Keywords

1 Introduction

Viruses are an age-old foe of humans and have caused great loss of life on a global scale. For example, the “Spanish flu” outbreak (1918–1919) caused 50 million deaths worldwide [1]. RNA viruses of the Family Orthomyxoviridae [2]—including the influenza A(H1N1) virus—have caused many epidemics. The virus undergoes constant genetic changes and gave rise to the new H1N1 (swine flu or type A influenza), which started the pandemic that began in Mexico in 2009.

A published series [3–7] showed that patients admitted to the intensive care unit (ICU) developed multi-organ failure, especially hypoxemia-induced acute respiratory failure (ARF). Mortality in this series ranged from 17 to 40 %. Ventilation was required in 64–100 % of the patients admitted to the ICU [3–8], whether due to hypoxemia symptoms such as adult respiratory distress syndrome (ARDS) or to exacerbation of chronic pathologies such as cardiac failure or chronic obstructive pulmonary disease (COPD), which are often accompanied by hypercapnia. The need for invasive mechanical ventilation (IMV) was considered to be one of the factors linked to hospital mortality [6]. With regard to the kind of ventilation used, this varied depending on the series [3–5, 7, 8], although IMV was more commonly used than noninvasive ventilation (NIV). Also, there was a high failure rate (>70 %) in the case of NIV (Table 14.1). Given the low success rate of NIV [3], the controversial indications for using it in hypoxemic patients, and the risk of facilitating aerosol-borne spread of the virus and thus the danger to health care personnel, in 2009 scientific societies [9] made various recommendations concerning its use. One was that NIV was best applied: (1) in patients with hypercapnia-exacerbated COPD; (2) in patients whose heart diseases were accompanied by acute pulmonary edema; (3) to prevent postextubation failure. In the case of patients with acute hypoxemia and the associated risk of organ failure, prolonged NIV treatment may lead to risky intubation. Accordingly, NIV should not be used as a matter of course.

Table 14.1 Outcomes of various ventilation systems and mortality rates in several series
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Our experience [10] produced results that differed from those in previously published studies on the use of NIV. Ten patients (2009–2010) were entered in the national register of virus influenza A(H1N1) of the Infectious Diseases Work Group of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units. Seven of these patients displayed primary viral pneumonia (Table 14.2). Most of the patients were young and otherwise healthy, but excess weight (40 %) and pregnancy (two patients) were notable factors. Seven patients (7/10, 70 %) underwent NIV. Two patients were intubated on admission, and one did not require mechanical ventilation. Overall mortality was 10 % (one patient). This patient had been transferred from another hospital with multi-organ failure and died 24 h after admission. A group of five patients with hypoxemia were analyzed (Table 14.2) especially in connection with radiological signs of hypoxemia and liver failure. All patients were treated with NIV and continuous positive airway pressure (CPAP). Orotracheal intubation was not required in any cases, and no patients died in the ICU or during the hospital stay (Tables 14.1 and 14.2). The mean interval from the onset of symptoms to ICU or hospital admission was 5 days.

Table 14.2 Baseline characteristics of comorbidity, pulmonary disease, laboratory and outcomes of patients admitted to the ICU
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Our tentative explanations for these highly satisfactory results are (1) the virtual absence of co-morbidity in a relatively young group of patients whose only adverse factors were excess weight and pregnancy (according to most series) [5–8]; (2) a low organ-failure score on the Sepsis-Related Organ Failure Assessment (SOFA) scale—on which hypoxemic respiratory failure was the most salient problem—compared with the scores in other series [3–5, 7]; (3) the heightened awareness of health personnel, who had received health-authority guidelines to the effect that patients with pulmonary infiltrates and significant hypoxemia were to be admitted to the ICU straightaway to receive assisted ventilation. That is why our intervals to ICU admission are similar or lower than those in previously published studies [3, 4, 7] given that, with one exception, the patients were not placed in wards first. Similar to our results, the Argentina series [8] showed that 64 patients were treated with NIV to good effect. In that case, NIV boosted patient survival (24 % vs. 13 %, p = 0.02). These data support the idea that greater use of NIV might have reduced the need for IMV and quite possibly the mortality rate, but this is of course no more than a supposition.

There are considerable disparities in the way NIV is used, but the published series [3–7] show a high failure rate. By contrast, our results [10] showed successful NIV-based treatment. We therefore recommend early NIV/CPAP treatment for at least a few hours in young patients with pneumonia-induced hypoxemia caused by type A influenza and where no organ failure is apparent on the SOFA scale. This does not mean that NIV is an alternative to IMV but, rather, that clinically well-placed patients may benefit from NIV for treating ARF. If there is no improvement or the patient suffers from organ dysfunction, it is best to proceed with orotracheal intubation to prevent death—a course of action recommended in one series [5], where there was a higher mortality rate among patients in which NIV failed than among those who had been intubated from the outset.

Key Recommendations

  • Patients affected by virus influenza A(H1N1) and displaying multi-organ failure (respiratory, renal, hemodynamic, hepatic) should be admitted to the ICU.

  • Most patients with pulmonary infiltrates and ARF should undergo mechanical ventilation in an ICU, with the option of round-the-clock invasive or noninvasive assisted ventilation.

  • Invasive mechanical ventilation is “the gold standard” for treating ARF.

  • Early application of NIV can be recommended for young patients with organ failure as measured by the SOFA scale where hypoxemic ARF is the main problem.