The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

THE USE OF PEEPIN A MECHANICALLY VENTILATED PEDIATRIC ASTHMATIC: A CASE REPORT.

Roberta L.Hales BS, RRT, Theresa Ryan Schultz BA, RRT, RN, Ann Marie DeLucca CRTT,Troy Dominguez MD, Andrew Costarino MD. The Children?s Hospital of Philadelphia.Philadelphia, PA.

Backround: Approximatelyten percent of patients admitted, to our institution with asthma, require intensivecare. Recognizing the need for a systematic approach to the management of thesepatients, a critical care asthma pathway was developed, including the use ofcontinuous albuterol, intravenous (IV) terbutaline, heliox therapy, inhaledisoflurane and guidelines for the management of positive pressure mechanicalventilation. The asthma patient requiring positive pressure mechanicalventilation presents a unique challenge. The literature suggests that the applicationof PEEP may reduce the work of breathing in patients with severe airflowobstruction either during the weaning phase from mechanical ventilation or whenventilatory assistance is required for respiratory muscle fatigue (1). Our protocolrecommends frequent assessment of auto-PEEP and guidelines for the applicationof mechanical PEEP (extrinsic). Extrinsic PEEP is set at zero in the chemicallyparalyzed patient and at the level of measured auto-PEEP in the spontaneouslybreathing patient.

Introduction: This 16-kgfemale, with a history of asthma, was admitted to an outlying Emergency Departmentin severe respiratory distress. She presented with altered mental status, minimalairflow movement with inspiratory and expiratory wheezing upon auscultation,cyanosis with a SpO2 86% in room air, tachypnic to 44 breaths perminute, tachycardic to 200 beats per minute, nasal flaring, and substernal retractions.The patient received subcutaneous epinephrine twice, IV magnesium sulfate, solumedrol,terbutaline, continuous inhaled albuterol and intermittent inhaled atrovent.With minimal response to therapy and evidence of a primary respiratory acidosis,pH of 7.0 and PaCO2 125 torr, the patient was intubated and transferredto our institution. Upon arrival to our Pediatric Intensive Care Unit, she wasreintubated with a 5.0 cuffed endotracheal tube and ventilated with SynchronizedIntermittent Mandatory Ventilation (SIMV) mode, mechanical frequency 15, TidalVolume (VT) 130ml, PEEP 0 cmH20, Inspiratory Time (Ti).75seconds, FiO2 1.0; resultant peak pressure (PIP) of 43cmH2O.The chest radiograph, at this time indicated, hyperinflation with a right lowerlobe atelectasis. As respiratory acidosis persisted (maximum PaCO2of 191 torr), care was escalated in accordance with the critical care asthmapathway to include: continuous IV terbutaline, intermittent IV steroids, ketamine,pancuronium, magnesium and calcium, isoflurane inhalation and albuterol viain-line metered dose inhaler with a spacer device. After sixteen hours of mechanicalventilation, the patient?s condition stabilized and the neuromuscular blockadewas discontinued. Measured auto-PEEP was 14 cm H2O and arterial bloodgas analysis indicated pH 7.34, PCO2 57 torr, PO2 98 torr,HCO3 30 base excess 3.8 on SIMV, frequency 24, VT 180ml,PEEP 3 cmH2O, Ti .6seconds, FiO2 .45 and PIP 50-55cmH2O.Frequent assessment of auto-PEEP was done utilizing a Bicore CP100 to determinebest PEEP in this now spontaneously breathing patient.

PEEP (cmH2O)PIP (cmH2O)ExhaledVT (ml)AirwayResistance (cm/L/sec)Lung Compliance(ml/cm H2O)
344129529
5431375410
8391485515
10371554820
12371604530
14371544145

Because meeting auto-PEEP yieldedbest lung compliance and airway resistance, while maintaining adequate oxygenationand ventilation, with a subjective assessment consistent with improved workof breathing in this awake, spontaneously breathing patient, 14 cm H2Oof mechanical PEEP was continued. Assessments of auto-PEEP continued and decrementsin applied mechanical PEEP were adjusted accordingly. This patient was successfullyweaned to extubation within 12 hours.

Discussion: Application ofmechanical PEEP at the level matching measured auto-PEEP seemed beneficial inthe management of this pediatric asthma patient requiring positive pressuremechanical ventilation. The use of extrinsic PEEP and timing of its application,deserves further investigation.

1. Gottfried SB, Rossi A, Milic-EmiliJ. Dynamic Hyperinflation, Intrinsic PEEP and the

Mechanically Ventilated Patient.Intensive Critical Care Digest 1986: 5:30-3.

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