathing strategy of the adult horse (Equus caballus) at rest.

To investigate the mechanism underlying the polyphasic airflow pattern of the equine species, we recorded airflow, tidal volum, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during quiet breathing in nine adult horses standing at rest. In addition, esophageal, abdominal, and transdiaphragmatic pressures were simultaneously recorded using balloon-tipped catheters. Analysis of tidal flow-volume loops showed that, unlike humans, the horse at rest breathes around, rather than from, the relaxed volume of the respiratory system (Vrx). Analysis of the pattern of electromyographic activities and changes in generated pressures during the breathing cycle indicate that the first part of expiration is passive, as in humans, with deflation toward Vrx, but subsequent abdominal activity is responsible for a second phase of expiration: active deflation to below Vrx. From this end-expiratory volume, passive inflation occurs toward Vrx, followed by a second phase of inspiration: active inflation to above Vrx, brought about by inspiratory muscle contraction. Under these conditions the abdominal muscles appear to share the principal pumping duties with the diaphragm. Adoption of this breathing strategy by the horse may relate to its peculiar thoracoabdominal anatomic arrangement and to its very low passive chest wall compliance. We conclude that there is a passive and active phase to both inspiration and expiration due to the coordinated action of the respiratory pump muscles responsible for the resting adult horse's biphasic inspiratory and expiratory airflow pattern. This unique breathing pattern perhaps represents a strategy of minimizing the high elastic work of breathing in this species, at least at resting breathing frequencies.

Factors affecting expired waveform for carbon monoxide.

We previously presented a method based on a computer lung model for determining the distribution of both specific ventilation and specific diffusing capacity. These argon and carbon monoxide (CO) washin and washout studies were obtained in 12 normal subjects and 24 patients with varying degrees of obstructive lung disease. In addition to end-tidal and mixed expired gas concentrations, the expired waveform for both gases was sampled. In patients we found that this method failed to adequately describe CO dynamics during the early part of expiration; predicted concentrations were higher than actual data. Modifications of the original model that satisfy all data are presented. This new model suggests that CO uptake occurs in spaces with ventilatory properties of dead space. The accuracy and reliability of these observations were established by computer simulation studies as well as by repeated testing in one subject. These proved to be highly reproducible over a period of 5 mo. Standard parameter sensitivity tests showed parameters to vary by less than 10% and to be stable even when realistic levels of noise were added to the data. We conclude that studies involving ventilation of insoluble gases are insufficient to describe gas exchange in the lung. The addition of an exchangeable gas adds significant understanding of lung function, particularly in disease.

Pressure available for expiration in chronic airway obstruction.

The pressure generated at 0.1 s after the onset of expiration measures the rate of rise of expiratory pressure potentially available for expiration. P0.1e increased with increasing the frequency of breathing and was higher in chronic obstructive pulmonary disease (COPD) patients than in controls. In normal subjects breathing under resistive load P0.1e became similar to that of patients for a given respiratory frequency. P0.1e consistently increased as the load and/or the frequency of breathing were raised. Expiratory pressure depends on elastic recoil of the respiratory system, nevertheless the action of neurally controlled respiratory muscles influence the rate of rise of expiratory pressure. The decrease of expiratory braking action by inspiratory muscles (-Pmusi) influence the rate of pressure rise in the first part of expiration, whereas the contraction of abdominal muscles (-Pmuse) increases P0.1e later from onset of expiratory occlusion. These compensatory reflexes are vagally mediated and are presumed to originate in stretch receptors. In COPD patients the braking action of inspiratory muscles was smaller and the facilitating action of abdominal muscles was higher than in controls. Both expiratory braking decay and expiratory activity increase with the rise of breathing frequency or with the increase of respiratory airflow resistance.

Exposure to butyl alcohol: uptake and distribution in man.

Twelve subjects were exposed to 300 or 600 mg/m3 of butyl alcohol in inspired air during rest and during exercise on a bicycle ergometer. Exposure lasted 2 h. The results were puzzling in view of the high blood/air partition coefficient for butyl alcohol. The arterial blood concentration was low. The concentration in the last part of the expired air, i.e., the ""alveolar'' concentration, was low. The quotient of ""alveolar'' concentration X 100/inspired concentration was low in relation to the low percentage uptake. However the high solubility of butyl alcohol in water may explain the results. Butyl alcohol was probably partially taken up in the water of the dead space mucous membranes during inspiration. It was then partially released from the membranes. Therefore the concentration of butyl alcohol in the last part of expiration was probably not the same as the concentration in the alveolar air.

The respiratory deposition of polystyrene aerosols in man

The respiratory tract deposition of nonhygroscopic polystyrene monodisperse aerosols is examined in human subjects. Three kinds of polystyrene particles, diameters of 0.188μ, 0.557μ, and 1.305μ (S.D.: 0.0076μ, 0.0108μ, 0.0158μ respectively) produced by Dow Chemical Co. are used to make monodisperse aerosols for inhalation. The aerosols are generated from the particles suspended in water by a nebulizer (Vaponefrin) under a pressure of 20p.s.i. and are stocked in a 9 litter Benedict-Roth type spirometer to dry and to be inhaled. Subjects are 7 healthy males and 1 healthy female (22∼29 years of age) and they are asked to breathe the aerosols in sitting posture by the nose at respiratory rates of 10, 15 and 20 per minute through a rubber mask connected to the spirometer which depicted tidal volume and respiratory flow rate simultaneously. One experiment durates 1∼2 minutes and 60 series of the experiments are performed in all. The aerosol concentration is measured by Kimoto light scatter photometer (Sinclair-Phoenix type) placed between the spirometer and the mask. The aerosol concentration depicted on the recorder of photometer during one respiration consists of 2 parts, an ascending inspiratory part and a descending expiratory part. From each part average concentrations are estimated and deposition rate are calculated for one cycle respiration. Though there are ca. 15 respiration cycle in one experiment, first 3 of them being excluded to avoid the influence of residual volume, 10 cycles are taken to get an average deposition rate for one experiment. The deposition rate is examined in relation to respiratory rate, tidal volume and respiratory flow rate.Aerosol depositions in the respiratory tract vary subject to subject, however, the larger the particle size, the higher the percent of deposition. The aerosols of diameters 0.188μ and 0.557μ showed considerably same and low deposition rates in all the respiratory rates used, which suggests the minimum deposition size will exist in the vicinity of these sizes.The respiratory rate is the next largest variable affecting deposition, that is, the less the respiratory rate the more the deposition, which is most eminently seen in 1.305μ particles. The tidal volume and the flow rate have no relation to the deposition rate.

Motor innervation and pattern of activity of cat diaphragm.

The segmental motor innervation of the costal and vertebral parts of the diaphragm of the cat has been studied by means of electromyography. The changes in electrical activity following successive sections of the cervical roots show that the costal region is innervated partly by C4 but mainly by C5, while the vertebral part is innervated partly by C5 and mainly by C6. After unilateral section of C4, C5, and C6 no diaphragmatic electrical activity remained on the ipsilateral hemidiaphragm. Section of the right phrenic nerve in the chest eliminates all electrical activity in the ipsilateral hemidiaphragm. Following a similar section of the left phrenic nerve, some rhythmic electrical discharge is still recorded from the corresponding hemidiaphragm. Only after section of the contralateral phrenic nerve does this residual activity disappear. Therefore, a few fibers must leave the left phrenic nerve and reach the diaphragm with the right phrenic nerve. Apparently these fibers cross the midline within the diaphragm and contribute to the motor supply of its left side. The pattern of the electrical activity of the costal and vertebral parts of the diaphragm is similar. Generally, no activity is present during the last part of expiration. Submitted on July 9, 1962