Bi-PAP, Nasal Ventilation, and Body Ventilators

Abstract

To the Editor: We read with interest the article by Sanders and Kern in which the use of bi-level positive airway pressure (Bi-PAP) was studied in the treatment of sleep apnea.1Sanders MH Kern N Obstructive sleep apnea treated by independently adjusted inspiratory and expiratory positive airway pressures via nasal mask: physiologic and clinical implications..Chest. 1990; 98: 317-324Abstract Full Text Full Text PDF PubMed Scopus (259) Google Scholar They noted difficulty in raising inspiratory positive airway pressure (IPAP) over 15 cm H2O because of mask leaks. Another recent publication reported nasal bridge soft-tissue breakdown resulting from continuous positive airway pressure (CPAP).2Steljes DG Kryger MH Kirk BS Millar TW Sleep in postpolio syndrome..Chest. 1990; 98: 133-140Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar The widely acknowledged intolerance of CPAP by approximately 30 percent of patients is at least in part due to leak and discomfort from the CPAP mask. Newer CPAP masks (Adam, Puritan-Bennett, Boulder, Colo) are generally more comfortable and better tolerated at IPAP pressures up to 20 cm H2O, at which point they too may leak or pinch the nostrils. It is important to call attention to the fact that custom-molded nasal interfaces have been used for the delivery of nasal intermittent positive pressure ventilation (IPPV) for the past six years.3Bach JR Alba AS Mosher R Delaubier A Intermittent positive pressure ventilation via nasal access in the management of respiratory insufficiency..Chest. 1987; 92: 168-170Crossref PubMed Scopus (128) Google Scholar,4McDermott I Bach JR Parker C Sortor S Custom-fabricated interfaces for non-invasive intermittent positive pressure ventilation..Int J Prosthodontics. 1989; 2: 224-233PubMed Google Scholar Similar interfaces are now commercially available (SEFAM mask, Lifecare, Lafayette, Colo). These interfaces are effective and convenient for the entire continuum of CPAP, Bi-PAP, and nasal IPPV at considerably greater pressures than their generic counterparts are. Sanders and Kern also noted that nonapneic oxyhemoglobin desaturation could be prevented by raising IPAP alone and cited several mechanisms to explain this, including the effect of reversing airway narrowing and reversal of CPAP-induced depression of cardiac output. The ability of their patients to adequately ventilate themselves, however, was not established. We have observed that ventilatory assistance or support is a direct fonction of the difference between the IPAP and the expiratory positive airway pressure (EPAP). Thus, the normalization of SaO2 is at least in part due to correction of Pco2. As the IPAP-EPAP difference approaches 18 to 25 cm H2O, the technique becomes the equivalent of nasal IPPV The effect of the IPAP-EPAP difference of nasal IPPV in supporting ventilation during sleep is observed most dramatically in patients with little or no measurable vital capacity.5Bach JR Alba AS Management of chronic alveolar hypoventilation by nasal ventilation..Chest. 1990; 97: 52-57Abstract Full Text Full Text PDF PubMed Scopus (236) Google Scholar It is of concern to see articles devoted to the management of chronic hypoventilation6Strumpf DA Millman RP Hill NS The management of chronic hypoventilation..Chest. 1990; 98: 474-480Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar in which the use of negative-pressure body ventilators is still being encouraged and the effectiveness and convenience of mouth and nasal IPPV is regarded with skepticism, as evidenced by such statements as “This technique has not been fully evaluated nor has its efficacy been definitely demonstrated.” We have managed over 200 patients on 24-h ventilatory support without tracheostomies by using either nasal or mouth IPPV7Bach JR Alba AS Bohatiuk G Saporito L Lee M Mouth intermittent positive pressure ventilation in the management of postpolio respiratory insufficiency..Chest. 1987; 91: 859-864Crossref PubMed Scopus (113) Google Scholar,8Bach JR O'Brien J Krotenberg R Alba AS Management of end stage respiratory failure in Duchenne muscular dystrophy..Muscle Nerve. 1987; 10: 177-182Crossref PubMed Scopus (102) Google Scholar for nocturnal support. Many switched to these techniques from body ventilators because of the sleep apneas and inconvenience associated with body ventilator use. Although there have been many recent reports exploring the use of nasal IPPV, we find that mouth IPPV is at least as effective and is preferred by many patients. We encourage other investigators to explore these techniques.