Pilbeams Ch 3

Question 1

Equation of motion

Answer 1

Pmus + Pvent= V/C+(Raw×flow)

Question 2

The primary variable that the ventilator adjust to produce inspiration is the control variable

Answer 2

The most commonly used control variables are pressure and volume

Question 3

Pressure controller

Answer 3

The ventilator maintains the same pressure waveform at the mouth regardless of changes in lung characteristics

Question 4

Volume controller

Answer 4

Ventilator volume delivery and volume waveform remain constant and are not affected by changes in lung characteristics. Volume is measured

Question 5

Flow controller

Answer 5

Ventilator volume delivery and flow waveform remain constant and are not affected by changes in lung characteristics. Flow is measured

Question 6

Time controller

Answer 6

Pressure, volume, and flow curves can change as lung characteristics change. Time remains constant

Question 7

Phase variables

Answer 7

A phase variable begins, sustains, and, and determines the characteristics of the excretory portion of each breath. 4 phase variables are typically described:

1. The trigger variable begins inspiration
2. The limit variable limits the pressure, volume, flow, or time during inspiration but it does not end the breath
3. The cycle variable ends inspiratory phase and begins exhalation
4. The Baseline variable is the end expiratory Baseline (usually pressure) before a breath is triggered

Question 8

Ventilator determination of actual breath delivery during assisted ventilation

Answer 8

If a patient occasionally starts a breath independently, the ventilator must determine how long to wait before another breath is needed. An example, the rate is set for 6 breaths/minute. The ventilator determines that it has 10 seconds for each breath. If the patient triggers a breath, the ventilator “resets” itself so that it still allows a full 10 seconds (60 s/6 breats) after the start of the patients last breath before it time triggers another breath.