respiratory failure sevda Özdoğan md, prof. chest diseases
Post on 23-Dec-2015
219 Views
Preview:
TRANSCRIPT
RESPIRATORY FAILURE
Sevda Özdoğan MD, prof.Chest Diseases
Definition
If PaO2 <55 mmHg and/or PaCO2>45 mmHg in arterial blood gas values of a resting person who inhales room air on the sea level, the condition is called Respiratory Failure
Respiratory failure is a condition in which the respiratory system fails in its gas exchanging functions.
Normal ABG values
pH 7.35 – 7.45
PCO2 35 – 45 mmHg
PO2 80 – 100 mmHg
HCO3 22 – 26 mmol/L
BE -2 - +2
SaO2 >95%
Acidosis Alkalosis
pH < 7.35
PCO2 > 45
HCO3 < 22
pH > 7.45
PCO2 < 35
HCO3 > 26
Respiratory Acidosis
Think of CO2 as an acid
failure of the lungs to exhale adequate CO2
pH < 7.35
PCO2 > 45
CO2 + H2CO3 pH
Metabolic Acidosis
failure of kidney function
blood HCO3 which results in availability of renal tubular HCO3 for H+ excretion
pH < 7.35 HCO3 < 22
Respiratory Alkalosis
too much CO2 exhaled (hyperventilation)
PCO2, H2CO3 insufficiency = pH
pH > 7.45 PCO2 < 35
Metabolic Alkalosis
plasma bicarbonate
pH > 7.45 HCO3 > 26
Definition
If PaO2 <55 mmHg and/or PaCO2>45 mmHg in arterial blood gas values of a resting person who inhales room air on the sea level, the condition is called Respiratory Failure
Respiratory failure is a condition in which the respiratory system fails in its gas exchanging functions.
Classification
Acute Chronic
Hypoxemic Hypercapnic (Mixed)
Acute Respiratory Failure (ARF)
Characterized by acute life-treatening (reversible) derangements in ABG and acid-base status
Usually the patients do not have an underlying pulmonary disease
As the CO2 values increases rapidly respiratory acidosis occurs Kardiogenic pulmonary edema Respiratory depressing drug intoxications
Acute respiratory failure can occur in patients who already have chronic respiratory failure Eg: Acute exacerbations in advanced
COPD patients 5 mm Hg or more increase in the
stable PaCO2 value is diagnostic
Chronic Respiratory Failure (CRF)
Develops over several days or longer and may be clinically inapparent
Patients have an underlying disease Neuromusculer disease Advanced interstitial lung disease etc
Chronic hypoxemia and/or hypercapnia is irreversible with slow progression
Hypercapnia is compansated by metabolic alkalosis so pH remains in normal limits
Hypoxemic Respiratory Failure(Type I; Pulmonary Failure)
PaO2< 55 mmHg PaCO2 normal or decreased Acute and chronic forms of HRF can not
be differentiated only by ABG analysis Polystemia and corpulmonale is common
in chronic hypoxemia The initial signs of acute hypoxemia are
usually confusion and neurologic signs due to cerebral edema (impaired tissue oxygenation)
Tissue oxygenation is not only affected by PaO2 but also by cardiac output and hemoglobine concentration
Three pathophysiologic mechanisms account for the hypoxemia
Ventilation/Perfusion (V/Q) mismatch
Decreased perfusion in the areas of good ventilation (dead space ventilation)seen in
pulmonary embolism, pneumothorax asthma localised pneumonia,
Right to left shunt Perfusion of nonventilated areas of the
lung causes right to left shunt Massive pulmonary hemorragie, drowning, diffuse pneumonia, pulmonary edema (ARDS or Cardiac)
Diffusion limitation Thickening in the alveolocapillary
membrane causes diffusion abnormalities İnterstitial lung diseases
Hypercapnic Respiratory Failure(Type II; Pump failure)
PaCO2>45 mmHg and pH<7.30 in acute form (Respiratory acidosis) Eg: Drug overdose Trauma Cerebrovascular accident Infections
Chronic hypercapnia is compansated by metabolic alkalosis so pH remains within normal limits Neuromusculer diseases Thorax deformities Advanced COPD
Hypercapnic Respiratory Failure
Two pathophysiologic mechanisms account for the hypercapnia Alveolar hypoventilation
A decrease in minute ventilation without dead space ventilation cause hypercapnia (CNS, neuromusculer or chest wall diseases) PaO2 is also decreased but (PAO2-PaO2) is normal
V/Q mismatch Dead space ventilation is increased with
normal minute ventilation (airway diseases like COPD, asthma)
Hypoxemic Type I Pulmonary failure
V/Q mismatch Pneumonia, p.embolism, pneumothorax, asthma
Shunt Pneumonia, Kong.heart failure, Pulm.edema, DAH, ARDS, gastr.aspir, drowning
Diffusion limitation Fibrotic lung disease
Hypercapnic Type II Resp.pump failure
Alveolar hypoventilation CNS diseases (Drug, cerebral infarct, trauma, hypothyroidism), Neuromuscular diseases (Guillan-Barre, myastenia, MS, resp.muscle diseases),Chest wall diseases (pain, morbid obesity, Kyphoscoliosis)
V/Q mismatch COPD, Asthma, Cystic fibrosis
Types of respiratory failure and and the frequent causes
Perioperative Type III
Atelectasis Decreased FRC (supine position, obesity, upper abd incision, anesthesia)İncreased closing volume (overhydration, bronchospasm,increased secretions)
Shock Type IV
Hypoperfusion Cardiogenic (MI, Cardiac tamponade, PAH)Hypovolemic (Bleeding, dehydration)Septic (Endotoxemic, bacteriemic
Alveoloarterial oxygen gradient (PAO2-PaO2)
PAO2-PaO2=[PıO2-PaCO2/R]-PaO2
PıO2: inspired PO2R: Respiratory exchange ratio=0.8
PıO2 =(PB-PH2O)(FiO2)
(760-47)(21) = 149
PAO2-PaO2=[PıO2-PaCO2/R]-PaO2
=[149-PaCO2/0.8]-PaO2
Acute Hypoxemic Respiratory Failure:Acute Respiratory Distress Syndrome
(ARDS)
Acute severe alteration in lung structure and function due to several causes. It is characterized by acute dyspnea, severe hypoxemia, diffuse radiographic infiltrates.
It is a pulmonary edema due to increased vascular permeability
Risk Factors for ARDS
Direct insult Pulmonary contusion* Toxic gas inhalation* Neardrowning Pulmonary infection* Gastric aspiration* Pulmonary embolism Thoracic radiation Radiologic Contrast
Indirect insult Septisemia* Multisystem trauma* Hypertransfusion* Acute pancreatitis Drug overdose
(Neurogenic) DIC Cardiyopulmonary by-
pass High altitude Lung reexpansion
Insult direct/indirect
Inflamation
CellularNeutrophylMacrophage/monocytLymphocyt
HumoralComplemanCoagulation, Fibrinolysis
MediatorsCytokinesLipid mediatorsOxygen radicalesProteasesNitric oxidGrowth factorsNeuropeptides
Direct insult Pulmonary epithelium
and alveoli are subjected to the initial injury
Alveolar filling by edema, fibrin, collagen, neutrophlic aggregates and/or blood
Pulmonary consolidation
Indirect insult pulmonary
endothelial cell is subjected to the initial injury by mediators released from extrapulmonary foci
Microvessel congestion and interstitial edema
Intra-alveolar spaces are relatively spared
Pulmonary arterial pressure is increased in ARDS (>30 mmHg)
Clinical manifestation
Acute dyspnea, hypoxia, bilateral diffuse infiltration occuring most often 12-48 hours of the predisposing event (up to 5 days)
Diagnosis: Chest radiogram ABG analysis Risk factor evaluation
Hypoxia is refractory to oxygen treatment
There are no signs of left atrial hypertension (Pulmonary wedge pressure <18 mm Hg)
ALI/ARDS
Oxygenation Chest radiograph
Pulm Arterial Wedge Pressure
ALIPaO2/FIO2<=300 mmHg
Bilateral interstitial/alveolar infiltrates
<= 18 mm Hg/ no sign of left atrial hypertension
ARDSPaO2/FIO2<=200 mmHg
Bilateral interstitial/alveolar infiltrates
<= 18 mm Hg/ no sign of left atrial hypertension
Diagnostic criteria for ALI and ARDS
Differential diagnosis
Cardiac pulmonary edema
Infectious causes that cause diffuse pulmonary infiltrates and acute respiratory failure
Non infectious causes
Infectious causes of acute respiratory failure
Bacterial pneumonia
(S aureus, streptococus, legionella, salmonella, tb, mycoplasma, chlamydia)
Viral pneumonia(CMV, RSV, HSV,
VZV, adenovirus, influensa)
FungiH capsulatum,
coccidioides immitis, cryptococcus)
Parasites(PCP, Toxoplasma,
strongiloides stercoralis)
Noninfectious causes of acute respiratory failure
Cardiovascular Congestive heart failure
Drugs Aspirin Heroin Toxic gas inhalation Tricyclic antidepressants Acute radiation
Idiopathic Acute eosinophyl.pn Acute interstitial pn BOOP Idyopatic inters. Pn sarcoidosis
Immunologic Acute lupus pneumonitis Goodpasture’s sydr İdy. Hemosiderosis Hypersensitivity pn Pulmonary vasculitis with
hemorragia Metabolic
Alveolar proteinosis Neoplastic
Lymphangitic carsinomatosis
Leukemic infiltration Lymhoma
Miscellaneous Fat, amnion embolism High altitude edema
Treatment
Treatment of the predisposing factor
Cardiovascular supportive care Mechanic ventilation Fluid management
Pharmacological treatment
Cardiogenic Pulmonary Edema
Radiology of cardiac edema with central alveolar consolidation (bat wing pattern)
Increased cardiothoracic index Increased pulmonary wedge
pressure (>18 mm Hg)
Radiology of non cardiac pulmonary edema with the differences of cardiac edema
Cardiogenic pulmonary edema
Radiology of a casulty of 1999 Izmit earthquake (ARDS)
15.July
16.July
17.July
22.July
ARDS due to Gr(-) sepsis
21.May
23. May
26. May
21. May
29 .May
ARDS occured 24 hours after a traffic accident. Resolution due to MV on May 26 but progression on May 29
Pulmonary edema
Positional redistribution of the densities due to gravity
Ground grass appearance and pneumotocel formation on CT
Prognosis of respiratory failure
Morbidity and mortality depends on degree of respiratory failure and the underlying disease
Mortality is higher in old age with acute hypercapnic respiratory failure
In COPD patients with acute respiratory failure mortality is 10-20%
In ARDS patients mortality is around 50%
top related