n addition to smoking, there are many other conditions associated with rhinosinusitis. These include allergic rhinitis, asthma, nasal polyps, aspirin hypersensitivity, cystic fibrosis, and immune deficiency (particularly immunodeficiency virus (HIV) infection).

The occurrence of secondary bacterial sinusitis is highly associated with prior viral respiratory illnesses. An important area of disease leading to secondary bacterial sinusitis is obstruction at the ostiomeatal complex. A variety of factors may lead to obstruction of the ostium.

The most common predisposing factor is viral infection, which causes edema and inflammation of the nasal mucosa. In addition to viral rhinosinusitisrelated cases, acute bacterial sinusitis occurs related to allergy and nasal obstruction due to polyps, foreign bodies, and tumors.

Less common risk factors associated with a predisposition for bacterial sinusitis are immune deficiencies such as agammaglobulinemia and human HIV infection; abnormalities of polymorphonuclear cell function; structural defects, such as cleft palate; and disorders of mucociliary clearance, including cilial dysfunction and cystic fibrosis.

• Rhinosinusitis and the Common Cold.

The relationship between rhinosinusitis and the common cold has been well established. In a sentinel prospective study of 110 adults, Gwaltney et al. evaluated the findings on CT examination of patients with rhinosinusitis.

Among 31 patients who had CT scans performed within 24 to 48 hours of assessment, 24 (77%) had occlusion of the ethmoid sinus, 27 (87%), had abnormalities of one or both maxillary sinuses, 20 (65%) had abnormalities of the ethmoid sinuses, 10 (32%) had abnormalities of the frontal sinuses, and 12 (39%) had abnormalities of the sphenoid sinuses.

Rhinovirus was detected in the secretions of 7 of 17 (41%) of these patients. The patients received no medical treatment for their infections; 14 patients with sinus abnormality as seen on the initial CT scan had repeat scans, and one of these reported resolution of symptoms.

Of significance, 11 of these 14 (79%) showed clearing or marked improvement in sinus abnormalities. It is evident from this study that the common cold is associated with frequent involvement of the paranasal sinuses.

• Rhinosinusitis and Allergy.

Several studies suggest an association between rhinosinusitis and allergic sinusitis. Allergic rhinitis predisposes the patient to sinusitis since it can be associated with inflammation and obstruction of the ostia. Thus, allergic rhinitis and acute bacterial sinusitis can overlap.

• Rhinosinusitis and Asthma.

Sinusitis is often seen in patients with asthma and often exacerbates the severity of the episode. Although the pathophysiology of the association between asthma and sinusitis is not very clear.

It may be related to damage induced by the eosinophil, a prominent component of the inflammatory process that is characteristic of both diseases. A reflex phenomenon linking inflammation in the sinuses to subsequent inflammation in the lower airways has been proposed.

Sinusitis and HIV

In the pre-highly active anti-retroviral therapy (HAART) era, up to 70% of patients with HIV experienced at least one bout of acute sinusitis during the course of their disease, and 58% experienced recurrent infections.

As patients are now living longer with the availability of HAART, the prevalence of acute and chronic sinusitis in HIV-infected patents has increased. In a study of 7513 HIV-infected patients enrolled from November 1990 to November 1999, the incidence of one or more diagnoses of sinusitis was 14.5%.

The mean CD4 count at the time of sinusitis was 391. Although the authors felt the incidence of sinusitis in individuals infected with HIV is frequent, there was no association between sinusitics and an increased hazard of death after adjusting results for the level of immunodeficiency age, gender, and race.

The organisms associated with acute sinusitis in HIV patients are similar to the pathogens in other patients, with S. pneumoniae and H. influenzae being predominant. However, there is a higher occurrence of S. aureus and Pseudomonas aeruginosa in the HIV-infected patient than in the noninfected patient.

The common occurrence of P. aeruginosa in HIV-infected patients probably reflects an impaired mucociliary transport often associated with HIV infection. In addition, more unusual organisms are also commonly found, particularly if immunodeficiency progresses.

As the CD4 counts of patients dip below 200, these patients become susceptible to more opportunistic infections. Opportunistic and atypical infections include cytomegalovirus, Aspergillus spp., and Mycobacterium spp.

Nosocomial Sinusitis

Sinusitis is a relatively common infection in patients treated in an intensive care unit (ICU). An epidemiologic study in an ICU orally-intubated population found the incidence of sinusitis, as diagnosed by cultures of maxillary sinus secretion, was 10%.

In another study of 300 patients, the incidence of infectious sinusitis was estimated at 20% after eight days of mechanical ventilation in patients that were orotracheally or nasotracheally intubated.

However, in a study designed to search for nosocomial sinusitis in patients who were intubated in an ICU, Holzapfel et al. found 80 patients among 199 study patients to have infectious nosocomial maxillary sinusitis.

In this study, all patients who were nasotracheally intubated were evaluated by a sinus CT scan if body temperature was ≤38°C. When CT scan showed an air-fluid level and/or an opacification within a maxillary sinus, a transnasal puncture was performed.

Critieria for nosocomial sinusitis were sinus CT scan findings consistent with sinusitis, mechanical ventilation, macroscopic purulent sinus aspiration, and quantitative culture of the aspirated material with ≤103 cfu/mL.

Among the 80 patients, infection was due to polymicrobial flora in 44 patients and 138 organisms were isolated. The most common organisms were Eshcerichia coli, P. aeruginosa, Proteus spp., Hemophilus spp., Klebsiella spp., Enterobacter spp., S. aureus, Streptococcus spp., anaerobes, andCandida albicans.

Multiple factors can promote nosocomial sinusitis in critically ill patients. Placement of endotracheal or gastric tubes through the nose can irritate the nasopharyngeal mucosa, causing edema in the region of the ostial meatal complex.

Nasal tubes can also directly obstruct sinus drainage by acting as foreign bodies. Placing tubes via the mouth does not entirely eliminate the risk of nosocomial sinusitis, but studies suggest the risk is lessened.

In one study, the incidence of sinusitis was higher in patients intubated nasotracheally as compared to those by the oropharyngeal route.

Additional factors which may play a role in ICU patients include the supine position and limitation of head movements (which may prevent natural sinus drainage normally caused by gravity), positive-pressure ventilation, impaired ability to cough or sneeze, and the absence of airflow through the nares in ventilated patients.