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Respir Care. 2016 Feb;61(2):134-41. doi: 10.4187/respcare.04063. Epub 2015 Nov 24.

Assessment of Factors Related to Auto-PEEP.

Author information

1
Department of Anesthesia and Intensive Care, Fondazione Poliambulanza Hospital, Brescia, Italy. giuseppe.natalini@gmail.com.
2
Department of Anesthesia and Intensive Care, Spedali Civili Hospital, Brescia, Italy.
3
Department of Anesthesia and Intensive Care, Fondazione Poliambulanza Hospital, Brescia, Italy.
4
Department of Anesthesia and Intensive Care, SS Annunziata Hospital, Savigliano, Italy.
5
Department of Anesthesia and Intensive Care, Misericordia Hospital, Grosseto, Italy.
6
Department of Anesthesia and Intensive Care, San Giovanni Bosco Hospital, Napoli, Italy.
7
Department of Anesthesia and Intensive Care, Cardarelli Hospital, Napoli, Italy.
8
Department of Anesthesia and Intensive Care, Mellino Mellini Hospital, Chiari, Italy.
9
Department of Anesthesia and Intensive Care, Agnelli Hospital, Pinerolo, Italy.
10
Department of Anesthesia and Intensive Care, Santa Maria degli Angeli Hospital, Pordenone, Italy.
11
Department of Anesthesia, Critical Care Medicine, and Emergency, University of Brescia at Spedali Civili, Brescia, Italy.
12
Department of Anesthesia and Intensive Care, Cattinara Hospital, Trieste, Italy.
13
Respiratory Epidemiology, Occupational Medicine & Public Health, Imperial College, London, United Kingdom.

Abstract

BACKGROUND:

Previous physiological studies have identified factors that are involved in auto-PEEP generation. In our study, we examined how much auto-PEEP is generated from factors that are involved in its development.

METHODS:

One hundred eighty-six subjects undergoing controlled mechanical ventilation with persistent expiratory flow at the beginning of each inspiration were enrolled in the study. Volume-controlled continuous mandatory ventilation with PEEP of 0 cm H2O was applied while maintaining the ventilator setting as chosen by the attending physician. End-expiratory and end-inspiratory airway occlusion maneuvers were performed to calculate respiratory mechanics, and tidal flow limitation was assessed by a maneuver of manual compression of the abdomen.

RESULTS:

The variable with the strongest effect on auto-PEEP was flow limitation, which was associated with an increase of 2.4 cm H2O in auto-PEEP values. Moreover, auto-PEEP values were directly related to resistance of the respiratory system and body mass index and inversely related to expiratory time/time constant. Variables that were associated with the breathing pattern (tidal volume, frequency minute ventilation, and expiratory time) did not show any relationship with auto-PEEP values. The risk of auto-PEEP ≥5 cm H2O was increased by flow limitation (adjusted odds ratio 17; 95% CI: 6-56.2), expiratory time/time constant ratio <1.85 (12.6; 4.7-39.6), respiratory system resistance >15 cm H2O/L s (3; 1.3-6.9), age >65 y (2.8; 1.2-6.5), and body mass index >26 kg/m(2) (2.6; 1.1-6.1).

CONCLUSIONS:

Flow limitation, expiratory time/time constant, resistance of the respiratory system, and obesity are the most important variables that affect auto-PEEP values. Frequency expiratory time, tidal volume, and minute ventilation were not independently associated with auto-PEEP. Therapeutic strategies aimed at reducing auto-PEEP and its adverse effects should be primarily oriented to the variables that mainly affect auto-PEEP values.

KEYWORDS:

artificial; intrinsic; positive-pressure respiration; respiration; respiratory function tests; respiratory insufficiency; respiratory mechanics; respiratory physiological phenomena

PMID:
26604329
DOI:
10.4187/respcare.04063
[Indexed for MEDLINE]
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