HFCWO on Pneumonic Respiratory Failure
Condition: Acute Respiratory Failure; Pneumonia
MeSH terms: Respiratory Insufficiency
Study type: Interventional

Summary: 
      BACKGROUND: Endotracheal intubation and prolonged immobilization of patients receiving
      mechanical ventilation may reduce expectoration function. High frequency chest wall
      oscillation (HFCWO) may ameliorate airway secretion movement; however, the vigorous
      oscillation may influence ventilator settings and change instantaneous cardiopulmonary
      responses. The aim of this study was to investigate these issues. METHODS: Seventy-three
      patients aged >20 years who were intubated with mechanical ventilation for pneumonic
      respiratory failure were recruited and randomly classified into two groups (HFCWO group,
      n=36; and control group who received conventional chest physical therapy (CCPT), n=37). HFCWO
      was applied with a fixed protocol, while CCPT was conducted using standard protocols. Both
      groups received sputum suction after the procedure. Changes in ventilator settings and the
      subjects' responses were measured at pre-set intervals and compared within groups and between
      groups.
    

Detailed description: 
      Pneumonia may increase bronchial secretion and decrease mucociliary function, thereby causing
      lung atelectasis. Patients with acute pneumonic respiratory failure receiving mechanical
      ventilation may therefore have a large amount of pulmonary secretions, thereby worsening
      bronchial hygiene, oxyhemoglobin saturation and ventilation-perfusion match. Cough function
      is paramount for expectoration; however, coughing is not practical for patients with
      endotracheal intubation and sedation. High frequency chest wall oscillation (HFCWO) may
      dislodge airway secretions as efficiently as conventional chest physical therapy (CCPT).
      However, pneumonia is not currently an indication for chest physical therapy.

      HFCWO compresses and relaxes the chest wall to generate an oscillated volume from the lungs,
      mimicking a "mini-cough" and producing shear stress at the air-mucus interface which changes
      the sputum rheology, thereby improving ventilation distribution, gas mixing, and forced
      expired volume in one second. Most studies that have reported no significant effects have
      focused on mortality, hospital stay, lung function or BODE (a multidimensional 10-point scale
      of body mass index, severity of airflow obstruction, dyspnea rated with the modified Medical
      Research Council, and exercise capacity evaluated with the Six-Minute Walk Distance) score.
      However, these outcome measurements are not associated with the immediate effects of chest
      physical therapy and may be affected by other factors such as disease severity.

      Using the amount of sputum as the outcome measurement of HFCWO is not strongly recommended.
      However, immediate cardiopulmonary changes in HFCWO have not been studied in patients
      receiving mechanical ventilation, although this measurement is more explicit than lung
      function and BODE score, as they are impractical in these patients. Changes in ventilator
      settings caused by HFCWO are a concern when the patients receive both treatments
      simultaneously. The aim of this study was to investigate the effect of HFCWO on pneumonic
      subjects with acute respiratory failure receiving mechanical ventilation by evaluating
      immediate cardiopulmonary changes and changes in the initial ventilator settings.

      Methods

      The investigators conducted this comparative prospective randomized controlled single-blinded
      study at a university hospital. Adult subjects with pneumonia complicated with acute
      respiratory failure requiring endotracheal intubation and mechanical ventilation were
      consecutively recruited from a medical intensive care unit (ICU) (20-bed capacity). Pneumonia
      was defined as the presence of new or progressive pulmonary infiltrates and two of the
      following: body temperature > 38.3C or < 36C; white blood cell count > 12,000/mL or <
      4,000/mL; purulent tracheal secretions without other signs of infection requiring
      antimicrobial treatment. Acute respiratory failure was defined as a sudden decrease in PaO2 <
      60 mm Hg (or arterial oxyhemoglobin saturation < 90%) with or without PaCO2 > 45 mm Hg.17-19
      All of the patients had sufficient sputum production to require the physician to order airway
      secretion clearance. Disease severity was assessed by Acute Physiology and Chronic Health
      Evaluation (APACHE) II score. Adverse events were evaluated by the investigators and reported
      to the institutional review board. The exclusion criteria were pregnancy, pneumothorax,
      manifest hemoptysis, unstable hemodynamics, increased intracranial pressure, and those
      undergoing major cardiac, thoracic or abdominal surgery.

      All of the eligible patients had acute pneumonic respiratory failure and received
      endotracheal intubation and mechanical ventilation, and all signed informed consent forms.
      The patients were randomly allocated to the study group (HFCWO) or the control group (CCPT),
      as the efficacy of bronchial hygiene for both HFCWO and CCPT is comparable4. The primary
      investigators were blinded to which procedure the patients received. The local institutional
      review board of Chung Shan Medical University Hospital approved this study (No. CS13004). The
      experimental research was conducted in compliance with the Helsinki Declaration.

      To prevent vomiting during or after chest care, all of the subjects underwent the procedure
      one hour before or two hours after feeding via a nasogastric tube. Inhalation therapy was
      performed with an aerosolized solution of 6 mL of half saline via the ventilator before HFCWO
      or CCPT.

      HFCWO was performed using a VestTM Airway Clearance System Model 105 (Hill-Rom, St. Paul,
      Minnesota) connected to a vest via two flexible tubes by trained nurses who were blinded to
      the purpose of the study. All of the nurses had been well trained in how to perform both
      HFCWO and CCPT before the study, as these procedures are routinely performed by nurses at the
      investigators institution. HFCWO was applied to each subject at a frequency of 10-12 Hz and a
      pulse pressure setting of 1-2 selected from a scale ranging from 1 to 10 (arbitrary units)
      for 15 minutes. The patients receiving HFCWO were placed in a semi-upright sitting position,
      and the patients undergoing CCPT received cup-hand percussion with the hands positioned 3
      inches from the chest, striking the chest with a waving movement while they were placed in
      right and left decubitus positions for 5-10 minutes each1. Following HFCWO or CCPT, suction
      was performed immediately via an endotracheal tube.

      Changes to the initial ventilator settings during HFCWO were recorded by the trained nurses
      by checking the ventilator panel before and at 5, 10 and 15 minutes during HFCWO. The
      variables included peak airway pressure (Ppeak), positive-end expiratory pressure (PEEP),
      respiratory rate (RR), fraction of inspired oxygen (FIO2), inspiratory time, and sensitivity
      settings.

      Changes in the patients' cardiopulmonary responses were measured before and at 5, 10 and 15
      minutes during oscillation, and at 15 minutes after sputum suction. The measurement protocol
      for the CCPT group was the same as for the HFCWO group, except no measurements were taken at
      5 or 10 minutes during percussion because it was not possible for a single nurse to perform
      percussion and record measurements at the same time.

      Rapid shallow breathing index (RSBI) was calculated as follows:

      RSBI = breathing frequency (breaths/minute)/tidal volume (liters) (1) Oxyhemoglobin
      saturation was measured using a pulse oximeter (SPO2). Data were presented as mean ± standard
      deviation (SD) or median (interquartile range). For each outcome variable, comparisons were
      planned a priori. A paired t or unpaired t test was used for within-group or between-group
      comparisons. For non-normal data, the Mann-Whitney test was used. The chi-square test or
      Fisher's exact test was used to compare proportions of categorical variables between the two
      groups. A p value less than 0.05 was considered to be statistically significant. All
      statistical analyses were performed using SAS software version 9.3 (SAS Institute Inc., Cary,
      NC) and Microcal Origin version 4.0 (Northampton, MA, USA).
    

Intervention name(s): Vest Airway Clearance System Model 105; placebo intervention
Intervention type(s): Device; Device
Intervention description(s): HFCWO for 15 minutes then sputum suction.; CCPT for 15 minutes then sputum suction.
Other intervention name(s): HFCW oscillation; HFCWO; CCPT; CC physical therapy
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Supportive Care
Keywords: chest wall oscillation; acute respiratory failure; airway secretion