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Effects of the inspiratory pressure waveform during patient-triggered ventilation on pulmonary stretch receptor and phrenic nerve activity in cats
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health, Pediatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health, Pediatrics.
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2001 (English)In: Critical Care Medicine, ISSN 0090-3493, E-ISSN 1530-0293, Vol. 29, no 6, 1207-1214 p.Article in journal (Refereed) Published
Abstract [en]

Objective:

To examine the effects of square wave, sinusoidal, and linear inspiratory pressure waveforms during pressure-controlled assist/control ventilation on the firing pattern of pulmonary stretch receptors and phrenic nerve activity.

Design:

Experimental, comparative study.

Setting:

Research laboratory at a university biomedical center.

Subjects:

Nine anesthetized, endotracheally intubated young cats (2.5–3.4 kg).

Intervention:

With interposed periods of continuous positive airway pressure (0.2 kPa), each cat was exposed to periods of assist/control ventilation with three different pressure waveforms, where the peak inspiratory pressure (0.74 ± 0.13 kPa), end-expiratory pressure (0.2 ± 0.02 kPa), and tidal volume (14.9 ± 5.22 mL/kg) were kept constant. Preset controlled ventilator rate was set below the rate of spontaneous breathing, and the mechanical inflation time equaled the inspiratory time during spontaneous breathing on continuous positive airway pressure.

Measurements and Main Results:

Respiratory rate and arterial blood gases did not change between the three pressure waveforms during assist/control ventilation. Peak pulmonary stretch receptor activity was lower and mean phrenic nerve activity higher during continuous positive airway pressure than during assist/control ventilation (p < .05). Peak inspiratory pulmonary stretch receptor activity was the same with all three pressure waveforms (82 ± 17 impulses·sec-1) but occurred earlier with square wave than with sinusoidal or linear pressure waveforms (p < .05). The total number of impulses in the phrenic nerve activity burst was smaller with square wave than with the other two pressure waveforms (0.21 ± 0.17 vs. 0.33 ± 0.27 and 0.42 ± 0.30 arbitrary units;p < .05), and the phrenic nerve activity burst duration was shorter with square wave (1.10 ± 0.45 vs. 1.54 ± 0.36 and 1.64 ± 0.25 secs;p < .05).

Conclusion:

Square wave pressure waveform during pressure-controlled assist/control ventilation strongly inhibits spontaneous inspiratory activity in cats. One mechanism for this inhibition is earlier and sustained peak pulmonary stretch receptor activity during inspiration. These findings show that differences in inspiratory pressure waveforms influence the spontaneous breathing effort during assist/control ventilation in cats.

Place, publisher, year, edition, pages
2001. Vol. 29, no 6, 1207-1214 p.
National Category
Pediatrics
Identifiers
URN: urn:nbn:se:uu:diva-92392PubMedID: 11395606OAI: oai:DiVA.org:uu-92392DiVA: diva2:165447
Available from: 2004-11-15 Created: 2004-11-15 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Regulation of Breathing under Different Pulmonary Conditions
Open this publication in new window or tab >>Regulation of Breathing under Different Pulmonary Conditions
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The breathing pattern of preterm infants is immature and is associated with a variety of reflexes. In a patient on the ventilator these reflexes interfere with spontaneous breathing. A better understanding of the immature control of breathing could lead to further improvements in ventilatory techniques. This thesis concerns studies of pulmonary stretch receptor (PSR) and phrenic nerve activity as part of the regulation of breathing in an animal model.

During assist/control ventilation with three different inspiratory pressure waveforms in animals with healthy lungs, squarewave pressure waveform strongly inhibits spontaneous inspiratory activity.

During partial liquid ventilation (PLV) in animals with healthy lungs, all PSRs studied maintained their phasic character, with increased impulse frequency during inspiration. PSR activity was not higher during PLV than during gas ventilation (GV), indicating that there was no extensive stretching of the lung during PLV.

During proportional assist ventilation (PAV) the applied airway pressure is servo-controlled proportionally to the ongoing breathing effort, thereby interacting with the activity of PSRs. Peak PSR activity was higher and occurred earlier during PAV than during CPAP. The regulation of breathing is maintained during PAV in surfactant-depleted animals before and early after surfactant instillation, with a higher ventilatory response and a lower breathing effort than during CPAP in both conditions.

Both lung mechanics and gas exchange influence the regulation of breathing. Inhibition of inspiratory activity occurred at a lower arterial pH and a higher PaCO2 during PLV than during GV in animals with surfactant-depleted lungs, which might be related to recruitment of a larger number of pulmonary stretch receptors during PLV.

In summary, selected aspects of the regulation of breathing were studied in an animal model with different ventilatory techniques under different lung conditions similar to those that can occur in infants.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 40 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1390
Keyword
Pediatrics, Control of breathing, Pulmonary Stretch Receptor, Phrenic Nerve Activity, Respiratory Distress Syndrome, Surfactant, Partial Liquid Ventilation, Assisted Ventilation, Pediatrik
National Category
Pediatrics
Identifiers
urn:nbn:se:uu:diva-4671 (URN)91-554-6096-8 (ISBN)
Public defence
2004-12-06, Rosensalen, Children's University Hospital, 751 85, Uppsala, 09:15
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Available from: 2004-11-15 Created: 2004-11-15 Last updated: 2013-12-10Bibliographically approved

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Sindelar, RichardJonzon, Anders

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