Effects of Mechanical Ventilation onPATIENT BODY

1. Presented By :-
1) HAIFAA
Effects of Mechanical Ventilation on
PATIENT BODY

2. OUTLINE
 OBJECTIVES
 INTRODUCTION
 Mechanical ventilation
 Modes of Ventilation
 Indications for mechanical ventilation
 GOALS OF MECHANICAL VENTILATION
 Effects of Mechanical Ventilation on RESPIRATORY SYSTEM
 Effects of Mechanical Ventilation on Cardiovascular system
 Effects of Mechanical Ventilation on RENAL SYSTEM
 Effects of Mechanical Ventilation on CNS
 Effects of Mechanical Ventilation on GASTROINTESTINAL
 Effects of Mechanical Ventilation on Large Bowel
 Effects of Mechanical Ventilation on Liver and Gallbladder
 Effects of Mechanical Ventilation on SLEEP
 OTHER Effects of Mechanical Ventilation
 MONITORING
 summary

3. OBJECTIVES
 What is the Mechanical Ventilation
 What are Mechanical Ventilation modes
 What are the Indications for mechanical
ventilation
 Identify the GOALS OF MECHANICAL
VENTILATION
 Identify the Effects of Mechanical Ventilation
on patient body

4. INTRODUCTION
 Human heart is functionally divided into right and
left side. Each side may be further subdivided into
a ventricle and an atrium.
 The primary function of each atrium is to act as a
reserviour and booster pump for venous return to
the heart.
 And , the primary physiological function of each
ventricle is to maintain circulation of blood to the
organs of the body .

5. Mechanical ventilation
Mechanical ventilation, in the
healthcare setting or home, helps
patients breathe by assisting the
inhalation of oxygen into the lungs
and the exhalation of carbon dioxide.
Depending on the patient’s condition,
mechanical ventilation can help
support or completely control
breathing

6. Modes of Ventilation
 Assist/control (A/C)
 Continuous positive airway pressure
ventilation (CPAP)
 Synchronized intermittent mandatory
ventilation (SIMV)
 Pressure control ventilation (PCV or PC)
 Positive end expiratory pressure (PEEP)
 Pressure support ventilation (PSV or PS)

7. Indications for mechanical
ventilation
 Ventilatory failure
 Oxygenation failure
 Excessive ventilatory workload
 Impending respiratory failure

8. VENTILATORY FAILURE
 Drug overdose
 Spinal cord injury
 Head injury & stroke
 Neuromuscular dysfunction
 Sleep disorders
 Acute airflow obstruction
 Chest trauma
 Postoperative – thoracic & upper abdominal
 Electrolyte imbalance
 General anaesthesia

9. OXYGENATION FAILURE
&INCREASED VENTILATORY
WORKLOAD
 Acute lung injury/ARDS
 Acute severe airflow obstruction
 Dead space ventilation
 Shunts
 Congenital heart diseases
 Shock
 High metabolic rate & Obesity
 General anaesthesia & Postop

10. GOALS OF MECHANICAL
VENTILATION
 Maintain patient comfort
 Allow a normal, spontaneous breathing pattern
whenever possible
 Maintain a PaCO₂ between 35 - 45 mmHg
 Maintain a PaO₂ sufficient to meet cellular O₂
demands but avoid oxygen toxicity
 Avoid acid-base and electrolyte imbalances
 Avoid respiratory muscle fatigue and atrophy

11. Effects of Mechanical Ventilation on
RESPIRATORY SYSTEM
Respiratory system
 decreased lung compliance
 more uneven distribution of ventilation
 increase in dead space and in ratio of dead space to
tidal volume
Patients with normal lungs
 fall in FRC and increased alveolar to arterial oxygen
gradient
 due to extensive dependent atelectasis
Patients with abnormal lungs
 in patients who have been hypoventilating near
residual volume, mechanical ventilation will increase
FRC and tidal volume

12. Effects of Mechanical Ventilation on
Cardiovascular system
 Positive pressure ventilation results in:
 rise in pleural pressure
 rise in intra-abdominal pressure
 increased lung volumes
The extent of these changes relative to any given level
of airway pressure will depend on the lung and chest
wall compliance and airway resistance
In any individual patient the overall effects will depend
on the patient's underlying pathophysiology.

13. Effects of Mechanical Ventilation on
Cardiovascular system
Preload
 LV preload is usually
(but not invariably) reduced by a variety
of mechanisms
 Venous return
 in a volume resuscitated patient
venous return does not fall
intrathoracic pressure is positive rather than negative
but
intra-abdominal pressure also rises
pressure gradient between abdomen and thorax is
maintained
 in a patient with an open abdomen
 venous return should fall
 intra-abdominal pressure does not rise
 pressure gradient not maintained

14. Effects of Mechanical Ventilation on
Cardiovascular system
 changes in LVEDV do not necessarily parallel
changes in RVEDVRV and LV confined by
pericardium
 as a result increase in RVEDV decreases LV
compliance and vice versa
 in a patient with pulmonary hypertension a reduction
in venous return as a result of positive pressure
ventilation will reduce the size of a dilated RV and
hence increase LV compliance and LV preload

15. Effects of Mechanical Ventilation on
Cardiovascular system
Pulmonary vascular resistance
 decreased RV stroke volume and hence LV preload because of compression
of pulmonary vessels by positive alveolar pressure
LV compliance
 at high lung volumes lungs compress the heart reducing LV compliance and
hence LV end-diastolic volume
Afterload
 afterload = wall tension (T) during contraction
where Ptm= transmural pressure, R=radius and H=wall thickness
 transmural pressure=intraventricular pressure-pleural pressure
 pleural pressure increased by positive pressure
 therefore transmural pressure and afterload must be decreased by positive
pressure ventilation

16. Effects of Mechanical Ventilation on
Cardiovascular system
Myocardial oxygen consumption
 myocardial oxygen consumption was previously thought to be
determined by stroke work. However it is now known that it is
determined by the sum of stroke work and elastance-defined potential
work. The latter is the potential energy in the ventricle at end-systole.
Figure below illustrates this relationship. Myocardial oxygen
consumption is proportional to the shaded area. As mechanical
ventilation generally decreases preload and afterload it shifts the
pressure-volume loop to the left and down decreasing elastance-defined
potential work and thus myocardial oxygen consumption.
 in patients with coronary artery disease reducing myocardial oxygen
consumption may improve the balance between oxygen demand and
supply resulting in an improvement in LV function. Thus in these
patients mechanical ventilation may increase LV contractility.

17. Effects of Mechanical Ventilation on
Cardiovascular system
Cardiac output
 overall effect depends on whether ventricle is
normal or abnormal
 in a patient with normal LV contractility increased
intrathoracic pressure decreases LVEDV more
than LVESV resulting in a fall in stroke volume
 in a patient with decreased LV contractility, �
intrathoracic pressure decreases LVEDV less
than LVESV resulting in a rise in stroke volume
(figure below). Note the decreased slope of the
end systolic pressure volume relationship due to
decreased contractility

18. Effects of Mechanical Ventilation on
RENAL SYSTEM
 Not all studies have shown a decrease in renal
blood flow with positive pressure ventilation.
Those patients who are volume depleted are
more susceptible to reduced cardiac output.
 renal blood flow falls if cardiac output falls
 Decreased sodium secretion due to fall in cardiac
output and decreased secretion of atrial
natriuretic factor
 Increased water retention due to increased
secretion of ADH, particularly in children.

19. Effects of Mechanical Ventilation on
RENAL SYSTEM
 The usual renal response to reduction of cardiac
output and mean arterial pressure.
 Reduction in urine output secondary to a fall in the
transmural pressure of the right atrium that results in
reduction of the secretion of atrial naturitic peptide
and the activation of renin-angiotensin-aldosterone
system and pituitary vasopressin secretion

20. Effects of Mechanical Ventilation on
CNS
 increased intrathoracic pressure decreases
venous drainage from head and may increase
ICP. If, however, mechanical ventilation results in
a decrease in PaCO2 ICP may actually fall
 NB adverse effects of mechanical ventilation are
far outweighed by benefits in brain injured
patients

21. Effects of Mechanical Ventilation on
GASTROINTESTINAL
Esophagus,Stomach and Small Intestine
 Erosive esophagitis (30-50% of patients
ventilated >48 hours)
 NG tube
 Poor lower esophageal sphincter tone and reflux
 Opiates and adrenergic agonists
 Duodenogastroesophageal reflux through the action of
trypsin
 Upper gastrointestinal hemorrhage:
 Stress
 Decreased gastric mucosal protection secondary to a fall
in splanchnic blood flow
 Decreased motility of stomach and small intestine

22. Effects of Mechanical Ventilation on
Large Bowel
 Constipation
 Abdominal distension

23. Effects of Mechanical Ventilation on
Liver and Gallbladder
 Reduction in portal venous flow secondary to the
fall in cardiac output.
 Hepatic engorgement.
 Reduction in drug clearance secondary to
reduction of hepatic blood flow.

24. Effects of Mechanical Ventilation on SLEEP
DISRUPT SLEEP
 Noise disruption
 Ventilator alarm:
 inappropriate threshold
 Delayed alarm inactivation
 Humidifier alarms
 Disruption by nursing interventions
o Airway suction
o Nebulizer delivery
 Ventilation-related pharmacological disruption
o Benzodiazepines
o Oipoids

25. OTHER Effects of Mechanical
Ventilation
 DECUBITUS ULCERS
 MALNUTRITION
 DEPRESSHION & ANXIETY
 DELEIRIUM

27. MONITORING
 Physical examination for all body systems
focusing on the resp system
 Assess the patient for decreased cardiac output
 Administer a sedative as ordered to relax the
patient
 Evaluate the settings of mechanical ventilator
 Ensure patient safety

28. summary
EFFECTS OF MECHANICAL
VENTILATION
 Decrease in venous return
 Decrease in cardiac output
 Decrease in pulmonary capillary blood flow
 Increase in pulmonary vascular resistance
 Increase in central venous pressure
 Increased intracerebral venous pressure
 Decreased CSF absorption
 Increased intraabdominal pressure
 Increased vasopressin secretion

29. summary
EFFECTS OF MECHANICAL
VENTILATION
 Decreased GFR & urine output
 Increased fluid retention
 Paradoxical fall in PaO₂
 Barotrauma/volutrauma
 Ventilator-associated pneumonia
 Oxygen toxicity
 Prolonged intubation – airway problems
 Pressure sores
 Ventilator dependence

30. Question ?