# 01 - SECTION 1 Respiratory Critical Care

## SECTION 1 Respiratory Critical Care

Section 1	 Respiratory Critical Care
Rebecca M. Baron, Anthony F. Massaro

Approach to the Patient 

with Critical Illness
The care of critically ill patients requires a thorough understand­
ing of pathophysiology and centers initially on the resuscitation of 
patients at the extremes of physiologic deterioration. This resuscita­
tion is often fast-paced and occurs early when a detailed awareness 
of the patient’s chronic medical problems may not yet be possible. 
While physiologic stabilization is taking place, intensivists attempt to 
gather important background medical information to supplement the 
real-time assessment of the patient’s current physiologic condition. 
Numerous tools are available to assist intensivists in the assessment 
of pathophysiology and management of incipient organ failure, offer­
ing a window of opportunity for diagnosing and treating underlying 
disease(s) in a stabilized patient. However, despite these tools, ongo­
ing clinical bedside assessment is imperative for care of the critically 
ill patient. Indeed, the use of interventions to support the patient, 
such as mechanical ventilation and renal replacement therapy, is 
commonplace in the intensive care unit (ICU). An appreciation of 
the risks and benefits of such aggressive and often invasive interven­
tions is vital to ensure an optimal outcome. Nonetheless, intensivists 
must recognize when a patient’s chances for recovery are remote or 
nonexistent and must counsel and comfort dying patients and their 
significant others if an initial trial of invasive supportive care is either 
not effective or is not appropriate for the patient’s current condition. 
Critical care physicians often must redirect the goals of care from 
resuscitation and cure to comfort when the resolution of an underly­
ing illness is not possible. The COVID-19 pandemic has heightened 
the need and priority for effective critical care practices (Chap. 205), 
as well as the need for additional support for post-ICU care and 
recovery for ICU survivors
TABLE 311-1  Calculation of SOFA Scorea
SYSTEM

Respiration
 
 
 
 
 
  Pao2/FIo2, mmHg (kPa)
≥400 (53.3)
<400 (53.3)
<300 (40)
<200 (26.7) with respiratory 
support
Coagulation
 
 
 
 
 
  Platelets, × 103/μL
≥150
<150
<100
<50
<20
Liver
 
 
 
 
 
  Bilirubin, mg/dL (μmol/L)
<1.2 (20)
1.2–1.9 (20–32)
2.0–5.9 (33–101)
6.0–11.9 (102–204)
>12.0 (204)
Cardiovascular
MAP ≥70 mmHg
MAP <70 mmHg
Dopamine <5 or 

dobutamine (any dose)b
Dopamine 5.1–15 or 

epinephrine ≤0.1 or 
norepinephrine ≤0.1b
Central nervous system
 
 
 
 
 
  Glasgow Coma Scalec

13–14
10–12
6–9
<6
Renal
 
 
 
 
 
  Creatinine, mg/dL (μmol/L) 

<1.2 (110)
1.2–1.9 (110–170)
2.0–3.4 (171–299)
3.5–4.9 (300–440)
or
<500
or urine output, mL/d
aAdapted from JL Vincent et al: Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. The SOFA (Sepsis-related Organ Failure 
Assessment) score to describe organ dysfunction/failure. Intensive Care Med 22(7):707, 1996. bCatecholamine doses are given as μg/kg per min for at least 1 h. cGlasgow 
Coma Scale scores range from 3 to 15; higher score indicates better neurological function.
Abbreviations: FIo2, fraction of inspired oxygen; MAP, mean arterial pressure; Pao2, partial pressure of oxygen.

Critical Care Medicine
PART 8
ASSESSMENT OF ILLNESS SEVERITY
In the ICU, illnesses are frequently categorized by degree of severity. 
Numerous severity-of-illness (SOI) scoring systems have been devel­
oped and validated over the past three decades. Although these scoring 
systems have been validated as tools to assess populations of critically 
ill patients, their utility in predicting individual patient outcomes at 
the bedside is not clear. Their utility may be more applicable toward 
defining patient populations for clinical trial outcomes and broader 
epidemiologic studies. SOI scores are also useful in guiding hospital 
administrative policies, directing the allocation of resources such as 
nursing and ancillary care, and assisting in assessments of quality of 
ICU care over time. Scoring system validations are based on the prem­
ise that age, chronic medical illnesses, and derangements from normal 
physiology are associated with increased mortality rates. All existing 
SOI scoring systems are derived from patients who have already been 
admitted to the ICU. Nevertheless, there has been increased recent 
clinical use of scoring systems due to revised consensus guidelines for 
definitions of sepsis, as will be detailed below.
The most commonly utilized scoring systems are the SOFA (Sequen­
tial Organ Failure Assessment) and the APACHE (Acute Physiology 
and Chronic Health Evaluation). There has been more recent interest 
in the use of a “quick” SOFA, or qSOFA, scoring system for prognosti­
cation of sepsis outcomes.
■
■THE SOFA SCORING SYSTEM
The SOFA scoring system is composed of scores from six organ 
systems, graded from 0 to 4 according to the degree of dysfunction 
(Table 311-1). The score accounts for clinical interventions; it can be 
measured repeatedly (i.e., each day), and rising scores correlate with 
increasing mortality. The most recent sepsis consensus conference 
guidelines incorporated an increase of at least two points in the SOFA 
score from baseline as diagnostic of sepsis in the setting of suspected 
or documented infection. Patients with suspected infection can be 
predicted to have poor outcomes typical of sepsis if they have at least 
two of the following clinical criteria: respiratory rate ≥22 breaths/min, 
altered mental status, or systolic blood pressure ≤100 mmHg. Recently, 
a new bedside clinical score using two or more of the above clinical 
criteria has emerged and is termed quick SOFA (qSOFA). qSOFA is 
intended to screen patients for risk of poor outcomes from sepsis from 
SCORE
<100 (13.3) with 
respiratory support
Dopamine >15 or 
epinephrine >0.1 or 
norepinephrine >0.1b
>5.0 (440)
or
<200