NPPV

Here’s Dr. Carmelli with today’s Morning Report!

Noninvasive positive pressure ventilation (NPPV)

Definition -NPPV refers to positive pressure ventilation delivered through a noninvasive interface (nasal mask, facemask, or nasal plugs), rather than an invasive interface (endotracheal tube, tracheostomy).

Indications:
- Younger age
- Lower acuity of illness (APACHE score)
- Able to cooperate, better neurologic score
- Less air leaking, intact dentition
- Moderate hypercarbia (PaCO2 >45 mmHG, <92 mmHG)
- Moderate acidemia (pH <7.35, >7.10)
- Improvements in gas exchange and heart respiratory rates within first two hours
Contraindications
- The need for urgent Endotracheal Intubation
- Cardiac or respiratory arrest
- inability to cooperate, protect the airway, or clear secretions
- Severely impaired consciousness
- Nonrespiratory organ failure
- Facial surgery, trauma, or deformity
- High aspiration risk
- Prolonged duration of mechanical ventilation anticipated
- Recent esophageal anastomosis
Pre-intubation
- Patients with hypoxemic respiratory failure are typically preoxygenated with 100 percent oxygen prior to the initiation of conventional mechanical ventilation, in order to prevent arterial oxygen desaturation during intubation.
- A randomized trial (baillard et al in 2005)- compared standard preoxygenation (with a bag mask valve) to preoxygenation with NPPV
  - The NPPV group had fewer oxyhemoglobin desaturations during intubation
  - higher oxyhemoglobin saturation at the end of preoxygenation, during intubation, and five minutes after intubation.
- COPD
  - Physiology
    - NPPV enhances ventilation by unloading fatigued ventilatory muscles, thus leading to:
  - a decreased respiratory rate, an increased tidal volume, and an increased minute ventilation
    - Overall, the improvement in respiratory blood gases during NIPPV is essentially due to higher alveolar ventilation and not to improvement in VA/Q^· relationships.
    - So, NPPV helps achieve an efficient breathing pattern rather than high inspiratory pressures
  - Severe COPD/ COPD complicated by hypercapnic acidosis.
    - Meta-analysis (14 randomized trials, 758 patients) that compared standard therapy alone to NPPV plus standard therapy in patients having a COPD exacerbation complicated by hypercapnia (PaCO2 >45 mmHg).
      - NPPV decreased mortality (11 versus 21 percent),
      - dec intubation rate (16 versus 33 percent),
      - dec treatment failure (20 versus 42 percent).
      - dec Hospital length of stay and complications
      - Patients with severe exacerbations of COPD respond better to NPPV than patients with mild COPD exacerbations
        
        A meta-analysis by Keenan et al in 2003 (15 randomized trials) found that NPPV improved clinical outcomes only in those randomized trials that enrolled patients with severe COPD exacerbations (defined as a baseline pH <7.3 or a control group mortality >10 percent) and not in those trials that enrolled patients with milder COPD exacerbations
        
        cochrane review in 2004- NPPV resulted in
        
        decreased mortality (Relative Risk 0.52; 95%CI 0.35 to 0.76),
        
        decreased need for intubation (RR 0.41; 95%CI 0.33 to 0.53),
        
        reduction in treatment failure (RR 0.48; 95%CI 0.37 to 0.63),
        
        rapid improvement within the first hour in pH (Weight Mean Difference 0.03; 95%CI 0.02 to 0.04),
        
        dec complications associated with Tx (RR 0.38; 95%CI 0.24 to 0.60)
        
        dec length of hospital stay (WMD -3.24 days; 95%CI -4.42 to -2.06)

Cardiogenic pulmonary edema
- Physiology
  - Improves respiratory parameters (eg, heart rate, dyspnea, hypercapnia, acidosis) in patients with cardiogenic pulmonary edema
  - particularly beneficial to patients with hypercarbia
  - It also accelerates the improvement in Pa_O2/FI_O2, Pa_CO2,

BIPAP vs CPAP
- META ANALYSIS (Ho et al, 2006)- CPAP vs BIPAP in cardiogenic pulm edema. No difference in mortality or risk of intubation.
- Meta-analysis (Peter et al, 2006)- CPAP vs BIPAP vs standard therapy. CPAP/BIPAP reduce intubations, CPAP reduces mortality, BIPAP trended toward reduced mortality.
- Mortality (There is conflicting evidence regarding the impact of NPPV on mortality)
  - A 2010 meta-analysis (Weng et al) of 13 trials (1369 patients) found that patients who received CPAP plus standard care (eg oxygen, diuresis) had a lower hospital mortality than those who received standard care alone (10.3 versus 15.8 percent, RR 0.64, 95% CI 0.44-0.92)- especially if MI was the underlying cause.
  - However, analysis of the 9 randomized trials (1091 patients) that studied BPAP reported that, compared with standard care alone, BPAP was associated with a trend towards improved mortality that did not reach statistical significance (9.6 versus 11.9 percent, RR 0.82, 95% CI 0.58-1.15)
  - A 2013 meta-analysis of 32 studies (2916 patients), that included both modalities of NPPV (CPAP and BPAP) in the analysis, reported that, compared with standard medical care, NPPV significantly reduced hospital mortality in patients with cardiogenic pulmonary edema (RR 0.66, 95% CI 0.48 to 0.89) [78].
- An important limitation of these meta-analyses is that the evidence is derived from numerous small trials. Large-scale trials are needed to examine the effect of NPPV on mortality in patients with cardiogenic pulmonary edema.
- Intubation
  - Many trials show a reduce in the intubation rate in the subgroup of hypercapnic patients.
Hypoxemic respiratory failure
- There is conflicting evidence about whether NPPV is advantageous in patients with hypoxemic respiratory failure:
- Cons
  - some observational studies in the past have shown high rates of intubation (60%) and in hospital mortality (64%), that lead some to wonder if NPPV is preventing anything in this high mortality disease process
  - Pros (however many are showing support)
  - a meta-analysis (8 randomized trials, 461 patients) compared standard medical therapy alone to standard medical therapy plus NPPV in patients with hypoxemic respiratory failure due to causes other than cardiogenic pulmonary edema
    - NPPV reduced ICU mortality (17 percent absolute risk reduction)
    - dec intubation rate (23 percent absolute risk reduction),
    - dec ICU length of stay (2 day absolute reduction)
    - systemic review (Keenan et al in 2004) of RCTs of BIPAP for hypoxemic resp failure-
      - 8 RCTs showed reduced intubation by 23%,
      - 7 RCTs showed reduced length in ICU by 1.9 days.
      - 3 RCTs showed reduced hospital stay by 2.8 days.
      - 8 RCTs showed reduced ICU mortality by 17%,
      - but no RCTs showed reduced hospital mortality (so more sick pt’s).
    - RCT (Ferrer et al 2003)-
      - The use of noninvasive ventilation prevented intubation, reduced the incidence of septic shock, and improved survival in these patients compared with high-concentra- tion oxygen therapy.

Pneumonia
- Cochran review 2012- NIV can reduce ICU mortality, dec intubation, shorten ICU stay
- in several randomized trials of pneumonia, resf failure 2/2 pna, or pan with immunocompromise
  - NPPV decreased ICU mortality (18 versus 39 percent)
  - dec intubation rate (25 versus 52 percent).
  - These effects were particularly strong in the subgroup of patients with hypoxemic respiratory failure due to pneumonia.
Asthma
- Physiology
  - NPPV has been postulated to have a direct bronchodilating effect and improve alveolar recruitment.
  - The bronchodilatory effect has been found to be independent of drug dispersion. This is thought to be due to the effect of external PEEP off-setting intrinsic PEEP that builds up during an asthma attack
- Poor evidence
  - Small randomized trials and one meta-analysis of these trials have not documented a clear benefit but have been limited by small numbers and methodological design flaws
  - Cochrane review- 2012- The paucity of data that exist to support the use of NPPV in patients in status asthmaticus. As such this course of treatment remains controversial despite its continued use in current clinical practice. Larger, prospective randomised controlled trials of rigorous methodological design are needed to determine the role of NPPV in patients with asthma.
  - RCT (soroksky et al in 2003)- 30 patients who presented to the emergency department with a severe asthma exacerbation that was not responding to inhaled bronchodilator therapy.
    - Patients were randomly assigned to receive NPPV (in the bilevel positive airway pressure [BPAP] mode) or sham (subtherapeutic BPAP). results:
    - dec rate of hospitalization (18 versus 63 percent)
    - increased lung function (80 versus 20 percent predicted forced expiratory volume in one second [FEV1]).
  - In the absence of conclusive data, a short trial of NPPV (eg, one to two hours) is appropriate in this population, particularly for those failing medical therapy.
  - Prolonged trials of NPPV are not warranted and should not delay mechanical ventilation when it is indicated. (See ”.)