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Effects of Lung Squeezing Technique on Lung Mechanics in Mechanically-Ventilated Preterm Infants with Respiratory Distress Syndrome. Hong Kong Physiother J 2006. [DOI: 10.1016/s1013-7025(07)70007-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Abstract
Neonatal respiratory distress syndrome (RDS) remains one of the major causes of neonatal mortality and morbidity despite advances in perinatal care. The initial management of infants with RDS has almost become 'too routine' with little thought about the pathophysiological processes that lead to the disease and how the clinician can use the existing therapeutic interventions to optimize care. The transition from fetus to infant involves many complex adaptations at birth; the most important is the function of the lungs as a gas exchange organ. Preterm surfactant-deficient infants are less well equipped to deal with this transition. Optimum gas exchange is achieved through matching of ventilation and perfusion. In RDS, ventilation may be affected by homogeneity of the airways with atelectasis and over distension, as hyaline membranes block small airways. In turn this contributes to the inflammation that becomes bronchopulmonary dysplasia. Exogenous surfactant given early, particularly with positive end-expiratory pressure and, where necessary, gentle ventilation, would seem to be the optimum way to prevent atelectasis. How this can be achieved in neonates after surfactant therapy is explored through a review of the normal physiology of the newborn lung and how this is affected by RDS. The therapeutic interventions of resuscitation, exogenous surfactant, ventilation and inhaled nitric oxide are discussed in relation to their effects and what are currently the optimum ways to use these. It is hoped that with a better understanding of the normal physiology in the newborn lung, and the effects of both disease and interventions on that physiology, the practising clinician will have a greater appreciation of management of preterm infants with, or at risk of, RDS.
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Martinez F, Lewis J, Copland I, Engelberts D, Kavanagh BP, Post M, Schurch S, Belik J. Mechanical ventilation effect on surfactant content, function, and lung compliance in the newborn rat. Pediatr Res 2004; 56:19-25. [PMID: 15128929 DOI: 10.1203/01.pdr.0000128980.82797.29] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Studies of ventilator-associated lung injury in adult experimental animal models have documented that high tidal volume (TV) results in lung injury characterized by impaired compliance and dysfunctional surfactant. Yet, there is evidence that, in neonates, ventilation with a higher than physiologic TV leads to improved lung compliance. The purpose of our study was to evaluate how lung compliance and surfactant was altered by high TV ventilation in the neonate. We utilized a new model (mechanically air-ventilated newborn rats, 4-8 d old), and used 40 or 10 mL/kg TV strategies. Age-matched nonventilated animals served as controls. In all animals, dynamic compliance progressively increased after initiation of mechanical ventilation and was significantly greater than basal values after 60 min (p < 0.01). Lung lavage total surfactant with both TV strategies (p < 0.05) and the large aggregate fraction (only in TV = 40 mL/kg; p < 0.01) were significantly increased by 60 min of mechanical ventilation, compared with control animals. Ventilation with 40 mL/kg TV for 60 min adversely affected the lung surfactant surface-tension lowering properties (p < 0.01). After 180 min of ventilation with 40 mL/kg TV, the lung total surfactant content and dynamic compliance values were no longer distinct from the nonventilated animals' values. We conclude that, in the newborn rat, mechanical ventilation with a higher than physiologic TV increases alveolar surfactant content and, over time, alters its biophysical properties, thus promoting an initial but transient improvement in lung compliance.
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Affiliation(s)
- Francisco Martinez
- Department of Pediatics, University of Toronto, Hospital for Sick Children, Toronto, ON, M5G 1X8, Canada
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Hammer J, Patel N, Newth CJL. Effect of forced deflation maneuvers upon measurements of respiratory mechanics in ventilated infants. Intensive Care Med 2003; 29:2004-8. [PMID: 12897998 DOI: 10.1007/s00134-003-1895-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2002] [Accepted: 06/03/2003] [Indexed: 11/29/2022]
Abstract
OBJECTIVE 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. DESIGN AND SETTING Prospective study in the pediatric intensive care unit of a university children's hospital. PATIENTS 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). INTERVENTIONS 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. RESULTS . 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. CONCLUSIONS 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.
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Affiliation(s)
- Jürg Hammer
- Division of Pediatric Intensive Care and Pulmonology, University Children's Hospital, Römergasse 8, 4005, Basel, Switzerland.
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Platzker AC, Colin AA, Chen XC, Hiatt P, Hunter J, Koumbourlis AC, Schluchter MD, Ting A, Wohl ME. Thoracoabdominal compression and respiratory system compliance in HIV-infected infants. Am J Respir Crit Care Med 2000; 161:1567-71. [PMID: 10806156 DOI: 10.1164/ajrccm.161.5.9902066] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The thoracoabdominal compression technique (TAC) is used to measure expiratory flow in infants. We investigated whether TAC caused a change in total thoracic compliance (Crs), resistance (Rrs), and respiratory system time constant (Trs). We studied 41 infants (mean age, 12.4 mo; SD, 7.5) from five centers studying longitudinal lung and cardiovascular function of infants from HIV-infected mothers. We measured Crs, Rrs, and Trs before and after TAC. Changes in Crs, Rrs, and Trs after TAC were not dependent on the length of time since TAC. Crs and Trs were reduced after TAC, p = 0.013 and p = 0.003, respectively, whereas Rrs did not change. When compared with uninfected infants, HIV-infected infants had a larger post-pre TAC percent decline in Crs (p = 0.003) and a post-pre TAC rise in mean Rrs (p = 0.03). These differences remained significant after adjusting for sex and age. When performing infant pulmonary function testing, TAC itself produces a temporary decrease in Crs and Trs that is more significant in infants at risk for abnormal lung volume or compliance. Therefore, the sequence of performing the infant lung function parameters should be the same each time the testing is repeated with TAC as the last parameter tested at each testing session.
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Affiliation(s)
- A C Platzker
- The Divisions of Pediatric Pulmonology, Childrens Hospital Los Angeles, CA, USA.
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Hammer J, Newth CJ. Infant lung function testing in the intensive care unit. Intensive Care Med 1995; 21:744-52. [PMID: 8847430 PMCID: PMC7095417 DOI: 10.1007/bf01704742] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/1993] [Accepted: 08/30/1994] [Indexed: 02/02/2023]
Abstract
As a result of the previous shortage of tools to assess objectively the overall physiological status of the respiratory system in infants and young children, it has been difficult to measure the degree of physiological disorder or the response to therapy in respiratory diseases such as BPD, the pediatric version of ARDS, bronchiolitis, pneumonia, asthma and croup in this patient population. The newborn- four-year old child is particularly difficult to study because of their lack of cooperation and size. The recent progress in computer technology made pulmonary function testing available for this age range and opened up new possibilities for monitoring changes in disease processes affecting the respiratory system. This may improve medical management of infants and children with lung and heart diseases in particular. In 1989, Shannon [49] proposed in this Journal that the minimum physiological information needed for the intelligent use of mechanical ventilation (particularly if lower airway and/or pulmonary parenchymal disease was apparent) required the measurement of at least 4 variables: i) arterial partial pressure of carbon dioxide; ii) arterial oxygen saturation; iii) the mechanical time constant of the lung and iv) FRC. In many circumstances, arterial CO2 is approximated by alveolar (end-tidal) CO2 and the arterial oxygen saturation is obtained from pulse oximetry accurately if perfusion is adequate. The mechanical time constant and FRC are easily measured by the techniques described above and together provide important information concerning appropriate ventilator settings for a given disease. The described techniques bring new insights and awareness, but also new responsibilities in the management of infants and children with respiratory compromise. Not all of these techniques need to be applied to all infants in the ICU. Not all the assumptions upon which some of the techniques we have described are based will prove true. Any such methods which do not withstand solid scientific testing must be quickly discarded and replaced with better and (hopefully) easier methods.
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Affiliation(s)
- J Hammer
- Division of Pediatric Critical Care, Children's Hospital of Los Angeles, University of Southern California School of Medicine 90027, USA
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Marsh MJ, Ingram D, Milner AD. The effect of instrumental dead space on measurement of breathing pattern and pulmonary mechanics in the newborn. Pediatr Pulmonol 1993; 16:316-22. [PMID: 8255637 DOI: 10.1002/ppul.1950160508] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effect of the instrumental dead space on breathing pattern and the values of pulmonary mechanics was evaluated because of concern about the relatively large dead space of 26 mL in a commercially available system. Sixty-three healthy newborn infants were studied with a system as commercially supplied, and with the dead space eliminated using a 2 L/min biased flow. This led to a significant reduction in mean (+/- SD) values of respiratory rate from 56.8 (+/- 11.7) to 48.2 (+/- 11.7) breath/min (P < 0.0001), tidal volume from 5.2 (+/- 1.3) to 4.9 (+/- 0.9) mL/kg (P < 0.05), minute volume from 284 (+/- 68) to 220 (+/- 63) mL/min/kg (P < 0.0001), and work of breathing from 13.7 (+/- 6.6) to 11.8 (+/- 7.6) g.cm/kg (P < 0.02). There was a significant increase in dynamic lung compliance from 5.2 (+/- 1.5) to 5.6 (+/- 1.2) mL/cm H2O (P < 0.01) but no difference for total pulmonary resistance 39.6 (+/- 22.8) and 38.8 (+/- 22.2) cm H2O/L/sec. This shows that the instrumental dead space prevents measurement of the basal breathing patterns and alters the values of pulmonary mechanics. It is, therefore, important to use equipment with low dead space or make efforts to remove it by using a biased flow system such as we describe when measuring breathing patterns and pulmonary mechanics in the newborn.
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Affiliation(s)
- M J Marsh
- Department of Paediatrics, St. Thomas' Hospital, London, U.K
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Kano S, Lanteri CJ, Pemberton PJ, Lesouef PN, Sly PD. Fast versus slow ventilation for neonates. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1993; 148:578-84. [PMID: 8368626 DOI: 10.1164/ajrccm/148.3.578] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
To investigate the effect of ventilation rate on respiratory mechanics, 21 neonates ventilated in the neonatal period for various reasons were studied while being ventilated at 30 and 80 breaths/min. Dynamic respiratory system elasticity (ERS), dynamic respiratory system resistance (RRS), and alveolar pressure at end expiration (EEP) were calculated by using multilinear regression to fit the equation of motion of a linear single-compartment model. Technically satisfactory data were obtained from 13 neonates. With the fast ventilation rate, tidal volume and RRS decreased by a mean of 41.3% (p < 0.01) and 17.5% (p < 0.01), respectively, ERS and EEP increased by a mean of 8.3% (p < 0.05) and 22.2% (p < 0.01), respectively. Fast ventilation produced a shorter effective time constant during expiration, limiting the changes in EEP and, hence, in end-expiratory lung volume. The same changes in respiratory mechanics were also observed in neonates who did not show an increase in EEP even at high frequency. These neonates had a high elastance and time constant short enough to ensure adequate lung emptying. These results suggest that the respiratory mechanics of ventilated neonates are frequency dependent and that neonates with higher ERS, such as those with hyaline membrane disease, can cope with fast rate ventilation without developing dynamic hyperinflation.
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Affiliation(s)
- S Kano
- Western Australian Research Institute for Child Health, Perth
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Respiratory mechanics in infants: physiologic evaluation in health and disease. American Thoracic Society/European Respiratory Society. THE AMERICAN REVIEW OF RESPIRATORY DISEASE 1993; 147:474-96. [PMID: 8430975 DOI: 10.1164/ajrccm/147.2.474] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Silva Neto G, Gerhardt T, Silberberg A, Gerhardt T, Claure N, Duara S, Bancalari E. Nonlinear pressure/volume relationship and measurements of lung mechanics in infants. Pediatr Pulmonol 1992; 12:146-52. [PMID: 1641270 DOI: 10.1002/ppul.1950120304] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We examined the effects of within-breath changes in compliance (C) upon the accuracy of measurements of compliance and resistance (R) by linear regression analysis and by Mead and Wittenberger's method. These effects were illustrated by a computer model and by lung models with linear and nonlinear pressure/volume relationships, and were also studied in 14 normal spontaneously breathing premature infants (mean +/- SD, BW 1,290 +/- 200 g, GA 29.9 +/- 2.7 weeks, age 7.4 +/- 2.1 days). Flow was measured by pneumotachography and tidal volume was derived as digitally integrated flow, and transpulmonary pressure as airway minus esophageal pressure. We found that C and R calculated from the equation of motion is accurate only if C and R remain constant throughout the respiratory cycle. Calculated compliance depends more on C at the end than at the beginning of inspiration. A decreasing C leads to underestimation or R, while an increasing C leads to an overestimation of inspiratory R. Calculated total R may be accurate, but with low r values for measurement points. Mead and Wittenberger's method and the regression method are similarly affected by changing C; however, since the regression method is based on many more measurement points and therefore allows the detection and analysis of within-breath changes of C and R, it is less prone to erroneous results secondary to signal artifacts than Mead and Wittenberger's method.
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Affiliation(s)
- G Silva Neto
- Department of Pediatrics, School of Medicine, University of Miami, Florida
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Ratjen FA, Wiesemann HG. Variability of dynamic compliance measurements in spontaneously breathing and ventilated newborn infants. Pediatr Pulmonol 1992; 12:73-80. [PMID: 1570192 DOI: 10.1002/ppul.1950120203] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We studied reproducibility and variability of dynamic pulmonary compliance (Cdyn) by making measurements with the esophageal balloon at multiple locations within the esophagus, in both spontaneously breathing and mechanically ventilated newborn infants. Reliable measurements could be obtained over a range similar to that reported for measurements with a liquid-filled catheter. In spontaneously breathing infants Cdyn was found to be highly variable. This variability was unrelated to catheter position but was associated with concomitant changes in pulmonary resistance. Probably because of the high variability, the correlation of Cdyn with a measurement of respiratory system compliance (Crs) was rather poor (r = 0.63). Cdyn measured in mechanically ventilated infants was significantly less variable and compared favorably to Crs (r = 0.86), but its accuracy could not be adequately assessed since the comparison of esophageal and airway occlusion pressure was not feasible in all infants. In addition, significant differences in Cdyn were found between spontaneous and ventilated breaths during mechanical ventilation. Further studies in both ventilated and spontaneously breathing infants are needed to assess the variability of Cdyn over extended time periods.
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Affiliation(s)
- F A Ratjen
- Department of Pediatrics, University of Essen, Germany
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Standaert TA, Wilham BE, Mayock DE, Watchko JF, Gibson RL, Woodrum DE. Respiratory mechanics of the piglet during the first month of life. Pediatr Pulmonol 1991; 11:294-301. [PMID: 1758753 DOI: 10.1002/ppul.1950110405] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Piglets at 3, 14, and 30 days of age were studied to assess the postnatal changes in lung, chestwall, and total respiratory system compliance associated with normal growth. Static deflation compliance of the lung and total respiratory system increased significantly with age; there was no change in chestwall compliance. When normalized for body weight or lung volume, all measures of compliance tended to decrease with postnatal age. Measures of lung and chestwall compliance obtained with an end-inspiratory occlusion technique were less than the static compliance measures, but demonstrated the same relative changes with postnatal maturation. Chestwall compliance at 3 days of age was only 1.3 times greater than lung compliance and there was no significant change in this ratio with postnatal age. In contrast to the trend for the human infant, the piglet's chestwall at 3 days of age is stiff relative to the lung and does not become stiffer with age over the first 4 weeks of life.
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Affiliation(s)
- T A Standaert
- Department of Pediatrics, University of Washington, Seattle 98195
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