Home volume ventilator

Boitano LJ, Benditt JO. An evaluation of home volume ventilators that support open-circuit mouthpiece ventilation. Respir Care 2005 50 1457-1461. 

Prior to cuff deflation it is preferable to switch to a home volume ventilator set for patient s comfort and adequate minute ventilation, with note taken of the peak airway pressure (Paw) Suctioning through the mouth and through the tracheostomy is necessary. With the cuff deflated, brief suctioning or use of the MIE may also be necessary. The Paw falls as the cuff is deflated, so the delivered volume should be increased to reach the previously observed Paw- Respiratory rate may need to be increased temporarily to improve patient comfort. Glottic function may require a few days to recover. Sa02 should be maintained at >90%. 

Most ventilators measure flow volume and pressure as these variables are needed as feedback mechanisms to operate the ventilator. In home care ventilators, these measured variables are not always used to provide sophisticated real-time monitoring. However, with increased data management capabilities, these measures can now be recorded in home care ventilators over a significant period of time with relative ease and little cost. The challenge is to provide this information in a format that can be easily interpreted by the clinician for review. Some examples can be seen in Figures 8 to 10. This is a new science and we are just beginning to learn how to interpret and use this information. Manufacturers are challenged to develop... 

Bi-level NIV may be used as a first-line treatment, with supplemental oxygen (27). Expiratory airway pressure is titrated to control h5q)opneas and apneas, and inspiratory airway pressure is added to control Paco2. If bi-level NIV fails, nasal volume ventilation may be used (29). In many patients with OHS and predominant OSA, once hypercapnia has improved (which may take several weeks) nCPAP may be used (29). Thirteen obese patients (n = 13) with a BMI > 35, aged 28-69 years with severe OSAS and hypercapnia (8.2 0.3 kPa) and failing to respond to initial CPAP therapy, were treated via a nasal nocturnal volume-cycled ventilator, which was tolerated by all patients. Significant improvements in daytime arterial blood gas levels were obtained after 7 to 18 days of nasal intermittent positive pressure ventilation (29) in 10 of the 13 patients three months later, 12 of the 13 patients could be converted to nCPAP therapy and one patient remained on NIV. In another study (37), the same results were observed after three months of home nocturnal bi-level NIV in seven patients, three of whom had severe obesity. 

New carpeting is installed in a home. The carpet outgasses formaldehyde at a total rate of 2.3 g/hr and the house has a ventilation rate of 0.3 ACH. If the house has a volume of 750 m3, what is the expected formaldehyde concentration If the carpet were taken outdoors, how long would it take for the formaldehyde concentration in the home to decrease to 0.1 ppm ... 

When providing support, a ventilator can control four primary variables during inspiration pressure, volume, flow, and time. If a ventilator controls a given variable, then the waveform of this variable during inspiration will ideally remain unchanged from breath to breath regardless of how the load (compliance and resistance) changes (1). Most modem home ventilators are either pressure or flow controllers. 

Figure 4 Improvement of ABG in different etiologies of CRF receiving long-term home ventilation. Abbreviations ABG, aiterial blood gas volume CRF, chronic respiratory failure. Source From Ref. 9.

Meanwhile, years of productive research have demonstrated that patients with chronic respiratory insufficiency can also benefit from mechanical ventilation. As the Preface of this volume mentions their survival as well as their health status may be dependent on long-term ventilatory support. The ever increasing incidence and prevalence of chronic respiratory disease suggests that the use of ventilatory support will markedly increase. However, the techniques and strategies to use it, and when and where (non-intensive care unit, or home), are very different from treating the respiratory failure resulting from acute conditions and in patients with structurally near normal lungs. 

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