A theoretical analysis of interrupter technique for measuring respiratory mechanics

Bates, Jason H. T.; Baconnier, Pierre; Milic–Emili, J.

doi:10.1152/jappl.1988.64.5.2204

Cited by 217 publications

(136 citation statements)

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“…The significance of R init ((P trmax -P 1 )/ flow) or (DP 1 ) has only recently been clarified in human beings, as essentially representing airway resistance (24). As described above, the difference between P 1 and P 2 (i.e., DP 2 ) represents the slow postocclusion decay in tracheal pressure and may reflect stress relaxation due to the viscoelastic properties of the respiratory system and possibly the Pendelluft phenomenon that represents distribution of air among the different lung regions (11,(25)(26)(27). In normal subjects, Pendelluft probably has a relatively small role, however, this phenomenon may be more evident if there were an increase in time constant inhomogeneities of alveolar inflation and deflation within the lung.…”

Section: Discussionmentioning

confidence: 99%

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

Auler

Carmona

Barbas

et al. 2000

Braz J Med Biol Res

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We prospectively evaluated the effects of positive end-expiratory pressure (PEEP) on the respiratory mechanical properties and hemodynamics of 10 postoperative adult cardiac patients undergoing mechanical ventilation while still anesthetized and paralyzed. The respiratory mechanics was evaluated by the inflation inspiratory occlusion method and hemodynamics by conventional methods. Each patient was randomized to a different level of PEEP (5, 10 and 15 cmH 2 O), while zero end-expiratory pressure (ZEEP) was established as control. PEEP of 15-min duration was applied at 20-min intervals. The frequency dependence of resistance and the viscoelastic properties and elastance of the respiratory system were evaluated together with hemodynamic and respiratory indexes. We observed a significant decrease in total airway resistance (13.12 ± 0.79 cmH 2 O l -1 s -1 at ZEEP, 11.94 ± 0.55 cmH 2 O l -1 s -1 (P<0.0197) at 5 cmH 2 O of PEEP, 11.42 ± 0.71 cmH 2 O l -1 s -1 (P<0.0255) at 10 cmH 2 O of PEEP, and 10.32 ± 0.57 cmH 2 O l -1 s -1 (P<0.0002) at 15 cmH 2 O of PEEP). The elastance (E rs ; cmH 2 O/l) was not significantly modified by PEEP from zero (23.49 ± 1.21) to 5 cmH 2 O (21.89 ± 0.70). However, a significant decrease (P<0.0003) at 10 cmH 2 O PEEP (18.86 ± 1.13), as well as (P<0.0001) at 15 cmH 2 O (18.41 ± 0.82) was observed after PEEP application. Volume dependence of viscoelastic properties showed a slight but not significant tendency to increase with PEEP. The significant decreases in cardiac index (l min -1 m -2 ) due to PEEP increments (3.90 ± 0.22 at ZEEP, 3.43 ± 0.17 (P<0.0260) at 5 cmH 2 O of PEEP, 3.31 ± 0.22 (P<0.0260) at 10 cmH 2 O of PEEP, and 3.10 ± 0.22 (P<0.0113) at 15 cmH 2 O of PEEP) were compensated for by an increase in arterial oxygen content owing to shunt fraction reduction (%) from 22.26 ± 2.28 at ZEEP to 11.66 ± 1.24 at PEEP of 15 cmH 2 O (P<0.0007). We conclude that increments in PEEP resulted in a reduction of both airway resistance and respiratory elastance. These results could reflect improvement in respiratory mechanics. However, due to possible hemodynamic instability, PEEP should be carefully applied to postoperative cardiac patients.

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Section: Discussionmentioning

confidence: 99%

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

Auler

Carmona

Barbas

et al. 2000

Braz J Med Biol Res

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“…If the flow of gas at the airway opening is suddenly interrupted during passive expiration by a rapidly shutting valve, one observes two distinct pressure changes just proximal to the valve. The first change, Pinit, is virtually immediate and reflects the resistive pressure drop across the airways (13,18) and the chest wall (19). This is followed by a second, slower pressure change, Pdiff, to a plateau equal to the static recoil pressure of the respiratory system (Fig.…”

Section: Methodsmentioning

confidence: 99%

Effect of Volume History on Measurements of Respiratory Mechanics Using the Interrupter Technique

Freezer

Nicolaï

Sly³

1993

Pediatr Res

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ABSTRACT. The importance of the viscoelastic properties of the tissues of the respiratory system has recently been recognized, and lung models have been produced to describe the resistive and viscoelastic properties of the lung. The pulmonary mechanics of 10 rabbits were studied using the interrupter technique to assess the effect of volume history on the resistive and viscoelastic elements of the respiratory system. The influence of the tone of the muscles of respiration was also studied. In healthy lungs, the resistive and viscoelastic elements of the lung are dependent on the volume history of the respiratory system and are significantly lower if these elements do not reach a resting position before expiration. The chest wall made a significant contribution to the resistive and viscoelastic elements of the respiratory system, which was also dependent on the lung volume history. The tone of the muscles of respiration had no effect on the resistive or viscoelastic elements of the respiratory system. (Pediatr Res 33: 261-266, 1993) Abbreviations R1, resistance of respiratory system RZ, dissipative properties of lung or chest wall El, static elastance of respiratory system E2, elastic properties ET, endotracheal FRC, functional residual capacity Pao, airway opening pressure Pes, esophageal pressure Pdiff, static recoil pressure of respiratory system Pinit, resistance pressure drop across airways and chest wall Rinit, Newtonian flow resistance of airways and chest wall Rrs, flow resistance of the respiratory system ANOVA, analysis of variance RE=, endotracheal tube resistance Recently, the importance of the viscoelastic properties of the tissues of the respiratory system has been recognized (1-10). The two-compartment model for the lung that best represents experimental data consists of a single alveolar compartment surrounded by a viscoelastic tissue compartment (1 1), and models have been produced to describe the resistive and viscoelastic properties of the lung. This model can be represented by springs 26and dashpots as shown in Figure 1, where R1 represents the airway resistance and any Newtonian component of tissue resistance that is in parallel with another three elements (El, E2, and R2) in the form of the Kelvin body, an elastic element in parallel with a series elastance-resistance. El represents the static elastance of the respiratory system and E2 and R2 the dissipative and elastic properties of the tissues of the lung and chest wall (12). If the two bars at either end of the model are moved relative to each other to represent the changes in volume during respiration, the properties of R1, El, R2, and E2 determine the behavior of the model. If the bars are stopped abruptly, simulating a flow interruption, the "energy dissipation" in R I and El will stop immediately; however, some time will be required for R2 and E2 to reach their resting position. This model allows a better description of the changes in Pao observed after rapid airway occlusions during passive expiration than the traditional one-com...

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“…The method used for the determination of pulmonary mechanics allows the identification of its elastic, resistive and viscoelastic and/or inhomogeneous components [18,25]. In group I, EL,st, DEL, DPL,tot, DP2L and RL,int tended to increase progressively as a function of time, but were significantly higher than control values only at 120 min postinfarction (table 2).…”

Section: Discussionmentioning

confidence: 99%

Pulmonary morphofunctional effects of acute myocardial infarction

Faffe¹,

Chagas²,

Medeiros³

et al. 1999

Eur Respir J

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Acute myocardial infarction (AMI) may yield several respiratory changes. Nevertheless, no comprehensive pulmonary morphological/physiological correlation has been performed under this condition. The aims of the present investigation were: 1) to determine the respiratory parameters in an experimental model of coronary artery occlusion, 2) to relate these results to findings from lung histopathology, and 3) to evaluate the effects of propranolol used prior to AMI.Twenty-eight rats were anaesthetized and mechanically ventilated. In the control group (C), a suture line was passed around the left anterior descending coronary artery (LADCA). The infarct group (I) was similarly prepared but the LADCA was ligated and infarct resulted. In the control/propranolol (CP) and infarct/propranolol (IP) groups, propranolol was intravenously injected 5 min before surgery as performed in groups C and I, respectively. Lung static (EL,st) and dynamic (EL,dyn) elastances, airway resistance (RL,int), and viscoelastic/inhomogeneous pressure (DP2L) were determined before and 30, 60 and 120 min after surgery.In group I, EL,st, EL,dyn, RL,int and DP2L increased progressively throughout the experiment, and were higher than those found in groups C, CP and IP. All respiratory parameters but EL,st remained unaltered in group IP. Lung histopathological examination demonstrated alveolar, interstitial and intrabronchial oedema in group I. Group IP showed only interstitial oedema.Acute myocardial infarction yields lung resistive, elastic and viscoelastic changes. The last two results from alveolar and interstitial oedema, respectively. The previous use of propranolol diminishes respiratory changes.

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A theoretical analysis of interrupter technique for measuring respiratory mechanics

Cited by 217 publications

References 0 publications

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

Effect of Volume History on Measurements of Respiratory Mechanics Using the Interrupter Technique

Pulmonary morphofunctional effects of acute myocardial infarction

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