Management of the patient with acute and chronic respiratory insufficiency: an overview

By Cristiano Antonino On Apr 18, 2023

Respiratory insufficiency, in its various types, is a condition that those who work in an emergency must know very well

Management of the patient with respiratory insufficiency

The management of the patient with this clinical picture is particularly complex and at risk of death.

It is therefore advisable to carefully study the causes, symptoms and consequences, in order to better intervene.

Furthermore, at the end of the article it will be possible to find many ad hoc insights.

“Respiratory insufficiency” refers to a syndrome caused by the inability of the entire respiratory system (not just the lungs as it is mistakenly thought) to perform its many functions, including the vital function of ensuring adequate gas exchange for the body ( carbon dioxide – oxygen) both at rest and under exertion.

In the patient with respiratory insufficiency, hypoxemia occurs (decrease in oxygen levels in the arterial blood) which can be associated with hypercapnia (increase in carbon dioxide values) which can potentially be fatal.

Since it is a clinical condition that appears in the course of various diseases, it is not considered a disease in its own right, but a syndrome.

Normocapnic and hypercapnic respiratory insufficiency

Depending on whether it affects only the oxygen supply or also the removal of carbon dioxide, one speaks of:

Normocapnic (or partial or hypoxemic or type I) respiratory failure: hypoxemia without hypercapnia is observed, i.e. low PaO2 levels in the presence of normal PaCO2 levels (PaO2 < 60mmHg; PaCO2 < 45mmHg).
Hypercapnic (or global, or total, or type II) respiratory failure: both hypoxemia and hypercapnia are observed, i.e. both low and high PaO2 levels (PaO2 < 60mmHg; PaCO2 > 45mmHg). In this case, especially in the severe forms and those with rapid onset, the excess of carbon dioxide present makes the blood acidic (i.e. the pH of the arterial blood drops below 7.30). In the first phase, the kidneys try to buffer and compensate for this excess of acidity, putting bicarbonates into circulation. When even this compensatory mechanism becomes insufficient, respiratory acidosis occurs, a condition that represents a medical emergency.

Both types can manifest themselves in an acute or chronic form.

There is also a third form: exacerbated chronic respiratory failure, also called “acute on chronic”, which is a frequent complication in patients with COPD.

Another possible classification is based on the fact that it occurs only with physical exercise or even at rest, on the basis of which we distinguish:

latent respiratory insufficiency: occurs under exertion but NOT at rest;
manifest respiratory insufficiency: it occurs at rest and can worsen under exertion.

Acute respiratory failure

Acute respiratory failure is the most severe form.

Severity is also related to the rapidity with which respiratory insufficiency manifests itself, as insufficiency can appear at a high rate of alteration of the values, even if the values themselves remain within the norm.

Chronic respiratory failure

Chronic respiratory failure is generally less serious than the acute form, but should not be considered non-dangerous for this reason.

It occurs more slowly (months or years), and there is a more severe form called “chronic exacerbated respiratory failure”, on the occasion of a rapid rapid increase in PaCO2 during the chronic form.

In this case the therapies are limited, as they return to the previous situation (the chronic form).

Causes of acute and chronic respiratory failure

Acute and chronic respiratory failure can typically be the result of:

acute pulmonary edema;
massive pulmonary embolism;
tension pneumothorax;
chronic obstructive pulmonary disease (COPD) which in association with the chronic or acute form increases the danger and risk of death;
respiratory distress syndrome;
bronchial asthma;
hemothorax, as a complication during treatment;
head trauma.

Environmental causes

permanence at high altitude even in healthy subjects due to O2 rarefaction;
environments with low O2 concentration.

Neurological and musculoskeletal causes

Guillan Barré syndrome;
tetanus and botulinum toxins;
barbiturate poisoning;
myasthenia gravis;
muscular dystrophies;
bulbar poliomyelitis;
tetraplegia;
kypho-scoliosis;
mobile flap.

Cardiovascular causes

severe pulmonary hypertension;
congenital heart disease;
shock;
intrapulmonary arteriovenous shunts;
pulmonary embolism;
pulmonary infarction.

Pathologies of the lung parenchyma

pulmonary edema;
pneumoconiosis;
atelectasis;
pneumothorax;
COPD;
asthma;
ARDS;
pulmonary fibrosis;
cystic fibrosis;
pneumonia.

Other causes

myxedema coma;
severe obesity (2nd or 3rd degree).

Type I respiratory failure is the most common form, it can be found in practically all pathological conditions involving the lungs.

Some of the most frequent are pulmonary edema or pneumonia.

The type II form can be found, for example, in severe forms of chronic obstructive pulmonary disease (COPD) and asthma.

Signs and symptoms of respiratory insufficiency

The forms of chronic respiratory insufficiency can be characterized by an increase in circulating red blood cells, a compensation system that the body implements in an attempt to transport as much oxygen as possible.

Patients with chronic respiratory failure also often have a heart condition known as chronic cor pulmonale, characterized by the alteration of the structure and functions of the right sections of the heart (the right ventricle has thickened and/or dilated walls) which are found to pump blood in the pulmonary circulation which, due to changes in the architecture of the lung, has high blood pressure (pulmonary hypertension).

Signs of acute respiratory failure

Clinical signs and symptoms are related to blood gas changes:

A) Symptoms related to hypoxia:

cyanosis: bluish color of the skin, due to the presence of hemoglobin not bound to oxygen (reduced hemoglobin) at concentrations greater than 5 g of /100mL;
tachypnea;
polypnea;
dyspnea (however it may be absent);
tachycardia;
increased blood pressure;
peripheral vasodilatation;
pulmonary arterial hypertension;
neurological disorders;
asthenia and muscle cramps;
coma

B) Symptoms related to hypercapnia:

acidemia: oliguria, gastrointestinal acid hypersecretion, gastric ulcers, drooling, hypersweating;
cerebral vasodilatation up to intracranial hypertension: burdening headache, vomiting, neuropsychic disorders;
sensory numbness, hypercapnic coma;
dyspnea.

C) Signs of chronic respiratory insufficiency

dyspnea;
asthenia (fatigue);
chronic encephalopathy;
chronic respiratory acidosis;
hypertension;
pulmonary hypertension;
chronic pulmonary heart;
polyglobulia.

Diagnosis of respiratory insufficiency

The level of PaO2 (partial pressure of oxygen in arterial blood) below which one speaks of respiratory insufficiency is 60 mmHg.

This limit was chosen because it is closely related to the critical point on the hemoglobin dissociation curve, below which the curve steepens and small changes in PaO2 are enough to greatly vary the oxygen content of the blood.

Similarly, by convention, the limit of 45 mmHg PaCO2 has been chosen for hypercapnia.

For the diagnosis of respiratory failure, the doctor relies on:

Clinical considerations based on history and physical examination: assessment of the patient’s state of consciousness, search for any causal comorbidities, pulmonary and cardiac objectivity.
Laboratory tests: blood gas analysis, hemoglobin saturation, arterial pH, bicarbonate concentration, hematocrit, urinary output and renal function (azotemia, creatininemia).
Diagnostic imaging: EKG, spirometry and other pulmonary function tests, echocardiogram, chest X-ray, CT scan, CT angiography, lung scintigraphy.

Treatment of respiratory insufficiency

The objectives are two:

identify and treat complications related to respiratory insufficiency that can put the patient’s life at risk;
identify and treat the underlying causes that led to the insufficiency of respiratory function.

Two of the primary duties of the doctor in the case of a patient with ARF are:

correct hypoxia (possibly by administering oxygen);
treat any respiratory acidosis that may occur.

The simple oxygen mask is used in most cases, but a better alternative may be the venturi mask.

In more acute cases, NIV (non-invasive ventilation) or mechanical ventilation may be used. useful aids can be nasal cannulas or guedel / mayo-type gold pharyngeal cannulas (to be used, however, with patients with Glasgow 3 or AVPU=U).

The percentage of oxygen to be administered to the patient is determined by the need to reach a specific oxygen saturation target, with a SaO2 between 88% and 92%; with a SaO2 between 96% and 97% in IMA and STROKE and 100% in traumatic events.

Both the means by which oxygen is administered, the FiO2 (percentage of oxygen) and the quantity of O2 expressed in litres/minute to be administered, are determined by the achievement of the saturation target to be obtained.

Treatment of chronic respiratory insufficiency

Treatment varies according to the related disease: in addition to pharmacological (antibiotics, bronchodilators) it can also include lifestyle correction (abstention from smoking or alcohol, following a balanced diet to reduce weight, etc.).

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