Use of Non-Invasive Ventilation in General Ward for the Treatment of Respiratory Failure
Sadeka Tamanna, MD, MPH and M. Iftekhar Ullah, MD, MPH

Introduction
Non-invasive ventilation (NIV), the provision of ventilatory assistance without an artificial airway, has emerged as an important ventilatory modality over the last 20 years. Delivery of pressured air at a certain level through a nasal or oro-nasal mask improves oxygenation and reduces ventilatory muscle fatigue. The equipment consists of a ventilator (typically a CPAP or BiPAP machine) with tubing, headgear, nasal or facial mask, filter and humidifier (Figure 1). In this article, we will discuss the medical literatures that support the use of NIV safely and effectively on the general medical floor to treat respiratory failure secondary to acute exacerbation of chronic obstructive pulmonary disease (COPD) and congestive heart failure (CHF).

Background
Continuous positive pressure ventilation (CPAP) and bi-level positive pressure ventilation (BiPAP) are the two major types of NIV in clinical use. Obstructive sleep apnea and respiratory difficulty from neuromuscular diseases were the primary indications for NIV when it was first introduced in early 1980’s. NIV was used to treat acute respiratory failure to avoid risks of intubation in the mid-nineties. Many applications of NIV have been tried in critical care settings while only four of them have been recommended after multiple randomized controlled trials (RCTs). Those four indications include acute exacerbation of chronic obstructive pulmonary disease (COPD), cardiogenic pulmonary edema, facilitation of extubation in COPD patients and immune-compromised patients who are at higher risk of complication from intubation.¹

Patients with respiratory failure either from COPD or congestive heart failure (CHF) exacerbation, are admitted frequently in every hospital. While NIV is already used in the ICU to treat the above cases helping to reduce intubation and long term hospital stays, not all of these patients meet the criteria for entry into the ICU on the first day of admission. Mild to moderate cases of respiratory failure that decompensate over hours to days despite optimal medical management on the medical floor need to be evaluated for transfer to the ICU or get intubated on the floor after sudden deterioration, only to be sent to ICU. The medical literature now supports the early use of NIV for certain patients on the general medical ward to prevent intubation and decrease mortality. The opportunity for a successful intervention may be lost if delay arises in initiating NIV, allowing the underlying disease to progress too far.²

NIV in Acute Exacerbation of COPD
COPD carries a tremendous financial, medical and psychological burden on society. Acute COPD exacerbations are responsible for more than 500,000 hospitalizations per year in the United States, and 6% to 34% of them die.³ Adding non- invasive ventilation to conventional therapy of COPD showed promising results. Bott et al. first published results of an RCT comparing conventional treatment and conventional treatment plus NIV for acute exacerbation of COPD. NIV was shown to improve the pH significantly in such patients (p<0.001) and caused steady gradual fall in pCO2 (p<0.001) compared to the control group.⁴

Patients with acute respiratory failure eventually develop inspiratory muscle fatigue and mere increase in the respiratory rate does not fully compensate for the ventilatory insufficiency. NIV provides a larger tidal volume with the same inspiratory effort helping to improve alveolar ventilation. ⁵ It also decreases the work of breathing by partially overcoming the auto-PEEP (positive end expiratory pressure) in certain situations. An auto PEEP is the abnormal residual pressure greater than the atmospheric pressure remaining in the alveoli at the end of exhalation due to air trapping in severe COPD. Improvement of gas exchange by improving alveolar ventilation lowers mortality, decreases the length of hospital stay and need for critical care admission and thus lowers the overall hospital cost.

Plant and colleagues randomized two groups of patients to NIV (BiPAP with face mask) and standard treatment for COPD exacerbation in the general ward. In this study, NIV has been shown to decrease the mortality and need for intubation significantly. PH, respiratory rate and PCO2 also improved significantly in the NIV group. ² In another systematic review of randomized controlled trials that compared NIV and usual medical care in patients admitted to the hospital with respiratory failure resulting from COPD exacerbation demonstrated a lower mortality (RR 0.41, 95% CI 0.26-0.64), a lower need for intubation (RR 0.42, 95% CI 0.31-0.59), a lower likelihood of treatment failure (RR 0.51, 95% CI 0.38%-0.67%) and greater improvements at 1 hour of PH, PaCO2 and respiratory rate. The average length of hospital stay for COPD exacerbation with op- timal medical treatment is usually 6-7 days.6 Use of NIV has been found to shorten the hospital stay (mean 3.24 days, 95% CI 4.42-2.06) and decrease complications associated with treatment (RR 0.32, 95% CI 0.18-0.56).⁷ This may translate into reducing the financial burden significantly on hospitals and patients as well. These findings have been further supported by a meta analysis of 15 RCTs comparing the addition of NIV to standard therapy alone for acute COPD exacerbation, showing a decrease in the rate of endotracheal intubation (RR 28%, 95% CI 15-40%), length of hospital stay (absolute reduction 4.57 days, 95% CI 2.3-6.83), and hospital mortality rate (RR 10%, 95% CI 5-15%).⁸

NIV in Acute Exacerbation of CHF
Heart failure affects 5 to 6 million North Americans each year and continues to be associated with repeated hospitalizations, high morbidity and mortality. The average length of hospital stay for patients with heart failure was found to be about 5.9 days.⁹ An RCT comparing oxygen, CPAP and Bi- PAP in patients with acute cardiogenic pulmonary edema found a significant reduction in the need of intubation in NIV group (p=0.001). 10 Up to 51% of patients with CHF have been found to have sleep-related periodic breathing disorders. 11 It is well known that CPAP improves arterial oxygenation and decreases left ventricular after-load, as well as the work of breathing in patients with acute cardiogenic pulmonary edema. CPAP has shown to improve the morbidity, mortality and left ventricular ejection fraction among patients with heart failure and sleep disorder. According to the European Cardiology Task Force, non-invasive ventilation and CPAP are regarded as first line treatments together with standard medical therapy when respiratory failure ensues from cardiogenic pulmonary edema.

Oxygen masks are primarily used for the treatment of hypoxemia in heart failure. Two randomized controlled trials showed that CPAP use may cause significant improvement in PaO2 and stroke volume index while decreasing intrapulmonary shunt and alveolar arterial oxygen gradient in acute cardiogenic pulmonary edema compared to the treatment with oxygen only. ^{12, 13} CPAP has been recommended as the initial noninvasive treatment of choice due to its greater simplicity and lesser ex- pense.^{12, 14} NIV induces a more rapid improvement in respiratory distress and metabolic disturbance than does standard oxygen therapy but had no effect on short term mortality. ¹³

Despite the benefits and approved guidelines, the utilization of NIV is still not adequate. In a survey in the Massachusetts and Rhode Island area in 2006, it was found that only 33% of patients with COPD and heart failure, who may have been candidates for NIV, were actually receiving it.¹⁵ Potential reasons for lower utilization include lack of awareness among physicians about its indication and efficacy, lack of sufficiently trained respiratory therapists, and lack of sufficient equipment in the hospital.

Who is A Candidate for NIV in the General Ward?
Patients with mild respiratory acidosis (pH as low as 7.30) and mild to moderate respiratory distress caused by an acute COPD exacerbation or hypoxemia from heart failure are the ones that benefit most from non-invasive ventilation. Hemodynamically stable patients with mild to moderate COPD exacerbation (pH ≥ 7.30) and cardiogenic pulmonary edema with hypoxemia can be treated safely and effectively in the general ward if the hospital physicians and the staff have appropriate expertise.^{2, 16} Very recently, the Canadian Medical Association has published clinical practice guidelines after reviewing 3033 studies and 146 RCTs and recommended NIV for severe COPD exacerbation and cardiogenic pulmonary edema (in the absence of shock or acute coronary syndrome requiring urgent coronary revascularization).¹⁷ The need for sedation in NIV is minimal or none compared to intubation, and thus the patients can maintain spontaneous breathing and can be weaned off more easily. However, it should be avoided in patients with contraindications (see table 1). Those patients should be treated in the intensive care unit with prompt intubation as soon as possible.


Risk of NIV Use on the General Medical Floor
Despite numerous benefits of NIV, it is not without risks. Patients may start to deteriorate while on NIV, and they may go unnoticed by the ward staff, thinking that they are being safely managed by NIV. To avoid that, a formal protocol of monitoring respiratory rate, hypoxemia and blood gases for these patients must be in place. Table 1 describes the potential risks associated with NIV, along with its indications and contraindications.

Conclusion
On the basis of controlled trials, NIV is now considered as a safe and effective therapy to treat patients with respiratory failure from COPD or congestive heart failure on the general medical floor outside intensive care units. If used early during hospitalization, it helps prevent intubation, reduce mortality and decrease the length of stay in the hospital. However, it should be done in a closely monitored setting by trained physician and personnel following an appropriate treatment protocol to avoid potential complications.

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