Efficacy of a New Full Face Mask for Noninvasive Positive Pressure Ventilation: Patient Selection
Prior to admission all patients were maximally treated with bronchodilators, supplemental oxygen, and on occasion theophylline for at least 48 h prior to study enrollment. All patients enrolled into the study fulfilled at least two clinical criteria and two physiologic criteria for implementation of noninvasive ventilation as shown in Table 1. Informed consent was obtained from all patients participating in the study. All patients underwent standard spirometric evaluation of lung function (Gould 2400 Spirometer, Dayton, Ohio). Respiratory muscle strength was evaluated by maximal inspiratory pressure and expiratory mouth pressure as described by Black and Hyatt. Arterial blood gas analysis was performed using an analyzer (BG3 Analyzer, Instrumentation Laboratory, Lexington, Mass).
All patients were evaluated for NPPV via a bilevel positive airway pressure device (BiPAP, Respironics, Monroeville, Pa) or a portable volume ventilator (PLV-102, Life Care, Boulder, Colo). A description of the ventilatory support system (BiPAP) has been previously well described by others. Appropriate settings of inspiratory and expiratory pressures and volumes and ventilatory mode (BiPAP vs portable volume ventilator) were chosen while monitoring airway pressure, airflow, and changes in tidal volume online antibiotics.
Airway pressure was monitored at the face mask via a pressure transducer (Validyne, range ± 100 cm H2O, Northridge, Calif). Changes in airflow were measured by a pneumotachograph (Hans Rudolph, Kansas City, Mo) placed between the mask and the exhalation valve, and inspired and expired volumes were recorded by integration of the airflow signal (Gould Recorder ES 1000, Dayton, Ohio). Titration of inspiratory and expiratory pressures for patients using the ventilatory support system and of ventilator-delivered tidal volume for patients using a volume ventilator were determined by achieving an expired minute ventilation of at least 20 percent over spontaneous ventilation while simultaneously improving gas exchange (increased Pa02/FIc>2, and lowered РаСОг), and ensuring patient-ventilator synchrony.
Table 1—Enrollment Criteria for Patients Receiving NPPV
|1.||Severe, irreversible chronic respiratory disease|
|2.||Symptoms of nocturnal hypoventilation, including morning headache, loss of energy, enuresis, nightmares, etc|
|3.||Dyspnea at rest or increased work of breathing impairing sleep or sustained rest|
|4.||Cor pulmonale due to hypoventilation and hypoxemia unresponsive to conventional treatment|
|1.||Vital capacity <25 percent predicted in patients with kyphoscoliosis or neuromuscular disease, but excluding patients with COPD or central hypoventilation; patients with COPD should have FEVi <25% predicted.|
|2.||PImax <50 cm H2O in COPD or <25 cm H2O in neuromuscular disease|
|3.||РаСОг >45 mm Hg and pH <7.32 persisting after appropriate treatment of airway obstruction and metabolic disturbances|
|4.||Nocturnal or sleep desaturation (Sa02 <88 percent) despite conventional oxygen therapy|
Category: Respiratory Symptoms
Tags: face mask, hypercapnia, noninvasive ventilation, respiratory failure