Aspects pratiques et techniques de la ventilation non invasive

[Home non-invasive ventilation for chronic obstructive pulmonary disease]

INTRODUCTION

The benefits of long-term non-invasive ventilation (NIV) in the management of chronic obstructive pulmonary disease (COPD) patients remain controversial.

AIM

To analyze the characteristics of COPD patients under home NIV and to evaluate its impact among this population.

METHODS

We carried out a retrospective study between January 2002 and April 2016 of COPD patients under long-term NIV at "la Rabta" and the Military Hospital.

RESULTS

There were 27 patients with an average age of 64 and a sex ratio (M/F) of 0.92. Active smoking was reported in 96.3%. A persistent hypercapnia following an acute exacerbation of COPD with failure to wean the NIV was the main indication of long-term NIV. We noted a reduction in hospital admissions in the first year of 60% and in intensive care of 83.3% (P<10^-3). There was no non-significant decrease of PaCO₂ (4.5mmHg). There was no modification in FEV 1 and in FVC (P>0.05). The survival rate was 96.3% at 1 year, 83.3% at 2 years and a median survival of 24 months.

CONCLUSIONS

Our study suggests that home NIV contributes to the stabilization of some COPD patients by reducing the hospitalizations rates for exacerbation. More prospective studies are needed to better assess the impact of NIV on survival and quality of life and to better define the COPD patients who require NIV.

[Ventilator modes and settings during non-invasive ventilation: effects on respiratory events and implications for their identification. 2011]

Compared with invasive ventilation, non-invasive ventilation (NIV) has two unique characteristics: its non-hermetic nature and the fact that the ventilator-lung assembly cannot be considered as a single-compartment model because of the presence of variable resistance represented by the upper airways. When NIV is initiated, the ventilator settings are determined empirically based on clinical evaluation and blood gas variations. However, NIV is predominantly applied during sleep. Consequently, to assess overnight patient-machine "agreement" and efficacy of ventilation, more specific and sophisticated monitoring is needed. The effectiveness of NIV might therefore be more correctly assessed by sleep studies than by daytime assessment. The simplest monitoring can be done from flow and pressure curves from the mask or the ventilator circuit. Examination of these tracings can give useful information to evaluate if the settings chosen by the operator were the right ones for that patient. However, as NIV allows a large range of ventilatory parameters and settings, it is mandatory to have information about this to better understand patient-ventilator interaction. Ventilatory modality, mode of triggering, pressurization slope, use or not of positive end expiratory pressure and type of exhalation as well as ventilator performances may all have physiological consequences. Leaks and upper airway resistance variations may, in turn, modify these patterns. This article discusses the equipment available for NIV, analyses the effect of different ventilator modes and settings and of exhalation and connecting circuits on ventilatory traces and gives the background necessary to understand their impact on nocturnal monitoring of NIV.

[Acute exacerbations of chronic obstructive pulmonary disease]

Acute exacerbation of chronic obstructive pulmonary disease (COPD) is defined by modification of the usual COPD symptoms, dyspnea, coughing and sputum, beyond daily variations, with a sudden onset, and requiring modification of the usual treatment. Exacerbations stud the course of COPD. Their frequency is variable, averaging 1-2 per year. Their frequency generally increases with COPD severity. Exacerbations impair patients' quality of life and aggravate disease prognosis by accelerating the decline in FEV1, the primary indicator of respiratory function. The most frequent causes of exacerbations are viral and bacterial respiratory infections and pollution. No cause is identified for nearly one third of all exacerbations. Most exacerbations can be treated at home, if a careful search for signs of clinical severity is negative. Treatment combines inhaled bronchodilator agents (beta-2 agonists, combined if necessary with anticholinergics) and oral corticosteroid therapy (prednisone: 0.5 mg/kg/d for 1 week) when the COPD is severe or signs of severity accompany the exacerbation. Antibiotic therapy is justified when the sputum appears purulent. Severe exacerbation may require oxygen therapy in cases of severe hypoxemia (PaO(2)<60 mm Hg) or mechanically assisted ventilation, essentially by noninvasive ventilation in cases of respiratory acidosis (pH<7.35). Noninvasive ventilation improves dyspnea and respiratory acidosis, diminishes respiratory frequency, intubation, duration of hospitalization, nosocomial infections, and mortality. Pulmonary follow-up is necessary after an exacerbation, especially to prevent the recurrence of exacerbations by measures that have been demonstrated to be effective, including help in smoking cessation, adaptation of COPD treatment, vaccination against influenza and pneumonia (pneumococci), and respiratory rehabilitation. Early diagnosis and rapid treatment of exacerbations can limit their impact, improve quality of life, and reduce the risk of hospitalization.

[Domiciliary ventilation in patients with COPD]

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) has become one of the main indications for domiciliary ventilation, which is usually non-invasive (NIV). This review focuses on the pathophysiology processes and clinical trial data that underlie current guidelines from international societies.

STATE OF THE ART

To date most published studies about domiciliary ventilation in COPD have been short-term and their message is complicated by the presence of significant methodological problems. The two controlled studies of > or =12 months-duration both found that survival was not improved by long-term NIV. Domiciliary ventilation may be considered when long-term oxygen therapy is unsuccessful and when failed with a progressive deterioration in clinical respiratory status with recurrent episodes of acute hypercapnic respiratory failure. A diurnal PaCO(2) > or =55 mmHg (7.3 kPa) is a necessary but not sufficient condition to consider domiciliary ventilation.

CONCLUSION

Domiciliary ventilation should only be initiated in selected patients on the basis of clinical symptoms and exacerbation frequency. Until further characterization of patients who are likely to respond, the response to treatment should be assessed regularly.

Is disinfection of mechanical ventilation tubing needed at home?

INTRODUCTION

Home mechanical ventilation is used to treat chronic alveolar hypoventilation. Maintenance protocols for home ventilation circuits (HVC) remain empirical and unproven. We have investigated (1) the cleanliness and sterility of the HVC used by home ventilated patients and (2) the efficiency of tubing cleaning and decontamination protocols recommended to them and used for 12 months or more.

METHOD

HVC cleanliness was assessed in 39 severe restrictive ventilated patients (16 (T) tracheostomy vs. 23 (N) noninvasive) and in 7 new valves as control. In the first experiment (Exp1), a visual and bacteriologic inspection of the expiratory valve (Eva) was conducted during a consultation in our centre. Eva visual cleanliness was assessed on a 10-point scale and Eva bacteriologic contamination analysis was performed on a dry smear. In the second experiment (Exp2), these analyses were repeated after a cleaning sequence chosen at random, either chemical (ammonium-chlorhexidine complex) (A) or mechanical by dishwasher (B).

RESULTS

In Exp1, 69% of Eva were dirty. Dirtiness was worse in (T) than in (N) (5.3 vs. 2; p<0.001). There was a significant positive correlation between visual cleanliness and bacteriologic contamination (r=0.56; p<0.001). Eva in group (T) were more contaminated than in group (N) (p<0.001). Eva contamination rates reached 22% in group (N) but without the presence of any potentially pathogenic organisms (PPO) and 81% in group (T) where 19% were PPO. In Exp2, EVA visual cleanliness was better after dishwasher cleaning (B) compared to chemical (A) (0.16 vs. 1.05; p<0.001) with similar bacteriological decontamination.

CONCLUSION

HVC from noninvasive ventilated patients are dirty but not contaminated by PPO. We recommend washing them in a dishwasher or with detergent and hot water without specific disinfection. PPO contaminated 1/5 of invasive HVC, for which we recommend dishwasher cleaning. Decontamination is only indicated when tubing is visually very dirty or/and when tracheostomized patients are particularly sensitive to respiratory tract infections. The expiratory valve must be carefully washed specifically, with care that its balloon is not placed under water.