healthmedicinet

Setting and patients

This was a prospective observational study of patients admitted to the Intensive Care
Department of King Abdulaziz Medical City (KAMC), a tertiary-care referral center
in Riyadh, Saudi Arabia that was accredited by the Joint Commission International.
The department included a mixed medical-surgical ICU, a neuro ICU, a surgical ICU,
a trauma ICU and a stepdown unit. It was operated as a closed unit with 24-h, 7-day
onsite coverage by board-certified intensivists 11]. Patients in respiratory failure were intubated with ETTs that had the conventional
high-volume, low-pressure polyvinylchloride cuffs and different brands were used in
the different ICUs. The size of the ETT tube was usually selected based on the patient
clinical characteristics such as age and gender. In the unit, the nurse-to-patient
ratio was approximately 1:1.2. Additionally, one certified respiratory therapist covered
a maximum of six ventilated patients and took care of the patient from the respiratory
point of view which included maintenance of the airway, cuff pressure measurement
and maintenance and ventilator adjustment based on the patient requirement. The department
had an active clinical research program and had conducted and participated in multiple
international randomized-controlled trials. The study was approved by the Institutional
Review Board of the Ministry of National Guard Health Affairs and because of the nature
of the study, the consent was waived.

All consecutive adult patients (?14 years old, which the cutoff age between adults
and pediatric patients in the hospital) who were mechanically ventilated with ETT
or tracheostomy were recruited in the study until a sample size of 201 was reached.
These patients were admitted from the Emergency Department (ED) where they could have
been intubated several days earlier or from the general wards. Patients were excluded
if they were intubated with non-air cuffed ETTs or were admitted after burn injury
as burn patients may have upper airway inhalational injury.

Cuff pressure measurement and maintenance

The standard practice in KAMC ICU was to measure the cuff pressure with a handheld
Portex cuff inflator pressure gauge manometer (Smiths Medical, Dublin, OH) by the
clinical respiratory therapists (RT) every 6 h and maintain it within the recommended
range (20–30 cm H
₂
O). If the pressure was found below or above the recommended range, the clinical respiratory
therapist would adjust the pressure by inflating or deflating the cuff until target
pressure was achieved. In this study, an independent research RT performed cuff pressure
measurements by checking the cuff pressure with the same handheld manometer 2–4 h
after the standard measurements. This procedure was repeated every 12 h for up to
72 h. When the cuff pressure was not within the recommended range, the cuff pressure
was adjusted by inflating or deflating the cuff until target pressure was achieved.
The clinical RTs were not blinded due to the nature of the study and the setting.

Other collected data

The following data were additionally recorded: age, sex, height, weight, Glasgow Coma
Scale score, respiratory rate, mean arterial pressure, the ratio of the partial pressure
of arterial oxygen (PaO
₂
) to the fraction of inspired oxygen (PaO
₂
:FiO
₂
), ETT size, type and brand, whether intubation was difficult or not, duration of
intubation, ventilator mode, peak inspiratory pressure, mean airway pressure, positive
end expiratory pressure inspiratory volume, and expiratory volume at the time of measurements,
mechanical ventilation settings, and number of days of ventilation before measurements.

Statistical analysis

Data from all enrolled patients were analyzed. Statistical Analysis System software
(SAS, version 9.0; SAS Institute Cary, NC) was used to analyze the data. Continuous
data were presented as means with standard deviations and categorical data as frequencies
with percentages. The primary outcome of the study was the percentage of out-of-range
ETT cuff pressures above and below the recommended range. We divided the patients
into two groups based on their cuff pressures. Patients with low-cuff pressure, defined
as cuff pressure of??20 cm H
₂
O on two consecutive measurements, were compared with other patients (control group).
The relationship between the time between research RT and clinical RT measurements
and the corresponding difference in cuff pressures was evaluated using Pearson correlation
and multivariate linear regression analysis. In addition, multivariate analysis was
performed to identify the predictors of low cuff pressure measurements. The following
independent variables were entered for both analyses: age, gender, BMI, Glasgow Coma
Scale, history of difficult intubation, orotracheal intubation vs. tracheostomy, subglottic
suctioning, respiratory rate, PaO
₂
:FiO
₂
, tube size, inspiratory tidal volume, peak inspiratory pressure, mean airway pressure,
positive end expiratory pressure, mean airway pressure, and duration of mechanical
ventilation before the study. Results were presented as odds ratio (OR) with 95 %
confidence interval (CI). A p-value??0.05 was considered significant.