Forced Deflation Research Articles

“Stiction Syndrome”: Non-Operative Management of Patients With Difficult AMS 700 Series Inflation

IntroductionStatic friction (stiction) is a mechanical phenomenon in which a state of increased resistance exists across a control valve mechanism. AimTo present a strategy for non-operative management of inflatable penile prosthesis (IPP) cases with pump malfunction from pump valve stiction. MethodsAll patients had American Medical Systems (AMS; Minnetonka, MN, USA) 700 series Momentary Squeeze IPPs with transient pump malfunction owing to pump valve stiction after extended periods of device inactivity. Main Outcome MeasuresOur evolving non-operative management experience with the “forced deflation” maneuver is described. This technique has successfully prevented the need for surgical pump replacement. Of patients with IPP who were instructed to inflate and deflate daily to prevent stiction recurrence, none have re-presented with difficult inflation. ResultsOf 306 patients receiving the AMS 700 series IPP at our institution from 2007 through 2015, 6 (1.9%) presented with difficulty activating the Momentary Squeeze pump (from 2011 through 2015). Four additional patients were referred from outside institutions with the same complaint. All patients (10 of 10, 100%) presented after a prolonged period of inactivity (minimum = 6 weeks) during which the IPP was not cycled and remained stagnant. Although the initial four patients (40%) underwent surgical exploration with pump mobilization and replacement, the six most recent patients (60%) were successfully instructed in the forced deflation maneuver in the office, which enabled the device to cycle normally thereafter. ConclusionDevice inactivity, for as little as 6 weeks, can predispose to Momentary Squeeze pump valve malfunction; and a regimen of daily IPP cycling could prevent stiction-related malfunction. Our findings should encourage practitioners to attempt conservative management of patients with “stiction syndrome” whenever possible, thereby avoiding unnecessary surgery.Kavoussi NL, Viers BR, VanDyke ME, et al. “Stiction Syndrome”: Non-Operative Management of Patients With Difficult AMS 700 Series Inflation. J Sex Med 2017;14:1079–1083.

Forced deflation pulmonary function test: a novel method to evaluate lung function in infants and young children.

We describe the safety and feasibility of a forced deflation pulmonary function test (dPFT) in infants and young children. Fifty-two dPFT studies were performed in 26 patients (median age, 1.4 years). Forced vital capacity (FVC) and forced expiratory flow (FEF75 ) were normal in all except one case, but respiratory system compliance (Crs) was reduced in 24% patients. There were no significant differences in pre-blood and marrow transplantation FVC, FEF75 , and Crs between those patients who did and those who did not have posttransplant pulmonary complications. A larger study is needed to determine the prevalence and significance of PFT abnormalities in this age group.

Forced Deflation PFT: A Novel Method to Evaluate Lung Function in Infants and Young Children

Pretransplant pulmonary function test (PFT) abnormalities are correlated with risk of early respiratory failure and mortality in adults and older children. While there is an increasing use of allogeneic BMT in infants and young children with metabolic and immune deficiency disorders, lung function has not been systematically studied in this age group. We describe use of forced deflation PFT (dPFT), a novel technique for assessment of lung function in a series of infants and young children and those unable to perform cooperative testing. Forced dPFT studies were coordinated with other procedures requiring general anesthesia and performed according to previously published techniques1. Briefly, a specially constructed forced deflation device was inserted between the endotracheal tube and anesthesia breathing circuit via a 3-way slide valve (Figure). The lungs were inflated three times to 40 cm H2O (total lung capacity) and then rapidly deflated to -40 cmH2O via a pneumotachograph (to residual volume). Raw flow or volume measurements were normalized and converted to %predicted and standard deviation scores using data obtained in healthy children. Between October 2008 and April 2014, 52 dPFT studies were performed in 26 transplant recipients. Indications for BMT were inherited metabolic disease (42%), malignancy (31%), primary immune deficiency (15%) and bone marrow failure (12%). Median age of 21 patients who had pretransplant studies was 0.9±1.3 y (0.1 – 4.9 y); nine of them (43%) had one or more prior lung diseases (respiratory failure [n=7]; pneumonia [n=7]; ARDS [n=3]; bronchopulmonary dysplasia [n=1]; and bronchitis [n=1]). Forced vital capacity (FVC) and forced expiratory flow (FEF75) were normal in all but respiratory system compliance (Crs) was reduced in 5/21 cases. Six out of nine (66.7%) patients with clinical resp. issues pre-BMT also had respiratory complications post-BMT compared with 3/12 (25%) that had no pre-transplant respiratory issues. There were no significant differences in pre-transplant FVC, FEF75 and Crs between those patients who did and who did not have post-transplant pulmonary complications with median follow-up of 1.7±1.5 y (p=0.435, p=0.305, and p=0.301 respectively). There were no complications during the procedures and dPFT studies could be safely done in coordination with other procedures requiring anesthesia. In this pilot study, pre-transplant PFTs were not predictive of post-transplant pulmonary complications, and most patients had normal volume and flows. A larger study would be required to determine prevalence and significance of lung function abnormalities in infants and toddlers undergoing transplantation. 1. Motoyama, E. K., et al. (1987). “Early onset of airway reactivity in premature infants with bronchopulmonary dysplasia.” Am Rev Respir Dis 136(1): 50-57.

Pulmonary function testing in infants with tetralogy of Fallot and absent pulmonary valve syndrome.

Aim:Absent pulmonary valve syndrome (APVS) is found in 3-6% of patients with Tetralogy of Fallot (TOF). Along with findings of TOF, absence of pulmonary valve tissue results in aneurysmal dilatation of the main and branch pulmonary arteries compressing the trachea, main-stem, and intrapulmonary bronchi leading to obstructive airways disease. Our objective was to review pulmonary function tests (PFT) in TOF-APVS patients.Materials and Methods:Eight PFT were performed on five mechanically ventilated TOF-APVS patients in the intensive care unit. Tidal volume, forced vital capacity (FVC), maximal expiratory flow 25%, resistance and compliance of the respiratory system were measured.Results:Pre-operative PFTs showed markedly elevated airways resistance (RRS) (median 0.45 cmH2O/mL/sec, range 0.17-0.66) and marked variability of the static compliance of the respiratory system (CRS) (median 0.6 mL/cmH2O/kg, range 0.25-2.6). Flow-volume loops measured by forced deflation showed flow limitation within the medium to small airways. Post-operative FVC was reduced in four of the five patients (median 46 mL/kg, IQR 42.9 - 48.8 mL/kg). Patients studied with various levels of positive end expiratory pressure (PEEP) showed improvement in tidal volume and reduced obstruction with PEEP greater than 10 cmH2O. For three patients with pre-operative data available, surgical correction resulted in near-normal post-operative CRS and improved, but still elevated RRS (median 0.14 cmH2O/mL/sec, interquartile range [IQR] 0.11-0.31).Conclusion:For our patients with TOF-APVS, airway resistance was elevated. Flow limitation was seen in the medium to small airways with a mild reduction of FVC. PFTs may help guide management of mechanical ventilation for TOF-APVS patients.

Passive aortic counterpulsation: Biomechanical rationale and bench validation

Aortic counterpulsation (IABP) consists in an ECG-controlled forced deflation and inflation of a balloon positioned in the aorta. The device is designed to decrease the ventricular afterload during systole and to increase the coronary driving pressure during diastole. In biomechanical terms, the IABP improves the mechanical matching between the pump and the load, facilitating the transfer of ventricular energy. This paper describes a completely passive aortic counterpulsation solution, with an intra-aortic balloon without a pumping system, designed to improve the mechanical matching between the ventricle and the artery at very low cost and complexity. The only requirement is an external reservoir to amplify the balloon pulsations due to physiologic arterial pressure pulse.Using a cardiovascular simulator and changing the reservoir pressure, a systolic not negligible (7.8ml) gas volume exchange between the intra-aortic balloon and the reservoir was measured. The same cardiovascular simulator was used to demonstrate an increase in stroke volume in three conditions of progressive ventricular failure, by detecting a change in systolic and diastolic arterial pressures and stroke volume (SV). The maximal arterial pressure always decreased and the diastolic pressure increased. The SV increased up to 7.8%, demonstrating an arterial elastance reduction and better ventricular–aortic mechanical matching and energy transfer.

The Effect of Cisatracurium and Rocuronium on Lung Function in Anesthetized Children

Neuromuscular blocking drugs have been implicated in intraoperative bronchoconstrictive episodes. We examined the effects of clinically relevant doses of cisatracurium and rocuronium on the lung mechanics of pediatric subjects. We hypothesized that cisatracurium and rocuronium would have bronchoconstrictive effects. We studied ASA physical status I and II pediatric subjects having elective dental or urological procedures, requiring general anesthesia with endotracheal intubations with either cisatracurium or rocuronium. Pulmonary function tests were performed before and after neuromuscular blocking drug dosing and again after albuterol administration. Using forced deflation and passive deflation techniques, forced vital capacity (FVC) and maximum expiratory flow rate at 10% (MEF10) of FVC were obtained. Fractional changes from the baseline were used to compare subjects. Changes in MEF10 of >30% were considered clinically significant. A Shapiro-Wilk test, paired t test, and Wilcoxon rank sum test were used to analyze the data. Twenty-five subjects (median age = 5.25 years; range = 9 months-9.9 years) were studied; 12 subjects received cisatracurium and 13 subjects received rocuronium. Data are shown as mean proportional change ± SD or, in the case of not normally distributed, median proportional change (first, third quartile) with P values. In the cisatracurium group, there were no differences between baseline and postneuromuscular blocker administration in the fractional change from the baselines of FVC (1.00 ± 0.04, P = 0.5), but there was a significant decrease in MEF10 (0.80 ± 0.18, P = 0.002). In the rocuronium group, there were small yet significant decreases of FVC (0.99 [first quartile 0.97, third quartile 1], P = 0.02) and significant decreases in MEF10 (0.78 ± 0.26, P = 0.008). After administration of albuterol in the cisatracurium group, FVC increased slightly but significantly from baseline values (1.02 ± 0.02, P = 0.005). MEF10 increased significantly beyond baseline values (1.24 ± 0.43, P =0.04). In the rocuronium group, there were also significant differences between baseline and postalbuterol administration from the baseline value of FVC (1.02 ± 0.02, P = 0.004) and MEF10 (1.23 ± 0.29, P = 0.01). At clinically relevant doses, both cisatracurium and rocuronium caused changes in lung function, indicating constriction of smaller airways. In general, these changes were mild and not clinically detectable. However, in the rocuronium group, 3 of 13 patients showed more noticeable decreases in MEF10 (≤50%), demonstrating the potential for significant broncho-bronchiolar constriction in susceptible patients.

Forced expiratory flows and volumes in intubated and paralyzed infants and children: normative data up to 5 years of age

Reference equations that express indexes obtained from forced expiratory maneuvers in relation to height and/or other independent variables are lacking for infants and children with artificial airways. The present study was performed to establish normative data of forced expiration by forced deflation in healthy intubated and paralyzed infants and children and to develop prediction equations in relation to height and to ulna length to enable pulmonary assessments in children whose height is difficult to measure. Measurements of forced and passive expiratory maneuvers after inflation to +40 cmH(2)O inspiratory pressure were prospectively obtained in 100 healthy anesthetized children from 0 to 5 yr of age. Linear regressions of log-transformed forced vital capacity (FVC) and maximum expiratory flow at 25% and 10% FVC (MEF(25) and MEF(10), respectively) obtained by forced deflation (-40 cmH(2)O airway opening pressure) and of analogous indexes obtained by passive deflation were used to develop prediction equations from height or ulna length. FVC was significantly dependent on age and height or ulna length. Prediction equations for FVC using height or ulna length were as follows: ln(FVC in ml) = -5.6 + 2.8 x ln(height in cm) and ln(FVC in ml) = 0.46 + 2.5 x ln(ulna length in cm). Younger subjects had a significantly steeper slope for FVC vs. height than the older age group. Normal reference data for forced expiratory maneuvers in intubated infants and children up to 5 yr of age will enable improved assessment of pulmonary dysfunction in acutely or chronically ventilator-dependent children. Using ulna length instead of height should facilitate respiratory assessment in ventilated children with spinal or joint deformities.

Measurement of Forced Expiratory Flows and Lung Volumes

After completing this article, readers should be able to: 1. Describe the information that measurements of forced expiratory flow can provide in spontaneously breathing and mechanically ventilated infants. 2. Delineate how lung volume can be measured. The measurements of forced expiratory flows and lung volumes are important to the evaluation of patients who have respiratory symptoms. Until recently, measurements have been restricted to adults and children old enough to cooperate with testing maneuvers. Newer techniques have enabled such measurements to be made in infants and led to improved understanding of normal lung and airway growth during infancy and early childhood, when dramatic changes occur. The measurements have had important clinical uses in the evaluation and treatment of infants who have respiratory disease, but their use has been limited because they require specialized equipment and expertise as well as sedation of the infant. In this article, we discuss the techniques required for measurement of forced expiratory flows and lung volumes, their limitations, and applications in clinical practice. Detection of airflow obstruction, by physical examination or by quantitative measurement techniques, is facilitated by increasing expiratory flow rates. Measurement of forced expiratory flows is useful because flow rates are inversely proportional to the fourth power of the radius of the airway and, therefore, are indicative of airway size when flow is limited. Disease states affecting the airways, including asthma, bronchopulmonary dysplasia (BPD), or congenital lesions such as pulmonary hypoplasia or vascular airway compression, are expected to decrease expiratory flow. Infants typically are sedated for testing to maintain relaxed breathing with a face mask placed over the mouth and nose. This sedation often is perceived by parents and physicians as one of the barriers to such testing. (1) However, sedation can be achieved safely using oral chloral hydrate at a dose of 80 to 100 mg/kg. …

Effect of forced deflation maneuvers upon measurements of respiratory mechanics in ventilated infants.

To determine the effect of forced deflation maneuvers on respiratory mechanics and to assess the reproducibility of such measurements in intubated infants with lung disease. Prospective study in the pediatric intensive care unit of a university children's hospital. Ten clinically stable infants requiring mechanically assisted ventilation for acute pulmonary disease, mean age 5.9 months (1-18), mean weight 5.8 kg (3.2-13). Two sets of measurements of compliance (Crs) and resistance (Rrs) were obtained at 20-min intervals both before and after +40/-40 cmH(2)O forced deflation maneuvers. Forced deflation measurements were repeated at the end of the study. . Forced deflation caused a significant increase in Crs from 0.53+/-0.09 and 0.58+/-0.11 ml/cmH(2)O/kg to 0.71+/-0.11 and 0.68+/-0.11 ml/cmH(2)O/kg. Rrs measurements did not differ. The low coefficients of variation for repeated measures of the baseline measurements (Crs 4.2+/-0.5%, Rrs 7.1+/-0.8%, for forced vital capacity 8.6+/-2.5%, maximum expiratory flows at 25% vital capacity 16.0%+/-3.3%) confirmed the good reproducibility during stable conditions. Inflation and deflation maneuvers affect subsequent measurements of respiratory system compliance but not measurements of maximum expiratory flow-volume relationships in intubated infants, probably through recruitment of lung volume. Careful interpretation and planning of the sequence of infant pulmonary function testing is necessary to reassure that changes are not related to short-term alterations in volume history.

Interdependence of flow between lobes reduces maximal emptying postresection in dogs.

The effect of pulmonary resection on the maximal emptying of the remaining lobes was examined in an open-chest preparation in normal canine lungs and in a unilobar papain emphysema model. The objectives were to determine whether, compared with when both lungs were deflated (BL), maximal emptying of the normal lower lobes or the emphysematous right lower lobe would be altered 1) when acute pneumonectomy of the contralateral lung was performed (OL) and 2) when the lower lobe deflated alone (LA). The alveolar capsule technique was used to measure alveolar pressures (Palv) at 75, 50, and 30% lobar vital capacity (VC). During forced deflation, the maximal rates of deflation (dPalv/dt) and flows (lobarV(max)) of the lower lobes were determined under the three different conditions. The Pitot-static tube technique was used to measure intrabronchial pressures and to estimate bronchial area and compliance in which values were obtained at the same central airway during the conditions studied. The results showed that, compared with BL and OL, dPalv/dt and lobar V(max) decreased during LA (P < 0.05). These findings were due to a reduction in bronchial area during LA that limited flow at a lower maximal value compared with BL. This decrease in area appeared to be due to a change in bronchial pressure area behavior that resulted in a smaller bronchial area during LA for similar transmural pressures between conditions. There were no differences in findings between normal and emphysematous lobes. This study suggested that removal of lobes may alter the pressure area behavior of central airways. Possible mechanisms considered were differences in axial tension between conditions, negative effort dependence, or parenchymal-bronchial interdependence that may be relevant to understanding the dynamic collapsibility of central as well as intraparenchymal airways.

Influence of endotracheal tube diameter on forced deflation flow-volume curves in rhesus monkeys.

The forced deflation (FD) technique is the recommended gold standard to generate forced expiratory vital capacity (FVC) curves and to measure maximum expiratory flow-volume (MEFV) relationships in intubated infants and children. However, the influence of the endotracheal tube (ETT) on the site of flow limitation, the shape and the analysis of the resultant MEFV curves have not been defined. Nine anaesthetized (thiopentone, 8 mg x kg(-1) x h(-1)) rhesus monkeys (mean weight (+/-SEM) 10+/-1 kg) were intubated consecutively with ETTs of different internal diameters (ID 3.0-5.5 mm, at intervals of 0.5 mm); the largest representing the appropriate ETT size for the animal. Quadruplicate MEFV curves were generated by FD using the standard +40 cmH2Oinsp/-40 cmH2Oexp pressures and recorded at each ETT diameter. The effect of the different ETT diameters on the FD flow-volume curve was analysed by comparing maximum expiratory flows at isovolume points at 50, 25 and 10% FVC (MEF50, MEF25 and MEF10, respectively). The shape of the resulting MEFV curves could be divided into an initial horizontal part (tube-dependent), and a final descending slope (airway-dependent). No difference in FVC occurred irrespective of the ETT size (p>0.05 by analysis of variance (ANOVA)). MEF50 increased with increasing tube diameter (p<0.05). MEF25 remained unchanged using ETTs which were less than 1.5 mm smaller than the largest ETT. Smaller ETTs resulted in significantly reduced MEF25 (p<0.05). MEF10 was not influenced by the ETT size. We conclude that maximum expiratory flows measured by the forced deflation technique are not influenced by an appropriately sized endotracheal tube at lung volumes below 25% forced vital capacity in our monkey model with normal lungs. We postulate that the effect of endotracheal tubes on maximum expiratory flow volume curves in intubated infants might be of similar or even smaller magnitude, which remains to be established.

Assessment of pulmonary function in the early phase of ARDS in pediatric patients.

Scant data are available on lung function in acute respiratory distress syndrome (ARDS) in pediatric patients. We measured respiratory mechanics by single-breath occlusion and maximum expiratory flow-volume curves by forced deflation in ten critically ill infants with clinical ARDS. Ten mechanically ventilated infants without lung disease served as the control group. To assess the severity of the lung injury in the infants with ARDS, we modified an adult scoring system that calculates a score (from 0 to 4; > 2.5 indicates severe lung injury) based on the extent of chest radiographic changes, degree of hypoxemia, amount of positive end-expiratory pressure (PEEP), and total respiratory system compliance. The lung injury scores of our patients were in the range of 2.75 to 3.75. The lung injury scores of the control group were zero. The predominant alteration in lung function was restrictive, as characterized by a significant decrease in total respiratory system compliance (0.41 +/- 0.13 ml/cmH2O/kg versus 1.12 +/- 0.16 ml/cmH2O/kg of controls; P < 0.001) and forced vital capacity (21.5 +/- 6.5 ml/kg versus 59.2 +/- 6.3 ml/kg of controls; P < 0.001). Maximum expiratory flow rates at 10% forced vital capacity were significantly increased (23.6 +/- 20.1 ml/kg/sec versus 8.4 +/- 2.5 ml/kg/sec of controls; P < 0.05), confirming the absence of any significant obstructive abnormalities. The passive expiratory flow-volume curves were curvilinear and convex in shape, indicating inhomogeneous lung pathology. The inhomogeneous distribution of lung injury in ARDS restricts the validity of respiratory mechanics measurements that rely on a single-compartment model. However, the forced deflation technique allows accurate spirometric assessments of the severity of restrictive (and obstructive) lung function changes in intubated infants with severe ARDS. Such measurements can be incorporated into lung injury scoring systems to classify the severity of the disease process for the purpose of outcome evaluation and to evaluate the effect of therapeutic interventions.

Mechanism of lobar alveolar pressure decline during forced deflation in canine regional emphysema.

A canine model of unilobar papain-induced emphysema was used to examine the extent to which differences in alveolar pressures (PA) would develop between an emphysematous right lower lobe (RLL) and normal left lower lobe (LLL) during forced vital capacity (FVC) deflation. RLL and LLL PA (PARLL and PALLL, respectively) were measured by the alveolar capsule technique. During forced deflation, PA and lobar flows were determined between 95 and 20% FVC. A choke point common to both lower lobes was observed at > 40% FVC. The results showed that deflation compliance (C) was altered for the RLL such that <90% lobar vital capacity, CRLL > CLLL, whereas >90% lobar vital capacity, CRLL < CLLL. At 95 and 90% FVC, the initial RLL PA decline was greater than that for the LLL (P < 0.05). However, large differences in PA were prevented because of the effect of interdependence of regional expiratory flow (IREF). IREF caused a relative decrease in RLL flows and increase in LLL flows that limited PA differences. Between 80 and 50% FVC, as CRLL became greater than CLLL, and because of the initial effect of IREF, PARLL was approximately PALLL. At < and = 40% FVC, without IREF, lobar differences in PA widened. These findings indicate that IREF may affect the dynamics of flow limitation in regional lung disease.

Albuterol responsiveness in infants with respiratory failure caused by respiratory syncytial virus infection

Objective: To assess the bronchodilator effect of inhaled albuterol in the acute stage of severe respiratory syncytial virus (RSV) infection. Design: Prospective, nonrandomized study of previously healthy infants who underwent intubation and whose lungs were ventilated because of respiratory failure caused by RSV infection. Ten infants with an endotracheal tube in place and without lung disease were matched for age and weight and served as normal control subjects. Methods: Lung function tests, including respiratory mechanics by single-breath occlusion, small airway function by forced deflation, and lung volumes by nitrogen washout, were performed before and after inhalation of 900 μg albuterol by metered dose inhaler. Bronchodilator response was defined as a change of more than twice the coefficient of variation of repeated baseline measurements. Results: Twenty-three infants (mean ± SE age = 4.2 ± 1.1 months) were studied, of whom 20 (87%) had obstructive small airway disease, and 3 (13%) had exclusively restrictive lung function profiles. Ten of the infants with obstructive disease (50%) did not benefit from albuterol, and 9 (45%) had small but significant improvements in lung function. Deterioration of lung function was documented in 1 patient after albuterol inhalation. Conclusion: Inhaled albuterol is of limited value as a bronchodilator in infants with RSV-induced respiratory failure and should be discontinued if a beneficial response cannot be observed. (J P EDIATR 1995;127:485-90)

Factors determining lobar emptying during maximal and partial forced deflations in nonhomogeneous airway obstruction in dogs.

The partial expiratory flow-volume (PEFV) maneuver has been proposed as a sensitive test to detect nonuniform airway disease. We tested this hypothesis in seven dogs in an open-chest preparation in which the right upper lobe (RUL) bronchus was partially obstructed. Alveolar capsules were placed on the obstructed RUL and nonobstructed right lower lobe (RLL) to measure respective alveolar pressures (Palv) during PEFV and maximal expiratory flow-volume (MEFV) maneuvers. PEFV curves were initiated at about 75% of the whole-lung vital capacity (VC). A Pitot static tube was placed into the airway to identify sites of flow limitation (choke-points [CP]), frictional pressure losses to CP (Pfr), CP area (A*), and compliance (K*). Results were analyzed at 45% VC, where a central tracheal CP was identified, and at 29% VC, where lobar CP were identified. At both lung volumes, the results showed that during PEFV, Palv and flows of the obstructed RUL decreased, whereas Palv and flows of the RLL increased compared with values obtained during MEFV. However, total maximal expiratory flow (Vmax) did not change between maneuvers. At 45% VC, although Pfr decreased during PEFV, this decrease was not large enough to result in an increase in A* and hence total Vmax because CP were identified in the noncompliant trachea. At 29% VC, offsetting changes in lobar A* and flow occurred between maneuvers: during PEFV, RLL A* and flow relatively increased while RUL A* and flow decreased. This study describes the mechanisms that explain why the PEFV maneuver is not useful in the detection of nonhomogeneous airway obstruction.

Heterogeneous regional behavior during forced expiration before and after histamine inhalation in dogs.

We studied the evolution of alveolar pressure (PA) heterogeneity during the course of forced expiration in the lungs of six anesthetized open-chest dogs. Using an alveolar capsule technique, we measured PA simultaneously in six lung regions during full maximal forced deflations before and after administering aerosolized histamine. Flow was measured plethysmographically with volume obtained by flow integration. Heterogeneity was expressed as the coefficient of variation (CV) of regional PA after 25% of the vital capacity had been expired from total lung capacity. The CV in in vivo open-chest canine lungs (21.3%) was significantly greater than that we measured previously in excised lungs (8.7%) (P < 0.02). Inhalation of aerosolized solutions of histamine produced significant increases in interregional heterogeneity (CV = 35.5 and 38.8% after 3 and 10 mg/ml of histamine, respectively; P < 0.025). After histamine, the vital capacity was reduced and the configuration of the flow-volume curve demonstrated some shortening of the flow plateau commonly observed in dogs. Changes in the flow-volume relationship failed, however, to reflect well the marked degree of heterogeneity of PA after histamine administration. These findings may be reconciled on the basis of interdependence of regional expiratory flows. Reductions in flow from obstructed regions appear to be compensated by increases in flow from unobstructed regions and thus mask upstream nonuniformities. These mechanisms may explain in part why the maximal expiratory flow-volume curve has been a relatively insensitive tool for the detection of early nonuniform airway disease.

Pulmonary dysfunction after primary closure of an abdominal wall defect and its improvement with bronchodilators.

To determine the extent of pulmonary dysfunction following primary closure of an abdominal wall defect, we obtained pulmonary function tests (PFT) in 11 newborn infants with gastroschisis and 6 with large omphaloceles admitted to a newborn ICU in a children's hospital. Patients were 1 to 30 days of age at the time of the PFT; all required endotracheal intubation and mechanical ventilation for operative procedures or for postoperative ventilatory support. Full-term infants (n = 21) undergoing minor surgical procedures provided comparative measurements. Flow-volume curves were obtained with manual inflation of the lungs followed by forced deflation using negative pressure, or by passive expiration, under sedation and pharmacologic paralysis. Deflation flow-volume curves gave measurements of forced vital capacity (FVC) and maximal expiratory flow at 25% of vital capacity from residual volume (MEF25). Modified passive mechanics technique gave passive expiratory curves that provided measurements of respiratory system compliance (Crs) and resistance (Rrs). Tests were done: within 48 h (period A), 3-7 days (period B), and 8-30 days after surgical repair (period C). Pulmonary function testing after nebulized 0.1% isoetharine (a bronchodilator), to test for bronchial reactivity, began midway during the study period in 15 patients. Preoperative and postoperative tests were obtained in 5 patients. Closure of an abdominal wall defect decreased FVC, Crs, and MEF25 by up to 50% of normal, reference values after surgery (P less than 0.05). FVC and MEF25 approached values of normal infants by 4 weeks, whereas Crs remained 50% lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary dysfunction in surgical conditions of the newborn infant

To describe the pathophysiology of surgical conditions that are associated with respiratory insufficiency in the newborn infant. Survey. Newborn ICU in a children's hospital. Twenty-four newborn infants (1 to 28 days old) who required endotracheal intubation and mechanical ventilation for operative procedures or postoperative ventilatory support. Flow-volume curves obtained by manual inflation of the lungs, followed by forced deflation by negative pressure, and by passive expiration, under sedation and pharmacologic paralysis. Deflation flow-volume curves and passive expiratory curves were measured. Pulmonary function testing before and after bronchodilator administration (n = 11) began midway during the study period. Term and preterm groups served as controls. Forced vital capacity (FVC) was decreased in all groups with surgical disease as follows: abdominal wall defects and necrotizing enterocolitis groups to 48.3% and 62.1% that of preterm, respectively; pulmonary hypoplasia group to 55.5% that of term (p less than .05). Maximal expiratory flow at 25% of FVC decreased in all groups: abdominal wall defects and necrotizing enterocolitis group, to 36.8% and 37.9% that of preterm, respectively (p less than .05); pulmonary hypoplasia group, 20.0% that of term (p less than .05). The ratio of maximal expiratory flow at 25% of FVC divided by FVC was significantly decreased in necrotizing enterocolitis and pulmonary hypoplasia groups compared with that of preterm and term groups, respectively, but not in the abdominal wall defects group. Maximal expiratory flow at 25% of FVC, but not FVC, increased significantly (36%, p less than .05) after bronchodilator nebulization, indicating the presence of airway reactivity. Respiratory system compliance was decreased significantly (p less than .05) in all surgical disease groups compared with the term group. Bronchial reactivity contributes to decreased maximal expiratory flow at 25% of FVC, a feature also seen in premature infants with respiratory distress syndrome who later develop bronchopulmonary dysplasia. Babies who require chronic ventilatory support after operation and who have developed reactive airways may benefit from the administration of bronchodilators during postoperative ventilatory management.

Interdependence of regional expiratory flows limits alveolar pressure differences

Wilson et al. (J. Appl. Physiol. 59:1924-28, 1985) have asserted that interdependence of regional expiratory flows could cause differences of interregional alveolar pressures to relax to time-independent limits during forced deflation. To test the hypothesis that such limiting differences do arise, we examined regional alveolar pressures during complete and partial maximally forced deflations of six excised canine lungs. Alveolar pressures were monitored using alveolar capsules on each of six lobes during forced deflations initiated at transpulmonary pressures of 30, 20, 15, and 10 cmH2O. In all lungs and in all maneuvers, interregional heterogeneity of alveolar pressure increased rapidly early in the deflation but much less so or not at all later in the deflation. When we compared complete with partial forced deflations, 16 of 24 maneuvers in six lungs showed clear evidence that as deflation progressed the degree of heterogeneity at isovolumic points became independent of the transpulmonary pressure from which the deflation was initiated. That is, alveolar pressures relaxed to limiting interregional differences that did not depend on time elapsed from the onset of the deflation. These data offer strong evidence of the existence of limiting differences. Such behavior implies that the sequence of regional emptying is controlled by a competition of opposing influences: nonuniformities of airway and parenchymal properties promoting nonuniformity of emptying vs. interdependence of regional expiratory flows promoting uniformity. As nonuniformity of regional pressures grows so do those factors that oppose that nonuniformity. These data underscore the insensitivity of maximum expiratory flow-volume curve configuration to the underlying inhomogeneous pattern of regional lung emptying.

Early onset of airway reactivity in premature infants with bronchopulmonary dysplasia.

Pulmonary function during the early development of bronchopulmonary dysplasia (BPD) in premature infants is not well understood. Furthermore, it is not known how early airway reactivity appears in BPD. During a 14-month period we studied 32 infants (mean gestational age, 27.3 wk; mean birth weight, 1.02 kg) with respiratory distress syndrome in whom BPD eventually developed. We obtained maximal expiratory flow-volume (MEFV) curves by manual inflation of the lung followed by forced deflation with a negative pressure on 64 occasions (mean postnatal age, 43.1 days). At each test MEFV curves were obtained in 3 conditions: baseline; after normal saline aerosolization with manual ventilation as a control; and after bronchodilator. Maximal expiratory flow at 25% of FVC (Vmax25) was markedly decreased at baseline and remained decreased after saline control. The FVC also was decreased in both baseline and saline control studies. After bronchodilator there was a marked (p less than 0.001) increase in Vmax25 (+214% above saline control) together with a significant (p less than 0.001) increase in FVC (+21%). Of 23 infants studied after 3 wk of postnatal age, 21 exhibited a more than 30% increase in Vmax25 above control (defined as airway reactivity). The remaining 2 infants were already receiving bronchodilator therapy. The most premature infant with demonstrable airway reactivity was 26 wk postconception, and the youngest was 12 days old. In 13 infants who were studied initially before 3 wk of age, there was a highly significant correlation (r = 0.91 p less than 0.001) between the degree of airway reactivity and the severity of respiratory disease as determined by the duration of ventilator dependence. Airway reactivity may play an important role in the development and severity of BPD.